Intensive rice agriculture deteriorates the quality of shallow groundwater in a typical agricultural catchment in subtropical central China.
High nitrogen (N) concentrations in rural domestic water supplies have been attributed to excessive agricultural N leaching into shallow groundwater systems; therefore, it is important to determine the impact of agriculture (e.g., rice production) on groundwater quality. To understand the impact of agricultural land use on the N concentrations in the shallow groundwater in subtropical central China, a large observation program was established to observe ammonium-N (NH4-N), nitrate-N (NO3-N), and total N (TN) concentrations in 161 groundwater observation wells from April 2010 to November 2012. The results indicated that the median values of NH4-N, NO3-N, and TN concentrations in the groundwater were 0.15, 0.39, and 1.38 mg N L(-1), respectively. A total of 36.3 % of the water samples were categorized as NH4-N pollution, and only a small portion of the samples were categorized as NO3-N pollution, based on the Chinese Environmental Quality Standards for Groundwater of GB/T 14848-93 (General Administration of Quality Supervision of China, 1993). These results indicated of moderate groundwater NH4-N pollution, which was mainly attributed to intensive rice agriculture with great N fertilizer application rates in the catchment. In addition, tea and vegetable fields showed higher groundwater NO3-N and TN concentrations than other agricultural land use types. The factorial correspondence analysis (FCA) suggested that the flooded agricultural land use types (e.g., single-rice and double-rice) had potential to impose NH4-N pollution, particularly in the soil exhausting season during from July to October. And, the great N fertilizer application rates could lead to a worse NO3-N and TN pollution in shallow groundwater. Hence, to protect groundwater quality and minimize NH4-N pollution, managing optimal fertilizer application and applying appropriate agricultural land use types should be implemented in the region.
Key Laboratory of Agro-ecological Processes in Subtropical Regions and Changsha Research Station for Agricultural and Environmental Monitoring, Institute of Subtropical Agriculture, Chinese Academy of Sciences, No. 644, the Second Yuanda Road, Furong District, Changsha, Hunan, 410125, China.
Yi
Y
Wang
Yuyuan
Y
Li
Yong
Y
Li
Feng
F
Liu
Xinliang
X
Liu
Dianlin
D
Gong
Qiumei
Q
Ma
Wei
W
Li
Jinshui
J
Wu
D000383:Agriculture; D064751:Ammonium Compounds / Q000032:analysis; D002681:China; D004784:Environmental Monitoring / Q000379:methods; D005308:Fertilizers / Q000032:analysis; D060587:Groundwater / Q000737:chemistry*; D009566:Nitrates / Q000032:analysis; D012275:Oryza / Q000254:growth & development*; D012987:Soil / Q000737:chemistry; D014329:Tropical Climate; D014874:Water Pollutants, Chemical / Q000032:analysis; D060753:Water Quality; D014881:Water Supply / Q000706:statistics & numerical data
D064751:Ammonium Compounds; D005308:Fertilizers; D009566:Nitrates; D012987:Soil; D014874:Water Pollutants, Chemical