Epsilon Archive for Student Projects

Abstract

This minor field study was executed in Zomba, Malawi, where land for cultivation is scarce, resulting in cultivation at potentially contaminated sites. Waste dumps are one of the main sources of heavy metal contamination and excessive levels in soil might lead to elevated levels in crops which can cause severe health effects. The objective of this study was to investigate how the current waste management affects the health of the local inhabitants when cultivating at contaminated sites, focusing on heavy metals. Two sites were studied: one field on a waste dump (WD) and one field close to a waste water treatment plant (WWTP). The hypothesis was that soil and crops contained higher concentrations of heavy metals close to these sites compared to a reference site. Samples of soil and crops were collected and analysed for cadmium, chromium, copper, iron, lead and zinc. The daily intake of these metals via maize was further calculated for the farmers to investigate possible health effects.

Comparing the results to The Swedish Environmental Protection Agency’s generic guideline values, levels are exceeded for copper, cadmium and lead at the waste water treatment plant, and cadmium at the waste dump. This does not classify the sites as contaminated but indicates excessive levels. It is also important to emphasize the uncertainty of the gained results which are inaccurately high. However, comparing the sites in the study, the concentration of zinc was significantly higher at both sites compared to the reference site regarding both soil and maize. A significant difference was also found for copper at WWTP regarding soil and at WD regarding maize. In general, there were tendencies for higher amounts of heavy metals at the study sites compared to the reference site, indicating that farming at the study sites has a higher probability to affect human health compared to farming at the reference site. Regarding tolerable daily intake, consumption was exceeded for cadmium and lead at all sites including zinc for children. Copper consumption was also exceeded for children at the waste dump.

Unfortunately, this study was limited by several factors such as broken equipment and the results must be interpreted with this in mind. Recommended future actions are to perform a thorough risk assessment at the locations with improved methods and also include other hazards such as pathogens. In general, waste management should be made a higher priority where waste is disposed in a better way, e.g. a landfill, and cultivations at contaminated sites are avoided.