Cronin Aidan A, Pedley Steve, Hoadley Alfred W, Kouonto Komou Fatoumata, Haldin Louis, Gibson James, Breslin Ned
Robens Centre for Public and Environmental Health, University of Surrey, Building AW Floor 2, Guildford Surrey, UK.
J Water Health. 2007 Sep;5(3):441-54. doi: 10.2166/wh.2007.040.
By 2010 Africa's urban population will have grown to over 420 million with on-site sanitation the predominant excreta disposal option. The use of on-site sanitation has important public health benefits but can result in large faecally derived loadings of nitrogen and chloride to groundwater resources. Nitrate is of particular concern, with elevated concentrations linked to potentially serious health problems. N and Cl can derive from natural sources so it is important to quantify the additional impact of human activities. Several authors have used empirical relationships between nitrate and chloride concentrations to assess the extent to which excreta influences groundwater quality. However, these relationships have assumed fixed loadings from excreta. Relationships between N and Cl have been extended here by adding country-specific estimates of average annual per capita nitrogen and chloride content of, and loading from, excreta. The results are compared with groundwater monitoring results from two very different mid-sized African cities (Timbuktu, Mali and Lichinga, Mozambique) where the vast majority of residents use on-site sanitation and are dependent on the subsurface water for drinking purposes. The results illustrate the impact of urbanisation on groundwater quality. They are compared with data from other African cities to allow the calculation of a general nitrate and chloride relationship for unsewered African urban areas. Potential interventions to help arrest rising nitrate levels and so provide a public health benefit are also examined.
到2010年，非洲城市人口将增长到4.2亿以上，现场卫生设施是主要的排泄物处理方式。使用现场卫生设施对公共卫生有重要益处，但可能导致大量粪便来源的氮和氯进入地下水资源。硝酸盐尤其令人担忧，其浓度升高与潜在的严重健康问题有关。氮和氯可能来自自然源，因此量化人类活动的额外影响很重要。几位作者利用硝酸盐和氯浓度之间的经验关系来评估排泄物对地下水质量的影响程度。然而，这些关系假设排泄物的负荷是固定的。通过增加各国人均排泄物中氮和氯的年均含量及负荷的具体估计值，这里扩展了氮和氯之间的关系。将结果与两个截然不同的非洲中型城市（马里的廷巴克图和莫桑比克的利欣加）的地下水监测结果进行比较，这两个城市的绝大多数居民使用现场卫生设施，且依赖地下水作为饮用水源。结果说明了城市化对地下水质量的影响。将其与其他非洲城市的数据进行比较，以便计算未铺设污水管道的非洲城市地区硝酸盐和氯的一般关系。还研究了有助于遏制硝酸盐水平上升从而带来公共卫生益处的潜在干预措施。
