My research aims to understand catchment biogeochemical processes affecting the interactions between landscapes, their management and the resulting impacts on water quality and quantity. My studies involve examining how biological, physical and chemical processes interact to determine the fate and impacts of nutrients and other potential pollutants, such as sediments and particulate bound contaminants.

It is increasingly important that we understand coupled factors of biogeochemistry to allow us to better predict and potentially control catchment processes to our benefit. Coupled nutrient cycling is a central theme to my research and provides a good example of ‘systems thinking’ at a process level.

However, catchment ‘systems thinking’ has to cross multiple scales to involve processes from surface interactions between soils and flowing waters to the decisions that land managers make at field to farm scales, to regional and national policy drivers.

This remains a key challenge in my work as theme leader for Managing Catchments and Coasts to provide the critical fine scale knowledge necessary to inform real world decision making at larger management and regulation scales.

As land use and environmental change pressures accumulate we will be looking increasingly to sound scientific principles of biogeochemistry to help manipulate catchment systems to function more efficiently.

This means learning to enhance natural biogeochemical function or understanding constraints of where to act in catchments to optimise growing demands for biodiversity, farming, energy, places to live and economic gain. Some highlights of my recent and ongoing work are given below.

Understanding and improving water quality

I have sought to link understanding from nutrient and sediment monitoring in catchments with laboratory based experimentation and characterisation of soils, sediments and their reactions with water. This has been targeted to issues such as reducing nutrient losses from farmland and explaining rising DOC concentrations in upland soils.

I use novel combinations of analytical methods to study the dynamics of different nutrient forms (dissolved, particulate and organically-complexed) from sources, transport to in-river cycling. This feeds into the design of diffuse pollution mitigation methods aiming to reduce key sources and interrupt transport pathways.

Through upscaling I have then examined the cumulative effectiveness of these mitigation measures at field and catchment scales including appraisals of costs and other practicalities. My ‘systems biogeochemical approach’ has allowed me to address constraints of mitigation such as pollutant swapping between dissolved nutrient to gas release and between particulate to dissolved nutrient forms.

Managing riparian areas for multiple benefits

My work has shown that we cannot adopt riparian buffer strips to minimise nutrient delivery from farmland to waters without proper consideration of their management. Initial chemical studies showed high P solubility in buffer soils and further biogeochemical exploration then suggested an accelerated turnover of upslope P inputs by microbial processes.

Our improved biogeochemical process knowledge suggests a need for vegetative P mining to offset buffer P accumulation. These studies highlight riparian buffers as a critical interface for attaining multiple benefits for habitat, erosion trapping, bank stabilisation, tree shading and woody debris and wider recreational benefits.

This work aims to show that by coupling bank side and stream channel ecosystem services we can promote a more heterogeneous and resilient system against future coupled stressors of pollution and climate.

Improving phosphorus resource use efficiency

An efficient use of the P resource is crucial to sustaining agricultural production and minimising pollution of waters. My work unites aspects of promoting efficient crop acquisition of applied P, minimising losses from the field edge and recovering beneficial resources such as P from materials previously viewed as ‘wastes’ (such as sewage or anaerobic digestate).

This biogeochemical understanding is working to understand mechanisms such as how crops may compete with soils for sequestered soil P and how waste processing may optimise nutrient recovery. Read more details on the nutrient cycles page.

An improved knowledge of soil phosphorus concentrations is key to better management in matching agronomic inputs to crop requirements to minimise losses such as by soil P leaching. We are doing this with in partnership with the farming community, who are actively taking part in sampling to learn more about this resource. Learn about this project and how to get involved on the farmer led phosphorus sampling page.

Current positions

• Managing Catchments and Coasts Research Theme Leader.
• Lead of the Scottish Government’s research theme on Safe and Sustainable Supply Chains for Water and Renewable Energy.
• Member of the Management Committee for the Dee Catchment Partnership.
• Associate Editor for Journal of Environmental Quality (2012-15).
• Associate Guest Editor on special editions for both Science of the Total Environment (2012) and Journal of Environmental Quality (2010).

Active projects

• Policy delivery projects for SEPA through the Centre of Expertise for Waters: CREW: Factoring ecological significance of P into catchment source methodologies.
• CREW: Development of Guidelines for Management of Riparian Buffer Strips.
• 2012-2016: NERC and Scottish Government. The multi-scale response of water quality, biodiversity and C sequestration to coupled macronutrient cycling from source to Sea. Macronutrients Cycles Programme.
• 2010-2013: NERC. Environmental Virtual Observatory.
• 2013-2016: BBSRC. Exploiting root exudation of organic acids and phytases to enhance plant utilisation of soil phosphorus.

Current postgraduate students

• 2010-2013: Will Roberts. Soil management, retention and transport of phosphorus in riparian buffer strips. James Hutton Institute/Lancaster University
• 2012 - ongoing: Samia Richards. Tracing sources of phosphorus from small point sources in catchments. James Hutton Institute/University of Bangor
• 2011 - ongoing: Laura Cruickshank. Novel silica, lanthanide complex-doped fluorescent particles as potential soil erosion tracers. James Hutton Institute/Robert Gordon University, Aberdeen.
• 2012 - ongoing: Adam Wyness. Influence of sediment characteristics on the transport of pathogens from freshwaters to coasts. James Hutton Institute/University of St Andrews
• 2012 – ongoing: Joseph Oyesikublakemore. Integrating terrestrial and hydrological-based models to assess gaseous and aquatic C:N fluxes. James Hutton Institute/University of Aberdeen.