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]. Availability of high Ammonia on industry. NOx are released when fuels are burned at land causes an unbearable odor in water and reduces high temperatures and power plants contribute most of the efficiency of disinfecting. High levels of Ammonia the NOx [1]. The current study of the distribution of also results in reduced body weight in humans, NOx serves to assist in having measures that reduces reduced ph in blood and lowers fat accumulation in the increase in releases of NOx and to assess which animals. If the intake in humans exceed about 100 human activity is contributing to the most NOx in the grams may disturb glucose tolerance and reduced area. The study of NOx is important as it causes tissue sensitivity to insulin [7]. The current study adverse environmental effects such as haze pollution, serves to show how ammonia is distributed in Hwange acid rain, eutrophication which leads to oxygen which will assist in knowing levels of ammonia depletion that degrades water quality and harming released into the environment in relation to land use. fish. EPA stipulates that 17 mg of ammonia per litre at ph 7 3. Results and Discussion and at 20 degrees Celcius temperature should not be exceeded in three years. 3.1 Nitrogen Oxides (NO2/NO3) Loads Ammonia = (Total Ammonia (mg/N)  The map shows that there is very low nitrogen 17/14)/1+10^(0.09018+(272992/273.15+Temp°C)-pH) oxides loads in the north eastern parts of Hwange 2.3.2 Total Dissolved Solids (TDS) urban catchment and on the southern parts with These Total Dissolved Solids are made up of loadings of 0-0.03 g per year. These areas are mostly inorganic salts such as calcium, magnesium, characterized by small scale farming, built up and potassium, sodium, chlorides, bicarbonates, sulfates Zambezi River. High amounts of nitrogen dioxide is and small amounts of organic matter [8]. These can found on the south eastern part of the map which develop from natural sources or human activities and act as nutrients. TDS acts as nutrients however too much of it can pose negative impacts on the environment through increasing toxicity and salinity. High salinity levels limits biodiversity, causes a shifts in biotic communities and chronic effects. The changes in ionic composition of water can result in exclusion of other species and promoting the availability of other resulting in unbalanced ecosystem [8]. 2.3.3 Nitrogen Oxides (NOx) NOX comprises of nitrogen compounds like nitrogen dioxide (NO2), and nitric oxide (NO). When these components are emitted into the atmosphere Fig. 3 NOx distribution in Hwange.

98 Pollution Extent Mapping and Modeling in Hwange Town, Zimbabwe ranges from 0.12-0.14 g and this part is characterized by mining areas (AMD) and waste sewage areas.

3.2 Ammonia Loads

The output map (Fig. 4) shows that there is more ammonia with range of 0.04-0.06 g in the south eastern parts of the region, which are characterized by AMD (mining site) sewages and built up. Low loadings of ammonia are on the north eastern parts and lower southern side of the map.

3.3 Total Dissolved Solids Loads (TDS)

The map in Fig. 5 shows that there are high total dissolved solids of 193965-242256 gramms in the eastern parts of Hwange. Low TDS of 800-49091 g in the rest of the map. Fig. 5 Total dissolved solids distribution in Hwange.

4. Discussion of Results

South eastern parts of Hwange has the highest level of NOx which is characterised by Colliery Company mining sites and China Company mining site. The most occurring activity in this area is the mining of coal and electricity generation. As a result there is bound to be high NOx levels in the area. These activities release most of the NOx that were recorded by the PLOAD model. NOx is mostly released by power plants, car fumes, gas turbines, incinerators Diesel engines [9]. The mining and electricity generating companies in Hwange uses coal during electricity generation which releases NOx in the atmosphere and adding to the ageing of the generating Fig. 4 Ammonia distribution in Hwange. plants the NOx released into the atmosphere has Table 3 Shows the cutoff of parameter pollutant mass (in increased over the years. gramms) allowed obtained from EMA Guidelines on This area with high NOx also covers an area where pollution. there are generators used to pump water from the Variable Safe Lowhazard High Hazard NOx < 0.7 < 1.3 > 1.5 Zambezi River to ZPC for electricity generation. Low TDS < 100 < 2000 > 3000 levels of NOx are found in the Northeastern parts of Ammonia < 0.5 < 1.5 > 2 the map which is characterised by residential zones according to the classified land use map. The NOx is resulting from moving vehicles and generators used in the area.

Pollution Extent Mapping and Modeling in Hwange Town, Zimbabwe 99

The PLOAD Model predicted most of the according to the results shown by the PLOAD model. Ammonia being in the south eastern parts of Hwange. The study was aimed at determining the spatial This area is characterised by Colliery Company water distribution of pollution as a result of human activities treatment plant, the AMD plant and the No 1 main and the study modeled that most pollution is occurring sewage site. These sites have high ammonia in the mining sites. The benefits of the software used concentration because ammonia is used as a coolant is it is free and readily available, and there are user and a cleansing agent. Ammonia found in water manuals and tutorials which act as guidelines for treatment plant area is used for the water purification modelling or software use. process. There is not much ammonia in the References agricultural areas because subsistence farming is practiced hence there is no fertilizer application in [1] Air Quality Nitrogen Oxides: How NOx Emissions Affect Human Health and the Environment, December most of the farms and the ammonia predicted can be 2002, p. 2002. from the human waste used as manure. [2] W. Bo et al., Influence of land use and point source Total Dissolved Solids (TDS) are higher in the pollution on water quality in a developed region: A case southeast parts of Hwange because this area has small study in Shunde, China, International Journal of Environmental Research and Public Health 15 (2017) (2) streams coming from the mines and flow towards 51, doi: 10.3390/ijerph15010051. Zambezi river. These streams have high TDS coming [3] Greenpeace, The environmental impacts of coal, Briefing in from the mining processes. The area is a low lying 2 (May 2005) 1-4, available online at: area hence most runoff is accumulating in this area. http://www.greenpeace.org/new-zealand/Global/new-zeal and/report/2007/1/enviro-impacts-of-coal.pdf. TDS is assumed to increase as a result of urbanization [4] D. D. Matyanga, Mineral Economist and Technical which will lead to high runoff [8], and also results Advisor, no date. from effluent discharge [10]. There was high [5] Zimbabwe Power Company (ZPC), Hwange Power prediction of TDS on the watersheds with mining, Station Expansion, 2015. [6] Force C., Cradle to grave: The environmental impacts electricity generation and along the zambezi river from coal, Clean Air Task Force (2001) 12, available because these sites have more effluent being relesed online at: http://catf.us/resources/publications/files/ on a daily basis from the sewage treatment plants, Cradle_to_Grave.pdf. water treament plants. [7] WHO, Chromium in drinking-water background document for development of WHO guidelines for Pollutants are high in mining areas and at electricity drinking-water quality, Health San Francisco 2 (20th generating power stations because activities occuring July, 1996), available online at: at these sites lead to emission of these pollutants. On http://www.who.int/water_sanitation_health/dwq/che. the other hand there is moderately high amounts of [8] P. K. Weber-Scannell and L. K. Duffy, Effects of total dissolved solids on aquatic organisms: A review of pollutants in settlements landuse zone because the literature and recommendation for salmonid species, human activities occuring in this area does not American Journal of Environmental Sciences 3 (2007) (1) produce much pollutants. There is little concentration 1-6, doi: 10.3844/ajessp.2007.1.6. of pollutants on natural cover because the land is [9] USEPA, PLOAD version 3.0. GIS Pollutant Loading Application — Users Manual, January 2001, p. 48. mostly bare and the area is almost grassland region available online at: http://water.epa.gov/scitech/datait/ and hence the pollutants found in this area would be models/basins/upload/2002_05_10_BASINS_b3docs_PL from accumulation from runoff or erosion. According OAD_v3.pdf. to the study there is a relationship between land use [10] Duffy L., Effects of total dissolved solids on aquatic organisms: A review of literature and recommendation and the level of pollution. Mining is the most human for salmonid species, January 2007, doi: activity that contributes to pollution in Hwange 10.3844/ajessp.2007.1.6.