A field trial was set up to examine the movement of microplastics and viruses in soils amended with biosolids and their effect on crop growth. Different biosolid products (following a range of treatment methods) were applied to a sandy clay loam soil and sown with a new grass ley. Agronomic rates of biosolid were applied and compared with a green compost, a fertiliser only treatment and a fertiliser+microplastics treatment (with the same quantity of microplastics loading as in the biosolids application). Measurements of microplastics and viruses were made in the topsoil immediately after application and at the time of grass harvest. Grass yield and quality were also measured. 

Aerial view of the field trial set up at Henfaes Research Centre, Bangor. The yellow stars indicate treatment plots and the blue star shows the location of the nearest watercourse.

We have also sampled existing sites with known histories of biosolids application to investigate the levels of viruses and microplastics present in soils where biosolids have been used over a longer period, but these have not been fully analysed yet.