Introduction: The purpose of our study was to determine the distribution of copper (Cu) in topsoils from urban public parks across Leicester and its rural surroundings (Leicestershire, England).
Methods: A total of 850 topsoil samples were collected (2017–18). A total of 26 composite samples were appropriately prepared after mixing samples collected per location (18 urban, 8 rural), which were further processed in duplicate. Cu was measured twice in each of the 52 composite samples via ICP-MS after acid/microwave digestion with nitric acid (69%)/chlorhydric acid (37%).
Results: Cu was found in all composites examined (LoD=1.335 mg/kg). Significantly higher levels were found in urban areas [43.784 (27.200, 56.190) vs. 32.678 (20.280, 35.710); data presented as median and IQR, in mg/kg; Peto–Prentice test, χ2(1)=7.4, p-value=0.007)], which might be logical as this metal is associated with traffic density. This would be supported by the enrichment factors calculated for rural topsoils (EF=0.101), which suggest minimal anthropogenic influence. Moreover, significant differences (p-value=3E-05) were found between the four ordinal directions dividing the Leicestershire region that were monitored to study the distribution of Cu, showing the following distribution: SW (51.345) > NW (43.827) > SE (37.262) > NE (20.052; all medians in mg/kg). This suggests a wide distribution of Cu in Leicestershire. Toxic risks derived from oral, inhalation, and dermal exposure to Cu from topsoils in the four ordinal directions in urban and in all rural topsoils monitored were <1, suggesting minimal non-carcinogenic risks deriving from exposure to Cu present in topsoils.
Conclusions: Thus, the presence and distribution of Cu in Leicestershire’s topsoils does not represent a significant risk for the population. In general, the range of Cu found (9.580-101.229 mg/kg) would suggest that the monitored topsoils were not polluted, if we consider the threshold proposed by the Finnish and Swedish legislations to denote unpolluted soils (100 mg/kg). However, continuous monitoring would be recommended to protect the public.