Small-scale gold mining is linked to significant environmental pollution by potentially toxic elements (PTEs). However, research on the pollution caused by such mining activities remains insufficient especially in dev...Small-scale gold mining is linked to significant environmental pollution by potentially toxic elements (PTEs). However, research on the pollution caused by such mining activities remains insufficient especially in developing countries. In the present study, a systematic investigation assessed the pollution and level of ecological risk of PTEs in soil and stream sediments in an active small scale gold mining area of Isanga, in Nzega, Tanzania. Samples amounting to 16 soil and 20 sediment were gathered from the study area and analyzed for five PTEs concentrations (As, Cd, Cr, Hg and Pb) using the AAS method. The contamination level and ecological risk were assessed using several pollution indices. The results suggest that the assessed environmental systems of the Isanga mining area and its vicinities are lowly contaminated by PTEs and have a low potential to pose ecological risks. Hg and Cd with mean concentrations of 0.09 mg/kg and 0.26 mg/kg respectively were found to be the most enriched PTEs in soil, compared to their average continental crust concentrations (0.056 mg/kg and 0.102 mg/kg respectively). The levels of the evaluated PTEs in the study area are susceptible to increase over time if proactive steps are not taken to control mining and waste disposal activities.展开更多
The geological anomaly unit method (GAUM) is a new way to delineate and evaluate ore finding targets in line with the “geological anomaly ore finding theory”. Comprehensive ore finding information from geological, g...The geological anomaly unit method (GAUM) is a new way to delineate and evaluate ore finding targets in line with the “geological anomaly ore finding theory”. Comprehensive ore finding information from geological, geochemical and geophysical data is used for quantitative measurement of the “ore forming geological anomaly unit” in this paper. The main procedures are shown as follows: (1) The geo anomalous events associated with gold mineralization are analyzed in Tongshi gold field; (2) The zonation in the concentrated heavy minerals and the stream sediment elements of ore forming geo anomaly are studied in detail; (3) The deep geological structural framework is deduced by means of the synthetic geological interpretation of gravity and magnetic information; (4) The ore controlling geo anomalies and ore anomalies are chosen as the variables of the favorable ore forming indexes that can be used for the quantitative delineation and evaluation of the potential ore forming regions.展开更多
Dynamic resource allocation(DRA) is a key technology to improve system performances in GEO multi-beam satellite systems. And, since the cache resource on the satellite is very valuable and limited, DRA problem under r...Dynamic resource allocation(DRA) is a key technology to improve system performances in GEO multi-beam satellite systems. And, since the cache resource on the satellite is very valuable and limited, DRA problem under restricted cache resources is also an important issue to be studied. This paper mainly investigates the DRA problem of carrier resources under certain cache constraints. What's more, with the aim to satisfy all users' traffic demands as more as possible, and to maximize the utilization of the bandwidth, we formulate a multi-objective optimization problem(MOP) where the satisfaction index and the spectrum efficiency are jointly optimized. A modified strategy SA-NSGAII which combines simulated annealing(SA) and non-dominated sorted genetic algorithm-II(NSGAII) is proposed to approximate the Pareto solution to this MOP problem. Simulation results show the effectiveness of the proposed algorithm in terms of satisfaction index, spectrum efficiency, occupied cache, and etc.展开更多
The form in which a metal exists strongly influences its mobility and thus, the effects on the environment. Operational methods of speciation analysis, such as the use of sequential extraction procedures, are commonly...The form in which a metal exists strongly influences its mobility and thus, the effects on the environment. Operational methods of speciation analysis, such as the use of sequential extraction procedures, are commonly applied. The Dongting Lake, the second largest fresh-water lake in China, contains three China wetlands of international importance, the East Dongting Lake, South Dongting Lake, and West Dongting Lake. In this work, an optimized BCR sequential extraction procedure was used to assess the environmental risk of Cd, Cr, Cu, Ni, Pb and Zn in contaminated sediment of the Dongting Lake. The procedure was evaluated by using a certified reference material, BCR701. The results of the partitioning study indicated that in the lake sediments, more easily mobilized forms (acid exchangeable) were predominant for Cd, particularly in the samples from the East Dongting Lake. In contrast, the largest amount of Pb was associated with the iron and manganese oxide fractions and Cu, Zn, Cr, and Ni analyzed were mainly distributed in residual phase at an average percentage greater than 60% of the total metals. The potential risk to the lake's water contamination was highest in the East Dongting Lake based on the calculated contamination factors. On the other hand, the total metal content was determined as well by inductively coupled plasma and mass spectrometry (ICP-MS) and assessed by using geo-accumulation index. The assessment results using geo-accumulation index were compared with the information on metal speciation. Both were correspondent with each other.展开更多
Encroachment, disposal of untreated domestic and industrial wastewater and dumping of solid wastes have degraded the overall quality of the river Turag, which is located in Dhaka—the Capital City of Bangladesh. The p...Encroachment, disposal of untreated domestic and industrial wastewater and dumping of solid wastes have degraded the overall quality of the river Turag, which is located in Dhaka—the Capital City of Bangladesh. The present study investigated the extent of pollution of sediments of this river and analyzed the regional variability for the concentrations of Cr, Pb, Zn, Cu and Cd—all of concern because of their potential toxicity, using atomic absorption spectrophotometer. As per US EPA sediment quality guideline, metal concentrations ranged between Cd: 0.00 - 0.80, Cr: 32.00 - 75.50, Cu: 46.30 - 60.00, Pb: 28.30 - 36.40, and Zn: 94.60 - 190.10 mg/kg in the Turag river sediments. Cr, Cu, Zn belongs to moderately to highly polluted, Pb and Cd belongs to not polluted for Turag river. The heavy metals contamination in the sediments were also evaluated by applying Index of geo-accumulation (Igeo), contamination factor (Cf), pollution load index (PLI) etc. Toxicity characteristics leaching procedure (TCLP) test (US EPA 1311) for sediment samples have been performed also for metals (Pb, Cd, Cr, Cu and Zn) to determine the readily toxicity level of heavy metals. Sieve analysis of sediment performed in this study to determine the physical characteristic of sediment samples. The metal concentrations are well below the regulated level as per US EPA. This index can be complemented with the contamination index, which allows more site-specific and accurate information on contaminant levels. If the aim of work on contamination evaluation is to assess the overall contamination of a study area, the indices are highly appropriate.展开更多
Sediment core samples were collected from the Salinas de San Pedro to assess the pollutant deposition processes in response to extensive human activities. Analysis of the sediment samples for heavy metals and some tra...Sediment core samples were collected from the Salinas de San Pedro to assess the pollutant deposition processes in response to extensive human activities. Analysis of the sediment samples for heavy metals and some trace elements was conducted with ICP-OES for 20 sites showing enrichment for some of trace and heavy metals. The results demonstrated that heavy metal concentrations in mud varied greatly for each metal, with concentration values (mg/g) ranging from 1.05 - 4.8 (Al);0.003 - 0.011(As);0.001 - 0.005 (Cd);0.02 to 0.82 (Cr);0.085 - 0.47 (Cu);5.98 - 14.22 (Fe);0.06 - 0.19 (Mn);0.03 - 0.67 (Ni);0.05 - 0.38 (Pb);- 0.069 (Se);0.18 - 0.63 (Ti);0.040 - 0.091 (V) and 0.149 - 0.336 (Zn). The Index of Geo-accumulation factor showed highest values for Pb, Mn, As, and Cu. Enrichment factors >1for these elements suggest anthropogenic inputs for most metals. The bioavailability of metals in lagoon sediments has the potential to be highly dynamic with local waste and natural H2S discharge from existing fault line.展开更多
Stream sediment samples were analyzed for the concentrations of some trace metals in the Obuasi gold mining environment, Ghana. The objectives were to determine the possible impacts of mining operations in the area on...Stream sediment samples were analyzed for the concentrations of some trace metals in the Obuasi gold mining environment, Ghana. The objectives were to determine the possible impacts of mining operations in the area on sediments’ trace metal load, and the resulting effects on agriculture and livelihoods. The concentrations of arsenic (As), copper (Cu), lead (Pb), zinc (Zn), iron (Fe), with calcium (Ca) as reference element, were compared to their respective background concentrations to calculate the enrichment and contamination factors, and also geo-accumulation and pollution load indices of each trace metal. These were in turn compared to standard tables to determine the status of contamination. Q-mode hierarchical cluster analysis (HCA) was then applied to the samples for spatial classification. This study suggests probable contribution of mining and associated activities in the Obuasi area to the concentrations of trace metals especially arsenic, in the stream sediments. Three spatial relationships were revealed based on the concentrations of these trace metals from the Q-mode HCA. The samples presented generally high concentrations, which were more profound for samples taken closer to holding pond and tailings dams, and decreased downstream.展开更多
The heavy metal contamination status of Bight of Bonny sea bed sediment w<span>as investigated. Sediment samples were collected from eleven locations grouped into three stations. The samples were analyzed to det...The heavy metal contamination status of Bight of Bonny sea bed sediment w<span>as investigated. Sediment samples were collected from eleven locations grouped into three stations. The samples were analyzed to determine the heavy met</span><span>als (Fe, Pb, Ni, Zn, Mn, Co, Cd, Cu, Cr) concentration using atomic absorption spectrophotometer. Index model analyses, such as geo-accumulation</span> index (I-geo), Enrichment factor (EF), and Pollution load index (PLI) were used for pollution assessment of sea bed sediment. The most predominant heavy metals in the upstream sediment were Fe;13.57 ± 1.838 mg/kg, cobalt;7.987 ± 3.550 mg/kg, and Ni;1.020 ± 0.802 mg/kg, midstream sediment were Fe;8.554 ± 3.010 mg/kg, Co;8.520 ± 4.00 mg/kg, and Ni;1.140 ± 0.879 mg/kg, while the downstream sediment result had Fe;11.12 ± 3.825 mg/kg, Co;7.275 ± 1.700 mg/kg, and Cd;1.025 ± 0.159 /kg. The I-geo results indicate that Cu, Mn, Pb, Cr, Fe, Zn, Ni, and Co were in their background concentrations while Cd had I-geo</span><span style="font-family:""> </span><span style="font-family:"">></span><span style="font-family:""> </span><span style="font-family:"">3 which implies a moderately or heavily polluted env<span>ironment. The EF indicates metal enrichment from anthropogenic sour</span>ces fo<span>r Co, Ni, Pb, Cd, Cu, and Cr while Fe and Mn predicate biogenic origin. The PLI of the heavy metals in the three sample stations of sea bed sediment was found to be generally low (<1). The Enrichment Factor and geo-ac</span>cumulation index strongly suggest the Bight of Bonny sea bed sediment contamination by Cd from anthropogenic sources.展开更多
文摘Small-scale gold mining is linked to significant environmental pollution by potentially toxic elements (PTEs). However, research on the pollution caused by such mining activities remains insufficient especially in developing countries. In the present study, a systematic investigation assessed the pollution and level of ecological risk of PTEs in soil and stream sediments in an active small scale gold mining area of Isanga, in Nzega, Tanzania. Samples amounting to 16 soil and 20 sediment were gathered from the study area and analyzed for five PTEs concentrations (As, Cd, Cr, Hg and Pb) using the AAS method. The contamination level and ecological risk were assessed using several pollution indices. The results suggest that the assessed environmental systems of the Isanga mining area and its vicinities are lowly contaminated by PTEs and have a low potential to pose ecological risks. Hg and Cd with mean concentrations of 0.09 mg/kg and 0.26 mg/kg respectively were found to be the most enriched PTEs in soil, compared to their average continental crust concentrations (0.056 mg/kg and 0.102 mg/kg respectively). The levels of the evaluated PTEs in the study area are susceptible to increase over time if proactive steps are not taken to control mining and waste disposal activities.
文摘The geological anomaly unit method (GAUM) is a new way to delineate and evaluate ore finding targets in line with the “geological anomaly ore finding theory”. Comprehensive ore finding information from geological, geochemical and geophysical data is used for quantitative measurement of the “ore forming geological anomaly unit” in this paper. The main procedures are shown as follows: (1) The geo anomalous events associated with gold mineralization are analyzed in Tongshi gold field; (2) The zonation in the concentrated heavy minerals and the stream sediment elements of ore forming geo anomaly are studied in detail; (3) The deep geological structural framework is deduced by means of the synthetic geological interpretation of gravity and magnetic information; (4) The ore controlling geo anomalies and ore anomalies are chosen as the variables of the favorable ore forming indexes that can be used for the quantitative delineation and evaluation of the potential ore forming regions.
基金supported by the National Science and Technology Major Project under Grant 2018ZX03001016
文摘Dynamic resource allocation(DRA) is a key technology to improve system performances in GEO multi-beam satellite systems. And, since the cache resource on the satellite is very valuable and limited, DRA problem under restricted cache resources is also an important issue to be studied. This paper mainly investigates the DRA problem of carrier resources under certain cache constraints. What's more, with the aim to satisfy all users' traffic demands as more as possible, and to maximize the utilization of the bandwidth, we formulate a multi-objective optimization problem(MOP) where the satisfaction index and the spectrum efficiency are jointly optimized. A modified strategy SA-NSGAII which combines simulated annealing(SA) and non-dominated sorted genetic algorithm-II(NSGAII) is proposed to approximate the Pareto solution to this MOP problem. Simulation results show the effectiveness of the proposed algorithm in terms of satisfaction index, spectrum efficiency, occupied cache, and etc.
基金Supported by science and technology foundation project of Xi’an Shiyou University (No. Z06098)China Geological Survey (No. 200314200021)
文摘The form in which a metal exists strongly influences its mobility and thus, the effects on the environment. Operational methods of speciation analysis, such as the use of sequential extraction procedures, are commonly applied. The Dongting Lake, the second largest fresh-water lake in China, contains three China wetlands of international importance, the East Dongting Lake, South Dongting Lake, and West Dongting Lake. In this work, an optimized BCR sequential extraction procedure was used to assess the environmental risk of Cd, Cr, Cu, Ni, Pb and Zn in contaminated sediment of the Dongting Lake. The procedure was evaluated by using a certified reference material, BCR701. The results of the partitioning study indicated that in the lake sediments, more easily mobilized forms (acid exchangeable) were predominant for Cd, particularly in the samples from the East Dongting Lake. In contrast, the largest amount of Pb was associated with the iron and manganese oxide fractions and Cu, Zn, Cr, and Ni analyzed were mainly distributed in residual phase at an average percentage greater than 60% of the total metals. The potential risk to the lake's water contamination was highest in the East Dongting Lake based on the calculated contamination factors. On the other hand, the total metal content was determined as well by inductively coupled plasma and mass spectrometry (ICP-MS) and assessed by using geo-accumulation index. The assessment results using geo-accumulation index were compared with the information on metal speciation. Both were correspondent with each other.
文摘Encroachment, disposal of untreated domestic and industrial wastewater and dumping of solid wastes have degraded the overall quality of the river Turag, which is located in Dhaka—the Capital City of Bangladesh. The present study investigated the extent of pollution of sediments of this river and analyzed the regional variability for the concentrations of Cr, Pb, Zn, Cu and Cd—all of concern because of their potential toxicity, using atomic absorption spectrophotometer. As per US EPA sediment quality guideline, metal concentrations ranged between Cd: 0.00 - 0.80, Cr: 32.00 - 75.50, Cu: 46.30 - 60.00, Pb: 28.30 - 36.40, and Zn: 94.60 - 190.10 mg/kg in the Turag river sediments. Cr, Cu, Zn belongs to moderately to highly polluted, Pb and Cd belongs to not polluted for Turag river. The heavy metals contamination in the sediments were also evaluated by applying Index of geo-accumulation (Igeo), contamination factor (Cf), pollution load index (PLI) etc. Toxicity characteristics leaching procedure (TCLP) test (US EPA 1311) for sediment samples have been performed also for metals (Pb, Cd, Cr, Cu and Zn) to determine the readily toxicity level of heavy metals. Sieve analysis of sediment performed in this study to determine the physical characteristic of sediment samples. The metal concentrations are well below the regulated level as per US EPA. This index can be complemented with the contamination index, which allows more site-specific and accurate information on contaminant levels. If the aim of work on contamination evaluation is to assess the overall contamination of a study area, the indices are highly appropriate.
文摘Sediment core samples were collected from the Salinas de San Pedro to assess the pollutant deposition processes in response to extensive human activities. Analysis of the sediment samples for heavy metals and some trace elements was conducted with ICP-OES for 20 sites showing enrichment for some of trace and heavy metals. The results demonstrated that heavy metal concentrations in mud varied greatly for each metal, with concentration values (mg/g) ranging from 1.05 - 4.8 (Al);0.003 - 0.011(As);0.001 - 0.005 (Cd);0.02 to 0.82 (Cr);0.085 - 0.47 (Cu);5.98 - 14.22 (Fe);0.06 - 0.19 (Mn);0.03 - 0.67 (Ni);0.05 - 0.38 (Pb);- 0.069 (Se);0.18 - 0.63 (Ti);0.040 - 0.091 (V) and 0.149 - 0.336 (Zn). The Index of Geo-accumulation factor showed highest values for Pb, Mn, As, and Cu. Enrichment factors >1for these elements suggest anthropogenic inputs for most metals. The bioavailability of metals in lagoon sediments has the potential to be highly dynamic with local waste and natural H2S discharge from existing fault line.
文摘Stream sediment samples were analyzed for the concentrations of some trace metals in the Obuasi gold mining environment, Ghana. The objectives were to determine the possible impacts of mining operations in the area on sediments’ trace metal load, and the resulting effects on agriculture and livelihoods. The concentrations of arsenic (As), copper (Cu), lead (Pb), zinc (Zn), iron (Fe), with calcium (Ca) as reference element, were compared to their respective background concentrations to calculate the enrichment and contamination factors, and also geo-accumulation and pollution load indices of each trace metal. These were in turn compared to standard tables to determine the status of contamination. Q-mode hierarchical cluster analysis (HCA) was then applied to the samples for spatial classification. This study suggests probable contribution of mining and associated activities in the Obuasi area to the concentrations of trace metals especially arsenic, in the stream sediments. Three spatial relationships were revealed based on the concentrations of these trace metals from the Q-mode HCA. The samples presented generally high concentrations, which were more profound for samples taken closer to holding pond and tailings dams, and decreased downstream.
文摘The heavy metal contamination status of Bight of Bonny sea bed sediment w<span>as investigated. Sediment samples were collected from eleven locations grouped into three stations. The samples were analyzed to determine the heavy met</span><span>als (Fe, Pb, Ni, Zn, Mn, Co, Cd, Cu, Cr) concentration using atomic absorption spectrophotometer. Index model analyses, such as geo-accumulation</span> index (I-geo), Enrichment factor (EF), and Pollution load index (PLI) were used for pollution assessment of sea bed sediment. The most predominant heavy metals in the upstream sediment were Fe;13.57 ± 1.838 mg/kg, cobalt;7.987 ± 3.550 mg/kg, and Ni;1.020 ± 0.802 mg/kg, midstream sediment were Fe;8.554 ± 3.010 mg/kg, Co;8.520 ± 4.00 mg/kg, and Ni;1.140 ± 0.879 mg/kg, while the downstream sediment result had Fe;11.12 ± 3.825 mg/kg, Co;7.275 ± 1.700 mg/kg, and Cd;1.025 ± 0.159 /kg. The I-geo results indicate that Cu, Mn, Pb, Cr, Fe, Zn, Ni, and Co were in their background concentrations while Cd had I-geo</span><span style="font-family:""> </span><span style="font-family:"">></span><span style="font-family:""> </span><span style="font-family:"">3 which implies a moderately or heavily polluted env<span>ironment. The EF indicates metal enrichment from anthropogenic sour</span>ces fo<span>r Co, Ni, Pb, Cd, Cu, and Cr while Fe and Mn predicate biogenic origin. The PLI of the heavy metals in the three sample stations of sea bed sediment was found to be generally low (<1). The Enrichment Factor and geo-ac</span>cumulation index strongly suggest the Bight of Bonny sea bed sediment contamination by Cd from anthropogenic sources.