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Hydrogeological Processes and Chemical Reactions at a Landfill
Author(s) -
Baedecker Mary Jo,
Back William
Publication year - 1979
Publication title -
groundwater
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.84
H-Index - 94
eISSN - 1745-6584
pISSN - 0017-467X
DOI - 10.1111/j.1745-6584.1979.tb03338.x
Subject(s) - leachate , alkalinity , environmental chemistry , nitrate , sulfate , organic matter , chemistry , dissolved organic carbon , groundwater , bicarbonate , carbonate , calcareous , aquifer , environmental science , geology , paleontology , geotechnical engineering , organic chemistry
Chemical and isotopic analyses were made of water from wells in and downgradient from a landfill to determine chemical and isotopic effects of generation and migration of leachate on ground water. The distribution and wide concentration range of oxygen and methane permit the delineation of an anaerobic zone, a regional oxygenated zone and an intermediate zone. The ratio of reduced nitrogen to nitrate indicates location of reducing fronts as the leachate migrates. The pH of the native ground water is low (≥5.0) primarily because of the low pH of rainfall and the lack of calcareous or other soluble minerals in the aquifer material. The pH is higher (∼6.6) in the leachate because of generation of carbon dioxide, ammonia, and methane. The native ground water has a low TDS (80 mg/l) while the leachate has an average TDS of 2800 mg/l and is primarily a NaHCO 3 type water. Sulfate concentrations are extremely low and H 2 S was not detected. We suggest that a major source of cations may be their exchange from the clays by the ammonium generated in the leachate. High concentrations of Fe and Mn are attributed to a source in the refuse but more important to reduction of oxide cements and coatings resulting from degradation of organic matter. The main source of bicarbonate is from organic degradation with minimal CO 2 from the soil zone. At one landfill site 52% of the total alkalinity is attributed to organic compounds, mainly organic acid anions. The δ 13 C of bicarbonate in the leachate is exceedingly heavy (+18.40 0 / 00 ) which results from fractionation during the formation of methane. The 10 per mil deuterium enrichment of water may be due to decomposition of deuterium‐enriched compounds and bacterial processes that preferentially consume the lighter hydrogen isotope.