Risk Index Of Heavy Metals Research Articles

Analysis and probabilistic health risk assessment of vertical heavy metal pollution in the water environment of reservoir in the west coast new area of Qingdao, China

The West Coast New Area is a typical city in China where water supply is predominantly sourced from reservoirs. Heavy metal pollution in these reservoirs directly impacts the safety of drinking water and human health. Therefore, this study comprehensively evaluated the status of heavy metal pollution in the water environment and sediment of the main water supply reservoir in the study area, revealing the interaction relationship and pollution sources, as well as assessing the probabilistic health risks to human beings. The results show that there are different degrees of pollution in the main water supply reservoirs in the study area, and the pollution increases with the increase of water depth. The heavy metal pollution index was up to 2681, indicating heavily pollution. The main polluting elements were Mn and Fe, and the maximum contents were 4.11 mg L−1 and 0.68 mg L−1, respectively, which far exceeded the Class III standard limit of drinking water in China. The main source of pollution is human activities, and Mn release from sediment aggravates deep water pollution. The non-carcinogenic risk index of heavy metals in the reservoir, ranging from 4% to 14%, is higher than 1, indicating a potential non-carcinogenic threat. Furthermore, heavy metals have a much greater impact on children compared to adults, among which Mn is the main contributor to human non-carcinogenic risk, contributing more than 60%. Therefore, controlling the content of Mn and Fe can effectively reduce the heavy metal pollution of reservoir and human health risk. The research results are of great significance for the utilization of reservoir water resources and the protection of the ecological environment in the study area.

Characteristics, source analysis, and health risk of PM2.5 in the urban tunnel environment associated with E10 petrol usage.

The increase in the number of motor vehicles has intensified the impact of traffic sources on air quality. Our aim was to illustrate the characteristics of PM2.5 emissions from vehicles fueled with E10 (a blend of 10% ethanol and 90% gasoline). A 21-day PM2.5 sampling in a fully enclosed urban tunnel and the component analysis were completed, and the characteristics, sources, and health risks of tunnel PM2.5 were studied. Moreover, the PM2.5 pH and its sensitivity were investigated by the thermodynamic model (ISORROPIA-II). In addition, exposure models were used to assess the health risks of different heavy metals in PM2.5 to humans through respiratory pathways. The two-point Cu/Sb ratio (entrance: 4.0 ± 1.4; exit: 4.4 ± 1.7) was close to the diagnostic criteria indicating a significant impact from brake wear. NO3-, NH4+, and SO42- constituted the main components of water-soluble ions in PM2.5 of the tunnel, accounting for 83.0-84.6% of the total concentration of inorganic ions. The organic carbon/elemental carbon ratio of the tunnel was greater than 2, indicating that the contribution of gasoline vehicle exhaust was significant. The average emission factors of PM2.5 in the fleet was 31.4 ± 16.6 mg/(veh·km). The pH value of PM2.5 in a tunnel environment (4.6 ± 0.3) was more acidic than that in an urban environment (4.9 ± 0.6). The main sensitive factors of PM2.5 pH in the urban atmosphere and tunnel environment were total ammonia (sum of gas and aerosol, NH3) and temperature, respectively. The results of the health risk assessment showed that Pb posed a potential carcinogenic risk, while As and Cd presented unacceptable risks for tunnel workers. The non-carcinogenic risk index of heavy metals of PM2.5 in the tunnel environment exceeded the safety threshold.

Health Risk Assessment of Heavy Metals in the Medicinal Plants Ziziphora clinopodioides and Echinophora platyloba in West Islamabad and Sanandaj Regions

Background & Aims: Medicinal plants are part of traditional medicine, which has many uses in the treatment of diseases and human health. This research was conducted to evaluate heavy metals in two species of Ziziphora clinopodioides and Echinophora platyloba. Materials and Methods: In each of the cities of Islamabad and Sanandaj, five sampling stations were determined, and from each station, 5 samples of Kakuti plant and 5 samples of Khosharizeh plant were collected from 3 different places of non-agricultural lands in the summer season of 2021. The mean data of heavy metals were compared with each other using a one-way analysis of variance and Duncan’s test. Results: The average of manganese (Mn) in Z. clinopodioides and E. platyloba (5112.95 and 4258.67 mg/kg) was significantly higher than other heavy metals (P<0.05). In addition, the average of arsenic in Z. clinopodioides and E. platyloba (0.002 mg/ kg and 0.001 mg/kg) had significantly the lowest values among the studied heavy metals (P<0.05). The results of the health risk assessment showed that the highest risk index of heavy metals in Z. clinopodioides and E. platyloba in the age group of children was related to Mn (12.15 and 12.74, respectively). On the other hand, the lowest value of the risk index of heavy metals for the consumption of Z. clinopodioides and E. platyloba for children and adults was obtained for iron (0.48 and 0.32, respectively). The highest carcinogenic risk index of the Kakuti plant was observed in two age groups of children and adults regarding cadmium (0.099 and 0.098, respectively). Conclusion: The analysis of the health risk assessment of heavy metals in the samples of Z. clinopodioides and E. platyloba in two regions of Islamabad and Sanandaj revealed that the consumption of these two plants is dangerous for the health of people of different age groups.

Temporal-spatial characteristics and sources of heavy metals in bulk deposition across China

With the rapid development of industries, agriculture, and urbanization (including transportation and population growth), there has been a significant alteration in the emission and atmospheric deposition of heavy metal pollutants. This has consequently given rise to a range of ecological and environmental health issues. In this study, we conducted a comprehensive two-year investigation on the temporal and spatial distribution characteristics of heavy metals in atmospheric deposition across China based on the Nationwide Nitrogen Deposition Monitoring Network (NNDMN). The atmospheric bulk deposition of Lead (Pb), Arsenic (As), Nickel (Ni), Selenium (Se), Chromium (Cr) and Cadmium (Cd) were 6.32 ± 1.59, 4.49 ± 0.57, 1.31 ± 0.21, 1.05 ± 0.16, 0.60 ± 0.06 and 0.21 ± 0.03 mg m−2 yr−1, respectively, with a large variation among the different regions of China. The order for atmospheric deposition flux was Southwest China > Southeast China > North China > Northeast China > Qinghai-Tibet Plateau and rural area > urban area > background area. The concentrations of heavy metals in bulk deposition exhibit seasonal variation with higher levels observed during winter compared to summer and spring, which are closely associated with anthropogenic activities. The Positive Matrix Factorization (PMF) results indicated that combustion, industrial emissions and traffic are the primary contributors to atmospheric deposition of heavy metals. The single factor pollution index (Pi) of heavy metals is consistently below 1, and the composite pollution index (Ni) is 0.16 across China, indicating that atmospheric heavy metal deposition is at a pollution-free level. The comprehensive potential ecological risk index of heavy metals is 11.8, with Cd exhibiting the highest single factor potential ecological risk index at 7.09, suggesting that more attention should be paid to Cd deposition in China. The present study reveals the spatial-temporal distribution pattern of atmospheric heavy metals deposition in China, identifying regional source characteristics and providing a theoretical foundation and strategies for reducing emissions of atmospheric pollutants.

Vertical and Lateral Variation of Ecological Risk Index of Heavy Metals in the Euphrates River Sediments between Heet and Fallujah, Iraq.

The heavy metals (HMs) contamination of river sediments and their ecological risks is a global environmental problem that has attracted the attention of researchers and those interested in environmental protection. The study aims to investigate the ecological hazards of some HMs in sediments of Euphrates River between the cities of Heet and Fallujah, Iraq and their lateral and vertical variations. At three depths—0-30, 30-60, and 60-90 cm—samples of sediment were collected from five sites. Atomic Absorption Flame Emission Spectrophotometer (ASC.7000) was used to measure concentration of Cd, Cr, Cu, Ni, Pb, and Zn. The ecological risk index (ErI) values of metals in Euphrates River sediment in the study area take the following descending order: Cd > Ni > Cu > Cr > Pb > Zn. The ErI levels were low for Cr, Cu, Ni, Pb and Zn and considerable ecological risk for Cd. The obtained results did not show a common lateral variation pattern of the ecological risk of the measured metals. There is a high level of risk for the measured metals at the downstream sampling sites except for the risk from Cd on the contrary. The potential ecological risk of Cd, Cr, Pb and Zn showed a similar vertical variation pattern which in turn reflects a common source or origin for these metals, while copper and nickel showed a different common distribution pattern.

Heavy metals pollution and potential ecological health risk assessment in the Yangtze River reaches

Since the construction of the Three Gorges Project, great changes have taken place in the hydrological situation along the Yangtze River and its tributaries. This paper analyzes the content level, temporal and spatial changes and potential ecological risk trends of heavy metal pollutants in surface sediments from 2015 to 2020. The results showed that the average contents of copper (Cu), lead (Pb), manganese (Mn), arsenic (As) and mercury (Hg) in the sediments along the Yangtze River were 23.2∼50.3 mg/kg, 19.6∼65.7 mg/kg, 154.3∼996.8 mg/kg, 6.98∼20.65 mg/kg, 0.198∼0.492 mg/kg, respectively. The average content of Cu, Pb, Mn, As and Hg in sediments of it’s tributaries was 22.3∼29.5 mg/kg, 15.3∼36.7 mg/kg, 456.3∼1123.4 mg/kg, 7.37∼17.15 mg/kg, 0.209∼0.345 mg/kg, respectively. There were obvious differences in the content of heavy metals in the surface sediments of the left and right banks of local river sections along the Yangtze River. The content of heavy metals in surface sediments along the Yangtze River and its tributaries fluctuated to a certain extent in different water periods. The contents of Cd, Cr, Cu, Pb, As and Hg in the back muscle tissue of seven main economic fishes were determined. The results showed that the contents of Cd, Cr, Cu, Pb, As and Hg were 0.02∼2.53 mg/kg, ND∼2.75 mg/kg, 0.0003∼4.1 mg/kg, ND∼1.03 mg/kg, ND∼0.03 mg/kg, ND∼0.03 mg/kg, respectively. Pb and Cd were the main elements of heavy metal pollution in Yangtze River fish. Crucian fish was the most polluted by heavy metals, while grass fish was the least. Various evaluations show that the heavy metals in the surface sediments along the Yangtze River and its main tributaries were generally at a medium enrichment level, and the potential ecological risk index of heavy metals except Ganjiang River changes little during most periods. The potential ecological risk index of heavy metals in Ganjiang River was at relatively high level in 2017, but declined and tended to be stable after 2017.

Spatial analysis and risk assessment of heavy metal pollution in rice in Fujian Province, China

To comprehensively understand the spatial characteristics and pollution hazards of heavy metals in rice in Fujian Province, the contents of Cd, Hg, As, Pb, Cr, Ni, Cu, and Zn in 260 rice samples were measured based on the field investigation. Their spatial distribution patterns and clustering characteristics were explored by geostatistical methods, and their pollution-health risks were revealed by the pollution index method and exposure evaluation model. The results showed that the average contents of eight heavy metals in rice were below the food safety limits, but the excess rates of As, Cu, and Cd samples reached 33.08%, 22.69%, and 18.85%, respectively. In terms of spatial characteristics, the contents of Cd, Hg, and Ni were higher in the southeastern and northwestern regions, while the contents of As, Cu, and Cr were higher in the southwestern parts of Fujian Province. The hotspots of the corresponding heavy metals were also concentrated in the above-mentioned areas, showing an obvious spatial clustering effect. The pollution risk assessment showed that the single factor pollution index of heavy metals in rice decreased in the order of As (0.536) > Hg (0.505) > Cu (0.421) > Cd (0.378) > Cr (0.318) > Zn (0.304) > Pb (0.286) > Ni (0.116), and the Nemerow comprehensive pollution index was 0.623, which was generally at a safe level with low pollution risk. Furthermore, the non-carcinogenic risk index of heavy metals for adults and children were 3.558 and 6.014, and the carcinogenic risk index were 0.0050 and 0.0084, respectively, with extremely serious health hazards. In contrast, the health damage of heavy metals was higher in children than that in adults, with As and Cd in rice as the pivotal elements. Therefore, attention should be paid to the future monitoring and agricultural management of heavy metal pollution in rice in the region.

Influence of Different Types of Dewatering Agents on the Solidification Effect and Physical and Chemical Properties of Sediment

In order to study the comprehensive effects of different types of dehydrating agents on the dewatering and solidification of dredged sediments, this study took the dredged sediments of Taihu Lake as the research object and selected microorganisms, polymeric iron aluminum salts, organic polymers, organic-inorganic composites, and aluminum salt microorganisms. These five types of composite dehydrating agents were used to conduct a three-month solidification test on the dredged sediment by means of geotechnical pipe bag solidification. The results of the study showed that the dehydration efficiency of organic polymers and organic-inorganic composite chemicals was better. After one month, the water content of sediment dropped to 61.78% and 63.26%, respectively, which then dropped to 40.56% and 32.16% after three months. Compared with that of the unsolidified sludge, the total nitrogen of the bottom sludge after solidification by the organic-inorganic composite agent was reduced by 74.82%, reaching 591 mg·kg-1, primarily due to the reduction in ammonia nitrogen. The solid sludge contained mainly aluminum-bound phosphorus, calcium-bound phosphorus, and iron-bound phosphorus. Among them, four groups (organic-inorganic composite) had the largest reduction in active phosphorus, with the lowest being 64.3 mg·kg-1. In addition, organic polymer agents had the best curing effect on heavy metals, the comprehensive ecological risk index of heavy metals was reduced by 51.3%, and the leaching toxicity concentration was far below the standard threshold. This study showed that organic polymers and organic-inorganic composite medicaments have a better effect on the dehydration and solidification of bottom sludge and thus have good application prospects.

Spatial Characteristics and Potential Ecological Risk Factors of Heavy Metals in Cultivated Land in the Transition Zone of a Mountain Plain

The purpose of this study was to explore the spatial distribution characteristics and potential ecological risk factors of heavy metal pollution in cultivated soil in the transitional zone of a typical mountain plain. In this study, a county in Sichuan Province, which has the typical transitional topography of the Chengdu Plain-Longmen Mountain transition zone, was taken as the study area. Geostatistics and potential ecological risk index methods were used to analyze the spatial distribution of Cd, Cr, Cu, Pb, and Zn from cultivated land in the study area, and a potential ecological risk assessment was carried out. This was combined with geographical detector analysis to further explore the main influencing factors leading to the spatial difference in potential ecological risk. The results showed that:① The average values of ω(Cd), ω(Cr), ω(Cu), ω(Pb), and ω(Zn) of cultivated land in the study area were 0.39, 123.00, 31.28, 51.04, and 119.66 mg·kg-1, respectively, which were more than 2.60, 1.59, 1.19, 2.00, and 1.54 times the soil background value in the study area. ② The high value areas of Cd and Cr in cultivated land in the study area were mainly distributed in the west of the mountain area, the south of the transition zone, and the west of the plain area; the high value areas of Cu and Zn were mainly distributed in the west of the mountain area; the high value areas of Pb were mainly distributed in the south of the transition zone and the west of the plain area; and the low values of the five heavy metals were mainly distributed in the north of the transition zone. ③ The soil of cultivated land in the study area was dominated by slight potential ecological risk, and the average value of potential ecological risk index of heavy metals was Cd(32.58) > Pb(3.12) > Cu(2.82) > Cr(1.58) > Zn(0.98). Cd was the main factor causing the potential ecological risk of cultivated land in the study area. ④ There were significant differences in the key influencing factors of soil potential ecological risk of cultivated land in different topographic regions of the study area. The distance from the river and the soil type were the key factors affecting the mountain area; the multiple cropping index and the distance from the industry and mine were the key factors affecting the transition zone, and the soil pH value and the amount of chemical fertilizer were the key factors affecting the plain area.

Evaluation of Health Risk Index of Heavy Metals of Lead, Nickel, Zinc, Iron and Copper in Liza Klunzingeri Muscle in Hormozgan Province

This study was performed to measure the amounts of heavy metals lead, nickel, zinc, iron and copper in garish fish of islands (Qeshm, Hengam and Hormoz) in Hormozgan province. A total of 180 samples were collected in the study areas during the two seasons of summer and winter in 1398. After bioassay, the concentration of elements in muscle tissue was measured using an atomic absorption spectrometer.The results showed that the highest mean concentrations of metals lead, nickel, zinc and copper in Qeshm (lead: 0.082 ± 0.009, nickel: 0.646 ± 0.07, zinc: 31.97 ± 1.33 and copper : 0.881 ± 0.03 μg / g) and iron metal in Hormoz (iron: 19.30 ± 0.75 μg / kg) and the lowest average concentration of metals in Hengam (lead: 0.036 ± 0.007 Nickel: 0.348 ± 0.05, Zinc: 15.13 ± 1.06, Copper: 0.657 ± 0.03 and Iron: 12.13 ± 0.4 μg / gram. The results also showed that there is a direct relationship between metal concentration and length and total body weight of fish. On the other hand, the concentrations of lead, nickel, zinc and copper in barley fish samples in the study areas were lower than the international standards of FAO, WHO, FDA, NHMRC and UKMAFF. Also, the level of potential risk and risk index for non-cancerous diseases in adults and children in the aquifer muscle tissue was less than 1. Therefore, it can be concluded that there are currently no problems for human health in terms of consumption of this fish.

Chemical quality assessment and health risk of heavy metals in groundwater sources around Saravan landfill, the northernmost province of Iran

ABSTRACT The penetration of landfill leachate into the subsoil contaminates soil and groundwater and has a negative effect on health. Therefore, the present study was conducted to investigate the quality and health risk of groundwater around Saravan landfill in Guilan province. To determine the effects of landfill on groundwater, leachate and water sampling of 5 wells around Landfill were performed according to standard procedures. The sampling was repeated 2 times and the samples were run through 0.45 Wattman filters to measure heavy metals. Then physico-chemical parameters were analysed and the results were compared with WHO standard and Environmental Protection Organization of Iran. Finally, the water quality index and potential health risks in children and adults were calculated. The results showed that the high pH of the leachate indicates the long life of the landfill. The concentrations of chromium, lead and manganese were higher than the allowed amount. The results of non-carcinogenic cumulative risk assessment in children and adults were 4.77 and 2.48 and the result of carcinogenic cumulative risk assessment in children and adults were 11 × 10 −3 and 23 × 10 −3, respectively Also, the health risk index of heavy metals for lead and manganese in gastrointestinal and cutaneous exposure in children was more than 1, respectively. Water quality index of 68.935 was obtained which was lower than recommended. According to the findings, the waste burial in Saravan landfill has led to a decrease in the quality of adjacent groundwater. The results of heavy metal concentrations and their health risk assessment showed the potential for pathogenic risk to the health of groundwater consumers in the study area. Therefore, due to the proximity of water wells to Saravan landfills and possible changes in the concentration of heavy metals, continuous monitoring is necessary.

Spatio-temporal Distribution Characteristic and Risk Assessment of Heavy Metals in Soils Around Centralized Drinking Water Sources in Wuhan

In the present study, the spatio-temporal distribution characteristics of heavy metals (Cd, Hg, As, Pb, Cr, Cu, Ni, and Zn) in soil around 19 centralized drinking water sources in Wuhan were investigated. Single-factor and comprehensive pollution indexes were used to determine soil pollution levels. The potential ecological hazard index was employed to evaluate soil potential ecological risks. The correlation and cluster analysis were conducted to identify pollution sources. The results showed that higher concentrations of heavy metals were present in soil from centralized drinking water source located in core area than suburb area of Wuhan. The concentrations of heavy metals in soil from centralized drinking water sources near the Yangtze River were higher than that in the sites near the tributaries of the Yangtze River. The average single potential ecological risk index of Hg, As, Pb, Cr, Cu, Ni, and Zn were lower than 40, which suggests a slight potential ecological risk. The average single potential ecological risk index of Cd was 80-160, which indicates a high potential ecological risk. The average comprehensive potential ecological risk index of heavy metals in soil around centralized drinking water sources in Wuhan was 142.12, which corresponded to a slight potential ecological risk. The correlation analysis showed that the sources of Cu, Pb, and Cr were similar and came from transport. The sources of Ni, As, Cr, and Cu were similar and could be attributed to metallurgical industries. The sources of Zn, Hg, and Cr were similar and could be related to antiseptic and catalytic industries. The long-term monitoring of Wuhan Dijiao and Baishazhou waterworks indicated that the concentrations of heavy metals around centralized drinking water sources in Wuhan were markedly decreased after 2017 and that ecological risk may be further reduced in the future.

Ecological Risk Assessment of Heavy Metals in Sediments of Duyen Hai Seaport Area in Tra Vinh Province, Vietnam

The Duyen Hai Seaport covering more than 427 hectares of water surface is part of a Duyen Hai thermal power plant complex. In the last years, port operations can lead to impact on air, water, land, and the ecosystem. To evaluate the ecological risk caused by heavy metals at the Duyen Hai Seaport, 17 surficial sediment samples were collected along the ship flow from shoreline to the material submerged zone in April 2019. The total concentrations of some heavy metals including lead, cadmium, arsenic, copper, zinc, and mercury were analyzed by using atomic absorption spectrophotometry. The experimental results indicated that there were significant and positive correlations between various heavy metals studied. The geo-accumulation index (Igeo), the potential ecological risk index (RI), and the degree of contamination (Cd) were calculated for evaluating the risks of heavy metal in sediment samples. The Igeo values showed that the Duyen Hai Seaport is slightly contaminated by heavy metals, especially by Cd. Generally, the low potential risk of heavy metal was observed from the values of RI. The potential ecological risk index of heavy metals was found in the order ER (Hg)>ER (Cd)>ER (As)>ER (Pb)>ER (Zn)>ER (Cu), which revealed that Cd was the most important factor leading to the risk. These findings might be useful for making appropriate management strategies to prevent or decrease pollution by heavy metal at the Duyen Hai Seaport.

Assessment of Pollution and Ecological Risk Index of Heavy Metals in the Surface Sediment of Estuary and the Coastal Environment of Bay of Bengal

The Mahanadi River, surrounding estuaries along the coastal water are important to understand the relationship between heavy metals, ecosystem and human health, as the region being used largely by fisher communities for the potential fishing ground and agriculture. The study evaluates the ecological risk index of heavy metals in the surface sediments along the coastal environment of the Bay of Bengal between 2011 and 2012. The metals concentrations were varied from a maximum in Manganese (4,137 mg/kg) to a minimum in Cadmium (17 mg/kg). The factor analysis result shows that higher concentration of cadmium (Cd), chromium (Cr), Nickel (Ni), lead (Pb), and Zinc (Zn) were significant environmental risk in the study region. The cluster analysis indicated that the creek sediment is heavily polluted than the estuary ecosystem of the coastal environment. Enrichment factor and Geo-accumulation Index of the surface sediment resulted that, the Cd was high enrichment and was moderate to severe in the study region. Pollution load index denoted that the sampling sites in the creek sediment were more polluted than coastal due to the influence of agricultural runoff, industrial and anthropogenic. The Cr, Cu, Ni, Pb, and Cd concentrations result in the potential toxicity to the aquatic organisms based on the comparison with the SQGs. Indicates the average magnitude of the metals in the study period in the decreasing order of Mn, Cr, Cu, Ni, Pb, and Cd which were alarming except iron (Fe) in the estuary and coastal ecosystem of the Bay of Bengal. The present investigation would be a first-hand informant to understand the impact of heavy metals in the ecosystem in the region. The result inputs need to be monitored further in the long term basis for isotopic sediment dating to reconstruct the contamination history for the ecosystem modeling, sustainable ecosystem, and coastal zone management.

Effects of Cascading Hydropower Dam Operation on Benthic Macroinvertebrate Assemblages and Sediments in the Lancang River

Li, J.P.; Cheng, D.M.; Zhao, A.D.; Liu, S., and Xuan, H., 2020. Effects of cascading hydropower dam operation on benthic macroinvertebrate assemblages and sediments in the Lancang River. In: Guido Aldana, P.A. and Kantamaneni, K. (eds.), Advances in Water Resources, Coastal Management, and Marine Science Technology. Journal of Coastal Research, Special Issue No. 104, pp. 465–472. Coconut Creek (Florida), ISSN 0749-0208.The operation of cascading hydropower dams may have complex and long-term effects on river ecosystems, where benthic macroinvertebrate assemblages and sediments are indicators of changes in dynamics. This study investigated how cascading hydropower dams in the middle and lower reaches of the Lancang River in China affect benthic macroinvertebrate assemblages and sediments. Benthic macroinvertebrate assemblages and sediments were sampled in the Manwan and Dachaoshan cascading dams in 2016. The structure and distribution pattern of benthic macroinvertebrate assemblages, and heavy metal and nutrient pollution in sediments were analyzed. The benthic macroinvertebrate assemblages were mainly composed of species from Oligochaeta, Mollusca, and Insecta. Corbicula fluminea (Mollusca) was the most dominant species. The potential ecological risk index of heavy metals was higher in the upstream of the Manwan dam (M1-M3), while nutrient pollution in sediments was higher in the downstream of the Dachaoshan dam (D1-D3). The correlation analysis revealed that the density of Mollusca was significantly correlated with heavy metal pollution in sediments, while the density of Oligochaeta was significantly correlated with nutrient pollution in sediments. Hence, the operation of cascading hydropower dams has significant accumulation effects on benthic macroinvertebrate assemblages, and heavy metal and nutrient pollution in sediments, in river ecosystems.

Preparation and characterization of glass-ceramics from oil shale ash: Effect of basicity and sintering temperature on crystallization behavior, properties, and environmental risk

Oil shale ash is an inorganic by-product generated from the combustion and refinement of oil shale. In this study, it was used as main raw material to produce glass-ceramics. The crystalline phases, crystallization mechanism, bulk density, compressive strength and microstructure of glass-ceramics were studied. Specifically, the leaching characteristics and ecological risk assessment of heavy metals in glass-ceramics were emphasized. The results showed that the increase of basicity reduced the crystallization activation energy, but the surface crystallization mechanism of different samples has not changed. Anorthite and diopside were identified as the main crystalline phases in glass-ceramics despite varying basicity and sintering temperatures. The compressive strength and bulk density increased with the increase of sintering temperature. The compressive strength of VS2 (basicity = 0.3) was higher than that of VS1 (basicity = 0.2) for the same sintering temperature due to more crystals and denser microstructure. Independent of the basicity, a higher sintering temperature promoted the sintering and densification of products. The highest compressive strengths of VS1 and VS2 were 219.14 ± 12.8 and 255.57 ± 15.6 MPa, respectively. In addition, the reliable stability and low potential ecological risk index of heavy metals in the final products make it to be a competitive eco-friendly construction material.

Evaluation of Contamination and Ecological Risk of Heavy Metals Associated with Cement Production in Ewekoro, Southwest Nigeria.

Background.Exposure to heavy metals emanating from cement production and other anthropogenic activities can pose ecological risks.Objectives.A detailed investigation was carried out to assess the contamination and ecological risk of heavy metals associated with dust released during cement production.Methods.Sixty samples, including 30 soils and 30 plants, were collected around Lafarge Cement Production Company. Control samples of soil and plants were collected in areas where human activities are limited. Samples were dried, sieved (for soil; 65 μm), packaged and analyzed using inductively coupled plasma mass spectrometry at Acme Laboratory in Canada.Results.The average concentration of heavy metals in soils of the area are: copper (Cu): 41.63 mg/kg; lead (Pb): 35.43 mg/kg; zinc (Zn): 213.64 mg/kg; chromium (Cr): 35.60 mg/kg; cobalt (Co): 3.84 mg/kg and nickel (Ni): 5.13 mg/kg. Concentrations of Cr in soils were above the recommended standards, while other metals were below recommended limits. The average concentrations of heavy metals in plants were: Cu: 26.32 mg/kg; Pb: 15.46 mg/kg; Zn: 213.94 mg/kg; Cr: 30.62 mg/kg; Co: 0.45 mg/kg and Ni: 3.77 mg/kg. Levels of heavy metals in plants were all above international limits. Geo-accumulation of metals in soils ranged between −0.15 and 6.32, while the contamination factor ranged between 0.53 and 119.59. Ecological risk index of heavy metals in soils ranged between 49.71 and 749.Discussion.All metals in soils of the study area except for Cr were below the allowable limits, while the levels of metals in plants were above the permissible limits. Levels of heavy metals reported in this study were higher than those from similar cement production areas. Soils around the Ewekoro cement production area were low to extremely contaminated by toxic metals. Cement production, processing, transportation in conjunction with the abandoned railway track in the area greatly contribute to the high degree of contamination observed in the area. Metal transfers from soil to plant are a common phenomenon. The metals pose low to considerable ecological risk.Conclusions.Anthropogenic sources, especially cement processing activities, release heavy metals which leads to progressive pollution of the environment and poses high ecological risk.Competing Interests.The authors declare no competing financial interests

Assessment of heavy metal pollution in marine sediments receiving produced water, Delta State, Nigeria

Every aspect of oil and gas operations poses significant negative impacts on the environment in varying levels, these environmental impacts have economic and public health consequences on the indigenes of the operation locality. Produced water discharge is one of such aspects of the upstream oil and gas operation whose potential for environmental degradation has necessitated both local and international regulations for its governance. This research focuses on the environmental assessment of heavy metal pollution on marine sediments receiving treated produced water in Delta state, Nigeria. Sediment samples were obtained from produced water discharge area at various distances from the disposal point. Heavy metals (Cadmium, Zinc, Iron, Lead, Chromium, Vanadium, Barium, Nickel and Manganese) concentrations in the sediment were analyzed using Atomic Absorption Spectrophotometry method. In the sediment, manganese, nickel, chromium, lead, cadmium and zinc were detected in all the locations and showed no significant difference across the various locations. Barium and vanadium were detected in some location although no statistical difference was established across the locations. Iron concentration showed significant difference across the various locations. The results of heavy metals contamination factor in marine sediments ranged from low contamination to very high contamination (CF<1; 3 ≤ CF ≥ 6). High contamination values were recorded for vanadium (Location SD16, 21 and 22) and barium locations (SD8 and 21). The enrichment factor of heavy metals ranged from minimal to moderate, significant and very high enrichment. Barium, Nickel and Manganese showed the highest variation in enrichment factor. Other than cadmium and barium that showed moderate risk (40 ≤ Er <80) and very high risk (Er ≥ 320) at some locations respectively, the Ecological Risk Index of heavy metals based on the criteria for risk assessment showed low risk (Er<40) for most of the locations. Key words: Assessment, environmental impact, produced water, pollution, heavy metal, contamination, sediments.

Distribution and transformation behaviors of heavy metals during liquefaction process of sewage sludge in ethanol-water mixed solvents

Liquefaction of sewage sludge (SS) in ethanol-water cosolvents is a promising process for the preparation of bio-oil/biochar products. Effect of the combined use of ethanol and water on the distribution/transformation behaviors of heavy metals (HMs) contained in raw SS is a key issue on the safety and cleanness of above liquefaction process, which is explored in this study. The results show that pure ethanol facilitates the migration of HMs into biochar products. Pure water yields lower percentages of HMs in mobile/bioavailable speciation. Compared with sole solvent treatment, ethanol-water cosolvent causes a random/average effect on the distribution/transformation behaviors of HMs. After liquefaction of SS in pure water, the contamination degree of HMs is mitigated from high level (25.8 (contamination factor)) in raw SS to considerable grade (13.4) in biochar and the ecological risk is mitigated from moderate risk (164.5 (risk index)) to low risk (78.8). Liquefaction of SS in pure ethanol makes no difference to the pollution characteristics of HMs. The combined use of ethanol and water presents similar immobilization effects on HMs to pure water treatment. The contamination factor and risk index of HMs in biochars obtained in ethanol-water cosolvent treatment are 13.1−14.6 (considerable grade) and 79.3−101.0 (low risk), respectively. In order to further control the pollution of HMs, it is preferentially suggested to improve the liquefaction process of SS in ethanol-water mixed solvents by introducing conventional lignocellulosic/algal biomass, also known as co-liquefaction treatment.

Analysis and Evaluation of Heavy Metal Content in Remixing Soil by Feldspathic Sandstone and Sand in Mu Us Sandy Land, China

In order to ensure the quality of cultivated land with the technology of remixing soil by feldspathic sandstone and sand, the concentrations of eight heavy metals were measured, and the degree of heavy metal pollution in the soil was assessed by Nemerow index and potential ecological risk index. The results showed that, compared with feldspathic, the concentrations of Cr, Ni, Cu, Zn, As, Cd and Pb in the remixing soil decreased by 12.8%, 40.7%, 44.1%, 49.3%, 49.8%, 37.6% and 14.1% respectively. The concentrations of eight heavy metals in sandstone and remixing soil were not significantly different in space, but in sand vary greatly. There was very significant positive correlation among the contents of Ni, Cu, Zn, As, Cd and Pb in the remixing soil, which indicates that the heavy metals have obvious homology. The single pollution index of heavy metals in remixing soil, feldspathic sandstone and sand were all less than one, and the comprehensive pollution index were 0.611, 0.980 and 0.395 respectively. The potential ecological risk index (RI) of heavy metals in remixing soil, feldspathic sandstone and sand were all less than 150, indicating that the soils with three textures showed low ecological risks. After three years of planting, the potential ecological risk index of heavy metals in the remixing soil increased slightly, but the single pollution index was also less than one. The research shows that the remixing soil in Mu Us Sandy Land can ensure the quality of soil environment and the safety of agricultural products.