X⁃ray fluorescence spectroscopy was used to explore the spatial distribution characteristics and potential ecological risks of heavy metals (Cu, Pb, V, Zn, Cr, Mn) in street dust in different functional areas of the city.The heavy metal content in the dust samples of the cultural and educational districts, commercial districts, residential areas, industrial areas, traffic areas and mixed areas in Benxi City was analyzed,and the results show that the average contents of heavy metals in street dust samples are 3.4, 3.1, 0.9, 5.5, 2.0 and 1.0 times of the Benxi Soil Element Background Values, respectively. The spatial distribution of heavy metal elements was that Cu, V and Cr were highest in the cultural and educational districts, Pb, Zn and Mn were highest in the industrial districts, Cu, Pb and Zn were lowest in the mixed districts, Cr and Mn were lowest in the commercial districts, and V was lowest in the residential districts. The environment risk of heavy metal pollution in street dust of Benxi city was assessed by Potential Ecologically Risk Index .The assessment results show that V, Cr and Mn are low potential ecological hazards, Zn is a medium potential ecological hazard, Cu and Pb have reached heavy potential ecological hazards.

Photocatalytic technology can convert solar energy into chemical energy under mild reaction conditions and promote the degradation of organic pollutants. As a new type of non⁃metal semiconducting polymer, graphite phase carbonitride has unique electronic structure and good chemical stability. In recent years, it has received extensive attention in the field of photocatalysis, but graphite phase carbonitride itself has some shortcomings. However, graphite⁃phase carbon nitride itself has some shortcomings, for example, the forbidden band width is 2.7 eV, which can absorb only blue⁃violet light of less than 475 nm in sunlight, photo⁃generated carriers are easy to recombine, quantum efficiency is low, and specific surface area is small, which needs to be modified to improve photocatalytic performance. In this paper, the research progress of graphite⁃phase carbon nitride in structure optimization, precious metal deposition, semiconductor composite, element doping, dye sensitization, carbon composite and its application prospect in the field of environmental pollution purification are reviewed.