Total Heavy Metal Research Articles

Phytoremediation of pollutants in oil-contaminated soils by Alhagi camelorum: evaluation and modeling

Phytoremediation is a cost-effective and environmentally friendly method, offering a suitable alternative to chemical and physical approaches for the removal of pollutants from soil. This research explored the phytoremediation potential of Alhagi camelorum, a plant species, for total petroleum hydrocarbons (TPHs) and heavy metals (HMs), specifically lead (Pb), chromium (Cr), nickel (Ni), and cadmium (Cd), in oil-contaminated soil. A field-scale study spanning six months was conducted, involving the cultivation of A. camelorum seeds in a nursery and subsequent transplantation of seedlings onto prepared soil plots. Control plots, devoid of any plants, were also incorporated for comparison. Soil samples were analyzed throughout the study period using inductively coupled plasma-optical emission spectroscopy (ICP‒OES) for HMs and gas chromatography‒mass spectrometry (GC‒MS) for TPHs. The results showed that after six months, the average removal percentage was 53.6 ± 2.8% for TPHs and varying percentages observed for the HMs (Pb: 50 ± 2.1%, Cr: 47.6 ± 2.5%, Ni: 48.1 ± 1.6%, and Cd: 45.4 ± 3.5%). The upward trajectory in the population of heterotrophic bacteria and the level of microbial respiration, in contrast to the control plots, suggests that the presence of the plant plays a significant role in promoting soil microbial growth (P < 0.05). Moreover, kinetic rate models were examined to assess the rate of pollutant removal. The coefficient of determination consistently aligned with the first-order kinetic rate model for all the mentioned pollutants (R2 > 0.8). These results collectively suggest that phytoremediation employing A. camelorum can effectively reduce pollutants in oil-contaminated soils.

Pore structure characteristics and leaching mechanism of Cu and Cr in sustainable porous ceramisite produced from contaminated soil and biomass waste

Contaminated soil (CS) and biomass waste are potential resources. Their secure, scale, resource, and high-value utilization will bring significant socio-economic benefits. In present work, the basic properties, crystalline phases, microstructure and leaching behavior of porous ceramisite (PC) via CS and biomass waste were investigated systematically. The link of pore structure characteristics with leaching behavior of Cu and Cr was revealed. The environmental and economic benefits were also assessed. The results showed that the addition of 5∼15% pore-forming agent (carbon powder or biomass waste) made the matrix looser and the leaching amounts of heavy metals increased. However, the heavy metals leaching amounts was still lower than the critical limits of nonhazardous materials with immobilization rates higher than 97.5%. The leaching mechanism of Cu in the PC was controlled by initial wash-off, diffusion and depletion. The time period of the depletion dominated leaching is prolonged with increasing porosity. The leaching mechanism of Cr in the PC was mainly initial wash-off and depletion. The wash-off dominated the total heavy metal leaching amount, accounted for more than 80% of the total leaching amount. The leaching of Cu and Cr showed a positive correlation with (effective) pore volume of pores large than 1 μm, while demonstrating a negative correlation with the fractal dimension. The economic benefits of PC throughout the production process were analyzed, which showed that the production of PC using CS and biomass waste could eliminate raw material costs and could be subsidized by the government. This study provides an idea for the 100% utilization of CS and biomass waste as well as theoretical support for the disposal of solid waste.

Comprehensive environmental impact assessment and irrigation wastewater suitability of the Arab El-Madabegh wastewater treatment plant, ASSIUT CITY, EGYPT.

The presence of a wastewater treatment plant in the Arab El-Madabegh region, which discharges excessive amounts of raw effluent toward the nearby farming fields, is the area's main issue. Examining the harmful implications of raw effluent releases on groundwater quality, determining if treated wastewater effluent complies with regulations for discharge into the aquatic environment, and assessing irrigation appropriateness by the effluent are the main goals of this work. In order to accomplish these targets, twelve treated effluent samples from the Arab El-Madabegh wastewater treatment plant were gathered every two weeks starting in January 2012 and finishing in June 2012. They were tested to determine pH, Total Dissolved Solids (TDS), Total Suspended Solids (TSS), Temperature (Temp), Conductivity (EC), Turbidity (Turb.), Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD), Total Organic Carbon (TOC), NO3-, SO42-, Cl-, Ca2+, PO43-, HCO3-, Na+, Mg2+, and heavy metals such as (Fe, Mn, K+, Cr, Pb, Zn, Ni, Cu, and Cd). The outcomes revealed that all Egyptian and Food and Agricultural Organization (FAO) standards for unrestricted irrigation were met by the treated effluents, except for COD, which exceeded than the Egyptian allowed limit. The evaluation indices of the effluent's EC, SAR, PI, MR, and MH were in the low-risk category according to indicators of water quality for irrigation, nevertheless, The SSP and RSC both showed slightly higher values (67.9% and 2.76, respectively). As well, The average values of heavy metals in treated wastewater effluent were found to be below permitted limits, with the exception of lead and phosphate, which exceeded permissible limits in Egypt. The environmental sustainability (ecological friendliness) of reusing and recycling tertiary treated wastewater can be achieved in agriculture to reduce the adverse impacts on the aquatic environment.

PHYSICOCHEMICAL PROPERTIES AND BIOFLOCCULATING EFFICIENCY OF POLAR RESIDUE OF PARTITIONED EXTRACT OF TELFAIRIA OCCIDENTALIS LEAF

Water contamination has become more pronounced as a result of human economic growth all over the world. This study investigated the physicochemical properties and bioflocculating activity of the polar residue of partitioned extract (PRPE) of Telfairia occidentalis leaf. The bioflocculating activity of the extract was evaluated for optimum dosage, pH, temperature, and metal ion using Kaolin clay suspension; the optimum activities obtained were used in wastewater treatment. The optimum flocculating activity of the PRPE was obtained at the dose of 1 mg/mL, pH of 4, the temperature of 50°C, and divalent cation (Ca2+). The physicochemical characteristics of removal of turbidity, biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS) and heavy metals were determined before and after treatment. Upon treatment of two different domestic wastewaters (DW1 &amp; DW2), the physicochemical parameters were reduced except for nitrate and turbidity, which increased for DW2. The bioflocculant displayed the highest activity in DW1 with turbidity removal of 74%, TSS removal of 48%, nitrate removal of 24%, BOD and COD removal of 87.5% and 50% respectively. Heavy metals were also removed effectively in DW1 compared to DW2. The FTIR characterization revealed the presence of primary amine (N-H), cyclic alkene (C=C), phenol (O-H), sulfoxide (S=O) and, halo compound (C-Br) groups present in the bioflocculant which are essential as they promote the flocculation process. The findings from this study attest to the ability of PRPE of Telfairia occidentalis to act as a flocculant.

Emission inventory of heavy metals from on-road vehicles in Xiamen, China, from 2015 to 2060

Reducing vehicle emissions to improve air quality has been widely adopted by policy makers. However, insufficient attention has been paid to non-exhaust particulate matter (PM) and the associated heavy metals (HMs) from on-road vehicles, which can cause adverse health effects. In this study, emission inventories of PM2.5 and PM10 and the associated HMs from on-road vehicles in Xiamen, China, were established from 2015 to 2060 under a business-as-usual scenario. In the base year 2021, the total emissions of HMs associated with primary PM2.5 and PM10 were 1.88 × 104 kg and 3.96 × 104 kg, respectively, with the dominant contributions from brake wear and road surface wear. The emissions of HMs were overwhelmingly dominated by light-duty passenger cars and heavy-duty trucks. Fe, Ba, Zn, Cu, Mn, and Ti together accounted for about 97% of the total HMs. High-density emission areas were concentrated in urban centers. From 2015 to 2060, an increasing trend in total HMs emissions was observed due to the superimposed effect of decreasing diesel exhaust and increasing non-exhaust brake wear and road wear. However, the trends of the individual HMs were different from each other. The U-shaped distribution patterns of the relative cancer and non-cancer risks of HMs were observed between 2015 and 2060. Vehicle electrification alone is not enough to effectively reduce the potential health risk of vehicle-related HMs in the future. Reducing HMs from brake wear should be encouraged to use in electric vehicle. Uncertainties in the emissions of HMs were quantified using the Monte Carlo simulation.

Removal of Heavy Metals from Petroleum Industry Wastewater Using Indigenous Microalgae &lt;i&gt;Scenedesmus &lt;/i&gt;sp

Petroleum industry effluents contain hazardous compounds such as heavy metals, which can damage the environment and human health. In this work, petroleum wastewater used as a medium to culture marine algae Scenedesmus sp. with the aim of removing maximum heavy metals. The efficiency of Scenedesmus sp. were examined in laboratory scale for elimination of COD, BOD and total petroleum heavy metals. The marine algae were monitored in pure petroleum wastewater as well as 25%, 50% and 75% diluted wastewater samples which conducted for 15 days. At the condition of 27 ± 2 °C, Scenedesmus sp. removed 35 – 96% of chromium (IV), cadmium (II) and copper (II). Among them chromium (IV) was significantly removed by Scenedesmus sp. Hence, phytoremediation using Scenedesmus sp. is seen as one of the best options to remove heavy metals from petroleum wastewater. Keywords: Microalgae, Scenedesmus sp., heavy metals, wastewater, biomass

Investigation of Water Quality of River Poonch for Drinking and Irrigation Purposes

In the present work, we reported fifteen water samples that were collected from selected locations in the study area of Poonch River. All water samples were collected and labelled in polythene bottles at the sites where water depth was 1 meter. The river Poonch flows through Indian occupied Kashmir and Jammu and Kashmir in Pakistan. The collected samples were tested for major physical and chemical water suitability parameters such as pH, electrical conductivity total dissolved solids, total alkalinity total hardness chlorides, major metals and heavy metals standard. The aforementioned analysis of samples was reported by methods such as conductometery, potentiometery and atomic absorption spectrometry.

Environmental assessment of Heavy Metals in Sedi - ments of Tigris, Euphrates, Shatt Al-Arab rivers and northern west of Arabian Gulf.

The most prevalent environmental contaminants found in sediments that suggest the presence of effluents from both home and industrial sources are thought to be heavy metals. The aim of this study was to assess the accumulation of heavy metals at surface sediment samples that were collected in order to measure the amounts of Cu, Zn, Pb, Cd, and Fe., to re-evaluate the environmental conditions and concentration of the analyzed elements in the sediment to detect any pollution of heavy metals in the studied area by using contamination factors (CF), Enrichment Factor (EF) and geo accumulation index (I-geo). To ascertain the connection between the sediment’s total organic carbon (TOC) level and heavy metal pollution, measurements were taken in addition of it. Using the inductively coupled plasma atomic emission spectrometer, studies were conducted., The mean values of the element in the sediments ranged as: Cu (13.45 μg/g at location 2 to 32.44 μg/g at location 9), Zn (20.76 μg/g at location 1 to 42.49 μg/g at location 10), Pb (9.78 μg/g at location 2 to 30.04 μg/g at location 9 and 10), Cd (7.89 μg/g at location 2 to 18.72 μg/g at location 7) and Fe (459.89 μg/g at location 1 to 833.83 μg/g at location 7) dry weight. The geochemical results show that the distribution and concentration of the heavy metals in the studied sediments is within the average concentration given for the FAO/WHO reported, and the sediment of the studied area is still free from pollution, except Pb and Cd in some local areas, which shows higher concentrations than those reported for world sediments.

Distribution, speciation, and assessment of heavy metals in sediments from Wadi Asal, Red Sea, Egypt

Globally, the environmental contamination of stream sediments due to geogenic and anthropogenic sources is of growing concern. In this study, the heavy metals (Cd, Co, Cr, Cu, Ni, Pb, and Zn) in 22 superficial sediments in Wadi Asal, Red Sea, Egypt, were explored to assess sediment sources, the mobility of chemical species, and the degree of contamination in sediments. Therefore, the total heavy metal values in the fine fraction (< 63 μm), a five-step sequential extraction on selective samples, risk assessment, and principal component analysis (PCA) were applied. The mobility of heavy metals in Wadi Asal sediments, according to non-residual fraction percent, declines in the following order: Cd (90.9%) > Pb (85.2%) > Co (84.4%) > Cu (80.8%) > Zn (75.9%) > Ni (48.4%) > Cr (39.6%); indicating the high mobility of Cd, Zn, Pb, Cu, and Co. The mean metal contamination factor (CF) order is Cd (10.96) > Ni (3.91) > Cr (2.77) > Zn (2.18) > Pb (2.10) > Co (1.12) > Cu (0.70). The Geo-accumulation Index (Igeo) is decreased in the following order: Cd (2.19) > Ni (0.78) > Cr (0.55) > Zn (0.44) > Pb (0.42) > Co (0.22) > Cu (0.14). The risk assessment code (RAC) revealed very high to high risk for Cd, Co, and Pb. The results pointed out that the metals Cr, Co, Cu, and Ni are from geogenic sources, while Zn, Cd, and Pb are from anthropogenic sources due to Pb–Zn mining activities. Based on the threshold effect level (TEL), Cd, Cr, Ni, and Pb have adverse effects on living organisms. According to these findings, the area along Wadi Asal and the downstream regions on the beach are highly polluted and heavy metal monitoring in sediments and aquatic organisms is recommended.

Risk assessment of Cr, As, and Sb to aquatic communities at the water-sediment interface in the lower Yellow River, China, integrated with the Diffusive Gradients in Thin‐films technique

The dynamic concentrations of labile metals/metalloids, measured by the Diffusive Gradients in Thin-films (DGT) technique, can be used for evaluating the toxicity risk of heavy metals to aquatic organisms in sediments. In this study, the different potential risks of the three sediment compartments, overlying water (W), sediment- water interface (SWI) and sediment (S) were independently assessed by studying the concentrations of Cr, As, and Sb in the sediment and water from the lower Yellow River. Total concentrations of these elements and bioavailable concentrations, using DGTs, were explored and probabilistic risk assessment (PRA) based on a Monte Carlo model was performed. The results show that the total heavy metal concentrations in sediment and overlying water were spatially variable due to influences of natural geography and sediment distribution. The trace elements mean concentrations using DGT were 1.68, 1.69 and 0.73 μg·L−1 for Cr, 0.61, 0.51 and 0.39 μg·L−1 for As, and 0.78, 1.16, and 0.41 μg·L−1 for Sb in W, SWI and S, respectively. Among them, the DGT-labile concentration of As displayed a large spatial variability, indicating a close association with anthropogenic activities. The risk quotient (RQ) categories for single heavy metal toxicity demonstrated to be moderate risk for Cr and almost no risk for As and Sb. The combined biotoxicity probability assessment of the three heavy metals showed that they would cause almost no harmful effects to benthic organisms in the whole ecosystem of the Yellow River.

A novel bioaccessibility-based probabilistic risks assessment of potentially toxic elements (PTEs) in earthworm.

Introduction: Early risk assessment studies usually based on total heavy metal (loid) contents, inevitably leading to an overestimation of the health risks. In addition, inputs are represented as single-point estimates in deterministic models, leading to underestimation or overestimation of the health risks. Methods: To overcome these barriers, a novel probabilistic risk assessment strategy based on the combinational use of bioaccessibility and Monte Carlo simulation was developed to assess heavy metal (loid) associated health risks of earthworms in this study. To obtain a realistic and robust probabilistic risk assessment, heavy metal (loid) exposure duration and frequency were determined using our questionnaire data. Results: As a result, the mean gastrointestinal bioaccessibility was in the order: Cd > As > Cu > Hg. The mean hazard index (HI) values for investigated metal (loid)s were 0.65 and 0.59 for male and female, respectively, demonstrating an acceptable health risk in an average community. However, the 90th percentile of HI values was 1.87 and 1.65 for male and female, respectively. And the total non-cancer risks of heavy metal (loid) exposure exceeded the acceptable threshold for 19.9% and 17.8% of male and female, respectively. In addition, the total cancer risk (TCR) value through co-exposure to As and Cd suggested that the carcinogenic risks may be of concern for average exposure population. Sensitivity analyses revealed that the exposure frequency and bioaccessible As concentration were the dominant contributors to the total risk variance, which provided meaningful implications for environmental management. Conclusion: Altogether, the refined strategy based on bioaccessibility and Monte Carlo simulation is the first of its kind, such effort attempts to scientifically guide the rational clinic use of TCM and the improvement of population-health.

Concentrations of Hydrocarbons and Heavy Metals in Groundwater from Andoni Local Government Area of Rivers State Nigeria

The concentrations of Polycyclic Aromatic Hydrocarbons (PAHs), Total Hydrocarbons contents (THCs) and heavy metals in groundwater from parts of Andoni Local Government Area in Rivers State were determined using Gas Chromatography-Mass Spectroscopy for PAHs, Spectrophotometer for THC and Atomic Absorption Spectrophotometer for heavy metals. The results showed maximum mean levels of Polycyclic Aromatic Hydrocarbons (0.642 ppm) and Total Hydrocarbons content (3.23±4.24 ppm), Manganese (0.705±0.125), Iron (0.217±0.300), Lead (0.355±0.488), Chromium (0.096±0.132) and Nickel (0.151±0.149) mg/L. The Polycyclic Aromatic Hydrocarbon levels were above permissible limits and the Total Hydrocarbons content levels were above acceptable limits in some stations. Lead and nickel levels were above standard limits in some stations. The high levels of lead and nickel portend toxic and carcinogenic risks in some stations, especially to the environment and children in the study areas. The results showed that Groundwater in the study area is poor for drinking purposes in some areas and can pose health hazards in the area if consumed without proper treatment. Thus, adequate treatment of the groundwater in the affected areas is recommended.

Migration of total petroleum hydrocarbon and heavy metal contaminants in the soil-groundwater interface of a petrochemical site using machine learning: impacts of convection and diffusion.

Convection and diffusion are key pathways for the migration of total petroleum hydrocarbons (TPH) and heavy metals (HMs) from soil to groundwater. However, the extent of their influence on pollutant migration, as well as the nonlinear relationships between these processes and pollutants, remains unclear. This study investigates the spatial distribution of TPH and HMs at a petrochemical site with complex hydrogeological conditions in southwestern China. In addition, machine learning (ML) was used to assess the effects of convection and diffusion on pollutant migration at the soil-groundwater interface. The analysis identifies and reveals TPH, Co, and Ni as the primary pollutants, with soil concentrations reaching 47.427, 7.024, and 4.766 times their respective screening values. Among various ML models, Random Forest (RF) was identified as the most effective, based on R 2, and RMSE performance metrics. The RF model demonstrates that the concentrations of TPH and As are closely related to soil depth. Furthermore, importance indices calculated by RF indicate that the significance of convection and diffusion varies across different soil-groundwater systems. Specifically, at the soil-perched water interface, convection plays a more significant role than diffusion in influencing the migration of TPH and As. However, at the soil-pore water interface, diffusion more significantly influences the migration of all pollutants compared to convection. Additionally, a threshold or saturation effect was observed for the impact of the convection factor on pollutant concentrations in groundwater. These findings highlight the distinct roles of convection and diffusion across various water interfaces, providing new insights into the mechanisms governing contaminant migration and fate.

Prediction of heavy metal ion distribution and Pb and Zn ion concentrations in the tailing pond area.

The pollution caused by tailings ponds has resulted in ecological damage, with soil contamination significantly impacting the daily lives of residents in the vicinity of mining areas and the future development of mining areas. This study assesses the transport status of heavy metal pollution in tailings areas and predicts its impact on future pollution levels. This study focused on lead-zinc tailing ponds, exploring the spatial and chemical distribution characteristics of heavy metals based on the distributions of Pb, Zn, As, Cu, Cr, Cd, Hg, and Ge ions. The concentrations of the major heavy metal ions Pb and Zn in tailings ponds were predicted via the exponential smoothing method. ① The total accumulation of Pb and Zn in the mine tailings ranges from 936.74~1212.61 mg/kg and 1611.85~2191.47 mg/kg, much greater than the total accumulation of the remaining six heavy metals. The total accumulation of associated heavy metal Cu was high, and the lowest total heavy metals were Hg and Ge at only 0.19 mg/kg and 1.05 mg/kg. ② The analyses of soil heavy metal chemical forms reveal that the heavy metals Pb and Zn had the highest exchangeable state content and state ratio and the strongest transport activity in the industrial plaza and village soils. Pb and Zn are the heavy metals with the greatest eco-environmental impacts in the mining area. ③ The predicted results show that the soil concentrations of the heavy metals Pb and Zn around the tailings area in 2026 are 1.335 and 1.191 times the predicted time starting values. The concentrations of the heavy metals Pb and Zn at the starting point of the forecast are already 3.34 and 3.02 times the upper limits of the environmental standard (according to environmental standards for gravelly grey calcium soils). These results have significant implications for heavy metal pollution risk management.

Chemical sensor thin film-based carbon quantum dots (CQDs) for the detection of heavy metal count in various water matrices.

Rising pollution of heavy metals is one of the greatest concerns, especially in water resources globally and has led to significant adverse effects to human health. To uplift the status of human health, detection of heavy metals is of key importance. This study establishes the ability of carbon quantum dot (CQD)-based thin films for the detection of total heavy metal counts based on a fluorescence-based mechanism in various water resources using a fiber optic spectrometer (FOS) device. CQDs and CQD thin films were characterized using various techniques, such as X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), X-ray diffraction (XRD), and confocal laser scanning microscopy (CLSM), and the sensing capability was evaluated for the detection of heavy metals using an optical fiber system. The analytical parameters of the CQD-based thin film were compared with the estimation carried out using a micro plasma-atomic emission spectroscopy (MP-AES) method. The sensing performances of CQD thin films indicate that they are able to detect five heavy metals individually (lead, nickel, manganese, cobalt and chromium) in combination with a response time of 1 minute. The CQD thin films were able to detect heavy metals with a detection limit of 0.006-0.019 ppm for the analyzed heavy metals with a linear range of estimation analyzed as 0-100 μM. The accuracy of the estimation of all five heavy metals when spiked in various real water samples lies in the range of 100-103%. The result of the study clearly indicates that CQD thin films associated with a fiber optic device have the potential to play a role in point-of-care devices for total heavy metal count detection in complex matrices of water.

Assessment of Heavy Metal Pollution from Granite Quarrying in Akure, Nigeria

This study investigated the heavy metals pollution of granite quarrying activities in Akure, Ondo State, Nigeria. Three quarries and a control site were selected for this study. Plants and soil samples were collected at 0, 50, 100, 150 and 200 m away from the crushing points, while samples were collected away from roadside for control. Water samples were collected at just a point. Concentration of heavy metals in collected samples was determined using Buck Scientific Atomic Absorption Spectrophotometer model 210 VGP. The mean total heavy metal contents in C. odorata and P. purpurem collected within 0 to 200 m showed that Pb, Fe, Zn, Cr Co and Cd contents were above the WHO permissible limit while only Pb content (190.8, 299.20 and 208.80 ppm) and Fe (7559.50, 13386.50 and 19019.50 ppm for Dortmond, Ebenezer and Samchase quarries respectively) were above the permissible limit in soil samples. Elevated Pb, Fe, Cr, and Ni were recorded in water samples collected from quarry sites while values recorded for control sites falls within the permissible limit except for the lead concentration of 0.10 ppm as against the maximum concentration of 0.05 ppm set by WHO. Zn, Mn, Cd and and Cu were not detected in all water samples. Higher pH values were also recorded in soil and water samples from quarry sites. This study has shown that quarrying introduces toxic heavy metals into nearby environment.

Size-classified aerosol-bound heavy metals and their effects on human health risks in industrial and remote areas in Japan

Airborne aerosols were collected in six size classes (PM<0.1, PM0.1–0.5, PM0.5–1, PM1–2.5, PM2.5–10 and PM>10) to investigate aerosol health risks in remote and industrial areas in Japan. We focused on heavy metals and their water-dispersed fractions. The average concentration of heavy metals was 18 ± 25–86 ± 48 ngm−3 for PM<0.1, 46 ± 19–154 ± 80 for PM0.5–1 ngm−3, 98 ± 49–422 ± 186 ngm−3 for PM1–2.5, 321 ± 305–1288 ± 727 ngm−3 for PM2.5–10 and 65 ± 52–914 ± 339 ngm−3 or PM>10, and these concentrations were higher in industrial areas. Heavy metals emitted from domestic anthropogenic sources were added to the long-range transport component of the aerosols. The water-dispersed fraction of heavy metals contained 3.3–40.1% of the total heavy metals in each size class. The relative contribution of Zn and other species (As, Cd, Cr, Ni, Pb, Mn, V and Cu) increased in the water-dispersed fraction. Smaller particles contained greater proportions of the water-dispersed heavy metal fraction. Carcinogenic risk (CR) and the hazard index (HI) were estimated for each size class. The CR of carcinogens was at acceptable levels (<1 ×10−6) for five particle size fractions. The HI values for carcinogens and noncarcinogens were also below acceptable levels (<1) for the same five size fractions. The estimated CR and HI values were dominated by contributions from the inhalation process.

Potential of ash from agricultural waste as substitute of commercial FeCl3 in primary treatment of landfill leachate

Due to the ever increasing global population, higher volumes of industrial waste discharges to landfill have caused major problems for the environment. This study investigated the performance of rice straw ash (RSA) as a natural coagulant under different conditions for the treatment of landfill leachates by coagulation-flocculation and microfiltration, with and without addition of FeCl3. The highest performing treatment conditions (RSA = 2.48 g/L, FeCl3 = 4.98 g/L, settling time = 54.75min) were achieved with the combined use of RSA and FeCl3 as coagulant and led to a sludge volume index of 41.65 mL/g, 51.27% COD removal and 76.48% total suspended solid removal. In contrast, FeCl3 alone achieved slightly better COD and total suspended solid removal rates, however it resulted in higher sludge volume index and sludge production. The combined use of RSA and FeCl3 reduced the consumption of these two coagulants by 78.76% and 46.69% respectively. Functional groups and thermal stability of the flocs showed that RSA + FeCl3 synergistically enhance the mechanisms of the coagulation-flocculation process, including adsorption by particle's bridging, charge neutralization and size of flocs. Combining the coagulants resulted in increased van der Waals forces and lower attractive forces of the inter-colloidal energy barrier in the leachate. Additionally, the highest and lowest heavy metals removal rates for treatment by microfiltration were found for Fe (92.15%) and Mg (7.63%), with a total heavy metals removal efficiency in the range of 6.08–90.78%. The findings of this study show that RSA can serve as a natural eco-friendly coagulant both alone and in combination with FeCl3 in the leachate treatment.

The effect of ascorbic acid and lemon juice on the extraction of metals from green tea, health risk assessment

The total heavy metal concentration (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn) in green tea leaves and metals leached into tea infusions of pure water with the addition of ascorbic acid and lemon juice at various temperatures (70, 80, and 100 °C) and steeping times (3, 5, and 7 min), were determined. Metal concentrations were analyzed by atomic absorption spectrometry and the flame technique (FAAS). Mean total concentrations of Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn were < LOD, <LOD, 0.198, 4.527, 67.51, 333.7, 2.588, <LOD, 10.23 μg/g, respectively. The highest percentage of extraction in different solutions was in the case of Mn (up to 100%). The risk for adults through consumption of tea was mainly contributed by Mn, and non-carcinogenic hazard quotient (HQ) was slightly higher than 1 when infusions were heated to 100 °C. High percentages of Ni were extracted in pure water compared to water with addition, regardless of tea steeping time, followed by Cu in pure water and water with lemon juice. Fe was poorly extracted in all applied solutions; the highest percentage of extraction (17.21%) was determined in lemon juice solutions of at 100 °C during a steeping time of 7 min.

Агроэкологическая характеристика черноземов Каменной степи: влияние растительных сообществ и распашки

Changes in soil carbon stocks have a significant impact on atmospheric CO2 concentrations and the global carbon balance. Despite the proven effectiveness of agroforestry in erosion control and prevention of soil fertility loss, there are many controversial data suggesting that the impact of afforestation on Chernozem soils should be further investigated. The Kamennaya Steppe site (arable land surrounded by shelterbelt forests) is a reference site for monitoring studies at the Voronezh Carbon Test Site, where the carbon balance of agro-ecosystems is being studied and the ecological role of shelterbelt forests in changing soil properties and carbon sequestration is being evaluated. The study was focused on the evaluation of agro-ecological characteristics and the impact of tillage on Chernozems of Kamennaya Steppe under different vegetation types. The study of the chemical properties of chernozems was carried out using classical chemical methods; the analysis of heavy metals was carried out using the voltampermetric method. Comprehensive agro-ecological evaluation showed that the studied Vorony-Calcic Chernozems had a high content of humus, which reached 7-8% in the upper horizons, enriched with mineral nutrition elements, and had favorable physical and chemical properties. Forest and grassland vegetation contribute to enrichment of the soil with organic residues, while tillage and mineralization of organic matter on arable land led to a decrease in humus content. Data analysis suggested that the study area did not suffer from contamination. Furthermore, it was found that the organic matter of the studied chernozems was able to bind the studied metals and retain them in an unavailable state. This phenomenon was supported by rather high correlations between humus and total heavy metal content (r = 0.946 for Pb and r = 0.975 for Cd at p &lt; 0.00001). It should be emphasized that shelterbelt forests could act as a biogeochemical barrier to the lateral migration of heavy metals. Cadmium is a rather mobile element potentially capable to migrate to adjacent environments. Therefore, regular monitoring of the agro-ecological condition of the Chernozems of the Kamennaya Steppe is required.