Assessing soil remediation effect of Cr and Pb based on bioavailability using DGT, BCR and standardized determination method.

In the field of soil remediation, the importance of bioavailability of pollutants has not received adequate attention, leading to the excessive application of remediation measures. Therefore, to ensure the safe use of farmland soil, a scientific method is needed to assess labile contaminants and their translocation in plants. To evaluate soil remediation effect based on bioavailability, the concentrations of these heavy metals in soil were analyzed using by the method for total metal content, the Community Bureau of Reference (BCR) extraction, and the diffusive gradients in thin films (DGT) technique. The results reveal that the correlation coefficients between metal concentrations measured by DGT and those accumulated in rice grains are the highest (Cr-R2 = 0.8966, Pb-R2 = 0.9045). However, the capability of method for total metal content to evaluate the remediation effect of heavy metals is very limited. In contrast, although Cr and Pb measured by BCR show a high correlation with HMs in rice plants, the method still falls short in precisely assessing bioavailability. Significantly, DGT proves to be more effective, successfully distinguishing the remediation effects of different treatments. Generally, DGT offers a more accurate and simpler assessment method, underscoring its practical significance for monitoring soil remediation and environmental management.

The effect of anthropogenic activities on the behavior of novel brominated flame retardants in surface soil of Northern China urbanized zone.

Novel brominated flame retardants (NBFRs) have emerged as an alternative to traditional brominated flame retardants (BFRs) and may pose risks to the environment and human health. However, the distribution pattern of NBFRs in urbanized zones and their association with multiple socioeconomic variables have not been adequately explored. Herein, seven NBFRs were investigated in surface soil samples from Tianjin, China, a typical urbanized area. The ∑7NBFRs ranged from n.d. to 101 ng/g, dry weight (dw) (mean: 12.6 ± 17.6 ng/g dw), which exhibited a relatively elevated level compared to NBFRs in soils from other regions worldwide. Decabromodiphenylethane (DBDPE) was the main contaminant, and its concentration ranged from 0.378 to 99 ng/g, dry weight (dw) (mean: 11.4 ± 17.0 ng/g dw), accounting for 81 % of the ∑7NBFRs. Notably, NBFRs exhibited peak concentrations within residential zones, significantly surpassing those recorded in the remaining four regions (green, farmland, water environment and other) (p < 0.05). Furthermore, the concentration of NBFRs in the soil of the Binhai New District within Tianjin was the highest, significantly exceeding that of other administrative areas, which was closely related to the intensive industrial activities in this region. The above results indicate that human activities are a key factor affecting the concentration of NBFRs in the soil. Moreover, a variety of statistical methods were employed to investigate the correlation between socioeconomic variables and the distribution of NBFRs. The concentration of NBFRs showed a significant correlation with population density and the gross domestic product (GDP) (p < 0.05), and the incorporation of administrative regional planning into structural equation models demonstrated an indirect influence on the spatial distribution of NBFRs concentration, mediated by its impact on population density. These results emphasize the association between NBFRs contamination and the degree of urbanization, thereby providing valuable insights for assessing the exposure risk of NBFRs among urban residents.

Microbial nitrogen transformation regulates pathogenic virulence in soil environment.

Soil nitrogen addition induces the generation and proliferation of some bacterial virulence, yet the interactive mechanisms between the two remain unclear. Here we investigated the variation of virulence genes (VGs) abundance during soil nitrogen transformation, and explored the biological mechanism and key pathways involved in the regulation of VGs by nitrogen transformation. The results showed that the diversity and abundance of virulence genes in soil under high nitrogen input (100 mg/kg) were markedly higher than those under low nitrogen input (50 mg/kg), suggesting a trade-off between the prevalence of virulence genes and nitrogen metabolism. Nutritional/metabolic factor, regulation, immune modulation and motility were the dominant virulence types. Linear regression analysis showed that soil nitrogen mineralization and nitrification rate were closely correlated with the abundance of virulence genes, mainly involving adherence, nutritional/metabolic factors and immune modulation (p < 0.05). Structural equations indicated that microbial community succession associated with nitrogen transformation largely contributed to the changes in VGs abundance. Metagenomic analysis revealed that major virulence genes pilE, pchB, and galE were regulated by nitrogen-functional genes gdh, ureC, and amoC, implying that microbial nitrogen transformation influences immune modulation, nutritional/metabolic factors, and adherence-like virulence. The meta-transcriptome reiterated their co-regulation, and the key pathway may be glutamate/urea> α-ketoglutarate/ammonia > pyruvate/amino acid. The outcome provides strong evidence on the linkage between microbial nitrogen transformation and pathogenic virulence factors development in the soil environment, which will aid in the effective suppression of the prevalence of soil pathogenic virulence.

Prediction of the bioaccessibility and accumulation of cadmium in the soil-rice-human system based on optimized DGT and BCR coupled models.

Cadmium, as a typical heavy metal, has the potential to induce soil pollution and threaten human health through the soil-plant-human pathway. The conventional evaluation method based on the total content in soil cannot accurately represent the content migrated from the food chain to plants and the human body. Previous studies focused on the process of plant enrichment of heavy metals in soil, and very few studies directly predicted human exposure or risk through the labile state of Cd in soil. Hence, a relatively accurate and convenient prediction model of Cd release and translocation in the soil-rice-human system was developed. This model utilizes available Cd and soil parameters to predict the bioavailability of Cd in soil, as well as the in vitro bioaccessibility of Cd in cooked rice. The bioavailability of Cd was determined by the Diffusive Gradients in Thin-films technology and BCR sequential extraction procedure, offering in-situ quantification, which presents a significant advantage over traditional monitoring methods and aligns closely with the actual uptake of heavy metals by plants. The experimental results show that the prediction model based on the concentration of heavy metal forms measured by BCR sequential extraction procedure and diffusive gradients in thin-films technique can accurately predict the Cd uptake in rice grains, gastric and gastrointestinal phase (R2=0.712, 0.600 and 0.629). This model accurately predicts Cd bioavailability and bioaccessibility across the soil-rice-human pathway, informing actual human Cd intake, offering scientific support for developing more effective risk assessment methods.

Enhanced sinks of polystyrene nanoplastics (PSNPs) in marine sediment compared to freshwater sediment: Influencing factors and mechanisms.

The difference in the transport behaviors of nanoplastics consistently assistant with their toxicities to benthic and other aquatic organisms is still unclear between freshwater and marine sediments. Here, the mobilities of polystyrene nanoplastics (PSNPs) and key environmental factors including salinity and humic acid (HA) were systematically studied. In the sand column experiments, both tested PSNPs in the freshwater system (100 nm NPs (100NPs): 90.15 %; 500 nm NPs (500NPs): 54.22 %) presented much higher penetration ratio than in the marine system (100NPs: 8.09 %; 500NPs: 19.04 %). The addition of marine sediment with a smaller median grain diameter caused a much more apparent decline in NPs mobility (100NPs: from 8.09 % to 1.85 %; 500NPs: from 19.04 % to 3.51 %) than that containing freshwater sediment (100NPs: from 90.15 % to 83.56 %; 500NPs: from 54.22 % to 41.63 %). Interestingly, adding HA obviously led to decreased and slightly increased mobilities for NPs in freshwater systems, but dramatically improved performance for NPs in marine systems. Electrostatic and steric repulsions, corresponding to alteration of zeta potential and hydrodynamic diameter of NPs and sands, as well as minerals owing to adsorption of dissolved organic matter (DOM) and aggregations from varied salinity, are responsible for the mobility difference.

Copper-zinc nanoparticle-decorated nitrogen-doped carbon composite for electrochemical determination of triclosan.

A new sensor based on copper-zinc bimetal embedded and nitrogen-doped carbon-based composites (CuZn@NC) was prepared for triclosan (TCS) detection by pyrolyzing the precursor of Cu-Zn binuclear metal-organic framework (MOF). The performance for detecting TCS was evaluated using linear scanning voltammetry (LSV) and differential pulse voltammetry (DPV), and the proton and electron numbers during TCS oxidation have been proved to be one-to-one. The results indicated that CuZn@NC can present a satisfactory analysis performance for TCS detection. Under the optimized conditions, the linear response range was 0.2-600 µM and the detection limit was 47.9 nM. The sensor presented good stability (signal current dropped only 2.5% after 21 days) and good anti-interference of inorganic salts and small molecular organic acids. The good recovery (97.5-104.1%) for detecting spiked TCS in commercial products (toothpaste and hand sanitizer) suggested its potential for routine determination of TCS in real samples.

Spatiotemporal variations in soil pollution by polycyclic aromatic hydrocarbons over a 20-year economic boom in different districts of a heavy industrial city in North China.

Urbanization-related human activities, such as population aggregation, rapid industrial expansion, and intensified traffic, are key factors that impact local polycyclic aromatic hydrocarbon emissions and their associated health risks. Consequently, regions with varying degrees of urbanization within a megacity may exhibit diverse spatiotemporal patterns in the presence and distribution of soil polycyclic aromatic hydrocarbons, resulting in different levels of ecological risks for local inhabitants following the same period of development. In this study, we measured the concentrations of 16 polycyclic aromatic hydrocarbons in soil samples collected from industrial district and rural district in Tianjin (China) in 2018, and compared with polycyclic aromatic hydrocarbon data in 2001 from a previous study to characterize these regional variations in occurrence, source, and human risk of polycyclic aromatic hydrocarbons induced by urbanization with time and space. The results indicate the 20-year rapid urbanization and industrialization has differentially affected the composition, distribution and sources of polycyclic aromatic hydrocarbons in soils from different economic functional zones in Tianjin. Additionally, its impact on health risks in rural district appeared to be more significant than that in industrial district.

The weakened physiological functions of human serum albumin in presence of polystyrene nanoplastics.

Due to the widespread presence of nanoplastics (NPs) in daily essentials and drinking water, the potential adverse effects of NPs on human health have become a global concern. Human serum albumin (HSA), the most abundant and multi-functional protein in plasma, has been chosen to understand the biological effects of NPs after entering the blood. The esterase activity and the transport of bisphenol A in the presence of polystyrene nanoplastics (PSNPs) under physiological conditions (pH 4.0 and 7.4) have been investigated to evaluate the possible biological effects. The interactions between PSNPs and HSA have also been systematically studied by multispectral methods and dynamic light scattering techniques. The esterase activity of HSA presented a decreased trend with increasing PSNPs; conversely, higher permeabilities are accompanied by higher amounts of PSNPs. Compared with the unchanged hydrodynamic diameter and weaker interactions at pH 7.4, stronger binding between HSA and PSNPs at pH 4.0 led to a significant increase in the particle size of the PSNPs-HSA complex. The quenching mechanism belonged to the static quenching type. The electrostatic force is proposed to be the dominant factor for PSNPs binding to HSA. The work provides some information about the toxicity of NPs when exposed to humans.

Contamination Status, Environmental Factor and Risk Assessment of Polychlorinated Biphenyls and Hexachlorobutadiene in Greenhouse and Open-Field Agricultural Soils across China.

With the popularization and high-intensity utilization of greenhouse cultivation for crops growth, the pollution of greenhouse soils has been of concern. Therefore, a national-scale survey was conducted to investigate the contamination status, sources, influence factors and the risks of polychlorinated biphenyls (PCBs) and hexachlorobutadiene (HCBD) in greenhouse and nearby open-field soils. Contents of PCBs ranged from 10-6). This study provided a full insight on the contamination status and risks of PCBs and HCBD when guiding greenhouse agriculture activities.

Predictive and estimation model of Cd, Ni, and Zn bioaccumulations in maize based on diffusive gradients in thin films.

Consumption of maize contaminated with heavy metals such as cadmium, nickel, and zinc threaten human health. For situ measuring the bioavailability of heavy metals, the diffusive gradients in thin films (DGT) is superior to other traditional methods. It is also important to find a method for predicting heavy metal enrichment in maize based on the DGT method. In this study, field surveys were conducted in the main maize producing areas of Tianjin, China. Heavy metal concentrations in maize grains were predicted by coupling DGT with traditional extraction methods. The results show that coupling DGT with soil solution can significantly improve prediction accuracy (Cd-R2 = 0.908, Ni-R2 = 0.903, and Zn-R2 = 0.904). This indicated that DGT and soil solution were feasible predictors of heavy metal concentration in maize. The DGT induced fluxes in soil/sediment (DIFS) model was used to simulate the uptake process of heavy metals by DGT, and better reveal the desorption processes of heavy metals in soils. DIFS-based desorption processes were employed to characterize the resupply ability of heavy metals in soils. The coupling of DGT and DIFS parameters provided the best prediction accuracy in this study (Cd-R2 = 0.920, Ni-R2 = 0.928, and Zn-R2 = 0.908). Predictions are slightly weaker for Zn than for Cd and Ni (Cd-P < 0.01, Ni-P < 0.01, and Zn-P < 0.05). The reason is that the average resupply type of Cd and Ni in soil is partially sustained while Zn is resupplied via diffusion only. The desorption rate k-1 can excellently improve the prediction accuracy of DGT, which avoids the disadvantage that soil solution does not consider desorption. The coupling of DGT and DIFS parameters provides an accurate and reliable method for predicting heavy metal enrichment in maize.

Exploring the Relationship between Ecosystem Services under Different Socio-Economic Driving Degrees.

The large-scale transformation of natural ecosystems to socio-economic development land types under human activities was a primary reason for the decline of regional ecosystem services. It is a key issue for regional ecosystem planning and management to reveal the relationship between ecosystem services of different land use types under different socio-economic driving degrees. However, the current related research was not in-depth. Based on the land use data of Wuhan City in 1980, 1990, 2000, 2010, and 2020, this study classified land use into three categories according to the different degrees of human activities on natural ecosystem development: the land use of a natural ecosystem (LUNE), the land use of a productive ecosystem (LUPE), and the land use of a socio-economic system (LUSE). The InVEST model was used to simulate five ecosystem services (grain yield, water yield, carbon storage, habitat quality, and water purification), and the spatio-temporal distribution and functional transformation of the three land use types were analyzed. Results showed that with the intensified urban expansion in Wuhan, the LUSE types increased to 2.7 times that of the original. However, the natural land types basically maintained a stable area, coupling with the large-scale transformation between the LUPE and LUSE types. Land use change resulted in significant spatial changes of five ecosystem services, especially carbon storage and habitat quality. The correlation analysis indicated that the five kinds of ecosystem services mainly showed a synergistic relationship, meanwhile the LUSE type denoted the most significant correlation with ecosystem services among these three category types. This study indicated that besides the protection of natural ecosystems, the LUSE type would become the key land use type in the planning and management of improving regional ecological function.

Accumulation Characteristics and Pollution Evaluation of Soil Heavy Metals in Different Land Use Types: Study on the Whole Region of Tianjin.

Heavy metal pollution in soil has received much attention in recent decades. Many studies have analyzed the interaction between specific soil quality and soil heavy metal pollution. However, there is little information about the pollution status, spatial distribution and pollution sources of heavy metals in the province of Tianjin. In this paper, the distribution characteristics and pollution sources of heavy metals in soil were studied by means of the surface soil of Tianjin, as the study area and object, conducted in combination with land use types, using multiple data analysis and multivariate statistics, while the pollution levels were evaluated by various indices. The results showed the mean contents of the seven heavy metals of the studied elements followed an increasing order of Cd (0.15 mg/kg) < As (11.9 mg/kg) < Cu (24.3 mg/kg) = Pb (24.3 mg/kg) < Ni (27.9 mg/kg) < Cr (70.7 mg/kg) < Zn (79.1 mg/kg). The median values of Cr and Ni were lower than the background values and did not exceed the screening values at the points, and the median values of Cu, Zn and Pb were close to the background values, while the median contents of As and Cd were higher than the background values. The highest accumulation of heavy metals was found in grassland, and the coefficient of variation of heavy metal contents were higher in garden land, industrial and mining storage land, residential land and transportation land, indicating that the soil heavy metal contents under these land use types were more significantly disturbed by human factors. The evaluation results of the ground accumulation index method showed that the soil in Tianjin was free of pollution, except for Cd, which was at the non-polluted to moderately polluted level. The Nemero integrated pollution index evaluation method and the pollution load index evaluation method together showed that the integrated pollution levels of heavy metals in Tianjin soils were both at no pollution level/safety level. Apart from Cd and As, which were not correlated, the other heavy metals were correlated with each other two by two. Cd, Pb and Zn were the main pollution contributors from traffic, industry and other anthropogenic factors, while Cr and Ni were the main pollution contributors from soil parent material, and Cu was the main pollution contributor from mining and metal smelting. In addition, As was presumed to be the main source of pollution contribution from agriculture and surface runoff.

Distribution and speciation of arsenic in seasonally stratified reservoirs: Implications for biotransformation mechanisms governing interannual variability.

HPLC-ICPMS was used to analyze the spatiotemporal variation of As species in different sections and tributaries of the Aha Reservoir over four seasons, and the migration and transformation mechanisms were clarified by combined analysis of hydrochemical parameters and microbial composition. The results showed that the internal release of As from the reservoir sediments is mainly due to the reduction of iron oxide and the release of adsorbed As(V). The average proportion of As(III) increased from 27.2% in autumn to 46.5% in summer, 68.9% in winter, and up to 70.8% in spring. In spring and summer, the high concentration of As(III) and organic arsenic in the epilimnion under phosphorus restriction was caused by the reductive metabolism of phytoplankton after intake of As(V). The arsenic species in the metalimnion were mainly affected by the oxidation-reduction potential (ORP). In summer and autumn, As-oxidizing bacteria used As(III) as an electron donor, and nitrate played an important role as an electron acceptor, maintaining the dominance of As(V) in the hypolimnion. However, in winter and spring, temperature-controlled ORP was the main process, which was dominated by As(III). In conclusion, As species show annual cycles in different layers of seasonally thermal stratified reservoirs. It provides a systematic mechanism of As species transformation in reservoirs, especially the effect of biological transformation mechanism.

Efficient pH-universal degradation of antibiotic tetracycline via Co2P decorated Neosinocalamus affinis biochar.

Considering the complexity of traditional cobalt phosphide (Co2P) loaded biochar synthesis research on a simple and efficient synthesis method has practical significance. In this study, after phosphoric acid activation, Neosinocalamus affinis biochar (NAB) and nanoplate Co3O4 quickly formed a Co2P-NAB composite material with high Co2P crystallinity and was uniformly dispersed on the surface of NAB in a microwave reactor. Co2P-NAB has an excellent catalytic degradation effect in the activation of peroxymonosulfate (PMS) to degrade tetracycline (TC). The optimal TC degradation efficiency was achieved with the addition of 50 mg L-1 TC concentration, 0.2 g L-1 catalysts, 0.406 mM PMS and pH = 6.02. In addition, according to the pseudo-first-order reaction rate constant calculation, the composite of Co2P-NAB and PMS the synergy efficiency is 81.55 %. Compared with Co2P-NAB (10.83 %) and PMS (7.62 %) alone, the Co2P-NAB/PMS system has a significant promotion effect on the degradation of TC molecules. Additionally, the Co2P-NAB/PMS system had a TC mineralization rate of 68 % in 30 min. Furthermore, after a series of characterization, detection and analysis, and influencing factor experiments, we proposed a potential mechanism for the Co2P-NAB/PMS reaction system to degrade TC and found that singlet oxygen (1O2) plays an essential role in the non-radical degradation process. Finally, according to the liquid chromatography-mass spectrometry (LC-MS) detection of TC degradation intermediates, a possible degradation route was proposed. Therefore, this work uses microwave technology to present a novel and simple synthesis method for transition metal phosphides, which provides potential application value for the treatment of actual wastewater with heterogeneous catalysts.

Predictive model for cadmium uptake by maize and rice grains on the basis of bioconcentration factor and the diffusive gradients in thin-films technique.

It is possible for heavy metals in soils to be adsorbed by crop roots and then accumulated in crops, which eventually causes great health risk when the crops are ingested by humans. Thus, it is valuable to understand the enrichment model of heavy metals in crops. Diffusive gradients in thin-films (DGT) technique, as an in-situ passive sampling method, can be used to evaluate the bioavailable heavy metals contents in soils. In this study, data of the bioavailable cadmium (Cd) in soils determined by DGT and Cd contents uptake in rice and maize grains in Tianjin, Zhejiang and Guangxi provinces of China were collected from previous references in Web of Science. By comparing bioconcentration factors, it was found that the heavy metal concentrations accumulated in rice and maize followed a general order roots > stems or leaves > grains. An accurate and robust model for the prediction of Cd content in maize and rice grains was established based on bioconcentration factor (BCF) and the bioavailable Cd content determined by DGT method, with R2 0.986 and root mean square error (RMSE) 0.128. This result suggests that the DGT method can be good tool for predicting heavy metals uptake in crops.

The effect of anthropogenic activities on the environmental fate of chlorinated paraffins in surface soil in an urbanized zone of northern China.

Chlorinated paraffins (CPs) have been widely used as halogenated flame retardants and plasticizers since the mid-20th century. The prevalence of CPs in soil has been widely reported, but the distribution pattern of CPs in urbanized zones and their association with multiple socioeconomic variables have not been adequately explored. Herein, short-chain and medium-chain chlorinated paraffins (SCCPs and MCCPs) were investigated in surface soil samples from Tianjin, China, a typical urbanized area. The concentration distributions of SCCPs and MCCPs showed similar trends in different administrative divisions and land use types: urban areas > suburbs > outer suburbs (p < 0.001) and residential areas > greenbelts > agricultural areas (p < 0.001). The CP congeners in residential surface soils mainly included those with longer carbon chains and high degree of chlorination, while the CP congeners in agricultural surface soils mainly consisted of those with shorter carbon chains and fewer chlorine substituents. Multiple statistical approaches were used to explore the association between socioeconomic factors and CP distribution. CP concentration was significantly correlated to population density and gross domestic product (GDP) (p < 0.001), and structural equation models incorporating administrative regional planning showed an indirect impact on the distribution of MCCP concentration due to the influence of regional planning on population density. These results highlight the association between CP contamination and the degree of urbanization, and this paper provides useful information toward mitigating the exposure risk of CPs for urban inhabitants.

Ecological risk assessment of heavy metals in farmland soils in Beijing by three improved risk assessment methods.

Beijing, as the capital of China, still has soil pollution problems that cannot be ignored. However, there are few studies on the overall ecological risks of heavy metals in farmland soils in Beijing. This study selected 432 soils and crops heavy metal content data of eight districts in Beijing from academic papers and academic journal papers. In this study, the improved Hakanson method, improved analytic hierarchy process (AHP), and integrated quality impact index (IICQ) comprehensively were used to evaluate the impact of Pb, As, and Cd pollution on the farmland soil environment, and the applicable conditions of these methods were discussed. The results by improved Hakanson method showed that both Pb and As were at the normal ecological risk level, while Cd was the largest contributor to potential ecological risk which accounted for 72.54% of the total risk and is mainly at a moderate ecological risk level. The analysis by improved AHP showed that the average comprehensive index of soil heavy metal pollution in the study area was 0.2317, which was at a light pollution level. The IICQ of soil and agricultural products were between 0 and 1 demonstrating that the soil was clean. In summary, the pollution of heavy metals Pb, As, and Cd in the study area is at a relatively low level, and there is no significant risk to the surrounding environment and human health. IICQ method is suitable for the evaluation of soil heavy metal composition and individual impact and can be more accurately used for the overall ecological evaluation of soil-crop-human health system.

Evolution and Efficiency Assessment of Pesticide and Fertiliser Inputs to Cultivated Land in China.

Excessive use of pesticides and fertilisers has been a key issue limiting sustainable agricultural development. China is a typical pesticide- and chemical-fertiliser-dependent agricultural production area. We have matched the target indicators related to sustainable agricultural development (SDG1 and SDG2) and analysed the gap between China and four developed countries in terms of fertiliser and pesticide use intensity and efficiency from 2002 to 2016. We have used an improved Logarithmic Mean Divisia Index model and cluster analysis to identify the factors and effects driving increased pesticide and fertiliser inputs in China, and we discuss the exploratory effects of different provinces in reducing pesticide and fertiliser application and increasing efficiency. The findings reveal that (1) China is a typical pesticide- and fertiliser-dependent agricultural production area. The average combined fertiliser application efficiency in China from 2002 to 2016 was only 28% of that of the Netherlands, and the country's average combined pesticide application efficiency was only 35% of that of the USA. (2) The most important of the three main drivers of the increase in pesticide and fertiliser inputs in China is the value added of the primary industry, contributing 56% for the period 2007-2016. (3) Further analysis at the provincial level according to four types-high-intensity high-yield type, high-intensity low-yield type, low-intensity high-yield type, and low-intensity low-yield type-clarified the provinces that should be focused on at the national level in terms of pesticide and fertiliser application reduction and efficiency increase in the future.

Determination of Labile Cadmium in Soils Using a New Sodium Alginate-Polyglutamic Acid-Diffusive Gradient in Thin Films.

Sodium alginate-polyglutamic acid was used to develop a new diffusive gradient in thin films (SA-PGA-DGT) device, which was proven to be suitable for the investigation of labile Cd in soil. The adsorption capacity of Cd was calculated to be approximately 16.8 µg/cm2 , which was hardly affected by factors including pH (5-9), ionic strength (0.1-100 mM), and the presence of other metals (Pb, Cu, Ni, and Cr). The SA-PGA gel has dense and uneven pores with large specific surface area, which ensures the adsorption of Cd by functional groups of the gel. A kinetics study indicated that the adsorption rate of Cd by the binding gel can be described as a pseudo-second-order reaction. Deployment of the SA-PGA-DGT in the soils of Tang Gu (located in Binhai New District, Tianjin, China) showed a strong positive linear correlation between Cd measured by the device and exchangeable Cd measured by the Tessier method (R = 0.73, p < 0.01). Cadmium determined by the SA-PGA-DGT device was less affected by soil properties. This new SA-PGA-DGT has obvious advantages over other methods in respect of the labile Cd analysis in soil. The innovative novel device expands the variety of existing DGT technologies and can be utilized to monitor the level of labile Cd in soil effectively. Environ Toxicol Chem 2021;40:1559-1569. © 2021 SETAC.

Application of DGT/DIFS to assess bioavailable Cd to maize and its release in agricultural soils.

Tianjin, as an important maize production region in China, has a long history of sewage irrigation resulting in the soil cadmium (Cd) contamination. In this study, single extractions of CaCl2 and HNO3, BCR sequential extraction and the diffusive gradients in thin films technique (DGT) were used to measure the bioavailable Cd content in soils. The Cd content in soil samples all exceeded the background values, with 14.3% and 33.3% of sites in the Baodi District (BDD) and Jinghai District (JHD) exceeding the risk control values, respectively. The average content of Cd in maize samples is lower than the pollution control values, which may be related to the higher pH (8.53) and organic matter (OM) content (15.01 g kg-1) in soils. Bioavailable Cd measured by DGT correlated well with Cd in maize grains (R2 =0.92). The DGT and DIFS model predicted the metals release from the agricultural lands, the total concentration of Cd in soil was relatively low, but the labile Cd in the soils has adequate metal release capability. This study shows that DGT is efficient in predicting Cd accumulation in grains from contaminated soils.