Study On The Coupling Relationship Of PH, Water Temperature With Both Heavy Metals And Zooplankton Community In Sea Area Near Zhanjiang Baosteel Power Plant

In order to save resources, a growing number of power plants have been constructed in coastal areas for using natural seawater to cooling and desulfurization process. The impact of discharge from flue gas desulfurization system on marine ecological environment has caused extensive attention of the society. The drainage can directly lead to the decrease in pH and the increase of water temperature then forming a natural scale near outfall. The data of pH, water temperature, concentration of heavy metals and zooplankton community in sea area near outfall of Zhanjiang power plant had been monthly investigated from February 2015 to February 2016. The distribution of concentration of heavy metals and the relationship with pH, water temperature were analyzed. Zooplankton community structure, biodiversity indexes and their relations to pH and water temperature were studied. This research can provide fundamental information for relevant departments to manage discharge from flue gas desulfurization system. The main results showed that:(1) The horizontal distribution of pH in sea area near outfall of Zhanjiang power plant was affected by tidal fluctuation.The affected area was mainly west of outfall during flood tide, and distributed in the east of outfall during ebb tide. The range of affected area during flood tide was bigger than in the ebb under the influence of terrain. The drainage could affect the range of pH in the seawater within 500 meters from outfall during spring tide and within 1000 meters during neap tide. The affected distribution levels also related to degree of pH decrease.(2) The horizontal distribution of water temperature in the study area was affected by tidal fluctuation, so the distribution rule was similar to pH. The range of affected area was influenced by the temperature rise of discharge. Three degrees increase in water temperature would cause that water warmed up in the west of outfall during ebb tide and in the east during flood tide wihin 500 meters.(3) Cu, Zn, total Cr, Cd, Pb, Ni, Hg and As accorded with the second categories of sea water quality standard(GB3079-1997)in research field. The discharge had less impact on distribution of heavy metals and had no effects on the water quality beyond 1000 meters.Because of disturbances from wharf and channel, concentration of heavy metals would increase.(4) The content of Zn, total Cr, Pb, Ni was negative correlation to pH and negative correlation between concentration of Cu, Cd, Hg, As and pH was not apparent. The content of Zn, total Cr, Pb, Ni was positive correlation to seawater temperature and relationship between concentration of Cu, Cd, Hg, As and temperature was not obvious.(5) A total of 119 zooplankton taxa and 48 pelagic larvae were identified belonging to16 groups in sea area near outfall of Zhanjiang power plant. The order of zooplankton taxa species number from highest to lowest was: summer(106 species), autumn(81 species),spring(68 species), and winter(55 species). Noctiluca scientillans was predominated species that dominance was 0.973 in spring; there were 8 dominant species in summer and15 in autumn; only 7 dominant species were discovered in winter. Both Pavocalanus crassirostris and Cirripedia nauplius were the dominant species in summer, autumn and winter. Acartia pacifica was dominant zooplankton in spring, autumn and winter.(6) The mean abundance value of zooplankton was12973.4ind/m3. Abundance and the distribution of zooplankton were significantly different according to the season. Abundance was highest in spring because of rich nutrients from the South China Sea, next was in summer and autumn, and the least was in winter. In summer, abundance was lower within1000 meters from outfall; in spring and autumn, abundance was higher in the section 500 meters from outfall; in winter, abundance progressively decreased as the distance from outfall increased. The mean biomass of zooplankton was 1021.0mg/m3. From season, the value of biomass in spring was higher than that in summer, autumn and winter, which in accordance with abundance. From the spatial distribution of biomass, biomass was lower in outfal in spring; in summer, biomass was lower within 1000 meters from outfall; in autumn and winter, biomass progressively decreased as the distance from outfall increased.(7) The seasonal difference of biodiversity indexes of zooplankton was significant.Seasonal variability of Shannon-Weaner diversity and Margalef species richness index was similar, autumn> summer> winter> spring.The order of Pielou′s evenness index from highest to lowest was: winter, autumn, summer and spring. From the horizontal distribution,diversity indices were all higher than the mean value in sea area of outfall; evenness indices were higher than the mean value except that in autumn; richness indices were higher than the mean value except that in winter. Abundance was positive correlation to biomass and numbers of zooplankton species; relationship between abundance and diversity index was negative in spring and summer, and was positive in autumn and winter,because the abundance of dominant species was larger; abundance was negative correlationto evenness index and richness index. Relationship between biomass and biodiversity indexes was not obvious. The correlation in diversity index, richness index and evenness index was positive.(8) In spring, pH was positive correlation to abundance and biomass, and water temperature was negative correlation to them. In summer, correlation between pH and abundance was positive, and water temperature was negative correlation to abundance and biomass. In autumn, relationship between pH and abundance was positive,and negative correlation between pH and biomass are significant; water temperature was negative correlation to abundance and was positive correlation to biomass. In winter, pH was significantly negative correlation to abundance and biomass, and water temperature was highly significantly positive correlation to them.(9) In spring, pH was positive correlation to species and richness index, and was negative correlation to diversity index and evenness index; water temperature was positive correlation to diversity index and evenness index, and was negative correlation to species.In summer, relationship between pH and biodiversity indexes were all negative and relationship between water temperature and biodiversity indexes were all positive. In autumn, pH was negative correlation to species and richness index, and was positive correlation to evenness index; water temperature was positive correlation to species and richness index. In winter, pH was negative correlation to species and diversity index, and was positive correlation to richness index; water temperature was positive correlation to species and diversity index, and was negative correlation to evenness index and richness index.