Hydrogeochemical Characteristics of Groundwater Highly Polluted with Nitrate in an Agricultural Area of Hongseong, Korea

Hyun-Su Kim,So-Ra Park

doi:10.3390/w8080345

Abstract

The hydrogeochemical characteristics of groundwater, in an area where widespread contamination by nitrate ( NO 3 − ) was anticipated, were studied using traditional geochemical investigation and multivariate statistical analysis. Widespread NO 3 − contamination as high as 67.2 mg/L as NO3–N was observed, and positively correlated with that for chemicals ( Cl − , major cations) with surface origin. Principal component analysis (PCA) revealed that three processes affected groundwater chemistry of the area: (1) leaching of pollutants from the ground surface; (2) reduction of NO 3 − in areas with low dissolved oxygen (DO); and (3) ingress of low NO 3 − deep groundwater. Five sample groups were identified from cluster analysis, and analysis of land use patterns around each group showed that fate and distribution of NO 3 − contamination were mainly controlled by surface topography and predominant land use type. The highest NO 3 − concentrations were associated with confined livestock feeding operations in hilly terrain areas, where infiltrating water also had high DO. Lower NO 3 − concentrations found in the lowland flat areas were thought to be due to either reducing conditions in rice paddies leading to N attenuation or drawing in of deep groundwater by pumping to meet agricultural needs during periods of low rainfall.

Highlights

Groundwater is an important water resource that is used as drinking water by more than 20%of the global population, and the share of groundwater in global water use is quickly rising [1,2,3]. pristine groundwater, in general, is thought to have had better water quality than surface water sources, such as rivers, streams, and lakes [4], increased impact from human activities has been undermining the quality of groundwater over the past few decades
It was reported that the concentrations of K+ in pristine groundwater were less than 5 mg/L, and the value higher than that indicated the possibility that groundwater was affected by contaminants, such as sewage and fertilizer [35]
PC3 showed a positive correlation with the aforementioned chemical species indicating water–rock interaction and a negative relationship with of Cl− and NO3−, which seems to indicate that PC3 was related to groundwater chemistry change due to natural mineralization (Table 3; Figure 3b)

Summary

Introduction

In general, is thought to have had better water quality than surface water sources, such as rivers, streams, and lakes [4], increased impact from human activities has been undermining the quality of groundwater over the past few decades. NO3− contamination of groundwater has been a serious environmental concern in South Korea over the last three decades. NO3− contamination is mainly caused by overapplication of organic and inorganic fertilizer and improper disposal of animal wastes. The most common form of livestock rearing in Korea is very intensive, where hundreds or thousands of cattle, pigs and poultry are raised in very confined and crowded conditions, and animal waste generated from these facilities are not properly collected or treated in many cases.

Methods

Results

Discussion

Conclusion