1. State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871 Beijing 100085, China, National Food Quality Supervision and Inspection Center, China National Research Institute of Food and Fermentation Industries, 32 Xiaoyun Road, Beijing 100027, China, and Centre de recherche TOXEN, Université du Québec à Montréal, Case Postale 8888, Succursale Centre-ville, Montréal, Québec, Canada H3C 3P8