Abstract
The overall objective of this project is to investigate the impact on the agricultural landbank available for the recycling of organic and inorganic materials (in England and Wales) of potential changes in soil metal loading rates and limit values. One of the objectives of the draft `Soil Strategy for England` consultation document is to establish the degree of risk from recycling organic materials to soils and the consequences for human, animal and plant health and the environment, and to seek to keep these risks at an acceptable level. As part of the implementation of this strategy, Defra are considering whether to introduce new soil metal limits (maximum permissible soil metal concentrations) which should be used across all regulatory regimes. This project will feed into Priority Work Area 4 of the draft `Soil Strategy for England` and will support the Welsh Soil Strategy, by determining the potential impact of introducing new soil metal limits on the landbank available for recycling organic and inorganic materials containing heavy metals. In more detail, the project will: 1. Review practices in other countries on how returns to agricultural land of organic materials containing potentially toxic elements (PTEs) are regulated. The review will summarise the contrasting ways in which diffferent countries (European and non-European) regulate heavy metal and organic contaminant inputs in various organic materials, and will compare limits on heavy metal concentrations in the organic materials applied, limits in receiving soils and and limits to nutrient/metal loading rates. 2. Update the Defra `Agricultural Soil Heavy Metal Inventory` with more recent data on the metal content of different types of farm manures, data on the metal content of other organic materials going to land and, if appropriate, more robust data on the atmospheric deposition of metals. The Inventory is a useful tool for determing the relative contribution of different sources of heavy metal inputs to agricultural soils and can be used to identify whether inputs from a particular source (e.g. farm manures, sewage sludge, compost) have changed in importance over time, due to changes in the regulatory framework or farming practices. 3. Calculate the temporal capacity (in years) of soils to reach current maximum permitted soil metal concentrations as specified in the Code of Practice for Agricultural Use of Sewage Sludge and other suggested revised maximum permissible soil metal concentrations. Using the Inventory tool, a series of calculations will be undertaken to estimate the length of time it would take for soils (using a present day baseline) to reach a series of selected metal limit concentrations based on inputs from farm manures, sewage sludge, compost, fertilisers, atmospheric deposition etc. and accounting for losses via crop offtake and leaching. 4. Update the ALOWANCE software to be compatible with the new (2009) Nitrate Vulnerable Zone Action Programme (NVZ-AP) rules and run a range of scenarios using ALOWANCE-PLUS at different soil metal limits, at increments along the scale between current and proposed maximum permissible soil metal concentrations. This will enable an assessment of the effect on the landbank available for organic material additions if maximum permissible soil metal concentrations were to change, and to determine the responsiveness of the land bank to such changes. An important part of this work will be to spatially disaggregate the temporal capacity for each of these scenarios (i.e. to produce maps for England and Wales of the time it would take to reach a series of maximum permissible soil metal concentrations) and to determine the local impacts of changing the maximum permissible soil metal concentrations.
United Kingdom