Micronutrient and pollution transfer in East African lake catchments: impacts on the food-water-energy security nexus

Primary supervisor: Dr Michael Watts (British Geological Survey). Email: mwatts@bgs.ac.uk

Secondary supervisor: Professor William Blake (University of Plymouth)

Additional supervisors:

Dr Andrew Marriott, (British Geological Survey). Email: anma@bgs.ac.uk

Professor Odipo Osano, (University of Eldoret-Kenya). Email: odipoosano@gmail.com

Subsistence farmers in Africa are often dependent on food grown within a limited area. Therefore, their health is often associated with geochemical factors that influence the soil-to-crop transfer of essential micronutrients (MN) for health (e.g. zinc). 

Food production and quality is compromised by soil erosion and downstream transport of sediments to waterbodies where sediment and associated nutrients/pollutants impact water security. 

Resources to manage soils sustainably can be limited, resulting in weathering and erosion of soil into waterways/catchments, such as Lake Victoria. Little is known about the loss of MN from weathering of soils and whether these are more prone to poor soil management (organic retention). 

Loss of fine soil particles may result in transfer of micronutrients or naturally occurring/anthropogenic potentially harmful elements (PHEs) into water courses/catchments with implications for ecological health. The Winam Gulf catchment of Lake Victoria is an exemplar of these processes as a regionally important source of food both from land and water.

Research, aims and objectives

  • Quantify the nutrient/micronutrient and erodibility status of soil across the Winam Gulf catchment under a range of land use histories and terrain.
  • Link sediment in transit within the system to specific spatial and land use defined source areas and processes (surface versus subsurface/gully erosion) using environmental forensic/tracer tools.
  • Integrate geospatial evidence with a GIS-based risk modeling framework permitting scenario testing of future changes in land use on MN and PHE flux.

To achieve these aims, the student will receive training in field, lab and data/statistical techniques in two phases:

  • Using on-going data capture, evaluate the potential apportionment of sediment chemistry to sources and locations from baseline soil geochemistry and sediment data collected by UK-Kenyan partners, with additional analyses on archived samples for source apportionment.
  • The student will undertake sampling in Kenya representative of differing land-use (varying timescales of land clearance) subject to different scales of soil erosion, accounting for soil geochemistry over two field seasons to better understand the chemistry and physical parameters influencing leaching of MNs/PHEs.

Person specification

The candidate should have an earth/environmental science or chemistry degree and willing to travel for fieldwork in Kenya.

This PhD proposal is important owing to the rapid development and environmental pressures in the Winam Gulf-Lake Victoria catchment (Kenya), compounded by poor coordination of environmental data (land-to-lake) to guide regulatory bodies. Road building, urbanisation around Kisumu supporting >1 million inhabitants and rapid conversion of scrub/natural environments to agricultural use, extractive industries (Gold, building materials), municipal waste, loss of soil into the shallow (<10m) Winam Gulf and limited Gulf-Lake Victoria exchange of water threaten the aquaculture industry (Gikuma-Njura 2005; Aura et al. 2013; Oyoo-Okoth et al 2013; Omwama et al 2014; Liema et al 2017). Equally, subsistence farmers require an understanding of the implications of poor soil management to minimise erosion/loss of soil nutrients and maintain conditions conducive to micronutrient soil-to-plant transfer (e.g. Se requires high pH: Hurst et al 2013; Joy et al. 2015) to maintain crop yield/food composition (micronutrient sufficiency).

To achieve the research aims & objectives the programme will focus on quantifying nutrient/micronutrient and erodibility status of soil across the catchment under a range of land-use histories and terrain. It will seek to link sediment in transit within the system to specific spatial and land-use defined source areas and processes (surface versus subsurface/gully erosion) using environmental forensic/tracer tools (Blake et al., 2018). Finally, it will integrate the geospatial evidence with a GIS-based risk modeling framework permitting scenario testing of future changes in land use on micronutrient and PHE flux.

The student will benefit from on-going projects in Western Kenya to utilise: (1) sediment/ecological data for the Lake

(2) geochemical mapping of soils and crops to understand the spatial influence on soil-crop chemistry and subsequently human health.

These projects will link to the University of Plymouth expertise in the mitigation of soil erosion (Tanzania) and methodologies for source apportionment of soil erosion-to-catchment. These projects and their existing data will inform the student on locating field experiments with local/project logistical support.

Training

In field experimental design/sampling strategy/collection, chemical analysis techniques and data interpretation tools (Bayesian models, GIS) will assist mapping of the spatial influence of geochemical/weather on soil erosion. The student will learn to interact with members of the public, address cultural concerns and dissemination of data at policy decision and farmer level.

The student will work between BGS and the University of Plymouth, utilising geochemistry lab facilities as appropriate (e.g. chemical analyses-BGS, gamma spectrometry-Plymouth), data management at BGS including planning of experimental sites through use of satellite imagery data and regional geochemical databases, interpretation of data at both institutes, with particular specialism in source apportionment for soil erosion at Plymouth. 

Whilst the student will produce new geochemical data at targeted locations, he/she will also work at a multidisciplinary level on statistical interpretation of a wider dataset for source apportionment data.

Funding

This project has been shortlisted for funding by the ARIES NERC Doctoral Training Partnership. Undertaking a PhD with ARIES will involve attendance at training events.

ARIES is committed to equality & diversity, and inclusion of students of any and all backgrounds. All ARIES Universities have Athena Swan Bronze status as a minimum.  

Applicants from quantitative disciplines who may have limited environmental science experience may be considered for an additional 3-month stipend to take appropriate advanced-level courses.

Usually, only UK and EU nationals who have been resident in the UK for three years are eligible for a stipend. Shortlisted applicants will be interviewed on 26/27 February 2019.

For further information please see www.aries-dtp.ac.uk or contact us at aries.dtp@uea.ac.uk.