1. Key Laboratory of Plant Nutrition and the Agri-environment in Northwest China, Ministry of Agriculture, College of Natural Resources and Environment, Northwest A & F University, Yangling, China
2. Aix-Marseille Univ, CNRS, IRD, INRA, CEREGE, Aix-en-Provence, France
3. Program for the Environment and Sustainability, Department of Occupational and Environmental Health, School of Public Health, Texas A&M University, College Station, TX, USA