Kinds Of Heavy Metals Research Articles

Leaching Characteristics of Heavy Metals from Asphalt Mixture with Basic Oxygen Furnace Slag as Aggregate

Abstract Basic oxygen furnace (BOF) slag, which has good mechanical properties, can be recycled as pavement materials. However, BOF slag contains several kinds of heavy metals. Batch leaching tests are usually conducted to investigate the leaching characteristics of asphalt mixture with BOF slag, which has a few limitations. In this article, the leaching characteristics of heavy metals were investigated through the column leaching test device self-designed in the laboratory. The factors that influence the leaching of heavy metals were evaluated. The experimental results indicate that high-basicity BOF slag that has high content of free calcium oxide (f-CaO) can effectively inhibit the leaching of heavy metals from asphalt mixture. Copper and nickel have no leaching risk in neutral and weakly acidic conditions. However, zinc and lead in asphalt mixture with medium-basicity BOF slag have a risk of causing environmental implication in long-term leaching process. Moreover, covering of asphalt inhibits the leaching of f-CaO and hinders the contact between heavy metals and the leachant at the same time. The conclusions of this article provide a theoretical basis for the green application of BOF slag as an asphalt pavement material.

Graphite Recycling by Doping Nano-materials for Water Treatment

AbstractThis paper presents graphite recycling by doping nanosilver for water filtration because of the need for secure water for consumption. It has demonstrated the significance of looking for alternative materials that can filter water independently or in combination with other materials. Adsorbent nanomaterials have unique characteristics as compared to conventional ones due to their small size and significant surface area relative to volume ratio. In this study, an effort is made to test the usability of nanomaterials, such as graphite-doped nanosilver, as adsorbents for the elimination of different kinds of heavy metals from water. This study detects the elimination of metal ions from aqueous solutions by using modified graphite nanosheets. The shape of the synthesized graphite adsorbent nanosheet was characterized by spectroscopic analyses such as SEM and HR-TEM. The sizes of these nanocrystals are comparatively small, at about 38 nm for Ag and 56 nm for G–Ag samples, as shown by HR-TEM. The results showed that raising the duration of immersion and adsorbent quantity improved adsorption effectiveness. Chemical treatment frequently affects the surface characteristics of nanoadsorbents and considerably enhances their adsorption capacities. The metal-nanomaterial interactions, processes, and capacities of nanomaterial-based adsorption are analyzed and described in this work in a variety of experimental settings. The improved adsorbent graphite recycling showed a significant adsorption efficiency of 91.7% for heavy metals. It is vital to research ecologically friendly and sustainable applications that can lead to innovative and revolutionary water treatment systems.

A general strategy to enhance hydrogen peroxide generation via two-electron water oxidation by antimony modification for removal of triethyl phosphate and hexavalent chromium

Two-electron water oxidation has attracted more and more attention for H2O2 production. This strategy mainly uses water and does not require bubbling of oxygen gas, which can be widely used in oxygen-deficient environments. Currently, the most important research for two-electron water oxidation is the design of high-efficiency anode materials. Herein, a general method is developed to enhance the activity of two-electron water oxidation for H2O2 production via Sb2O3 modification. This strategy is suitable for a series of electrodes, including carbon fiber paper, graphite plate, WO3, CuWO4 and WO3&CuWO4 composite. The mechanism for Sb2O3 modification toward enhanced H2O2 generation is clearly demonstrated. It should be due to three factors: 1) enhance the reaction kinetic, 2) enlarge the specific surface area and 3) suppress H2O2 decomposition. According to density function calculation, it is firstly found that the Sb optimizes the Gibbs free energy of adsorbed *OH intermediate of its nearby atom, making its adjacent atom (such as W) the active site. Finally, these Sb-modified electrodes are firstly used to produce H2O2 for high-efficiency removal of triethyl phosphate, an environmental pollutant that are difficult to be degraded. It can also be used for the removal of hexavalent chromium, one kind of heavy metal.

The genotoxicity impact of heavy metals on the Escherichia coli

ABSTRACT In present work, the genotoxicity of Hg2+, Ag+, Cr6+, Ni2+, Pb2+, Co2+, Mn2+, Zn2+, and Cr3+ was investigated via a quantitative toxicogenomics assay, to understand the toxic mechanism of heavy metals with greater depth. Under the experimental conditions, Hg2+, Ag+, and Cr6+ showed a more serious toxic impact on the expression of functional genes (eg., oxyR, katG, grxA, osmE, emrE, dinG) than Ni2+, Pb2+, Co2+, Mn2+, Zn2+, and Cr3+, while the protein, oxidative, and membrane stress response pathways were more sensitive to the toxicity of Hg2+, Ag+, and Cr6+ than the DNA and general stress response pathways. Compared with the other kinds of heavy metals, Ni2+, Pb2+, Co2+, and Mn2+ altered the expression of functional genes (uvrY, recX, mutY, and sbmC) related to the DNA stress response pathways more seriously, while Zn2+ and Cr3+ changed the expression of the functional genes (yfjG, ydgL, ssrA, and osmC) associated with the general stress response pathway more significantly. Meanwhile, the toxicity of Ni2+, Pb2+, Co2+, and Mn2+ was slightly higher than that of Zn2+ and Cr3+ in terms of the total value of transcriptional effect level Index (TELI) by detecting the promoter activities of different functional genes. In addition, to survive the toxicity of heavy metals, the expression of multidrug efflux genes (ydgL, cyoA, emrA, and emrE) and toxicity-resistant genes (Ion, dnaJ, clpB, mutY, dnaK, rpoD, sbmC) mainly functioned.

Enrichment characteristics and environmental risk assessment of heavy metals in municipal sludge pyrolysis biochar

Pyrolysis treatment of municipal sludge is a promising sludge treatment technology. However, due to the presence of heavy metals in sludge, the practical application of sludge pyrolysis products, especially biochar, is greatly affected. In this paper, the enrichment characteristics of different heavy metals in municipal sludge and its pyrolysis biochar and their leaching characteristics in the environment were studied. The environmental risks of municipal sludge and biochar were also assessed. The experimental results revealed that pyrolysis would promote the enrichment of different heavy metals in sludge in pyrolysis biochar. And with higher pyrolysis temperature, the enrichment is stronger. But for metals with high volatility such as Hg, Cd, Se, increasing the pyrolysis temperature will reduce their enrichment. Pyrolysis can inhibit the heavy metals in sludge leaching, and the effect of pyrolysis temperature on different kinds of heavy metals is different. The leaching rates of Se, As and Cr first increased and then decreased as the temperature of pyrolysis increased. The leaching rate of Cd increased as the temperature of pyrolysis increased. Considering the leaching rate of each heavy metal, the leaching toxicity of heavy metals in pyrolysis biochar is the lowest at the pyrolysis temperature of 400 °C. The risk assessment of municipal sludge and biochar revealed that the most harmful heavy metals in the original sludge were Hg, Cd and Se, followed by Cu and Zn. Sludge pyrolysis into biochar can reduce the content of Hg, Cd and Se. The use of copper and zinc water pipes should be reduced for sewage pipe laying to decrease the contents of Cu and Zn in municipal sludge.

Non-Negligible Ecological Risks of Urban Wetlands Caused by Cd and Hg on the Qinghai-Tibet Plateau, China.

The Huangshui National Wetland Park (HNWP) is a unique national wetland park in a city on the Qinghai-Tibetan Plateau, containing three zones: Haihu, Beichuan, and Ninghu. In this study, a total of 54 soil samples (18 sampling points with depths of 0-10 cm, 10-20 cm, and 20-30 cm) were collected in these three zones, and the contents of heavy metals (Cr, Cd, Cu, Hg, Ni, Pb, Zn, and As) of each sample were determined. The ecological risk of eight kinds of heavy metals was evaluated by using the geo-accumulation index (Igeo), and the ecological risk-controlling effect of the Xining urban wetlands on heavy metals was explored by comparative analysis, and the possible sources of heavy metals in the soil were analyzed via correlation analysis and principal component analysis (PCA). The results revealed that the total heavy metal concentration order was Haihu > Beichuan > Ninghu zone. As and Cu presented vertical accumulation characteristics in the surface and lower horizon, respectively. Cr, Cd, Hg, Ni, Pb, and Zn accumulated downwards along the depth. On the spatial scale, the enrichments of Cd and Hg brought non-negligible ecological risks in plateau urban wetlands. The results of PCA indicated that soil heavy metals mainly came from compound sources of domestic and atmospheric influences, traffic pollution sources, and industrial pollution sources. The study has revealed that human activities have inevitable negative impacts on wetland ecosystems, while the HNWP provides a significant weakening effect on heavy metal pollution.

Ball Mill, Humic Acid, and Rock Phosphate-Modified Conocarpus Biochar for Efficient Removal of Heavy Metals from Contaminated Water

An increasing trend of anthropogenic activities such as urbanization and industrialization has resulted in induction and accumulation of various kinds of heavy metals in the environment, which ultimately has disturbed the biogeochemical balance. Therefore, the present study was conducted to probe the efficiency of conocarpus (Conocarpus erectus L.) waste-derived biochar and its modified derivatives for the removal of lead (Pb), cadmium (Cd), copper (Cu), and zinc (Zn) from aqueous solutions. Biochar was produced at 600 °C and modified with humic acid (1:10 w/v ratio) and rock phosphate (0.5:1 w/w ratio). Additionally, produced biochar, as well as humic acid and rock phosphate-modified biochars, were subjected to ball milling separately. Equilibrium and kinetics batch experiments were conducted to investigate heavy metals adsorption on synthesized adsorbents. Adsorption isotherms and kinetics models were employed to explore the adsorption efficiency of produced materials for metals adsorption. Among all the applied adsorbents, ball-milled biochars showed comparatively higher adsorption compared to un-milled biochars. Humic acid and rock phosphate-modified milled biochar showed the highest adsorption capacity for Pb (18.85 mg g−1), while rock phosphate-modified milled biochar showed the highest adsorption capacity for Cu and Zn (24.02 mg g−1 and 187.14 mg g−1), and humic acid modified biochar adsorbed maximum Cd (30.89 mg g−1). Adsorption isotherm study confirmed Freundlich as the best-suited model (R2= 0.99), while kinetics adsorption was well described by the pseudo-second-order (R2 = 0.99). Hence, it was concluded that ball-milled biochar modified with humic acid and rock phosphate could potentially remove heavy metals from contaminated water.

Cadmium Absorption in Various Genotypes of Rice under Cadmium Stress.

Cadmium (Cd) is a kind of heavy metal. Cadmium pollution in paddy fields will accumulate a large amount of cadmium in rice, which will affect the growth and development of rice. In addition, long-term consumption of rice contaminated with Cd can harm human health. In this study, four rice varieties with high Cd accumulation (S4699, TLY619, JHY1586, QLY155) and four varieties with low Cd accumulation (YY4949, CYJ-7, G8YXSM, MXZ-2) were screened through field experiments for two consecutive years (2021 and 2022) and differences in antioxidant enzyme systems and expression of genes in their organs were analyzed. The total Cd content showed as follows: indica rice > japonica rice, high-Cd-accumulation variety > low-Cd-accumulation variety, and the total Cd content of each organ of rice showed root > stem > leaf > grain. The results of the antioxidant enzyme system showed that the contents of malondialdehyde (MAD), reduced glutathione (GSH), oxidized glutathione (GSSH), and peroxidase (POD) were positively correlated with the total Cd content in rice, and superoxide dismutase (SOD) showed the opposite performance in the leaves. There was no correlation between catalase (CAT) and Cd content, but CAT content decreased in leaves and grains and increased in roots and stems with increasing fertility. Based on this study, RT-qPCR was used to further validate the expression of Cd-uptake-related genes in different rice varieties. It was found that high expression of OsHMA3, OsCCX2, OsNRAMP5, and OsHMA9 genes promoted Cd uptake and translocation in rice, especially in rice varieties with high Cd accumulation. The high expression of OslRT1, OsPCR1, and OsMTP1 genes hindered Cd uptake by rice plants, which was especially evident in low-accumulating Cd rice varieties. These results provide an important theoretical reference and scientific basis for our in-depth study and understanding of the mechanism of cadmium stress tolerance in rice.

A novel flavonol-based fluorescent probe for rapid detection of Hg2+ and its multi-functional applications

Mercury is a kind of heavy metal with bioaccumulation and is extremely toxic. The analysis and detection of mercury ions (Hg2+) are of great significance for environmental and human health. Hence, in this paper, we synthesized a novel fluorescent probe (TO-PCBM) based on flavonol as the fluorophore and thiocarbonate as the reaction site for turn-on monitoring of Hg2+. The probe TO-PCBM can detect Hg2+ sensitively, and possesses the excellent features of low detection limit (3.25 × 10−8 M), large Stokes shift (200 nm) and fast detection response (within 2 min). The unique sensing mechanism was attributed to the deprotection of thiocarbonate induced by Hg2+, leading to the strongly excited state intramolecular proton transfer emission of MHPCB. The detection mechanism was fully validated through ESI-MS, TLC and DFT calculations. Because of its high sensitivity, the probe TO-PCBM has a high recovery rate for trace mercury ions in real environmental water samples. Meanwhile, due to its good biocompatibility and cell membrane permeability, the probe TO-PCBM can successfully monitor Hg2+ in fluorescence imaging of zebrafish and onion cells. Furthermore, the TO-PCBM-loaded test strip achieves simple and fast identification of Hg2+.

Cobalt chloride exposure disturbs spindle assembly and decreases mouse oocyte development potential

Cobalt is a kind of heavy metal which is widely used in petrochemical and biomedical industries. Animal studies have reported that cobalt would exert systemic toxicity, but its effects on the ovarian function in mammals, especially for oocyte quality remains unknown. In the present study, we report that cobalt chloride treatment affects ovary coefficient and follicular growth. Oocytes in cobalt chloride exposed mice exhibited a decreased development potential, with the evidence of decreased occurrence rate of germ vesicle breakdown and polar body extrusion. Besides, cobalt chloride disorganized meiotic spindle formation and movement, mechanically associated with affecting TACC3 and Ac-a-tubulin levels, and disturbing actin reorganization. In addition, cobalt chloride exposure result in mitochondrial cristae structures disappear, cluster distribution and potential depolarization. Altogether, these findings suggest that cobalt chloride impairs the ovarian follicle growth and affects oocyte development by disrupted spindle assembly and mitochondrial function.

Source Analysis of Heavy Metal Pollution Using UNMIX and PMF Models in Soils along the Shuimo River in Urumqi, China.

Eight kinds of heavy metals in soil within 0-2 km from the banks of Shuimo River in Urumqi were analyzed by using an X-ray fluorescence spectrometer and national standard detection methods. Unmix and PMF models are comprehensively used to analyze potential pollutant sources and contribution rates. Soil samples are sampled in three layers of 0-20, 20-40, and 40-60 cm, and each group of sample points in each layer is 5 m, 1 km, and 2 km away from the riverbank, respectively. Only the average concentration of Mn in each layer of soil is lower than the background value, according to the analytical results, while the average concentration of other heavy metals surpasses the background value. The highest proportion of exceeding the background value is Ni in the 40-60 cm soil layer, up to 1.92 times. Unmix and PMF models are used to analyze pollutants' source quantity and contribution rate, respectively. The results show that the two models can identify two pollution sources at the three soil layers, and their contribution rates are similar, and each index of the analysis results of the two models is within the required range of model reliability. By comparing with the Pearson correlation coefficient and distribution map of heavy metal concentration in surface soil, it is concluded that Zn, Pb, Cr, and Cu are mainly from industrial sewage and air pollution from coal combustion, while As, Mn, Ni, and V are mainly from agricultural pollution and light industrial pollution. In future research, it is necessary to investigate the change of heavy metal concentration in detail from the time dimension to further quantitatively calculate the potential pollutant source and contribution rate.

Dual-Functional Nanostructures for Purification of Water in Severe Conditions from Heavy Metals and E. coli Bacteria

Because of industrial water, many groundwater sources and other water bodies have a strongly acidic medium. Increased bacterial resistance against multiple antibiotics is one of the main challenges for the scientific society, especially those commonly found in wastewater. Special requirements and materials are needed to work with these severe conditions and treat this kind of water. In this trend, nanolayered structures were prepared and modified in different ways to obtain an optimum material for removing different kinds of heavy metals from water in severe conditions, alongside purifying water from a Gram-negative bacteria (E. coli), which is an indication for fecal pollution. An ultrasonic technique effectively achieved this dual target by producing nanolayered structures looking like nanotapes with dimensions of 25 nm. The maximum removal percentages of the heavy metals studied (i.e., iron (Fe), copper (Cu), chromium (Cr), nickel (Ni), and manganese (Mn)) were 85%, 79%, 68%, 63%, and 61%, respectively for one prepared structure. In addition, this nanostructure showed higher antimicrobial activity against the most common coliform bacterium, E. coli (inhibition zone up to 18.5 mm). This study introduces dual-functional material for removing different kinds of heavy metals from water in severe conditions and for treating wastewater for Gram-negative bacteria (E. coli).

Fabrication of Effective Nanohybrids Based on Organic Species, Polyvinyl Alcohol and Carbon Nanotubes in Addition to Nanolayers for Removing Heavy Metals from Water under Severe Conditions.

Industrial water has a dual problem because of its strong acidic characteristics and the presence of heavy metals. Removing heavy metals from water in these severe conditions has special requirements. For this problem, an economic method was used for removing iron (Fe), copper (Cu), chromium (Cr), nickel (Ni) and manganese (Mn) with extremely acidic characteristics from water. This method depends on the preparation of nanohybrids through host–guest interactions based on nanolayered structures, organic species (stearic acid), polyvinyl alcohol (PVA) and carbon nanotubes (CNTs). The formation of nanohybrids was confirmed using different techniques through the expansion of the interlayered spacing of the nanolayered structure from 0.76 nm to 1.60 nm, 1.40 nm and 1.06 nm. This nano-spacing is suitable for trapping and confining the different kinds of heavy metal. The experimental results indicated that the prepared nanohybrid was more effective than GreensandPlus, which is used on the market for purifying water. The high activity of the nanohybrid is obvious in the removal of both copper and nickel because the GreensandPlus was completely inactive for these heavy metals under severe conditions. Finally, these experimental results introduce new promising materials for purifying industrial water that can work under severe conditions.

Adsorption capacity of bio-char prepared from the pyrolysis of hazelnut shells at different temperatures

Abstract Biomass pyrolysis to produce bio-char is one of the scientific and effective means of utilizing biomass resources. Differ from previous studies, this paper explored the effect of pyrolysis temperature (400–1000 °C) on the adsorption capacity of hazelnut shell bio-char from two perspectives, including physical macroscopic structure and functional group microscopic adsorption, and the practical adsorption application tests on common 7 kinds of heavy metals in polluted water were further carried out. The results showed that the yield and adsorption of bio-char prepared at different pyrolysis temperatures varied significantly, as the temperature increased, bio-char yield and surface acid functional group content decreased, the adsorption rate on most of heavy metals increased firstly and then decreased (except for Cr6+), the adsorption capacity of bio-char prepared at above 600 °C was mainly affected by physical macroscopic structure, and at 800 °C, bio-char had a large number of pore structures, and pore structure has been fully developed, iodine adsorption value and BET specific surface area were 595.36 mg/g and 197.32 mg/m2, respectively, the adsorption effect of bio-char on Cr6+, Cd2+, Zn2+, Cu2+ and Ni2+ were best, and the adsorption rates were 45.23%, 44.14%, 60.11%, 61.28% and 65.07% respectively. It revealed that although the absorption effect of bio-chars prepared at different temperatures on different heavy metals had a great variation, large specific surface area and developed pore structure still played important role in the adsorption capacity of bio-char. These provided a reference for the application of hazelnut shell bio-char based on adsorption properties, especially absorbing heavy metals in polluted water.

Optimization of the raw materials of biochars for the adsorption of heavy metal ions from aqueous solution.

In this paper, the material types were preferentially selected for different kinds of heavy metals, the effect of calcination temperatures on metal adsorption was investigated, and the adsorption mechanism was explored and summarized. The results show that the pseudo-first-order kinetic was better to fit the adsorption of heavy metals. The biomass type and pyrolysis temperature had an effect on the rate at which heavy metals were absorbed. Based on their adsorbed capacity, 350 °C pyrolyzed corn stalk char, 550 °C pyrolyzed peanut shell char, 450 °C pyrolyzed peanut shell char, 450 °C pyrolyzed peanut shell char, and 500 °C pyrolyzed wheat stalk char were shown to be the best adsorbents for Cr2O72-, Cd2+, Cu2+, Zn2+ and Pb2+, respectively. The largest adsorption rate were in the order of Cr6+ (Cr2O72-, 0.5380 /min) > Pb2+ (0.2276 /min) > Cd2+ (0.1354 /min) > Cu2+ (0.1273 /min) > Zn2+ (0.1000 /min), which might be positively related to the ion radius. Meanwhile, the yield of biomass decreased from 43.9% to 29.0% with the increase of pyrolysis temperature from 350 °C to 550 °C. In addition, the specific surface area and functional groups of the biochar, as well as the ionic radius and initial concentration of heavy metals affect the adsorption rate.

Distribution, Genesis, and Human Health Risks of Groundwater Heavy Metals Impacted by the Typical Setting of Songnen Plain of NE China.

Heavy metals pollution in groundwater and the resulting health risks have always been an environmental research hotspot. However, the available information regarding this topic and associated methods is still limited. This study collected 98 groundwater samples from a typical agricultural area of Songnen Plain in different seasons. The pollution status and sources of ten heavy metals (As, Ba, Cd, Co, Cr (VI), Cu, Fe, Mn, Ni, Pb, and Zn) were then analyzed and compared. In addition, the human health risks assessment (HHRA) model was used to calculate human health risks caused by heavy metals in groundwater. The results revealed that heavy metals were mainly distributed in the northwest of the study area and along the upper reaches of the Lalin river and that the concentrations of heavy metals were higher during the wet season than the dry season. Industrial and agricultural activities and natural leaching are the main sources, and each kind of heavy metal may have different sources. Fe and Mn are the primary pollutants, mainly caused by the native environment and agricultural activities. The exceeding standard rates are 71.74% and 61.54%, respectively based on the Class III of Quality Standard for Groundwater of China (GB/T 14848-2017). The maximum exceeding multiple are 91.45 and 32.05, respectively. The health risks of heavy metals borne by different groups of people were as follows: child > elder > young > adult. Carcinogenic heavy metals contribute to the main risks, and the largest risks sources are Cr and As. Therefore, the government should appropriately restrict the use of pesticides and fertilizers, strictly manage the discharge of enterprises, and control man-made heavy metals from the source. In addition, centralized water supply and treatment facilities shall be established to prevent the harm of native heavy metals.

EFFICIENT REMOVAL OF HEAVY METALS BY PHYTOREMEDIATION TECHNIQUES

Direct and indirect disposal of different wastes either due to some accidental spillage or due to practicing of sewage sludge to agricultural fields for diverse reasons in the water reservoirs contributes towards contamination of our ecosystem. Physical removal or immobilization is required for making soil and water contaminant-free from such kind of heavy metals. The Earth crust is mainly composed of these heavy metals and as they are non-degradable in nature, so there is a greater risk of their entrance into the food web and lead to various health hazards. Phytoremediation is an innovative, environment friendly, cost-effective, and aesthetically pleasing approach to remove/immobilize heavy metals. Processes mainly involves the detoxification, removal, or stabilization of retentive pollutants via utilization of vegetation and is a green environmental-friendly tool for cleaning polluted soils. It is a broad-spectrum remediation mechanism in which several processes are involved as mentioned here includes phyto-stabilization, rhizo-filtration, rhizo-degradation, phyto-degradation, phyto-extraction, and phyto-volatilization. Use of aromatic non-edible plants is sustainable and the best treatment approach for the elimination of toxic metals. These plants are not removed directly by humans or animals like non-aromatic edible crops such as cereals, pulses, or vegetables. This research is entirely based on qualitative analysis with descriptive approach. The crops like mustard plant, sunflower, rapeseed etc. are effectively put in an application at sites with superficial contamination of organic or inorganic contaminants via the above-mentioned six techniques. Phytoremediation is a reliable reclaiming treatment and hence the most demanding remediation technology in the world.

Comparative Study on the Determination of heavy metals in Soil by XRF and ICP-MS

The contents of Cr, Ni, Cu, Zn, As, Pb and Cd in standard soil for composition (GBW07403) and two soil samples were determined by XRF and ICP-MS, respectively. The results showed that XRF had higher precision than ICP-MS in the determination of seven metals in standard soil, but the relative errors of Ni, As and Cd were larger, up to -33%~22.7%. XRF and ICP-MS were used to determine contents of seven kinds of heavy metals in 2 soil samples, respectively. Both methods had high precision. F test showed that there was no significant difference in precision between the two methods except for Cd in No.2 soil. The t test showed that there were significant differences by the two methods for the determination of other heavy metals except for Cd and Cu (P ≤0.05). Although the method of XRF was fast and simple, its accuracy and comparison with other experimental methods need to be further studied due to the sample matrix effect.

Health risks of PM2.5-bound polycyclic aromatic hydrocarbon (PAH) and heavy metals (PPAH&HM) during the replacement of central heating with urban natural gas in Tianjin, China.

To investigate the health effects of fine particulate matter (≤ 2.5μm in aerodynamic diameter; PM2.5)-bound heavy metals and polycyclic aromatic hydrocarbons (PAHs) before and after the implementation of the Urban Natural Gas Heating Project (UNGHP), the lifetime cancer risks, hazard quotients (HQs) of heavy metals and PAHs were calculated. Seven kinds of heavy metals (Al, As, Cd, Cr, Mn, Ni and Se) and 12 kinds of PAHs including acenaphthylene (ANY), acenaphthene (ANA), fluoranthene (FLT), pyrene (PYR), chrysene (CHR), benz[a]anthracene (BaA), benzo[b]fluoranthene (BbF), benzo[k]fluoranthene (BkF), benzo[a]pyrene (BaP), dibenz[a,h]anthracene (DBA), benzo[ghi]perylene (BPE) and indeno[1,2,3-cd]pyrene (IPY) were analyzed and used for the health risk assessments. It was found that HQ of Mn fell from 1.09 in the coal-burning period to 0.72 in the gas-burning period in the suburban area. And lifetime cancer risks of PAHs fell from 35.7 × 10-6 in the coal-burning period to 17.22 × 10-6 in the gas-burning period in the urban area. It could be concluded that, during the gas-burning period, downward trends were observed for the lifetime cancer risks and HQs of most kinds of heavy metals and PAHs in all regions of Tianjin compared to those during the coal-burning period. The UNGHP was effective, and we should also take other measures to control the pollution.

The Interactions Between Antibiotic Resistance Genes and Heavy Metal Pollution Under Co-Selective Pressure Influenced the Bio-Enzyme Activity.

The spread of antibiotic resistance genes (ARGs) has brought potential risks to public health. However, the interactions between heavy metals and ARGs, as well as their potential effect on bio-enzyme activity under the pressure of co-selectivity in soil still remain poorly understood. In this work, the distribution characteristics and the co-selective relationship of 28 ARGs and eight heavy metals in soil in a dairy farm were visualized via the geographic information system (GIS) technique. Eight kinds of heavy metals were detected by an atomic fluorescence spectrometer and atomic absorption spectrophotometer, which were further evaluated via the single factor pollution index value. The GIS analysis showed that arsenic (As) was the key element responsible for soil pollution, which was found to be positively related to soil depths. The top three comprehensive scores of ARGs ranked the orders of sul2 > tetX > blaTEM, indicating the high potential of risk caused by these genes in the soil environment. In addition, the functional predications performed with the 16 SrDNA sequencing data based on the KEGG database indicated that the sulfonamides in soil involved multiple pathways, especially the metabolism, transport and catabolism, and membrane transport processes. This suggested that most bio-enzymes were found to be expressed in low activities in different pathways. Significant correlations were observed between the heavy metals and ARGs (p < 0.05), particularly between the ARGs and As, Cu, Ni, Pb, and Zn (p < 0.01). This study offers deep insights into the potential interactions between heavy metals and ARGs in soil and provides guidance for the fabrication of enzyme-based smart materials for soil remediation in dairy farms.