&EPA
United States
Environmental Protection
Agency
Municipal Environmental Research EPA 600 2-79-128
Laboratory August 1979
Cincinnati OH 45268
Research and Development
Adapting Woody
Species and Planting
Techniques to
Landfill Conditions
Field and Laboratory
Investigations
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development. U S Environmental
Protection Agency have been grouped into nine series Those nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are'
1 Environmental Health Effects Research
2. Environmental Protection Technology
3 Ecological Research
4. Environmental Monitoring
5 Socioeconomic Environmental Studies
6 Scientific and Technical Assessment Reports (STAR)
7 Interagency Energy-Environment Research and Development
8. "Special" Reports
9 Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH
NOLOGY series This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards
This document is available to the public through the National lechmoal Informa-
tion Service, Springfield, Virginia 22161
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EPA-600/2-79-128
August 1979
ADAPTING WOODY SPECIES AND
PLANTING TECHNIQUES TO LANDFILL CONDITIONS
Field and Laboratory Investigations
Ida A. Leone, Franklin B. Flower
Edward F. Oilman, and John J. Arthur
Cook College, Rutgers University
New Brunswick, New Jersey 08903
Grant No. R 803762-02-3
Project Officer
Robert E. Landreth
Solid and Hazardous Waste Research Division
Municipal Environmental Research Laboratory
Cincinnati, Ohio 1*5268
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 1*5268
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DISCLAIMER
Laboratory, U.S. Enviromental^r^13^^6 MuniciPal Environmental Research
Approval does not signify that th* ^°n Afiency and approved for publication.
and policies of the uVs. Environ^ t°f ^ neces^rily reflect the views
of trade names or coBme^STSSSt p™tection Agency, nor does mention
for use- Products constitute endorsement or recommendation
ii
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FOREWORD
The Environmental Protection Agency (EPA) was created because of
increasing public and government concern about the dangers of pollution to
the health and welfare of the American people. Noxious air, foul water and
spoiled land are tragic testimony to the deterioration of our natural environ-
ment. The complexity of that environment and the interplay between its com-
ponents require a concentrated and integrated attack on the problem.
Research and development is that necessary first step in problem
solution and it involves defining the problem, measuring its impact, and
searching for solutions. The Municipal Environmental Research Laboratory
develops new and improved technology and systems for the prevention, treat-
ment and management of wastewater and solid and hazardous waste pollution
discharges from municipal and community sources, for the preservation and
treatment of public drinking water supplies and to minimize the adverse
economic, social, health, and aesthetic effects of pollution. This publica-
tion is one of the products of that research, a most vital communication's
link between the researcher and the user community.
The ultimate use of refuse landfills involves the planting of vegetation.
The problems of growing deep-rooted vegetation over former landfills has
been studied through literature surveys, and greenhouse and field experiments.
It was the purpose of these studies to gain an insight into the role of
anaerobically produced gases (mainly methane and carbon dioxide) in curtail-
ing the growth of plants on landfills. Methods of attenuating the detri-
mental effects of landfill gases were also evaluated.
Francis T. Mayo, Director
Municipal Environmental Research
Laboratory
iii
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ABSTRACT
During the past dozen years, many attempts to revegetate completed
sanitary landfills have been undertaken throughout the United States, with
variable degrees of success. This has been evaluated in a recent nationwide
field survey of vegetation growth on completed sanitary landfills. Based on
the results of this survey, literature reviews and other field experiences,
a study was undertaken to determine which species, if any, can maintain
themselves in a landfill environment; to investigate the feasibility of
preventing landfill gas from penetrating the root zone of selected species
by using gas-barrier techniques; and to identify the (those) factor(s) which
are most important in maintaining adequate plant growth on completed sanitary
landfills. Ten replicates of nineteen woody species were planted on a ten-
year old completed sanitary landfill and five gas-barrier systems were
constructed. The experiment was completely replicated on old forest land to
act as a control. Of the nineteen species planted on the landfill for the
past two years, certain species have tolerated the landfill conditions better
than others. Black gum jproved most tolerant and honey locust least tolerant
to anaerobic landfill^conditions.OftheTfive gas-barrier systems tested,
plastic sheeting underlain by gravel and vent-ed by means of vertical PVC
pipes, a three foot mound underlain with one foot of clay, and a three foot
mound with no clay barrier proved effective in preventing penetration of gas
into the root systems of the test species.
Carbon dioxide and methane are the major components of sanitary refuse
landfill-generated gas which has been associated with the demise of vegeta-
tion on and adjacent to completed landfills. An investigation of the effects
of carbon dioxide (CQ^} and/or methane (CH1+) contaminated soil atmospheres on
the growth of tomato plants indicated that C02 per se was toxic to tomato
roots in a low 02 soil atmosphere, whereas CHlj. per se was innocuous under the
same conditions. No interaction was observed between COg and CH^ in terms of
damage to tomato roots. Investigations' into the effects of C0?- and CHi«-
contaminated soil indicated that red maple (Acer rubrum) is more tolerant to
the presence of these gases than is sugar maple (Acer saccharum). With
respect to gas concentration, 50$ CH^ alone in the~~root zone resulted in no
visible symptoms whereas 20ffl C02 was found to cause adventitious root
formation and visible decline in tomato shoots.
This report was submitted in fulfillment of Contract No. R 803762-02-3
by Rutgers University under the. sponsorship of the United States Environ-
mental Protection Agency. This report covers the period January 1, 1976 to
September lU, 1978, and the work was completed as of October 15, 1978.
iv
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CONTENTS
Foreword ill
Abstract iv
Figures vi
Tables viii
Acknowledgements xii
1 Introduction 1
2 Conclusions 2
3 Recommendations h
h Literature Review 5
5 Experimental Procedures 19
6 Results 66
7 Discussion 101
8 References Ill
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FIGURES
Number Page
1 Location of landfill vegetation growth experiment, East
Brunswick, New Jersey 20
2 Species distribution on landfill and successional stages on
adj ourning woodlot 22
3 Edgeboro Sanitary Landfill, East Brunswick, New Jersey,
location of reference stations for gas and vegetation
sampling points 29
k Gas and vegetation sampling points on Edgeboro Sanitary
Landfill 30
5 Plastic soil gas sampler 31
6 Location of trees on species screening area and gas-barrier
techniques on experimental plot 33
7 Location of trees on species screening area and gas-barrier
techniques on control plot 3^
8 Design of gravel/plastic/vents trench ........................ 35
9 Design of clay/ vents trench .................................. 37
10 Design of clay /no vents trench ............................... 38
11 Design of no clay-barrier mound .............................. 39
12 Design of clay barrier mound ................................. ho
13 Location of soil variable sampling stations on experimental
landf in plot ............................................. U9
lU Location of soil variable sampling stations on control plot . . 50
15 Hammer and auger used for collecting soil bulk density sample. 52
16 Modified galvanized steel trash can used to fumigate maple
seedlings ................................................. 58
vi
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Number Page
17 Design of red and sugar maple fumigation experiment 59
18 Culture vessel for tomato plant fumigations 62
19 Lids for culture vessels 63
20 Soil moisture content of experimental and control plots 77
21 Mean percent 0 at 7" depth in fumigated trash cans 89
22 Mean percent CO at 7" depth in fumigated trash cans 90
23 Mean percent N at 7" depth in fumigated trash cans 91
2U Mean percent CH^ at 7" depth in fumigated trash cans 92
25 Percent oxygen in culture vessels in tomato treatments A and D
(Experiment U) 99
vii
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TABLES
Number Page
1 Tree Distribution and Density- Edgeboro Landfill and Island ... 25
2 Description of Permanent Stations on the Completed Sanitary
Landfill .................................................. 27
3 Tree Planting Selection Criteria ............................. U2
U Species Selected for Vegetation Growth Experiment at Edgeboro
Landfill .................................................. 1*3
5a Plant Key for Edgeboro Landfill Tree Growing Experiment for
the Control Plot
5b Plant Key for Edgeboro Landfill Tree Growing Experiment for
the Experimental Plot ..................................... 1*5
6 Tree and Shrub Planting Data ................................. U6
7 Distance From the Soil Surface at Which Stem Increment was
Measured .................................................. 5^
8 Composition of Atmospheres Used to Fumigate Tomato Plants in
Experiment 1 .............................................. 6U
9 Composition of Atmospheres Used to Fumigate Tomato Plants in
Experiment 2 ............... '. .............................. 6U
10 Composition of Atmospheres Used to Fumigate Tomato Plants in
Experiment 3 .............................................. 65
11 Composition of Atmospheres Used to Fumigate Tomato Plants in
Experiment h .............................................. 65
12 Percent Frequency of C02 Readings* of Soil Atmospheres on
Twenty Completed Sanitary Landfills ....................... 66
13 Percent Frequency of 02 Readings* of Soil Atmospheres on
Twenty Completed Sanitary Landfills ....................... 67
viii
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Number Page
lU Percent Frequency of Combustible Gas Readings* of the
Atmospheres on Twenty Completed Sanitary Landfills ....... 67
15 Mean Percent COp, 02 and Combustible Gas at 1-Foot Depth
With Age of Sanitary Landfill ............................. 67
16 Mean Percent Og, C02 and Combustible Gas at 1-Foot Depth
With Depth of Refuse in the Sanitary Landfill ............. 68
17 Percent Combustible Gas From 1-Foot Deep Test Holes on
Completed Edgeboro Landfill ............................... 68
18 Percent 02* From 1-Foot Deep Test Holes on Completed
Edgeboro Landfill ......................................... 69
19 Percent C02* From 1-Foot Deep Test Holes on Completed
Edgeboro Landfill ......................................... 70
20 Gas Chromatographic Analysis of Composition of the Soil
Atmosphere at Depth of 10- Inches at Six Stations on
Completed Edgeboro Landfill, July lU , 1977 ................ 70
21 Gas Chromatographic Analysis of Composition of Soil Atmosphere
at Depth of 10- Inches at Six Stations on Completed Edgeboro
Landfill , October 13 , 1977 ................................ 70
22 Depth of Soil Cover* at Stations on Edgeboro Landfill and
Growth Status o'f Vegetation ............................... 71
23 Number of Tree Deaths in Screening Experiment Between
1976 and 1977 ............................................. 72
2k Mean Values for the Five Tree Variables for Each Species on
the Experimental and Control Plots ........................ 73
25 Relative Tolerance of Species to Landfill Conditions ......... 7U
26 Mean Values for Soil Variables on Experimental and Control
Plots in 1977 ............................................. 75
27 Mean Values for Nitrate and Ammonium Nitrogen on Experimental
and Control Plots ......................................... 76
28 Coefficients of Variation for Soil Variables on Experimental
and Control Plots ......................................... 78
8.
29 Depth of Root Penetration on Experimental and Control Plots . . 79
30 Observation of Dead Trees on Experimental and Control
Gas-Barrier Techniques .................................... 80
ix
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Number Page
31 Mean Values for Dependant Tree Variables for Each Gas-Barrier
Technique on Experimental Area 8l
32 Variance Components for American Basswood and Japanese Yev
for Three Tree Variables 82
33 Nitrate Nitrogen, Ammonium Nitrogen and Manganese Contents of
Soil in the Barrier Techniques 83
3^ Mean Soil Variable Levels in the Gas-Barrier Techniques 8U
35 Number of Maple Seedlings* Exhibiting Various Growth
Conditions at Termination of Experiment 86
36 Mean Stomatal Resistance (SEC/CM)* of Red and Sugar Maple
Seedlings in Various Treatments 87
37 Stomatal Resistance* of Maple Seedlings for Treatments 1 and
3 Recorded as Percent of Control 87
38 Mean Percent Composition* of the Culture Vessel Atmospheres
in Experiment 1 88
39 Total Increase in Height, Foliar Dry Weight, and Total Nitrogen
Content of the Leaves of the Tomato Plants* at the
Termination of Experiment 1 93
hO Mean Percent Composition* of the Culture Vessel Atmospheres
in Experiment 2 (8-Day Fumigation) 93
hi Mean Percent Composition* of the Culture Vessel Atmospheres
in Experiment 2 (12-Day Fumigation) 9^
k2 Total Increase in Height, Foliar Dry Weight, and Total
Nitrogen Content of the Leaves of Tomato Plants* After
8-Days of Fumigation in Experiment 2 95
1*3 Total Increase in Height, Foliar Dry Weight, and Total
Nitrogen Content of the Leaves of Tomato Plants After
12-Days of Fumigation in Experiment 2 95
kk Mean Percent Composition* of the Culture Vessel Atmospheres
in Experiment 3 96
U5 Total Increase in Height, Foliar Dry Weight and Adventitious
Root Development of Tomato Plants at the Termination of
Experiment 3 96
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Number Page
k6 Mean Percent Composition* of the Culture Vessel Atmospheres
in Experiment k 97
kl Total Foliar Nitrogen and Dry Weight and Increase in Height
and Adventitious Root Development of Tomato Plants* at
the Termination of Experiment U 98
xi
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ACKNOWLEDGEMENTS
The cooperation of the New Jersey Cooperative Extension Service
personnel, particularly Dr. Spencer H. Davis, Jr., Specialist in Plant
Pathology, Dr. Roy Flannery, Specialist in Soils, and Professor Lawrence D.
Little, Jr., Associate Specialist in Nursery Management, is greatfully
acknowledged. The authors would also like to acknowledge the assistance of
the following Cook College students: Deborah Flower, Christopher Proulx, and
Michael Telson. In addition, we wish to acknowledge Mary Ann Fischer for her
timeless efforts in reviewing and typing this manuscript.
xii
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SECTION 1
INTRODUCTION
The pressures of population expansion and urbanization have prompted
a reappraisal of anticipated uses for completed landfill sites. Conversion
to recreational areas or other non-structural usage has been considered an
acceptable end for completed landfill sites in urban areas; and in rural
areas intensifying land use has resulted in attempts to use completed
landfills for growing commercial crops. Numerous farmers, as well as scores
of landscapers, have encountered mixed success in trying to establish
agricultural crops, trees, and shrubs on landfills throughout the country
Three questions are often raised: "What species will thrive on completed
landfill sites?", "Are there any techniques available which will help in
attempting to establish a vegetative cover over a completed landfill area?",
and "What is the nature of the toxic effect of landfill gas on vegetation?"
Reports from a nationwide mail survey funded by the Federal E.P.A.
Solid and Hazardous Waste Division determined that the scope of problems
encountered when vegetating completed landfills was indeed of national
latitude. It was ascertained, from on-site visits to some 60 vegetated
landfills, that answers to the previously raised questions would benefit
not only the landscaper or farmer trying to vegetate a former landfill, but
the general public as well in that they too would ultimately derive value
from successful vegetation projects such as parks, golf courses and
recreational areas.
In order to investigate the possibility of successfully growing vegeta-
tion on such areas, two experiments were designed: (l) a field experiment
with three objectives: (a) to determine the relative tolerance of a number
of commonly grown tree and shrub species to the soil environment created on
and adjacent to a sanitary refuse landfill; (b) to determine if barriers to
the migration of decompositional gases can function in preventing gas con-
tamination of the root systems of selected sensitive species; (c) to identify
those soil factors which are most responsible for causing vegetation growth
problems on completed landfills. (2) A greenhouse experiment to assess the
effects on vegetation of soil contamination by simulated landfill gas
and CHr) mixtures.
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SECTION 2
CONCLUSIONS
1. Black gum, Norway spruce, and ginkgo were the three species most toler-
ant to conditions of the Edgeboro experimental landfill.
2. Honey locust, hybrid poplar, and weeping willow made the poorest growth
of all surviving species on the landfill plot and appeared to be least
adapted to landfill conditions.
3. Soil carbon dioxide, oxygen, moisture content, bulk density and
temperature were important soil factors controlling the growth of
American basswood on the experimental plot on the Edgeboro sanitary
landfill.
h. Soil mounds, either with or without an underlying clay gas-barrier
functioned successfully in preventing the migration of landfill gases
into the root zone of trees. A U-foot deep trench with a 1-foot layer
of road gravel overlain with polyethylene sheeting and vented with
perforated vertical vent pipes also functioned to keep out the gases
of anaerobic decomposition.
5. Woody plants appeared able to better survive on a completed sanitary
landfill if planted when small in height i.e. less than three feet.
Daring this study, this factor appeared to be more important than the
biological ability of a plant to withstand low oxygen environments.
6. Severe gas contamination of the original soil cover on the Edgeboro
sanitary landfill was observed in isolated areas which could be located
by the poor growth of vegetation associated with these areas. These
soil gas conditions remained consistent for the fifteen month study
period. The poor growth of vegetation in areas of landfill gas contami-
nation was believed to be responsible for excessive erosion on the site.
7. Red maple (Acer rubrum), which is flood tolerant, was found to be more
tolerant also of soil contaminated by simulated landfill gas than
sugar maple (Acer saccharum) which is not tolerant of flooding.
8. Tomato plants growing in sand-solution greenhouse cultures were severely
damaged by exposure to carbon dioxide concentrations of 17$ or greater
in the root zone. This response was not influenced by the presence or
absence of high concentrations of methane or fluctuations in the 09
concentrations, provided the 0_ in the root zone was not less than 2$.
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9. Excessive concentrations of methane in the root zone of such tomato
plants resulted in the depletion of oxygen, and the consequent decline
of the plants after eight days' exposure.
10. Tomato plants exposed to excessive rhizosphere concentrations of carton
dioxide exhibited symptom development which differed significantly from
that caused by lack of oxygen in the root zone, suggesting that high
CC>2 concentrations damage tomato roots by a mechanism different from
that of low oxygen concentration.
11. Rhododendron appeared to be poorly adapted to both landfill and
control conditions.
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SECTION 3
RECOMMENDATIONS
1. Those responsible for planting vegetation on completed landfills should
avail themselves of current research on the adaptability of species to
landfill conditions and avoid the use of non-tolerant species.
2. A survey of the landfill cover soil prior to establishing vegetation
will help to avoid areas high in gas concentration for locating
vegetation.
3. The use of a barrier technique for excluding landfill gas from the root
zone of vegetation should be considered when planting on a former land-
fill. Two methods to consider would be (a) a mound of soil over the
existing cover, (b) a lined and vented trench backfilled with suitable
soil.
k. The use of smaller planting stock might also increase the chance of
survivab ility.
5. Adequate irrigation of the plants established on a landfill is an
important contribution to their survivability.
6. Special precautions should be taken to insure that the landfill cover
soil has not been too densely compacted by heavy equipment. Loosening
of the soil may be necessary before planting.
7. All cultural practices required for.the successful establishment of
vegetation in non-landfill soils should be considered, i.e. soil
fertility, healthy planting stock, optimal soil density and physical
characteristics, maintenance procedures, etc.
8. Further studies should be undertaken to determine if the ability to
withstand high levels of carbon dioxide in the root zone is a charac-
teristic of flood tolerant species.
9. The influence of secondary factors such as size of trees at planting,
the use of bare-rooted versus containerized trees and the effect of
water stress on the adaptability of species to landfill conditions
should be evaluated.
10. The value of mycorrhizal fungi in inducing tolerance of trees to
landfill conditions should be assessed.
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SECTION U
LITERATURE REVIEW
GAS PRODUCTION IN SANITARY REFUSE LANDFILLS
The serious disadvantages for adequate vegetation growth inherent in
landfill sites; namely the production of toxic gas mixtures from anaerobic
decomposition of organic matter present and leaching of infiltrates and
gases into ground water supplies, as well as high ground temperatures, have
been enumerated (32, hQ, 160).
The composition of landfilled refuse varies considerably depending
on its origin, be it municipal, industrial, incineration material or sewage
sludge. The organic content of solid waste collected from homes, schools,
commercial establishments and industries generally ranges from 50 to 75$
on a weight basis. Most of these organics are biodegradable and can be
broken down into simpler compounds by both aerobic and anaerobic organisms.
The rate at which this occurs is reported to be a function of (a) permeabil-
ity of cover material (b) depth of garbage (c) amount of rainfall (d) mois-
ture content of the refuse, (e) putrescibility of the refuse (f) compaction
(g) pH and (h) age of the landfill (i) redox potential (30, 8?, 103, 138).
The concentration of biocides as well as other factors may also effect the
rate of decomposition.
When the refuse is initially deposited in the landfill, there is
enough oxygen present to support a population of aerobic bacteria. This
state lasts from one day to many months (U9). The literature indicates
carbon dioxide and water to be the principal products formed in aerobic
decomposition (21).
After the oxygen concentration is depleted, the aerobic bacteria die,
resulting in a sharp increase in the anaerobic bacterial population. During
the anaerobic state of decompostion two phases have been identified, a non-
methanogic state followed by a methane-producing stage (2).
During the non-methanogic stage, organic matter is reduced, in the
presence of water and extracellular enzymes produced from bacteria, to
smaller soluble components which include fatty acids, simple sugars, amino
acids and other light-weight compounds (150). During the methanogenic
stage, C02 and CHlf are the principal gases produced. They originate from
two reactions carried out by the bacterium Methano-bacterium (V?).
Various other gases reportedly produced in the anaerobic environment
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of the landfill include ethane, propane, phosphine, hydrogen sulfide,
nitrogen and nitrous oxide (3, 6, Ik, 32, 96, 126, 150). Reserve Synthetic
Fuel Company reports finding over 60 different gases in a California landfill
(Frank Flower, Personal communication with Fred Rice, Reserve Synthetic
Fuel Company March 15, 1977). Hydrogen sulfide which is produced from the
bacterium Desulfovibrio desulfuricans in alkaline conditions (58), causes
lower root respiration rates and a decrease in soil nematode population (8U).
In addition to the methane-producing bacteria mentioned above, there
exists a bacterium, Pseudomonas chromobacterium, which utlizes methane
during its metabolism. It oxidizes methane, producing carbon dioxide and
water (70). Since oxygen is required for this reaction, these bacteria
will generally be found near the upper surface of the landfill.
During the oxidation of methane, oxygen is consumed. This raises a
question of whether or not the oxygen concentration is a limiting factor
in this reaction. Hoeks (70) points out that the organisms involved can
function at soil atmospheric oxygen concentration as low as 1$. However, at
this low concentration, incomplete oxidation causes formation of such inter-
mediate side products as methanol, formaldehyde and formic acid (78).
Of the various factors influencing methane gas production, the
parameters most ccpmonly reported are refuse moisture content, temperature,
oxygen and pH. Frequently the major factor is refuse moisture content.
Ramaswamy (122). and Sougonuga (137) found that methane gas production rates
increase with increased refuse moisture content, with a maximum production
occurring at moisture content of 60 to 80$ wet weight. Farquhar and Rovers
(U7) report maximum methane production when refuse is near the saturation
point. An experiment carried out by Merz and Stone (99) concluded that
methane gas production increased with the addition of surface irrigation
water. Ludwig (9^) found that at one of the two sites in California, methane
production increased after a heavy rainfall. It is reported that refuse
moisture content too low to support continuous gas production in a landfill
may be in the range of 30 to k&fo (99). This condition may exist in certain
areas of the United States such as the dry southwest, where rainfall and
relative humidity are very low.
Temperature has also been described as a limiting factor in the methane
gas production. Kotze et al (82) report 37°C to be the optimum temperature
for methane gas production in the mesophilic stage of sewage sludge de-
composition. Dobson (37) and Ramaswamy (122) say maximum gas production
occurs at 30°C and 35°C respectively. All found that deviations from the
optimum temperature resulted in decreased methane production rates.
The optimum pH for methane production during anaerobic decomposition
of sewage sludge is very near 7.0 (1*7). As deviations from this optimum are
encountered, gas production is decreased. High pH may exist in the refuse
because of the presence of alkaline materials. When methane production is
inhibited, the information of organic acids results and the pH decreases (U7).
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EFFECT OF LANDFILL GASES ON PLANT GROWTH
Field Cases
Many reports of success or proposals for transforming barren former
refuse sites into luxuriant vegetated areas have appeared in the literature
and in the press (5, 12, 6h, 88, 105).
In July 1972 an article by Duane (38) applauding the construction of
golf courses on completed sanitary landfills cited the successful use of such
tree species as Japanese black pine, London plane, thornless honey locust
and Russian olive for beautifying the sites. In 1973, any anonymous article
appeared in Solid Waste Management magazine describing the transformation
"From Refuse Heap to Botanic Garden", of an 87-acre landfill in Los Angeles
that the distinction of being one of the world's first such phenomena (U).
A catalogue published in 1973 describing hybrid poplars bred by a
Pennsylvania nursery cites a particular hybrid which supposedly was grown
successfully on a landfill site at Fort Dix, New Jersey (98). In that same
year, a brochure was published by the Caterpillar Tractor Company describing
and displaying in lavish color various successfully vegetated golf courses
and parks in Mountain View, California; Anoka, Minnesota; Baltimore County,
Maryland; Long Island, New York; Alton and Chicago, Illinois (2k). In 197^
a news item in the Sun-Star of Merced, California described a 5-acre park
whose new grass and trees would be aided in growth by "the proximity to the
refuse which will provide needed nutrients" (6).
Few problems if any were either observed or anticipated in achieving
these spectacular results with the exception of the report of root damage to
large trees and shrubs at the Los Angeles Botanic Garden site.
At the same time, various investigators were experiencing difficulties
in growing vegetation at similar sites. In January 1969? Professor F. Flower
and associates of Rutgers University in New Brunswick, New Jersey (50),
responding to a complaint of vegetation death on private properties adjacent
to a landfill in Cherry Hill Township observed dead trees and shrubs of the
following species: spruce, rhododendron, Japanese yew, azalea, dogwood,
flowering peach, brush dogwood, Scotch broom, arbor vitae, Douglas fir, and
lawn grasses. Testing of the soil with appropriate equipment disclosed high
concentrations of carbon dioxide and explosive gases. The conclusion
reached was that the trees and shrubs may have been killed by displacement
of oxygen from their root zones by lateral movement of the gases of refuse
decomposition or by the decomposition gases themselves.
In 1972, the Rutgers contingent made a visit to the peach orchard of
the DeEugenio Brothers in Glassboro, New Jersey, which bordered on a
completed landfill, where approximately 50 peach trees had died (51). Upon
completion of the landfill, the growers had hoped to plant additional peach
trees on the filled area. Examination of the soil atmosphere revealed high
concentration of carbon dioxide and methane form the anaerobic decomposition
of organic matter had moved laterally from the landfill into the orchard
area.
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The Hunter Farm, in Cinnaminson, New Jersey, was visited in December,
when fields planted with rye were growing poorly (51). Gas checks
revealed that combustible gases were present in the area of new vegetation
injury and that migrating gases were traveling up to 600 feet from the nearest
edge of the landfill.
Another trip to Hunter's Farm was made in June, 1975 when corn was
found to be growing poorly in areas where combustible gas and C02 concen-
tration were high.
On May Ik, 1973, the Rutgers group visited Sharkey's Landfill in
Parsippany-Troy Hills, New Jersey to estimate its potential for supporting
vegetative cover and to examine field test plots set out by the county
agent (53). It appeared that grass seeding had been attempted; however,
grass seemed to be growing well over only small areas of the fill. Numerous
pools of oily leachate were observed, many with gas bubbles breaking the
surface.
Samples of soil gas revealed high concentrations of combustible gases.
In the few areas where vegetation seemed to be growing well, there was little
combustible gas in the root zone.
A communication from the county agent on June 3? 1975 reported that
clover, vetch, lespedeza and weeping love grass were doing well on the
landfill (79).
Although the literature on vegetation problems on completed landfills
is fairly sparse, information received from a nationwide survey has indicated
that such problems have been encountered throughout the United States. On-
site visits (51? 52) to some of these areas in the northeast, the midwest,
southern Alabama, the far west, Puerto Rico and southern California have
corroborated the findings of the group at Rutgers University concerning the
detrimental effect of landfill gases on vegetation atop or adjacent to
completed sanitary refuse landfills.
The discrepancies in results of efforts to establish vegetation on
former landfill sites is apparently due to variability in certain landfill
characteristics such as type and amount of solid waste, depth and permeabil-
ity of cover, construction and grading of the fill; certain meteorological
conditions, such as temperature, relative humidity and rainfall, soil
characteristics such as composition, texture, ability to retain moisture,
nutritional characteristics; adaptability of plant species to landfill
conditions, and planting and maintenance techniques to overcome unfavorable
landfill conditions (17, ^5, 123, 1^2, 15^, l6o).
Effect of Low Soil 02 on Plant Growth
It has been known since the early 1900fs that> plants grown in solution
culture required both air and minerals in order to achieve the best growth
(Mt), this was found to be the case for barley, lupines (66, 127), and
tomato (28, 1*1).
8
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Chang and Loomis in 19^5 (26) conducted a survey of the literature and
found that although some plants could survive 02 concentrations in the root
zone as low as 1 to 2%, most plants would function normally at 0? concentra-
tions ranging from 5 to
There is a good deal of variability in tolerance to low 0 in the root
zone among different species of plants. The growth of red and'Talack rasp-
berries was inhibited by exposure to 10% 0 (120) , whereas apple trees
required 10% 0 in the soil in order to sustain growth (15). One-tenth per-
cent Og in the flooded root zone of apple trees resulted in the death of the
trees (15). Tomato plants grown in solution culture exhibited marked reduc-
tion in growth and ability to take up potassium when exposed to 3% 0 in the
root zone (153). Sour-orange seedlings in sand-solution culture given 1.5%
Op in the root zone for seventeen weeks did not grow, and seedlings receiving
k.6 to 6.1% ©2 grew half as well as the controls (62). Rice plants have been
reported to grow as well in solution culture having less than 1% 02 in the
root zone as control plants (153).
Aside from differences between species, environmental factors can also
influence plant response to low 02. High temperatures were found to increase
the need for 02 by growing root tips (120). A dense soil can also increase
the need for 0^ by growing root tips. This is believed to be due to the
extra energy required to push the root tips through the soil (6l). The 02
concentration in the soil is dependent on the ability of air to diffuse into
and through the soil and the rate of diffusion is largely dependent on the
texture and degree of compaction of the soil. Sandy soils generally exhibit
ample gas exchange, whereas finely textured soils with pore spaces of less
than 10% are prone to poor, soil aeration (155 , l6l). Excessive compaction
in soils containing large amounts of clay was found to result in 02 concen-
trations of less than 2% and C02 concentrations as high as 20.5
Low concentrations of 02 in the root zone can influence plants in ways
other than by decreasing growth or killing the plants. Susceptibility of
roots to soil-borne pathogens has been found to increase when the soil is
poorly aerated. This is believed to be due in part to the ability of some
pathogenic fungi and other organisms to flourish in such soils (8). Sus-
tained low Q>2 concentrations in the soil have been found to cause mineral
deficiencies in plants. Potassium is the first mineral affected. The order
in which the other major nutrients, nitrogen, phosphorus, calcium, and magne-
sium,become deficient depends upon the plant species (69, 78, 91)-
Effect of High Soil C02 on Plant Growth
Carbon dioxide (C02) concentrations in the soil normally comprise less
than 2% of the soil atmosphere. The death of vegetation in flooded or poorly
aerated soils is not generally considered to be due to excessive C02 concen-
trations but rather to lack of oxygen (85). C02 concentrations as high as
20.5% have been reported in the soil under roadways and compacted paths in
areas where trees were reported to have been killed, but the high C02 read-
ings occurred in conjunction with very low 02 concentrations (162).
-------
In a sanitary landfill, the refuse is a source of C02 which can migrate
into the surrounding soil, resulting in concentrations greater than 20$ (52).
The C02 migrating into the soil can displace the 02, but not being dependent
on the soil 02 for its generation, it can occur in high concentrations in
conjunction with 02 concentrations which might not be considered limiting
to plant growth.
Plant species vary in their sensitivity to excessive C02 in the root zone
The exposure of plant roots to pure C02 was first shown to be toxic in 191^
(109). Pure C02 in soil around tomato and corn plants killed the plants
after two weeks exposure (109). This was also found to be true for buck-
wheat which was killed after a few days' root exposure to pure C02 (56).
The growth of guayule in solution culture exhibited a significant
reduction (20), and red and black raspberries were killed when exposed to 10%
C02 in the root zone (120). Cotton plants growing in solution culture
exhibited optimum growth in the presence of 10$ C02 in the root zone, provid-
ed at least 7.5$ Og was also present. Thirty to 1*0$ C02 in the root zone
severely limited growth, and 60$ C02 stopped growth of cotton completely (9°)-
Tomato plants growing in solution culture exhibited a significant reduction
in growth when exposed to 28$ C02 for 2k hours, but were not inhibited by
lower concentrations (kk). Pea seedlings have been reported to exhibit a
significant reduction in growth when exposed to only 1$ C02 in the root zone
(lU3) whereas barley plants growing in solution culture exhibited no reduction
in growth when exposed to 20$ C02 in the root zone (69). The roots of sour-
orange seedlings growing in sand solution culture only ceased growing when
exposed to 37.2$ C02 (62).
Root growth of pea seedling has been reported to be stimulated by
exposure to 0.5$ C02 and inhibited by 1$ C02 in the substrate (59, 1^3). Tne
roots that were stimulated by exposure to low C02 concentrations were thinner
and had an increased amount of lateral root initials. This stimulatory
effect of low concentrations of C02 was attributed by the authors to the
ability of the roots to use C02 as a carbon source (59, Il6, 1^3). In light
of more recent developments this stimulatory response is probably due to the
C02 acting as an analogue to ethylene, competing for a receptor site in the
cell. This competition would result in a hormonal imbalance that would
manifest itself as a more pronounced auxin response (22, 25).
Valmis and Davis (53) investigated the mechanism by which C02 damages
plant roots and demonstrated differences in sensitivity among plant species
to exposure to C02 in the root zone. Tomato roots growing in solution cul-
ture exposed to pure C02 were killed immediately. The exposure of tomato
roots under the same conditions to pure nitrogen resulted in a 90$ reduction
in the rate of growth. Rice plants were also killed by exposure to pure C02
in the root zone but exhibited no measurable reduction in rate of growth
when exposed to pure nitrogen. Barley plants were killed by exposure to
pure C02 and exhibited a 1*5$ reduction in the rate of growth when exposed
to pure nitrogen. This study shows that high C02 concentrations can kill
plants by a mechanism other than lack of 02. Norris et al (108), in 1959
postulated that the damage caused by C02 contamination in the root zone
occurs when the C02 diffuses across the plasma membrane and disrupts the
10
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intercellular pH.
TO s^arise car, ,on
the root zone can be toxic to roots^
dependent. c™ce"£f lo"*e°£^iL by vhich C02 damages plant roots is not
So^ut SeTvSnce SdicSerthat It is not the sane -ctanl. by vhich
lack of 02 damages plants.
«
extensively studied as a phytotoxic gas when present
in soiospr ao! £ literate on the effects of manufac-
tured gas could be enlightening.
™. *• 4- ^nvtPd incident of manufactured illuminating- gas damage to
The first ^"telujj1 Condon in l80? after the first public street
trees occurred on ^f .^^'(i^). In the late l800's and early 1900' s
light system ever wa ^J^^ wody ^ herbacious plants were
manufactured-gas (83, 132,
^ T5^00 Tl n reported that ethylene was one of the toxic
Harvey andRose 7 xn P speciosa? Aiianthus altissima, Vi£ia
components of ^a^^|f verFHvidedinto-bwo treatments, one group
— ' rJo^TTIuHnlting gS and the other to ethylene. The seedlings re-
exposed to ^^^^ to both treatments. Ethylene concentration in
sponded in a similar ^^ enou^ that leaks could be detected by
manufactured gas was usually nign ^ observations for epinastic
placing ^fP^!^) il has been shown that ethylene can be
SS Jneconcen?Sti3ons'which are biological^ active in anaerobic
soils (133).
,4. u v o-i- fli (68} in 193^ reported that container-grown willow,
Sf a£ silver bell trees were severely injured when their roots
^ple and « oe
H a silver e
cherry, ^ple and «£^ for 30 minutes. When cyanogen was removed
vere exposed to ma nufa ctu re g ^ ^ ^ ^ ^^ .n.ury
* -in Tontine cas 20 to 24 times more gas was rey.uj.i-eu. ow •_«,«= ^0^
from illummating gas 2U ic acid when mixed with water and
to the trees ^^gen^s well as ethylene, has been considered to be
carbon dioxide. . Jyanogen^a toxicit of inuminating gas in soils.
SfcomJ^d aree not foun'd L landfill gases or natural gas in concentra-
tions netrTas high as in manufactured gas, xf at all.
Effect of Natural Gas on Plant Growth
^n-Hon of natural gas more closely resembles that of landfill
The W^^LSrSd gas (Table l). The main difference between natu-
fal ST^IaSS gnSSthai there is more C02 and less methane in the
latter.
That natural Bas can
to the soil occurred. Exposing
11
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the aerial portions of plants to natural gas did not damage the vegetation
(136).
Gustafson (65) in 191*9 fumigated the roots of container-grown American
elm trees during four consecutive growing seasons with concentrations of
natural gas not exceeding h%. Although slight discoloration of the roots was
noted on the trees exposed to the gas, no injury to the shoots was reported.
Pirone (115) in 1960 reported that exposing the roots of tomato plants
to pure natural gas for U8 hours did not cause any damage. The roots of
Norway maples, London plane and pin oaks were fumigated with pure natural gas
for 5 to 6 week periods at soil concentrations ranging from 60 to 100%. No
damage to the trees was reported due to this treatment.
f
In 1972, Hoeks (70) reported that natural gas was responsible for the
demise of 5 to 20$ of the road trees in town centers in the Netherlands. He
found that when soil was contaminated with natural gas for a period of time
there was a build up of methane-utilizing bacteria whose activity resulted in
the depletion of oxygen in the soil. The oxidation of methane follows the
general equation (CTfy + 202 = C02 + 2H20 + Energy). The organisms responsible
for this reaction belong to the Pseudomonas and Chromobacteria genera. Under
experimental conditions the oxidation of methane was found to be so intensive
that if 02 was in excess all the CH1+ was depleted, and if CH^ was in excess
all the 02 was utilized. This bacterial activity, in conjunction with simple
displacement of the soil atmosphere by natural gas, was concluded by Hoeks to
be responsible for the death of the many shade trees in the Netherlands.
Garner (58) in 1973 investigated the death of numerous shade trees near
natural gas leaks in Wilmington, North Carolina, and concluded that the death
of the trees was due to anaerobic soil conditions brought on by dilution of
the soil atmosphere with natural gas and the activity of methane-utilizing
bacteria. Garner also partially attributed the death of vegetation to the
build up of hydrogen sulfide (H2S) in the soil produced by Disulfovibrio
desulfuricans under anaerobic conditions. He also reported extremely low
soil nematode populations due to ^S toxicity.
THE EFFECT OF SOIL FLOODING ON PLANT GROWTH
Soil saturated with landfill gases (52) or with water (86) often becomes
anaerobic. The ability of a plant to survive in anaerobic soil is character-
istic of flood tolerant species (6l, 158). Such species, therefore, might
prove adaptable to adverse growing conditions caused by refuse-generated
gases on completed sanitary landfills.
Species vary considerably in their ability to withstand flooding due to
a number of biological and environmental factors which are known to influence
the ability of a tree species to survive in flooded soil. This is evident in
the observable zonation of tree species on river •banks, reservoir margins and
bottom lands (19, 66, 7^). Hardwood species are generally more tolerant of
flooding than conifers (1, 6l, 92). Soil type can also influence flood
tolerance. In the U. S. S.R. on the Volga-Don flood plain Populus alba, P.
12
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balamifera are recommended for clay- loam sites while P_._ nigra and Acer negundo
are recommended for sand- silt sites (151). The time and duration of flooding
are important considerations. Dormant trees are less sensitive to flooding
than actively growing trees (66). Trees growing on the margins of reservoirs
require that the site be flooded no more than k5% of the growing season in
order to survive (66). In isolated years some species can tolerate flooding
during the entire growing season (60). The condition of the flood water is
another factor which may influence flood tolerance. Flooding with standing
water is more injurious than flooding with moving water (129). Warm water can
accelerate the death of trees exposed to flooding (19). If the flood water
covers all or most of the trees above the ground, the tree is more likely to
be injured than if only the soil is saturated (66). Older trees are generally
more tolerant of flooding. This was found true both for hardwoods (80) and
conifers (89).
In order for a species to survive flooding it must possess special char-
acteristics that enable it to survive when the soil is anaerobic. Some
species have the ability to undergo anaerobic respiration in the roots when
flooded. Species which have been shown to do this are Salix cinerea and Nyssa
aquatica (39 > 72). The prolonged dependence upon anaerobic respiration can
result in a build-up of toxic end products, such as ethanol, which can then
become toxic to the plant (57, 76). Hook (72) has postulated that Nyssa
aquatica can avoid being damaged in this way by producing secondary roots,
thus increasing the size of the root system to compensate for the lack of
efficiency and reducing the concentration of ethanol per unit tissue.
A large number of plants possess the ability to transport oxygen to their
roots. This characteristic is associated with but not confined to flood-
tolerant species. Corn, turnips, barley, carrot, lettuce, beets', leek, pea,
onion, rye grass and cabbage (63) all have been shown to transport oxygen to
their roots, but none of these species is considered flood-tolerant (72).
This adaptation is more common in herbaceous species (6l). Woody species,
including Populus petrowskyana, Salix alba, §. repens , £3. atrocinerea and S.
fragilus have also been shown to transport oxygen to the roots. Lenticels on
the stem were shown to contribute to this process (7, 27). Other woody
species which can transport oxygen to their roots include Fraxinus pennsylva-
nicum, Nyssa aquatica, N. sylvatica, Avicennia nitida, Picea abies , Liqui-
dambar styracif lua , Liriodendron tulipfera, and Platanus occidentalis (73).
Ananas comosus (pineapple) can also transport oxygen to its roots. The gas
moving to the roots was observed to contain up to 78$ oxygen, most of which
was believed to have been produced during photosynthesis
The ability to develop adventitious and secondary roots has also been
associated with flood tolerance (60). The original root systems of the flood-
tolerant species Fraxinus pennsylvanicum , Platanus occidentalis, and Nyssa
aquatica deteriorate when flooded, but secondary roots develop to replace
them which are more succulent and less branched (71). Most flood- tolerant
species develop adventitious roots at or below the water line (60). The
adventitious roots of Salix alba can replace the original root system by
growing in the sediment deposited by flood water (119). This could also be
true for other species. It has been postulated that adventitious roots in
flood water can carry on the salt- absorb ing function while the damaged
13
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original root system continues to contribute to the water absorbing needs of
the tree (85).
The ability to withstand elevated concentrations of CC>2 in the soil has
been proposed as contributing to species ability to withstand flooding (72).
This possibility has been neglected due to the generally accepted belief that
low oxygen and not high C02 is the main cause of damage to roots in flooded
soils (86). Nyssa aquatica seedlings are more tolerant of flooding and of
high C02 concentrations in the root zone than Liquidambar straciflua. N.
aquatica was not affected by exposure to 2 or 10% CC>2 in the root zone for up
to 15 days, whereas 30/0 C02 over the same period retarded root and shoot de-
velopment and decreased the rate of transpiration. L. styraciflua exhibited
chlorosis when exposed to 2$ and was killed by exposure to 10 to 30% C02 for
15 days (71).
The exact nature of the flood-tolerance mechanism for any species has
not been determined. There could be contributing mechanisms other than the
ones discussed above. The work done indicates -that a combination of adapta-
tions can be responsible for flood tolerance. Nyssa aquatica is tolerant of
high C02 concentrations in the soil, it can undergo anaerobic respiration, it
develops adventitious and secondary roots and it can transport oxygen to the
roots. All these adaptations are believed to contribute to its tolerance of
flooding (72). The ability of five hardwood trees to tolerate flooding was
found to correspond to their ability to transport 02 to the roots, develop
adventitious roots and undergo anaerobic respiration. The more flood toler-
ant the tree, the more developed were these adaptations. The trees in order
of increasing flood tolerance were Liriodendron tulipifera, Liquidambar styra-
ciflua, Flatanus Occidentalis, Fraxinus pennsylvanica and Nyssa aquatica (7lX
The mechanisms which enable a species to adapt to flooding have evolved
in response to flooding. The conditions on a sanitary landfill may resemble
flooding in terms of anaerobic soil conditions but there are significant dif-
ferences between the two environments, the most dramatic departure being the
lack of water on the landfills. Most flood tolerant species develop adventi-
tious roots which would not be able to develop under landfill conditions due
to the lack of water. It is not known to what extent these roots contribute
to flood tolerance. It has been postulated that adventitious roots develop
in response to a build-up of growth regulators and carbohydrates at the base
of the stem and are a response rather than adaptation to flooding (8U).
Anaerobic soil conditions could be more stable on a landfill than during
flooding and not give the trees a chance to grow at all. The ability to
withstand high concentrations of C02 in the soil might be more important on a
landfill where the concentrations of C02 in the soil can exceed kctfo (52).
EFFECT OF OTHER SOIL PARAMETERS ON PLANT GROWTH
Soil Temperature
A number of investigators have characterized the optimum temperature for
root growth of some selected species. As early as the 19th century, King
found that corn roots responded quite differently to different soil tempera-
-------
tures throughout the growing season (77). Early in the season, cooler soil
temperatures promoted more horizontal root grovrth than later in the season
when higher soil temperatures caused the roots to respond by growing verti-
cally. Burstrom (23) in 1936, found that total growth in length of wheat
roots is optimum at temperatures around 68°F and decreases at temperatures
above and below this optimum. Richardson (121*) described a similar relation-
ship for silver maple (Acer saccharinum). Soil temperatures of 68°F were
reported by Rufelt (128) as optimum for maximum growth of wheat plants. The
tops of oats generally grow better at 70°F and the roots at 6o°F indicating
a difference in the optimum temperature for root and shoot growth, respec-
tively.
Total dry weights of both roots and shoots are influenced by the tem-
perature of the root zone. Maximum dry weight of wheat plants increased with
decreasing temperatures from 86°F to 50°F, whereas optimum growth of rye
grass tops occurred at 67°F with growth decreasing as the temperature was
raised to 82°F or lowered to 52°F (107). This same temperature range has
been reported for barley (118), rye grass (110), corn, bromegrass (106), oats,
tobacco (111), and tomato tops (3^). The root growth of wheat and other
species was found to be optimum at about 68°F whereas Italian rye grass roots
grew best at 52°F (106).
Moisture Stress
Because of their perennial nature, long life, and potentially large size,
trees require special consideration in the study of their growth and develop-
ment under environmental stress. For example, water stresses during several
separate growing seasons may affect each year's growth increment and thus,
the effect of a given water stress is different in a tree seedling than in a
mature tree. Drought during a critical period one year may result in reduced
food storage for utilization in growth the following year, and the effect on
development of wood tissue or of flowers and fruits can be appreciable for
several succeeding years. The root/shoot ratio may be seriously affected by
water deficits in woody seedlings, whereas in large trees the more important
effect of the same deficits may be in the distribution of growth along the
annual sheath of wood.
There is convincing indirect evidence that shoot growth in trees is
related to water stress. Forest mensurationists find tree height the most
sensitive growth parameter for measuring site productivity, to which the
generally accepted key is soil moisture (121, lUl, 159). Correlations be-
tween rainfall and shoot growth have been attempted with various degrees of
success for many decades (102, 113), but there is little doubt that longer
shoots are produced in wet years than in dry years by many tree species on
upland sites. Root tissues are probably never at as severe water stress as
shoot tissue because of the time lag in the build up of water tension between
the transpiring leaf and the absorbing root.
Soil water stress reduces the number, rate of expansion, and final size
of leaves. In species whose entire leaf crop for one year is present as
preformed primordia in the overwintering bud, water stresses of the preceding
year regulate the numbers of leaf primordia that form in the developing bud
15
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(40, 8l). In these species, e.g. Pinus strobus, water stress during the
period of shoot growth has no significant effect on the numbers of leaves
that mature, but results in smaller leaves spaced closer together and ulti-
mately less leaf weight (93). Clemments (29) found that numbers of needle
fascicles on current shoots of 20-and 5-year old Pinus resinosa were directly
proportional to the frequency of irrigation during the previous growing sea-
son. Therefore, it can be concluded that the previous year's deficits may
affect tree species whose leaf primordia are all preformed in the overwinter-
ing bud by reducing leaf numbers, and that current year deficits may reduce
the size of leaves and their spacing along the shoots. In other species e.g.
Pinus taeda, which can add new foliage throughout the growing season, not all
leaf primordia are preformed in overwintering buds, so water deficits during
the season of flushing probably reduce production as much as deficits of the
previous season (163). Zahner (163) showed that for sapling-size Pinus taeda
grown outdoors in large containers, the 2-year effect on elongation of the
terminal leader of well-watered trees was almost twice that of trees subjected
to extreme drought conditions.
Lotan and Zahner (93) measured elongating needles on 20-year old Pinus
resinosa trees under conditions of imposed drought and irrigation. Needles
on the irrigated trees expanded for several weeks longer, at a 30$ faster
rate, and reached a Uo$> greater length than needles of trees under the drought
treatment.
Root growth is also adversely affected by soil moisture stress. Two
studies have emphasized that resistance increases sharply as the soil dries,
and the resulting physical impedence of penetration by a root tip is consid-
ered a limiting factor independent of the deficiency of water for absorption
(10, 1^8). Therefore, the failure of roots to grow into dry soil is probably
more the result of physical impedence than of soil water stress. However,
cambial growth continues slowly in dry soil because dry soil should not ap-
preciably affect secondary growth (8l).
EFFECT OF SOIL PARAMETERS ON SOIL PROPERTIES
Soil Temperature
The processes of ammonification and.nitrification in soil are among those
affected by soil temperature (128, 157). A temperature between 77°F and 99°F
was found to be optimum for the activities of the nitrifying bacteria (1^7,
156); above 130°F and below U5°F the nitrification rate was severely reduced
(156). Ammonification requires a higher optimum temperature (iOh°F) and the
bacteria responsible can remain active at higher temperatures than the nitri-
fying bacteria. Frederick (55) and Sabey (130) studied nitrification in
greenhouse pots of soil without plants. Both corroborated the results of the
previous investigators in that higher rates of nitrification were associated
with increasing temperatures (from 36°F to 95°F and from 32°F to 86°F,
respectively) and that nitrate formation was entirely inhibited at tempera-
tures of 10U°F (lU7, 156).
16
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Low 02 Tension
Several investigators have found that oxygen concentration in the soil
strongly influences the fate of many soil components by altering soil reac-
tions and finally affecting plant growth.
Ponnamperuma (11?) has reviewed a large quantity of the literature con-
cerning the dynamics of flooded soils i.e. soils low in oxygen concentration.
It is common knowledge that the moment a soil is flooded, its oxygen supply
is virtually cut off. Oxygen can enter the soil only by molecular diffusion
(which is 10,000 times slower than in the absence of water) (71) or by diffu-
sion of gaseous oxygen through plants from aerial parts through aerenchyma
cells continuous with the roots.
When the oxygen supply to the soil is cut off, aerobic organisms quickly
deplete the oxygen remaining in the soil and become quiescent or die. The
facultative anaerobes, followed by the obligatory anaerobic organisms, then
take over the decomposition of soil organic matter; using oxidized soil com-
ponents such as nitrate, manganic oxides, ferric oxides, sulfate, or phos-
phate; or dissimilation products of organic matter as electron acceptors in
respiration.
Nitrate is the first soil component to undergo extensive reduction when
oxygen becomes limited (117). Although it is known that nitrate reduction
(denitrification) often occurs in slight amounts in well-aerated soils at
optimum moisture level, the percentage of nitrate lost is usually not signif-
icant until the oxygen concentration is 12$ or lower. A concentration of
0.^6$ oxygen resulted in-comparatively large nitrate losses through denitri-
fication (18).
Almost coincident with denitrification is the reduction of the higher
oxides of manganese (Mn02, 1^03, Mn30^)} because of their similarity to
nitrates with respect to redox potential in flooded soils. The reduction may
result from these compounds functioning as either (a) electron acceptors in
the respiration of microorganisms or (b) chemical oxidants (95). Reduction
of the oxidized forms of manganese causes an increase in soluble or
manganous-manganese in the soil solution.
The next soil constituent to be reduced in the thermodynamic sequence is
Fe(OH>2 . This reduction process operates at a considerably lower redox
potential than that required for the two previously mentioned compounds (31).
The process releases soluble or ferrous iron into the soil solution which can
then be taken up by plants or complexed with other molecules.
The reduction of sulfate to sulfide occurs only when the soil has under-
gone appreciable reduction i.e. when the redox potential has fallen to a very
low value (U6). However, in soils high in iron, the likelihood of I^S toxic-
ity to plant roots is minimal because of the formation of insoluble FeS.
17
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ESTABLISHING VEGETATION ON LANDFILLS
Cremer (33), in 1972, planted seedlings of four species of pine in a
simulated sanitary landfill wherein raw refuse was placed in steel containers
on top of which was placed two feet of soil. After one year the seedlings in
these containers were growing as well as the controls.
More, Molze and Browning (101) , in 197^, proposed that transpiration by
vegetation can reduce the amount of leachate escaping from a landfill. Their
study was conducted in a lysimeter designed to simulate landfill conditions.
Raw refuse was interspaced with soil in the lysimeter and two feet of soil
placed on top. Four woody species were then placed in the lysimeter: silver-
berry (Elaeganus pungens), black locust (Robinia pseudoacacia), bristly locust
(Robinia hispida), and slash pine (Pinus elliottiij^All these species grew
well in the simulated landfill and were able to reduce the amount of water
leached from the modified lysimeters. The roots of the plants grew through
the refuse and no methane was reported to have been produced in the lysim-
eters, indicating that anaerobic conditions did not occur in this simulated
sanitary landfill.
Such systems in which small amounts of refuse are placed in containers
(lysimeter) do not reproduce true landfill conditions. The small amounts of
refuse used cannot duplicate the temperature, gas production or settlement
generated by the large quantities of refuse that occur in real landfills.
Swope (1^6) in 1975s conducted a survey of 2k completed landfills in the
state of Pennsylvania. He concluded that 19 of the 2h landfills had vegeta-
tive cover inadequate to prevent erosion. Considering only the seeded
portions of the nineteen revegetated landfills, twelve were observed to have
cover inadequate to prevent erosion. Of five landfills on which no attempts
had been made to establish vegetation, four were judged to have a cover of
volunteer vegetation inadequate to prevent erosion. The physical soil char-
acteristics most often found limiting to vegetative growth were: low soil
fertility, droughtiness, high percentage of course fragments in the soil,
slope, and lack of adequate soil cover. The effects of landfill gas contami-
nation of the soil were not examined.
There have been numerous attempts to establish trees and other forms of
vegetation on completed sanitary landfills (52). These attempts unfortu-
nately were not designed as controlled experiments. In a national survey,
Flower et al (52), examined a number of completed sanitary landfills and
reported that problems with the establishment of vegetation included: lack of
soil cover, droughty conditions, poor quality cover material, poor planting
practices, lack of care, and landfill gas contamination of the soil. In many
instances there was a strong direct correlation between the poor growth of
vegetation and the occurrence of landfill gases in the soil. Symptoms exhib-
ited by woody species exposed to landfill gas contamination were: a general
lack of vigor, dieback, scorching of the leaves or needles, and rapid death.
The death of vegetation on or adjacent to landfills caused by landfill gases
has also been reported in Japan (152), and Canada (6).
18
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SECTION 5
EXPERIMENTAL PROCEDURES
FIELD STUDIES
Selection of Appropriate Site for Landfill Vegetation Field Study
An ideal site for the species screening and gas-barrier technique study
was defined as one which has a relatively high combustible gas concentration
and adequate drainage. The control site should be located on virgin land,
close to, but not adjacent to the landfill and have no combustible gas in its
soil atmosphere. The sites should be large enough to accommodate a four foot
spacing between adjacent trees.
An appropriate site for the experiment was located on the tidal marsh of
the Raritan River in East Brunswick, New Jersey a distance of about two miles
from the Cook Campus (Figure 1). The site had been operated as a landfill
since the early- 1960 's by the Herbert Sand Company which offered space on the
landfill and space on a nearby undisturbed tract of land for the experimental
and control plots respectively.
Adjacent to the southern boundary of the landfill is a woodlot. This
was an island used as a defensive position by colonial forces during the
Revolution. All other landfill boundaries are tidal creeks that flow into
the Raritan River or other landfills located over marshland.
The geologic history of this area is Atlantic Coastal Plain with the
Piedmont Plateau boundary less than one mile to the North and West. Accord-
ing to Patrick et al (112), the soil would be sassafras loam or sandy loam
with a sand deposit that is quarried on the southern side of the woodlot.
The soil covering the landfill seems to be a sassafras subsoil as indicated
by the presence of quartz and other stones with a reddish-yellow to yellow-
brown tint
Characterization of Vegetation on Edgeboro 'Landfill
In order to evaluate the degree of change imposed on the area by our
experimental plantings, we first characterized volunteer vegetation in the
area. For the most part the work in surveying the native vegetation was
accomplished with a minimum of equipment (36). The mapping was performed by
use of a hand-held compass, and the distances were measured by pacing on the
landfill and by the use of a wheeled odometer on the woodlot. The bearings
and distances measured were placed on graph paper to show the respective out-
lines of the two areas studied. Plotting the map on graph paper helped in
determining the area by the formula using a coordinate system.
19
-------
•u
-*-Jt
:w Jersey Turnpiki
Interchange #9
•^-.neroerT; y.
Av Sand Company
Township of
Brunswick, N. J.
Control Plot
Experimental Plot
Figure 1. Location of landfill vegetation growth experiment,
East Brunswick, New Jersey
20
-------
2(Area) = Y-X + Y(X-X) + ... Y-X) (IX*).
Twenty- five randomly stratified plots, 50x50 feet, were used to deter-
mine the composition and successional changes in the woodlot (Figure 2). In
each plot, the DBH (diameter at breast height, k^ feet) of all trees over two
and one-half inches was recorded with the use of a 2k- inch tree caliper. In
the case of one sassafras tree a metric biltmore stick graduated at two cen-
timeter intervals was used and the result converted to the English system.
The shrub layer was measured by the number of stems in a plot.
On the landfill, stems of aJI woody species were counted since only three
trees were above the minimum stem DBH of two and one-half inches. As a check
to note the effectiveness of the woodlot as a seed source, the number of
stems on each side of the road dividing the landfill approximately in half
from the southwest corner to the northeast corner was determined.
Unfilled Island Vegetation--
The island was divided into nine different regions that are at varying
stages of succession or are dominated by a defined cover type (Figure 2).
1) Grass and rose stage - Here the dominant species are Andropogon
virginicus , Phragmites australis and Rosa spp. Over most of the area
Andropogon is dominant except where the moisture seems to collect, and here
Phragmites will tend to be dominant. Different species of wild roses come up
through these grasses and tend to prepare the soil for the next stage of
development.
2) Bayberry- smooth sumac stage - The roses give way to a thick shrub
cover of bayberry (Myrica pensylvanica) and smooth sumac (Rhus glabra) .
Seedlings of black cherry (Prunus serotina) and black gum (Nyssa sylvatica)
appear through this canopy starting the succession toward a forest cover type.
Arrowwood viburnum (Viburnum dentatum) acts as an understory to both sumac
and bayberry, but eventually replaces the latter as the dominant shrub while
the former attempts to become the canopy species.
3) Smooth sumac-black cherry- sassafras stage - A tree canopy becomes
established with sumac and cherry predominating and sassafras (Sassafras
albidium) advancing as a challenger for the dominant position. Smooth sumac
has to be considered a tree species here since it reaches 20 feet in height
and a maximum of 5^ inches DBH. Black gum is co-dominant to the other three
species while the major understory species is flowering dogwood (Cornus
florida). Bayberry is still present in the shrub layer, but is losing fast
to the Arrowwood viburnum under a closed canopy. A small number of red maple
(Acer rubrum) are associated, but never become more than an associated co-
dominant species.
k) Black cherry- sassafras-black gum stage - This stage is more or less
the same as the previous stage, but smooth sumac has dropped out from com-
petition and oak-hickory regeneration has started. The shrub layer is domi-
nated by arrowwood and the understory by flowering dogwood. After this stage
the succession will go to oak-hickory or to sassafras if it can regenerate
21
-------
ro
ro
Landfill Species
Successional
Stages of Woodlot
Sampling Plots
Grass and Rose
Bayberry-Sumac
Sumac-Blk. Cherry-Sassafras
Blk.Cherry-Sassafras-Blk.Gum
5 Ailanthus-Blk. Cherry
6 M Oak-Hickory
7 PJJ Sassafras
8 pj Pine-Oak
9 Evl Aspen-Birch
Figure 2. Species distribution on landfill and successional stages on adjoining woodlot.
-------
vigorously.
5) Ailanthus-black cherry stage - Ailanthus (Ailanthus altissima)
replaced, smooth sumac earlier in the succession and becomes the dominant
species with black cherry co- dominating. The succession seems to follow the
same sequence as from stage 3) , the only exception being that Ailanthus will
take longer to succumb to the more tolerant species so that oak-hickory re-
generation will occur while it is still present in the canopy.
6) Oak-hickory stage - This type resembles Type kO (Post Oak-Black Oak)
of the Society of American Foresters (5^). Black oak ( Quercus velutina) and
bitternut hickory ( Carya cordiformis^l are the dominate canopy trees with
black gum, post oak ( Quercus stellata) , sassafras and black cherry in the
co-dominate position.
7) Sassafras stage - An allelopathic substance from the leaves of
sassafras inhibits the regeneration of other species and a stand is produced
that will be mono- species in content for a long part of its life. The re-
generation of sassafras under its own canopy is slow to non-existent in older
stands. The stand in the woodlot has the largest tree present, 33 inches
DBH, plus two others over 20 inches DBH. This is S.A.F. Type 6k
8) Pine-oak stage - This is a Society of American Foresters (S.A.F.)
Type 76 (5U) with Virginia pine (Pinus virginiana) dominant with advance oak
regeneration of post oak, black oak, blackjack oak ( Quercus marilandica) , and
pin oak ( Quercus palustris) as the rising co-dominant species (97). Red.
maple is associated with this cover type and would seem to take a secondary
position with black gum to the species mentioned above.
9) Aspen-birch stage - Although this is an earlier transition form, it
is not the dominate form on the north side of the woodlot. On the south side
this quaking aspen-grey birch variation of S.A.F. Type 19 (5^) has a much
higher coverage. Quaking aspen (Populus tremuloides) and grey birch (Be tula
populifolia) form the dominate cover of this area with a shrub layer changing
from bayberry to arrowwood. The associated species are black gum and Malus
spp. , the latter is either a domestic apple or one of the types of wild
crabapples.
Landfill Vegetation—
The landfill itself is still too early in succession to designate a
forest cover type or one that may be emerging, so three areas of examination
were conducted: the ground cover, the shrub layer and the arborescent vege-
tation that is developing.
1) Ground cover - This is very similar to stage one in the woodlot,
Andropogon is predominant with Phragmites localized. Trailing strawberry
( Euonymus obvatus ) and greenbriar (Smilax rotundifolia) crisscross the open
areas with the former being the only live vegetation over the gas upwellings
when it sends a stolon from one side of the gas area to the other.
2) Shrub layer - Bayberry and smooth sumac are the predominant shrubs,
forming pure patches in localized areas scattered over the landfill. Not as
23
-------
numerous, but still present are the wild roses and the Malus spp. found as
scattered bushes over the area. Found now in greater numbers or for the
first time, are the black haw (Viburnum prunifolium), highbush blueberry
(Vaccinium corymbossa) and witch hazel (Hamamelis virginiana), probably from
the Raritan River Flood Plain, which represents another seed source influ-
encing the landfill site. These occur as scattered bushes for the most part.
3a) Arborescent vegetation, north side - Black cherry is very numerous,
being about six times as numerous as ailanthus, black gum, and red maple.
Lesser amounts of pin oak, sweet gum (Liquid-ambar styraciflua), boxelder
(Acer negundo), green ash (Fraxinus pennsylvanica), and cottonwood (Populus
deltoides), again probably from the flood plain, were found with the usual
old-field species grey birch, eastern redcedar (Juniperus virginiana), short-
leaf pine, sassafras, and black locust (Robinia pseudoacacia). Most of the
tree forms occur on the edge of the landfill where there is probably more
soil and less refuse. Absence of any gas upwelling seems to be responsible
for the growth of most, if not all, these trees.
3b) Aborescent vegetation, south side - The area here is greater than
that on the north side of the road, but the vegetation is sparser. The num-
bers of black cherry are about one-third less than on the other side, but it
is still the most numerous species found. A small grove of green ash is
found on the northeastern corner of this section, near a patch of Phragmites,
numbering about two-thirds the amount of black cherry found here. Associated
with the green ash are boxelder, and honeylocust (Gleditsia triacanthos),
again species found on river bottoms. The rest of the species found in
reducing frequency are eastern redcedar, grey birch, red maple, sassafras,
ailanthus, shortleaf pine, black gum, and quaking aspen, all of which are
found in the woodlot.
Discussion—
At first the flood plain was not considered a major seed source, but
because of the prevailing winds from the northwest and the large numbers of
birds and rodents from the flood plain visiting the landfill, a reversal in
thinking occurred after the data were collected. The prevailing winds work
against the woodlot as a source of windblown seed as shown by the low number
of shortleaf pine seedlings. The seedlings of pine found on the landfill
showed a distribution pattern emanating from the southwest. When the winds
are from this direction they blow through the pine stand. The flood plain is
then the major source of wind-blown seeds while probably equal to the woodlot
as a source of animal-borne seeds.
The presence of two seed sources will show a different trend than that
seen in the woodlot. This greater number of species may be an added benefit
since a greater variety of responses of more trees can be seen than if there
were but one seed source.
*
Any trend now seen on the landfill would be superficial, since major
root competition is just beginning to occur in the soil. The soil depth
varies on the landfill from the edges where more soil is usually found to
the areas of gas upwellings that have been eroded by the wind to expose the
refuse. Billings (13) states that Virginia pine has most (56-6k%) of its
-------
root system in the top 6 inches of soil, while oaks and other more tolerant
species tend to have deeper root systems. The distribution of roots into the
deeper portions of soil increases with time over the life of the stand. The
next ten to twenty years will be the true test of this natural vegetation to
see whether the roots do penetrate the refuse or if the refuse acts as a
barrier and prevents penetration. The result may then be an edaphic climax
or a constant shifting of types until no gas exists in the soil. Roots often
have the habit when possible, to circumvent a barrier and send roots to areas
more favorable, as shown by Stout (lU5). One Virginia pine in particular,
found growing on the landfill was checked for the presence of mycorrhizal
fungi after a basidiocarp was found adjacent to it. The fungus was not
identified, but the pattern of the tree roots was striking. A lateral root
from the sapling grew out of the north side of the tree and swung clockwise
around the tree until it found a path to a better soil condition marked by
increased vegetation. On the eastern and western sides of the tree, areas
of gas upwelling were found. A second pine in a similar situation had very
poor form and vigor, and a check of the roots showed an absence of
mycorrhizal fungi and a compact root system.
Final Evaluation—
Vegetation succession on the landfill is still in the very early stages
of tree growth (9> 100). Patterns are not occurring too far out of sequence
even though the number of trees may be high for the age of abandonment
(eleven years). A study of the patterns of root growth of these trees could
be quite useful in understanding the problems that occur in establishing
plantings on landfills. Coupled with these observations mycorrhizal fungi
could be evaluated for their help in relieving vegetation stresses that occur
here. Table 1 summarizes the main species found on the Edgeboro Landfill
site and adjacent island.
TABLE 1. TREE DISTRIBUTION AND DENSITY - EDGEBORO LANDFILL AND ISLAND
Species
Number Found On Landfill
North Section South Section
Also Present In
Woodlot Test Plot
Acer rubrum
Acer negundo
Ailanthus altissima
Betula populifolia
Fraxinus pennsylvanica
Gleditsia triacanthos
Hamamelis virginiana
Juniperus virginiana
Liquidambar styraciflua
Malus spp.
Myrica pensylvanica
Nyssa sylvatica
Pinus echinata
Populus deltoides
15
1
17
7
3
0
0
3
3
3
ho
16
9
1
3
2
2
3
19
2
1
9
o
I*
115
1
1
o
X
X
X
X
X
X
X
X
X
X
X
Genus
n
(continued)
25
-------
TABLE 1. (continued)
Number Found On Landfill Also Present In
Species North Section South Section Woodlot Test Plot
Populus tremuloides 0 IX Genus
Prunus serotina 86 30 X
Quercus palustris k 0 X X
Rhus glabra 3^0 282 X
Robinia pseudoacacia 5 0 X -
Rosa spp. 38 16 X -
Sassafras albidium 3 3 X -
Vaccinium corymbosa 18 19 X -
Viburnum prunifolium 38 5 X -
Total Area
Woodlot = U63,150 square feet = 10.63 acres
Landfill = U42,700 square feet = 10.16 acres
X = presence
= not found
Genus = different species of same genus found
Site Conditions
The refuse in the Edgeboro landfill ranges in depth from 20 to 35 feet
and consists primarily of municipal refuse plus some light industrial waste.
The areas on the landfill where these data were collected were completed
between 1966 and 1969. There is a foot or less of final soil cover over the
refuse. No attempts have been made to vegetate this landfill; therefore, all
vegetation observed growing on it consists of volunteer native species.
Ten permanent stations were established on the landfill where vegetation
was either growing very well or not at all (Figures 3 and U, Table 2).
Acrylic gas sampling devices (Figure 5) designed to enable extraction of a
micro-sample of the soil atmosphere for gas chromatographic analysis were
buried at a depth of 10 inches at each of these stations.
The depth of cover material at the permanent stations was determined by
digging five holes with a spade. Each approximately 18-inch diameter hole
was dug until the refuse was reached. Then a yardstick resting on undis-
turbed soil was placed across the top of the hole. A second yardstick was
used to measure the distance from the top of the cover. This distance was
recorded as the depth of cover.
The soil atmosphere was analyzed by two methods, one utilizing a macro-
sample, one a microsample:
1) The macrosample was obtained by means of the MSA model 2A Explosi-
meter and Fyrite Og and C02 analyzers. The 02, and C02? and
combustible gas readings were all taken from separate holes within 1 foot of
26
-------
each other when taken at the same station.
2) A microsample was obtained by first extracting a 5 ml. gas sample
through the sampling device (Figure 5) with a syringe and discarding it.
After extracting this volume, the tygon tubing was pinched to prevent a back
flow of ambient air. A 0.5 ml. sample was then extracted through the
sampling device with a gas-tight syringe and the sample sealed in the syringe
by inserting the needle into a rubber stopper. The sample was then analyzed
in a Carle model 8500 gas chromatograph equipped with a porpack Q and molec-
ular sieve column system and a thermal conductivity detector.
The gas chromatograph was calibrated with standard gas concentrations
supplied by Matheson Gas Products of East Rutherford, New Jersey. A flow of
gas was established through a soft rubber tube, one end of which was attached
to the regulator on the standard gas cylinder and the other end immersed in
water to prevent a back flow of ambient air. A gas-tight syringe was then
used to extract a 0.5 ml. sample through the tubing and inject it into the
chromatograph. The recorder attached to the chromatograph was equipped with
an intergration unit which translates the area under the gas peaks into
standard units which were then plotted against the known concentrations of
the gas to produce standard curves. The calibration procedure was performed
once a month. Once a week a standard gas concentration was passed through
the chromatograph to insure accuracy of the calibration curves.
TABLE 2. DESCRIPTION OF PERMANENT STATIONS ON THE
COMPLETED SANITARY LANDFILL
Station Description
A. Oval area approximately 50 feet long by 38 feet wide. No vegeta-
tion growing in this area.
B. Kidney shaped area about 500 feet long by 25 feet wide. Very
little vegetation-only a few scattered clumps of brome grass
covering less than 5$ of the surface area.
C. Circular area approximately 25 feet in diameter. At the center
was a pin oak tree 15 feet high with a DBH of 8 cm. Moss was
observed growing under the oak and brome grass grew all around it.
The vegetation in this area provided 100$ cover.
D. Round clump of staghorn sumac about 15 feet in diameter. The
sumac was about 6 feet high at the center. It appeared healthy,
exhibiting good growth this season. Also in this area was a 10
foot high sweet gum tree with a DBH of 4.5 cm. It also exhibited
good growth this season. The soil in this area tended to be very
wet.
E. Oval area approximately 20 feet long by 10 feet wide. Brome grass
was growing in this area in sparse clumps providing about 25$
(continued)
27
-------
TABLE 2. (continued)
Station Description
cover. This -was the only poorly vegetated station where vegeta-
tion appeared to be increasing its percent coverage during the
course of this study.
F. Irregularly shaped 10 feet diameter group of staghorn sumac and
peach trees. The sumac vas 4.5 feet tall. It did not exhibit
good growth this year. There were two peach trees, one about
k feet high and one 6 feet high, which appeared healthy. The
larger exhibited a good production of fruit in 1977.
G. Round area about 25 feet in diameter. No vegetation was observed
growing here.
H. Round area about 25 feet in diameter. There was a good cover of
brome grass and weeds in this area, providing close to 100$ cover.
I. Round area about 15 feet in diameter. A small group of peach
trees about 6 feet high. These trees exhibited poor growth this
year. There was also a 6-foot-tall crab apple tree with a DBH of
h cm. that appeared healthy and grew well this year. There was a
considerable amount of refuse on the surface in this area. News-
papers found in the refuse were dated January, 1969.
J. Oval area approximately 18 feet long by 10 feet wide. The vegeta-
tion in this area provided less than 5$ cover. It consisted of
a few scattered clumps of brome grass and one chlorotic staghorn
sumac 10 inches high. There was a considerable amount of refuse
on the surface in this area. A newspaper found in the refuse was
dated November, 1968.
K. Irregular area approximately 15 feet in diameter. There was a
healthy stand of peach trees here about 7 feet tall which grew
very well in 1977.
Preparing The Experimental And Control Field Plots
Two field experiments were designed; one to screen tree species for
adaptability to landfill conditions and the second to test gas-barrier sys-
tems for effectiveness in preventing contamination of root zones by landfill
gases.
Species Screening Experiment—
One foot of sandy subsoil was spread over the entire experimental screen-
ing area followed by 8-10 inches of topsoil. Because there were two or three
inches of original soil cover over the refuse prior to construction, this
brought the total cover to approximately 2 feet.
28
-------
ru
\o
To Edgeboro Road
Power Plant
Not drawn to scale
Figure 3. Edgeboro Sanitary Landfill, East Brunswick, New Jersey,
location of reference stations for gas and vegetation sampling points.
-------
K
Fran
A
A
A
P
P
P
P
P
P
P
To
B
C
D
E
F
G
H
I
J
K
Dist.
(in feet)
180
235
265
kO
k2
157
220
25
37
7
An0
22
320
299
26
11*0
312
315
3^3
186
303
Figure h. Gas and vegetation sampling points on Edgeboro Sanitary Landfill.
30
-------
Septum
3/32" O.D. X 1/32" I. D.
Tygon Tubing
U
Plastic Cement
3/8" O.D. X 3/16" i.D.
Plastic Tubing
-1/2" O.D. X 3/8" I.D.
Plastic Tubing
' Wire Screen
Figure 5. Plastic soil gas sampler.
31
-------
Following removal of the native vegetation, one foot of the same sandy
subsoil spread on the experimental landfill plot was deposited on top of the
control area. Eight to twelve inches of topsoil were then placed on top of
the subsoil. The topsoil layer was about 2 inches deeper here than in the
experimental plot. This was due to the need for extra soil to fill in the
tracks created by the large tractor used to level the area.
Combustible gas readings were taken by means of the MSA Model 2A
Explosimeter over much of the site at 50 foot intervals until a large enough
area with high combustible gas concentrations was found.
The experimental plot measures 72'x!08', an area large enough to accom-
modate ten replicates of nineteen different tree and shrub species and five
landfill gas-barrier systems (Figure 6). The control is located approximately
a quarter-mile from the experimental plot and is on a former undisturbed
woodland. It measures ^6'xllO1 and accommodates ten replicates of the same
nineteen species planted on the experimental plot, in addition to two gas-
barrier systems (Figure 7).
The experimental landfill plot is exposed to strong winds and driving
rains, as is typical of many of the larger landfills. The control plot,
located on the north side of an adjacent wooded rise, is only moderately
exposed on the south and southwest where native woodlands remain. These
native woods comprise sassafras, red oak, mockernut hickory, red maple and
dogwood, species typical of a young forest community which normally follows
20-30 years after a disturbance such as a fire or clear cut.
Drainage on both the experimental and control plots is good and should
not be a limiting factor for tree growth.
Gas-Barrier Techniques--
Following the designation of the experimental plot, the precise bound-
aries for three lO'xlV trenches and two lVxl8f mounds were determined by
selecting the areas of highest combustible gas concentration in the soil
atmosphere. A caterpillar tractor bulldozer was used to dig the three 3
foot deep trenches and to move the excavated rubbish from the experimental
site.
In order to prevent landfill decomposition gases from penetrating the
soil, the three trenches were lined at the bottom with various barrier
materials prior to backfilling with topsoil. One of the two mounds was
underlain with a barrier whereas no barrier was used in the second mound.
Plastic/gravel/vents trench—This trench (Figure 8) was lined with a
one-foot layer of 1 inch round road gravel which was deposited on the trench
bottom by means of a front-end loader and spread out evenly with a hand rake.
Two plastic gas samplers were buried in the gravel to permit the analysis of
accumulated gas. Ten holes were then dug in the gravel around the periphery
of the trench into which were placed ten 5-foot long, U-inch diameter per-
forated polyvinyl chloride pipes. The perforations are \ inch in diameter
and are orientated at 90° angles at 6 inch intervals. A l6'x!2' sheet of
k mil polyethylene plastic was cut to fit over the PVC pipes and placed on
32
-------
•191
•182 Trench- Clay,
•173 ,o, '19° Vents
.17? '181 -189 -2U1
Trench-Clay ^ ' 1*> .,33 '219^218
16U
163
162
l6l
160
159
158
157
156
155
151+
153
152
151
150
149
ll+8
ll+7
i
/
.11+6
.11+5 '
•237 .170 >179 -187 -220
21? . ?1 ? ' 178 „ , . ?
" ^-^t— _ r r\ . T Q^L ^
00/- -Io9 loo -,.
•c:jD . ,„„ -221
• 217
!39
• 2l6
.11+1+ . 21]+ .211 l6Q -^"^-^ .238
.11+3 >
.11+2
.11+1
• ll+O
.139
.138
.137
• 136
•135
• 131+
• 133
- 132
• 131
• 130
• 129
/
f
•235 .,_ ' -"-fo .i8U
215 -210 lt>7 • 175 -«,
•23U -166 i^'183
•165
Mound-No
day Mound- Clay
• 233 ' 229
•206 ' 207 '200 -201
• 232 • 228
• 205 ' 208 • 199 -202
• 231 * 227
• 201+ • 209 ' 198 -203
•230
Trench-Gravel,
Plastic, Vents
•19l+ -193 ' 192
•225-221+ -223-222
•195-196 -197
• 128-127 -126 -125 -121+ -123 -122 -121 -120
•118 -117 -116 -115 -111+ -113-112 -111
•109 -108 -107 -106 -105 -101+ -103 -102
•100- 99- 98- 97- 96- 95- 9!+- 93
• 91 • 90 • 89 • 88 • 87 • 86 • 85 • 81+
• 82- 81- 80- 79- 78- 77- 76- 75
•73
•72
•71
•70
•69
•68
•67
•66
•65
- -61+
•63
•62
•61
•119 -60
•no -59
•101 -58
• 92-57
• 83 -56
• 71+-55
'53
•52
•51
•50
.1+9
•1+8
•1+7
•1+6
•1+5
•1+1+
•k3
•1+2
•1+1
•1+0
•39
•38
•37
•36
•35
• 3k
•33
•32
•31
• 30
•29
• 28
•27
•26
•25
•21+
•23
•22
•21
•20
•19
•18
•17
•16
•15
•ll+
•13
•12
•11
•10
• 9
• 8
• 7
• 6
• 5
• 1+
• 3
• 2
• 1
Legend: Numbers identify specific trees
Trees spaced 4' apart
Figure 6. Location of trees on species screening area and gas-
barrier techniques on experimental plot.
33
-------
Mound
.210
.202 -199
.209
.201 -198
.208
•200 -197
.207
Trench
•206
.194 J-93
•205
.195 -192
•204
.196 .191
•203
\
\
\
-190
.189
.188
.187
.186
.185
• 184
-183
.182
•181
•180
•179
•178
• 177
•176
•175
. 174
• 173
. 172
• 171
. 170
. 169
. 168
. 167
. 166
. 165
. 164
. 163
. 162
. l6l
. 160
• 159
. 158
• 157
. 156
- 155
. 154
• 153
• 152
• 151
•150
•149
•148
•147
•146
•145
•144
•143
• 142
-l4l
• l4o
• 139
• 138
• 137
• 136
• 135
•134
• 133
• 132
• 131
• 130
• 129
• 128
• 127
• 126
•125
•124
•123
•122
•121
•120
•119
•118
•117
•116
•115
• 114
• 113
• 112
• 111
• 110
• 109
• 108
. 107
• 106
. 105
• 104
- 103
• 102
• 101
•100
• 99
• 98
• 97
• 96
• 95
• 94
• 93
• 92
• 91
• 90
• 89
• 88
• 87
• 86
• 85
• 84
• 83
. 82
• 81
• 80
• 79
• 78
• 77
- 76
•75
•74
•73
•72
•71
•70
-69
. 68
.67
. 66
•65
. 64
• 63
• 62
. 61
. 60
• 59
• 58
• 57
- 56
• 55
• 54
• 53
• 52
• 51
• 50
•49
• 48
•47
• 46
•45
• 44
•43
.42
•41
. 40
•39
•38
• 37
•36
• 35
• 34
• 33
• 32
• 31
• 30
• 29
• 28
• 27
. 26
• 25
• 24
•23
• 22
• 21
• 20
• 19
• 18
• 17
• 16
• 15
• 14
• 13
• 12
• 11
• 10
• 9
• 8
• 7
- 6
• 5
• 4
• 3
• 2
• 1
Legend: Numbers identify specific trees
Trees spaced 4' apart
Figure 7. Location of trees on species screening area and gas-
barrier techniques on control plot.
-------
Plan View
10'
0
c
0
o
o
5 C
o
o
o
o
;>
o
Q
O
c/
Q
O
O
s
o
(Vi^
^V '
o
•American
Basswood
Japanese Yew
V PVC Vertical Vents
End View
Japanese Yew
American Basswood
30'
Refuse '
•
•
•
•
•
I \ 1 f
• -^ o -A-
3' Topsoil
1' 1" Road Gravel
•
•
•
•
•
' 10" Topsoil
' 12" Subsoil
Plastic Sheeting
.10'
.U" PVC Vents
Figure 8. Design of gravel/plastic/vents trench.
35
-------
top of the road gravel. Presumably this made a seal through which no decom-
position gas could migrate. It was expected that the gas collected under the
plastic sheeting would be carried to the soil surface via the perforated
pipes, thereby bypassing the 3-feet of topsoil backfilled into the trench.
The tops of the ten perforated pipes extend approximately 1 foot above the
soil surface.
Clay/vents trench—This trench (Figure 9) was lined at the bottom with
a one-foot layer of clay similar to that used in California to exclude de-
composition gases. The clay was obtained from virgin land about one-half
mile away and brought to the site via a large earthscraper tractor. A
front-end loader was then used to deposit the clay on the trench bottom.
Some of the clay was friable and could be easily spread by hand shovel;
however, a large portion of it had to be broken into smaller pieces to allow
for better compaction. After the clay was adequately spread, it was packed
down tightly by foot. Ten ventilation pipes, similar to those used in Figure
8, were placed vertically around the periphery of the clay bed, hopefully,
to remove the gases of landfill decomposition prior to their entering the
trench. Finally the trench was filled with 3-feet of topsoil.
Clay/no vents trench—This trench (Figure 10) was lined at the bottom
with a foot-thick clay layer as was the previous trench. However, this
trench has no perforated pipes for venting landfill gas. After the clay was
spread and compacted, 3-feet of topsoil were backfilled into the trench.
Two experimental mounds were also constructed for preventing gas migra-
tion.
No clay mound—This mound (Figure 11) was constructed of the same qual-
ity topsoil as that used in the trenches. The final mound dimensions were
lVxl8' at the base, 8'xl2' at the top, and 3' in height with h^° sloping
sides.
Clay barrier mound—To keep the landfill gases out of the root zone,
this mound (Figure 12) (same dimensions as the previous mound) was under-
lain with a one-foot layer of the same type clay as used in trench-clay/vents
and trench-clay. The clay base below the mound has an overall dimension of
l6'x20' thereby extending one foot beyond the base of the mound.
The control plot contained one trench and one mound constructed to the
same dimensions as those on the experimental plot with topsoil similar to
that used on the experimental plot. No gas barriers or vents are associated
with the trench or mound in the control plot.
Selection of Experimental Species
In order to test species representative of a maximum number of desirable
landscaping characteristics and a variety of genotypes, plants were chosen
from the following categories: deciduous shrubs, deciduous trees, needle-leaf
evergreens and a broad-leaf evergreen. Within these categories, species were
selected for: 1) tolerance to low oxygen tension environments; 2) tolerance
to city conditions; 3) aesthetic landscaping purposes; k) ubiquity; 5)
36
-------
Plan View.
10'
3
0
O
o
O O
O
o
o
o
o
Q
O
cT
o
o
o
o
r^ <
{J <
o
•American
Basswood
•Japanese Yew
V PVC Vertical Vents
14'
End View
Japanese Yew
American Basswood
30' <
Refuse <
»
-<3
>
1 \ /
-^ O ^
3' Topsoil
lf Clay
10' . .
r*=
\
^
10" Topsoil
12" Subsoil
\ k" PVC
Figure 9. Design of clay/vents trench.
37
-------
Plan View
10'
O O
O O O O
O O O
American
Bassvood
Japanese Yew
End View
Japanese Yew
American Basswood
30'
Refuse
i
"\
i
\ *—
10" Topsoil
12" Subsoil
Figure 10. Design of clay/no vents trench.
38
-------
Plan View
\ /'
O O O
G> ©
O
y-^
G>
0 0
1
12'
k
i ,
8' 1
-
\
IS1
Japanese Yew 20' American Basswood
End View
O
Topsoil
F
31
i
.' Topsoil
F
Subsoil
30'
Refuse
Figure 11. Design of no clay-barrier mound.
39
-------
Plan View
20'
Japanese Yew American Basswood
End View
o
Topsoil
\
o o o
o
o o o
0 0
^
/ '
'
o
8'
'
\
J
1
v
16'
1' Clay
I1 Subsoil
30'
Refuse
£ Topsc
Topsoil
Figure 12. Design of clay-barrier mound.
1*0
-------
susceptibility to natural and landfill gas injury; 6) tolerance to sea salt;
7) ease in transplanting; 8) minimal costs (Table 3).
Nineteen species (Table U) were selected according to the above eight
criteria. American basswood and Japanese yew were chosen for planting on the
trenches and mounds because of their reported susceptibility to landfill
gases. All species chosen for the experiment were judged to be relatively
easily transplanted and obtainable at local commercial nurseries at a rea-
sonable cost.
Planting of Trees and Shrubs
The trees were spaced at k foot intervals to allow for several years of
growth uninhibited by adjacent trees. For random placement of the trees,
points were marked in rows on the plot to accommodate all the trees. These
points were assigned numbers in consecutive order on both plots from 1 to 210
and 1 to 2^0 (Tables 5a & 5b) (Figures 6 & 7) for the control plot and ex-
perimental plot respectively. For each species, ten of these numbers were
selected from a random numbers table, and the ten replicates were planted in
locations bearing these numbers on the dates shown in Table 6.
The planting holes were dug by means of a pick and shovel. Those for
bare-rooted trees were dug deep enough to accommodate the vertical expanse
of the root system and 3 to 6 inches wider than the lateral expanse. The
balled and burlapped trees and the trees in containers were planted in holes
as deep as the root ball or container and about 12 inches wider in diameter.
The holes extended down into the sandy subsoil in the majority of cases.
As the trees were placed in the holes, the topsoil was backfilled to
three-fourths of the original hole depth. The soil was packed firmly by
foot and watered. When the water had been absorbed, the remainder of the
hole was filled with topsoil and loosely packed by hand. A 2-inch ridge was
constructed around each tree to act as a catch-basin.
Because of the loss of roots when the trees were dug at the nursery,
the bare-rooted trees required branch pruning. This was done after the trees
had been planted. Thirty to fifty percent of most of the viable branches
was removed as well as all dead tissue.
The large deciduous trees were staked in order to stabilize them in the
soil and prevent windthrow. Two 2"x2"x6' Douglas fir stakes were driven into
the soil on either side of each tree perpendicular to the direction of the
strongest prevailing winds. Plastic chain-lock was used to secure the tree
between the two stakes.
Cultural Methods
Fertilizing—
In 1976, soil nutrient analyses for both the experimental and control
plots indicated low nitrogen, phosphorus and potassium levels. In order to
bring these nutrients to a medium level in the soil, on April 16-17, 1977,
four pounds of 10:10:10 granular fertilizer were spread around each tree on
-------
TABLE 3. TREE PLANTING SELECTION CRITERIA
ro
Trees Tolerance to Ubiquity Aesthetic Sea Salt Tolerance Susceptibility
Low C>2 Tension Landscaping Tolerance to City to Landfill
Environments Purposes Conditions Gases
CO
H
IH
CO
8
8
M
O
Q
CO
ED co
HJ— • J
t-*
O K
W PI
Honey Locust
American Sycamore X
Red Maple X
Green Ash X
Black Gum X
Black Willow X
Pin Oak X
Ginkgo
Sweet Gum
American Basswood
Hybrid Poplar
Mixed Hybrid Poplar
Euonymus
Bayberry X
X
X X
X X
X
X
X
X
X X
X
X X
X
X
X
X
CO
Rhododendron
PQ H CO
CO
White Pine
Japanese Black Pine
Norway Spruce
Japanese Yew
X
X
X
X
X
-------
TABLE k. SPECIES SELECTED FOR VEGETATION GROWTH EXPERIMENT
AT EDGEBORO LANDFILL
Abbreviation Latin Name
Common Name
Selection
Criteria*
Ar Acer rubrum
Ea Euonymus alatus
Fl Fraxinus lanceolata
G Ginkgo
Gt Gleditsia triacanthos
Ls Liquidambar styraciflua
Mp Myrica pensylvanica
Ns Nyssa sylvatica
P Populus
Pe Picea excelsa
Pm Populus m
Po Plantanus occidentalis
Ps Pinus strobus
Pt Pinus thuribergi
Qp Quercus palustris
R Rhododendron Roseum elegans
Sb Salix babylonica
Ta Tilia americana
Tec Taxus cuspidata capitata
Red Maple 1,2,3
Euonymus 3
Green Ash 1,3
Ginkgo 3,5
Honey Locust 1,3
Sweet Gum 3
Bayberry 1,3
Black Gum 1,3
Poplar (Hybrid) 3
Norway Spruce 3
Poplar (Mixed Hybrid) 3
American Sycamore 1,3,5
White Pine 3
Black Pine 3,^
Pin Oak 1,3
Rhododendron 3
Weeping Willow 1,3
American Basswood 3>6
Japanese Yew 3,6
Selection Criteria
1. Tolerant of low 0_ environments
2. Ubiquity
3. Aesthetic landscaping purposes
k. Sea salt tolerance
5. Tolerant to city conditions
6. Susceptibility to landfill gases
-------
TABLE 5a. PLANT KEY FOR EDGEBORO LANDFILL TREE GROWING
EXPERIMENT FOR THE CONTROL PLOT
Tree Latin
Number Abbreviation
1 -
2 -
3 -
5 -
6 -
7 -
8 -
9 -
10 -
11 -
12 -
13 -
11* -
15 -
16 -
17 -
18 -
19 -
20 -
21 -
22 -
23 -
2U -
25 -
26 -
27 -
28 -
29 -
30 -
31 -
32 -
33 -
35 -
36 -
37 -
38 -
Ea
Tec
Fl
Ta
Fl
. Ea
Po
Qp
Tec
Po
Ar
P
G
Ps
Po
P
Ls
Tec
Ta
Qp
Mp
Sb
Fl
Ls
Pe
Ns
Sb
G
Pt
R
Ps
G
Qp
Mp
Sb
Ea
Ar
Sb
39
1*0
1*1
1*2
1*3
1*1*
1*5
1*6
1*7
1*8
1*9
50
51
52
53
55
56
57
58
59
60
61
62
63
61*
65
66
67
68
69
70
71
72
73
75
76
- Ls
- Pm
- Ar
- Pm
- P
- Pe
- P
- Ps
- Ns
- Pm
- R
- Ph
- Ta
- Gt
- Ls
- Tec
- Sb
- Mp
- Pm
- Ta
- Po
- Pt
- G
- Qp
- Ns
- Gt
- Gt
- Pm
- Ps
- Po
- Pt
- Ro
- Po
- Ar
- Ls
- Fl
- R
- Ns
77
78
79
80
81
82
83
81*
85
86
87
88
89
90
91
92
93
9!*
95
96
97
98
99
100
101
102
103
ioi*
105
106
107
108
109
110
111
112
113
111*
- Qp
- Sb
- Tec
- Pe
- QP
- Pm
- Tec
- Gt
- Fl
- Ta
- R
- Ps
- Pe
- Sb
- Ns
- Sb
- Ps
- Ea
- Gt
- R
- Tec
- Ar
- Ta
- Pe
- Ph
- Ls
- G
- Ar
- Ns
-. Pt
- Ps
- Sb
- Pt
- Pe
- Pt
- Pm
- Mp
- Po
115
116
117
118
119
120
121
122
123
12l*
125
126
127
128
129
130
131
132
133
131*
135
136
137
138
139
ll*0
1*4-1
1 ]i g
ll*3
11*1*
11*5
ll*6
ll*7
ll*8
ll*9
150
151
152
•
- Ea
- R
- Ar
- G
- Ls
- Mp
- Pm
- Ar
- Ls
- Qp
- Ea
- Ea
- Ps
- Pt
- Fl
- QP
- Ps
- Gt
- Ta
- Ea
- Ph
- Mp
- Ns
- Pe
- Fl
- G
- Tec
- Po
- Qp
- Ph
- R
- Po
- Ar
- R
- Po
- G
- Gt
- Ph
153
151*
155
156
157
158
159
160
161
162
163
161*
165
166
167
168
169
170
171
172
173
171*
175
176
177
178
179
180
181
182
183
181*
185
186
187
188
189
190
191
203
- Sb
- R
- G
- Ea
- Fl
- Gt
- Fl
- Ar
- Mp
- Ns
- Ph
- Gt
- Pe
- Ea
- Fl
- Gt
- Ta
- Pm
- G
- Qp
- Ls
- Pm
- Pt
- Pe
- Tec
- Ls
- Ps
- Pe
- Ta
- Mp
- Mp
- Pt
- Ta
- Mp
- Pt
- Ns
- Ns
- Tec
- 202 - Ta
- 210 - Tec
* See Table U for key to abbreviations
1*1*
-------
TABLE 5b. PLANT KEY FOR EDGEBORO LANDFILL TREE GROWING
EXPERIMENT FOR EXPERIMENTAL PLOT
Tree Latin
Number Abbreviation
1 -
2 -
3 -
4 -
5 -
6 -
7 -
8 -
9 -
10 -
11 -
12 -
13 -
i
Ik -
15 -
16 -
17 -
18 -
19 -
20 -
21 -
22 -
23 -
24 -
25 -
26 -
27 -
28 -
29 -
30 -
31 -
32 -
33 -
i
3k -
35 -
36 -
37 -
38 -
Pm
Tec
Po
Ta
Po
Ea
Fl
Qp
Ea
Fl
Ar
P
G
Ps
Fl
Fl
Ls
P
Ta
Qp
Mp
Tec
Po
Ls
Pe
Ns
Ta
Sb
G
Pt
R
Ps
G
Qp
Mp
Tec
Pe
Ns
39 -
40 -
*a -
42 -
*3 -
44 -
45 -
46 -
U7-
48 -
k9-
50 -
51 -
52 -
53 -
54 -
55 -
56 -
5Z -
58 -
59 -
60 -
6l -
62 -
63 -
64 -
65 -
66 -
67-
68 -
69-
70 -
71 -
72 -
73 -
74 -
75 -
76 -
Ls
Sb
Pm
Ea
Pm
P
Pe
P
Ps
Ns
R
Ta
P
Ta
Gt
Mp
Ls
Ar
Ps
Mp
Pm
Ta
Fl
Pt
G
Qp
Ar
Gt
Gt
Pm
Ar
Tec
R
Fl
Pt
Ls
Tec
R
77 - Ns
78 - Qp
79 - Ta
80 - Sb
81 - Pe
82 - Qp
83 - Pm
84 - PO
85 - Gt
86 - Po
87 - Ta
88 - R
89 - Mp
90 - Pe
91 - Sb
92 - Ar
93 - Pt
94 - Ps
95 - Sb
96 - Mp
97 - R
98 - Ps
99 - Ar
100 - Ea
101 - Pe
102 - P
103 - Ls
104 - G
105 - Ar
106 - Ns
107 - Pt
108 - R
109 - Sb
110 - Ea
111 - Pe
112 - Mp
113 - Pm
114 - Qp
115 - Fl
116 - NS
117 - Ps
118 - Ar
119 - Ls
120 - G
121 - Gt
122 - Ea
123 - Pt
124 - Ls
125 - Tec
126 - Ea
127 - Sb
128 - Ps
129 - Pt
130 - Po
131 - Qp
132 - Ps
133 - Gt
134 - Ta
135 - Tec
136 - P
137 - Mp
138 - Ns
139 - Pe
140 - Fl
l4l - G
142 - Pm
143 - Po
144 - Qp
145 - Ea
146 - Mp
147 - P
148 - R
149 - Fl
150 - Ar
151 - R
152 - Fl
153 - G
154 - Gt
155 - P
156 - Sb
157 - G
158 - Sb
159 - Tec
160 - Po
161 - Gt
162 - Ea
163 - Po
164 - Pt
165 - Ar
166 - pt
167 - NS
168 - Po
169 - Gt
170 - P
171- - Tec
172 - Ns
173 - Ea
174 - Pe
175 - Gt
176 - Ta
177 - Pm
178 - G
179 - Qp
180 - Ls
181 - Pt
182 - Mp
183 - Pm
184 - Pt
185 - Tec
186 - R
187 - Sb
188 - PS
189 - Pe
190 - Ls
191 - Ns
192 - 221 - Ta
222 - 241 - Tec
* See Table 4 for key to abbreviations
45
-------
TABLE 6. TREE AND SHRUB PLANTING DATA
Dates of Planting
Screening Experiment
Honey locust (a)*
American sycamore (a)
Red maple (a)
Green ash (a)
Black gum (c)
Weeping willow (a)
Norway spruce (b)
White pine (b)
Euonymus (b)
Bayberry (b)
Pin oak (a)
Rhododendron (c)
Ginkgo (a)
Japanese black pine (b)
Japanese yew (b)
Sweet gum (c)
American basswood (a)
Hybrid poplar (a)
Mixed hybrid poplar (a)
Barrier System Experiment
Basswood - trenches
Basswood - mounds
Yew - trenches
Yew - mounds
* Shipping Method:
(a) Bare- rooted
(b) Balled and bur lapped
(c) Containerized
Site A
(Control Plot)
It- 22- ?6
4-27-76
4- 22- 76
4-22-76
4-15-76
4.27-76
4-14-76
4-15-76
4-27-76
4-10-76
4-27-76
4-15-76
4-22-76
4-10-76
4-27-76
4-26-76
4-22-76
4-6-76
4-15-76
4-23-76
4-23-76
6-10-76
6-10-76
Site B
(Experimental)
Plot
4-4-76
4-6-76
4-4-76
4-6-76
4-9-76
4-15-76
4-8-76
4-8-76
4-27-76
4-9-76
4-4-76
4-6-76
4-4-76
4-8-76
4-8-76
4-26-76
4-23-76
4-3-76
4-3-76
4-23-76
4-23-76
6-10-76
6-10-76
Approximate
Tree Height at Planting
7'-8«
10 '-12'
6'-8'
10' -12'
3'-4'
14--15'
18" -24"
l8"-24"
15"-l8"
12"-15"
6'-8'
12"-18"
5'-6'
l8"-24"
l8"-24"
3'-4f
7'-8'
9'-10'
I1
7'-8'
7f-8'
l8"-24"
l8"-24"
(8" cans)
(6" cans)
(8" cans)
-------
both plots for a total of 840 pounds with a standard granular fertilizer-
spreader.
Liming--
1Q77 Bo*h P1^8 were lined with pulverized dolcmitic-limestone on April 18,
1977. In order to raise the PH to 6.5, forty-six Ibs./lOOO square feet were
applied to the control plot and fifty- seven Ibs./lOOO square ?eet to the
experimental plot by means of a standard walk-behind spreader.
Irrigation —
The rainfall in New Brunswick in the early spring of 1976 and 1977 was
6n^?H *v Tint^n the S0il at a m°isture level sufficient for Sequatl See
growth but by the middle of May in both years, the soil moisture* had
reached a low enough level to warrant irrigation. During the summer of 1976
a one-horsepower irrigation pump with a 3/k inch outlet hose was used to
allocate water to each tree. The water was pumped from a series of fou?
55-gallon drums located in the back of a pick-up truck. Approximately^hree
gallons were applied to each tree at each irrigation period at Trate of
SLf HhOUr; • ^H ^^ °f irri^ion ™ quite tSlcIn^ and pro-
vaded only a limited amount of water for each tree.
A 200anueiv °f irri8ation ™ **de available.
A 2000-gallon fuel- oil truck was converted into a water- supply truck by the
Herbert Sand and Gravel Company and arrangements were made to utiSze this
truck for irrigating the trees. Approximately ten gallons were Jo! applied
to each tree at each watering at a rate of 2obo galf/hour? Sen Se wS
rainfall was inadequate, the plots were irrigated on the weekend by this
morefficient method which allocated more wlter/tree in rSSSe^peSo
Pest Control —
the
8' 1976 for the
On May 6, 1977, the following tree species were
Sevin for the control of tent caterplUar?
the
*Soil moisture was tested by the squeeze method, i.e. when a handful of
soil was squeezed and water dripped from the soil, it was classified as wet;
when no water came out but the soil stayed together in a clump the soil was
moist; and when the soil crumbled after squeezing, the soil was considered
dry and the plants were irrigated.
-------
Rodent Control—
On December 29, 1977? a -| inch mesh screen supported by three stakes was
placed around each euonymus shrub to prevent damage by rabbits.
Plot Maintenance—
During the growing season, grass and weeds were periodically cut with a
power mower and weeds were pulled from the area immediately surrounding each
tree trunk. Tree support-stakes were driven back into the ground when loos-
ened and the plastic chain-lock supporting trees between stakes was replaced
when necessary.
Sampling Methods
Soil Gas Analyses—
During the summer of 1976, combustible gas was measured in situ by means
of a Mine Safety Appliance Model 2A Explosimeter. A \ inch hole was punched
in the soil to the desired depth by means of a commercial bar-hole maker.
The sample was withdrawn from the bar-hole by use of a 3-foot long nonspark-
ing probe. A rubber stopper was placed over the upper end of the sampling
probe to help seal the bar-hole from the ambient air. The Wheatstone bridge
principle is used within the instrument for determining the concentration of
combustible gases.
Gas data were taken at a 1-foot soil depth from eleven collection points
on the experimental plot and eight points on the control plot on 7/7/76 and
9/13/76. Gas data were also collected from the trenches and mounds of the
gas-barrier technique experiments on these same dates. Measurements were
made at the 1-foot soil depth at six points within each gas-barrier technique
and at four or six points around the periphery of the trenches, as well as
within the vent pipes.
During 1977, gas samples were collected from forty-eight buried samplers
approximately every two weeks, beginning in March and ending in August, when
a-11 plants had ceased growing. Forty-two of the sampling stations were on
the experimental plot (Figure 13) and six on the control plot (Figure lU).
The device in Figure 5 was used for obtaining the soil gas samples. In the
experimental screening area, one sampler is in place for each group of six
plants, whereas in the trenches and mounds, there is a sample for each group
of five plants.
Soil Temperature Analyses—
Soil temperatures at the 1-foot depth were collected at the same sample
points (Figure 13 & 1*0 and on the same dates as the gas samples.
Soil Moisture Analyses—
Beginning in mid-March, 1977 3 soil moisture measurements were made on
six samples from the experimental screening area and four from the control
(Figures 13 & 1*0 • One measurement was made in each of the gas-barrier
techniques. Samples were collected at approximately two-week intervals at
times when the moisture content was considered to be the lowest, i.e. before
irrigation or before a rain was expected. A sample was obtained using a
3-inch diameter soil auger in the following manner: two 8-inch deep holes
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Legend:
. Trees
O Gas Sample Points
% Nutrient Sample Points
© Moisture Sample Points
Figure 13. Location of soil variable sampling stations
on experimental landfill plot.
-------
©
o
©
o
0 •
i .
o •
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o
•
O
•
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0
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Legend:
• Trees
O Gas Sample Points
• Nutrient Sample Points
© Moisture Sample Points
Figure lU. Location of soil variable sampling stations on control plot.
50
-------
were dug in the same general area and the soil from these two holes was
?hean1med ^th'SL^f *?+** * *"*' A k°° *• metal "JSiS
then filled with this soil mixture and capped to retain all the moisture
Soil Nutrient Element Analysis—
S
Soil Bulk Density Analysis--
auger and placed into a
were taken at each oour locations tot^L*?^1"8 **** tW° measureme^
Tree Root Biomass--
-
bore a 12-inch deep hole, 1 s t to™ Si, J" SOil auger TOS used to
51
-------
Hammer
L
r-
i
'
Hammer Stem
Hammer Stock
Core
-Auger
Figure 15. Hammer and auger used for collecting soil bulk density sample.
52
-------
Tree Shoot Length—
In 1976, shoot length measurements (in cm.) were used as indicators of
the vigor and growth response of each tree to its immediate soil environ-
ment. Four measurements were taV^n T«»Y« +~~« -n-- •••—-•-•- ~ ••
the
ssss '" that
plant>
TSkX?- sr: r-'=—
Tree Stem Basal Area Increment--
--^"st^LTi^ar
ing nine specie, were Measured a
"
be taken at the end of September ft'thS^ ^^ measurements
were converted to eros.-^ct dimet™
percent increase in cross- sectional
Tree Leaf Weight—
2. From each of these four shoots, collect all the leaves (needles)
from last year's bud scar to this year's terminal bud and place
those from each shoot in a separate bag. Dry for approximately
twenty-four hours at 150°F and then weigh.
For evergreens, excluding Japanese yew:
1. Collect all the needles along the current year's leader shoot and
53
-------
place them in a bag.
2. Select three other shoots, two from the top whorl and one from the
whorl second from the top. Collect needles from these three shoots
and place them in three separate bags.
The needles were oven-dried for approximately twenty-four hours at 150°F
and then weighed.
TABLE 7. DISTANCE FROM THE SOIL SURFACE AT WHICH
STEM INCREMENT WAS MEASURED
Latin Name
Species
Common Name
Distance from Soil
(cm)
Acer rubrum
Euonymus alatus
Fraxinus lanceolata
Ginkgo biloba
Gleditsia triacanthos
Liquidambar styraciflua
Myrica pensylvanica
Nyssa sylvatica
Poplus
Foplus
Picea glauca
Platanus occidentalis
Pinus strobus
Pinus thunbergi
Quercus palustris
Rhododendron elegans
Salix babylonica
Tilia americana
Taxus cuspidata capitata
Red Maple
Euonymus
Green Ash
Ginkgo
Honey Locust
Sweet Gum
Bayberry
Black Gum
Hybrid Poplar
Mixed Hybrid Poplar
Norway Spruce
American Sycamore
White Pine
Japanese Black Pine
Pin Oak
Rhododendron
Weeping Willow
American Basswood
Japanese Yew
30
5
30
30
30
8
3
8
30
5
3
30
5
5
30
3
30
30
3
Physical Condition of Trees—
At monthly intervals during the summer of 1977, observations were
recorded for every tree which showed signs of stress. Leaf loss, scorch,
chlorosis, dieback and wilt were included as signs of stress. At the end of
the growing year, each tree was given a number from 0 to 5 based on the phys-
ical appearance of the tree. Zero indicated a dead tree and five the
healthiest.
Statistical Methods
Analysis of variance, Student's "t" and multiple stepwise regression
techniques were employed for data analysis (135). Library programs of the
Bio-Med (BMD) series and Statistical Analysis System (SAS) at the Rutgers
University Computer Center were employed.
-------
In the analysis of variance, the response variables were leaf weight
shoot length, root Manas s and basal stem area increment. Data for these
variables were collected on each of the ten replicates for each species on
the experimental and control plots, as well as on all ten trees planted in
each gas-barrier technique.
In the regression analysis, American basswood was chosen for study
because it was growing in those areas (i.e on the gas-barrier techniques)
which exhibited a wide range for the soil variables included in the analysis
Ten independent variables were considered: soil gases (six variables?
oxygen lowest oxygen, carbon dioxide, highest carbon dioxide, methane,
highest methane; soil temperature (two variables) - temperature and highest
temperature; soil moisture content (one variable) and soil bulk density (one
R2 a** aen ,o L11"11*! "^ed °n ^ regression were' significant F values,
.R and all coefficients with P < 0.05. A prediction equation was then
Sm 22 VariaMe (i'e- ^"i**, shoot length, root
Environmental Conditions
Weed Growth —
Weeds including goldenrod, ragweed, mustard plant and a variety of
grasses established themselves over much of the area on both the experimental
and control plots. However, the control plot was covered more quickly and
more completely than the experimental plot. The grasses comprised a greater
portion of the weeds on the control plot.
The two mounds on the experimental plot and the mound and the trench on
the control area supported weed growth similar to the gravel/plastic/vents
trench which exhibited the best vegetative growth in general.
Hurricane Effects —
On August 10, 1976, Hurricane Belle passed within 50 miles of East
Brunswick New Jersey, site of the landfill experiment depositing 2.U inches
% l^S^f tHa in- *f V6100"163 °f ^ *iles per hour from tne northwest.
%*lltG°*the T^0? securin§ each tree to stakes, the wind caused
damage to trees on both the experimental and control plots.
Twenty-one trees on the control plot were shifted substantially in the
soil by the strong winds Seven of these were blown over to the extent that
their trunks formed a U5° angle with the ground. The trees most affected
were the tallest i e green ash (#7 & 6l) weeping willow (80, 91, 12?) and
American sycamore (84 & 86). These seven trees were placed In the erect
position and restaked. Tree #15^, a rhododendron, was split in half at the
base ol the stem and had to be removed from the site.
On the experimental plot, three green ash trees (10, 15 16) were blown
about so that a much enlarged hole was created around the base of the trunk
The soil was quite loose in the root zone because some large roots had been'
moved in the soil. These trees had to be restaked and the soil packed down
around the roots to ensure that the small roots again had contact with the
soil. One of the green ashes (#10) had broken loose from the chain lock
55
-------
securing it to the stakes, allowing the trunk to rub against one of the
stakes and causing the bark and part of the cambium to be scraped off for
lk inches along the trunk. Also affected was a Japanese black pine (#l8l)
which was blown over to about a ^5° angle with the soil. This tree was
placed in an erect position and the soil packed down to ensure good root
contact with the soil.
Drainage—
The overall slope of the sites was measured with an Abney hand level.
The slope in the north-south direction on the experimental plot was slightly
great-er (2°) than on the control (1°) which gave the experimental plot better
drainage than the control. The east-west slopes were about 1° on both plots.
The difference in drainage between the two plots was very noticeable
following Hurricane Belle in August 1977. Ponding of water was observed on
the control plot for five days following the hurricane whereas ponding on
the experimental plot lasted only one day.
SIMULATED LANDFILL STUDIES
Selection of Gas Concentrations for Greenhouse Studies
In order to select realistic concentrations of landfill gas components
for inclusion in simulated mixtures for greenhouse studies, soil gas con-
centrations of twenty sanitary landfills visited throughout the continental
United States were measured between August 1975 and January 1977 (52). Of
these landfills five had completed filling since 1966 or were still operating
when the data were collected. Only landfills which contained municipal
refuse which was not burnt were used in this study. Seven of the sanitary
landfills had a reported average refuse depth of more than twenty feet and
twelve had an average depth of less than twenty feet of refuse. Information
concerning the landfills was obtained by questioning landfill operators and
public works employees.
Sampling sites were chosen by visually examining the landfill for types
of vegetative growth and sampling was done on areas indicative of the types
of vegetation observed. The samples were obtained by making a hole to a
depth of one foot with a ^ inch diameter bar-hole maker. Once the hole was
made the bar-hole maker was quickly removed and a hollow steel probe was
inserted into the hole which was then sealed with a rubber stopper. A MSA
Model 2A Explosimeter was then used to extract a sample through the probe.
This instrument provides a reading of the percent combustible gas in the
sample.
The MSA Explosimeter is sensitive to all combustible gases. The sample
is drawn over a heated catalytic filament which forms part of a balanced
Wheatstone bridge electrical circuit. The combustion raises the temperature
of the filament, thereby increasing resistance in proportion to the concen-
tration of combustibles in the sample. This unbalances the electrical cir-
cuit causing a deflection of the current meter pointer which indicates on the
scale the concentration of combustible gas in the sample. This instrument
was calibrated by means of a MSA (Part #^5^380) calibration kit supplied by
56
-------
the manufacturer Frequent calibration is necessary since the filament may
become contaminated with use.
The approximate concentrations of oxygen and carbon dioxide were ob-
tained by using Bacharach Fyrite Model CPD 02 and Model CUD C0? analyzers
^If^tf S "^J" °Pf ate « toe Orsat principle of gas^nalyJis. 'A
TSS tS O of rn < aaal^c; is chained in a space of known volume from
which the 02 or C02 is removed from the gas mixture by selective absorption
into fluids in the analyzer. The removal of the 02 or C02 from the sample
decreases the pressure exerted by the gas sample on the fluid. The fluid is
in contact with the atmospheric pressure by means of an elastic diaphragm so
that as the gas is absorbed the fluid replaces the gas mixture being mea-
sured. The intrusion of the fluid into the space originally occupied by the
sample provides a measurement of the amount of 02 or C02 removed.
The quality of the fluid in the C02 analyzer is determined by exhaling
a deep breath into the instrument and if it fails to record 2 to h « electrical sterilize for
Fumigation Methods —
co
3% 02, 40J C02, 50% C% and 7% N2. Treatment 2 was a control with compressed
ambient air forced through the soil. The compressed air and tS gas mSSes
were supplied by Mathe son Gas Products Inc. of East Rutherford Nf w JeSeT
in treatment 3 the seedlings were flooded by filling the cans wither to
a depth of several inches above the soil line. In order to iJigatftS
soil, two cans were attached in series to a cylinder contain!™ t^Jr
mixture and equipped with a two-stage gas reg^Sor ?rior^S Bl^tfn! th
seedlings it was determined that alas flow oflPO tn 2£ i pl^lnf the
necessary for each pair of cans in SL?£
57
-------
Maple Seedlings
Gas Sampling Device
Soil
Glass Wool
Gravel
Vacuum Tubing
Gas Mixture
Drain Plugs
Bricks
Figure 16. Modified galvanized steel trash can used to fumigate
maple seedlings.
-------
Treatment 1.
Compressed Air
Treatment 2.
CO- and 50$ CH,
Treatment 3.
Flooded Soil
MR J Trash can with 5 red maple trees
S ) Trash can with 5 sugar maple trees
Compressed gas cylinder
•u" tygon tubing
Figure I?. Design of red and sugar maple fumigation experiment.
59
-------
The gas flow was established by disconnecting the tubing from the cylinder to
the two trash cans and establishing the desired flow in air with a soap
bubble flowmeter. This done, the tubing was reconnected. The flow of gas
through the soil was not determined.
The composition of the soil atmospheres was monitored by extracting a
0.5 ml. sample of air from devices (Figure 5) buried at a 7 inch depth in the
soil and analyzing it with a Carle model 8500 gas chromatograph
The fumigations did not begin until August 9> 1977 by which time the
seedlings had completed most of their seasonal growth. They were from 2- to
4- feet tall at this time.
Analytical Methods —
Transpiration measurements- -The physiological condition of the seedlings
was monitored by periodically measuring the rate of transpiration with a
Lambda Instruments Diffusive Resistance Porometer. This instrument measures
water vapor that evaporates off of the leaf surface and consists of a
sensor which is a modified hygrometer whose electrical resistance varies
inversely with humidity and a portable resistance meter. The instrument was
calibrated by means of an acrylic plate with holes drilled in it which was
placed over filter paper saturated with water to simulate the stomatal resis-
tance. If the root system was damaged, the tree would be unable to take up
water fast enough to support normal transpiration. Readings were taken only
on leaves which were fully illuminated and in the upper one- third of the
seedling. Measurements of transpiration rate were obtained only on sunny
days. It required two to three hours to take transpiration measurements on
all sixty seedlings. Therefore, sampling had to be performed in such a way
as to compensate for the changes in illumination caused by movement of the
sun or the occurrence of clouds. This was done by taking readings on only
two seedlings in each can before moving on to the next one. After all the
cans had been sampled in this manner, measurements were begun again on the
remaining three seedlings in each can. If the weather changed after the sets
of two readings were completed but before the rest of the data were collected
then only the data obtained in the first sets were reported. If the weather
conditions changed noticeably before the first sets of two readings were
completed, the data were not reported. .
Soil gas analyses — The composition of the soil atmosphere in treatments
1 and 2 was monitored regularly during the course of the experiment. From
August 9 through August 25, the flow of gas as it came out of the cylinder
was 120 ml. per minute for each group of two trash cans. From August 26
through August 29 treatments 1 and 2 were discontinued due to an interrup-
tion of the gas delivery. From August 30, for the duration of the experi-
ment, the flow of gas coming out of the cylinder was 220 ml. per minute for
the two cans containing the sugar maples and 250 ml. per minute for the two
cans containing the red maples. The increased flow of gas to the red maples
was found to be necessary in order to maintain a soil atmosphere similar to
that given the sugar maples. On September, 20, 21 and 22, the gas treatment
was discontinued to the red maples receiving C02 and CH^ due to problems with
the regulator. The control seedlings were fumigated with compressed air at
the same rate of flow used for the corresponding species in treatment 1.
60
-------
This experiment was terminated on September 27, 1977.
Statistical methods—Where there were two means to be compared the data
were statistically analyzed by means of Student's "t" test. Where more than
two means were involved statistical significance was determined by means of
analysis of variance (135).
The Effect of Simulated Landfill Gas on Tomato Plants in Solution Culture
Cultural Methods—
Rutgers tomato plants were grown in specialized 4-liter culture vessels
in sand solution culture (Figure 18). The plants were watered daily with a
solution containing nutrients in the following molar concentrations: .0019 M
KgSQip .0016 M KHjjPOli, .
-------
Plant Stem
Lid (l*|lf diameter)
Gas Outlet
Gas Sampling Device
Thermometer
Washed Sand
Glass Wool
Gravel
Water Drain
Figure 18. Culture vessel for tomato plant fumigations.
62
-------
Plant Stem
Cotton and Vacuum Grease
A. Partially Dissected Side View
B. Top View
Glass Lids
Gas Outlet
Notch in Top Lid
Plant Stem
Notch in Bottom Lid
Figure 19. Lids for culture vessels.
63
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9. This experiment was conducted twice; from March 22, 1977 to March 30,
1977 and again from April 19, 1977 to May 1, 1977. The first trial was of
shorter duration (8 days) than the second trial which lasted twelve days.
TABLE 8. COMPOSITION OF ATMOSPHERES USED TO FUMIGATE
TOMATO PLANTS IN EXPERIMENT 1
A*
%0 21
$>C00 trace
$N2 79
$CH, 0
Treatment
B
7
trace
93
0
c
7
10
58
25
* Atmospheric air
TABLE 9. COMPOSITION OF ATMOSPHERES USED TO FUMIGATE
TOMATO PLANTS IN EXPERIMENT 2
Treatment
fo02
%co2
$N2
*CH,
A*
21
trace
79
0
B
5
trace
95
0
c
5
Uo
55
0
D
5
Uo
5
50
E
5
trace
U5
50
* Atmospheric air
Experiment 3, was designed to determine the effects of a soil atmo-
sphere containing high concentrations of carbon dioxide on the growth of
tomato plants exposed to differing oxygen concentrations in the soil. This
experiment consisted of twelve plants which were divided into three treat-
ments with four replicates for each. Due to the results of previous exper-
iments in which plant response to low 02 and ambient air fumigations were
identical, air controls were eliminated. The composition of the atmospheres
used to fumigate the culture vessels in the various treatments is given in
Table 10. The fumigation was started on October 15, 1977 and was completed
on November 10, 1977.
Experiment k, was designed to determine the effects of a soil atmo-
sphere containing high concentrations of methane or carbon dioxide on the
-------
growth of tomato plants. This experiment consisted of sixteen plants which
were divided into four treatments with four replicates for each. The compo-
sition of the atmospheres used to fumigate the culture vessels used in the
various treatments is given in Table 11. The fumigation began on December
10, 1977 and was'discontinued on January 9, 1978.
TABLE 10. COMPOSITION OF ATMOSPHERES USED TO FUMIGATE
TOMATO PLANTS IN EXPERIMENT 3
A
$02 U
-------
SECTION 6
RESULTS
COMPOSITION OF THE SOIL ATMOSPHERES OF TWENTY COMPLETED SANITARY LANDFILLS
The majority of the C02 readings in the atmospheres occurred in the 0 to
4.9$ category (Table 12). The majority of the Oo readings in the atmospheres
of the twenty landfills occurred in the 15 to 21% concentration category
(Table 13). The combustible gas readings were concentrated in the two
extreme categories, between 0 and 4.9$ and greater than 25$, with the major-
ity of the readings occurring in the 0 to 4.9% category (Table 14). This
tendency of the readings to polarize at the extreme ends of the scale was
also noted with respect to the C02 readings (Table 12). The landfills com-
pleted prior to 1966 exhibited lower average C02 and combustible gas read-
ings in conjunction with higher average 02 readings than the landfills com-
pleted since 1966 (Table 15). These differences were not statistically
significant. The landfills having less than 20 feet of refuse did not
exhibit any significant differences in the average concentrations of the soil
atmospheric components when compared with the landfills having more than 20
feet of refuse (Table l6).
TABLE 12. PERCENT FREQUENCY OF C02 READINGS* OF SOIL ATMOSPHERES
ON TWENTY COMPLETED SANITARY LANDFILLS
% Range % Frequency
0 -
5 -
10 -
15 -
20 -
4.9
9.9
14.9
19-9
4o+
67.2
10.3
6.0
1.7
14.7
* Il6 samples at one foot depth.
66
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TABLE 13. PERCENT FREQUENCY OF C>2 READINGS* OF SOIL ATMOSPHERES
ON TWENTY COMPLETED SANITARY LANDFILLS
% Range % Frequency
0 - *K 9 7.0
5 - 9.9 7.0
10 - lU.9 Ik.k
15 - 21 71.6
* 128 samples at a one foot depth.
TABLE lU. PERCENT FREQUENCY OF COMBUSTIBLE GAS READINGS* OF THE
ATMOSPHERES ON TWENTY COMPLETED SANITARY LANDFILLS
1o
0
5
10
15
20
25
Range
- U.9
- 9.9
- 1U.9
- 19.9
- 2^.9
- 1+0+
% Frequency
81.6
k.6
0.6
0.5
0.3
12.3
350 samples at a one foot depth.
TABLE 15. MEAN PERCENT CO^, 0 AND COMBUSTIBLE GAS AT
1-FOOT DEPTH WITH AGE OF SANITARY LANDFILL
__^ — ^— —
Gas %
°2
co2
Combustible Gas
Completed Before 1966*
19.0
2.2
1.7
Completed After 1966**
15.2
8.7
8.9
* Average of 5 landfills.
** Average of 15 landfills.
67
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TABLE 16. MEAN PERCENT 0 , CO AND COMBUSTIBLE GAS AT 1-FOOT
DEPTH WITH DEPTH OF REFUSE IN THE SANITARY LANDFILL
Gas % >20 Feet* <20 Feet**
°2
CO
Combustible Gas
15.9
7.3
5.0
17.3
5.3
8.9
* Average of 7 landfills.
** Average of 12 landfills.
COMPOSITION OF THE SOIL ATMOSPHERE AND ITS INFLUENCE ON THE DISTRIBUTION OF
NATIVE VEGETATION ON THE COMPLETED EDGEBORO SANITARY LANDFILL
Data for in situ measurements of gas composition on the Edgeboro Land-
fill by the macro-sample method are presented in Tables 17, 18, and 19 and for
the micro-sample method (gas chromatography) in Table 20 and 21. At all
stations monitored there was a consistent relationship between the occurrence
of high levels of combustible gas and poor or no growth of vegetation. This
relationship was also evident when comparing high levels of C02 and low
levels of 02 with poor growth of vegetation.
The four stations A, B, C, and D, monitored for the entire fifteen
months (Table 2) exhibited very little fluctuation in composition of the
soil atmosphere. This was also true for the stations E, F, G, and H moni-
tored for only five months.
The cover material was significantly thicker (P < 0.05) where the
vegetation was growing well (Table 22).
TABLE 17. PERCENT COMBUSTIBLE GAS FROM 1-FOOT DEEP TEST HOLES ON
COMPLETED EDGEBORO LANDFILL
Sampling Data
Station 6/6/76* 7/15/76** k/15/77* 8/10/77** 9/1^/77* 9/20/77*
A >1*5
B >1*5
C 4. 5
D 0
E
F
G
H
ho
>h5
~ 3
Wet
--
—
—
—
39
>1*5
~ 3.3
1.0
15
1
1*5
0
]|Q
^^4-5
|i C
Wet
>1*5
0'
>^5
0
39
36
0.8
0
--
0
—
--
ho
>1*5
~ 2.2
0
>^5
5
32
0.5
(continued)
68
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TABLE 17. (continued)
Sampling Data
Station 6/6/76* 7/15/76** V!5/77* 8/10/77** 9/1V77* 9/20/77*
I -- — ~ " - 0
j - -- ~ ~ - >U5
K - " " " -- 0
* Average of U readings. — no reading taken.
** Average of 2 readings. Data obtained with a MSA explosimeter.
TABLE 18. PERCENT 0 *FROM 1-FOOT DEEP TEST HOLES ON
COMPLETED EDGEBORO LANDFILL
Sampling Date
Station 7/15/76** V15/77*** 8/10/77**
A
B
C
D
E
F
G
H
5.0
6.0
20.0
wet
3.5
7.0
19. ^
20.0
If. 2
21.0
8.5
20.5
7.5
2.5
18.75
wet
Hi. 5
20.0
• 7.5
20.5
* Readings were obtained with Bacharach, Fyrite 0 analyzer.
** one reading.
*** Average of 2 readings.
-------
TABLE 19. PERCENT CC>2 *FROM 1-FOOT DEEP TEST HOLE ON
COMPLETED EDGEBORO LANDFILL
Station
A
B
C
D
E
F
G
H
* Readings were
** One reading.
*** Average of 2 ]
7/15/76**
17.0
18.0
0.5
wet
obtained with
readings.
Sampling Date
b/15/77***
21.0
25.0
1.0
0.0
12.5
0.5
16.0
0.0
Bacharach, Fyrite C0? analyzer.
8/10/77**
16.0
34.5
1.5
wet
9.0
1.5
20.0
0.0
TABLE 20. GAS CHRCMATOGRAPHIC ANALYSIS OF COMPOSITION OF SOIL
ATMOSPHERE AT DEPTH OF 10-INCHES AT 6 STATIONS ON
COMPLETED EDGEBORO LANDFILL, JULY l4, 1977
Station
A
B
C
D
E
F
°2
0.5
2.7
18.2
20.3
2.0
18.2
Gas (% by
co2
38.0
35.3
4.2
1.7
35.5
4.2
volume)*
CHU
49.5
• 39.0
3.6
0.0
34.5
0
N2
12.0
23.0
74.0
78.0
28.0
77.6
* Corrected to 100 percent.
TABLE 21. GAS CHRCMATOGRAPHIC ANALYSIS OF COMPOSITION OF SOIL
ATMOSPHERE AT DEPTH OF 10-INCHES AT 6 STATIONS ON
COMPLETED EDGEBORO LANDFILL, OCTOBER 13, 1977
Station
A
B
C
00
2
0.8
1.5
19.0
Gas ("jo by
C00
2
37.5
32.0
1.0
volume)*
CH
4
46.7
48.5
0.0
N
2
15.0
18.0
80.0
(continued)
70
-------
TABLE 21. (continued)
Station
D
E
F
°2
20.2
3.0
18.8
Gas
co2
1.2
30.0
2.2
(% by volume)*
CHU
2.6
36.0
1.0
N2
76.0
31.0
78.0
Corrected to 100 percent.
TABLE 22. DEPTH OF SOIL COVER* AT STATIONS ON EDGEBORO
LANDFILL AND GROWTH STATUS OF VEGETATION
Good Vegetative Growth
Station
Poor Vegetative Growth
Depth of Soil
Cover (inches)
Station
Depth of Soil
Cover (inches)
c
F
D
H
K
I
Mean
* Each value is
** Significantly
10.0
10.1
8.2
9.5
6.7
6.5
8.5**
the mean of 5
greater ( P <
A
B
E
G
J
Mean
observations.
0.05).
5.1
• 7.U
3.9
3.0
3.9
IK 7
SPECIES SCREENING EXPERIMENT
Relative Viability of Plants
Sixty-two trees died on the experimental and control plots during this
study: 38 on the experimental and 2k on the control plot (Table 23).
71
-------
TABLE 23. NUMBER OF TREE DEATHS IN SCREENING EXPERIMENT
BETWEEN 1976 AND 1977
Species
Rhododendron
Hybrid Poplar
Mixed Hybrid Poplar
Euonymus
Black Gum
Sweet Gum
Weeping Willow
Red Maple
Ginkgo
Bayberry
Japanese Yew
Norway Spruce
Exp.
2
0
0
0
k
1
1*
0
0
0
0
0
11
Summer
1976
Control
2
1
2
0
1
0
0
0
1
0
0
0
5
16
Exp
2
1
0
5
0
1
0
0
0
0
0
0
9
Winter
1976-77
Control
k
0
5
0
1
0
0
0
0
0
0
0
10
19
Exp.
6
6
0
i
i
2
0
1
0
0
0
1
18
Summer
1977
Control
U
2
0
0
0
1
0
0
0
1
1
0
9
27
Relative Growth of Surviving Plants
The interpretation of whether a particular species grew significantly
better on the control or on the experimental plot depended upon the tree
variable measured (Table 2U). On the basis of three or more of these depen-
dent (tree) variables, the majority of species grew significantly better on
the control than on the experimental plot.
Shoot length was the only tree variable measured both in 1976 and 1977.
With respect to shoot length, twelve species on the control plot appeared
to grow better during the 1977 season than in 1976; whereas on the experi-
mental plot, only seven species apparently grew better during the 1977
growing season than they did during 1976. This is indicated by the average
shoot length calculated for each species - plot combination for each year
(Table 2*0 and reflects the stress on the trees growing on the experimental
plot.
72
-------
TABLE 2k. MEAN VALUES FOR THE FIVE TREE VARIABLE FOR EACH SPECIES
ON THE EXPERIMENTAL AND CONTROL PLOTS
.
Species
Red
Maple
Euonymus
Green
Ash
Ginkgo
Honey
Locust
Sweet
Gum
Bayberry
Black
Gum
Norway
Spruce
Hybrid
Poplar
Mixed
Poplar
American
Sycamore
White
Pine
Black
Pine
Pin
Oak
Weeping
Willow
American
Basswood
1
Plot
Cont.
Exp.
Cont.
Exp.
Cont.
Exp.
Cont.
Exp.
Cont.
Exp.
Cont.
Exp.
Cont.
Exp.
Cont.
Exp.
Cont.
Exp.
Cont.
Exp.
Cont.
Exp.
Cont.
Exp.
Cont.
Exp.
Cont.
Exp.
Cont.
Exp.
Cont.
Exp.
Cont.
Exp.
Root
Biomass
(mg)
1270
579
1807**
691
1U16
681
958**
U77
1370
821
1522**
1*32
868**
29k
1098
52U
689
U97
895*
335
270
592
1375
778
1829
961
1281
907
10U?
628
186U**
U29
1865**
713
Leaf
Wt.
(g)
6.U**
2.U
1.2**
0.2
10.5**
U.3
0.36
0.35
23.9 **
2.8
7.6**
3.7
2.0
2.3
2.U
1.8
0.37
0.3U
8.0 **
1.0
3U.O
2k.Q
11. U
7.8
2.3
1.7
15.9*
12.0
U.5
3.6
11.6*
3.9
1.0
1.2
Visual Basal
Obs. Area
% increase
U.U*
2.8
3.5**
1.1
U.6**
3.1
l.i
1.3
U.7**
1.7
U.9**
2.1
3.U
U.2
U.2
2.6
3.9
2.8
2.5
1.3
U.I
U.2
1+.9**
2.9
U.3**
3.U
U.9**
3.8
U.8*
3.8
U.5**
1.0
2.7
2.7
69.2
39.0
UU.5
28.9
57.1**
23.8
12.6
7.U
9U.7**
25
198 **
86
66.3
U6.7
178
211
3U.3
35.6
696
16
U362
1178
53.0**
33.5
52.0
Uo.o
68
65
115 *
76
llU •**
.17
28.8 **
19.2
Shoot Length
(cm)
1976 1977
20.6
21.6
18.8**
15.2
30. U
3U.O
17.8
23.3*
10. U
11.7
12.7
12.2
10. U
7.U
7.9
8.6.
12.2
10.9
35.0**
20.0
25. U
31.0
22.6
20.6
20.8
15.2
18.8
19.3
13.7
12. U
69.6
75.2
19.8
19.0
U5.5
15.2
13.2*
3.8
15.5**
5.8
0.8
0.8
68.6**
5.1
35.3
17.0
20.3
17.0
25.6
20.8
U.8
6.1
85.8
12.7
13U.1
92.9
U2.2
U3.7
10.9
v • j
7.9
19.8**
1U.5
23.1**
13.5
217.2**
65.6
18.5**
9.9
1 - % increase from March to September
73
(continued)
-------
TABLE 2k. (continued)
Species Plot Root Leaf
Biomass Wt.
(nig)
Japanese Cont. 1087
Yew Exp. 572
Rhododendron Cont. 0
Exp. 0
* Significant difference
** Significant difference
(g)
0.98
0.50
0
0
Visual Basal Shoot Length
Obs. Area (cm)
% increase l 1976 1977
U.6 19.3** 11.9 12.2
^.3 ^5 12.7 19.6
0 0 8.U* 0.0
0 0 6.1 0.0
between control and experimental plot @ 95$, C.L.
between control and experimental plot @ 99% C.L.
The results of Student's "t" tests for the dependent variables (i.e.
root biomass, shoot length, leaf weight and basal area) comparing experi-
mental with control plot indicated that black gum exhibited the least
difference in growth between the experimental and control plot (Table 25).
Rhododendron had the poorest growth of all species in that all replicates on
both plots succumbed by the end of the winter of 1976-1977, presumably from
the abnormally cold temperatures.
TABLE 25.
Rank a
1
2
3
U
5
6
7
8
9
10
11
12
13
1U
15
16
17
18
19
RELATIVE TOLERANCE OF SPECIES
Species
Black Gum
Norway Spruce
Ginkgo
Black Pine
Bayberry
Mixed Poplar
White Pine
Pin Oak
Japanese Yew
American Basswood
American Sycamore
Red Maple
Sweet Gum
Euonymus
Green Ash
Honey Locust
Hybrid Poplar
Weeping Willow
Rhododendron
TO LANDFILL CONDITIONS
Z "t" Statistics b
2.66
3.22
^.95
6.59
6.62
8.13
8.9U
8.96
8.98
9.U8
10.66
10.95
12.62
1U.25
1U.8?
15.05
20.33
21.20
All plants died
(continued)
-------
TABLE 25. (continued)
a. Rank 1 = the best growth when experimental plot is compared to the
control plot, i.e. most tolerant of landfill conditions.
b. H"t" = the sum of the "t" statistics for shoot length in 1976; leaf
weight, basal area increase, root biomass and shoot length in 1977
comparing the experimental area with the control.
Soil Variables
Measurements of numerous soil variables throughout the study were made
in order to characterize the nature of the stress to which the plants were
subjected on the experimental plot and to compare the values for these
variables with those in the control plot (Table 26). The mean carbon dioxide,
methane and temperature were significantly greater (99% C.L.) and the oxygen
and moisture content significantly lower on the experimental plot than on the
control plot.
The calcium content (Table 26) was not significantly different between
plots immediately after fertilization in June 1977; however, by November,
the experimental plot contained less calcium than the control (99% C.L.).'
The pH was significantly lower on the control before and after fertilization
(99# C.L.). There were no other significant differences for any of the other
measured nutrients between plots.
The soil textures (Table 26) were different (99* C.L.) between the two
plots with the experimental plot consisting of 82.8% sand while the control
plot contained 7^.0$ sand.
The moisture content of the experimental plot and control plots over
time during the summer 1977 is represented in Figure 20. For every date the
control plot shows a greater moisture content than the experimental plot.
TABLE 26. MEAN VALUES FOR SOIL VARIABLES ON EXPERIMENTAL
AND CONTROL PLOTS IN 1977
Soil Variables Experimental Control
<& 02 17.8
% co2 5.5*
% CHU 0.9*
Temperature °F 66.2*
% Moisture Content 8.1
pH 5.0
Mg lUl
P 106
19.7*
1.2
0.0
61*. 3
11.0*
U.8
1U3
97
(continued)
75
-------
TABLE 26. (continued)
Soil Variables
Experimental
Control
K
CA
COND
NO,,
Organic Matter
Fe
Cu
Zn
Mn
B
Sand
Silt
Clay
252
266
29
42
201
9.6
54.7
196
579
301
67
82.8
283
229
32
271
10
82
210
465
385
62
7^.0
* Differences between experimental and control plots significant at 99% C.L.
The average nitrate (N0§) and ammonium (NH^) nitrogen for the experi-
mental and control plots are given in Table 27 for samples collected on
three separate dates in 1976 and 1977. There was no significant difference
between plots for NH^ nitrogen on any of the three dates in spite of the
fact that, in June 1977, the NHt on the control was much greater in concen-
tration than on the experimental plot. A single very high reading on the
experimental plot was the cause for this large difference.
TABLE 27. MEAN VALUES FOR NITRATE AND AM40NIUM NITROGEN
ON EXPERIMENTAL AND CONTROL PLOTS
Experimental a
Control b
Date
October '
June '77
November
a.
b.
76
'77
N03
Ibs/A
6.0
67.1
16.8
Ibs/A
58.
370.
10.
Each number is the average
Each number is the average
Significantly greater than
3
0
8
Ratio
0.10
0.18
1.56
Ibs/A
10.
103.
39.
5
2
5
Ibs/A
48.5
587.1
11.5
Ratio
N03:NH4
0.22
0.18
3.43*
of 7 separate measurements.
of 4 separate measurements.
experimental plot (95% C.L. ).
76
-------
0)
3/16 3/31 k/19 5/1 5/15 6/7 6/22 7/7 7/20 8/7
Date (1977)
Figure 20. Soil moisture content of experimental and control plots.
77
-------
The NOo nitrogen content in the experimental plot was statistically
similar to that in the control after fertilization in June 1977; however,
by November, NOg was significantly lower in the experimental plot (95$ C.L.).
This resulted in a significantly lower NO~:NH. ratio in the experimental plot
than in the control.
Despite the anticipated variability in the independent soil variables
from one sampling location to another, and from one sampling date to the
next on the control plot, the variability on the experimental plot was far
greater than on the control particularly for oxygen, carbon dioxide and
methane. This is reflected in the coefficients of variation calculated for
each independent soil variable in both plots (Table 28).
TABLE 28. COEFFICIENTS OF VARIATION FOR SOIL VARIABLES
ON EXPERIMENTAL AND CONTROL PLOTS
Soil Variables
°2
C°2
CH^
Temperature
Moisture Content
pH
Mg
P
K
CA
COND
NO
NH^
Organic Matter
Fe
Cu
Zn
Mn
B
Experimental
26. 42**
117. 34**
388.86**
13.47
28.19
5.63
66.86
50.09
44.50
115.69
54.00
73.69
104. 71
77.85
149. 87
106.65
51.19
82.83
48.25
Control
4.02
36.29
0.00
12.49
29.07
4.11
60.91
77.90
36.97
119.73
63.32
59.32
133. 57
72.17
125.19
105.84
60.22
71.53
65.15
** Significant at 99% confidence level.
Root System Profiles
The extent of vertical root penetration for plants growing on the
experimental landfill plot was found to be approximately 6-8 inches with the
root biomass in the top 6 inches of soil. The data indicated that the roots
of plants growing on the control plot penetrated 2-h inches (or 1.5 times)
deeper than on the experimental plot (Table 29).
78
-------
TABLE 29. DEPTH OF ROOT PENETRATION ON EXPERIMENTAL AND CONTROL PLOTS &
Species Experimental Plot Control Plot
Basswood
Sycamore
Sweet Gum
Black Gum
Black Pine
6"
5"
6"
h"
5"
9"
7"
10"
7"
8"
•*
*
•*
a. Average of U trees.
* Significant difference between plots @ 95% C.L.
GAS-BARRIER TECHNIQUES
Relative Viability of Plants
All plants in the gas-barrier techniques broke bud soon after planting
in the spring of 1976. During the following growing season all ten plants
(6 American basswood and k Japanese yew) on the clay/vents trench died as
well as ten Japanese yew scattered on the remaining barrier techniques
(Table 30). All remaining plants survived the winter 1976-1977, however, by
the end of the 1977 growing season, six plants had died (1*. of these were'in
trench-clay/vents where 6 plants had died the previous year).
Relative Growth of Surviving Plants
Tree data collected in 1976 and 1977 from the five experimental gas-
barrier techniques and the experimental screening area (which serves as a
control for the barrier techniques) for American basswood and Japanese yew
are given in Table 31. For American basswood, the gravel/plastic/vents
trench and clay barrier mound on landfill supported significantly better
(99% C.L.) growth than did the experimental screening area which had no
special treatment and represented typical landfill conditions. This was true
for all the dependent (tree) variables measured excluding root biomass The
variability in root biomass among the basswood trees within each of the
planting techniques is reflected in the relatively large variance components
among trees compared to those among techniques (Table 32). Because the
variability among trees was greater than the variability among barrier tech-
niques, no statistical differences were detected between barrier techniques
and experimental screening area despite the large difference in mean root
biomass. However, the measurements for root biomass for the gravel/plastic/
vents trench, the clay barrier trench and the clay barrier mound fall at the
high end of the range of values for all techniques (Table 32).
Japanese yew showed no significant differences between the barrier
techniques and the experimental screening area. The variance components for
Japanese yew wxthin the barrier techniques were relatively large compared to
among techniques for shoot length, leaf weight and root biomass illustrating
the great variability among trees compared to the variability among barrier
79
-------
TABLE 30. OBSERVATION OF DEAD TREES OK EXPERIMENTAL
AND CONTROL GAS-BARRIER TECHNIQUES
Seasons
1976 Growing Season 1976-1977 Winter 1977 Growing Season
Experimental a Control a Experimental Control Experimental Control
American
Basswood
216
217
218
219
220
221
Japanese
Yew
223 23^
225 238
226 239
227 2^0
231 2Ul
233
American
Basswood
192
Japanese
Yew
210
No trees No trees American
died died Basswood
216
217
219
220
Japanese
Yew
228
229
No trees
died
a. All these plants were replaced in October 1976.
techniques (Table 32), resulting in no significant difference between any of
the techniques and the experimental screening area (Table 31).
Soil Variables
_ ^.
The average nitrate (NO^) and ammonium (NHlj.) nitrogen content in each
barrier technique is given+in Table 33 for samples collected on two separate
dates in 1977. The NO§:NH^ ratios in Jun| for all techniques were relatively
similar, however, by November, the NOjrNH^ ratio was more than two times
lower in the clay/vents trench than any other technique. There were no other
discernable nutrient trends other than a small decrease in the manganese
concentration in the clay/vents trench compared to a relatively large de-
crease in all other barrier techniques, resulting in a high manganese (U5
ppm) concentration by November (Table 33) in the clay/vents trench.
The values for soil oxygen, carbon dioxide, methane, moisture content
and bulk density are given in Table 3^ for each gas-barrier technique. These
data show that the gravel/plastic/vents trench and the two mounds on the ex-
perimental plot contained no excessive amounts of carbon dioxide and no
methane and that the oxygen concentration was 19.8% or greater. However,
carbon dioxide and methane from refuse decomposition contaminated the clay/
vents trench and the clay trench. The oxygen concentration in these two
latter trenches was also significantly lower than in the control and in the
80
-------
CO
H
TABLE 31. MEAN VALUES FOR DEPENDANT TREE VARIABLES FOR EACH
GAS-BARRIER TECHNIQUE ON EXPERIMENTAL AREA
Planting
Technique
Trench-Plastic/
Vents/Gravel
Trench- Clay/
Vents
Trench- Clay/
No Vents
Mounds-No Clay
Mound- Clay
Experimental
Screening Area
Species
Jap. Yew
Basswood
Jap. Yew
Basswood
Jap. Yew
Basswood
Jap. Yew
Basswood
Jap. Yew
Basswood
Jap. Yew
Basswood
Root
Biomass
(mg)
516
800
7k
153
616
1069
1051
622
1062
930
572
6kb
Basal
Area
"lo »
(increase)
17.0
73.3*
9.3
0.0
26.0
23.9
Ik.0
31.3
6.2
60.0*
1+5.0
26.8
Visual
Obs.
5.0
U.5*
2.0 .
0.0
k.o
3.5
3.5
4.5*
2.5
4.5*
4.3
2.5
Leaf
Weight
(g)
1.24
3.97*
0.4l
0.02
0.59
2.21
0.6k
1.89
0.85
3. to*
10.98
1.04
Shoot Length
1976 1977
(inches)
5.2
12. Ill*
0.52
1.06
5.1
7.19
6.9
10.98*
7.1
12. 15*
5.0
7.46
2.61
8.98*
2.43
.66
2.96
5.58
1.8U
6.66
2.78
8.52*
2.17
3.84
* Grew significantly better than the experimental screening area @ 99$ C.L.
-------
TABLE 32. VARIANCE COMPONENTS FOR AMERICAN BASSWOOD AND
JAPANESE YEW FOR THREE TREE VARIABLES
Shoot Length
American Basswood Japanese Yew
Source of Variation Variance Components Source of Variation Variance Components
Among techniques 73.20 Among techniques 10.59
Among trees 6.53 Among trees 21.50
Among measurements 5.79 Among measurements 2.32
Leaf Weight
American Basswood Japanese Yew
oo
10 Source of Variation Variance Components Source of Variation Variance Components
Among techniques 15.08 Among techniques 0.08
Among trees 0.68 Among trees 0.36
Among measurements 0.79 Among measurements 0.08
Root Biomass
American Basswood . Japanese Yew
Source of Variation Variance Components Source of Variation Variance Components
Among techniques 573,181 Among techniques 57,832
Among trees 9l6,l6o Among trees 286,^32
-------
Ibs/A
oo '
CO
TABLE 33. NITRATE NITROGEN, AMMONIUM NITROGEN AND MANGANESE
CONTENTS OF SOIL IN THE BARRIER TECHNIQUES
Experimental Plot Control Plot
Trench-gravel, Trench-clay Trench-clay Mound-no Mound Trench Mound
plastic, vents vents no vents clay clay
June Nov. June Nov. June Nov. June Nov. June Nov. June Nov. June Nov.
77 77 77 77 77 77 77 77 77 77 77 77 77 77
NO. 120.0 20.0 6l.O 12.0 50.0 12.0 57.0 1^.0 U6.0 kO.O 62.0 36.0 13^.0 8k. 0
NHj^ 620.0 8.0 395.0 12.0 280.0 k.O 580.0 2.0 3to.O 16.0 360.0 6.0 560.0 22.0
Ibs/A
NO.rNHj^ 0.19 -2.5 0.15 1.0 0.18 3.0 0.10 7.0 O.l4 2.22 0.17 6.0 0.2^ 3.80
ratio
Mn 90.0 6.5 55.0 1*5.0 50.0 6.0 50.0 8.5 72.5 11.0 M*.5 12.5 77.5 1^.0
ppm
-------
other three techniques on the experimental plot (99$ C.L.).
TABLE 3U. MEAN SOIL VARIABLE LEVELS IN THE GAS-BARRIER TECHNIQUES
Gas-Barrier
Techniques
Gravel/Plastic
H Vents Trench
1 >
g Clay/Vents Trench
US
£ PH Clay Trench
w Mound
Clay Mound
H
h -p Trench
•P 0
B cd Mound
o rrr^rzz^zrr^mmr
Oxygen
foVolume
19. 8c*
if.3a
16. 3b
20. 3c
20. 3c
19. 6c
19. ^c
Carbon
Dioxide
^Volume
1.3a
22. 8c
7. Ob
0.8a
0.8a
1.2a
1.2a
Methane
^Volume
O.Oa
11. 8c
O.?b
O.Oa
O.Oa
O.Oa
O.Oa
Moisture
Content
% Dry
Weight
9. Ob
11. Oc
8.Ub
7.3a
7.5a
10. 5c
10. 7c
Bulk
Density
1.29a
l.l*2a
1.67b
1.3^a
l.U5a
1.73b
l.l*5b
* Means in a column followed by different letters are statistically
different at P <0.01.
The moisture content of the soil in the 'experimental techniques was
generally lower than on the control; however, the highest moisture content is
in the clay/vents trench. In addition, analysis of variance showed that the
soil in the two mounds on the experimental plot had a significantly lower
moisture content than any of the other barrier techniques. Analysis of
variance of bulk density showed that the values in the clay trench on the
experimental plot as well as the trench on the control plot were signifi-
cantly higher than in any other techniques (99$ C.L.).
Statistical Analysis of the Effect of Soil Variables on Tree Variables
Multiple regression analysis of American basswood shoot length data
shows a correlation with the linear responses of carbon dioxide, lowest
oxygen, highest temperature, bulk density and moisture content, R2=53$. The
general multiple linear regression model given in equation 1 becomes the
estimated multiple
regression equation for basswood shoot length in equation 2.
Y = 45.2k - 0.32 lowest oxygen - 0.57 carboi> dioxide - 0.2k highest
temperature - 12.3^ bulk density + 0.78 moisture content. (2)
Addition of the quadratic, reciprocal and interactive effects of these
-------
variables did not change the coefficient of determination (R2).
i
.,«. ?^?le regression ana^sis of basswood leaf weight shows a correlation
with the linear responses of temperature and bulk density, R2 = 4l% according
to equation 3.
Y = 37.86 - 0.37 temperature - 6.58 bulk density (3)
When the quadratic, reciprocal and interactive effects of these vari-
ables were added into the analysis, an increase in R2 of 22% was obtained
with the equation
Y = 37.69 - 0.23 highest temperature - 10.12 bulk density - 0 10
(moisture content x carbon dioxide) - 1.42/CO +4 (4)'
giving an R = 63%.
When the tree response root biomass was regressed onto the ten soil
variables, it was found to correlate linearly with temperature, bulk density
and moisture content, R^ = 39% according to the equation
Y = 15395.87 - 222.17 temperature - 1129.52 bulk density + 269 65
moisture content. (5)
The addition of quadratic, reciprocal and interactive effect of these
variables did not change the coefficient of determination.
Multiple regression.analysis of basswood basal area increment data
shows carbon dioxide and bulk density to be linearly correlated with the
response basal area R^ = 48% as seen in equation 6.
Y = 141.48 - 2.42 carbon dioxide - 59.07 bulk density. (6)
Examination of the quadratic, reciprocal and interactive effects
produced an increase of 5% in the coefficient of determination to R2 -
(see equation 7).
- 2.07 (bulk density x carbon
Y = '60 bulk
THE EFFECT OF CARBON DIOXIDE AMD METHANE IN THE ROOT ZONE OF TWO MAPLE
SPECIES
At the termination of the 48-day experiment to compare the effects of
simulated landfill gases with those of flooding on twolaple s^eciesf bo?h
red and sugar maple trees fumigated with COa and CHI, were in noticeably worse
rf^T^%7^^^^^^
leaves by the Uth day of treatment and defoliations
85
-------
were chlorotic. All the red maples that were flooded exhibited adventitious
root development below or just above the surface of the water and swelling of
the lenticels which were exuding a soft textured white substance.
TABLE 35. NUMBER OF MAPLE SEEDLINGS* EXHIBITING VARIOUS
GROWTH CONDITIONS AT TERMINATION OF EXPERIMENT
1
Condition Red Sugar
Healthy 1 1
2
Air
Red Sugar
6 8
3
Flooding
Red Sugar
0 0
Chlorotic
Lower third
of tree
Lower half
of tree
> half
of tree
Defoliated
Adventitious
5
2
1
k
0 0
0 0
V 2
0 0
0 0
0 0
0 0
3 o
5 0
2 0
0 10
10 0
* 10 seedlings in each treatment.
The rate of transpiration which is inversely related to stomatal diffu-
sive resistance for the sugar maples fumigated with C02 and CHI^ (Treatment 1)
was found to be significantly less than the control on day-2U (Tables 36 &
37). The red maple seedlings fumigated with C02 and CH^ showed no signifi-
cant difference in transpiration from the control at any time during the
experiment (Table 36 & 37). The sugar maples grown in flooded soil showed
a significant decrease in transpiration rate on the 3rd day of the treatment,
whereas the red maples which were flooded did not show a decrease in transpi-
ration until day-^2 of the experiment (Tables 36 & 37).
The composition of the soil atmosphere in the garbage cans fluctuated
during the experiment. These data are given in Figures 21, 22, 23 and 2^.
86
-------
TABLE 36. MEAN STOMATAL RESISTANCE (SEC/CM)* OF RED AND
SUGAR MAPLE SEEDLINGS IN VARIOUS TREATMENTS
Date
1977
8/9
8/10
8/12
8/15
8/18
8/21
8/23
8/29
9/2
9/8
9/21
9/27
C02
Red
6.5
13.5
9.5
8.0
7.5
7.5
8.5
9.0
7.5
13.5
13.5
19.5
1
+ CH^
Sugar
N R
16.0
9.0
7.5
1^.5
8.0
12.0
15.5
21.0
89.5
60.5
1*9.0
Treatment
2
Air
Red
N R
11.0
9.5
7.5
11.0
8.0
9.5
9.5
6.5
13.5
.12.0
17.5
Sugar
7.5
18.5
11.0
7.0
15.5
8.5
13.0
9.0
7.5
17.0
11.0
19.5
3
Flooding
Red
6.5
N R
14.0
7.5
16.5
6.0
11.0
13.0
7.5
17.5
2k. 0
28.5
Sugar
8 5
»->• j
N R
66.5
26.0
81 o
109.0
120.0
N L
N L
N L
NT.
N L
— —
N R No reading.
N L No leaves.
* Each value is the mean of k or 10 readings per 10 trees.
TABLE 37. STOMATAL RESISTANCE* OF MAPLE SEEDLINGS FOR TREATMENTS
1 AND 3 RECORDED AS PERCENT OF CONTROL
Treatment
1
Date
1977
8/10
8/12
8/15
8/18
8/21
8/23
8/29
9/2
9/8
9/21
9/27
C02 H
Red
122.7
100.0
106.6
63.6
93.8
89.5
94.7
115.3
100.0
112.5
111.3
h C\
Sugar
86.4
81.8
106.1
93.4
94.1
92.3
172.2
280.0**
526.4**
550.2**
251.2**
Flo
Red
N R
147.1
100.0
150.0
75.0
115.7
136.7
115.3
129.6
200.0
162.8
3
Sugar
N R
6o4.5**
328.5**
522.5**
1282.3**
882.3**
N L
N L
N L
N L
N L
(continued)
87
-------
TABLE 37. (continued)
N R No readings.
N L No leaves.
* Each value is the mean of k or 10 readings.
** Statistically significant increase (P < 0.01).
EFFECT OF CO AND CHr ON THE GROWTH OF TOMATO PLANTS IN SAND SOLUTION CULTURE
Experiment 1
The average composition of the soil atmosphere in the culture vessels
for each treatment is given in Table 38. No statistically significant
difference was found between the three treatments in terms of total change in
height, total dry weight of the leaves or total nitrogen content of the leaf
tissue (Table 39). Four of these plants exhibited a reddening of the veins
on the intermediate-aged leaves which had been fully expanded at the start of
the fumigation. This symptom was not observed on any of the plants treated
with low 02 or air (Treatments A & B). All the plants receiving high COo and
CH4 concentrations exhibited adventitious root development on the stems above
the glass lids.
Temperatures in the vessels ranged from a low of 65°F to a high of 8l°F
during the experimental period.
TABLE 38. MEAN PERCENT COMPOSITION* OF THE CULTURE
VESSEL ATMOSPHERES IN EXPERIMENT 1
Gas %
Or,
2
co2
No
2
CHU
A
20.7
1.1
78.2
0.0
Treatment
B
12.2
1.3
86.5
0.0
C
10.5
7.2
62.3
20.0
* Mean of 35 to ^0 observations, corrected to 100 percent.
-------
20
10
00
vo
I
o
fH
^
PL,
0
Control Trees
Red Maple
Sugar Maple
8/10 8/15 8/20 8/25 8/30- 9/5 9/10 9/15 9/20 9/25
Date (1977)
Figure 21. Mean percent 0 at 7" depth in fumigated trash cans.
-------
30
20
o
•p
q
0)
o
h
0)
EM
10-
0
Sugar Maple
Red Maple
8/10 8/15 8/20 8/25 8/30 9/5 9/10 9/15 9/20 9/25
Date (1977)
Figure 22. Mean percent C0p at 7" depth in fumigated trash cans.
-------
,, 50 .
-P
£
o
20
10
II
8/10 8/15 8/20 8/25 8/30 9/5 9/10 9/15 9/20 9/25
-Date (1977)
Figure 23. Mean percent N2 at 7" depth in fumigated trash cans.
91
-------
0)
H
O
ro
-P
g
o
0)
Siigar Maple
Red Maple
Control Trees
8/10 8/15 8/20 8/25 8/30 9/5 9/10 9/15 9/20 9/25
Date (1977)
Figure 2k. Mean percent CH^ at 7" depth in fumigated trash cans.
-------
TABLE 39. TOTAL INCREASE IN HEIGHT, FOLIAR DRY WEIGHT,
AND TOTAL NITROGEN CONTENT OF THE LEAVES OF
TOMATO PLANTS* AT THE TERMINATION OF EXPERIMENT 1
Total
Nitrogen (%)
Total dry
weight (g)
Total increase
in height (cm)
A
1.9
13.1
16.7
Treatment
B . C
1.6 1.9
12. k 13.1
10.2 16.7
* Each value is the mean of 7 replicates.
Experiment 2
The average composition of the culture vessel substrate atmospheres for
each treatment in the two trials of this experiment are given in Tables Uo
and Ul.
TABLE UO. MEAN PERCENT COMPOSITION* OF THE CULTURE VESSEL
ATMOSPHERES IN EXPERIMENT 2, (8-DAY FUMIGATION)
Gas %
°2
co2
N2
CH^
A
20.0
0.6
79. U
0.0
B
6.9
0.7
92. k
0.0
Treatment
C
6.6
3U.2
59.2
0.0
D
6.U
39.5
7.6
U6.5
E
6.3
0.9
U7.6
U5.2
* Mean of 20 to 25 observations, corrected to 100 percent.
93
-------
TABLE 1*1. MEAN PERCENT COMPOSITION* OF THE CULTURE VESSEL
ATMOSPHERES IN EXPERIMENT 2, (12-DAY FUMIGATION)
Gas %
°2
co2
N2
CHU
A
20.0
0.5
79-5
0.0
B
6.7
0.1*
92.9
0.0
Treatment
C
6.7
35.1
58.2
0.0
D
5.2
39.2
9.8
1*5.8
E
5.0
1.8
^9.9
1*3.3
* Mean of 30 to 33 observations, corrected to 100 percent.
The plants that were treated with air or low 02, but no CH^ or C02
(Treatments A and B) grew significantly better than did the plants receiving
high C02 with or without CHl^ (Treatments C and D). This was true for both
the 8-day and 12-day trials of the experiment and was evidenced by greater
nitrogen content of the leaf tissue, increased height of the plants and
greater dry weight of the leaf tissue (Tables 1*2 and 1*3). The visual appear-
ance of the plants also bore out this relationship. The plants receiving
high concentrations of C02 with or without City (Treatments C and D) began to
decline after three days of treatment. The symptoms observed were a swell-
ing of the stem accompanied by the formation of adventitious roots which
became more pronounced as the treatments continued. The leaves first became
chlorotic, then completely yellow and finally, necrotic. This decline pro-
gressed upwards on the stem for the duration of the experiment.
At the termination of the 8-day trial the plants receiving air or low
02 (Treatments A and B) were in the same condition as the plants receiving
City and no C02 (Treatment E). This relationship was evident in terms of the
parameters measured and the visual appearance of the plants. During the
second trial (12 days) the plants receiving CH^ and no C02 were in the same
condition as the plants receiving air or low Cfe after eight days of treat-
ment but by the twelfth day they had gone into a rapid decline. This decline
was believed to have been caused by lower 02 concentrations in the vessels
brought about by a build-up of methane-utilizing bacteria in the substrate.
The 02 levels had fallen below 2$ in Treatment E after eight days of treat-
ment concomitant with the decline of the plants. Oxygen depletion was not
observed in any of the other treatments.
During the first trial the temperatures in the greenhouse ranged from
68°F to 77°F and in the vessels from 70°F to 8l°F. During the second trial
the temperature in the greenhouse ranged from 75°F to 88°F and in the
vessels, from 73°F to 90°F. No consistent temperature differences were
observed between the treatments.
-------
TABLE U2. TOTAL INCREASE IN HEIGHT, FOLIAR DRY WEIGHT,
AND TOTAL NITROGEN CONTENT OF THE LEAVES OF TOMATO
PLANTS* AFTER 8-DAYS OF FUMIGATION IN EXPERIMENT 2
Treatment
A B C D E
Total
nitrogen ($) 2. la l.?b
Total dry
weight (g) 8.7a 8.?a
Total increase
in height (cm) l6.5a 15. 3a
1.6b l.5b 2. la
2.7b 3. Ob 9.0a
U.lb U.Tb 15. 5a
* Mean of k replicates.
All values in row followed by an a are greater than values followed by a
b. (P < 0.01).
TABLE U3. TOTAL INCREASE IN HEIGHT, FOLIAR DRY WEIGHT,
AND TOTAL NITROGEN CONTENT OF THE LEAVES OF TOMATO
PLANTS* AFTER 12-DAYS OF FUMIGATION IN EXPERIMENT 2
Treatment
A B
Total
nitrogen (%) 2.58a 2.6Ua
Total dry
weight (g) 9.ka. 9. la
Total increase
in height (cm) 20. 9a 21. la
C
1.68b
3.8c
6.0c
D
1.89b
2.2c
5.0c
E
1.80b
5.9b
16. 6b
Mean of U replicates.
All values in row followed by an a are greater than values followed by a
b or c (P<0.01). Values followed by a b are greater than values followed
by a c (KD.01).
Experiment 3
The mean percent composition of the culture vessel atmospheres for each
treatment is given in Table hk. The plants that were treated with low Oo
and low C02 (Treatment A) grew significantly better than the plants given
high C02 with low 02 or with high Og (Treatments B and C). This relationship
was evidenced by dry weight of the leaf tissue, increased height of the
plants and adventitious root development (Table U5). Five of the plants
95
-------
receiving high COg (Treatments B and C) wilted after three days exposure, and
all but two had recovered from their wilted condition by the fourth day of
exposure. Of the two plants which did not recover, one was in Treatment B
and one in Treatment C. By the tenth day of exposure all the plants given
high C02 (Treatments B and C) exhibited adventitious root development on the
shoots and a general chlorosis of the leaves. The plants remained in this
condition throughout the experiment, exhibiting little additional growth.
Adventitious root development was suppressed on the two plants which had
wilted.
TABLE kk. MEAN PERCENT COMPOSITION* OF THE CULTURE VESSEL
ATMOSPHERES IN EXPERIMENT 3
Gas %
On
C.
co_
2
N2
A
6.3
0.3
93. ^
Treatment
B
17.0
28.7
5U.3
C
6.0
28.8
65.2
Corrected to 100 percent.
TABLE U5. TOTAL INCREASE IN HEIGHT, FOLIAR DRY WEIGHT
AND ADVENTITIOUS ROOT DEVELOPMENT OF TOMATO
PLANTS AT THE TERMINATION OF EXPERIMENT 3
Treatment
A B
Total increase
in height (cm) 4l.3a • 2.Ub
Mean dry
weight (g) 9.0a 3. Ob
Adventitious
root development - +
C
O.lrt>
2.5b
+
* All values in row followed by an a are greater than values followed by a
b (
-------
Experiment 4
The average'composition of the atmospheres in the culture vessels for
each treatment is given in Table 46.
The plants that were treated with low 02 (control) or 10$ C02 (Treatment
A and B) grew significantly better than the plants treated with 20$ C02
(Treatment C). The latter plants all exhibited adventitious root development
and general chlorosis by the seventeenth day of exposure (Table 47). The
adventitious root development involved, on the average, the lower 9-5 centi-
meters of the stem at the termination of the experiment. At the start of the
experiment **.n the plants exhibited an interveinal chlorosis believed to have
been caused by lack of light due to extended cloudy weather. By the tenth
day of exposure this symptom had begun to subside on control and high CH^
treated plants (Treatments A and D) but was more pronounced on the plants
given 10 and 20$ C02 (Treatments B and C). This symptom had disappeared
from all plants by the seventeenth day of treatment but could have been
masked on the plants receiving 20$ C02 by the total chlorosis observed at
this time.
By the seventeenth day of exposure all the plants receiving 50$ City
(Treatment D) exhibited adventitious root development involving the lower
28.5 centimeters or so of the stems at the termination of the experiment.
These plants also exhibited chlorosis of the lower leaves and epinastic
curvature of the lower one-third to one-half of the leaves, not all of which
were exhibiting chlorosis. The development of these symptoms occurred
coneamitantly with the lowering of the Og percentage in the root atmospheres
(Figure 25) presumably dae to the activity of methane-utilizing micro-
organisms.
TABLE 46. MEAN PERCENT COMPOSITION* OF THE CULTURE VESSEL
ATMOSPHERES IN EXPERIMENT 4
Gas $
°2
co2
N2
CHU
A
6.3
0.4
93.3
0.0
Treatment
B
17.4
9.1
73.5
0.0
C
17.1
18.0
64.9
0.0
D
4.3
1.7
49.6
44.4
* Each value is the mean of 12 to 15 observations, corrected to 100 percent.
97
-------
TABLE Vf. TOTAL FOLIAR NITROGEN AND DRY WEIGHT AND
INCREASE IN HEIGHT AND ADVENTITIOUS ROOT DEVELOPMENT
OF TOMATO PLANTS* AT THE TERMINATION OF EXPERIMENT k
Treatment
B C
D
Total
nitrogen (%)
Mean total
dry weight (g)
Total increase
in height (can)
Adventitious
root development
3. la 2.5a
11. Oa 9.5a
41. Oa 51. 3a
-
2.4a 2. Ob
2. Ob 8.5a
3. 8c 29. 3b
+ -f
Mean of h replicates.
All values in a row followed by an a are greater than values followed by
a b or c (P<0.01). Values followed by a b are greater than values
followed by a e (P<0.01).
-------
\o
vo
1
S
2
1
0-
Treatment A (Low Op Control)
Treatment D
(High CHU)
10 15 20
Bays from beginning of fumigation
25
Figure 25. Percent oxygen in culture vessels in tomato Treatments A and D (Experiment U).
-------
SECTION 7
DISCUSSION
A survey of soil atmospheres on twenty completed sanitary landfills
throughout the United States revealed that combustible gas (methane) CO
and, to a lesser degree, 02 readings were concentrated in two extreme pe§-
centage categories rather than being' evenly distributed among all of the
categories (Tables 12, 13, and lU). The combustible gas readings were most
extreme in this respect, with 86.2/0 of the samples containing less t Jan iS
combustible gas by volume, whereas 12.3$ of the samples contained 2% or more
combustible gas and only 1.^ of the samples had combustible gas concentra-
tions between 10 and 2h.9%. This polarization of sample distribution is
probably due to the tendency of refuse-generated gas to well up in specific
areas rather than uniformly over the entire landfill site. This could be due
to the fact that certain areas on the landfill are less restrictive of gas
flow and act as chimneys for gas release, or to some characteristic of the
refuse. This tendency of gas to occur in isolated areas in the cover mate-
rial could be useful when vegetating these sites. By locating the areas
where the gases are present, high concentratibns can be avoided and the loss
of expensive trees and shrubs can be minimized.
Data for soil gas composition on the Edgeboro Landfill indicated a
strong correlation between the presence of landfill gases in the soil and the
poor growth of existing vegetation. The gas samples were taken from a depth
near or below the interface between the refuse and the cover material TM.
indicates that the presence or absence of landfill gases in the cover'mate-
rial was not a function of the depth of the cover but rather a ftactioTof
the state of decomposition or some other characteristic of the refuse Th«
sc o e refus
tendency of areas of soil covers saturated with landfill gases to be
than areas which did not contain landfill gases could £ £e to soil eroon
brought about by lack of protective vegetation over the gas -saturated Seas?
The Edgeboro data also indicate that severe contamination of the soil
atmosphere by landfill gases was localized and stable on the undisturbed
surface of the landfill during the fifteen month period of soil aSpheric
sampling. The large size of some of the existing trees in the areas P™
taining little or no soil landfill gas indicateftJat the^e areS have
probabOy been stable with respect to gas contamination for a number of years.
A considerable amount of effort and money could be saved when vecetati™
fo^d^^ fomer,,landfi11 *«re high concentrations of la^dfm glsefare g
found to occur in the soil cover by not planting at these location!.
Most of the tree deaths on the Edgeboro experimental screening areas can
100
-------
be attributed to factors other than landfill gas (especially on the control)
Low soil moisture, transplanting difficulties, animal damage and winter
injury can explaj^n many of the deaths.
Rhododendron suffered the greatest number of deaths all of which were
attributable to lack of soil moisture or winter injury. Several of these on
the experimental plot had landfill gas in the root zone, however, the gas was
only detected after these rhododendrons had died. The demise of eight of the
ten dead hybrid poplars can also be attributed to lack of soil moisture.
These trees, six on the experimental and two on the control, had succumbed
during the driest part of the summer of 1977 when the soil moisture reached
5.5% on the experimental plot and 6.0% on the control. No other species
appeared to be as adversely affected by the low soil moisture as were these
two.
Since black gum and sweet gum had been grown in containers in the nur-
sery, their root systems were rather small at the time of planting, resulting
in the death of several replicates of each species on the experimental plot
due to lack of water. One replicate of each succumbed on the control plot
also from low soil moisture. '
Damage to several euonymus trees by rabbits resulted in severe cambial
disruption causing the death of five replicates on the experimental plot and
poor growth of most of the others on the experimental and control plots.
The species which were very tall (12-15') at the time of planting (i.e.
American sycamore, weeping willow and green ash) suffered from acute water
deficiencies on the experimental plot apparently due to their large size
Many American sycamore and weeping willow trees died back and sprouted from
the lower trunk and root collar during the first growing season (1976),
whereas those on the control plot grew normally and suffered verv little
dieback.
. Although landfill gas was not significantly correlated with death of
trees, in a number of instances the carbon dioxide concentration at one
foot Beneath a recently dead Norway spruce was 2.8% and under a dead sweet
gum 10%. On the other hand, landfill gases were consistently associated with
death of trees in one landfill gas-barrier technique where carbon dioxide and
methane were much higher than in the landfill screening area. Apparently,
gas concentrations in most locations on the screening area were not high
enough to cause tree death.
Although landfill gas concentrations in the experimental plot were not
high enough to account for actual death of many of the plants, they were of
adequate magnitude to detect the order of relative tolerance of the surviving
trees as listed in Table 25. This listing resulted from a consideration of
four tree variables including leaf and root biomass, shoot length (1976 and
1977) basal stem area.
It is interesting that of the nine most tolerant species, only three
i.e. black gum, bayberry and pin oak, (73) have been reported to be able to
withstand low oxygen tension in the soil, one of the criteria for selecting
101
-------
experimental species (Table 3). However, seven of these most tolerant species
were three feet or less in height when planted, whereas seven of the last ten
species in Table 25 were six feet or taller when planted. Obviously, the size
of the tree as well as the biological ability of species to withstand low oxy-
gen is important in selecting vegetation for completed sanitary landfills.
In order to assess the role of the various soil variables in predis-
posing these species to landfill tolerance, multiple regression analysis was
performed for data from American basswood (the species present in both types
of experiments) for the four tree variables (shoot length, leaf weight, root
biomass, basal area). Results indicated that the soil variables, including
oxygen, carbon dioxide, temperature, moisture content and bulk density ex-
plained a significant portion (95% C.L.) of the variability in the tree
responses to landfill conditions. Examination of the quadratic effects of
these variables did not result in an increase in the coefficients of deter-
mination (R2); however, when the interactive and reciprocal effects were
added to the models, the interactions: moisture content with carbon dioxide,
and bulk density with carbon dioxide, as well as the reciprocal of carbon
dioxide to the fourth power resulted in a significant increase in the coef-
ficient of determination above that for the linear model.
Regression equations were computed for each of the four variables with
respect to American basswood. The equation for shoot length (equation 2,
page 84) indicates that the significant soil variables which explain 53% of
the variability are carbon dioxide, temperature, bulk density, oxygen and
moisture content. The negative coefficients for the first three soil vari-
ables indicate that high levels of these variables are correlated with a de-
crease in shoot length of American basswood trees while the positive coeffi-
cients for oxygen and moisture content correspond to an enhancement of growth
at high levels and a detrimental effect at lower levels of oxygen and
moisture content.
In that the reciprocal and interactive effects of the soil variables
increased the R2 value by 22% for leaf biomass, they were included in the
final regression model for leaf biomass (see equation k, page 85). The
significant independent variables temperature, bulk density, the interaction
of moisture content with carbon dioxide and the reciprocal of carbon dioxide
to the fourth power explained 63% of the variability. High levels of all
these variables correspond to a decrease in leaf biomass in that the regres-
sion coefficients are negative. The interaction of moisture content with
carbon dioxide shows that for the same concentration of carbon dioxide, the
leaf weight of basswood is different for different levels of moisture content.
The reciprocal effect of carbon dioxide illustrates that at low carbon diox-
ide concentrations, a small increase in concentration corresponds to a large
decrease in leaf weight, whereas at higher carbon dioxide levels, leaf weight
changes very little with changes in carbon dioxide concentration.
Thirty-nine percent of the variability in root biomass can be attributed
to the soil variables temperature, bulk density and moisture content leaving
a considerable amount of the variability unexplained. In that the variance
in the root biomass among basswood trees is large compared to the variance
among the screening areas and the gas-barrier techniques, it is not sur-
102
-------
prising that only a small portion of the variability could be accounted for
by the independent soil variables. The large variance among trees can be
partially explained by the sampling method. The method of sampling roots
for the present study, i.e. taking only one sample per tree, is subject to
a large amount of error in that the likelihood of collecting widely differ
ent biomass for trees growing under the same conditions is high. This stems
from the fact that one sample collected from a particular tree may have
purely by chance, been taken from a portion of the root system high in root
•biomass while a sample from another tree may have come from an area of low
biomass. This problem can be partially overcome by sampling roots from two
or more areas around a particular tree.
The significant effects in the equation describing the basal stem
cross-sectional area response of American basswood, with an R2 of fiftv three
percent, were bulk density, the interaction of bulk density with carbon
dioxide, and the reciprocal of carbon dioxide to the fourth power Since the
regression coefficient for each of these effects was negative, an*increase in
the value for these significant soil variables corresponds to a decrease in
the basal area. The significant interaction effect illustrates that at a
particular level of carbon dioxide, the difference in basal area is not the
same for different levels of bulk density. The significant reciprocal effect
for carbon diocide shows that a low C02 concentration (i.e. 0-5-*) a «m*ll
increase in concentration results in a large decrease in the basal area
vhereas at higher concentration (i.e. 5.30* C02), an increase in carbon'
dioxide corresponds with a small decrease in basal area. Rajappan (120) has
shown that root growth of red kidney bean was completely inhibited at carbon
dioxide concentrations of 5.5*. On the other hand, cotton seedlings grown
in hydroponic solution were able to make optimum growth with 10* carbon
dioxide present, provided at least 7.% oxygen was present (52)T
Apparently the variability within each basswood tree for shoot length
and leaf weight has been provided for adequately by collecting sS and^our
measurements per tree respectively, because the variance of tRese twT
variables for a particular tree is small compared with the variance among
tr*5?' Conse1uently> the R2 values for shoot length (53*) and leaf weicht
(63jt) are considerably higher than that for rootbicniif aS) vSre^nf
sample per tree was collected. VJW *nere one
In that there is only one measurement possible for the cross-sectional
^±t^fa«ow?hPSi^r,tree^itS ^ ShOUld reP~*ent very ^11 t£
amount of growth which that particular tree has produced However since
^calculation of cross section basal area is dependent upon the tree di-
ameter, then any error in the diameter measurement would result in an
erroneous basal area. Furthermore, when the diameter measurement is used
for the calculation of basal area, a circular cross section is assumed.
This is indeed an invalid assumption in that several of the trees are obvi-
ously not circular. Despite the high R2 ^^ (53^ for basal ^
^f^v*? S*!811^' S0me °f the ™«*Plaliied variability can most likely be
attributed to the non-circularity of some of the trees.
Despite the correlation of carbon dioxide with the growth of American
basswood, higher R^ values may be obtainable by placing fhe^ifgat coSL
103
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tion samplers at a depth comparable to the depth of the root system. This
depth was found to be approximately six inches on the experimental plot and
eight inches on the control plot. For the present study, gas samplers were
twelve inches below the soil surface. Since the average root depth was four
to six inches above the depth of the samplers, the gas concentration in the
root zone was not precisely measured. However, since carbon dioxide cor-
relates so well with poor growth, apparently the carbon dioxide at twelve
inches was related to the concentration in which the roots were growing.
Until now, oxygen has not been considered in the discussion of soil
factors and their effect on tree growth since oxygen became a significant
effect in only one of the four descriptive equations. The values for oxygen
correlated very highly (r = -.938) with those for carbon dioxide. Since
carbon dioxide was slightly better correlated with growth than oxygen, it
was entered into the majority of the equations and oxygen was omitted.
However, the absence of oxygen in the equation describing the variability
in growth must be interpreted with care. Since it is impossible to describe
the effects of each of these gases separately any discussion of the effects
of high carbon dioxide concentration on growth is confounded with the effects
of low oxygen.
Methane gas concentrations on the experimental plot screening area
averaged approximately one percent of the soil gas atmosphere at a depth
of one foot. Since this concentration is low, methane was not a significant
factor in explaining the variability in the tree responses. The low methane
concentration may be due to the action of Pseudomonas chromobacterium in the
landfill cover soil which utilizes methane as a source of carbon in its
metabolism (70). Oxygen is also required during the metabolism of these
bacteria which ultimately produce carbon dioxide and release it to the
surrounding soil. Therefore, the action of these bacteria in the landfill
cover-soil results in the production of carbon dioxide at the expense of
oxygen and methane. This reaction may be significant in that our studies
indicate that methane is innocuous to tomato plants if oxygen is not limiting,
whereas carbon dioxide has a detrimental effect on growth. If activity of
these bacteria can be inhibited, then less carbon dioxide will be present in
the landfill soil and the vegetation growing in this soil may have a better
chance to survive.
The nature of the soil strata (i.e. consisting of ten year old refuse
lying beneath two feet of soil) and perhaps the higher soil temperatures
and sand content on the experimental landfill plot helped promote drying
of the soil. Normal capillary water movement is restricted in such a soil
structure to the top two-feet enabling the roots to obtain additional water
only from irrigation or rainfall, and not from deeper soil layers. The soil
structure on the control plot is closer to normal with two feet of soil
spread over virgin land. Here, capillary action can help supply water to the
roots under low moisture conditions. In addition', the slope of the experi-
mental plot was about two percent whereas that of the control was one percent,
promoting more runoff on the experimental plot and resulting in less water
percolation and ultimately a lower soil moisture content. If the rate of
transpiration is measured on both plots for particular species along with
soil moisture content through time, rate of soil moisture loss relative to
10U
-------
the transpiration rate can be calculated for both plots. If these rates are
proportional on the control plot and not proportional on the experimental
plot, then some of the water was perhaps lost from the experimental plot soil
by processes other than transpiration.
This could imply one of two processes: first, that more water is T>erco
lating through the two- foot soil layer on the experimental plot and beinc
lost to the refuse layer below and that on the control plot the undisturbed
soil beneath the top two feet is slowing down percolation; second that on
the control plot, the deeper soil permits capillary water movement upwards
toward the dryer surface layer where the roots are located and that on the
experimental plot where only two feet of soil lies above thirty feet of
refuse, these deeper soil layers are not present to facilitate such capil-
lary action. Further studies may show whether or not these relationships
are valid. *
The trees on the control plot produced more leaf biomass than those on
the experimental plot, causing more of the smaller trees and shrubs as well
as the soil to be shaded to a greater extent on the control plot. This may
have tended to reduce the transpiration rate of the shaded plants and thuT
the rate of evaporation from the soil surface to lessen the water demand on
the control plot. In that soil moisture content has contributed
significantly to explaining the variability in equations two (page 8U) and
five (page 85) let us examine it further.
,4v i e^erlmentf Pjot ™s ^o ^re exposed to the elements and more
likely to be subjected to stronger winds than the control. This could place
an even greater demand f&r water on the trees growing in the experimental
plot so that the evapotranspiration rate would be enhanced at the expense of
lower soilToisture
The direct relationship of soil moisture
brought out by the positive'regression
ta
equations two and five showing that when moisture content was incased the
American basswood trees responded by increasing growth, A^hou^ Sis rela!
tionship is significant when all the American basswood data is^cSded in
the analysis, where moisture content was highest (in clay/vents to«2? ^he
growth of basswood was the poorest, i.e. t£ reverse of^STprevI^'
stated relationship. This supports the positive relationship beSe^ grovth
and soil moisture content in that the regression coefficient is p^SiS
despite the reverse relationship in the clay/ vents trench. Positive,
Why then is the high moisture content in the clay/vents trench asso-
ciated with the poorest growth? To answer this question it is necessary to
recall that water is one of the products of decomposition of the organic
matter in refuse (21). In addition it is also produced by the methane
utilizing bacteria (70). It travels along with'the otoer^o^osmmal
gases and since both carbon dioxide and methane were high in this
presumably the high moisture content resulted from wate™ vapor m
with these decomposition gases. The carbon dioxide concentratim
significant factor in the regression equation calculated for
105
-------
leaf weight and basal area for American bassvood and had a negative coef-
ficient, illustrating the detrimental effect of carbon dioxide on American
basswood growth. Therefore, the high carbon dioxide in the clay/vents trench
appeared to have contributed largely to the poor growth of these trees de-
spite the high moisture content.
Lack of soil moisture might have had an effect not only in reducing
water uptake by plants on the experimental plot and ultimately reducing
productivity, but also by reducing the assimilation of very soluble nutrients
such as nitrogen. Although the leaf tissue was not analyzed for nutrient
content during the present study, future analysis will make possible a
better understanding of the effects of landfill soil environment on nutrient
uptake and assimilation.
The soil nutrient levels were also found to be influenced by the land-
fill environment. The ratio of 1103: NHjJ on the experimental and control
screening areas were identical following the application of fertilizer in
the spring of 1977; however, by November of 1977, the NO^rNHt ratio on the
control was more than two times greater and significantly different from the
ratio on the experimental plot indicating one or both of two things: either
more ammonium nitrogen was converted to nitrate on the control plot because
of the higher oxygen concentration in the soil on the control plot, or
nitrate on the experimental plot was reduced to ammonium due to the utili-
zation of the oxygen portion of nitrate in the metabolism of soil bacteria
(117). This reduced the amount of nitrate in the soil and could result in a
lower NO§:NH£ ratio as exhibited on the experimental plot.
The NO§:NHi| ratio in the clay/vents trench where the oxygen concentra-
tion was h.3%, was more than two times less than the other gas-barrier
techniques where the oxygen was 16.3$ or greater. The same two possibil-
ities as described above most probably contributed to these phenomena.
The manganese content in the experimental and control screening areas
as well as in six of the seven gas-barrier techniques averaged approximately
10 ppm. However, in the clay/vents trench, -where the oxygen concentration
averaged ^.3$» the manganese reached b$ ppm. These relationships indicated
that at oxygen concentrations of 17.8$ (i.e. on the experimental screening
area), free manganese does not increase in the soil. However, when the
average oxygen concentration is U.3$ (i.e. in the clay/vents trench) then
manganese is significantly increased in the soil. Manganese available to
plants is reportedly significantly increased in soils flooded for short
periods of time (117).
Considering the nutrient changes described above, it is apparent that
at oxygen concentration of 17.8$ on the experimental plot, a slight reduc-
tion in the ratio of nitrate to ammonium nitrogen is occurring (Table 8)
compared to the control where the oxygen concentration is 19.7$ and that
when the oxygen concentration reaches ^.3$ (in clay/vents trench), oxides
of manganese are also reduced, increasing the free manganese in the soil
(Table 33).
Because the pH of the soil in the clay/vents trench was very low
106
-------
(5.0) the high manganese content may have been toxic to the plants in the
trench and contributed to their demise. One recommendation to help lower the
availability of manganese is to lime the soil, thereby raising the pH and
decreasing the likelihood of manganese toxicity to plants.
The effectiveness of each gas-barrier technique in preventing methane
gas migration into the trenches may be evaluated by considering the ratio
between the methane concentrations around the periphery of the trench and
those inside the trench. In the gravel/plastic/vents trench and clay barrier
trench, the ratios are 207:1 and 5^:1 respectively, indicating that these
trenches have functioned effectively in keeping out methane gas. On the
other hand, for the clay/vents trench, the 1:1 ratio indicated that this
gas-barrier technique was not effective in preventing the migration of
methane from the refuse into the trench.
No gas measurements were made in the soil immediately adjacent to either
of the two mounds on the experimental plot. However, methane or elevated
carbon dioxide levels were never detected in either mound. Furthermore, the
average carbon dioxide concentration on the experimental screening area
surrounding these mounds was six percent indicating that both mounds func-
tioned successfully in preventing gas migration.
Interpreting the effectiveness of each gas-barrier technique is not as
straightforward as it may first appear. Despite the previously presented
ratios between gas outside and gas inside the trenches, the concentrations
below the trenches were not measured and may differ from one trench to
another. In addition there is no way to determine if the clay barrier below
the clay/vents trench has remained intact. Although there are not obvious
signs of refuse settlement around this trench, small amounts of settlement
may have split the clay barrier allowing the upward movement of gases into
the soil in the trench. This might explain the high methane and carbon
dioxide in this trench. Future experiments with gas-barrier techniques
should include more than one application of each technique in order to make
adequate assessment of effectiveness in preventing gas migration. In this
study only one replicate of each technique was employed.
Another way of assessing the effectiveness of each barrier technique was
by the growth of the two species in each of these areas. For the same three
techniques which prevented landfill gas from contaminating the soil, analysis
of variance showed growth of American basswood significantly greater (99)6
C.L.) than the experimental screening area which acted as the control for
the barrier techniques. Because of the large variability in growth responses
of Japanese yew within each technique no significant differences were found
between the techniques and the experimental screening area for this species.
Presumably, the great variability in Japanese yew growth was partially due
to planting only four replicates per technique instead of six as were planted
for American basswood.
Carbon dioxide contamination in the root zone of tomato plants in solu-
tion culture was toxic when the concentration of C02 averaged 17.0% during
the experimental period. When C02 concentrations averaged 8.8% or less no
symptoms were observed, indicating that there was a threshold level between
107
-------
9 and 11% at which COg became toxic trader these experimental conditions.
Tomato plants exposed to 17$ C02 exhibited progressive chlorosis and abscis-
sion of the lower leaves, adventitious root development, swelling of the stem
near the nodes, chlorosis of the entire plant, and a reduction in the growth
rate. Complete symptom development was observed on all plants by the 17th
day of fumigation. Exposing tomato roots to concentrations of CC>2 between
25 and 36$ resulted in earlier and more severe symptom development on tomato
plants than did 17$ C02- These higher C02 concentrations caused some of the
plants to wilt after only three days of fumigation, and some plants never
recovered. The other symptoms were fully expressed on all plants given 26
to 27$ C02 by the tenth day of fumigation and on plants given 3k to 38$ C02
by the eighth day of fumigation.
These findings are consistent with what is reported in the literature.
Erickson (kk) in 19^6 found that 28$ C02 in the root zone severely reduced
the growth rate of tomato plants. The symptom development observed in this
experiment was also similar to that observed by Erickson on plants exposed
to low 02 and/ or high C02 in the root medium. This type of symptom develop-
ment was also reported by Jackson (75) in 19^8 and Kramer (Qk) in 1951, on
tomato plants grown in poorly aerated growth media.
No interaction was observed among 02, C02 and CH^ when they occurred
together in the root zone in terms of symptom development on tomato plants.
When the C02 was held at 27$, 02 at either 5.-5 or 16$ caused no differences
in symptom development. Plants exposed to 3^ to 38$ C02 alone exhibited the
same symptom development as plants exposed to 3k to 38$ C02 with ^3$
Exposing the roots of tomato plants to 1*3$ CHi^ for an 8-day period
resulted in no measurable adverse effects, whereas a 12-day exposure resulted
in a decline of the tomato plants concomitant with a decrease in 02 concen-
tration in the culture vessels. This decrease in 02 is believed to be due
to the activity of methane-utilizing microorganisms. Hoeks (70) in 1970 also
reported that exposing soil to high concentrations of CH^ resulted in
eutrophication by the second week of exposure.
Tomato plants are known to be sensitive to poor soil aeration and will
exhibit characteristic symptoms when so exposed (kk, 75, 8U). These symptoms
include: adventitious root development, swelling of the stem near the nodes,
progressive chlorosis and abscission of the lower leaves, reduction in growth
and an epinastic curvature of the leaf petioles. Such symptoms were dupli-
cated exactly when the 02 concentrations decreased in the cultures fumigated
with 1*3$ CHU. However, the plants exposed to high concentrations of C02
exhibited less extensive adventitious root development, less swelling of the
stem and little or no epinastic curvature. Chlorosis often involved the
entire plant rather than just the lower leaves, and in some cases the entire
plant wilted after only a few days of exposure. 'This indicates that C02
may damage tomato plants by means of a mechanism different from that through
which low 02 concentrations in the root zone causes plant damage.
Sugar maple was intolerant of flooding as evidenced by the statistically
significant decrease in transpiration rate after only one day of flooding
108
-------
and the loss of all leaves by the termination of the experiment. Red maple
seedlings were more tolerant of flooding than were more tolerant of flooding
than were sugar nfeples, their transpiration rate did not decrease until the
l*2nd day of flooding and this decrease was not statistically significant.
The lower half of the leaves on the flooded red maples were chlorotic by the
end of the experiment but this did not influence the stomatal diffusion
because the porometer readings were taken only on the uppermost leaves. The
fact that red maple is more tolerant of flooding than sugar maple has been
reported in the literature (6l).
Flood tolerance has been attributed to more than one adaptive mechanism
in several species (72). The adventitious root development and swelling of
lenticels observed on the flooded red maples in this experiment have been
found to occur on many other "flood tolerant" species and are believed to
contribute to flood tolerance to some degree. Such morphological adaptations
were not observed on the red maples fumigated with simulated sanitary land-
fill gas mixtures. This is not surprising since adventitious root develop-
ment is dependent upon the presence of water and lenticel opening requires
high humidity near the stem. Other adaptations which are believed to con-
tribute to flood tolerance which are not as water dependent include the
ability to withstand elevated levels of C02 in the soil (72) and to undergo
anaerobic root respiration without the production of inhibitory concentrations
of ethanol. Mechanisms such as these could explain why the differences be-
tween the two species were more pronounced in their response to flooding than
to soil contamination with simulated landfill gas. The inability to develop
adventitious roots and to permit opening of the lenticels in response to
landfill gas contamination would reduce the advantage enjoyed by flood
tolerant species, whereas, other mechanisms contributing to flood tolerance
such as the ability to withstand elevated levels of CC>2 in the soil or under-
go anaerobic respiration in the roots which are not inhibited by lack of
water and would continue to supply some protection.
Considering these factors, red maple might be a better choice as a tree
to plant on a completed sanitary landfill than sugar maple. The ability to
withstand flooding might be a good characteristic for a tree to have since
uneven settlement of the refuse can wreak havoc with surface drainage,
creating ephemeral ponds. The greater ability of red maple than sugar maple
to withstand the presence of C02 and CH^ in the soil was not as dramatic as
the ability to withstand flooding. Being less sensitive to these gases
red maple could develop a more extensive root system giving it a competitive
advantage over sugar maple whose root development would be more likely to be
inhibited by high C02 and CIfy in the soil.
109
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SECTION 8
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
. REPORT NO.
EPA-600/2-79-128
3. RECIPIENT'S ACCESSION NO.
4. TITLE ANDSUBTITLE
ADAPTING WOODY SPECIES AND PLANTING TECHNIQUES
TO LANDFILL CONDITIONS
Field and Laboratory Investigations
5. REPORT DATE
August 1979 (issuing Date)
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Ida A. Leone, Franklin B. Flower, Edward F. Gilman
and John J. Arthur
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Cook College, Rutgers University
New Brunswick, New Jersey 08903
10. PROGRAM ELEMENT NO.
1DC818. SOS #1, Task 3k
11. CONTRACT/GRANT NO.
R 803762-02-3
12. SPONSORING AGENCY NAME AND ADDRESS
Municipal Environmental Research Laboratory—Cin., OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 1*5268
13. TYPE OF REPORT AND PERIOD COVERED
January 19?6 - September 1978
14. SPONSORING AGENCY CODE
EPA/600/14
15. SUPPLEMENTARY NOTES
Robert E. Landreth, Project Officer 513/684-7871
16. ABSTRACT
A study was undertaken to determine which tree species can best maintain themselves
in a landfill environment; to investigate the feasibility of preventing landfill gas
from penetrating the root zone of selected species by using gas-barrier techniques;
and to identify the (those) factor(s) which are most important in maintaining
adequate plant growth on completed sanitary landfills. Ten replicates of nineteen
woody species were planted on a ten-year old completed sanitary landfill and five
gas-barrier systems were constructed. Of the nineteen species planted on the landfill
black gum proved most tolerant and honey locust least tolerant to anaerobic landfill
conditions. Of the five gas-barrier systems tested, three proved effective in pre-
venting penetration of gas into the root systems of the test species. Investigations
into the effects of C02 and Glfy contaminated soil indicated that red maple is more
tolerant to the presence of these gases than is sugar maple.
An investigation of the effects of carbon dioxide (C02) and/or methane (Cffi^) contam-
inated soil atmospheres on the growth of tomato plants indicated that C02 was toxic
to tomato roots in a low 02 soil atmosphere, whereas CHlj. was innocuous under the
same conditions. No interaction was observed between C0? and CH. in terms of damage
to tomato plants.
7.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COS AT I Field/Group
Methane
Carbon dioxide
Vegetation
Solid vaste management
Sanitary landfill
Landfill gas
13B
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
134
20. SECURITY CLASS (Thispage)
Unclassified
22. PRICE
EPA Form 2220-1 (9-73)
122
«O.S. GOVERNMENT PRINTING OFFICE: l<"4-657-oso/S3es
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