Metal Potential Risk Research Articles

Residual, sequential extraction, and ecological risk assessment of some metals in ash from municipal solid waste incineration, Vietnam

Abstract Incineration plants for electricity generation have offered a solution to the challenges of domestic solid waste treatment in many countries. However, their emissions, fly ash (FA) and bottom ash (BA), have had a detrimental impact on environmental quality. This study investigated the morphology, element composition, and concentration of metals in FA and BA from municipal solid waste incineration plants using scanning electronic microscopy/energy-dispersive X-ray and inductively coupled plasma mass spectrometry techniques. It also evaluated the distribution ratios of metal species across five fractions: exchangeable, carbonate-bound, oxide-bound, organic-bound, and sulfide-bound, and residual. The total metal content in both FA and BA was comparable, with calcium having the highest concentration (28,170–135,130 mg·kg−1 dry weight) and silver having the lowest (5.26–19.3 mg·kg−1 dry weight). However, the percentage proportion of metals differed between the extracted fractions. Except for cadmium in FA, ecological risk assessment indicated low direct bioavailability and potential risk of metals in both FA and BA. These findings contribute to the hazard assessment of FA and BA generated from waste incinerators and provide a scientific basis for developing treatment techniques for this type of waste.

Regional geochemical baseline based pollution assessment and dominant factors influencing metals in riparian sediment of Yangtze River, China

In this study, we assessed pollution status and potential risk of metals in riparian sediment of Yangtze River with geo-accumulation index (Igeo), ecological risk index (RI) and health risk index (THQ) by calculated regional geochemical baseline (RGB) values. We explored the influence of natural factor (sediment property) and anthropogenic factors (land use composition and landscape configuration) at different buffers (500 m, 1 km and 5 km) on metals in sediment using redundancy analysis (RDA) and variation partitioning analysis (VPA). Results indicated that RGB values can effectively model background values of metals (p < 0.01). Igeo and RI assessment showed that Cd was the primary pollutant, which showed no contamination to moderate contamination (Igeo > 0) and moderate ecological risk (ecological risk factor > 40) in upper downstream of the river. Besides, Cd showed moderate to strong contamination (Igeo > 2) and considerable ecological risk (ecological risk factor > 160) at site 24, which is located in the intersection of Poyang Lake and Yangtze River and strongly affected by natural erosion and human activities of Poyang Lake drainage. THQ assessment indicated low health risk of metals from consuming fish influenced by suspended sediment. RDA and VPA analysis indicated that explanation rate of land use composition, sediment property and landscape configuration on metals was 27.01–55.1 %, 36.66 %, 9.77 %-12.52 %, respectively. The total explanation rate was significantly higher at 1 km scale (82.5 %), which was mainly contributed by land use composition and its interaction with sediment property and landscape configuration (55.11 %). Specifically, percentage of farmland, grassland, wetland and forest, content of TN, TOC, silt and clay in soil and landscape configuration index of NumP were positively correlated with metals, and content of sand in soil and landscape index of MSI negatively correlated with metals in riparian sediment at different buffer scales. Our results offer valuable insights for safeguarding riparian zone.

Chemical Speciation, Bioavailability and Human Health Risk Assessment of Metals in Surface Dust from an Industrial Cluster in India

In this study, distribution of metals in different geochemical forms, their mobility and bioavailability in bulk surface dust samples of Bhiwadi industrial cluster (BIC) in Rajasthan, India, was assessed by modified Community Bureau of Reference (m-BCR) sequential extraction procedure. Potential risk of metals in surface dust to environment and human health was evaluated using Contamination factor (Cf), Mobility Factor (MF) and Risk Assessment Code (RAC), and carcinogenic and non-carcinogenic health risk. Residual fraction contained significant amount of metals as Cd(55.86%), Cr(86.05%), Fe(90.06%), Mn(69.94%), Ni(66.08%), and V(71.80%). Pb(52.43%) was present in reducible fraction, while Cu was equally distributed in reducible (27.66%) and oxidizable (28.20%) fractions. Zn was equally distributed in acid exchangeable (33.15%) and reducible (35.01%) fractions. High Cf values were observed for Zn (1.32-16.98), followed by Pb (0.38-11.23) and Cu (0.26-8.22). RAC indicated high risk of Cd, Mn, Ni and Zn to environment due to their high mobility and toxic nature. Zn, Pb, Cu and Cd showed highest mobility (potential bioavailability) in samples collected around metal casting, electroplating, and automobile part industries. Data indicated that metals can bio-available with the changes in redox conditions in environment. Ingestion was major pathway for carcinogenic and non-carcinogenic health risks followed by dermal and inhalation. Hazardous Index value (6.32) indicated higher susceptibility of children for non-carcinogenic risk as compared to adults. Carcinogenic risk of Cr, Cd, Ni and Pb was higher than acceptable levels in surface dust, suggesting a high risk of cancer to exposed population.

Contamination Status and Potential Risk of Metals in Marine Sediments of Shalateen Coast, the Red Sea

ABSTRACT Metal contamination of the aquatic environment is a serious concern, insofar as public health and environmental protection are considered. Owing to their persistent and toxic characteristics, spatial analyses of metal concentrations in sediment with comparisons with natural backgrounds are essential. This study aimed to determine the metal concentrations of Cd, Cr, Co, Cu, Ni, Pb, and Zn and to appraise their probable ecological risk in sediments from the Shalateen coastal area. A total of 18 sediment samples were taken from different locations from the Shalateen coastal area. All sediment samples were kept in plastic bags at −20°C until analysis. The samples were digested using a wet oxidation method. The digested samples were determined for Cd, Cr, Co, Cu, Ni, Pb and Zn using Flame Atomic Absorption Spectrophotometry. Physicochemical characteristics (calcium carbonate content, grain size, organic matter, and pH) were conducted using standard procedures. Diverse procedures, guidelines, and indices have been employed and manipulated to assess risk. The results revealed that the mean value of metal contents in the study area followed the order Zn > Cr > Ni > Cu > Pb > Co > Cd. Most of the studied metals in the sediment did not exceed limits that are regarded harmful for aquatic life. Both pollution load and potential ecological risk index methods displayed that the integrated ecological risk of the investigated metals was quite low. A clear correlation linking the concentrations of metals and anthropogenic sources was not observed. This work designates that even with continuing development of the Shalateen coastal area, the metal contamination status remains relatively low.

Distribution and potential risk of metals and metalloids in soil of informal E-waste recycling sites in Lagos, Nigeria

Crude and haphazard informal e-waste recycling has resulted in environmental pollution with detrimental effects on human health. The present study assesses the levels of metals and metalloids (Pb, Mn, Fe, Zn, Co, Cd, Ni, Ag, Cu, As, Ba, Cr, Ca, Mg, K, and Na) in topsoil of informal e-waste recycling sites in Lagos, Nigeria. Topsoil samples (0-15 cm) were randomly collected at different informal e-waste recycling hubs in Lagos. Samples were digested and the levels of heavy metals and metalloids were determined using ICP-OES. Soil contamination indices, ecological and human health risks were evaluated using contamination factor, degree of contamination, geo-accumulation index, ecological risk index (RI), and human risk index (HI), respectively. There were variations in the concentrations of metals and metalloids in the soil, which ranged from 7.05-16,350 mg/kg Pb, 14.4-3,373 mg/kg Cu, ND-21.9 mg/kg Cd, and ND-166 mg/kg Ni. Lead had the highest mean concentration of 7394 ±7759 mg/kg in soil around the dismantling points at Ojota scrap market. Ojota scrap market also had the highest concentrations of all the metals except Co, Cd, As and Ba. Health risk index (HI) ranged from 3.93-183 in both children and adults populations. These calls for concern due to potential health risk associated with human exposure to toxic metals, some of which are also endocrine disruptors. There is need for proper management of e-waste in Nigeria to prevent human exposure to these toxic substances present therein.Keywords: Electronic waste, environmental contamination, heavy metals, recycling, health risk, waste management

Enhanced electrokinetic remediation of mixed contaminants from a high buffering soil by focusing on mobility risk

Electrokinetic (EK) experiments were conducted for investigating the mobility and risk assessment of inorganic (lead, zinc, and nickel) contaminants beside phenanthrene (PHE) in a natural soil with high buffering capacity; moreover, the optimum simultaneous treatment of the contaminants was considered with regard to the removal efficiency, energy consumption and risk assessment. Nonionic surfactants (Tween 80 and Brij 35) combined with disodium ethylene diamine tetraacetate salt (Na2-EDTA) were examined during 15-day electrokinetics. The operating conditions including pH-control, refreshing electrolyte and changing voltage gradient were tested to improve the soil remediation. A five-step sequential extraction was used to figure out the potential risk of metals in the treated soil. Lead had the highest removal of 79% among the other contaminants. The priority of heavy metals removal under the optimum conditions (Tween 80 + Na2EDTA) was lead > zinc > nickel. Electrolyte refreshment was favorable for remediation of selected heavy metals, while pH conditioning increased energy consumption and hindered the migration in the high buffering soil. Data analyses by Bioavailability Index (BI) and Mobility Factor (MF) confirm that the enhanced EK technology could increase the mobility risk of heavy metals, especially near the anode chamber; thus, the availability of the remained contaminants should be considered alongside the removal efficiency and energy consumption for evaluating EK strategies.