Regional Water and Environmental Sanitation Center, Dept of Civil Engineering, Kwame Nkrumah University of Science and Technology, Private Mail Bag, University Post Office, Kumasi, Ghana; National Isotope Hydrology Lab, National Nuclear Research Institute, Ghana Atomic Energy Commission, P. O. Box LG 80, Legon-Accra, Ghana.
Regional Water and Environmental Sanitation Center, Dept of Civil Engineering, Kwame Nkrumah University of Science and Technology, Private Mail Bag, University Post Office, Kumasi, Ghana.
Ecotoxicol Environ Saf. 2020 Mar 15;191:110227. doi: 10.1016/j.ecoenv.2020.110227. Epub 2020 Jan 22.
A significant population within the Lower Volta River Basin of Ghana relies solely on untreated groundwater (GW) and surface water (SW) for various purposes. However, negative practices associated with increasing human activities pose threats to particularly GW quality in the basin. Using NO as a proxy, this study mainly focused on the status of GW contamination, origins of NO and potential human health risks through integrated hydrochemistry, correlation analysis, isotopes (N, δO), Bayesian and USEPA human health risk models. Slightly acidic to alkaline GW and SW environments were observed. Electrical conductivity (EC) values above 1000 μS/cm were recorded in 45% of the GW with a maximum of 19370 μS/cm. NO in GW ranged from 0.12 to 733 mg/L with average 59.6 mg/L and positively correlated with K, Ca, Mg Cl, Na and EC. In SW, a maximum of 5.3 mg/L of NO was observed. Largely, 75% of the GW exceeded local background NO value of 2.1 mg/L, while 35% were above the WHO recommended value of 50 mg/L. Bivariate and correlation relationships elucidated human contributions to sources of NO, Cl, SO and K to GW in the basin. From NO/Cl ratio, 43% of the GW and 21% of SW were affected by effluents and agrochemicals. Values for δN-NO and δO-NO ranged from +4.2‰ to +27.5‰ and +4.5‰ to +19.9‰ for GW, and from +3.8‰ to +14.0‰ and +10.7‰ to +25.2‰ for SW. Manure, septic effluents and mineralized fertilizers are sources of NO contamination of water in the basin. The Bayesian model apportioned 80% of GW NO contamination to sewage/manure. Hazard index indicated 70%, 50% and 48% medium to high-risk levels for infants, children and adults respectively, with 79% high-risk of SW NO contamination to infants. Immediate measures for GW and SW quality protection are recommended.
加纳下沃尔特河流域的很大一部分人口仅依靠未经处理的地下水 (GW) 和地表水 (SW) 来满足各种需求。然而，不断增加的人类活动带来的负面影响对流域内的地下水质量构成了威胁。本研究主要以硝酸盐（NO）作为指标，通过综合水化学、相关分析、同位素（N、δO）、贝叶斯和美国环保署人类健康风险模型，研究了 GW 污染状况、NO 的来源以及潜在的人类健康风险。结果表明，GW 和 SW 的环境呈弱酸性至碱性。45%的 GW 电导率（EC）值超过 1000 μS/cm，最大值为 19370 μS/cm。GW 中 NO 的浓度范围为 0.12 至 733 mg/L，平均值为 59.6 mg/L，与 K、Ca、Mg Cl、Na 和 EC 呈正相关。SW 中 NO 的最高浓度为 5.3 mg/L。75%的 GW 超过了当地 2.1 mg/L 的背景 NO 值，35%的 GW 超过了世界卫生组织推荐的 50 mg/L 的标准。双变量和相关关系表明，人类活动对流域内 GW 中 NO、Cl、SO 和 K 的来源产生了影响。根据 NO/Cl 比值，43%的 GW 和 21%的 SW 受到废水和农用化学品的影响。GW 中 δN-NO 和 δO-NO 的值范围分别为+4.2‰至+27.5‰和+4.5‰至+19.9‰，SW 中的值范围分别为+3.8‰至+14.0‰和+10.7‰至+25.2‰。粪肥、污水和矿化肥料是流域内水 NO 污染的来源。贝叶斯模型将 80%的 GW NO 污染归因于污水/粪肥。危害指数表明，婴儿、儿童和成人分别有 70%、50%和 48%处于中高风险水平，SW 中 NO 污染对婴儿的风险为 79%。建议立即采取措施保护 GW 和 SW 的水质。
