Abstract:Mineral extraction contributes positive to the socioeconomic fabric of many African countries but has also contributed to the deterioration of environmental quality. It has been branded the most destructive industry in the world. This study sought to assess the effects of conventional gold mining which use cyanide for gold extraction and artisanal gold mining which uses mercury amalgamation on water quality in Ngwabalozi River. Along the river, there are gold panning activities upstream and a conventional mine downstream. Water samples were collected at four sampling points: 1) upstream of the gold panning activities; 2) just downstream of gold panning area; 3) upstream of the conventional mine; 4) downstream of the conventional mine. Benthic macro-invertebrates were also collected at the name four points, identified to family level and counted. Water samples were analyzed for mercury, iron, arsenic, sulphates and turbidity. There were significant differences (p = 0.000) in the measurements of mercury, arsenic, sulphates, taxa richness, total count of individuals, Shannon-Weiner index, evenness index and average tolerance scores among the four sampling sites. Gold panning activities were found to pollute Ngwabalozi River with mercury while the conventional mine polluted the river with sulphates. Gold panning activities also feed a lot of sand into the river resulting in high turbidity. Gold mining reduced the taxa richness, total count of individual and the diversity of benthic macro-invertebrate community in the river. There was pollution induced succession in the river as pollution sensitive species were replaced by pollution tolerant ones.
Despite widespread food insecurity in Zimbabwe, there is an increasing amount of agricultural land being left fallow for indeterminate periods of time. The objective of the study was to assess the characteristics of vegetation growing in indeterminate fallows in Chivi district in south-central Zimbabwe. One metre by one metre quadrats were used to assess the species composition of herbaceous species while 8 m × 8 m quadrats were used for woody species. Attributes that were assessed included frequency, abundance, density of different plant species from which were computed diversity indices (Shannon-Weiner index and Shannon evenness index). The density, Shannon-Weiner index and Shannon Evenness index, and species richness of the fallow land sites were significantly lower than those of the uncultivated land. However, there were no significant differences among fallow treatments. Species richness, Shannon Index, and Shannon's Evenness Index showed a weak and non significant correlation with length of the fallow period. Woody species, which were cleared during land preparation and repeatedly weeded during the cultivation years were absent in all fallows regardless of the fallow period.
The economic meltdown in Zimbabwe which started around 2000 and lasted almost a decade led to the intensification of already existing environmental problems. Local authorities were not able to fully regulate the treatment and disposal waste and some sewerage system often burst and raw sewage flowed into streams and rivers unmonitored. In Marlborough, Harare, sewage from burst Marlborough sewerage system was flowing into Marlborough stream which flows through the suburb. Water quality in Marlborough river was monitored by collecting benthic macro-invertebrates once a month from February to April 2012 at four sites, one upstream and three downstream of the point of sewage discharge. Macroinvertebrates metrics of abundance, taxa richness, Shannon Wiener diversity index, tolerance average score per taxon (ATSPT) and South African Scoring System (SASS) scores were used in the determinations of water quality of the stream. Abundance, taxa richness and Shannon Wiener index differed significantly (p<0.05) spatially but no significant differences were found among the sampling months. SASS scores and ATSPT differed significantly (p<0.05) among sampling sites in each sampling month indicating that water quality differed significantly among sampling sites but no significant difference were found among the sampling months. The reference site had the highest number of pollution sensitive families, while the site 1, just after point of discharge had the highest number of pollution tolerant families. The abundance of pollution tolerant families decreased from site 1 going down stream possibly due to self-purification and dilution. The outcomes of the research showed that the inflow of sewage into the stream reduced water quality of the stream.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.