TY - JOUR
T1 - Residence times of groundwater and nitrate transport in coastal aquifer systems
T2 - Daweijia area, northeastern China
AU - Han, Dongmei
AU - Cao, Guoliang
AU - McCallum, James
AU - Song, Xianfang
PY - 2015/1/1
Y1 - 2015/1/1
N2 - Groundwater within the coastal aquifer systems of the Daweijia area in northeastern China is characterized by a large of variations (33-521mg/L) in NO3- concentrations. Elevated nitrate concentrations, in addition to seawater intrusion in the Daweijia well field, both attributable to anthropogenic activities, may impact future water-management practices. Chemical and stable isotopic (δ18O, δ2H) analysis, 3H and CFCs methods were applied to provide a better understanding of the relationship between the distribution of groundwater mean residence time (MRT) and nitrate transport, and to identify sources of nitrate concentrations in the complex coastal aquifer systems. There is a relatively narrow range of isotopic composition (ranging from -8.5 to -7.0‰) in most groundwater. Generally higher tritium contents observed in the wet season relative to the dry season may result from rapid groundwater circulation in response to the rainfall through the preferential flow paths. In the well field, the relatively increased nitrate concentrations of groundwater, accompanied by the higher tritium contents in the wet season, indicate the nitrate pollution can be attributed to domestic wastes. The binary exponential and piston-flow mixing model (BEP) yielded feasible age distributions based on the conceptual model. The good inverse relationship between groundwater MRTs (92-467years) and the NO3- concentrations in the shallow Quaternary aquifers indicates that elevated nitrate concentrations are attributable to more recent recharge for shallow groundwater. However, there is no significant relationship between the MRTs (8-411years) and the NO3- concentrations existing in the carbonate aquifer system, due to the complex hydrogeological conditions, groundwater age distributions and the range of contaminant source areas. Nitrate in the groundwater system without denitrification effects could accumulate and be transported for tens of years, through the complex carbonate aquifer matrix and the successive inputs of nitrogen from various sources.
AB - Groundwater within the coastal aquifer systems of the Daweijia area in northeastern China is characterized by a large of variations (33-521mg/L) in NO3- concentrations. Elevated nitrate concentrations, in addition to seawater intrusion in the Daweijia well field, both attributable to anthropogenic activities, may impact future water-management practices. Chemical and stable isotopic (δ18O, δ2H) analysis, 3H and CFCs methods were applied to provide a better understanding of the relationship between the distribution of groundwater mean residence time (MRT) and nitrate transport, and to identify sources of nitrate concentrations in the complex coastal aquifer systems. There is a relatively narrow range of isotopic composition (ranging from -8.5 to -7.0‰) in most groundwater. Generally higher tritium contents observed in the wet season relative to the dry season may result from rapid groundwater circulation in response to the rainfall through the preferential flow paths. In the well field, the relatively increased nitrate concentrations of groundwater, accompanied by the higher tritium contents in the wet season, indicate the nitrate pollution can be attributed to domestic wastes. The binary exponential and piston-flow mixing model (BEP) yielded feasible age distributions based on the conceptual model. The good inverse relationship between groundwater MRTs (92-467years) and the NO3- concentrations in the shallow Quaternary aquifers indicates that elevated nitrate concentrations are attributable to more recent recharge for shallow groundwater. However, there is no significant relationship between the MRTs (8-411years) and the NO3- concentrations existing in the carbonate aquifer system, due to the complex hydrogeological conditions, groundwater age distributions and the range of contaminant source areas. Nitrate in the groundwater system without denitrification effects could accumulate and be transported for tens of years, through the complex carbonate aquifer matrix and the successive inputs of nitrogen from various sources.
KW - Anthropogenic contamination
KW - Coastal carbonate aquifer
KW - Groundwater mean residence time
KW - Nitrate transport
KW - Seawater intrusion
UR - http://www.scopus.com/inward/record.url?scp=84956783262&partnerID=8YFLogxK
U2 - 10.1016/j.scitotenv.2015.08.036
DO - 10.1016/j.scitotenv.2015.08.036
M3 - Article
C2 - 26318690
AN - SCOPUS:84956783262
SN - 0048-9697
VL - 538
SP - 539
EP - 554
JO - Science of the Total Environment
JF - Science of the Total Environment
ER -