GEOCHEMICAL SURVEY OF BLACK LAND IN NORTHEAST CHINA: Progress and Prospect

The black land in Northeast China, as one of the significant four black soil areas in the world, known for high organic matter and high fertility, plays a pivotal role in ensuring national food security. The Northeast Plain is tectonically located in the active zone of Eurasia Plate continental margin, undergoing multistage complex geological process and environmental evolution and gradually forming the present black land. The mineral compositions of black soil mainly include illite, vermiculite, kaolinite and montmorillonite. With black soil degradation in the land transferring process into farmland after reclamation, there are also some major geological problems such as disunified geological survey methods, weak basic geological study and inadequate comprehensive research. At present, by means of land quality geochemical survey and RS technology, significant progress has achieved in the fields of black land quality, land quality limiting factors and interaction mechanism, black soil formation time and environment, integrated satellite-aero-ground survey methods for key area of black land and screening of selenium-rich land resources. The future exploration and research should focus on long-term observation base monitoring with international cooperation, geological program for black land restoration, elemental geochemical cycle mechanism, black soil formation and evolution theory, and land resources "double evaluation" techniques to ensure the sustainable utilization of black soil.