Contaminants of emerging concern in agricultural systems: a risk to soil and plant health?

In order to sustainably secure global food for a growing population, it is critical that crop dependence on chemical-based fertilisers (e.g. nitrogen, phosphorus, potassium) is reduced and alternative water supplies identified which address water scarcity issues. Agriculture is the largest consumer of available freshwater (70%) with demand expected to increase by a further 19% by 2050. The depletion of global phosphorus and potassium reserves within 100 years also pose major threats to future fertiliser supply and our ability to grow enough food.
One of the most promising options to secure future agricultural productivity is the use of wastewater treatment by-products, including sludges and Treated Wastewater (TWW). However, chemicals used in our everyday lives, including pharmaceuticals (e.g. prescription and non-prescription), personal care products (e.g. soaps, disinfectants) and fibres (e.g. plastics) can pass through wastewater treatment plants and contaminate the TWW and sludges. These pollutants are referred to collectively as "contaminants of Emerging Concern" (ECs). Our ability to boost yields and nutritional content of food to meet future demand may be impacted by the presence of ECs in soil-plant systems.
Pharmaceuticals, in particular, are biologically active chemicals and their presence in agricultural systems could result in undesired toxic effects for plant, soil and human health. Pharmaceuticals are now ubiquitous global contaminants; however, our scientific understanding of potential ecosystem risks posed by these pollutants is scarce, especially in agricultural systems. Research has established that plants can accumulate pharmaceuticals that persist in soils, but we know very little about impacts of >1,500 pharmaceuticals estimated to be in current use on plant and soil health and ultimately crop productivity. The proposed programme of research for the first phase of the Fellowship aims to fill these knowledge gaps by uniting scientific expertise to explore the:
1. Impact of pharmaceuticals associated with sludges and TWW on soil functioning in relation to maintaining sustainable agricultural production
2. Accumulation and effects of pharmaceuticals on plant health and implications for crop productivity
3. Assessment of the risks in the future (20-100 years) accounting for changes in land use, climate and associated changes in application rates of sludges and TWW
The second phase of the Fellowship will use the science platform created during the first phase to investigate the impact of a wider range of ECs that have the potential limit agricultural productivity such as nanomaterials and plastics as well as exploring solutions to mitigate against observed effects. Application of wastewater by-products to land is an accepted practice in a number of countries where populations have a relatively high use of pharmaceuticals (e.g Israel, Southern Europe, Southwest US). Pharmaceuticals have been identified in soils receiving sludges and TWW, and coupled with a recent drive to increase the use of TWW for agricultural irrigation in countries experiencing water shortages, there is an urgent need to establish the global risks of these chemicals in our agricultural systems. Whilst the UK does not currently use TWW for agricultural irrigation, the Environment Agency has suggested there will be significant water supply deficits in the UK by the 2050s. TWW may therefore offer a means of supplementing our demand for freshwater irrigation; however, this solution must be evaluated to ensure environmentally safe protocols are established which promote agricultural sustainability. Outputs of this research will also provide effective evidence for use by non-academic end users (e.g. environmental regulators, water industry, agricultural sector), guiding post-Brexit TWW reuse policies to ensure the UK maintains a world-leading position on mitigating risks of ECs in the environment whilst maximising sustainable reuse.

The ultimate aim of this Fellowship is to address global and regional grand challenges concerning the impacts of Emerging Contaminants (ECs) on the plant-soil system and in doing so generate world-leading research that delivers impacts to a variety of end users encompassing the environment, economy and society. We currently know very little about impacts of ECs on crop development and soil health, which have the potential to affect crop yield, sustainable agricultural production. This Fellowship will provide a step change in our current knowledge regarding the input, fate, plant uptake and effects of ECs in agricultural systems. This is a timely proposal that feeds directly into CGIAR's "4 per 1,000" initiative and has potential to inform key UN Sustainable Development Goals (SDGs), namely: Zero Hunger, Clean Water and Sanitation and Responsible Consumption and Production.
The first phase (0-4 years), will enable significant advancements in understanding agricultural risks resulting from Treated Wastewater (TWW) irrigation and sludge application to land. Outputs will help:
- UK Water Industry Research (UKWIR) address their 'Big Questions', including Q5 How will we deliver an environmentally sustainable wastewater service that meets customer and regulator expectations by 2050? and Q11 How do we turn all wastes we receive and generate into products by 2030?
- Farmers who use sludges and TWW to enable them to better manage these resources to increase their agricultural productivity and profitability (e.g. Israel, Southwest US, Southern Europe). There is a drive to increase TWW use in agriculture through subsidies in water scarce regions (e.g. half the tariff (US$0.3 m3) of freshwater ($0.66 m3) in Israel)
In the second phase of this Fellowship (5-7 years) thresholds for levels of ECs in sludge and TWW (determined in WP4) will inform longer-term policies around TWW and sludge reuse. The need to increase water reuse at a global (Coping with water scarcity: An action framework for agriculture and food security (FAO)) and EU level (A Blueprint to Safeguard Europe's Water Resources (COM(2012)673)) has been acknowledged. Impacts will therefore include:
- Uptake by environmental regulators in countries where sludge and TWW are routinely used without prior consideration of the transfer of ECs to land (i.e. Israel Ministry for Agriculture, US Environmental Protection Agency)
- Evidence for future policy in countries who have potential to adopt these practices in an attempt to mitigate against projected water scarcity combined with the need to dispose of wastewater by-products (e.g. UK: Environment Agency (EA), Defra). In 2012, approximately 3million m3 of TWW was reused (golf course irrigation); however, the UK does not currently use TWW in agriculture. With 4,249million m3 of wastewater treated in 2012 alone, the UK has potential to use this to meet annual agricultural demand for water estimated to be in excess of 1,200 million m3
- Establishment of Soil Screening Values (SSV) for ECs as part of the EA initiative to asses ecological risk of chemicals derived from landspreading of wastes
- Contribute to establishing minimum requirements for water reuse as acknowledged in existing EU documents (COM(2018)337). Forming policy related to TWW reuse will be of particular importance after Brexit, where policy decisions will be made independently of existing EU policy
Beyond the Fellowship (7+ years) outcomes of this will inform:
- Worldwide policy frameworks such as SAICM (Strategic Approach to International Chemicals Management)
- UNESCO and OECD programmes on ECs in wastewater
- Development of soil diagnostic tools for decision making to help determine optimum timing for sludge or TWW reuse
- Water industry advancements in water treatment technologies, targeted at removing particularly 'risky' chemicals
- Pharmaceutical companies to pursue 'greener' alternatives in their drug development, and improve waste disposal initiatives