Pollution Extent Mapping and Modeling in Hwange Town, Zimbabwe
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Modern Environmental Science and Engineering (ISSN 2333-2581) January 2021, Volume 7, No. 1, pp. 94-99 Doi: 10.15341/mese(2333-2581)/01.07.2021/012 Academic Star Publishing Company, 2021 www.academicstar.us Pollution Extent Mapping and Modeling in Hwange Town, Zimbabwe Ndlovu M.1, Sunny M. Chikwanha2, Tungwarara M. K.3, Mutibura E. R.4, Ncube K.5, Mazula A.5, and Chikumene L.1 1. University of Zimbabwe 2. Prone Cane Investments (Pvt) Ltd t/a Envirotech, Zimbabwe 3. Midlands State University, Zimbabwe 4. Zimbabwe Open University, Zimbabwe 5. Chinhoyi University of Technology, Zimbabwe Abstract: For best pollution management practices to be put in place there is need for information and this information can be attained through examining, mapping and modelling the extent of pollution. This information helps in ensuring that resources for pollution management are distributed well and accordingly. The current study was conducted in Hwange to map the distribution of pollution using pollutants such as nitrogen oxides, ammonia, and Total dissolved Solids as indicators of pollution within the sub catchment area. In order to model point and non-point sources of pollution with the assumption of human activities as the main source of pollution, the PLOAD model tool found in BASINS software was used. The most prevalent human activities in Hwange are mining, electricity generation and settlement. Using the PLOAD model and export coefficient method pollutant in each sub catchment were calculated and mapped. The results obtained indicated that the extent and amount of pollutant is directly related to the type of human activity occurring in each sub catchment. Key words: pollution management, PLOAD, Hwange Town, Zimbabwe cause adverse health complications [2]. These metals 1. Introduction are non-biodegradable hence their pollution is long Over the years there has been an increasing concern lasting and the cleanup processes are expensive. Soil pertaining pollution due to mining activities. Pollution contamination due to mining activities is not only of soils and vegetation caused by mining comes from toxic but can also lead to loss of soil functions and mostly the atmospheric fallout of emissions. Research productivity [3]. Coal mining in Hwange has been has established that pollutants from mining and operational since 1903 when the first shaft was industrial processing activities are rich in metallic commissioned by Wankie Coal Railway and pollutants specifically heavy metals such as Cd, Cu, Exploration Company at No.1 Colliery [4] and has Pb and Zn [1]. Of the heavy metals released during been the major environmental polluting activity for mining, exposure to cobalt (Co), copper (Cu), lead many years. Over the years the mining activities has (Pb), cadmium (Cd), mercury (Hg), zinc (Zn), increased in the area due to increased number of manganese (Mn) and arsenic (As) among others can mining companies within Hwange. The biggest client of the coal generated in Hwange is Zimbabwe Power Company for electricity generation purposes. Corresponding author: Sunny M. Chikwanha, Mr; research area/interest: environmental science, technology, engineering Electricity generation in Hwange was commissioned and management. E-mail: [email protected]. Pollution Extent Mapping and Modeling in Hwange Town, Zimbabwe 95 in 1983 [5], hence due to ageing of the production include Ammonium, nitrogen and Total Dissolved plant complete combustion has become difficult as a Solids. This study seeks to determine the spatial extent result there is more pollution taking place. Coal of pollution resulting from land use type around mining is carried out through open cast method and Hwange Town. Its major aim is to show the spatial this has both short-term and long-term effects on land distribution of pollutants around Hwange and the including dust, noise, land degradation and water intensity of pollution. On the other hand this study pollution. Pollution occurs in various stages of mining, also seeks to determine the relationship between transportation and electricity generation. Mining of land-use and pollution distribution within Hwange. coal produces both solid and liquid waste which must 2. Material and Methods be treated and disposed correctly in order to reduce the level of pollution [6]. The coal mining and Hwange town is situated within Hwange district, electricity generation activities causes environmental which is in Matabeleland North Province. It is in the impacts such as acid mine drainage, air emissions, northwestern parts of Zimbabwe which is close to the thermal releases, climatic and visual impacts from international boarders of Botswana and Zambia. The cooling towers, solid waste disposal, and ash disposal area of study is situated at 770 meters above sea level. [3]. Land use types within an area is a cause for The coordinates for Hwange town are 18°21’53”S and concern because of haphazard development, reduced 26°30’00”E. According to population estimates in environmental quality standards, loss of agriculture 2015 Hwange had a total population of 38000. land, species extinction, loss of biodiversity and Hwange is the largest coal providing town in habitat and destruction of wet lands [2]. The land use Zimbabwe and it started with Colliery Company as types also affect water quality standards [2]. Finding the main coal mining company around the area. With out the relationship between land use and pollution time more companies were opened such as Makomo, assists in developing pollution management practices Kalota and China. Hwange also has a tourist attraction [2]. Each activity has a pollutant additive to the zone with game parks and reserves. The area is in agro environment hence thresholds for these pollutants ecological region VI which is associated with high should be designed so as to avoid environmental temperatures and little rainfall throughout the year. pollution and degradation. The major activities that compromises the environment in Hwange include coal mining, electricity generation and urbanization. The increased number of coal mining companies led to urbanization as a result of increased populations according to census of 2002 and 2012 respectively. This has resulted in more demand for land for human activities such as mining and settlement hence reducing forestry and bare land within the area. Coal mining is assumed to be the most polluting activity in Hwange [4], On the other hand pollution is as a result of different human activities hence the current study desires to show the extent of pollution and how these pollutants are distributed in relation to land use Fig. 1 Showing the map of study area classified in landuse activity. The study focuses on three variables which zones. 96 Pollution Extent Mapping and Modeling in Hwange Town, Zimbabwe 2.1 Data Collection data to produce maps using its integrating framework provided by a Geographic Information System. This Table 1 shows the data inputs and data sources. framework allows user to organize spatial information Table 1 Data inputs and data sources. as maps, tables or graphs and also analyzing of Data Inputs Data Source landscape information to display relationships classification of Landsat Land-use in shape file format between them. The study used BASINS software images Administrative divisions Diva GIS because it brings key data and analytical components Watershed data Calculated using DEM in one tool. BASINS supports development of Pollutant loading rates tables Database cost-effective approaches to watershed and sub in dbf format catchment management. The software provides an Sample Point data sample surveys integrated watershed assessment and modelling DEM downloaded from SRTM Point source facility locations framework that supports the analysis of point and Sample surveys and loads non-point source of pollution. The environmental data required are soil characteristics, land-use data, Point 2.2 Modelling Process source data, meteorological and precipitation data, This process was used to map out intensity and DEM, and area segmentation. The classification of extent of pollution within Hwange using datasets such land use data was carried out in ArcMap and the as the DEM, classified land use maps and point data. modelling process was carried out in BASINS Fig. 2 shows the modelling process. software using the PLOAD model tool. The pollution modelling process was carried out PLOAD is a GIS-based model that is used for using the Basin (Better Assessment Integrating Point calculating average-annual runoff and pollutant loads and Non-Point Source) Software. This software was from a watershed under particular land use patterns. designed for conducting environmental analysis. It The current study used the export coefficient within serves its purpose through integrating environmental the PLOAD model to calculate pollutant loads for each sub catchment. The export coefficient uses the equation below LP = U (LPU * AU) Where: LP = Pollutant load LPU= Pollutant loading rate for land use type u, lbs/acre/year; and AU = Area of land use type u, acres The loading rates are derived from the export coefficient tables, while the land use areas are interpreted from the land use and watershed GIS data. 2.3 Pollutant Variables Modelled 2.3.1 Ammonia Ammonia is mostly used in waste treatment plants and water processing plants. Colliery and ZPC own various plants around Hwange for processing of water Fig. 2 The modelling process. Pollution Extent Mapping and Modeling in Hwange Town, Zimbabwe 97 from Zambezi for human consumption. Ammonia can there are negative environmental effects that might also be found in human waste hence the presence of arise. The release of these can produce harmful ammonia at higher levels can show an indication of particulate matter, acid rain and smog. These have fecal pollution [7]. When ammonia dissolves in water different negative effects on the environment. The it forms hydroxyl ions and this formation is depended sources of NOx in Hwange are the electricity on temperature, ph and concentration of dissolved generating plants, moving vehicles and the mining salts in water [7].