Co-occurrence of macroplastics, microplastics, and legacy and emerging plasticisers in UK soils

Despite a theoretical link between plastic and plasticiser occurrence in the terrestrial environment, there are few em-pirical studies of the relationship between these contaminants in soils. We carried out a field study to assess the co -occurrence of plastic waste, and legacy and emerging plasticisers in UK soils (n = 19) from various land uses (wood-lands, urban roadsides, urban parklands, landfill-associated). Surface plastics and soil microplastics were quantified and characterised using ATR-FTIR and mu-FTIR. Eight legacy (phthalate) and three emerging (adipate, citrate, trimellitate) plasticisers were quantified using GC-MS. Surface plastics were found at higher prevalence at landfill -associated and urban roadside sites, with levels significantly (2 orders of magnitude) greater than in woodlands. Microplastics were detected in landfill-associated (mean 12.3 particles g-1 dw), urban roadside (17.3 particles g-1 dw) and urban parkland (15.7 particles g-1 dw) soils, but not in woodland soils. The most commonly detected poly-mers were polyethene, polypropene and polystyrene. Mean n-ary sumation plasticiser concentration in urban roadside soils (3111 ng g-1 dw) was significantly higher than in woodlands (134 ng g-1 dw). No significant difference was found between landfill-associated (318 ng g-1 dw) and urban parkland (193 ng g-1 dw) soils and woodlands. Di-n-butyl phthalate (94.7% detection frequency) and the emerging plasticiser trioctyl trimellitate (89.5%) were the most com-monly detected plasticisers, with diethylhexyl phthalate (493 ng g-1 dw) and di-iso-decyl phthalate (96.7 ng g-1 dw) present at the highest concentrations. n-ary sumation plasticiser concentrations were significantly correlated with surface plastic (R2 = 0.23), but not with soil microplastic concentrations. Whilst plastic litter seems a fundamental source of plasticisers in soils, mechanisms such as airborne transport from source areas may be as important. Based on the data from this study, phthalates remain the dominant plasticisers in soils, but emerging plasticisers are already wide-spread, as reflected by their presence in all land uses studied.