Source Identification and Apportionment of Soil Cadmium in Cropland (Meishan Basin, Changxing): A Combined Approach of Fmdm, PCA, PMF, and GIS.

Source identification and apportionment of soil cadmium in cropland (Meishan Basin, Changxing): A Combined Approach of FMDM, PCA, PMF, and GIS
 Yuyou Zhi ·Jiachun Shi^* ·Laosheng Wu^*

College of Environmental and Natural Resource Sciences, Zhejiang University, 310058 Hangzhou, China

*Corresponding author Email: jcshi@zju.edu.cn, laowu@zju.edu.cn

Abstract Cadmium (Cd) is a toxic pollutant in environment. To identify the sources of Cd in Meishan Basin, Changxing County, Zhejiang Province, China, and apportion their respective contributions, 127 topsoil samples and 21 subsoil samples were collected and analyzed. Finite mixture distribution model (FMDM) was employed to fit the data to obtain the local soil Cd threshold value, a crucial indicator to assess soil pollution. According to the result of FMDM, 71 samples were subject to Cd contamination with a mean concentration of 0.66 mg kg^-1 while the other 56 samples were viewed as background with a low mean concentration of 0.145 mg kg^-1, approaching to local background concentration of 0.142 mg kg^-1. Further, principal component analyses (PCA) and GIS were used to identify the potential sources of Cd. Three components were extracted and interpreted as background, lead (Pb) battery plant, and construction material plant, respectively. And most of the topsoil samples around the Pb battery plants and constructions were classified as Cd contamination. Finally positive matrix factorization (PMF) was applied to apportion the contributions from the three sources. Results indicated Cd contamination only originated from anthropogenic activities-Pb battery plants and construction material plants. It was, however, inappropriate to exclude geogenic factors. Thus it seemed improper to apply PMF in this study, which may result from the high skewness or outliers of Cd concentration in sampling sites and violation of the assumption that all samples have the same sources.

Keywords Cadmium (Cd) · source identification · source apportionment · finite mixture distribution model (FMDM) · principal component analysis (PCA) · positive matrix fraction (PMF)