Pollution indices (PI) of heavy metals in different administrative regions.

<p>Pollution indices (PI) of heavy metals in different administrative regions.</p

Correlation coefficients among physical and chemical properties of samples.

<p>Correlation coefficients among physical and chemical properties of samples.</p

Physical and chemical properties (mean ± SD) of soils in nine land use types.

<p>Physical and chemical properties (mean ± SD) of soils in nine land use types.</p

Mean concentration (mg/kg) of heavy metals in different regions.

<p>Mean concentration (mg/kg) of heavy metals in different regions.</p

Difference of pollution index (PI ± SD) and statistical test (* <i>p</i> < 0.05) between the pre- and post- rainy seasons.

<p>F (Forest), G (grass), S (shrub), M (mixed farmland), O (orchard), SP (spring maize), SM (summer maize), W (wheat), and C (cotton).</p

Assessment of Heavy Metal Pollution in Topsoil around Beijing Metropolis

<div><p>The topsoil around Beijing metropolis, China, is experiencing impacts of rapid urbanization, intensive farming, and extensive industrial emissions. We analyzed the concentrations of Cu, Ni, Pb, Zn, Cd, and Cr from 87 topsoil samples in the pre-rainy season and 115 samples in the post-rainy season. These samples were attributed to nine land use types: forest, grass, shrub, orchard, wheat, cotton, spring maize, summer maize, and mixed farmland. The pollution index (PI) of heavy metals was calculated from the measured and background concentrations. The ecological risk index (RI) was assessed based on the PI values and toxic-response parameters. The results showed that the mean PI values of Pb, Cr, and Cd were > 1 while those of Cu, Ni, and Zn were < 1. All the samples had low ecological risk for Cu, Ni, Pb, Zn, and Cr while only 15.35% of samples had low ecological risk for Cd. Atmospheric transport rather than land use factors best explained the seasonal variations in heavy metal concentrations and the impact of atmospheric transport on heavy metal concentrations varied according to the heavy metal types. The concentrations of Cu, Cd, and Cr decreased from the pre- to post-rainy season, while those of Ni, Pb, and Zn increased during this period. Future research should be focused on the underlying atmospheric processes that lead to these spatial and seasonal variations in heavy metals. The policymaking on environmental management should pay close attention to potential ecological risks of Cd as well as identifying the transport pathways of different heavy metals.</p></div

Heavy metal concentrations (mg/kg) of measurement (MV), background (BV), and environmental quality standard for soils (EQSS).

<p>Heavy metal concentrations (mg/kg) of measurement (MV), background (BV), and environmental quality standard for soils (EQSS).</p

Significance test (*<i>p</i> < 0.05) of pollution index (PI) difference among different land use types.

<p>Significance test (*<i>p</i> < 0.05) of pollution index (PI) difference among different land use types.</p

Location of the research region and sampling sites.

<p>(The China map was generated using free, open access data sources from the National Geomatics Center of China)</p

Infiltration process under different BSCs and non-BSCs soil types.

<p>Infiltration process under different BSCs and non-BSCs soil types.</p