The fact that both exposure to air and the action of soil bacteria
contribute to the conversion of ammonia to nitrate is supported by
the ground water analyses. Ammonia was only detected at extremely
low levels in all wells with one notable exception, well WC-2 at Site
B. The fact that the downgradient well at Site B showed elevated
levels of ammonia while the downgradient well at Site A showed none
can be attributed to the fact that Site B was underlain by very sandy
soils that allowed the leachate to infiltrate into the ground water
very quickly. This allowed for very little interaction between the
leachate and the air or soil. Site A, on the other hand, had clay
soils and large pools of leachate that optimized the interaction
between leachate and the environment.

Most of the nitrate problems can be related to the fact that the
study sites accepted nutrient-rich grass clippings and allowed these
wastes to decay anaerobically. Numerous studies (Cole, 1994, Varsa,
1994, Richard, et. al., 1990 and Helfrich, 1992) have shown that when
yard waste composting is managed under controlled conditions that
encourage aerobic decomposition and restrict the amount of grass
waste, excessive nitrate and ammonia production does not occur.

Chloride levels in the downgradient wells at both study sites were
much higher than levels in upgradient wells. A similar situation was
noted in a study done by Varsa (1994). He attributed the increase┬ž
to high levels of chloride in the compost runoff and chloride's low
susceptibility to adsorption. Leachate samples taken from all four
sites indicated high levels of chloride. Chloride in the leachate
may originate from road salt picked up by vacuum collection trucks
along with leaf litter.   Another possible source is from plants that
have adsorbed chloride from the soil. As these plants decompose in
the compost piles, the chloride could then be released to the
leachate.

The sulfate levels recorded at Site A indicated that sulfate levels
were up to 10 times higher in the downgradient well LR-4 than the
levels found in upgradient well LR-l. At Site B, however, the
sulfate concentrations were about the same in all wells and no
significant increase in sulfate concentration was noted in any
downgradient wells. This can be explained by looking at the leachate
analyses for each site.   Site A had some of the highest sulfate
levels of any site with one recorded concentration of 880 mg/L. Site
B leachate had relatively low amounts of sulfate, around 65 mg/L.

Chromium and lead concentrations were found in almost all leachate
samples and some of the metal concentrations were quite high, well
above Wisconsin's ground water quality standards.    Previous studies
have shown the presence of heavy metals in yard waste compost
leachate. Lead levels ranging from 15 to 512 ug/L were detected in
the leachate from a leaf composting operation in New Jersey (Strom,
1986). Cole (1994) cites a study done by Kee (1962), that found the
water-solubility and mobility of several types of metals is greater
under conditions of low oxygen and low pH.    These conditions exist
within large piles of organic materials that are allowed to decay
anaerobically, such as at Sites A and D.    The most obvious source for