| 摘 要： |
A key to control sources of groundwater nitrogen pollution relies on improved understanding of nitrogen enrichment along with water recharge and its hydrological pathways. Employing the water stable isotope technique (delta D-H2O and delta 18O-H2O) combined with water chemistry analysis, this study investigated interactions of groundwater with surface water and identified potential recharge sources of groundwater in a typical agricultural basin with mixed land use types and agricultural intensification of Northeast China. A total of 48 groundwater and surface water samples and representative samples from potential nitrogen sources (piedmont plateau spring water, domestic sewage, atmospheric precipitation and ditch water) were collected. The Bayesian isotopic mixing model was performed to quantify proportional contributions of potential water recharge sources to groundwater. Results showed that limited interactions between surface water and groundwater occurred in the basin except for the headwater area. The proportional contributions of water recharge sources to groundwater varied with land use types. Groundwater in the forested area was primarily recharged by piedmont plateau spring water and atmospheric precipitation. In the town area, atmospheric precipitation was the major recharge source with the mean probability estimate of 46.2 %, and the contribution of domestic sewage should not be ignored (15.4 %). Besides the lateral recharge of piedmont plateau spring water (59.2 %) and atmospheric precipitation (36.7 %), ditch water for irrigation in rice paddies also contributed to groundwater to a lesser degree (4.2 %). In dry cropland, shallow groundwater was mainly from lateral recharge of piedmont plateau spring water (59.9 %), while deep groundwater recharge largely relied on atmospheric precipitation and the mean probability estimate was 74.9 %. This study provided an alternative to reveal hydrological pathways of groundwater nitrogen recharge in mixed land use basins with agricultural intensification. |
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