We are seeking a highly motivated student to carry out PhD research in the fields of environmental health, soil and agricultural science, and human pathogen ecology. The successful candidate will be based at the University of Stirling, supervised by Professor Richard Quilliam, and become fully embedded within the SPACES project (https://www.stir.ac.uk/news/2020/november-2020/385m-stirling-led-study-to-tackle-impact-of-plastic-pollution-in-africa/), the Plastic Vectors Project (https://plasticvectors.stir.ac.uk/), and the “Environmental Sustainability & Human Health Research Group” https://eshh-stirling.com/ at the University of Stirling.
Rural-urban migration in sub-Saharan Africa is one of the most important factors contributing to rapid population growth. Upsurge of urban populations has outpaced sanitation infrastructure and service delivery, causing about 80% of wastewater generated from urban centres to end up in the environment in its untreated form, with less than 5% of city populations having sewerage connections. A rise in urban population has increased the demand for food, and although cereals can be transported from rural areas, perishable crops like vegetables lose their market value during transportation, as refrigeration is scarce. Urban and peri-urban farmers in sub-Saharan Africa commonly produce perishable crops such as leafy vegetables for sale in local markets. Such provision of fresh food is crucial for providing a continual supply of vitamin-rich vegetables to urban communities. However, observational data suggests that urban and peri-urban soils used for growing crops are already heavily contaminated with plastics. Most vegetables are grown in river-valleys where wastewater constitutes the only available surface water for irrigation, especially in the dry season. Use of wastewater in urban vegetable farms not only lessens the pressure on water resources but also increases water productivity through reuse of water and nutrients.
Wastewater irrigation is often associated with enteric pathogens and microplastic contamination. It has been suggested that plastics, and microplastics, can provide a novel hydrophobic ecological habitat capable of supporting diverse microbial communities. This so-called ‘Plastisphere’ has the potential to act as a significant vector of potentially pathogenic and harmful microorganisms, particularly if the plastic has been in contact with a source of faecal contamination. The human health impact of growing vegetables in urban soils contaminated by plastics, and further irrigating them with wastewater contaminated with faecally associated pathogens and a potential high load of microplastics, is unclear. This PhD studentship, therefore, aims to test the hypothesis that plastics can facilitate the transfer of enteric diseases such as dysentery, diarrhoea, typhoid and cholera into agricultural soil and even directly into crop plants. Specifically, this PhD studentship aims to quantify the potential for microplastic contamination of vegetable crops grown in urban soils, and the risk of transferring enteric human pathogenic bacteria.
The student will begin by growing vegetable crops and artificially irrigating them with wastewater contaminated with various concentrations of microplastics colonised by a cocktail of human pathogenic bacteria, and then quantifying persistence dynamics under a range of manipulative conditions. The successful student will be encouraged to develop their own research questions and experiments depending upon their interests, but there will also be the opportunity for the student to carry out a field season in either Tanzania or Malawi as part of the wider SPACES research project.