1. School of Resources and Environment, Anhui Agricultural Univ.; Hefei 230036 People's Republic of China
2. Dep. of Chemistry and Biochemistry; Old Dominion Univ.; Norfolk VA 23529 USA
3. USDA-ARS, National Lab. for Agriculture and the Environment; Ames IA 50011 USA
4. Princess Anne High School; Virginia Beach VA 23462 USA
5. Agronomy Dep.; Iowa State Univ.; Ames IA 50011 USA