| In this paper, nutrient criteria variables were chosen for optimization through a number of investigations and analysis. Meanwhile, the influence mechanism of salinity (TDS) was analyzed to explore the possibility of using TDS as the nutrient impacting variables of the Mongolia-Xinjiang plateau. Finally, the lake nutrient criteria values of the Mongolia-Xinjiang plateau were chosen by using lake population distribution approach. This study would be of great importance in scientifically evaluating the health status of lakes and determining the goals of governance and restoration.The database of potential nutrient variables of the Mongolia-Xinjiang plateau was established by the history data collection and field monitoring of the physiochemical index, biological index and the basin comprehensive index of potential nutrient variables. Then we figured out nutrient variables that could characterize lake eutrophic states by analysis of contribution ratio and correlation of potential nutrient variables through regression analysis, principal component analysis and correlation analysis. We considered the scientificalness, independence, stability, representative. Then we screened out chlorophyll-a, total nitrogen, total phosphorus and transparency as the nutrient criteria variables of the Mongolia-Xinjiang plateau through analysis.Meanwhile, the influence mechanism of salinity (TDS) was analyzed to explore the possibility of using TDS as a nutrient impacting variable of the Mongolia-Xinjiang plateau.1) Integrated regression equation indicated that, total phosphorus and TDS were the key environmental physical and chemical factors affecting chlorophyll-a. The relationship between the nutrient and biological variables was analyzed in typical examples in the Mongolia-Xinjiang plateau. The results showed that, dissolved oxygen, pH, total nitrogen, chlorophyll-a, transparency were significant factors that affected TDS. It was presented a significantly negative relationship between dissolved oxygen, pH and TDS, a significantly positive relationship between total nitrogen, chlorophyll-a, and TDS, and a positive relationship between transparency and TDS.2) The TDS’s influence on the growth and activity of antioxidant enzymes of Microcystis aeruginosa were studied in this paper. The results showed that the high-salinity stress (2,4g/L) inhibited the growth of Microcystis aeruginosa under NaCl and Na2SO4treatments. The salinity formed by Na2SO4played a more significantly role on algae growth than that formed by NaCl. The activities of antioxidant enzymes (SOD, CAT) decreased with salt stress time after increased trend at first. The activity of antioxidant enzymes under high-salinity stress (2,4g/L) was significantly higher than that under low-salinity stress (0.5,1g/L). Salinity stress resulted in membrane lipids of peroxidation of Microcystis aeruginosa and the rise of the content of MDA, which might impact the normal function of the cell membrane negatively.Finally, lake nutrient criteria values in the Mongolia-Xinjiang plateau were chosen through lake population distribution approach. The criteria value of chlorophyll a, total nitrogen concentration, total phosphorus concentration and transparency in freshwater lake (TDS<1g/L),0.676mg/m3,0.120mg/L,0.005mg/L, and1.90m, respectively, were recommended. The criteria value of chlorophyll a, total nitrogen concentration, total phosphorus concentration and transparency in micro-salt lake (1-2g/L) should be0.494mg/m3,0.675mg/L,0.005mg/L, and2.478m, respectively. The criteria value of chlorophyll a, total nitrogen concentration, total phosphorus concentration and transparency in the lagoons (2-50g/L) should be0.950mg/m3,0.728mg/L,0.012mg/L, and3.00m, respectively. The criteria value of chlorophyll a, total nitrogen concentration, total phosphorus concentration and transparency in salt lake (>50g/L) should be5.258mg/m3,1.250mg/L,0.010mg/L, and0.45m, respectively. |
