Evaluating a Sampling Regime for Estimating the Levels of Contamination and the Sources of Elements in Soils Collected from a Rapidly Industrialized Town in Guangdong Province, China.

Gaogang Town, a typical urban center within the Pearl River Delta region of China, suffers contamination of soils with metals/metalloids due to rapid development of industrial activities and agriculture. Few studies have been conducted to systematically describe the main sources, influencing factors, and ecological risks of metals/metalloids in soils in China. In this study, 312 surface soil samples were collected, and 15 elements were detected by plasma emission spectroscopy, atomic fluorescence spectroscopy, and atomic emission spectrometry. Element content features were analyzed by index of geo-accumulation (I), pollution load index (PLI), potential ecological risk index (RI), positive matrix factorization model (PMF), and geostatistical analysis. The PLI value is between 0 and 1, indicating that the whole study area is lightly polluted. Combining PMF model and geostatistical analysis, soil elements in surface soils of Gaogang town were quantitatively apportioned into four sources: parent material and basic substances (23.5%), natural sources (32.2%), agricultural activities and industrial pollution (22.9%), and transportation (21.4%). The comprehensive analysis results show that polluted areas are mainly distributed on roads, rivers, and industrial and human activity areas. The main sources of ecological risks are factory pollution and human activity. Finally, we found that a quarter of the sampling density was the best sample size for this study.