1. Guangdong Key Laboratory of Integrated Agro-environmental Pollution Control and Management, Guangdong Institute of Eco-Environmental Science and Technology, Guangzhou, P. R. China;
2. Chinese Academy of Sciences, Guangzhou Institute of Geochemistry, Guangzhou, P. R. China;
3. Graduate University of The Chinese Academy of Sciences, Guangzhou Institute of Geochemistry, Beijing, P. R. China