赤水河是长江上游一级支流,生境类型复杂多样,在长江上游珍稀特有鱼类资源保护方面发挥着至关重要的作用.为了解赤水河健康状况,本研究于2020年5月和9月,在赤水河干流和重要一级支流31个点位开展鱼类调查,采用Shannon-Wiener指数、Simp...赤水河是长江上游一级支流,生境类型复杂多样,在长江上游珍稀特有鱼类资源保护方面发挥着至关重要的作用.为了解赤水河健康状况,本研究于2020年5月和9月,在赤水河干流和重要一级支流31个点位开展鱼类调查,采用Shannon-Wiener指数、Simpson指数、Pielou指数评价鱼类多样性,构建了F-IBI(fish-based index of biotic integrity)指数评价赤水河健康状况.此次调查共采集6288尾,隶属于4目10科26属90种;鱼类Shannon-Wiener指数范围为0.21~2.87,平均值为1.48±0.46;Simpson指数范围为0.08~0.91,平均值为0.69±0.14;Pielou指数范围为0.13~0.97,平均值为0.76±0.13.上游至下游Shannon-Wiener指数和Simpson指数均呈现逐渐升高的变化规律.构建了包含物种总数、鲤形目个体数%、鮈亚科个体数%、鲌亚科个体数%等10个指标在内的F-IBI核心指标体系,采用比值法计算各点位F-IBI值,根据F-IBI值将流域健康状况划分为“健康”(F-IBI≥5.99)、“亚健康”(4.49≤F-IBI<5.99)、“一般”(2.99≤F-IBI<4.49)、“较差”(1.50≤F-IBI<2.99)和“极差”(F-IBI<1.50)5个等级.评价结果显示,所调查点位整体为健康状态,20个点位显示健康状态,5个点位显示亚健康状态,3个点位显示一般状态,3个点位显示较差状态.F-IBI值从上游到下游呈现逐渐上升趋势,且上、中、下游F-IBI值存在显著性差异(P<0.05).干流健康状况优于支流,较差健康点位位于桐梓河、五马河流域,一般健康点位位于习水河流域.研究显示,赤水河鱼类以鲤形目、鲤科为主要种群,构建的F-IBI评价体系可作为人类活动干扰的良好的预测因素,较好地反映赤水河水生生态系统健康状况,可作为赤水河水生生态系统健康评价和资源管理的工具.展开更多
It is not easy to construct a model to describe the geochemical background in geochemical anomaly detection due to the complexity of the geological setting.Isolation forest and its improved algorithms can detect geoch...It is not easy to construct a model to describe the geochemical background in geochemical anomaly detection due to the complexity of the geological setting.Isolation forest and its improved algorithms can detect geochemical anomalies without modeling the complex geochemical background.These methods can effec-tively extract multivariate anomalies from large volume of high-dimensional geochemical data with unknown population distribution.To test the performance of these algorithms in the detection of mineralization-related geochemical anomalies,the isolation forest,extended isolation forest and generalized isolation forest models were established to detect multivariate anomalies from the stream sediment survey data collected in the Wu-laga area in Heilongjiang Province.The geochemical anomalies detected by the generalized isolation forest model account for 40%of the study area,and contain 100%of the known gold deposits.The geochemical anomalies detected by the isolation forest model account for 20%of the study area,and contain 71%of the known gold deposits.The geochemical anomalies detected by the extended isolation forest algorithm account for 34%of the study area,and contain 100%of the known gold deposits.Therefore,the isolation forest mo-del,extended isolation fo-rest model and generalized isolation forest model are comparable in geochemical anomaly detection.展开更多
Based on field investigation and study of petrology, mineralogy, geochemistry and isotopic geochronology for the granodiorite, the authors discussed the formation setting of the granodiorite. The pluton is calci alkal...Based on field investigation and study of petrology, mineralogy, geochemistry and isotopic geochronology for the granodiorite, the authors discussed the formation setting of the granodiorite. The pluton is calci alkalic and peraluminous granite in which light rare earth elements (LREE) are intensively enriched, heavy rare earth elements are relatively poor, the ratio of LREE to heavy rare earth elements (HREE) is 7.12, and the fractionation of REE is good. The pluton formed in late orogenic setting which is relatively steady.展开更多
A total of 67 samples from the upper and lower sediment traps in the central South China Sea were analyzed, which were collected during 1993~1996. It is indicated that the distribution of stable isotope values, surfac...A total of 67 samples from the upper and lower sediment traps in the central South China Sea were analyzed, which were collected during 1993~1996. It is indicated that the distribution of stable isotope values, surface primary productivity, fluxes of total particulate matter, carbonate, biogenic opal, organic carbon, planktonic foraminiferal species and their total amount exhibit obviously seasonal and annual fluctuations. High values of the fluxes occurred in the prevailing periods of the northeastern and southwestern monsoons, and the low values occurred during the periods between the two monsoons. The fluxes of some planktonic foraminiferal species (Globigerinoides sacculifer, G. ruber, Globigerinita glutinata, Neogloboquadrina dutertrei) and their percentages also exhibit two prominent peaks during the prevailing periods of the northeastern and southwestern monsoons respectively, while those of Globigerina bulloides, Globorotalia menardii and Pulleniatina obliquiloculata only exhibit one peak in the prevailing periods of the northeastern monsoon. In addition, fluxes and percentages of Globigerinoides sacculifer and Globorotalia menardii as well as the fluxes of carbonate and total amount of planktonic foraminifera decrease gradually from 1993 to 1996, and those of Globigerina bulloides, Globigerinita glutinata and biogenic opal increase gradually from 1993 to 1996. The fluxes of carbonate and organic carbon in the upper trap are higher than those in the lower one. The study indicates that the seasonal and annual variations of the sediment fluxes and planktonic foraminiferal species are mainly controlled by the changes of surface primary productivity and hydrological conditions related to the East Asian monsoon. The lower carbonate and organic carbon fluxes in the lower trap are related to the dissolution.展开更多
文摘赤水河是长江上游一级支流,生境类型复杂多样,在长江上游珍稀特有鱼类资源保护方面发挥着至关重要的作用.为了解赤水河健康状况,本研究于2020年5月和9月,在赤水河干流和重要一级支流31个点位开展鱼类调查,采用Shannon-Wiener指数、Simpson指数、Pielou指数评价鱼类多样性,构建了F-IBI(fish-based index of biotic integrity)指数评价赤水河健康状况.此次调查共采集6288尾,隶属于4目10科26属90种;鱼类Shannon-Wiener指数范围为0.21~2.87,平均值为1.48±0.46;Simpson指数范围为0.08~0.91,平均值为0.69±0.14;Pielou指数范围为0.13~0.97,平均值为0.76±0.13.上游至下游Shannon-Wiener指数和Simpson指数均呈现逐渐升高的变化规律.构建了包含物种总数、鲤形目个体数%、鮈亚科个体数%、鲌亚科个体数%等10个指标在内的F-IBI核心指标体系,采用比值法计算各点位F-IBI值,根据F-IBI值将流域健康状况划分为“健康”(F-IBI≥5.99)、“亚健康”(4.49≤F-IBI<5.99)、“一般”(2.99≤F-IBI<4.49)、“较差”(1.50≤F-IBI<2.99)和“极差”(F-IBI<1.50)5个等级.评价结果显示,所调查点位整体为健康状态,20个点位显示健康状态,5个点位显示亚健康状态,3个点位显示一般状态,3个点位显示较差状态.F-IBI值从上游到下游呈现逐渐上升趋势,且上、中、下游F-IBI值存在显著性差异(P<0.05).干流健康状况优于支流,较差健康点位位于桐梓河、五马河流域,一般健康点位位于习水河流域.研究显示,赤水河鱼类以鲤形目、鲤科为主要种群,构建的F-IBI评价体系可作为人类活动干扰的良好的预测因素,较好地反映赤水河水生生态系统健康状况,可作为赤水河水生生态系统健康评价和资源管理的工具.
文摘It is not easy to construct a model to describe the geochemical background in geochemical anomaly detection due to the complexity of the geological setting.Isolation forest and its improved algorithms can detect geochemical anomalies without modeling the complex geochemical background.These methods can effec-tively extract multivariate anomalies from large volume of high-dimensional geochemical data with unknown population distribution.To test the performance of these algorithms in the detection of mineralization-related geochemical anomalies,the isolation forest,extended isolation forest and generalized isolation forest models were established to detect multivariate anomalies from the stream sediment survey data collected in the Wu-laga area in Heilongjiang Province.The geochemical anomalies detected by the generalized isolation forest model account for 40%of the study area,and contain 100%of the known gold deposits.The geochemical anomalies detected by the isolation forest model account for 20%of the study area,and contain 71%of the known gold deposits.The geochemical anomalies detected by the extended isolation forest algorithm account for 34%of the study area,and contain 100%of the known gold deposits.Therefore,the isolation forest mo-del,extended isolation fo-rest model and generalized isolation forest model are comparable in geochemical anomaly detection.
文摘Based on field investigation and study of petrology, mineralogy, geochemistry and isotopic geochronology for the granodiorite, the authors discussed the formation setting of the granodiorite. The pluton is calci alkalic and peraluminous granite in which light rare earth elements (LREE) are intensively enriched, heavy rare earth elements are relatively poor, the ratio of LREE to heavy rare earth elements (HREE) is 7.12, and the fractionation of REE is good. The pluton formed in late orogenic setting which is relatively steady.
文摘A total of 67 samples from the upper and lower sediment traps in the central South China Sea were analyzed, which were collected during 1993~1996. It is indicated that the distribution of stable isotope values, surface primary productivity, fluxes of total particulate matter, carbonate, biogenic opal, organic carbon, planktonic foraminiferal species and their total amount exhibit obviously seasonal and annual fluctuations. High values of the fluxes occurred in the prevailing periods of the northeastern and southwestern monsoons, and the low values occurred during the periods between the two monsoons. The fluxes of some planktonic foraminiferal species (Globigerinoides sacculifer, G. ruber, Globigerinita glutinata, Neogloboquadrina dutertrei) and their percentages also exhibit two prominent peaks during the prevailing periods of the northeastern and southwestern monsoons respectively, while those of Globigerina bulloides, Globorotalia menardii and Pulleniatina obliquiloculata only exhibit one peak in the prevailing periods of the northeastern monsoon. In addition, fluxes and percentages of Globigerinoides sacculifer and Globorotalia menardii as well as the fluxes of carbonate and total amount of planktonic foraminifera decrease gradually from 1993 to 1996, and those of Globigerina bulloides, Globigerinita glutinata and biogenic opal increase gradually from 1993 to 1996. The fluxes of carbonate and organic carbon in the upper trap are higher than those in the lower one. The study indicates that the seasonal and annual variations of the sediment fluxes and planktonic foraminiferal species are mainly controlled by the changes of surface primary productivity and hydrological conditions related to the East Asian monsoon. The lower carbonate and organic carbon fluxes in the lower trap are related to the dissolution.
