Department of Ecology and Resource Management, University of Venda, Thohoyandou 0950, South Africa; South African Institute for Aquatic Biodiversity, Grahamstown 6140, South Africa.
Department of Biological Sciences and Biotechnology, Botswana International University of Science and Technology, Palapye, Botswana; South African Institute for Aquatic Biodiversity, Grahamstown 6140, South Africa.
Sci Total Environ. 2019 Sep 20;684:296-302. doi: 10.1016/j.scitotenv.2019.05.167. Epub 2019 May 22.
The consideration of nutrients in pollution dynamics is important for environmental management and conservation. Developing countries are yet to appreciate the aquatic ecosystem pollution impacts on their economies and as such, information on water pollution dynamics is limited. This study assessed the spatio-temporal dynamics of nutrient loading and retention in stream water and sediments in the Bloukrans River system, Eastern Cape province, South Africa over the course of the wet and dry season. Sediment and water samples were analysed for total phosphorus (TP) and nitrogen (TN) concentrations, and were used in combination with river flow discharge, to determine nutrient loads. The study results highlight that river discharge plays a significant role in temporal differences in sediment and water column nutrient concentrations. The mean sediment nutrient concentration was high for the dry season, with high values being observed for the urban river system. Nutrient loads were high above the sewage treatment works outflow (i.e. urban sites), as such, a decreasing trend was observed with increasing distance from the urban environment. Nutrient loads were generally high for the dry season in comparison to the wet season indicating organic matter retention (i.e. accumulation from burst sewage pipes) most likely due to low flows. While it was evident that the ageing wastewater infrastructure contributed to the observed state of the Bloukrans River, the high natural nutrient retention capacity seemed to mitigate eutrophication of downstream aquatic ecosystems. As such, the nutrient retention capacity and management of the system is central to the entire Bloukrans River catchment management practices. Therefore, the study contributes to our understanding of water and sediment nutrient pollution dynamics in an arid temperate river landscape where vast spatio-temporal differences in base flow characterise the riverscape.
在污染动态中考虑营养物质对于环境管理和保护至关重要。发展中国家尚未意识到水生生态系统污染对其经济的影响，因此，有关水污染动态的信息有限。本研究评估了南非东开普省布卢坎斯河流域在干湿季节过程中溪流水中和沉积物中养分负荷和保留的时空动态。对沉积物和水样进行了总磷（TP）和总氮（TN）浓度分析，并结合河流流量排放，以确定养分负荷。研究结果表明，河流流量在沉积物和水柱养分浓度的时间差异中起着重要作用。干季的沉积物养分浓度较高，城市河流系统的浓度值较高。污水处理厂出水口（即城市地区）以上的养分负荷较高，因此，随着与城市环境的距离增加，观察到负荷呈下降趋势。与湿季相比，干季的养分负荷通常较高，这表明由于流量低，有机物质的保留（即突发污水管中的积累）很可能发生。尽管老化的废水基础设施对布卢坎斯河的现状产生了影响，但高天然养分保留能力似乎减轻了下游水生生态系统的富营养化。因此，系统的养分保留能力和管理对于整个布卢坎斯河流域的管理实践至关重要。因此，本研究有助于我们了解干旱温带河流景观中的水和沉积物养分污染动态，其中基流特征的巨大时空差异构成了河流景观。
