Rate Of Cd Research Articles

Geochemical relationship and profile distribution of Selenium and Cadmium in typical Selenium-enriched areas in Enshi

Selenium (Se) is an essential nutrient element for humans, and Se-enriched products are gaining popularity due to their health benefits. However, Enshi, a region in China naturally rich in Se, a high background value of cadmium (Cd) is discovered, which severely impacts local Se-enriched agriculture. Therefore, it is crucial to explore the geochemical relationship between Se and Cd. In this study, we analyzed soil profiles and parent rocks of different geological ages from Enshi to investigate the accumulation and distribution of Se and Cd. The ratio of redox sensitive elements and the multivariate statistical analysis, along with XRD and XPS analysis, were utilized to investigate the correlated relationship between Se and Cd and the underlying geochemical mechanisms. The results showed that average Se and Cd contents in rocks were 1.67 and 0.32 mg/kg. Se and Cd levels reached highest at Permian in rocks of different geological ages, which may be related to the Permian Dongwu movement near the study area. The highest migration rate of Cd and Se from rock to soil was 12 and 1.5 times. The soil Se and Cd fractions were mostly in bound states, with the largest fraction of Se being organic-bound at an average of 45.9%. The reducible and the residue state accounted for the largest proportion in the Cd fractions, with an average of 40.6% and 25.6%. Redox-sensitive element ratios indicate a reducing forming environment of deep sediments in the Permian strata. Furthermore, the correlation and PCA analysis revealed highly significant positive correlations between Se, Cd, V and Cr, suggesting that the sources of Se and Cd were closely related to volcanic and biological activities. In conclusion, a strong geochemical relationship was observed between Se and Cd. And as a result, metal pollution must be closely monitored during the production of Se-enriched agriculture in Se-enriched regions.

Study of the pedological quality of an overexploited soil and the operating constraints: Case of market gardening sites from Kimuenza to Kinshasa

The study aims at assessing the quality of the market garden soil of Kimuenza and the constraints faced with its productivity. The analysis was carried out on the one hand, by Hach UV-visible spectroscopy based on the beer-Lambert law, for the physicochemical parameters, by X-ray fluorescence for the saturation elements and on the other hand, by ICP- MS for metallic trace elements. The detection limit and the reproducibility of these methods have been confirmed. The obtained indicated that the soil is poor in nutrients necessary for plants, low water retention and a sandy texture and has a high rate of Cd varying between 9.6 to 12.1 mg/Kg in all sites.

Source Analysis of Heavy Metals in Typical Farmland Soils Based on PCA-APCS-MLR and Geostatistics

Human activities often increase the content of heavy metals in surface soils, thus affecting the precise quantification and evaluation of heavy metals in regional soils. In order to systematically study the spatial distribution characteristics and contribution rate of heavy metal pollution sources in typical farmland soil around stone coal mines in western Zhejiang Province, heavy metals such as Cd, Hg, As, Cu, Zn, and Ni in topsoil samples of arable land and agricultural products were collected and analyzed, with an emphasis on the geochemical characteristics of each element and ecological risk assessment of agricultural products. Correlation analysis, principal component analysis (PCA), and the absolute principal component score-multiple linear regression receptor model (APCS-MLR) were used to discuss the source and source contribution rate of soil heavy metal pollution in this area. Meanwhile, the spatial distribution characteristics of the contribution rate of Cd and As pollution sources of the soil in the study area were also expounded in detail by the geostatistical analysis method. The results showed that the contents of six heavy metal elements including Cd, Hg, As, Cu, Zn, and Ni in the study area all exceeded the risk screening value. Among them, two elements exceeded the risk control value, Cd and As, and the point-exceeding rates were 36.11% and 0.69%, respectively. The Cd in agricultural products was also seriously exceeded. According to the analysis, there were two main sources of heavy metal pollution in the soil in the study area. Source one (Cd, Cu, Zn, and Ni) was coming from mining activities and natural sources, and the contribution rates to Cd, Cu, Zn, and Ni were 78.53%, 84.41%, 87%, and 89.13%. Source two (Hg and As) was mainly an industrial source, and the contribution rates to As and Hg were 82.41% and 83.22%, respectively. Cd was the heavy metal with the greatest pollution risk in the study area, and measures should be taken to reduce the pollution risk. There was an abandoned stone coal mine rich in elements such as Cd, Cu, Zn, and Ni. Located in the northeastern part of the study area under the action of atmospheric deposition, the confluence of mine wastewater into irrigation water and farmland sediment was one of the important factors for forming the source of farmland pollution. The settled fly ash was the main pollution source of As and Hg, which was also closely related to agricultural production. The above research can provide technical support for the precise implementation of ecological and environmental management policies.

Single and Binary Removals of Pb(II) and Cd(II) with Chemically Modified Opuntia ficus indica Cladodes.

In this study, cladodes of Opuntia ficus indica (OFIC), chemically modified with NaOH (OFICM), have been prepared, characterized, and tested as an effective biomass to remove Pb(II) and/or Cd(II) from aqueous media. At an optimum pH of 4.5, the adsorption capacity, qe, of treated OFICM was almost four times higher than that of untreated OFIC. The maximum adsorption capacities (qmax) in the single removal of Pb(II) and Cd(II) were 116.8 and 64.7 mg g-1, respectively. These values were 12.1% and 70.6% higher than those for the corresponding qmax in binary removal, which indicates the strong inhibitive effect of Pb(II) on the co-cation Cd(II) in a binary system. Structural and morphological characterization have been carried out by FTIR, SEM/EDX, and point of zero charge (pHPZC) measurements. The SEM/EDX results confirmed that the metals are adsorbed on the surface. The presence of C-O, C=O, and COO- functional groups were identified by FTIR on both OFIC and OFICM surfaces. On the other hand, we found that the adsorption processes followed the pseudo-second-order kinetics for both single and binary systems, with a fast biosorption rate of Pb(II) and Cd(II). The equilibrium data (adsorption isotherms) were better described by Langmuir and modified-Langmuir models for single and binary systems, respectively. A good regeneration of OFICM was obtained with an eluent of 0.1 M HNO3. Therefore, OFICM can be efficiently reused to remove Pb or Cd, up to three times.

Unveiling the migration of Cr and Cd to biochar from pyrolysis of manure and sludge using machine learning

Heavy metal (HM) in biochar derived from pyrolysis of sludge or manure is the main issue for its large-scale application in soils for carbon sequestration. However, there is a paucity of efficient approaches to predict and comprehend the HM migration during pyrolysis for preparing low HM-contained biochar. Herein, the data on the feedstock information (FI), additive, total concentration of feedstock (FTC) of HM (i.e., Cr and Cd), and pyrolysis condition, were extracted from the literature, to predict total concentration (TC) and retention rate (RR) of Cr and Cd in sludge/manure biochar using machine learning for mapping their migration during pyrolysis. Two datasets for Cr and Cd were compiled with 388 and 292 data points from 48 and 37 peer-review papers. The results indicated that the TC and RR of Cr and Cd could be predicted by the Random Forest model with test R2 of 0.74–0.98. Their TC and RR in biochar were dominated by the FTC and FI, respectively; while pyrolysis temperature was the most important to Cd RR. Moreover, potassium-based inorganic additives decreased the TC and RR of Cr while increased those of Cd. The predictive models and insights provided by this work could aid the understanding of HM migration during manure and sludge pyrolysis and guide the preparation of low HM-contained biochar.

Sorption and mobility of cadmium in soil impacted by irrigation waters

Soil contamination by Cd has drawn global attention, while how irrigation waters modulate Cd sorption and mobility in soil remains obscure. We address this by investigating how cropped sandy soil irrigated with different waters altered Cd sorption and mobility using a rhizobox experiment followed by a batch experiment. Maize were planted in the rhizoboxes and irrigated by reclaimed water (RW), livestock wastewater (LW) and deionized water (CK), respectively. The bulk soil sampled from each treatment after 60 days of growth was employed to measure the Cd sorption and mobility using the isothermal adsorption and desorption experiments. The results showed that, in a small rhizobox experiment, the adsorption rate of Cd by the bulk soil in the adsorption phase was much faster than the desorption rate in desorption phase. Irrigation with RW and LW both reduced the Cd adsorption capacity of soil, and the reducing degree brought by LW was more obvious. Cd desorption rate was very low but keep increasing in the desorption stage, and pre-RW irrigation had the potential to increase Cd desorption from soil. Although the results were obtained based on the bulk soil sampled from a rhizobox experiment, our study strongly suggests that the altered Cd adsorption and desorption behavior in the soil caused by the RW and LW irrigation may risk the farmland ecosystem and deserve more concern.

Reconstruction of Metal Ions Extracted from Coal Gangue to Synthesize Cost-effective Adsorbent for Highly Efficient Removal of Pollutants.

An emerging "one stone, three birds" strategy was proposed to realize the value-added disposal of solid waste coal gangue (CG), the synthesis of superb adsorbent and the efficient decontamination of pollutants (i. e., dyes, heavy metals). In this process, the metal ions extrated from calcined coal gangue (CCG) was reconstituted by a one-step hydrothermal process to yield porous polymetallic silicate adsorbent (named HECCGA8h). The adsorbent has a high adsorption capacity of 270.27 and 185.53 mg/g for methylene blue (MB) and Cd(II), respectively. In the actual waters, the removal rate of MB by this adsorbent reaches 99.8% (in Yangtze River water) and 99.42% (in Seawater), and the removal rate of Cd(II) reaches 99.11% (in Yangtze River water) and 92.52% (in Seawater), respectively. Thermokinetic analysis showed that the adsorption of MB by HECCGA8h is spontaneous and endothermic with increased entropy, and the adsorption of Cd(II) is spontaneous and exothermic. The adsorption of MB is mainly driven by synergism of hydrogen bond, electrostatic attraction and ion exchange, and the adsorption of Cd(II) is mainly driven by the complexation and ion exchange between the surface group of the adsorbent and Cd(II). This research provides a new way for the realization of "treating waste with waste".

A Systematic Review of Inflammatory Bowel Disease Epidemiology and Health Outcomes in Sexual and Gender Minority Individuals

A Systematic Review of Inflammatory Bowel Disease Epidemiology and Health Outcomes in Sexual and Gender Minority Individuals

Aminated Polyacrylonitrile Nanofiber Membrane for Effective In Situ Bivalent Cadmium Contaminated Kaolin Remediation

AbstractCadmium is a harmful pollutant in soil. Here, an aminated polyacrylonitrile (PAN) nanofiber membrane is obtained by electrospinning and amination modification for effective in situ remediation of bivalent cadmium (Cd(II)) contaminated kaolin. The aminated PAN (APAN) nanofiber membrane has the potential to be used as permeable reactive barrier (PRB) combined with electrokinetics (EK) for the remediation of potentially toxic metal contaminated soil. Morphology and chemical characterizations of the nanofibers are analyzed by scanning electron microscopy and attenuated total reflectance Fourier transform infrared spectroscopy. The maximal adsorption capacities of Cd(II) on APAN nanofiber membrane, as calculated from the Langmuir model, are 51.8 mg g−1. In addition, the obtained APAN nanofiber membrane can also be facilely regenerated through the adsorption/desorption experiments (5 cycles). The APAN‐15 nanofiber membrane is used for the remediation of Cd(II) contaminated kaolin. The pH, water content, conductivity, and Cd(II) concentration of kaolin are detected after EK process. These results show that the APAN‐15 nanofiber membrane works as adsorption medium and can accelerate the migration rate of Cd(II) in kaolin, stabilize the pH, and water content. The APAN nanofiber membrane as PRB material can remove Cd(II) in soil effectively and remediate the soil via the EK/APAN process.

Independent and combined effects of sepiolite and palygorskite on humus spectral properties and heavy metal bioavailability during chicken manure composting

The effects of the independent and combined addition strategies of sepiolite and palygorskite on humification and heavy metals (HMs) during chicken manure composting were evaluated. Results showed that clay mineral addition showed a favorable effect on composting, prolonged the duration of the thermophilic phase (5–9 d) and improved the TN content (14%–38%) compared to CK. Independent strategy enhanced the humification degree in equal measures with the combined strategy. Carbon nuclear magnetic resonance spectroscopy (13C NMR) and fourier transform infrared spectroscopy (FTIR) confirmed that aromatic carbon species increased by 31%–33% during composting process. Excitation–emission matrix (EEM) fluorescence spectroscopy showed that humic acid–like compounds increased by 12%–15%. In addition, the maximum passivation rate of Cr, Mn, Cu, Zn, As, Cd, Pb and Ni were 51.35%, 35.98%, 30.39%, 32.46%, −87.02%, 36.61% and 27.62%, respectively. The independent addition of palygorskite exhibits the most potent effects for most HMs. Pearson correlation analysis indicated that pH and aromatic carbon were the key determinants of the HMs passivation. This study provided preliminary evidence and perspective of the application of clay minerals on the humification and safety of composting.

Adsorption capacity of Penicillium amphipolaria XK11 for cadmium and antimony

Heavy metal pollution is a global problem that affects both the environment and human health. Microorganisms play an important role in remediation. Most studies on the use of microorganisms for heavy metal remediation focus on single heavy metals. In this study, a strain of Penicillium amphipolaria, XK11 with high resistance to both antimony (Sb III) and cadmium (Cd II) was screened from the mineral slag. The strain also had a high phosphate solubilization capacity. The single-factor adsorption experiment results showed that the initial pH (pH0), adsorption time (T), and initial solution concentration (C0) all affected the adsorption of Sb and Cd by XK11. When the initial pH0 (Cd = 6, Sb = 4) and adsorption time (T = 7 d) were constant, XK11 achieved the maximum removal rate of Cd (45.6%) and Sb (34.6%). These results confirm that XK11 has potential as a biomaterial or remediation of Sb and Cd pollution.

Investigation of cadmium and nickel biosorption by Pseudomonas sp. via response surface methodology.

The environmental contamination of heavy metals has grown over the last several decades along with global industrialization and now constitutes a serious threat to human health. In this research, high cadmium (Cd) and nickel (Ni) resistant bacteria that were chosen for heavy metal biosorption were isolated from the Industries Factory in Sari, Mazandaran, Iran. Pseudomonas aeruginosa was recognized as the isolated bacterium based on its morphological, physiological, biochemical, antibiotic resistance testing, and 16S rRNA sequences. The bacteria had the highest concentrations of resistance to Cd (up to 1600ppm) and Ni, according to the Minimum Inhibition Concentration (MIC) test (up to 2000ppm). Single-factor studies in single and binary systems were used to examine the effects of temperature, contact duration, pH value, starting Cd and Ni concentration, and biomass dose on the Cd and Ni adsorption by P. aeruginosa. The Cd and Ni biosorption in binary solutions was optimized using the response surface methodology (RSM) based on Central Composite Design (CCD). The investigation revealed that at pH 7.0, 45°C, and 1.5 gL-1 biomass dose, the greatest biosorption efficiency for Cd and Ni was 92.43 percent and 88.45 percent, respectively. According to the adsorption of Cd and Ni in urban water, under these similarly extreme conditions, Cd adsorption drops to 54% and Ni to 60%. Analysis Potential functional groups involving interactions between cells and metal ions were identified using Fourier transform infrared spectroscopy (FTIR). Different compounds and heavy metal ions were found to have been adsorbed to the surface of the biosorbent by scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDS). It was determined that P. aeruginosa had a high rate of Cd and Ni adsorption and that variations in pH level had a greater impact than other parameters. The findings imply that P. aeruginosa biomass may be an effective, economical, and environmentally friendly method for removing Cd and Ni from contaminated settings. It also has a reasonable capacity for biosorption in both a natural environment and a laboratory environment.

Assessment of Heavy Metal Concentrations in Penang, Malaysia’s Wastewater Treatment Plants: A Wastewater-Based Epidemiology Approach

Heavy metals and trace metals are among the most prevalent contaminants in sewage. Depending on the concentration and frequency of exposure, certain heavy metals are toxic, carcinogenic, and hazardous to humans. In this study, copper (Cu), nickel (Ni), zinc (Zn), iron (Fe), and cadmium (Cd) levels were measured in the collected wastewater samples from 10 selected domestic sewage treatment plants (STPs) in Penang, Malaysia in December 2021. All metals in the wastewater were determined using the atomic absorption spectrometric (AAS) method followed by the wastewater-based epidemiology (WBE) analysis. The mean concentrations of heavy metals in the wastewater samples were found to be in the following order (unit of mg/L): Fe > Ni > Zn > Cu > Cd (influent), and Fe > Ni > Zn > Cd > Cu (effluent). Among the metals, Fe concentrations were found to be the highest in effluent, with average values at 5.93 ± 5.319 mg/L, slightly over than a maximum permissible Fe concentration. Cadmium level in all STPs was significantly higher when compared to the maximum permissible Cd concentration (0.02 mg/L) allowed by Malaysia’s regulation, with an average of 0.13 ± 0.011 mg/L. Other metals concentration such as Cu, Ni and Zn in wastewater at the studied STPs showed low level and were considered safe. Using the WBE approach, the collected data were then calculated to estimate the population’s exposure consumption to heavy metals. Mass loading demonstrated high Fe exposure in all STPs but low Cd exposure, with the mean exposure of 1,924.86 ± 2451.772 and 46.91 ± 20.936 mg/1000p/d, respectively. Given the World Health Organization’s recommendation for tolerable weekly cadmium intake, the estimated human exposure to Cd in this study was particularly concerning, in addition to the lack of efficiency of Cd removal in the studied STPs. HIGHLIGHTS The order of the heavy metal mean concentrations in wastewater samples was Fe > Ni > Zn > Cu > Cd (influent), and Fe > Ni > Zn > Cd > Cu (effluent) The removal efficiency of the STPs followed the order: Cu > Fe > Zn > Cd > Ni The daily exposure rate of Fe was recorded as the highest exposure rate among other studied heavy metals (1924.7 ± 2451.772 mg/1000p/d) The daily exposure rate of Cd, estimated from the mass loads of total Cd, was found to be the lowest when compared to the other heavy metals (46.91 ± 20.936 mg/1000p/d) GRAPHICAL ABSTRACT

Process parameters and biological mechanism of efficient removal of Cd(II) ion from wastewater by a novel Bacillus subtilis TR1

The safe treatment of heavy metals in wastewater is directly related to the human health and social development. In this paper, a new biological strain has been isolated from electroplating wastewater, which can effectively remove metal ions in wastewater. The results of 16 S rDNA sequencing analysis and NCBI GenBank database comparison show that the strain belongs to a novel Bacillus genus and names Bacillus subtilis TR1 with the accession number of OL441606. The removal rate of Cd(II) reaches to 85.68% with the conditions of pH = 7, C0Cd(II) = 20 mg L−1, t = 48 h, m = 0.1 g, and T = 35 °C. The biological removal mechanism of Cd(II) is in-depth studied by FTIR and XRD combined with third-generation sequencing. The results indicate that Bacillus subtilis TR1 removes Cd(II) mainly through two synergistic pathways, namely, extracellular chemisorption and intracellular bioaccumulation: 1) The groups carried on the surface of the strain, such as –COOH, –NH, –OH and C–H, have good chemisorption properties for Cd(II) and easily form cadmium containing chelation (–COO–Cd(II), -N-Cd(II), etc.) with these groups. The appearance of TR1 strain changes from cylindrical to spherical after Cd(II) adsorption, which is due to the biotoxicity of Cd(II); 2) Cd(II) exchanges on the surface of TR1 strain with K and Na ions released from the intracellular cytoplasm and enters the cytoplasm under the transfer of biological transport medium. This part of Cd(II) is converted into its own components by anabolic enzymes and accumulates in the cytoplasm. These data provide a new biological agent for the efficient treatment of heavy metal ions in wastewater and enrich relevant theoretical knowledge.

Accumulation Characteristics and Health Risk Assessment of Heavy Metals in Soil-Crop System Based on Soil Parent Material Zoning

This study used both the element occurrence form analysis and the chronic health risk assessment method to investigate the accumulation characteristics of heavy metals in the soil-crop system and the health risk assessment of agricultural products in northeastern Yunnan, which is a typical area of Southwest China where heavy metals are enriched in soil. Based on the study of 1137 groups of agricultural products and corresponding root soils, the results showed that the soil cadmium (Cd) and lead (Pb) in the lead-zinc ore concentration area were higher than the risk-intervention values of the "Soil Environmental Quality Risk control standard for soil contamination of agricultural land" (GB 15618-2018), whereas the soil Cd in the other parent material areas was within the screening-intervention buffer zone, and Pb was below the minimum risk-screening value. According to the National Food Safety Standard of China (GB 2762-2017), the heavy metal Cd in potatoes and soybeans in the area seriously exceeded the standard, the heavy metal Pb in tartary buckwheat and walnut exceeded the limit value, and the exceeding rate of heavy metal Cd in crops from these parent material areas showed: clastic rock>basalt>lead-zinc ore>carbonate ≈ Quaternary sedimentary>sand (mud) rock. According to the U.S. Environmental Protection Agency's assessment method for the chronic health risk of heavy metal intake by humans, the grains and potatoes, staple foods, and fruits had low chronic health risks of heavy metal intake. Agricultural products from the parent material area of clastic rock, sand (mud) rock, Quaternary sedimentary, and lead-zinc ore concentration showed health risks; with the change in soil physical and chemical properties and the increase in the types of edible crops, the risk will gradually increase. Based on this research, it is urgent to carry out real-time monitoring of agricultural products in the area.

Performance and mechanisms for Cd(II) and As(III) simultaneous adsorption by goethite-loaded montmorillonite in aqueous solution and soil

A series of goethite-modified montmorillonite (GMt) materials was synthesized for the amelioration of cationic cadmium (Cd) and anionic arsenic (As) complex contaminants in soil and water bodies. The results showed that goethite (Gt) was successfully loaded onto the surface of montmorillonite (Mt), which possessed more functional groups (such as Fe–O, and Fe–OH) and a larger specific surface area. GMt-0.5 (Mt loaded with Gt at a ratio of 0.5:1) showed the highest adsorption capacity for Cd(II) and As(III) with the maximum of 50.61 mg/g and 57.58 mg/g, respectively. The removal rate of Cd(II) was highly pH dependent, while the removal rate of As(III) showed little dependence on pH. The goethite on montmorillonite might contribute to the formation of surface complexes with As(III) and oxidation of As(III) to As(V). In the binary system, both, synergistic and competitive adsorption existed simultaneously. Importantly, in the binary system, the removal of As(III) was more favorable because of the electrostatic interaction, formation of a ternary complex, and co-precipitation. In addition, the amendment of GMt-0.5 significantly reduced the availability of Cd and As in the soil. This study suggests that GMt-0.5 is a promising candidate for the simultaneous immobilization of metal (loid)s in both, aqueous solution and mine soil.

Experimental study on the redistribution law of heavy metals in sludge disintegration

Aiming at the problems of large output of excess sludge, difficulty in treatment and disposal, and the potential toxicity of heavy metals restricting its resource utilization, this paper studies the redistribution law of heavy metals in the process of sludge disintegration. The dissertation investigates the distribution law of typical heavy metals such as Cu, Pb, Cd, Zn in the process of microwave and citric acid-microwave cracking sludge under different specific energy and fixed specific energy conditions. The Tessier five-step continuous extraction method was used to extract heavy metals, and the changes in their content and chemical forms were analyzed, which provided certain technical support for the subsequent harmless treatment and resource utilization of excess sludge. The main findings of this paper are as follows: The dissolution rate of heavy metals Cu, Pb, Cd, and Zn increased rapidly during the citric acid-microwave cracking process in the TS specific energy range of 0–45000 kJ/kg, and then gradually tended to be gradual. The maximum dissolution rates of Cu, Pb, Cd, Zn were 8.06%, 16.58%, 14.69%, and 24.11%, respectively. The concentrations of Cu, Pb, Cd, and Zn in the sludge were mainly F4; F3, F4; F2, F3. The proportions of stable states of Cu, Pb, Cd, and Zn in sludge increased to 88.6%, 55.91%, 35.7%, and 31.35%, respectively. When the specific energy was 45000 kJ/kg TS, the concentrations of Pb, Zn, and Cd in the solid phase of the sludge appeared to increase under microwave cracking alone and decrease under the combined action of citric acid and microwave. The concentration of Cu in the solid phase of the sludge increased slightly. The dissolution rates of Pb, Cd, and Zn by microwave alone and citric acid-microwave method were 14.23% and 16.58%, 10.34% and 14.69%, 17.53%, and 24.11%, respectively. The dissolution rates of Cu by both methods were lower. The steady state ratios of Pb and Zn in the citric acid-microwave method increased to 55.91% and 31.25%, respectively; the steady state ratio of Cd in the microwave alone method increased to 39.51%; both methods had no significant effect on the stability of Cu.

Effect of arbuscular mycorrhizal fungi (Glomus mosseae) and elevated air temperature on Cd migration in the rhizosphere soil of alfalfa

Cadmium (Cd) migration in the rhizosphere soil is easily affected by plants and microorganisms. Global warming significantly affects plant growth, and arbuscular mycorrhizal fungi (AMF) can chelate heavy metals by mycelium, cell wall components, and mycelial secretion. Here, we investigated the regulation of Glomus mosseae on Cd migration in the rhizosphere soil of alfalfa under elevated temperature (ET, + 3 °C). Elevated temperature significantly decreased G. mosseae colonization rate in the roots by 49.5% under Cd exposure. Under ET + G. mosseae + Cd relative to ET + Cd, the contents of free amino acids, total and easily extractable glomalin-related soil protein (GRSP), and root Cd increased significantly; however, the changes in DTPA-Cd in the rhizosphere soil and Cd in the shoots were insignificant. In addition, G. mosseae colonization enhanced the bioconcentration factor of Cd in the roots and the total removal rate of Cd in the rhizosphere soil by 63.4% and 16.3%, respectively, under ET + Cd. However, the changes in the expression of iron-regulated transport 1 (IRT1) and natural resistance-associated macrophage protein 1 genes were insignificant under ET + G. mosseae + Cd relative to ET + Cd. In summary, temperature and G. mosseae significantly affected Cd fate in the rhizosphere soil, and IRT1 gene and rhizosphere soil pH, N, and C/N ratio were significant factors influencing Cd migration. Additionally, G. mosseae improved the remediation efficiency of Cd-contaminated soils by alfalfa under ET. The results will help us understand the regulation of AMF on the phytoremediation of heavy metal-contaminated soils under global warming scenarios.

Removal Efficiency of Heavy Metals Such as Lead and Cadmium by Different Substrates in Constructed Wetlands

In order to find an efficient and economical wetland substrate to treat mine wastewater containing various heavy metals, and effectively realize the resource utilization of water treatment residuals, in this paper, the treatment efficiency of mine wastewater containing various heavy metals was investigated using unburned ceramsite prepared from water treatment residuals (UCWTR) and clay ceramsite. The continuous dynamic test results showed that the removal rate of Pb, Cd, Cu, Zn, and Fe can reach more than 98.5% after the UCWTR-based CWs runs for 56 days, and its concentration was 30.05%, 24.85%, 20.82%, 14.63%, and 7.91% lower than that of the clay ceramsite-based CWs, respectively. SEM, XPS, and FT-IR showed that the characteristic peaks of two ceramsites were basically similar. The ceramsite undergoes ion exchange, coordination complexation, and chelation reaction with Pb, Cd, Cu, Zn, and Fe under the action of the gel of internal groups -OH, C=O, Al-OH, Si-Fe-O and C-S-H. Compared with clay ceramsite, the ion exchange reaction and chelation reaction of -OH effect and the coordination reaction of C=O effect of carboxyl group in UCWTR were enhanced. In conclusion, using UCWTR as a CWs substrate can effectively enhance the adsorption capacity of heavy metals, providing a scientific basis for the application of UCWTR-based CWs in mine wastewater treatment.

Quantitative source apportionment of heavy metals in atmospheric deposition of a typical heavily polluted city in Northern China: Comparison of PMF and UNMIX

Receptor models are rarely utilized in atmospheric deposition but are often used to identify pollutant sources and quantify their contributions. This article focuses on the soil in atmospheric deposition in a typical polluted city. Atmospheric deposition has become an important route for exogenous heavy metals’ input into ecosystems. In this study, the heavy metals in atmospheric deposition were determined in three monitoring points arranged in Handan City. According to the functional area, fluxes, sources, and accumulation in the soil were explored. The sources of heavy metals were identified by PMF (positive matrix factorization) and UNMIX. The accumulation of heavy metals in the soil was predicted. The results showed that the deposition fluxes in industrial areas were higher than other functional areas. The mean concentrations of 8 heavy metals (Cd, Cr, Cu, Mn, Ni, Pb, Zn, and As) in the atmospheric deposition exceed their background values. PMF identified five major sources and UNMIX analyzed four sources. Similar source apportionment results were acquired via PMF and UNMIX, which were the combustion of fossil fuels, steel-smelting emission, road dust, and industrial sources. Steel-smelter emission was the highest source contributor. Therefore, combining these two models was the most effective approach, and more attention should be paid to mitigating the pollution caused by the industrial activities. The prediction indicated that the accumulation of heavy metals from atmospheric deposition to the soil would increase in 30 years, the growth rate of Cd increased significantly. The results of this study could provide reference in reduction of heavy metal pollution in atmospheric deposition.