Total Pb Concentrations Research Articles

Integrated assessment of the impact of land use types on soil pollution by potentially toxic elements and the associated ecological and human health risk

The impact of land use type on the content of potentially toxic elements (PTEs) in the soils of the Qinghai-Tibet Plateau (QTP) and the associated ecological and human health risks has drawn great attention. Consequently, in this study, top- and subsurface soil samples were collected from areas with four different land uses (i.e., cropland, forest, grassland, and developed area) and the total contents of Cr, Cd, Cu, Pb and Zn were determined. Geostatistical analysis, self-organizing map (SOM), and positive matrix factorization (PMF), ecological risk assessment (ERA) and human health risk assessment (HRA) were applied and used to classify and identify the contamination sources and assess the potential risk. Partial least squares path modeling (PLS-PM) was applied to clarify the relationship of land use with PTE contents and risk. The PTE contents in all topsoil samples surpassed the respective background concentrations of China and corresponding subsurface concentrations. However, the ecological risk of all soil samples remained at a moderate or considerable level across the four land use types. Developed area and cropland showed a higher ecological risk than the other two land use types. Industrial discharges (32.8%), agricultural inputs (22.6%), natural sources (23.7%), and traffic emissions (20.9%) were the primary PTE sources in the tested soils, which indicate that anthropogenic activities have significantly affected soil PTE contents to a greater extent than other sources. Industrial discharge was the most prominent source of non-carcinogenic health risk, contributing 37.7% for adults and 35.2% for children of the total risk. The results of PLS-PM revealed that land use change associated with intensive human activities such as industrial activities and agricultural practices distinctly affected the PTE contents in soils of the Qinghai-Tibet Plateau.

Deep eutectic solvents for the removal of lead contaminants in mangrove soil

The remediation of heavy metal contaminated mangrove soil with proper washing agents is critical for reducing the harmfulness of heavy metal contaminated soil to the environment. This work is aimed to investigate the potential of natural-based deep eutectic solvents as soil washing agents. Choline chloride (ChCl) and two organic acids, lactic acid and levulinic acid, are used as degradable and natural washing agents to remove Pb in the soil. Results verified that ChCl: Lactic Acid (1:2) [ChCl-LacA] and ChCl: Levulinic Acid (1:2) [ChCl-LevA] were found to be suitable for the removal of Pb from the contaminated soils, which significantly lowers the total Pb concentration in the soil. The high distribution ratio from the Conductor-like Screening Model for Real Solvents (COSMO-RS) screening gave an early indication that natural acid DESs are effective soil washing agents. The effect of washing agent concentration, soil to liquid ratio, contact time, and the interaction between acid DESs and metal ions was evaluated. ChCl-LacA and ChCl-LevA remove lead to 97% and 99%, respectively, under optimum conditions. ICP-MS, XRD, and FTIR spectroscopy analysis clarified the interaction between DES and metal ions. As a washing agent, green and natural DESs provide an environmentally sustainable alternative. Employing soil washing to remove heavy metals is a simple, rapid, and cheap remediation technology that could potentially be used in mitigating soil pollution.

Effect of Marginal-Quality Irrigation on Accumulation of some Heavy Metals (Mn, Pb, and Zn) in TypicTorripsamment Soils and Food Crops

Lack of active sorption sites in sandy soils renders metals added by irrigation water more labile and increases their soil-to-plant transfer. Thus, this study investigated the long-term impacts of irrigation using sewage effluents and contaminated groundwater on metal accumulations in TypicTorripsamment soils, and edible parts of food crops. Nine sites in El-Gabal El-Asfar farm, south-eastern to the Nile Delta of Egypt, were selected. At each site, irrigation water, soil (0–30 cm), and the crop’s edible part were sampled in triplicates and analyzed for Mn, Pb, and Zn. Results revealed significant (p < 0.05) differences in metal concentrations among water sources. Thus, constant irrigation caused significant spatial variations in total and available metal contents in soils. Total contents of Pb (in four sites) and Zn (in all sites) exceed the lithosphere range, while the available contents of the three metals exceeded the safe limits in all soils. The index of geo-accumulation indicated no Mn pollution but showed elevated pollution risks for Pb and Zn. The three metals showed high availability ratios, proving the effect of light soil texture. The multivariate statistical analysis indicated that Mn and Zn had similar geochemical behaviors in soils. Metal contents in all crop’s edible parts surpassed the safe limits. The bioaccumulation factor (BAF) was less than 1.0 for Mn and Zn but higher than 1.0 for Pb. The highest BAFs occurred in cabbage leaves, indicating the phytoextraction potential of this species. Sufficient water treatment and proper remediation techniques are recommended to alleviate metal accumulation in food crops and their transfer via the food chain.

Variation and factors on heavy metal speciation during co-composting of rural sewage sludge and typical rural organic solid waste

In this study, a co-composting of rural organic solid waste (rural sewage sludge, kitchen waste and corn stalks) was conducted to analyze the variation of heavy metals (As, Cu, Cr, Ni, Pb, Hg, and Zn) and their major influencing factors. During composting, significant changes were observed in the total contents of heavy metals (p < 0.01): the total concentrations of As, Cu, Hg, Pb and Zn increased by 7.5%, 54.1%, 26.3%, 15.8%, and 34.2%, whereas that of Cr and Ni decreased by 71.3% and 33.4%, respectively. Heavy metals were mainly bound to the oxidizable and residual fractions. Spearman and Redundancy analysis (RDA) indicated that substances were significantly correlated with the changes in speciation of heavy metals, among all the factors, while pH and temperature were the dominating environmental influencing parameters. Several metal-resistant bacterial genera (Pseudomonas, Paenibacillus, Bacillus, Acinetobacter, Desulfovibrio, and Ochrobactrum, etc) were observed, with significant explanatory capacity for the changes in heavy metals. Composting showed a poor effect on heavy metal passivation, except for that of As. After composting, the heavy metal contents were consistent with the application standards. The evaluation of potential ecological risk showed a high cumulative ecological risk (336.9) of heavy metals. This study provides technical support and practical information for the disposal and safe recycling for rural organic solid waste.

The effect of resource-saving tillage technologies on the mobility, distribution and migration of trace elements in soil.

The influence of agricultural tillage technologies on the accumulation and distribution of trace elements in the soil is poorly studied. At the same time, intensive agriculture requires large amounts of fertilizers, growth stimulators, pesticides, and other substances, which can effect the ecological safety of the plant products and soil. This paper represents studying the effect of various agricultural techniques (including resource-saving technologies) on the mobility and profile distribution of Pb, Zn, and Cu in Haplic Chernozem. No significant influence of resource-saving tillage technologies was found on the total Pb content. Contrary, the resource-saving tillage technologies was observed to promote the growth of the total Zn and Cu content depending on the cultivation method (by 26% Zn, 34% Cu at minimal tillage, and 28% for both elements using No-till in Ap horizon). Amongst different applied agrotechnologies, there was no influence found on the profile distribution of total elements content. Only two horizons showed the total Pb content accumulation: biogenic (Ap-A) and carbonate (BC-C) horizon. In contrast, the only biogenic accumulation for Zn was determined. Copper characterizes by even distribution over the soil profile. The use of resource-saving agricultural technologies increases exchangeable fraction of Zn, Pb and Cu in soil almost by 1.5-2.0 times in the Ap horizon compared to moldboard ploughing. Despite the increase in the exchangeable fraction of Zn and Cu, this amount of micronutrients is not enough for adequate plant nutrition. The use of various agricultural technologies at Haplic Chernozem led to changes in the distribution of studied elements' exchangeable fraction over the soil profile. The study results suggested a need to increase the amount of Cu and Zn fertilizers applied to the soil with resource-saving cultivation technologies.

Retention of trace elements in coal-fired flue gas by a novel heterogeneous agglomeration technology

Heterogeneous agglomeration (HA) is a very potential technology for coal-fired flue gas treatment. In this paper, the distribution and migration mechanisms of trace elements (TEs) such as Se, As and Pb in CFPPs were studied on a 30,000 m3/hr pilot-scale experimental platform. The influences of HA on the removal efficiency of gaseous and particulate TEs were well analyzed. The results showed that Se, As and Pb were enriched in fly ash, and their sensitivity to particle size is quite different. The content of Se was the highest in PM1, reaching 193.04 mg/kg at the electrostatic precipitator (ESP) outlet. The average particle size of the total dust before ESP increased significantly from 21.686 to 62.612 µm after injecting the heterogeneous agglomeration adsorbent, conducive to its further removal by ESP. In addition, the concentrations of gaseous Se, As and Pb in the flue gas decreased after adsorbent spray, and accordingly, their contents in the hierarchical particles increased, indicating that the adsorbent could effectively promote the adsorption of gaseous trace elements in fly ash and reduce the possibility of their escape to the atmosphere. Total concentrations of Se, As and Pb emitted by wet flue gas desulfurization (WFGD) are 0.223, 0.668 and 0.076 µg/m3, which decreased by 59.98%, 47.69% and 90.71%, respectively. Finally, a possible HA mechanism model was proposed, where chemical adsorption, physical condensation and collision agglomeration of gaseous TEs and fine particles with adsorbent droplets occurred to form larger agglomerates.

Toxic elements in children’s crayons and colored pencils: Bioaccessibility assessment

Crayons and colored pencils for children may contain toxic elements (TEs) exhibiting potential risk for children?s health including cognitive development, after their ingestion, through mouthing and chewing and eventually, their accumulation. The aim of this study was to determine total content of As, Pb, Cr, Cd, Ni and Sb and estimate their bioaccessibility conducting artificial saliva extraction. Sixty samples of colored pencils and crayons from 10 manufacturers were analyzed. Microwave acid assisted digestion followed by inductively coupled plasma optical spectroscopy (ICP-OES) was performed for determination of total content of TEs. Simulation of extraction by artificial saliva was applied to get more reliable data when bioavailability is concerned. The total concentrations of TEs were higher in colored pencils than in crayons and their maximum levels were: 5.78, 9.36, 9.97, 0.615, and 6.63 mg kg-1 for As, Pb, Cr, Cd and Ni, respectively. Concentration of Sb was below the detection limit for all investigated samples. This study showed that concentration of As and Pb in several samples did not comply with European Union regulative. Bioaccessibility study showed the high degree of leaching of Cr and As from pencils, but regardless of extracted portions, concentrations of selected investigated TEs were below allowed levels.

Interactive Effects of Soil Lead and Cadmium on Dry Matter Yield and Metal Content of Indian Mustard (Brassica juncea (L.) Czern)

Lead (Pb) and cadmium (Cd) are known to influence each other’s uptake by plants when they coexist in the soil in significant amounts. This influence can be useful if it is antagonistic but may be detrimental if synergistic. In a screenhouse, interactive effects of soil Cd (0, 10, 25, 50 and 100 mg kg-1) and Pb (0, 25, 50, 100 and 200 mg kg-1) were studied on dry matter yield (DMY), Cd and Pb content in Indian mustard (Brassica juncea (L.) Czern) grown for 60 days in a loamy sand soil. The DMY was recorded and plants were analyzed for total Cd and Pb contents. In equilibrated soil there was significant increase in the mean DTPA-Cd and DTPA-Pb with increase in levels of their respective spiking. The content of DTPA-Cd increased significantly where different combinations of Cd and Pb were applied whereas, DTPA-Pb significantly decreased when Pb was applied in combination with Cd. At Cd+200 mg Pb kg-1 soil and Pb+100 mg Cd kg-1 soil, the mean shoot DMY of Indian mustard decreased by 55.8 and 57.7 per cent, respectively as compared to control. The mean shoot Cd content of Indian mustard increased by 9.9 per cent with application of Cd+200 mg Pb kg-1 soil while the mean Pb content decreased by 10.4 per cent with application of Pb+100 mg Cd kg-1 soil as compared to their respective single treatments. The post-harvest soil DTPA-Cd and Pb decreased as compared to their pre-sowing contents but considerable residual contents still remained in soil. An additive adverse effect of the metals on DMY, Pb and Cd content of the crop was observed.

Influence of Seed Source and Soil Contamination on Ecophysiological Responses of Lavandula pedunculata in Rehabilitation of Mining Areas.

Mining activities have turned many areas of the Iberian Pyrite Belt (IPB) into extreme environments with high concentrations of metal(loid)s. These harsh conditions can inhibit or reduce the colonization and/or development of most vegetation. However, some species or populations have developed ecophysiological responses to tolerate stress factors and contaminated soils. The main objectives of this study are: (i) to assess the differences in germination, growth, development and physiological behaviour against oxidative stress caused by metal(loid)s in Lavandula pedunculata (Mill.) Cav. from two different origins (a contaminated area in São Domingos mine, SE of Portugal and an uncontaminated area from Serra do Caldeirão, S of Portugal) under controlled conditions; and (ii) to assess whether it is possible to use this species for the rehabilitation of mine areas of the IPB. After germination, seedlings from São Domingos (LC) and Caldeirão (L) were planted in pots with a contaminated soil developed on gossan (CS) and in pots with an uncontaminated soil (US) under controlled conditions. Multielemental concentrations were determined in soils (total and available fractions) and plants (shoots and roots). Germination rate, shoot height, dry biomass and leaf area were determined, and pigments, glutathione, ascorbate and H2O2 contents were measured in plant shoots. Total concentrations of As, Cr, Cu, Pb and Sb in CS, and As in US exceed the intervention and maximum limits for ecosystem protection and human health. The main results showed that L. pedunculata, regardless of the seed origin, activated defence mechanisms against oxidative stress caused by high concentrations of metal(loid)s. Plants grown from seeds of both origins increased the production of AsA to preserve its reduction levels and kept the contents of GSH stable to maintain the cell’s redox state. Plants grown from seeds collected in non-contaminated areas showed a high capacity for adaptation to extreme conditions. This species showed a greater growth capacity when seeds from a contaminated area were sown in uncontaminated soils. Thus, L. pedunculata, mainly grown from seeds from contaminated areas, may be used in phytostabilization programmes in areas with soils with high contents of metal(loid)s.

Soil lead distribution in Chicago, USA

Identifying the distribution of soil lead (Pb) in urban areas can serve to quantify the location and magnitude of health risks, and thereby inform urban land use and Pb mitigation policies. We evaluated total soil Pb distribution across the third largest metropolitan region of the United States (U.S.), Chicago, a city with multiple historical sources of Pb deposition and previous reports of soil total Pb that exceed geogenic concentrations by orders of magnitude. Total Pb was quantified in Chicago soils obtained by grid sampling (n = 995) parkways and residential properties (n = 156). As anthropogenic modification of soils that entail Pb accumulation may also alter other properties, soil pH, clay content, and Olsen P were also measured. Median and mean total Pb was 220 and 282 mg kg−1 for parkway soils, and 146 and 352 mg kg−1 for residential soils. For parkway soils, 93% of the city area exceeded the conservative California EPA threshold of 80 mg kg−1 but 94% of the area was below the U.S. and Illinois EPA threshold of 400 mg kg−1. Hotspots of soil Pb exceeding the U.S. EPA inhalation risk threshold of 400 mg kg−1 occurred for an estimated area of ≈ 38 km2, representing ≈ 6% of the total area of 606 km2. Soil Pb distributions based on parkway sampling were higher by 100 mg kg−1 for ≈ 23% of the city compared to residential sampling. Soil properties of Olsen P, pH, clay, sand, and silt were unrelated to total Pb concentrations, though a significant negative linear relationship between Olsen P and soil pH was found for 13% of soil sampling locations. Across Chicago, the majority of soils in parkways and residential properties appear to be enriched in total Pb concentrations, indicating widespread but non-severe contamination.

Distribution and contamination assessment of heavy metals in soils and sediments from the Fildes Peninsula and Ardley Island in King George Island, Antarctica

Concentrations of heavy metals (Cu, Pb, Zn, Cd and Cr) in surface soils and sediments collected in 2008 from 37 sampling sites in the Fildes Peninsula and Ardley Island were detected by atomic absorption spectrometry. The total contents of Cu, Pb, Zn, Cd and Cr ranged, respectively, from 61.36 to 562.2 mg/kg, 0.52 to 1.95 mg/kg, 54.61 to 577.9 mg/kg, 0.04 to 3.76 mg/kg and 6.83 to 25.9 mg/kg in soils and from 58.55 to 498.3 mg/kg, 0.60 to 2.51 mg/kg, 56.22 to 345.9 mg/kg, 0.07 to 5.77 mg/kg and 7.76 to 39.5 mg/kg in sediments. The geo-accumulation index and the pollution load index were calculated to evaluate the environmental effects of heavy metal pollutants, Cu, Zn and Cd, in the study area. Soils and sediments from Ardley Island were found to be moderately polluted with the studied metals. Pearson’s correlation analysis and principal component analysis were applied to assess the distribution pattern and potential source of heavy metals. The results suggest that Cu, Zn and Cd in the study area originated from both the lithogenic sources and penguin guano, while Pb and Cr were probably derived from lithogenic sources.

A comparative study on characteristics and leaching toxicity of fluidized bed and grate furnace MSWI fly ash

Grate furnace and fluidized bed are the most widely used technologies for municipal solid waste incineration (MSWI), which play significant roles in characteristics of MSWI fly ash. A comparative study of the physicochemical characteristics, microstructure morphology and leaching toxicity of fluidized bed and grate furnace MSWI fly ash was conducted in this work, and some resource utilization and disposal treatments were proposed. Results showed that calcium salt and chlorine salt formed the dominant components of MSWI fly ash. CaO–SiO2–Al2O3 ternary system indicated that MSWI fly ash had potential pozzolanic activity, similar to coal fly ash and blast furnace slag. The total Pb, Cd and Zn contents in fluidized bed MSWI fly ash was only 1/2, 1/3 and 2/3 of grate furnace MSWI fly ash, respectively. Leachability of Pb in MSWI fly ash collected from Dalian, Shanghai, Zhuji and Hangzhou was 4.25 mg/L, 3.83 mg/L, 3.84 mg/L and 3.68 mg/L, 28.3, 25.5, 25.6 and 24.5 times as much as the national standard limitation (GB16889-2008), respectively. However, grate furnace MSWI fly ash with high chloride and unstable chemical speciation distribution of heavy metals would pose more environmental risk toits immobilization and disposal. Fluidized bed fly ash is a promising candidate for preparing the Portland cement clinker, microcrystalline glass and ceramics due to its high Si and Al content. Grate furnace MSWI fly ash is more appropriate for Alinite cement preparation because of high chloride content.

Environmental Pollution Indices and Multivariate Modeling Approaches for Assessing the Potentially Harmful Elements in Bottom Sediments of Qaroun Lake, Egypt

This research intends to offer a scientific foundation for environmental monitoring and early warning which will aid in the environmental protection management of Qaroun Lake. Qaroun Lake is increasingly influenced by untreated wastewater discharge from many anthropogenic activities, making it vulnerable to pollution. For that, six environmental pollution indices, namely contamination factor (Cf), enrichment factor (EF), geo-accumulation index (Igeo), degree of contamination (Dc), pollution load index (PLI), and potential ecological risk index (RI), were utilized to assess the bottom sediment and to determine the different geo-environmental variables affecting the lake system. Cluster analysis (CA), and principal component analysis (PCA) were used to explore the potential pollution sources of heavy metal. Moreover, the efficiency of partial least-square regression (PLSR) and multiple linear regression (MLR) were tested to assess the Dc, PLI, and RI depending on the selected elements. The sediment samples were carefully collected from 16 locations of Qaroun Lake in two investigated years in 2018 and 2019. Total concentrations of Al, As, Ba, Cd, Co, Cr, Cu, Fe, Ga, Hf, Li, Mg, Mn, Mo, Ni, P, Pb, Sb, Se, Zn, and Zr were quantified using inductively coupled plasma mass spectra (ICP-MS). According to the Cf, EF, and Igeo results, As, Cd, Ga, Hf, P, Sb, Se, and Zr demonstrated significant enrichment in sediment and were derived from anthropogenic sources. According to Dc results, all collected samples were categorized under a very high degree of contamination. Further, the results of RI showed that the lake is at very high ecological risk. Meanwhile, the PLI data indicated 59% of lake was polluted and 41% had PLI &lt; 1. The PLSR and MLR models based on studied elements presented the highest efficiency as alternative approaches to assess the Dc, PLI, and RI of sediments. For examples, the validation (Val.) models presented the best performance of these indices, with R2val = 0.948–0.989 and with model accuracy ACCv = 0.984–0.999 for PLSR, and with R2val = 0.760–0.979 and with ACCv = 0.867–0.984 for MLR. Both models for Dc, PLI, and RI showed that there was no clear overfitting or underfitting between measuring, calibrating, and validating datasets. Finally, the combinations of Cf, EF, Igeo, PLI, Dc, RI, CA, PCA, PLSR, and MLR approaches represent valuable and applicable methods for assessing the risk of potentially harmful elemental contamination in the sediment of Qaroun Lake.

Characteristics and sources of Pb exposure via household dust from the urban area of Shanghai, China

Household dust has been considered as an important pathway for children's environmental Pb exposure. Shanghai was one of the first cities in China that removed Pb from petrol and has been shown in our previous study to have the lowest childhood blood Pb levels in China. This study therefore examines household dust Pb (PbHD) in Shanghai in order to determine the extent and exposure risks of PbHD. Household vacuum cleaner dust samples (n = 40) were collected and analyzed for total Pb concentration, bio-accessible Pb concentration and Pb isotopic compositions (PbIC). The mean concentration of PbHD was 195 mg/kg, which is between 7 and 10 times the Pb concentration of background soil samples from Shanghai. Among the investigated homes, those living in neighborhoods with lower average estate prices have higher dust Pb exposure risks for children. Bio-accessibility of Pb in household dust ranged between 53 and 91%, with a mean value of 71%. Analysis of PbIC of household dust samples (208Pb/206Pb: 2.1096 ± 0.0054; 207Pb/206Pb: 0.8648 ± 0.0025) are a close match to PbIC of coal combustion and solid waste incineration and fit well with those of outdoor air PbIC and urban surface soil PbIC of Shanghai. The study shows that children living in Shanghai are subject to PbHD exposure, with children living in the homes with lower average price having increased susceptibility to PbHD exposure. The data indicate that PbHD is derived primarily from contemporary coal combustion and solid waste incineration rather than common legacy Pb sources (e.g., Pb petrol and paint). Practices including closing doors and windows on days with poor air quality or high wind and preventing shoe wearing inside homes will aid in minimizing outdoor surface soil and ambient particulate intrusion indoors.

Long-term and high-bioavailable potentially toxic elements (PTEs) strongly influence the microbiota in electroplating sites

Multiple potentially toxic elements (PTEs) wastes are produced in the process of electroplating, which pollute the surrounding soils. However, the priority pollutants and critical risk factors in electroplating sites are still unclear. Hence, a typical demolished electroplating site (operation for 31 years) in the Yangtze River Delta was investigated. Results showed that the soil was severely polluted by Cr(VI) (1711.3 mg kg−1), Ni (6754.0 mg kg−1) and Pb (2784.4 mg kg−1). The spatial distribution of soil PTEs performed by ArcGIS illustrated that the soil pollution varied with plating workshops. Hard Cr electroplating workshops (HCE), decorative Cr electroplating workshops (DCE) and sludge storage station (SS) were the hot spots in the site. Besides, the toxicity characteristic leaching procedure (TCLP) - extractable Cr and Ni contents in different workshops were significantly related (P < 0.05) to their bioavailable fractions (exchangeable fraction (F1) + bound to carbonate fraction (F2)), which pose potential risk to humans. Although the soil total Pb concentration was high, its mobility was very low (<0.007%). Moreover, the soil microbial community dynamics under the stress of long term and high contents of PTEs were further revealed. The soil microbiota was significantly disturbed by long term and high concentration of PTEs. A bit of bacteria (Caulobacter) and fungi (Cladosporium and Monocillium) showed tolerance potential to multiple metals. Furthermore, the canonical correspondence analysis (CCA) showed that the bioavailable fractions (F1 + F2) of Cr and Ni were the most critical environmental variables affecting microbiota. Therefore, remediation strategies are required urgently to reduce the bioavailability of soil Cr and Ni. The results of this study provide an overview of the pollution distribution and microbial dynamics of a typical plating site, laying a foundation for ecological remediation of electroplating sites in Yangtze River Delta of China.

Speciation and mobility of heavy metals in the Yundang Lagoon catchment surface sediments after 30 years of continuous remediation and management at Xiamen in China

ABSTRACT The present study emphasised the speciation and mobility of heavy metals (Cr, Mn, Ni, Cu, Zn, As, Cd, and Pb) in sediments of the Yundang Lagoon catchment (YLC) at Xiamen in China. The maximum total metals concentrations of Cr, Cu, Zn, Cd, and Pb were higher than the class I pollution level of China Marine Sediment Quality values. Average total metals concentrations of Cu, Zn, Cd, and Pb were greater than world average shale values. The highest average percentages of Cr (68.01%), Mn (39.14%), Ni (61.32%), and As (74.09%) were found in the residual fraction, while Cu (50.69%) was the highest in the oxidisable fraction. Furthermore, the greater percentages of Zn (37.65%), Cd (48.98%), and Pb (47.52%) were bound in the reducible forms in YLC sediment. Total organic carbon (TOC) showed a strong correlation with heavy metal fractions, suggesting that TOC could be a carrier of heavy metals within alkaline urban sediment. The risk assessment code values for Cd, Mn, and Zn indicate that these metals could pose a medium to a high potential risk to the aquatic organisms. However, the present remediation strategy should be continued with more focus on reducing urban runoff and domestic discharge into the lagoon.

Integral analysis of hydrodynamic cavitation effects on waste activated sludge characteristics, potentially toxic metals, microorganisms and identification of microplastics

Wastewater treatment plants, the last barrier between ever-increasing human activities and the environment, produce huge amounts, of unwanted semi-solid by-product - waste activated sludge. Anaerobic digestion can be used to reduce the amount of sludge. However, the process needs extensive modernisation and refinement to realize its full potential. This can be achieved by using efficient pre-treatment processes that result in high sludge disintegration and solubilization. To this end, we investigated the efficiency of a novel pinned disc rotational generator of hydrodynamic cavitation. The results of physical and chemical evaluation showed a reduction in mean particle size up to 88%, an increase in specific surface area up to 300% and an increase in soluble COD, NH4-N, NO3-N, PO4-P up to 155.8, 126.3, 250 and 29.7%, respectively. Microscopic images confirmed flocs disruption and damage to yeast cells and Epistilys species due to mechanical effects of cavitation such as microjets and shear forces. The observed cell ruptures and cracks were sufficient for the release of small soluble biologically relevant dissolved organic molecules into the bulk liquid, but not for the release of microbial DNA. Cavitation treatment also decreased total Pb concentrations by 70%, which was attributed to the reactions triggered by the chemical effects of cavitation. Additionally, the study confirmed the presence of microplastic particles and fibers of polyethylene, polyethylene terephthalate, polypropylene, and nylon 6 in the waste activated sludge.

Testing Homes for Potential Sources of Lead Exposure as a High-School Science Project.

High‐school students tested soil, paint, and water for lead (Pb) in a total of 80 houses in their town of Pelham, New York, where blood‐Pb data indicate relatively high levels of child exposure. All the samples were tested in the laboratory using established procedures but this was preceded by testing of soil and paint in the field with a kit by the students. The total Pb concentration in 32 of the 159 soil samples that were collected exceeded 400 ppm, the EPA standard for bare soil in residential areas where children play. Only 4 of the 118 tap water samples that were collected contained over 15 ppb Pb, with the data showing that flushing for 2 min clearly lowered Pb concentration further across the board. The highest risk of child exposure may be posed by old Pb‐based paint, however, which was detected in 9 of the 48 samples that were tested. Residents were also the least willing to let the students test or sample their paint. High‐school students could help reduce exposure in the many towns where child blood‐Pb levels remain high today by identifying sources and, while doing so, learn about environmental science and measurement from this hands‐on experience.

Investigation of the effects of pretreatment on the elemental composition of ash derived from selected Nigerian lignocellulosic biomass

Lignocellulosic biomass is an important source of renewable energy and a potential replacement for fossil fuels. In this work, the X-ray fluorescence (XRF) method was used to analyze the elemental composition of raw and pretreated lignocellulosic biomass of cassava peels, corn cobs, rice husks, sugarcane bagasse, yam peels, and mixtures of cassava peels and yam peels, corn cobs and rice husks and all five biomass samples combined. The influence of particle size on elemental properties was investigated by screening the selected biomass into two size fractions, of an average of 300 and 435 µm, respectively. The total concentration of Mg, Al, Si, P, S, Cl, Ca, Ti, Cr, Mn, Fe, Co, Cu, Zn, Sn, Ni, Br, Mo, Ba, Hg, and Pb were determined for each of the biomass samples before and after the different pretreatments adopted in this study. From the results of the analysis, there was a significant reduction in the concentration of calcium in all the analyzed biomass after the alkaline pretreatment with rice husks biomass having the lowest concentration of 66 ppm after the alkaline pretreatment. The sulfur content of the acid pretreated biomass increased considerably which is likely due to the sulfuric acid used for the acid pretreatment. The fact that a mixture of biomass feedstock affects the properties of the biomass after pretreatment was validated in the mixed biomass of cassava peels and yam peels biomass as an example. The concentration of Mg in the mixed biomass was 1441 ppm but was 200 ppm and 353 ppm in individual cassava peels and yam peels respectively. The results of this study demonstrated that pretreated mixtures of biomass have varied elemental compositions, which could be an important factor affecting downstream processes, especially if a hybrid feedstock is used in a large-scale application.

Legacy of anthropogenic lead in urban soils: Co-occurrence with metal(loids) and fallout radionuclides, isotopic fingerprinting, and in vitro bioaccessibility

Anthropogenic lead (Pb) in soils poses risks to human health, particularly to the neuropsychological development of exposed children. Delineating the sources and potential bioavailability of soil Pb, as well as its relationship with other contaminants is critical in mitigating potential human exposure. Here, we present an integrative geochemical analysis of total elemental concentrations, radionuclides of 137Cs and 210Pb, Pb isotopic compositions, and in vitro bioaccessibility of Pb in surface soils sampled from different locations near Durham, North Carolina. Elevated Pb (>400 mg/kg) was commonly observed in soils from urban areas (i.e., near residential house foundation and along urban streets), which co-occurred with other potentially toxic metal(loids) such as Zn, Cd, and Sb. In contrast, soils from city parks and suburban areas had systematically lower concentrations of metal(loids) that were comparable to geological background. The activities of 137Cs and excess 210Pb, coupled with their correlations with Pb and co-occurring metal(loids) were used to indicate the persistence and remobilization of historical atmospherically deposited contaminants. Coupled with total Pb concentrations, the soil Pb isotopic compositions further indicated that house foundation soils had significant input of legacy lead-based paint (mean = 1.1895 and 2.0618 for 206Pb/207Pb and 208Pb/206Pb, respectively), whereas urban streetside soils exhibited a clear mixed origin, dominantly of legacy leaded gasoline (1.2034 and 2.0416) and atmospheric deposition (1.2004–1.2055 and 2.0484–2.0525). The in vitro bioaccessibility of Pb in contaminated urban soils furthermore revealed that more than half of Pb in the contaminated soils was potentially bioavailable, whose Pb isotope ratios were identical to that of bulk soils, demonstrating the utility of using Pb isotopes for tracking human exposure to anthropogenic Pb in soils and house dust. Overall, this study demonstrated a holistic assessment for comprehensively understanding anthropogenic Pb in urban soils, including its co-occurrence with other toxic contaminants, dominant sources, and potential bioavailability upon human exposure.