Study of marine new productivity using low-level radioactivity measuring technique

Primary productivity is the rate of autotroph producing organism through photosynthesis and new productivity is that supportedby nutrient element imported into euphotic zone and that is equal with net export of particulate organic carbon under steady state condition. So new productivity in euphotic zone is assimilating capacity with carbon imported from outside and supporting capacity to product of high trophic level. In euphotic zone, the distributions of ²³⁸U and ²²⁶Ra are rather homogeneous, but their daughters ²³⁴Th and ²¹⁰Pb can be easily absorbed by suspension particulate and sink down. That shows an image that is very similar with biogenic particulate absorbing carbon and sink down. People measure contents and distributions of ²³⁸U, ²²⁶Ra and ²³⁴Th and ²¹⁰Pb in seawater using measurement technique of low-level radioactivity and study particulate dynamics and new productivity of euphotic zone through disquilibrium relations. This paper introduces contents mentioned above, significance of new productivity and the study progress of new productivity in China. (author)