Spatial and Temporal Variations of Nitrogen and Phosphorus in Surface Water and Groundwater of Mudong River Watershed in Huixian Karst Wetland, Southwest China

Liangliang Huang,Zupeng Wan,Zhangnan Li,Linyan Pan,Junlei Han,Zhiqiang Wu,Junfeng Dai

doi:10.3390/su131910740

Liangliang Huang, Zupeng Wan + Show 5 more

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https://doi.org/10.3390/su131910740

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Journal: Sustainability	Publication Date: Sep 27, 2021
Citations: 1	License type: CC BY 4.0

Affiliation: Guilin University of Technology

Abstract

When considering the factors affecting the spatial and temporal variation of nitrogen and phosphorus in karst watersheds, the unique karst hydrogeology as an internal influencing factor cannot be ignored, as well as natural factors such as meteorological hydrology and external factors such as human activities. A watershed-scale field investigation was completed to statistically analyze spatial and temporal dynamics of nitrogen and phosphorus through the regular monitoring and collection of surface water and shallow groundwater in the agricultural-dominated Mudong River watershed in the Huixian Karst Wetland over one year (May 2020 to April 2021). Our research found that non-point source pollution of nitrogen (84.5% of 239 samples TN > 1.0 mg/L) was more serious than phosphorus (7.5% of 239 samples TP > 0.2 mg/L) in the study area, and shallow groundwater nitrogen pollution (98.3% of 118 samples TN > 1.0 mg/L) was more serious than surface water (68.6% of 121 samples TN > 1.0 mg/L). In the three regions with different hydrodynamic features, the TN concentration was higher and dominated by NO3−-N in the river in the northern recharge area, while the concentrations of TN and TP were the highest in shallow groundwater wells in the central wetland core area and increased along the surface water flow direction in the western discharge area. This research will help improve the knowledge about the influence of karst hydrodynamic features on the spatial patterns of nitrogen and phosphorus in water, paying attention to the quality protection and security of water in karst areas with a fragile water ecological environment.

Highlights

Nitrogen and phosphorus from non-point source pollution caused by agricultural activities have led to the degradation of water quality and the destruction of water ecosystem in watersheds, a worldwide environmental concern [1,2,3]
Water is at high risk of nitrogen and phosphorus pollution, whether in bare carbonate areas with a thin or scarce protective soil layer or in covered carbonate areas with high intensity of human agriculture and living activities
Non-point source pollution of nitrogen and phosphorus in karst areas have been reported across the world, for example, in China [4,10,11], Mexico [12], United

Summary

Introduction

Nitrogen and phosphorus from non-point source pollution caused by agricultural activities have led to the degradation of water quality and the destruction of water ecosystem in watersheds, a worldwide environmental concern [1,2,3]. Water is at high risk of nitrogen and phosphorus pollution, whether in bare carbonate areas with a thin or scarce protective soil layer or in covered carbonate areas with high intensity of human agriculture and living activities. The barren soil and limited land resources in the covered carbonate area lead to intensive human agricultural activities, as well as overuse of nitrogen and phosphorus fertilizers. All this results in the rapid spread of nitrogen and phosphorus pollution in aquifers. Non-point source pollution of nitrogen and phosphorus in karst areas have been reported across the world, for example, in China [4,10,11], Mexico [12], United

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