Regional Variability of Agriculturally-Derived Nitrate-Nitrogen in Shallow Groundwater in China, 2004–2014

Jing Li,Quanyan Tian,Shu Fang,Zhibin He,Pengfei Lin,Jun Du,Xi Zhu,Minmin Zhao,Liwen Zhao,Longfei Chen

doi:10.3390/su10051393

Abstract

Increasing diffuse nitrate loading of groundwater has long been a major environmental and health concern in China, but little is known about the spatial and temporal variability of nitrate concentrations in groundwater at regional scales. The aim of this study was to assess the spatial distribution and variation of nitrate-nitrogen (NO3−-N) concentrations in groundwater. We used groundwater quality monitoring data and soil physical characteristics from 21 agro-ecosystems in China for years 2004 to 2014. The results indicated that NO3−-N concentrations were highly variable in shallow groundwater across the landscape. Over the study period, most of the NO3−-N concentrations were below the World Health Organization permissible limit for drinking water (<10 mg N·L). NO3−-N concentrations in groundwater neither significantly increased nor decreased in most agro-ecosystems, but fluctuated with seasons. In addition, groundwater NO3−-N under purple soil (6.81 mg·L−1) and Aeolian sandy soil (6.02 mg·L−1) were significantly higher (p < 0.05) than that under other soil types, and it was medium-high (4.49 mg·L−1) under aquic cinnamon soil. Elevated nitrate concentrations occurred mainly in oasis agricultural areas of northwestern China, where farmlands with coarse-textured soils use flood irrigation. Therefore, arid and semi-arid areas are expected to sustain high NO3−-N concentrations in groundwater. Mitigation strategies can prevent this problem, and include control of N fertilizer input, balanced fertilization, proper rotation system, adoption of improved irrigation methods, and establishment of environmental policies.

Highlights

Anthropogenic activities across the world affect the quality of groundwater, and result in a severe problem for society [1]
Mean NO3−-N concentrations in groundwater at most of the monitored stations in the Northeast and South agricultural areas were below 2 mg·L−1 (HLA, SYA, CSA, HJA, TYA, YTA, QYA)
We found that nitrate concentration in groundwater did not increase under intensive cultivation and under the present rate of heavy fertilization in most typical agro-ecosystems of China Ecosystem Research Network (CERN) except for LZD and YGA (Figure 2)

Summary

Introduction

Anthropogenic activities across the world affect the quality of groundwater, and result in a severe problem for society [1]. It is expensive, and, in many cases, virtually impossible to clean up [8]. Because of those concerns, the U.S Environmental Protection Agency (U.S EPA) established a maximum contaminant level (MCL) of 10 mg·L−1 NO3− N in drinking water [9]. Studies have indicated that the Circum-Bohai-Sea Region, including the provinces of Beijing, Hebei, Henan, Shandong, Liaoning, Tianjin, and Shanxi, had high NO3−-N concentrations in groundwater, with an average value of 11.9 mg·L−1; about 34.1% of the groundwater exceeded the WHO (World Health Organization) limit of 10 mg·L−1 for drinking water [11]. Many studies suggested that 32.4% of wells in the middle of the Heihe River irrigation areas exceeded the limit of 10 mg NO3−-N L−1 [12]

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Discussion

Conclusion