Ineffectiveness of Nakivubo wetland in filtering out heavy metals from untreated Kampala urban effluent prior to discharge into Lake Victoria, Uganda
Ineffectiveness of Nakivubo wetland in filtering out heavy metals from untreated Kampala urban effluent prior to discharge into Lake Victoria, Uganda
复制标题
纳基武博湿地在未经处理的坎帕拉城市污水排入乌干达维多利亚湖之前过滤重金属无效
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
J. Wasswa
中科院分区：
文献类型：
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作者：
J. Mbabazi;J. Kwetegyeka;M. Ntale;J. Wasswa
自20世纪70年代政治动荡以来，乌干达首都坎帕拉的人口急剧增加，工业化程度也随之大幅上升。然而，很少有制造工厂在将其污染的废水排放到周围生态系统之前对其进行预处理。坎帕拉的主要排水系统是Nakivubo水道，直接流入邻近的维多利亚湖，这是世界上第二大内陆淡水湖。城市污水量增加，加上填海作农作物种植，大大降低了湿地过滤主要污染物，特别是重金属的效率。利用原子吸收分光光度法，本研究表明，筛选出锌（Zn），铜（Cu），镉（Cd）和铅（Pb）的效率从2006年12月的89.7 - 98.3%下降到2008年12月的79.4 - 92.1%，连续三年。这表明湿地吸收重金属的效率越来越低。同一时期，距湿地口约两公里的湖水中相同金属的含量相应地从23 - 31%增加到35 - 47%。这对鱼类的质量和直接依赖湖水进行家庭和工业使用的200多万城市人口构成了严重威胁。补救措施在于有关当局在每个工厂现场执行预处理，提高工厂管理对环境问题的敏感性，并采取更严格的措施防止湿地侵占。
关键词：坎帕拉城市污水，Nakivubo湿地，重金属过滤，维多利亚湖。
The population of the Ugandan capital city of Kampala has dramatically increased since the political turmoil of the 1970s and with it a considerable rise in industrialisation. Few manufacturing plants, however, have pretreatment installations in place for their polluted effluent prior to discharge into the surrounding ecosystems. Kampala’s main drainage system is the Nakivubo channel which empties directly into the neighbouring Lake Victoria, the second largest inland freshwater lake in the world. Increased urban effluent load coupled with reclamation for crop farming have considerably reduced the effectiveness of the wetland to filter out major pollutants, in particular heavy metals. Using atomic absorption spectrophotometry, this study showed that the efficiency in sieving out zinc (Zn), copper (Cu), cadmium (Cd) and lead (Pb) has shrunk from 89.7 - 98.3% in December 2006 to 79.4 - 92.1% in December 2008, over a period of three consecutive years. This is indicative of the growing ineffectiveness of the wetland to absorb heavy metals. Levels of the same metals in the lake water some two kilometres away from the mouth of the wetland have correspondingly increased from 23 - 31% to 35 - 47% in the same period. This poses a serious threat to the quality of the fish and to the over two million urban population that directly depend on the lake water for domestic and industrial use. The remedy lies in the relevant authorities to enforce pretreatment at each factory site, increased factory management sensitisation on environmental concerns and more stringent measures against wetland encroachment.
Key words: Kampala urban effluent, Nakivubo wetland, heavy metal filtration, Lake Victoria.