Selected trace metals （Pb, Cd, Cu, Hg） and arsenic in seawater and surface sediments of Laizhou Bay were determined, to evaluate their spatial distribution, pollution risk and potential ecological risk. Concentratio...Selected trace metals （Pb, Cd, Cu, Hg） and arsenic in seawater and surface sediments of Laizhou Bay were determined, to evaluate their spatial distribution, pollution risk and potential ecological risk. Concentrations of the elements were 0.56-2.07, 0.14-0.38, 12.70-18.40, 0.014-0.094, and 1.13- 2.37 μg/L in the seawater and 8.94-32.2, 0.18-0.67, 4.51-30.5, 0.006-0.058, and 5.75-15.3 mg/kg in sediments for Pb, Cd, Cu, Hg and As, respectively. High concentrations of the trace metals and arsenic in seawater and surface sediments were generally observed near the fiver estuary. The pollution risk result of the elements showed that Cu was the prominent trace metal pollutant in seawater, followed by Hg, Pb, Cd and As. The metal complex pollution index in seawater was at a medium level. The most important trace metal pollutant in sediments was Cd, followed by As, Cu, Pb, and Hg. Our pollution assessment suggests that trace metal pollution in Laizhou Bay sediments was at a low level. The potential ecological risk was also low in surface sediment.展开更多
The influencing factors of surface alloying layer by evaporative pattern casting technology were investigated.A certain thickness alloying layer was formed on the surface of Mg-alloy matrix when the pouring temperatur...The influencing factors of surface alloying layer by evaporative pattern casting technology were investigated.A certain thickness alloying layer was formed on the surface of Mg-alloy matrix when the pouring temperature was 780°C with different vacuum degree and alloying powder size.The surface layer microstructure,micro area composition of the new phase formed on the matrix and the composition characteristics on the surface layer were examined by SEM and element scanning.The results show that the content of aluminum increases greatly on the surface layer.The micro-hardness of alloyed layer has a more obvious increase compared with that of the matrix.The size of alloying element and the vacuum degree are the key factors influencing the alloying layer,with the increase of element powder size from 0.074 to 0.15 mm and vacuum degree from 0.04 to 0.06 MPa,the surface alloying effect becomes better.展开更多
With the enhanced warming and acidification of global ocean, whether and to what extent the naturally-weathered flu- vial sediment into the sea can release elements and thus influence the geochemical process and ecosy...With the enhanced warming and acidification of global ocean, whether and to what extent the naturally-weathered flu- vial sediment into the sea can release elements and thus influence the geochemical process and ecosystem of global ocean remain to be resolved. In this contribution, an experimental study was carried out to examine the release rates of major elements （Ca, K, Mg and AI） from the surface sediments in the Changjiang （Yangtze River） Estuary under the pH values of 4.0, 6.0 and 7.0. The two stud- ied sediments consist primarily of quartz, plagioclase, calcite and clay minerals, with the BET （Brunauer, Emmett and Teller） surface areas of 61.7m2g-1 and 23.1 m2g-1. Major elements of Ca, K, Mg and A1 show different release rates under different solution pH values. With the decreasing solution pH, the release rates of Ca and K increase obviously, while the release rates of Mg and A1 in- crease with the initial solution pH varying from 6.0 to 7.0. The different release rates of these elements are closely related to the original mineral composition of the sediments and the reaction kinetics. Based on the experimental observation, quartz and clay min- erals that have low dissolution rates may dominate the major element release to the aqueous phase. This study reveals that the en- hancing ocean acidification could cause considerable release of major elements from natural terrigenous sediments into the ambient marine environment, which has to be considered carefully in the future study on global change.展开更多
基金Supported by the Shandong Key Laboratory of Marine Ecological Restoration,Shandong Marine Fisheries Research Institute(No.201211)the National Natural Science Foundation of China(No.41206120)
文摘Selected trace metals （Pb, Cd, Cu, Hg） and arsenic in seawater and surface sediments of Laizhou Bay were determined, to evaluate their spatial distribution, pollution risk and potential ecological risk. Concentrations of the elements were 0.56-2.07, 0.14-0.38, 12.70-18.40, 0.014-0.094, and 1.13- 2.37 μg/L in the seawater and 8.94-32.2, 0.18-0.67, 4.51-30.5, 0.006-0.058, and 5.75-15.3 mg/kg in sediments for Pb, Cd, Cu, Hg and As, respectively. High concentrations of the trace metals and arsenic in seawater and surface sediments were generally observed near the fiver estuary. The pollution risk result of the elements showed that Cu was the prominent trace metal pollutant in seawater, followed by Hg, Pb, Cd and As. The metal complex pollution index in seawater was at a medium level. The most important trace metal pollutant in sediments was Cd, followed by As, Cu, Pb, and Hg. Our pollution assessment suggests that trace metal pollution in Laizhou Bay sediments was at a low level. The potential ecological risk was also low in surface sediment.
基金Project(50775085)supported by the National Natural Science Foundation of China
文摘The influencing factors of surface alloying layer by evaporative pattern casting technology were investigated.A certain thickness alloying layer was formed on the surface of Mg-alloy matrix when the pouring temperature was 780°C with different vacuum degree and alloying powder size.The surface layer microstructure,micro area composition of the new phase formed on the matrix and the composition characteristics on the surface layer were examined by SEM and element scanning.The results show that the content of aluminum increases greatly on the surface layer.The micro-hardness of alloyed layer has a more obvious increase compared with that of the matrix.The size of alloying element and the vacuum degree are the key factors influencing the alloying layer,with the increase of element powder size from 0.074 to 0.15 mm and vacuum degree from 0.04 to 0.06 MPa,the surface alloying effect becomes better.
基金supported by research funds awarded by the National Natural Science Foundation of China (Grant Nos. 41225020 and 41376049)Continental Shelf Drilling Program (Grant No. GZH201100202)China Geologic Survey (Grant No. GZH201100203)
文摘With the enhanced warming and acidification of global ocean, whether and to what extent the naturally-weathered flu- vial sediment into the sea can release elements and thus influence the geochemical process and ecosystem of global ocean remain to be resolved. In this contribution, an experimental study was carried out to examine the release rates of major elements （Ca, K, Mg and AI） from the surface sediments in the Changjiang （Yangtze River） Estuary under the pH values of 4.0, 6.0 and 7.0. The two stud- ied sediments consist primarily of quartz, plagioclase, calcite and clay minerals, with the BET （Brunauer, Emmett and Teller） surface areas of 61.7m2g-1 and 23.1 m2g-1. Major elements of Ca, K, Mg and A1 show different release rates under different solution pH values. With the decreasing solution pH, the release rates of Ca and K increase obviously, while the release rates of Mg and A1 in- crease with the initial solution pH varying from 6.0 to 7.0. The different release rates of these elements are closely related to the original mineral composition of the sediments and the reaction kinetics. Based on the experimental observation, quartz and clay min- erals that have low dissolution rates may dominate the major element release to the aqueous phase. This study reveals that the en- hancing ocean acidification could cause considerable release of major elements from natural terrigenous sediments into the ambient marine environment, which has to be considered carefully in the future study on global change.
