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.
Highlights
Shimabara Peninsula in Nagasaki Prefecture, Japan is composed of three municipalities: Shimabara City, Unzen City, and Minami-Shimabara City
Mean dissolved oxygen (DO) of about 8.0 mg L−1 indicates that groundwater is aerobic (Table 1)
Land use and correlation analysis indicate that excessive NO3 −N is related to application of chemical fertilizers and discharge of livestock waste
Summary
Shimabara Peninsula in Nagasaki Prefecture, Japan is composed of three municipalities: Shimabara City, Unzen City, and Minami-Shimabara City. The peninsula is an important agricultural and livestock region. The cultivated area occupies about 12,100 ha of the total 45,962 ha of the peninsula [1]. Agricultural production areas for potatoes, vegetables, industrial crops, and fruit farms represent about 62.7% of the cultivated area. Crops such as carrots, lettuce and Chinese cabbage are main crops cultivated throughout the year. The number of milk cattle and chicken (70% of all livestock) is about 7000 and 1,236,000, respectively [1]. Shimabara Peninsula was recognized as a UNESCO Global Geopark in 2009
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
