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As deep space exploration activities increase worldwide, the exploration environment becomes increasingly complex and the exploration tasks become increasingly difficult. Therefore, it is of great practical significance to research on deep space security issues. In this study, we first clarify the basic connotation of deep space security, briefly describe the significance and key issues of deep space security research, and summarize the research status and future development of four key deep space security issues: space radiation threat, planetary protection, space heritage protection, and space legislation. The study indicates that space radiation has the characteristics of multiple threat sources and high radiation intensity and should be researched from the perspectives of physical, biomedical, and chemical protection. Planetary protection mainly faces the challenges of pollution and impact of deep space spacecraft, and research should be conducted from the perspectives of deep space microbial detection and disinfection technologies as well as policy formulation. Space heritage protection is controversial in terms of evaluation and protection measures owing to political, cultural, and legal differences among countries, and it should be researched from the perspectives of international cooperation, deep space spacecraft, and reduction of human impact. Due to the complex international relations among countries, it is difficult for the effectiveness of current laws and regulations to become the consensus of the international community; therefore, research should be conducted from the aspects of international legislative organizations, domestic research institutions, and the improvement of domestic legal systems.

With the effective control of industrial wastewater, pollution of non-point sources has become increasingly important in China. The understanding of non-point source pollution processes, mostly through mathematical models, is thus a prior knowledge to its effective control. A review is presented in this paper, regarding the development of non-point source pollution models. The conceptualization, structure and major processes of non-point source models are systematically summarized and several widely applied models are compared so as to assess its state of art. The future development trends of non-point source model are also discussed.