Background soils are frequently utilized as a surrogate to assess pollution levels and environmental risks of heavy metals in Chinese lakes. However, there remains a lack of understanding regarding the reliability and uncertainty of such assessments. Here, we determined heavy metals (As, Cd, Co, Cr, Cu, Hg, Ni, Pb, and Zn) in sediment cores from five rural lakes in North China to evaluate the reliability and uncertainty of the assessments using background soils by comparing them with assessments based on background sediments. Comparative studies reveal large uncertainties in the assessments using background soils. Among these metals, uncertainties for Hg and Cd are relatively large, whereas those for the other metals are minor. This discrepancy is due to the considerably higher natural variability of Hg and Cd in soils and sediments in comparison to the other metals. Generally, assessments utilizing background soils underestimate pollution levels and risks of Hg but overestimate those of Cd in these lakes. Despite limited human activities around the lakes, they still received a considerable influx of heavy metals via regional atmospheric transport. Assessments of the nine metals indicate moderate to considerable ecological risks in these lakes. The risks are contributed primarily (78–89%) by Hg and Cd. This study underscores the substantial uncertainties in assessing heavy metal pollution and risks using regional background soils and emphasizes the importance of controlling atmospheric emissions of Hg and Cd to mitigate pollution in rural and remote water bodies in China.

To investigate ecological risks and spatial distributions of heavy metals in atmospheric particles in the Beijing urban area, atmospheric dust was collected from 62 sites and 12 heavy metals in their <63 μm fractions were measured. Results indicate that V, Cr, Mn, Co, Ni, and Ba in the dust are basically unpolluted by human activities; whereas Cu, Zn, As, Cd, Sb, and Pb are moderately to heavily polluted. These metals (not including Ba) in most dust show a high ecological risk (RI = 809 ±585, ranging 291-4,848), predominantly contributed by Cd (71%) and Sb (14%). Relatively higher risks mainly occur in the eastern and northwestern urban areas. The high risks in the east are caused mainly by Cd pollution associated with coal-burning and industrial and traffic activities, while those in the northwest are caused mainly by Sb pollution associated with point pollution sources and Cd pollution from traffic activity. This is significant for controlling atmospheric heavy metal pollution over the Beijing urban area and investigating atmospheric metal pollution in other cities.