1. School of Public and Environmental Affairs; Indiana University; MSBII, Walnut Grove Avenue, Bloomington IN 47405-2204 USA
2. Faculty of Environmental Science; VNU University of Science, Vietnam National University; Hanoi (VNU), 334-Nguyen Trai, Thanh Xuan, Hanoi Vietnam
3. Institute of Soil Science; Leibniz Universität Hannover; Herrenhäuser Straße 2, 30419 Hannover Germany
4. Institute of Applied Geosciences; Technical University Darmstadt; Schnittspahn Street 9, 64287 Darmstadt Germany