Institute of Integrated Science and Technology, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki, 852-8521, Japan.
Department of Kyushu Liberal Arts Education, Tokai University, 9-1-1 Toroku, Higashi-ku, Kumamoto, 862-8652, Japan.
Sci Rep. 2021 Jan 28;11(1):2598. doi: 10.1038/s41598-021-82188-2.
Nitrate pollution in groundwater is a serious problem in many parts of the world. However, due to the diffuse and common spatially over-lapping character of potential several non-point pollution sources, it is often difficult to distinguish main nitrate sources responsible for the pollution. For this purpose, we present a novel methodology applied to groundwater for an intensely polluted area. Groundwater samples were collected monthly from April 2017 to March 2018 in Shimabara City, Nagasaki, Japan. Soil samples were collected seasonally at soil surface and 50 cm depth at 10 locations during the same period. Sequential extraction by water and extract agents was performed using calcium phosphate for anions and strontium chloride for cations. Mean nitrate concentration in groundwater close to a livestock waste disposal site (hereinafter called "LWDS") was 14.2 mg L, which is exceeding Japanese drinking water standards (10 mg L). We used coprostanol concentration, which is a fecal pollution indicator, to identify pollution sources related to livestock waste. For this purpose, we measured coprostanol (5β) and cholestanol (5α) and then calculated the sterol ratio (5β/(5β + 5α)). The ratios for three groundwater sampling sites were 0.28, 0.26, and 0.10, respectively. The sterol ratios indicated no pollution (< 0.3). However, the detection of coprostanol originating from animal and human waste showed that groundwater was clearly affected by this pollution source. Nitrate levels in the soil were relatively high in samples collected close to the LWDS and coprostanol contents were affected by livestock waste. Soil and groundwater nitrate concentrations displayed a complex but strong relationship. Nitrate contents were shown to be transported downstream from source areas in both soil and groundwater.
地下水硝酸盐污染是世界许多地区的一个严重问题。然而，由于潜在的非点污染源具有弥散和普遍的空间重叠特征，因此通常难以区分造成污染的主要硝酸盐源。为此，我们提出了一种应用于地下水的新方法，该方法适用于一个污染严重的地区。从 2017 年 4 月到 2018 年 3 月，在日本长崎市岛原市每月采集地下水样本。在同一时期，10 个地点的土壤表面和 50 厘米深处采集土壤样本。使用磷酸钙提取阴离子和氯化锶提取阳离子，采用水和提取剂顺序提取。靠近牲畜废物处理场（以下简称“LWDS”）的地下水硝酸盐浓度平均值为 14.2mg/L，超过了日本饮用水标准（10mg/L）。我们使用粪甾烷醇浓度作为粪便污染指标来识别与牲畜废物有关的污染源。为此，我们测量了粪甾烷醇（5β）和胆甾烷醇（5α），然后计算了甾醇比（5β/（5β+5α））。三个地下水采样点的比值分别为 0.28、0.26 和 0.10。该比值表明没有污染（<0.3）。然而，动物和人类粪便来源的粪甾烷醇的检测表明，地下水明显受到这种污染源的影响。靠近 LWDS 采集的土壤样本中的硝酸盐含量相对较高，并且粪甾烷醇含量受到牲畜废物的影响。土壤和地下水硝酸盐浓度之间存在复杂但强烈的关系。硝酸盐含量显示从土壤和地下水中的源区向下游输送。
