Study On Water Environmental Assessment And Environmental Carrying Capacity Of Shantou Port

Shantou Port, an important Port in East Guangdong, is one of the main transit ports in thecoastal areas of China and a natural deep-water port with the shortest distance to Taiwan inGuangdong. Shantou Port will get a new round of rapid development with the development ofEconomic Zone on the West Coast of the Taiwan Strait and application of the―double-shift‖strategy in Guangdong. But Shantou Port became seriously polluted with a continued trend ofdeterioration. So, it is necessary to investigate and evaluate the ecological environment ofShantou Port systematically to coordinate the economic development and the ecologicalenvironmental remediation and ensure the sustainable development in Shantou Port. In this study,the survey of the ecological environment in Shantou Port was done from March 2009 to March2010 and the marine water quality, the phytoplanktonic diversity, the environmental capacity andthe environmental carrying capacity of the port was assessed.In the survey, six sections were set in Shantou port with a monthly survey at low tide. Theaverage concentrations of dissolved oxygen (DO), chemical oxygen demand (COD), dissolvedinorganic nitrogen (DIN) and labile phosphate (PO4-P) in this port were respectively 5.83g·m^-3,1.98 g·m^-3, 95.15×10-3mol·m^-3, and 2.6×10 - 3 mol·m^-3. The correlation of environmentalfactors showed that the significant correlation between salinity and NO₃-N, DIN, PO4-P, COD(r=-0.673, -0.684, -0.461, -0.498) and the significant correlation between NO₃-N and DIN(r=0.929), which indicated that the main polluted sources of the bay were sewage discharge andrunoff and NO₃-N was the main component of inorganic nitrogen. By the fuzzy comprehensiveevaluation, the water quality in Shantou Port was GradeⅣin each section following thenational marine water quality standard (GB 3097-1997); DIN and PO4-P were the majorpollutants; and the water quality in the western part of the port was worse than that in the easternpart, especially the zone near Queshi Bridge was the worst. The survey indicated 322 species of phytoplankton, including 234 species of diatom, 141fresh-water and half-fresh-water species and 64 species of red tide organisms. Averageabundance, diversity index (Shannon-Wiener index, H') and evenness index (J) were3.13×107cells?m-3, 2.53 and 0.57 respectively. Skeletonema costatum and Oscillatoria sp. werethe dominant species throughout the year, with 0.066 and 0.038 of dominance index, respectively.Correlation between temperature and phytoplankton community structure (r=0.699, p<0.01)explained the temporal pattern of phytoplankton community structure in this port well. Therelationship between abundance and environmental factors showed that phytoplankton growthwas limited by the intensity of light. The different correction between algal groups andenvironmental factors indicated that much nutrient and COD were inputted by fresh water fromupper stream. With MDS and Pearson Correlation, fluctuations in phytoplankton communitystructure were mainly affected by temperature, salinity and pH.A simply two-dimensional model of water quality model was built and used to estimate theenvironmental capacity of the port with a method invented by Shiyu Li et al. (1999), stated as themaximization of total discharged pollutant loads, subject to the satisfaction of environmentalstandards imposed on the sea water quality of check points which were set along the boundary ofwater bodies of different utility functions. The environmental capacit ies of COD_Mn wererespectively 30653T·a^-1 and 29360T·a^-1 in the environmental conditions in 1999 and 2009 bymodeling. Comparison of the environmental capacities in the two years showed that the mainsources were runoff and municipal wastewater discharge. The environmental capacity calculatedprovided the basis for the pollution control program made or modified and its effectivenessevaluation.Estuarine environmental carrying capacity was defined and the evaluation index systemfor analyzing the environmental carrying capacity of Shantou Port was established. Then, theenvironmental carrying capacities of Shantou Port from 2005 to 2009 were assessed with theevaluation index system by the state space method coupling with the entropy method. The resultshowed that the environmental carrying capacities of Shantou Port were in low level from 2005 to 2008, and there was the same level for socio-economic part from 2005 to 2007 and for eco-environmental part from 2006 to 2009; and the environmental carrying capacities fitted a good state in 2009 and there was the same for socio-economic part in 2008 and 2009 and for eco-environmental part in 2005. The study of the comparison of environmental carrying capacities for some years was of great scientific significance for the layout of Shantou port and the industrial upgrading and restructuring in the port.