Nyairo Wilfrida Nyanduko, Owuor Philip Okinda, Kengara Fredrick Orori
Department of Chemistry, Maseno University, Private Bag 40105, Maseno, Kenya.
Environ Monit Assess. 2015 Nov;187(11):691. doi: 10.1007/s10661-015-4913-8. Epub 2015 Oct 16.
Mau Forest in the upper reaches of the Mara River basin has recently undergone increased forest destruction followed by human settlement and agricultural activities. These anthropogenic activities may be contributing nutrients and heavy metals, ultimately polluting the river water and eventually Lake Victoria water hence damaging these aquatic ecosystems. This study sought to establish the effect of anthropogenic activities and season on the water quality of the Amala and Nyangores tributaries of the River Mara in Kenya. Pristine springs in the Mau Forest were used as reference sites. Water samples were analyzed for pH, temperature, conductivity, nutrients, selected heavy metals, and selenium. The mean range of the parameters measured from sites along the tributaries was pH 5.44-7.48 and that for conductivity was 20-99 μS/cm while the mean range of nutrient levels (μg/L) was 80-443 (NO3--N), 21.7-82.7 (NH4+-N), 11.9-65.0 (soluble reactive phosphorous), and 51-490 (total phosphorous). The mean range for heavy metals and selenium (in μg/L) from sites along the tributaries were 6.56-37.6 (Cu), 0.26-4.97 (Cd), 13.9-213 (Zn), 0.35-3.14 (Cr), 0.19-5.53 (Mn), 1.90-9.62 (Pb), and 0.21-4.50 (Se). The results indicated a significant difference (p≤0.05) between the reference sites and the different sampling sites, indicating that anthropogenic activities were impacting the quality of water in the two tributaries. Although most of the parameters were within the WHO (2004), USEPA (2014) and NEMA (2006) acceptable limits for surface waters, they were above the permissible levels for domestic use. Moreover, the levels of nutrients, heavy metals, and selenium were significantly higher in the wet season than in the dry season, further indicating that anthropogenic activities are causing a disturbance in the aquatic system. Therefore, further anthropogenic activities should be checked and limited so as to conserve the ecosystem.
马拉河流域上游的莫乌森林最近森林破坏加剧，随后出现了人类定居和农业活动。这些人为活动可能会带来养分和重金属，最终污染河水，进而污染维多利亚湖水，从而破坏这些水生生态系统。本研究旨在确定人为活动和季节对肯尼亚马拉河阿马拉和尼扬戈雷斯支流水质的影响。莫乌森林中未受污染的泉水被用作参考站点。对水样进行了pH值、温度、电导率、养分、选定的重金属和硒的分析。沿支流各站点测得的参数平均范围为pH值5.44 - 7.48，电导率为20 - 99 μS/cm，而养分水平（μg/L）的平均范围为80 - 443（硝酸根 - 氮）、21.7 - 82.7（铵根 - 氮）、11.9 - 65.0（可溶性活性磷）和51 - 490（总磷）。沿支流各站点重金属和硒（μg/L）的平均范围为6.56 - 37.6（铜）、0.26 - 4.97（镉）、13.9 - 213（锌）、0.35 - 3.14（铬）、0.19 - 5.53（锰）、1.90 - 9.62（铅）和0.21 - 4.50（硒）。结果表明，参考站点与不同采样站点之间存在显著差异（p≤0.05），这表明人为活动正在影响这两条支流的水质。尽管大多数参数在世界卫生组织（2004年）、美国环境保护局（2014年）和肯尼亚国家环境管理局（2006年）规定的地表水可接受限值范围内，但高于生活用水的允许水平。此外，雨季的养分、重金属和硒含量显著高于旱季，这进一步表明人为活动正在对水生系统造成干扰。因此，应检查并限制进一步的人为活动，以保护生态系统。
