Analysis of the Variation Trend and Sources of Nitrogen and Phosphorus in Qinzhou Bay in the Last 30 Years

Based on the monitoring data and historic information in Qinzhou Bay in the last thirty years, the variation trend of annual concentration and spatial distribution of DIN and DIP were analyzed. The correlation analysis and analysis of nutrient fluxes into the sea were applied to study the main sources of nutrient in Qinzhou Bay and the influencing factors of spatial distribution. The results displayed that the annual mean DIN concentration showed a wave of rising trend, the annual mean DIP concentration showed the down trend. Nitrate was the main component of DIN, with the proportion of 71%. The concentration of nutrients decreased from the inner bay to the baymouth. Land-source was the main source of inorganic nitrogen, and the nutrients carried by the river contributed more than 78% of the nutrients into the sea.