Department of Disaster Management, Begum Bekeya University, Rangpur 5400, Bangladesh.
Institute of National Analytical Research and Service (INARS), Bangladesh Council of Scientific and Industrial Research (BCSIR), Dhanmondi, Dhaka 1205, Bangladesh.
Sci Total Environ. 2023 Jan 20;857(Pt 1):159383. doi: 10.1016/j.scitotenv.2022.159383. Epub 2022 Oct 11.
The COVID-19 era has profoundly affected everyday human life, the environment, and freshwater ecosystems worldwide. Despite the numerous influences, a strict COVID-19 lockdown might improve the surface water quality and thus provide an unprecedented opportunity to restore the degraded freshwater resource. Therefore, we intend to investigate the spatiotemporal water quality, sources, and preliminary health risks of heavy metal(loid)s in the Karatoya River basin (KRB), a tropical urban river in Bangladesh. Seventy water samples were collected from 35 stations in KRB in 2019 and 2022 during the dry season. The results showed that the concentrations of Ni, Cu, Zn, Pb, Cd, and Cr were significantly reduced by 89.3-99.7 % during the post-lockdown period (p < 0.05). However, pH, Fe, Mn, and As concentrations increased due to the rise of urban waste and the usage of disinfectants during the post-lockdown phase. In the post-lockdown phase, the heavy metal pollution index, heavy metal evaluation index, and Nemerow's pollution index values lessened by 8.58 %, 42.86 %, and 22.86 %, respectively. Besides, the irrigation water quality indices also improved by 59 %-62 %. The total hazard index values increased by 24 % (children) and 22 % (adults) due to the rise in Mn and As concentrations during the lockdown. In comparison, total carcinogenic risk values were reduced by 54 % (children) and 53 % (adults) in the post-lockdown. We found no significant changes in river flow, rainfall, or land cover near the river from the pre to post-lockdown phase. The results of semivariogram models have demonstrated that most attributes have weak spatial dependence, indicating restricted industrial and agricultural effluents during the lockdown, significantly improving river water quality. Our study confirms that the lockdown provides a unique opportunity for the remarkable improvement of degraded freshwater resources. Long-term management policies and regular monitoring should reduce river pollution and clean surface water.
新冠疫情时代深刻影响了全世界人类的日常生活、环境和淡水生态系统。尽管受到了诸多影响，但严格的新冠疫情封锁可能会改善地表水水质，从而为恢复退化的淡水资源提供前所未有的机会。因此，我们旨在调查新冠疫情封锁前后孟加拉国热带城市河流卡塔罗亚河流域（KRB）的水质时空变化、来源和重金属（类）的初步健康风险。2019 年和 2022 年旱季期间，在 KRB 的 35 个站点采集了 70 个水样。结果表明，封锁后，Ni、Cu、Zn、Pb、Cd 和 Cr 的浓度分别降低了 89.3-99.7%（p<0.05）。然而，由于封锁后城市废物增加和消毒剂的使用，pH、Fe、Mn 和 As 的浓度增加。封锁后，重金属污染指数、重金属评价指数和 Nemerow 污染指数分别降低了 8.58%、42.86%和 22.86%。此外，灌溉水质指数也提高了 59%-62%。由于 Mn 和 As 浓度在封锁期间升高，儿童和成人的总危害指数值分别增加了 24%和 22%。相比之下，封锁后儿童和成人的总致癌风险值分别降低了 54%和 53%。在封锁前后，河流流量、降雨量或河流附近的土地覆盖没有明显变化。半变异模型的结果表明，大多数属性具有弱空间依赖性，表明封锁期间工业和农业废水受到限制，这显著改善了河流水质。我们的研究证实，封锁为改善退化的淡水资源提供了一个独特的机会。长期管理政策和定期监测应减少河流污染并清洁地表水。
