ADVANCE IN STUDY ON METHOD FOR OXYGEN ISOTOPIC ANALYSIS OF PHOSPHATE IN SOIL AND ITS APPLICATION

Zhang Han;Wang Jiani;Guo Qingjun;Zhang Xian;Zhu Yongguan;Institute of Urban Environment,Chinese Academy of Sciences;Institute of Geographic Sciences and Natural Resources Research,Chinese Academy of Sciences;

Phosphate in soil;;Oxygen isotope composition;;Phosphate sources;;Phosphorus cycling

Phosphorus is a nutrient essential to all living organisms in the soil. Researches have demonstrated that oxygen isotope in phosphate is an important tracer for source and cycling of the phosphate in the ecosystem. This type of researches in based theoretically on the hypothesis that under natural surface temperature and p H conditions,P-O bond in phosphate is quite stable and not likely to get hydrolyzed easily However,in the process of enzyme mediated biological activity,the P-O bond would break,leading to fractionation of oxygen isotopes,which means that oxygen isotope fractionation in phosphate is primarily controlled by biological activity. As phosphate in soil is often very limited in natural abundance and a large quantity of organic matter exists in soil,how to remove the interference of oxygen from other sources in the soil is the key to determination of oxygen isotopes in phosphate that needs several rounds of enrichment,isolation and purification. This paper summarizes the theoretical basis and analytical technique,including methods for extraction andpurification and instrumental analysis of soil inorganic P in the study on oxygen isotopes in soil phosphate,reviews recent progresses in the study on application of phosphate oxygen isotopes as tracer ti determining source of the phosphate in soil and cycling of phosphate in the ecosystem,and puts forth methods for extraction of organic phosphate in soil and the use of18O-labeled and enriched phosphate in the study,which will further help deepen the knowedge about phosphorus transport in soil.