Assessment of nutrients effect on the bioaccessibility of Cd and Cu in contaminated soil

Innovative accumulative risk assessment of co-exposure to Cd, As, and Pb in contaminated rice based on their in vivo bioavailability and in vitro bioaccessibility

The consumption of cadmium (Cd), arsenic (As), and lead (Pb) co-contaminated rice exposes humans to multiple heavy metals simultaneously, with relative bioavailability (RBA) and bioaccessibility (BAc) being important determinants of potential health risks. This study evaluated the relationship between in vivo RBA and in vitro BAc of Cd, As, and Pb in rice and their cumulative risk to humans. A total of 110 rice samples were collected in Zhejiang Province, China, and 10 subsamples with varying concentration gradients were randomly selected to measure RBA using a mouse model (liver, kidney, femur, blood, and urine as endpoints) and BAc using four in vitro assays (PBET, UBM, SBRC, and IVG). Our results indicated that Cd-RBA varied from 21.2 % to 67.5 %, As-RBA varied from 23.2 % to 69.3 %, and Pb-RBA varied from 22.2 % to 68.9 % based on mouse liver plus kidneys. The BAc values for Cd, As, and Pb in rice varied according to the assay. Compared to Cd and As, Pb exhibited a lower BAc in the gastric (GP) and intestinal (IP) phases. According to the relationship between the BAc and RBA values, IVG-GP (R2 = 0.92), SBRC-IP (R2 = 0.73), and UBM-GP (R2 = 0.80) could be used as predictors of Cd-, As-, and Pb-RBA in rice, respectively. The health risks associated with co-exposure to Cd, As, and Pb in contaminated rice for both adults and children exceeded the acceptable threshold, with Cd and As being the primary risk factors. The noncarcinogenic and carcinogenic risks were markedly reduced when the RBA and BAc values were incorporated into the risk assessment. Due to the risk overestimation inherent in estimating the risk level based on total metal concentration, our study provides a realistic assessment of the cumulative health risks associated with co-exposure to Cd, As, and Pb in contaminated rice using in vivo RBA and in vitro BAc bioassays.

Tryptophan Seed Treatment Improves Morphological, Biochemical, and Photosynthetic Attributes of the Sunflower under Cadmium Stress

Tryptophan, as a signal molecule, mediates many biotic and environmental stress-induced physiological responses in plants. Therefore, an experiment was conducted to evaluate the effect of tryptophan seed treatment in response to cadmium stress (0, 0.15, and 0.25 mM) in sunflower plants. Different growth and biochemical parameters were determined to compare the efficiency of the treatment agent. The results showed that cadmium stress reduced the growth attributes, including root and shoot length, dry and fresh weight, rate of seed germination, and the number of leaves. Cadmium stress also significantly reduced the contents of chlorophyll a, b, and total chlorophyll, carotenoid contents, phenolics, flavonoids, anthocyanin, and ascorbic acid. Whereas cadmium stress (0.15 and 0.25 mM) enhanced the concentrations of malondialdehyde (45.24% and 53.06%), hydrogen peroxide (-11.07% and 5.86%), and soluble sugars (28.05% and 50.34%) compared to the control. Tryptophan treatment decreased the effect of Cd stress by minimizing lipid peroxidation. Seed treatment with tryptophan under cadmium stress improved the root (19.40%) and shoot length (38.14%), root (41.90%) and shoot fresh weight (13.58%), seed germination ability (13.79%), average leaf area (24.07%), chlorophyll b (51.35%), total chlorophyll (20.04%), carotenoids (43.37%), total phenolic (1.47%), flavonoids (19.02%), anthocyanin (26.57%), ascorbic acid (4%), and total soluble proteins (12.32%) compared with control conditions. Overall, the tryptophan seed treatment showed positive effects on sunflower plants' growth and stress tolerance, highlighting its potential as a sustainable approach to improve crop performance.

Effects of tris (2-chloroethyl) phosphate exposure on gut microbiome using the simulator of the human intestinal microbial ecosystem (SHIME)

Tris (2-chloroethyl) phosphate (TCEP) has been widely used, and its health risk has received increasing attention. However, the rare research has been conducted on the effects of TCEP exposure on changes in the structure of the human gut microbiome and metabolic functions. In this experiment, Simulator of the human intestinal microbial ecosystem (SHIME) was applied to explore the influences of TCEP on the human gut bacteria community and structure. The results obtained from high-throughput sequencing of 16S rRNA gene have clearly revealed differences among control and exposure groups. High-dose TCEP exposure increased the Shannon and Simpson indexes in the results of α-diversity of the gut microbiome. At phylum level, Firmicutes occupied a higher proportion of gut microbiota, while the proportion of Bacteroidetes decreased. In the genus-level analysis, the relative abundance of Bacteroides descended with the TCEP exposure dose increased in the ascending colon, while the abundances of Roseburia, Lachnospira, Coprococcus and Lachnoclostridium were obviously correlated with exposure dose in each colon. The results of short chain fatty acids (SCFAs) showed a remarkable effect on the distribution after TCEP exposure. In the ascending colon, the control group had the highest acetate concentration (1.666 ± 0.085 mg⋅mL-1), while acetate concentrations in lose-dose medium-dose and high-doseTCEP exposure groups were 1.119 ± 0.084 mg⋅mL-1, 0.437 ± 0.053 mg⋅mL-1 and 0.548 ± 0.106 mg⋅mL-1, respectively. TCEP exposure resulted in a decrease in acetate and propionate concentrations, while increasing butyrate concentrations in each colon. Dorea, Fusicatenibacter, Kineothrix, Lachnospira, and Roseburia showed an increasing tendency in abundance under TCEP exposure, while they had a negatively correlation with acetate and propionate concentrations and positively related with butyrate concentrations. Overall, this study confirms that TCEP exposure alters both the composition and metabolic function of intestinal microbial communities, to arouse public concern about its negative health effects.

Bioaccessibility and reliable human health risk assessment of heavy metals in typical abandoned industrial sites of southeastern China

Heavy metal pollution caused by a large number of abandoned industrial sites cannot be underestimated, but its human health risks have not been accurately assessed. This study investigated the pollution of heavy metals in soils of the typical abandoned industrial sites in southeastern China. Based on the bioaccessibility of different heavy metals (Pb, Ni, Cu, Zn, Cd, Cr) in the industrial soils, the human health risks were accurately evaluated, and the controlling factors were quantitatively assessed. The results showed that the heavy metals in each typical abandoned industrial sites had a high degree of spatial heterogeneity. Among them, Cd was the most susceptible to relevant discrete input from external factors such as human activities, followed by Zn, Pb, Cr, Ni and Cu. The bioaccessible concentration of heavy metals by the physiological-based extraction test (PBET) had a good correlation (R² = 0.58 ∼ 0.86) with its bioavailable concentration by diethylenetriaminepentaacetic acid (DTPA) extraction. The regression model based on soil parameters had great potential to predict the bioaccessibility of heavy metals in abandoned industrial sites (R² = 0.49 ∼ 0.95). The total concentration of heavy metals, Fe, soil texture and pH were the controlling factors of the metal bioaccessibility. Compared with the total concentration, the hazard index (HI) and carcinogenic risk (CR) values calculated based on gastrointestinal bioaccessibility were decreased by 39.0∼77.9% and 68.2∼79.9% in adults, and 45.3∼88.0% and 73.9∼83.5% in children, respectively. This work provides a feasible theoretical basis for reliable assessment of the human health risks of heavy metals in the abandoned industrial sites in the future.

Phytoremediation as a potential technique for vehicle hazardous pollutants around highways

With the synchronous development of highway construction and the urban economy, automobiles have entered thousands of households as essential means of transportation. This paper reviews the latest research progress in using phytoremediation technology to remediate the environmental pollution caused by automobile exhaust in recent years, including the prospects for stereoscopic forestry. Currently, most automobiles on the global market are internal combustion vehicles using fossil energy sources as the primary fuel, such as gasoline, diesel, and liquid or compressed natural gas. The composition of vehicle exhaust is relatively complex. When it enters the atmosphere, it is prone to a series of chemical reactions to generate various secondary pollutants, which are very harmful to human beings, plants, animals, and the eco-environment. Despite improving the automobile fuel quality and installing exhaust gas purification devices, helping to reduce air pollution, the treatment costs of these approaches are expensive and cannot achieve zero emissions of automobile exhaust pollutants. The purification of vehicle exhaust by plants is a crucial way to remediate the environmental pollution caused by automobile exhaust and improve the environment along the highway by utilizing the ecosystem's self-regulating ability. Therefore, it has become a global trend to use phytoremediation technology to restore the automobile exhaust pollution. Now, there is no scientific report or systematic review about how plants absorb vehicle pollutants. The screening and configuration of suitable plant species is the most crucial aspect of successful phytoremediation. The mechanisms of plant adsorption, metabolism, and detoxification are reviewed in this paper to address the problem of automobile exhaust pollution.

Amelioration of cadmium cytotoxicity to human cells by nutrient cation contents and the building of a biotic ligand model

A variety of important major and trace elements may competitively inhibit cadmium (Cd) absorption in human cells and reduce Cd toxicity. However, the impact of essential elements on the cytotoxicity of metals can be difficult to quantify and anticipate. Cd acute toxicity to Caco-2 cell viability was studied in culture solutions and modeled by a biotic ligand model (BLM). The individual effects of the cations potassium (K⁺), calcium (Ca²⁺), magnesium (Mg²⁺), ferrous ion(Fe²⁺), zinc (Zn²⁺) and manganese (Mn²⁺) on Cd toxicity were also investigated. The results indicated that the toxicity of Cd in culture solutions to cell viability declined with increasing concentrations of Zn²⁺ and Mn²⁺ in the solutions, while K⁺, Ca^{2 +}, Mg^{2 +} and Fe²⁺ had no significant effect. Using the BLM, the stability constants for the binding of Cd^{2 +}, Zn²⁺, and Mn²⁺ to biotic ligands were determined to be logK_CdBL = 5.76, logK_ZnBL = 4.39 and logK_MnBL = 5.31, respectively. Moreover, it was calculated that 51% occupancy of the biotic ligand sites for Cd by Cd was required to cause a 50% reduction in Caco-2 cell viability. A BLM was successfully established using the estimated constants to predict the Cd cytotoxicity to Caco-2 cell viability as a function of solution characteristics, so that the effective concentrations that reduced cell viability by 50% (EC50) could be predicted by the BLM within 1.6 fold changes of the observed EC50. The application's viability and precision for foretelling Cd toxicity in Caco-2 cells are discussed.

Effect of phosphorus fertilizer on phytoextraction using Ricinus communis L. in Cu and Cd co-contaminated soil

Mining activities have led to Cu and Cd contaminated of surrounding agricultural soil. To decrease the Cu and Cd accumulation in crops, the Ricinus communis L. (castor) has been used for phytoremediation. A pot experiment was served to investigate the effect of phosphate fertilizer (Ca(H₂PO₄)₂) on the growth and Cu/Cd uptake of castor in contaminated soil. The results showed that the application of P fertilizer improved the leaf cell morphology, decreased the malonaldehyde (MDA) content of castor leaves, and increased the plant biomass (28.2-34.2%). Besides, phosphate fertilizer still facilitated accumulation Cu and Cd by castor. The addition of phosphate fertilizer increased the contents of Cu in the root of castor, improved the bioconcentration factor (BCF) of Cu, and observably enhanced the accumulation of Cu (up to 201 μg/plant) in castor. Applying phosphorus increased the percentage of residual Cd, diminished the percentage of acid extractable Cd in soil, and the accumulation of Cd in castor was not significantly increased. These results suggest that phosphorus alleviated the stress of heavy metals on castor leaves and enhanced the accumulation of Cu and Cd in castor by promoting the growth of castor.

How do controlled-release fertilizer coated microplastics dynamically affect Cd availability by regulating Fe species and DOC content in soil?

Microplastics (MPs) affect the accumulation of heavy metals by regulating the soil environment. However, studies on the dynamic effects of microplastics on the available states of heavy metals in soil are lacking. In particular, how controlled-release fertilizer coated microplastics can synergistically change the avsilable states of heavy metals in soil by affecting soil physical and chemical properties and microbial community structure is still lacking. The dynamic effect of polyurethane (PU) MPs on the effective state of soil cadmium (Cd; DGTCd), at different particle sizes and concentrations, was studied in situ by diffusive gradient in thin-films (DGT) for the first time. The bioavailability, soil chemical properties, and microbial effects of PU MPs on Cd depend on PU particle size and concentration; high-concentration (1 %) PU MPs cause a significant increase in DGT-Cd concentration. The addition of PU MPs decreased soil pH and dissolved organic carbon (DOC), while increasing the absolute zeta value, Fe(II) and Mn(II), in a manner dependent on particle size, concentration, and culture time. Correlation analysis combined with path analysis showed that PU MPs affected the effective state of Cd by changing soil properties, among which Fe(II) content and DOC were important factors controlling the activation of Cd. Meanwhile, changes in soil properties and heavy metal availability correlated significantly with microbial community composition, suggesting that PU MPs may indirectly impact heavy metal activity by affecting microorganisms and functional genes associated with C and Fe cycling. Therefore, when the concentration of PU MPs is higher than 1 %, we should strengthen ecological risk prevention and control of the compound pollution of controlled-release fertilizer coated microplastics and heavy metals in farmland soil.

Chemical structure and nanomechanics relevant electrochemistry of solid-phase humic acid along a typical forest-river-paddy landscape section in eastern China and its environmental implications

Solid-phase humic acid (HA_solid) plays a critical role in global carbon cycle and redox biogeochemistry of topsoil, because of its unique physicochemical properties, including electrochemical property. In this study, topsoil HA_solid along a typical forest-river-paddy landscape section in eastern China was investigated in the aspects of electrochemical property, chemical structure and nanomechanics, and their relationship. Nano-size HA_solid particles were extracted from topsoil of paddy soil (PS-HA_solid), forest soil (FS-HA_solid) and riverside sediment (RS-HA_solid). Results showed that all the HA_solid were conductive and played an important role in conductivity of topsoil suspension. HA_solid contained both reversible and irreversible redox peaks, with redox activity of PS-HA_solid > RS-HA_solid > FS-HA_solid. Owing to limited humification, electron exchange capacity (EEC) values of topsoil HA_solid suspensions were modest (3.18-4.45 μmol e^-g^-1 HA_solid). Compared with RS-HA_solid and FS-HA_solid, PS-HA_solid showed higher aromaticity and higher degree of humification with simple and even nanomechanical property. Long-term cultivation (human activities) as well as high content of polyvalent metals in paddy soil were supposed to facilitate formation of aromatic carbon and improve humification of HA_solid. The results suggested that aromatic carbon and high humification degree of PS-HA_solid contributed to simple and even nanomechanics, which further optimized its electrochemical property. This study not only provides novel insight into the mechanism of HA_solid mediating electron transfer, but also inspires ideas for soil and environmental management with different purposes based on regulation of HA_solid.

Mechanisms of Cd and Cu induced toxicity in human gastric epithelial cells: Oxidative stress, cell cycle arrest and apoptosis

Cadmium (Cd) and copper (Cu) are widely present in foods. However, their adverse effects on human gastric epithelium are not fully understood. Here, human gastric epithelial cells (SGC-7901) were employed to study the toxicity and associated mechanisms of Cd + Cu co-exposure. Their effects on cell viability, morphology, oxidative damage, cell cycle, apoptosis, and the mRNA levels of antioxidases and cell cycle regulatory genes were investigated. Co-exposure to Cd (5 μM)/Cu (10 μM) induced >40% cell viability loss, whereas little effect on cell viability at <10 μM Cd or 40 μM Cu. Compared to individual exposure, co-exposure induced greater oxidative damage by elevating ROS (3.5 folds), malondialdehyde (2.3 folds) and expression of SOD1 and HO-1 besides inhibiting CAT, GPX1 and Nrf2. A marked S cell-cycle arrest was observed in co-exposure, evidenced by more cells staying in the S phase (36%), up-regulation of cyclins-dependent kinase (CDK4) and CDKs inhibitor (p21) and down-regulation of CDK2, CDK6 and p27. Furthermore, higher apoptosis (22%) with floated and round cells occurred in co-exposure group. Our data implicate the cytotoxicity of Cd + Cu co-exposure was higher than individual exposure, and individual assessment would underestimate their potential health risk. Oxidative stress and cell cycle arrest possibly played a role in Cd + Cu induced toxicity and apoptosis in SGC-7901 cells. Our data suggest the importance to reduce Cd in foods to decrease its adverse impacts on human digestive system.

Geochemical phases of soil and the bioaccessibility of some elements in soils and vegetables from boron mines

The bioaccessibility of some elements (As, B, Cd, Cu, Fe, Mn, Ni and Zn) in soils and vegetables was determined using the physiologically based extraction test. An investigation of the geochemical phases of soils through sequential extraction methods followed by ICP-MS detection was also undertaken. Samples were collected from Iskele, Begendikler and Yolbasi villages in the Bigadic region and Yildiz village in the Susurluk region of Balikesir province, Turkey. All of these villages are close to boron mines. Principal component analysis and correlation analysis demonstrated the interrelationship between the bioaccessibility values of these elements in the gastric and intestinal extracts of soils as well as the plant samples grown in those soils and the elements' concentrations in the different soil fractions. From the bioaccessible concentrations of the elements in the intestinal phases, it was shown that the amounts of As, B, Cu, Mn and Ni in some plant samples were higher than the recommended and tolerable values for human consumption. The bioaccessibilty of these elements in the soils and plants were statistically related with the concentrations of these elements in the labile phases of the soil. The methodology adopted here would be applicable to determining interactions between elements and soil fractions and the interrelationships between bioaccessibility data and soil fractions for any soil samples.