Understanding organic matter characteristics （e.g., amount and state） of sediments is necessary for evaluating both the sediment and water environments; however, methods that have been proposed to investigate these ...Understanding organic matter characteristics （e.g., amount and state） of sediments is necessary for evaluating both the sediment and water environments; however, methods that have been proposed to investigate these characteristics are relatively expensive. This study attempted to evaluate the organic matter characteristics of littoral sediments by employing solely the loss on ignition （LOI） method, which is the most economical and accessible method in developing countries. Different types of sediments were first oven dried at 100 ~C and then continuously burned at 200, 300, 400, 500, and 600 ~C for 4 h at each temperature. The mass LOI at each temperature was calculated and compared with the 100 ℃oven-dried weight. Our results suggested that the mass LOI across the temperature range of 200-300 ℃（LOI200-300）：mass LOI at 600 ℃ （LOI600） ratio （LOI200-300/LOI600） could represent different types of sediments as well as the organic matter：organic C ratio. Compared with the sediments unaffected by wastewater, the sediments that were more influenced by the inflow of domestic wastewater had a higher LOI200-300/LOI600. Interestingly, LOI200-300/LOI600 could also represent changes in the organic matter characteristics as a function of organic matter decomposition in sediments. In conclusion, the organic matter characteristics of littoral sediments could be evaluated using solely the LOI method, particularly with LOI200 - 300/LOI600.展开更多
This paper studies the effective polytropic index in the central plasma sheet （CPS） by using the method of Kartalev et al. （2006）, which adopts the denoising technique of Haar wavelet to identify the homogeneous M...This paper studies the effective polytropic index in the central plasma sheet （CPS） by using the method of Kartalev et al. （2006）, which adopts the denoising technique of Haar wavelet to identify the homogeneous MHD Bernoulli integral （MBI） and has been frequently used to study the polytropic relation in the solar wind. We chose the quiet CPS crossing by Cluster C1 during the interval 08：51：00-09：19：00 UT on 03 August 2001. In the central plasma sheet, thermal pressure energy per unit mass is the most important part in MBI, and kinetic energy of fluid motion and electromagnetic energy per unit mass are less important. In the MBI, there are many peaks, which correspond to isothermal or near isothermal processes. The interval lengths of homogenous MBI regions are generally less than 1 min. The polytropic indexes are calculated by linearly fitting the data of lnp and Inn within a 16 s window, which is shifted forward by 8 s step length. Those polytropic indexes with IRI ≥0.8 （R is the correlation coefficient between lnp and inn） and p-value≤0.1 in the homogeneous regions are almost all in the range of [0, 1]. The mean and median effective polytropic indexes with high R and low p-value in homogeneous regions are 0.34 and 0.32 respectively, which are much different from the polytropic index obtained by traditional method （αtrad=-0.15）. This result indicates that the CPS is not uniform even during quiet time and the blanket applications of polytropic law to plasma sheet may return misleading value of polytropic index. The polytropic indexes in homogeneous regions with a high correlation coefficient basically have good regression significance and are thus credible. These results are very important to understand the energy transport in magnetotail in the MHD frame.展开更多
基金the Grantin-Aid for Science Research from the Japan Society for the Promotion of Science (Nos.26820204 and 26630229)
文摘Understanding organic matter characteristics （e.g., amount and state） of sediments is necessary for evaluating both the sediment and water environments; however, methods that have been proposed to investigate these characteristics are relatively expensive. This study attempted to evaluate the organic matter characteristics of littoral sediments by employing solely the loss on ignition （LOI） method, which is the most economical and accessible method in developing countries. Different types of sediments were first oven dried at 100 ~C and then continuously burned at 200, 300, 400, 500, and 600 ~C for 4 h at each temperature. The mass LOI at each temperature was calculated and compared with the 100 ℃oven-dried weight. Our results suggested that the mass LOI across the temperature range of 200-300 ℃（LOI200-300）：mass LOI at 600 ℃ （LOI600） ratio （LOI200-300/LOI600） could represent different types of sediments as well as the organic matter：organic C ratio. Compared with the sediments unaffected by wastewater, the sediments that were more influenced by the inflow of domestic wastewater had a higher LOI200-300/LOI600. Interestingly, LOI200-300/LOI600 could also represent changes in the organic matter characteristics as a function of organic matter decomposition in sediments. In conclusion, the organic matter characteristics of littoral sediments could be evaluated using solely the LOI method, particularly with LOI200 - 300/LOI600.
基金supported by the National Natural Science Foundation of China(Grant Nos.41431071,41174141,41474124)the National Basic Research Program of China(Grant No.2011CB811404)
文摘This paper studies the effective polytropic index in the central plasma sheet （CPS） by using the method of Kartalev et al. （2006）, which adopts the denoising technique of Haar wavelet to identify the homogeneous MHD Bernoulli integral （MBI） and has been frequently used to study the polytropic relation in the solar wind. We chose the quiet CPS crossing by Cluster C1 during the interval 08：51：00-09：19：00 UT on 03 August 2001. In the central plasma sheet, thermal pressure energy per unit mass is the most important part in MBI, and kinetic energy of fluid motion and electromagnetic energy per unit mass are less important. In the MBI, there are many peaks, which correspond to isothermal or near isothermal processes. The interval lengths of homogenous MBI regions are generally less than 1 min. The polytropic indexes are calculated by linearly fitting the data of lnp and Inn within a 16 s window, which is shifted forward by 8 s step length. Those polytropic indexes with IRI ≥0.8 （R is the correlation coefficient between lnp and inn） and p-value≤0.1 in the homogeneous regions are almost all in the range of [0, 1]. The mean and median effective polytropic indexes with high R and low p-value in homogeneous regions are 0.34 and 0.32 respectively, which are much different from the polytropic index obtained by traditional method （αtrad=-0.15）. This result indicates that the CPS is not uniform even during quiet time and the blanket applications of polytropic law to plasma sheet may return misleading value of polytropic index. The polytropic indexes in homogeneous regions with a high correlation coefficient basically have good regression significance and are thus credible. These results are very important to understand the energy transport in magnetotail in the MHD frame.
