92 Contamination of Agricultural Products in the Surrounding of the Tsumeb Smelter Complex Benjamin Mapani 1 , Rainer Ellmies 2 , Lothar Hahn 4 , Gabi Schneider 3 , Kaarina Ndalulilwa 3 , Rosina Leonard 3 , Mukuve Zeeuw 2 , Norwel Mwananawa 2 , Shopala Uugulu 2 , Eline Namene 2 , William Amaambo 2 , Florence Sibanda 5 , Maria Mufenda 3 1 University of Namibia, Geology Department, Windhoek, Namibia 2 Bundesanstalt für Geowissenschaften und Rohstoffe, Hannover, Germany 3 Geological Survey of Namibia, Ministry of Mines and Energy, Windhoek, Namibia 4 Deutsche Forschungsgemeinschaft (DFG), Bonn, Germany 5 Department of Water Affairs, Ministry of Agriculture, Water and Forestry, Windhoek, Namibia Since the turn of the last century, the Tsumeb area was a major mining hub until 1999, and still contin- ues to be a smelting centre for ores originating from the Democratic Republic of Congo, Zambia, Mauritania, Bulgaria and Chile. This has brought about a situation where the top soils surrounding the smelter, especially in the down wind direction, are highly contaminated with lead, zinc, copper, arsenic and cadmium. The con- tamination of the top soils and crops is a result of historical smelter emissions as well as due to windborne dust derived from the tailings and slag dumps of the smelter complex. A total of 43 samples of vegetative material were collected in areas with potential soil contamination in the surroundings of the Tsumeb smelter complex. The samples comprise fruit crops (marula, papaya), vegetable (tomato, parsley, carrot, bean, pumpkin, chillies) and a field crop (maize). Twelve topsoil samples were collected at specific sampling sites for correlation with vegetation samples. The concentrations of arsenic, lead and cadmium of most of the fruits and vegetables (marula fruits, pumpkins, chilli, and tomato) correlate with the heavy metal values of the underlying contami- nated top soils. The guideline values of the WHO (Codex Alimentarius) and EU were applied for the interpre- tation of eventual health risks. All plant samples are characterised by high lead concentrations exceeding the guideline values. Crops from Tsumeb-Nomtsoub and the agricultural land to the west of the smelter show criti- cal contaminations. Introduction The contamination of the agricultural land in the surroundings of the Tsumeb smelter complex has been well known for many years, though no quantitative data had been available. It can be traced back to emis- sions from the historical smelter activities as well as to windborne dust derived from the mine tailings and slag dumps in the smelter area. The Geological Survey of Namibia monitored the environmental situation in Tsumeb in cooperation with the Czech Geo- logical Survey (Kríbek and Kamona, 2005) and the University of Namibia in the past few years. This research has now revealed the exact extent and severity of soil contami- nation in the Tsumeb area (Geological Sur- vey of Namibia, 2006a; 2006b; 2007a; 2007b; Iipinge, 2008). The previous research included groundwater quality, soil contami- nation, quality of fresh water fish and to a limited extent the contamination of grasses on surrounding farms. For this study, a plant sampling campaign assisted by students from the Department of Geology at the University of Namibia (UNAM) was carried out in the Tsumeb area. The following metals were analysed: arsenic, cadmium, copper, lead, molybde- num and zinc. Soil is a crucial component of rural and urban environments in a setting such as Tsumeb, as it forms the basis for crop cultivation and grazing of domestic animals. Heavy metals occur naturally in soils but rarely at toxic levels. In the case of Tsumeb, critical soil contamination with a number of metals has been caused by mining and processing of poly-metallic ores over a period of more than 100 years. Heavy metals have a deleterious effect on bacteria which are key players in nutrient turnovers in soil (Gremion, 2003). Due to the prevailing car- bonate lithologies, the soils in the Tsumeb area have high a pH which is generally re- ducing the metal uptake of the plants (USDA-NRCS, 2000). Communs geol. Surv. Namibia, 15 (2014), 92-110