Historical arsenic contamination of soil due to long-term phosphate fertiliser applications

Archived samples from the Park Grass Experiment, established in 1856, were analysed to determine the impacts of long-term phosphate fertiliser applications on arsenic concentrations in soil and herbage. In plots receiving 35 kg P ha−1 annually (+P), topsoil As concentrations almost doubled from an initial value of ∼10 mg kg−1 during 1888–1947 and remained stable thereafter. The phosphate fertilisers used before 1948 contained 401–1575 mg As kg−1, compared to 1.6–20.3 mg As kg−1 in the later samples. Herbage samples from the +P plots collected during 1888–1947 contained significantly more As than those from the −P plots, but later samples did not differ significantly. Mass-balance calculations show that the increase in soil As can be explained by the As input from P fertiliser applications before 1948. The results demonstrate that the P fertilisers used on the Park Grass Experiment before 1948 caused substantial As contamination of the soil.