TY - JOUR
T1 - Effects of sludge disposal on groundwater nitrate concentrations
AU - Spalding, R. F.
AU - Exner, M. E.
AU - Martin, G. E.
AU - Snow, D. D.
PY - 1993/2
Y1 - 1993/2
N2 - More than 100 groundwater samples were collectd and analyzed for nitrate-nitrogen, δ15N of the nitrate, dissolved organic carbon (DOC), and chloride. Multilevel samplers and nested monitoring wells were located beneath and down-gradient from an irrigated cornfield on which human waste sludge was injected. The sampling delineated a 1.3 km × 0.3 km plume of nitrate contamination. Both the nitrate-nitrogen concentrations and the δ15N values within the plume's centroid were homogeneous. The levels were 34 ± 3 mg 1-1 and + 13.4 ± 1.2%, respectively. A retarding zone of clayey silt split the plume and separated the oxic water from the deeper anoxic water. Nitrate levels were lower in the anoxic water and declined rapidly with depth. The significant association (r = - 0.91) between increasing δ15N values and decreasing nitrate concentrations indicated that the nitrate was denitrified. High chloride concentrations in the anoxic zone beneath the retarding layer are thought to originate from the sludge storage lagoon and/or the sludge compost piles. Tritium and atrazine levels confirm that this is recent recharge water. Denitrification has utilized most of the original nitrate and DOC in the plume.
AB - More than 100 groundwater samples were collectd and analyzed for nitrate-nitrogen, δ15N of the nitrate, dissolved organic carbon (DOC), and chloride. Multilevel samplers and nested monitoring wells were located beneath and down-gradient from an irrigated cornfield on which human waste sludge was injected. The sampling delineated a 1.3 km × 0.3 km plume of nitrate contamination. Both the nitrate-nitrogen concentrations and the δ15N values within the plume's centroid were homogeneous. The levels were 34 ± 3 mg 1-1 and + 13.4 ± 1.2%, respectively. A retarding zone of clayey silt split the plume and separated the oxic water from the deeper anoxic water. Nitrate levels were lower in the anoxic water and declined rapidly with depth. The significant association (r = - 0.91) between increasing δ15N values and decreasing nitrate concentrations indicated that the nitrate was denitrified. High chloride concentrations in the anoxic zone beneath the retarding layer are thought to originate from the sludge storage lagoon and/or the sludge compost piles. Tritium and atrazine levels confirm that this is recent recharge water. Denitrification has utilized most of the original nitrate and DOC in the plume.
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U2 - 10.1016/0022-1694(93)90011-W
DO - 10.1016/0022-1694(93)90011-W
M3 - Article
AN - SCOPUS:0027334381
SN - 0022-1694
VL - 142
SP - 213
EP - 228
JO - Journal of Hydrology
JF - Journal of Hydrology
IS - 1-4
ER -