The changes in soil organic carbon(C) mineralization as affected by anthropogenic disturbance directly determine the role of soils as C source or sink in the global C budget. The objectives of this study were to inves...The changes in soil organic carbon(C) mineralization as affected by anthropogenic disturbance directly determine the role of soils as C source or sink in the global C budget. The objectives of this study were to investigate the effects of anthropogenic disturbance(aquaculture pond, pollutant discharge and agricultural activity) on soil organic C mineralization under different water conditions in the Minjiang River estuary wetland, Southeast China. The results showed that the organic C mineralization in the wetland soils was significantly affected by human disturbance and water conditions(P < 0.001), and the interaction between human disturbance activities and water conditions was also significant(P < 0.01). The C mineralization rate and the cumulative mineralized carbon dioxide-carbon(CO_2-C)(at the 49th day) ranked from highest to lowest as follows: Phragmites australis wetland soil > aquaculture pond sediment > soil near the discharge outlet > rice paddy soil. This indicated that human disturbance inhibited the mineralization of C in soils of the Minjiang River estuary wetland, and the inhibition increased with the intensity of human disturbance. The data for cumulative mineralized CO_2-C showed a good fit(R^2 > 0.91) to the first-order kinetic model C_t = C_0(1 – exp(–kt)). The kinetic parameters C_0, k and C_0 k were significantly affected by human disturbance and water conditions. In addition, the total amount of mineralized C(in 49 d) was positively related to C_0, C_0 k and electrical conductivity of soils. These findings indicated that anthropogenic disturbance suppressed the organic C mineralization potential in subtropical coastal wetland soils, and changes of water pattern as affected by human activities in the future would have a strong influence on C cycling in the subtropical estuarine wetlands.展开更多
Minerals which enter lake-marsh ores composition are very diverse. There are two large classes of ores： ferrous and manganese-ferrous ores. Each class is divided into groups according to its mineral composition. In t...Minerals which enter lake-marsh ores composition are very diverse. There are two large classes of ores： ferrous and manganese-ferrous ores. Each class is divided into groups according to its mineral composition. In this investigation, ferrous ore sample （Chagodostcha） and manganese-ferrous ore samples （Totyma-2 and Mologa-2） were considered. All samples in the initial state are contaminated with a-quartz and Ab-An feldspars. Thus for purification of the samples, direct flotation method with kerosene agent were used. As a result, almost all impurities were removed from the samples. With the X-ray diffraction method, the authors identified following phases： goethite （ferrous ore） and birnessite （manganese-ferrous ores）. Also, the authors used electron probe microanalysis of the original and purified probes and it showed the presence of such impurities as Ca, K, Mg and Ba in birnessite from the manganese-ferrous ores, and AI and Mn impurities in goethite from the ferrous ore. All ore minerals are in a nanocrystalline state （crystallite size is about 10 nm）.展开更多
基金Under the auspices of National Basic Research Program of China(No.2012CB956100)National Natural Science Foundation of China(No.41301085)the Key Foundation of Science and Technology Department of Fujian Province(No.2016R1032-1)
文摘The changes in soil organic carbon(C) mineralization as affected by anthropogenic disturbance directly determine the role of soils as C source or sink in the global C budget. The objectives of this study were to investigate the effects of anthropogenic disturbance(aquaculture pond, pollutant discharge and agricultural activity) on soil organic C mineralization under different water conditions in the Minjiang River estuary wetland, Southeast China. The results showed that the organic C mineralization in the wetland soils was significantly affected by human disturbance and water conditions(P < 0.001), and the interaction between human disturbance activities and water conditions was also significant(P < 0.01). The C mineralization rate and the cumulative mineralized carbon dioxide-carbon(CO_2-C)(at the 49th day) ranked from highest to lowest as follows: Phragmites australis wetland soil > aquaculture pond sediment > soil near the discharge outlet > rice paddy soil. This indicated that human disturbance inhibited the mineralization of C in soils of the Minjiang River estuary wetland, and the inhibition increased with the intensity of human disturbance. The data for cumulative mineralized CO_2-C showed a good fit(R^2 > 0.91) to the first-order kinetic model C_t = C_0(1 – exp(–kt)). The kinetic parameters C_0, k and C_0 k were significantly affected by human disturbance and water conditions. In addition, the total amount of mineralized C(in 49 d) was positively related to C_0, C_0 k and electrical conductivity of soils. These findings indicated that anthropogenic disturbance suppressed the organic C mineralization potential in subtropical coastal wetland soils, and changes of water pattern as affected by human activities in the future would have a strong influence on C cycling in the subtropical estuarine wetlands.
文摘Minerals which enter lake-marsh ores composition are very diverse. There are two large classes of ores： ferrous and manganese-ferrous ores. Each class is divided into groups according to its mineral composition. In this investigation, ferrous ore sample （Chagodostcha） and manganese-ferrous ore samples （Totyma-2 and Mologa-2） were considered. All samples in the initial state are contaminated with a-quartz and Ab-An feldspars. Thus for purification of the samples, direct flotation method with kerosene agent were used. As a result, almost all impurities were removed from the samples. With the X-ray diffraction method, the authors identified following phases： goethite （ferrous ore） and birnessite （manganese-ferrous ores）. Also, the authors used electron probe microanalysis of the original and purified probes and it showed the presence of such impurities as Ca, K, Mg and Ba in birnessite from the manganese-ferrous ores, and AI and Mn impurities in goethite from the ferrous ore. All ore minerals are in a nanocrystalline state （crystallite size is about 10 nm）.
