Spatial Characteristics of Groundwater Chemistry in Unzen, Nagasaki, Japan

Abstract

Nitrate pollution in groundwater is a serious problem in Shimabara Peninsula, Nagasaki, Japan. A better understanding of the hydrogeochemical evolution of groundwater in vulnerable aquifers is important for health and environment. In this study, groundwater samples were collected at 12 residential and 57 municipal water supply wells and springs in July and August 2018. Nitrate (NO3−N) concentration at eight sampling sites (12%) exceeded Japanese drinking water standard for NO3 + NO2−N (10 mg L−1). The highest nitrate concentration was 19.9 mg L−1. Polluted groundwater is distributed in northeastern, northwestern, and southwestern areas, where land is used for intensive agriculture. Correlation analysis suggests that nitrate sources are agricultural fertilizers and livestock waste. Dominant groundwater chemistry is (Ca+Mg)−HCO3 or (Ca+Mg)−(SO4+NO3) type. Groundwater with higher nitrate concentration is of (Ca+Mg)−(SO4+NO3) type, indicating nitrate pollution affecting water chemistry. Principal component analysis extracted two important factors controlling water chemistry. The first principal component explained dissolved ions through water–rock interaction and agricultural activities. The second principal component explained cation exchange and dominant agricultural effects from fertilizers. Hierarchical cluster analysis classified groundwater into four groups. One of these is related to the dissolution of major ions. The other three represent nitrate pollution.

Use of Multivariate Statistical Analysis of Hydrochemical Data for the Identification of the Geochemical Processes in the Tirana-Fushe Kuqe Alluvial Aquifer, North-Western Albania

“…Principal component analysis (PCA) is a popular strategy for reducing dimensions of dataset, thus increasing the interpretability with minimal information loss. The way PCA operates is by generating new uncorrelated variables that enable the maximization of variance [Jolliffe and Cadima, 2016;Zainol et al, 2021;Nakagawa, 2021;Zhang et al, 2021]. Basically, the problem of defining the new dataset dimensions is reduced in a matrix decomposition, with eigenvalues/vectors interpretation described in many works [Beattie et al, 2021;Torokhti and Friedland, 2009;Gewers, 2021].…”

Activated Carbon and Coconut Coir with the Incorporation of ABR System as Greywater Filter: The Implications for Wastewater Treatment

“…The properties of wastewater are categorized into physical parameters, for instance, color, temperature, turbidity, and odor; chemical parameters, for instance, BOD, COD, pH, and the content of hazardous chemicals, including nitrogen, phosphorus, and chloride; as well as biological parameters, which refer to the content of various living organisms, including fungi, bacteria, and similar aquatic organisms [7,8]. Wastewater treatment technology is a key aspect of environmental conservation aimed at removing pollutant materials from wastewater using three treatment methods: Physical processing, chemical processing, and biological processing [9].…”