Environmental quality and sources of heavy metals in the topsoil based on multivariate statistical analyses: a case study in Laiwu City, Shandong Province, China

To provide a basis for soil environmental risk pre-warning, management and pollution remediation, 560 topsoil samples (0–20 cm) were collected from farmland soil in Laiwu. The environmental quality of heavy metals in soil was evaluated with Nemerow pollution index, and the sources and spatial distribution features of heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) were investigated with the multivariate statistical analysis method. The results showed that the average amounts of As were 8.80 ± 4.05 mg kg−1, Cd 0.15 ± 0.09 mg kg−1, Cr 74.21 ± 44.82 mg kg−1, Cu 27.92 ± 11.44 mg kg−1, Hg 0.05 ± 0.20 mg kg−1, Ni 36.10 ± 24.92 mg kg−1, Pb 28.81 ± 18.90 mg kg−1 and Zn 74.54 ± 41.69 mg kg−1, respectively. These eight heavy metals do not exceed the national secondary standard value except for As, but the average amounts of the other seven kinds of heavy metals were higher than the soil natural geological background of Shandong Province. Eight kinds of heavy metals could be divided into three principle components: PC1 (Cd, Pb and Zn) was mainly influenced by agriculture and industry as well as transportation; PC2 (Cr and Ni) was natural element; and PC3 (As and Hg) was relevant to the exploitation of mine, the coal combustion and irrigation with polluted water. Cu was considered to be affected by nature and human activity and had a relatively bigger loading. The major soil of researched area was better than Class III of Nemerow multifactor index which has high environmental quality, and virtually no soil studied exceeded the Class III of Nemerow multifactor index.