Interaction Between Fate/speciation Of Nutrient/Trace Elements And Ocean Acidification In Coastal Zone

An important but be underestimated consequences of Ocean acidification is changing the large scale of inorganic and organic chemical environment in addition to ocean carbon system of the Ocean. Similar to the carbonate chemical system, detected CO32-concentration reducing cause the concentration of HCO3- and dissolved CO2 increasing, also will lead to morphological transformation of the other weak acid associated with lower p H in acid-base balance. Knowledge about the effects of ocean acidification on fate and morphology of important elements in Marine ecosystem is rather scarce. So drawing out the effects and function mechanisms of Ocean Acidification to fate and morphology of matriculate elements and trace elements, and research geochemical characteristics of these elements in the future high CO2 concentration environment are very necessary. This research design and simulation of different level of ocean acidification(pH≈8.0, 7.5 and 7.0) in lab scale tanks, study the concentration and morphology changes of several nutrient elements(C, N, P, Si) and trace elements(Pb, Ni, Sc, V, Cd, Mn, Fe, Cu, Zn, Hg, As, Cr) before and after different levels of acidificstion in overlying waters, pore water, sediment and suspended particulate matter, and inguiry the mechanisms of these changes. Explore the effects of ocean acidification to nutrient and trace elements in water/sediment system of shallow water. In addition, according to the survey of nutrient and pH in the southwestern Laizhou bay, investigate the interaction relations between acidification and nutrient in practical environment of coastal zone; and according to the survey of trace elements(Cd, Cr, Cu, Hg, Ni, Pb, Zn and As) in sediments from intertidal zone of the southwestern Layzhou bay, examine heavy metal pollution status of the sediments, analysis and predict the effect acidification to heavy metal pollution status in sediment from intertidal zone of the southwestern Laizhou bay.The concentration of total nitrogen(TN), ammonia nitrogen(NH4-N), total phosphorus(TP), activated phosphorus(PO4-P) and dissolved silicate(DSi) in the overlying water increase with acidification, and with pH decreasig from 8.0 to 7.0, their biggest increaments reached 27.7%, 48.8%, 153%, 23.6% and 13.1%, respectively, in the simulation experiment day 1, day 30, day 60, day 7 and day 30, respectively, but the content of nitrate nitrogen(NO3-N) decrease with acidification; With the extension of acidification time the TN content showed a trend of decrease in overlying water, indicated that the influence of acidification to nitrogen in overlying water weakened with the extension of acidification time; with the degree of acidification increased and acidification prolonged, DSi content in overlying water increasing, illustrated that the effects of acidification to silicon in overlying water increase with the extension of time.The concentration of TN, NH4-N and DSi in porewater increased with acidification, The concentration of NO3-N, NO2-N, TP and PO4-P decreased with acidification, with pH decreasig from 8.0 to 7.0, their maxmum reduction reched 40.2%, 79.6%, 83.8% and 93.2% in day 30, 30, 60 and 60, respectivly; Acidification caused more ammonia nitrogen and silicate migrated to the pore water, and precipitation nitrate, nitrate and phosphate from pore water.With pH decreasing from 8.0 to 7.0, the concentration of inorganic carbon(DIC), TN and TP in sediments decreased, the maxmum reduction reched 79.2%, 26.3% and 13.9% in day 15, 1 and 7, respectively, indicating that acidification promoted they separating out from sediments; Lower degree of acidification(pH ≈ 8.0) can not cause big change in phosphorus content of the sediment, but a little higher degree of acidification(pH < 7.5) could decrease the concengtration of loose combining phosphorus, iron combining phosphorus and authigene phosphorus in the sediment, the order of the influencing was: Authigene P > iron combining P > loosely combining P.DIC content in the suspended particulate matter decreased with acidification and reched the maxmum 66.7% in day 1; TN content in the suspended particulate matter increased with acidification before 30 days and reched the maxmum 22.9% in day 30, but after 30 days TN content decreased with acidification in the suspended particulate matter; The concentration of TP, inorganic phosphorus(IP) and bioavailable phosphorus(BiaP) increased with acidification, suggested that acidification could lead to more phosphorus migration into the suspended particulate matter.Acidification can result in Fe and Mn dissolution from the sediments, and the maxmum amounts reached 48.2% and 45.9%, respectively. And then the elements combined with Fe/Mn oxides may dissolution from sediments with Fe and Mn dissolution. V, Zn, Pb, As, Cr and Cu content in sediments decreased with acidification, the order of influence degree of medium and long-term acidification(>15 days) on these element is roughly about: As > Fe > Mn > V > Cr > Zn > Pb > Cu; The content of Ni and Co in the sediments increased with acidification,the influence order was:Co>Ni;Sc and Cd content in the sediments are not sensitive to acidification;Acidification seemingly could not influence the content of Ca andΜg in sediments,but may lead to decreasing of Na content;Short-term acidification(<7days)may make Al content increaseing in the sediments,while the medium and long-term acidification may reduce Al content in sediments.The concentration of Zn, Mn, V, Ni and Sc in suspended particulate matters decreased with acidification, the order of influence degree of medium and long-term acidification(>15 days) on these elements was roughly about: Ni > Zn > Mn > Sc > V. The content of Fe and As in suspended particulate matter increased with acidification, the influence order was: Fe > As; Pb, Cr, Cu, Co and Cd in suspended particulate matters were not sensitive to acidification. Different forms of the elements demenatrated different responses to acidification.Increasing nutrient content in surface water, especially increasing the concentration of DIN and DSi may intensified acidification in the water system of coastal laizhou bay, acidification of that region is not sensitive to the nutrient structures.As, Cr, Cu, Ni, Pb and Zn in intertidal surface sediments from the southwest coast of laizhou bay were in status of no pollution and low ecological risk; But Cd and Hg were in moderate pollution status and moderate to high ecological risk status. Acidification is likely to affect the heavy metal pollution status in sediments of laizhou bay coastal zone by separating some heavy metals from sediment. The influence of acidification to Cd and Hg in that region deserved attention.