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Estimating Background and Threshold Nitrate Concentrations Using Probability Graphs
Author(s) -
Panno S.V.,
Kelly W.R.,
Martinsek A.T.,
Hackley K.C.
Publication year - 2006
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.1745-6584.2006.00240.x
Subject(s) - nitrate , environmental science , groundwater , effluent , spring (device) , fertilizer , environmental chemistry , population , soil water , organic matter , hydrology (agriculture) , precipitation , environmental engineering , chemistry , soil science , geology , organic chemistry , mechanical engineering , geotechnical engineering , demography , sociology , engineering , physics , meteorology
Because of the ubiquitous nature of anthropogenic nitrate () in many parts of the world, determining background concentrations of in shallow ground water from natural sources is probably impossible in most environments. Present‐day background must now include diffuse sources of such as disruption of soils and oxidation of organic matter, and atmospheric inputs from products of combustion and evaporation of ammonia from fertilizer and livestock waste. Anomalies can be defined as derived from nitrogen (N) inputs to the environment from anthropogenic activities, including synthetic fertilizers, livestock waste, and septic effluent. Cumulative probability graphs were used to identify threshold concentrations separating background and anomalous NO 3 ‐N concentrations and to assist in the determination of sources of N contamination for 232 spring water samples and 200 well water samples from karst aquifers. Thresholds were 0.4, 2.5, and 6.7 mg/L for spring water samples, and 0.1, 2.1, and 17 mg/L for well water samples. The 0.4 and 0.1 mg/L values are assumed to represent thresholds for present‐day precipitation. Thresholds at 2.5 and 2.1 mg/L are interpreted to represent present‐day background concentrations of NO 3 ‐N. The population of spring water samples with concentrations between 2.5 and 6.7 mg/L represents an amalgam of all sources of in the ground water basins that feed each spring; concentrations >6.7 mg/L were typically samples collected soon after springtime application of synthetic fertilizer. The 17 mg/L threshold (adjusted to 15 mg/L) for well water samples is interpreted as the level above which livestock wastes dominate the N sources.