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Land Management Impacts on Dairy‐Derived Dissolved Organic Carbon in Ground Water
Author(s) -
Chomycia Jill C.,
Hernes Peter J.,
Harter Thomas,
Bergamaschi Brian A.
Publication year - 2008
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2007.0183
Subject(s) - dissolved organic carbon , groundwater , environmental chemistry , environmental science , surface water , total organic carbon , anoxic waters , trihalomethane , denitrification , maximum contaminant level , water well , hydrology (agriculture) , san joaquin , water quality , environmental engineering , chemistry , water treatment , nitrogen , ecology , geology , soil science , geotechnical engineering , organic chemistry , biology
Dairy operations have the potential to elevate dissolved organic carbon (DOC) levels in ground water, where it may interact with organic and inorganic contaminants, fuel denitrification, and may present problems for drinking water treatment. Total and percent bioavailable DOC and total and carbon‐specific trihalomethane (THM) formation potential (TTHMFP and STHMFP, respectively) were determined for shallow ground water samples from beneath a dairy farm in the San Joaquin Valley, California. Sixteen wells influenced by specific land management areas were sampled over 3 yr. Measured DOC concentrations were significantly elevated over the background as measured at an upgradient monitoring well, ranging from 13 to 55 mg L −1 in wells downgradient from wastewater ponds, 8 to 30 mg L −1 in corral wells, 5 to 12 mg L −1 in tile drains, and 4 to 15 mg L −1 in wells associated with manured fields. These DOC concentrations were at the upper range or greatly exceeded concentrations in most surface water bodies used as drinking water sources in California. DOC concentrations in individual wells varied by up to a factor of two over the duration of this study, indicating a dynamic system of sources and degradation. DOC bioavailability over 21 d ranged from 3 to 10%, comparable to surface water systems and demonstrating the potential for dairy‐derived DOC to influence dissolved oxygen concentrations (nearly all wells were hypoxic to anoxic) and denitrification. TTHMFP measurements across all management units ranged from 141 to 1731 μg L −1 , well in excess of the maximum contaminant level of 80 μg L −1 established by the Environmental Protection Agency. STHMFP measurements demonstrated over twofold variation (∼4 to ∼8 mmol total THM/mol DOC) across the management areas, indicating the dependence of reactivity on DOC composition. The results indicate that land management strongly controls the quantity and quality of DOC to reach shallow ground water and hence should be considered when managing ground water resources and in any efforts to mitigate contamination of ground water with carbon‐based contaminants, such as pesticides and pharmaceuticals.