Hyperaccumulators' Diversity Enhances Cd-Contaminated Soil Restoration and Reduces Rice Cd Uptake under an Intercropping System.

Cd accumulation in rice-cultivated soils across China is a major problem that needs to be tackled. A plot experiment was carried out using heavy metal (HM) hyperaccumulators Amaranthus hypochondriacus L. and Perilla frutescens (L.) Britt. intercropped with low-accumulation rice to obtain safe edible rice while reducing the soil Cd concentration. It was found that Cd concentration in soil was decreased by 7.43 and 2.86% under rice intercropped with Amaranthus hypochondriacus L. and Perilla frutescens (L.) Britt., respectively, compared to single cropped rice. In addition, enhanced effects were noted under the combination of Amaranthus hypochondriacus L., Perilla frutescens (L.) Britt, and rice in which a 20.35% decrease in soil Cd content was recorded compared to single-cultivated rice soil. In addition, the available Cd in soil was reduced by 4.00 and 5.00% under rice/Amaranthus and rice/Perilla, respectively, and 12.00% under rice/Amaranthus/Perilla mixed culture. Moreover, the concentration of Cd in various parts of rice was under permissible limits. However, rice biomass was decreased by the presence of hyperaccumulators. This study suggests that combining HM hyperaccumulator plants and low-accumulation rice provides efficient Cd extraction results and could be a crucial option for restoring Cd-contaminated soil without reducing rice production.

Investigation of arsenic contamination in soil and plants along the river of Xinzhou abandoned gold mine in Qingyuan, China.

The exploitation of mineral resources is very important for economic development, but disorderly exploitation poses a serious threat to the ecological environment. However, investigations on the advantages of plant species and environmental pollution in polluted mining areas are limited. Thus, a survey was conducted to evaluate the impacts of abandoned mines on the surrounding ecological environment along rivers in polluted areas and to determine the Arsenic (As) pollution status in soil and plants. The results showed that the soil and vegetation along the river in the survey area were seriously polluted by As. The total As content of the 15 samples was significantly greater than the national soil background value (GB 15618-2018), and degree of pollution was nonlinearly related to the distance from the mine source, R2 = 0.9844. B. bipinnata, P. vittata and B. nivea were predominant with degrees of dominance of 0.01-0.33, 0.05-0.11, and 0.06-0.14 respectively. The As enrichment capacities of Juncus and P. vittata were significantly greater than those of the other plants, while the bioaccumulation factors (BCFs) were 21.81 and 7.04, respectively.

Effects of arsenic on gut microbiota and its bioaccumulation and biotransformation in freshwater invertebrate.

This study aimed to investigate the impact of arsenic stress on the gut microbiota of a freshwater invertebrate, specifically the apple snail (Pomacea canaliculata), and elucidate its potential role in arsenic bioaccumulation and biotransformation. Waterborne arsenic exposure experiments were conducted to characterize the snail's gut microbiomes. The results indicate that low concentration of arsenic increased the abundance of gut bacteria, while high concentration decreased it. The dominant bacterial phyla in the snail were Proteobacteria, Firmicutes, Bacteroidota, and Actinobacteriota. In vitro analyses confirmed the critical involvement of the gut microbiota in arsenic bioaccumulation and biotransformation. To further validate the functionality of the gut microbiota in vivo, antibiotic treatment was administered to eliminate the gut microbiota in the snails, followed by exposure to waterborne arsenic. The results demonstrated that antibiotic treatment reduced the total arsenic content and the proportion of arsenobetaine in the snail's body. Moreover, the utilization of physiologically based pharmacokinetic modeling provided a deeper understanding of the processes of bioaccumulation, metabolism, and distribution. In conclusion, our research highlights the adaptive response of gut microbiota to arsenic stress and provides valuable insights into their potential role in the bioaccumulation and biotransformation of arsenic in host organisms. ENVIRONMENTAL IMPLICATION: Arsenic, a widely distributed and carcinogenic metalloid, with significant implications for its toxicity to both humans and aquatic organisms. The present study aimed to investigate the effects of As on gut microbiota and its bioaccumulation and biotransformation in freshwater invertebrates. These results help us to understand the mechanism of gut microbiota in aquatic invertebrates responding to As stress and the role of gut microbiota in As bioaccumulation and biotransformation.

Survival strategies in arsenic-contaminated environments: Comparative insights from native and exotic aquatic species.

The aim of this work was to study the sublethal effects, biokinetics, subcellular partitioning and detoxification of arsenic in two native Chinses species, Bellamya quadrata and Cipangopaludina cathayensis, as well as an exotic South American species, Pomacea canaliculata. The exotic species exhibited higher tolerance than native species. Physiologically based pharmacokinetic model results showed that the exotic species P. canaliculata exhibited a lower bioaccumulation rate and a greater metabolism capacity of As. Subcellular partitioning of As revealed that P. canaliculata exhibits superior As tolerance compared to the native species B. quadrata and C. cathayensis. This is attributed to P. canaliculata effective management of the metal sensitive fraction and enhanced accumulation of As in the biologically detoxified metal fraction. Under As stress, the biochemical parameters (superoxide dismutase, malondialdehyde, glutathione and glutathione S-transferase) of the exotic species P. canaliculata changed less in the native species, and they returned to normal levels at the end of depuration period. Our study provides evidence of the superior survival capability of the exotic species P. canaliculata compared to the native species B. quadrata and C. cathayensis under environmentally relevant levels of As contamination.

Transcriptomic and metabolomic analysis of the mechanisms underlying stress responses of the freshwater snail, Pomacea canaliculata, exposed to different levels of arsenic.

Arsenic (As) pollution poses an important problem, but limited information is available about the physiological effects of As on freshwater invertebrates. Here, we investigated the physiological effects of chronic As exposure on Pomacea canaliculata, a freshwater invertebrate. High level of As (Ⅲ, 5 mg/L) inhibited the growth of P. canaliculata, whereas low level of As (Ⅲ, 2 mg/L) promoted growth. Pathological changes in shell and cellular ultrastructure due to As accumulation likely explain the growth inhibition at high As level. Low level of As simulated the expression of genes related to DNA replication and chitosan biosynthesis, potentially accounting for the growth promotion observed. High level of As enrichment pathways primarily involved cytochrome P450, glutathione, and arachidonic acid-mediated metabolism of xenobiotics. ATP-binding cassette (ABC) transporters, specifically the ABCB and ABCC subfamilies, were involved in As transport. Differential metabolites were mainly associated with the metabolism and biosynthesis of amino acids. These findings elucidate the dose-dependent effects of As stress on P. canaliculata growth, with low levels promoting and high levels inhibiting. Additionally, our findings also provide insights into As metabolism and transport in P. canaliculata.

Nitrogen addition accelerates litter decomposition and arsenic release of Pteris vittata in arsenic-contaminated soil from mine.

The arsenic (As) release from litter decomposition of As-hyperaccumulator (Pteris vittata L.) in mine areas poses an ecological risk for metal dispersion into the soil. However, the effect of atmospheric nitrogen (N) deposition on the litter decomposition of As-hyperaccumulator in the tailing mine area remains poorly understood. In this study, we conducted a microcosm experiment to investigate the As release during the decomposition of P. vittata litter under four gradients of N addition (0, 5, 10, and 20 mg N g-1). The N10 treatment (10 mg N g-1) enhanced As release from P. vittata litter by 1.2-2.6 folds compared to control. Furthermore, Streptomyces, Pantoea, and Curtobacterium were found to primarily affect the As release during the litter decomposition process. Additionally, N addition decreased the soil pH, subsequently increased the microbial biomass, as well as hydrolase activities (NAG) which regulated N release. Thereby, N addition increased the As release from P. vittata litter and then transferred to the soil. Moreover, this process caused a transformation of non-labile As fractions into labile forms, resulting in an increase of available As concentration by 13.02-20.16% within the soil after a 90-day incubation period. Our findings provide valuable insights into assessing the ecological risk associated with As release from the decomposition of P. vittata litter towards the soil, particularly under elevated atmospheric N deposition.

Biomonitoring of glyphosate and aminomethylphosphonic acid: Current insights and future perspectives.

Glyphosate is one of the most widely used herbicides globally, raising concerns about its potential impact on human health. Biomonitoring studies play a crucial role in assessing human exposure to glyphosate and providing valuable insights into its distribution and metabolism in the body. This review aims to summarize the current trends and future perspectives in biomonitoring of glyphosate and its major degradation product of aminomethylphosphonic acid (AMPA). A comprehensive literature search was conducted, focusing on studies published between January 2000 and December 2022. The findings demonstrated that glyphosate and AMPA have been reported in different human specimens with urine as the dominance. Sample pretreatment techniques of solid-phase and liquid-liquid extractions coupled with liquid/gas chromatography-tandem mass spectrometry have achieved matrix elimination and accurate analysis. We also examined and compared the exposure characteristics of these compounds among different regions and various populations, with significantly higher levels of glyphosate and AMPA observed in Asian populations and among occupational groups. The median urinary concentration of glyphosate in children was 0.54 ng/mL, which was relatively higher than those in women (0.28 ng/mL) and adults (0.12 ng/mL). It is worth noting that children may exhibit increased susceptibility to glyphosate exposure or have different exposure patterns compared to women and adults. A number of important perspectives were proposed in order to further facilitate the understanding of health effects of glyphosate and AMPA, which include, but are not limited to, method standardization, combined exposure assessment, attention for vulnerable populations, long-term exposure effects and risk communication and public awareness.

Hyperaccumulator Solanum nigrum L. Intercropping Reduced Rice Cadmium Uptake under a High-Bed and Low-Ditch Planting System.

Anthropogenic activities have raised cadmium (Cd) concentrations in agricultural soil, emerging as a primary catalyst for the decline in crop yield. Intercropping of two or several plants is one technique among many Cd phytoremediation techniques that has gained enormous attention recently. However, the impact of cultivation modes on Cd movement in rice plants when intercropped with heavy metal (HM) hyperaccumulator plants remains unclear. Thus, this study was designed to explore the effects of cultivation modes and the intercropping of rice with Solanum nigrum L. on rice growth and Cd uptake in Cd-contaminated soil. The experimental design encompassed five treatments: dry cultivation of monocultured rice, monocultured Solanum nigrum L., and intercropped rice-Solanum nigrum L.; flood cultivation of monocultured rice; and intercropped rice-Solanum nigrum L. in a high-bed and low-ditch planting system. The results revealed a significant increase in rice growth when intercropped with Solanum nigrum L., with a notable increase of 18.32 g∙plant-1 observed in rice biomass in dry cultivation under the intercropping system. In contrast, a more modest increase of 3.67 g∙plant-1 was observed in the high-bed and low-ditch intercropped rice-Solanum nigrum L. mode. The soil total Cd was higher in dry cultivation of monocultured rice and Solanum nigrum L. compared to intercropped rice/Solanum nigrum L.-cultivated soil, with lower values recorded for intercropped rice/Solanum nigrum L. under the high-bed and low-ditch planting system. In contrast, no significant effect was noted on soil exchangeable Cd content based on the planting pattern and cultivation mode. Intercropping with Solanum nigrum L. demonstrated a significant reduction of Cd content in various rice tissues, particularly in roots at the maturity stage, while Cd content was reduced across all rice tissues under the high-bed and low-ditch planting system. The Cd content in the stem, leaves, and bran of monocropped rice was higher compared to intercropped rice. This study suggests that the rice-Solanum nigrum L. intercropping system effectively reduces rice Cd uptake, particularly under the high-bed and low-ditch planting system.

A salting-out assisted liquid-liquid extraction method for 25 emerging pesticides in follicular fluid.

Emerging pesticides of neonicotinoids (NEOs) and "Universal Pesticides" (UPs) are a growing global concern due to their growing commercial importance and potential risks to human health. The currently available analytical methods for these pesticides in biomonitoring were usually tailored for limited number of analytes, or were time consuming and costly. In this study, an efficient and sensitive method for the analysis of 16 NEOs and nine UPs in human follicular fluid (FF) was developed by using a salting-out assisted liquid-liquid extraction (SALLE) method and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Method performance was evaluated by calibration linearity (r > 0.99), sensitivity at limits of quantification (0.01-0.50 ng/mL), accuracy at relative recoveries (81-117%) and precision at relative standard deviations (≤16%). The developed method was further validated by analyzing 21 human FF samples that were collected from a hospital in Guangzhou, China. Among the 25 study analytes, two NEOs and six UPs had their detection rates over 85% and medians at 0.048-0.808 ng/mL in the FF samples. Considering the well-known toxicity of these pesticides and their metabolites, it is urgent to figure out exposure profiles of study pesticides and potential reproductive risk for women. To the best of our knowledge, this study is the first to develop and apply the SALLE method in the extraction of 16 NEOs and nine UPs simultaneously in human FF.

The application of mixed stabilizing materials promotes the feasibility of the intercropping system of Gynostemma pentaphyllum/Helianthus annuus L. on arsenic contaminated soil.

Intercropping technology and stabilizing materials are common remediation techniques for soils contaminated with heavy metals. This study investigated the feasibility of the Gynostemma pentaphyllum (G. pentaphyllum)/Helianthus annuus L. (H. annuus) intercropping system on arsenic (As) contaminated farmland through field and pot experiments and the regulation of plant As absorption by the application of mixed stabilizing materials in this intercropping system. Field experiments demonstrated that intercropping with H. annuus increased the As concentration in G. pentaphyllum leaves to 1.79 mg kg-1 but still met the requirements of the national food standard of China (2 mg kg-1) (GB2762-2017). Meanwhile, G. pentaphyllum yield in the intercropping system decreased by 15.09%, but the difference was insignificant (P > 0.05). Additionally, the As bioconcentration (BCA) per H. annuus plant in the intercropping system was significantly higher than that in the monoculture system, increasing by 76.37% (P < 0.05). The pot experiment demonstrated that when granite powder, iron sulfate mineral, and "Weidikang" soil conditioner were applied to the soil collectively, G. pentaphyllum leaf As concentration in the intercropping system could be significantly reduced by 42.17%. Rhizosphere pH is the most crucial factor affecting As absorption by G. pentaphyllum in intercropping systems. When these three stabilizing materials were applied simultaneously, the As bioaccumulation (BCA) per H. annuus plant was significantly higher than that of normal intercropping treatment, which increased by 71.12% (P < 0.05), indicating that the application of these stabilizing materials significantly improved the As removal efficiency of the intercropping system. Dissolved organic carbon (DOC) concentration in the rhizosphere soil is the most pivotal factor affecting As absorption by H. annuus. In summary, the G. pentaphyllum-H. annuus intercropping model is worthy of being promoted in moderately As polluted farmland. The application of granite powder, iron sulfate mineral, and "Weidikang" soil conditioner collectively to the soil can effectively enhance the potential of this intercropping model to achieve "production while repairing" in the As polluted farmland.

Rainwater input reduces greenhouse gas emission and arsenic uptake in paddy rice systems.

This work aimed to test the hypothesis that rainwater-borne hydrogen peroxide (H2O2) can affect arsenic uptake by rice plants and emission of greenhouse gases in paddy rice systems. A mesocosm rice plant growth experiment, in conjunction with rainwater monitoring, was conducted to examine the effects of rainwater input on functional groups of soil microorganisms related to transformation of arsenic, carbon and nitrogen as well as various arsenic species in the soil and plant systems. The fluxes of methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) were measured during selected rainfall events. The results showed that rainwater-borne H2O2 effectively reacted with Fe2+ present in paddy soil to trigger a Fenton-like reaction to produce •OH. Both H2O2 and •OH inhibited As(V)-reducing microbes but promoted As(III)-oxidizing microbes, leading to a net increase in arsenate-As that is less phytoavailable compared to arsenite-As. This impeded uptake of soil-borne As by the rice plant roots, and consequently reduced the accumulation of As in the rice grains. The input of H2O2 into the soil caused more inhibition to methanogens than to methane-oxidizing microbes, resulting in a reduction in CH4 flux. The microbes mediating the transformation of inorganic nitrogen were also under oxidative stresses upon exposure to the rainwater-derived H2O2. And the limited conversion of NO3- to NO played a crucial role in reducing N2O emission from the paddy soils. The results also indicated that the rainwater-borne H2O2 could significantly affect other biogeochemical processes that shape the wider ecosystems, which is worth further investigations.

Neonicotinoid insecticides and their metabolites: Specimens tested, analytical methods and exposure characteristics in humans.

The use of neonicotinoid insecticides (NEOs) has been rising globally due to their broad-spectrum insecticidal activity, unique mode of neurotoxic action and presumed low mammalian toxicity. Given their growing ubiquity in the environment and neurological toxicity to non-target mammals, human exposure to NEOs is flourishing and now becomes a big issue. In the present work, we demonstrated that 20 NEOs and their metabolites have been reported in different human specimens with urine, blood and hair as the dominance. Sample pretreatment techniques of solid-phase and liquid-liquid extractions coupled with high performance liquid chromatography-tandem mass spectrometry have successfully achieved matrix elimination and accurate analysis. We also discussed and compared exposure characteristics of these compounds among types of specimens and different regions. A number of important knowledge gaps were also identified in order to further facilitate the understanding of health effects of NEO insecticides, which include, but are not limited to, identification and use of neuro-related human biological samples for better elucidating neurotoxic action of NEO insecticides, adoption of advanced non-target screening analysis for a whole picture in human exposure, and expanding investigations to cover non-explored but NEO-used regions and vulnerable populations.

Intercropping efficiency of Pteris vittata with two legume plants: Impacts of soil arsenic concentrations.

Intercropping of hyperaccumulators with crops has emerged as a promising method for remediating arsenic (As)-contaminated soil in agroecosystems. However, the response of intercropping hyperaccumulators with different types of legume plants to diverse gradients of As-contaminated soil remains poorly understood. In this study, we assessed the response of plant growth and accumulation of an As hyperaccumulator (Pteris vittata L.) intercropped with two legume plants to three gradients of As-contaminated soil. Results indicated that soil As concentration had a substantial effect on the As uptake by plants. P. vittata growing in slightly As-contaminated soil (80 mg kg-1) exhibited higher As accumulation (1.52-5.49 folds) than those in higher As-contaminated soil (117 and 148 mg kg-1), owing to the lower soil pH in high As-contaminated soil. Intercropping with Sesbania cannabina L. increased As accumulation in P. vittata by 19.3%- 53.9% but decreased in intercropping with Cassia tora L. This finding was attributed to S. cannabina providing more NO3--N to P. vittata to support its growth, and higher resistance to As. The decreased rhizosphere pH in the intercropping treatment also resulted in the increased As accumulation in P. vittata. Meanwhile, the As concentrations in the seeds of the two legume plants met the national food standards(<0.5 mg kg-1). Therefore, the intercropping P. vittata with S. cannabina is a highly effective intercropping system in slightly As-contaminated soil and provides a potent method for As phytoremediation.

Remediation effect and mechanism of low-As-accumulating maize and peanut intercropping for safe-utilization of As-contaminated soil.

Phytoremediation by intercropping is a potential method to realize both production and remediation. Maize and peanut are the main crops planted in arsenic(As) contaminated areas in south China and vulnerable to As pollution. Experiments were conducted on arsenic-polluted soil with low As-accumulating maize monoculture (M), peanut monoculture (P), and intercropping with different distances between the maize and peanut (0.2 m, 0.35 m, and 0.5 m, recorded as MP0.2, MP0.35, and MP0.5, respectively). The results indicated that the As content in the maize grains and peanut lipids in the intercropping system decreased significantly, meeting the food safety standard of China (GB 2762-2017). Moreover, the land equivalent ratio (LER) and heavy metal removal equivalence ratio (MRER) of all intercropping treatments were greater than 1, indicating that this intercropping agrosystem has the advantage of production and arsenic removal, among which the yield and LER of MP0.35 treatment were the highest. Additionally, the bioconcentration factors (BCF) and translocation factor (TF) of MP0.2 increased by 117.95% and 16.89%, respectively, indicating that the root interaction affected the absorption of As in soil by crops. This study preliminarily demonstrated the feasibility of this intercropping system to safely use and remedy arsenic-contaminated farmland during production.

Phytoremediation by intercropping is a potential method to realize both production and remediation. Maize and peanuts are the main crops planted in As-contaminated areas and easily polluted by As. This study preliminarily demonstrated the feasibility of this intercropping system to safely use and remedy arsenic-contaminated farmland during production.

Effects of different planting distances and fertilizer use on the remediation of farmland contaminated with Cd by intercropping Cucurbita moschata and Amaranthus hypochondriacus L.

Selecting suitable agronomic measures can strengthen the application of intercropping in the remediation of cadmium (Cd)-contaminated soil. In this study, the effects of different planting densities and fertilizer applications on the crop growth and Cd absorption of a pumpkin (Cucurbita moschata)-Amaranthus hypochondriacus L. intercropping system was determined. The goal was to provide enhanced means and a scientific basis for the promotion and application of this intercropping system. The Cd content of pumpkin in different planting systems was lower than the national food safety standard (0.05 mg kg-1). In the IN-1 (4 pumpkin plants intercropped with 200 A. hypochondriacus plants) and IN-2 (4 pumpkin plants intercropped with 400 A. hypochondriacus plants) intercropping systems, the bioconcentration amount (BCA) per plant of Cd in A. hypochondriacus increased by 32.43% and 25.25%, respectively, compared with that of the monocropping system (P < 0.05). The IN-2 system had the highest equivalent ratio of heavy metal removal (3.08), indicating that this model had a substantial advantage for removing Cd. The land equivalent ratio of IN-1 (2.89) and IN-2 (2.60) was significantly higher than that of other intercropping systems, indicating that these two models had obvious yield advantages. In our study, chicken manure was the best at promoting the growth and yield of the two plants and sludge treatment significantly enhance Cd absorption of A. hypochondriacus. In general, intercropping four pumpkin plants with 400 A. hypochondriacus plants and applying chicken manure fertilizer can strengthen the application of this intercropping system in Cd-contaminated soil.

Occurrence of emerging bisphenol S analogues in urine from five occupational populations in South China.

Bisphenol S (BPS) and its 11 emerging analogues were investigated in 325 urine samples from five occupational populations in South China. Besides BPS, ten emerging BPS analogues were newly identified and detected in the urine. It should be noted that urinary concentrations of dominant BPS analogues of 2,4'-bis(hydroxyphenyl)sulfone (2,4-BPS), bis(3-allyl-4-hydroxyphenyl)sulfone (TGSA) and diphenylsulfone (DPS) were 1.1-2.3 times higher than that of BPS, with overall detection frequencies at 74-91 %. The median sum concentrations of the target 12 bisphenols (ng/mL) were found highest in urine from cashiers (1.12), followed by water plant staffs (0.994), teachers (0.552), doctors (0.408) and power plant staffs (0.333). The composition profile of the urinary dominant bisphenols was occupational-dependent, with 2,4-BPS accounting for 45-73 % in cashiers and power plant staffs, and with DPS and TGSA for 74-82 % among doctors, teachers and water plant staffs. Significant correlations were found among the most frequently detected bisphenols in cashiers, indicating their common application and emission pathways. The median exposures based on estimated daily intakes (EDIs, ng/kg bw/day) for the 12 bisphenols in cashiers and water plant staffs (31.6-35.6) were 1.8-3.4 times higher than those of teachers, doctors and power plant staffs (10.6-17.5). This is the first study to identify multiple emerging BPS analogues in urine from occupational populations, especially cashiers and water plant staffs.

Dose-dependent inhibitory effects of glyphosate on invasive Pomacea canaliculata reproductive and developmental growth under oxidative deposition.

Glyphosate (GLY) is the most widely used herbicide worldwide, and its effects on animals and plants have attracted increasing attention. In this study, we explored the following: (1) the effects of multigenerational chronic exposure to GLY and H2O2, alone or in combination, on the egg hatching rate and individual morphology of Pomacea canaliculata; and (2) the effects of short-term chronic exposure to GLY and H2O2, alone or in combination, on the reproductive system of P. canaliculata. The results showed that H2O2 and GLY exposure had distinct inhibitory effects on the hatching rate and individual growth indices with a substantial dose effect, and the F1 generation had the lowest resistance. In addition, with the prolongation of exposure time, the ovarian tissue was damaged, and the fecundity decreased; however, the snails could still lay eggs. In conclusion, these results suggest that P. canaliculata can tolerate low concentrations of pollution and in addition to drug dosage, the control should focus on two time points, the juvenile and early stage of spawning.

Synergistic removal of sulfamethoxazole and dimethyl phthalate by five constructed wetland substrates.

Frequent detection and joint toxicity of sulfonamides (SAs) and phthalate acid esters (PAEs) in water environment have caused serious health and safety problems that can be reduced by vertical flow constructed wetland (VFCW). However, it remains unclear what kind of substrate used in VFCW can synergistically remove SAs and PAEs. In this study, it was determined if biochar, zeolite, vermiculite, peat and sand synergistically removed sulfamethoxazole (SMX) and dimethyl phthalate (DMP) as representatives of SAs and PAEs by using batch and column experiments. The batch experiments showed that pseudo-second-order and intraparticle diffusion kinetics and Freundlich isotherm could better describe the synergistic adsorption of SMX and DMP on each substrate. SMX promoted hydrophobic interaction between DMP and each substrate so that low concentration DMP almost was adsorbed completely at neutral pH. Both neutral and alkaline pH conditions were favorable for synergistic adsorption of SMX and DMP on each substrate. The column experiments showed that removal of SMX or DMP in VFCW by substrate adsorption alone was limited with run time increasing, but SMX and DMP were effectively removed with run time increasing when loaded with simulated wastewater, SMX and DMP. The VFCW not only removed 94.7% SMX and 91.8% DMP after running 50 d, but also improved total nitrogen removal. In conclusion, these results strongly suggest that biochar, zeolite, vermiculite, peat and sand filled in VFCW can synergistically remove SMX and DMP.

Salinity elevates Cd bioaccumulation of sea rice cultured under co-exposure of cadmium and salt.

Salt-tolerant rice (sea rice) is a key cultivar for increasing rice yields in salinity soil. The co-existence of salinity and cadmium (Cd) toxicities in the plant-soil system has become a great challenge for sustainable agriculture, especially in some estuaries and coastal areas. However, little information is available on the Cd accumulating features of sea rice under the co-stress of Cd and salinity. In this work, a hydroponic experiment with combined Cd (0, 0.2, 0.8 mg/L Cd2+) and saline (0, 0.6%, and 1.2% NaCl, W/V) levels and a pot experiment were set to evaluate the Cd toxic risks of sea rice. The hydroponic results showed that more Cd accumulated in sea rice than that in the reported high-Cd-accumulating rice, Chang Xianggu. It indicated an interesting synergistic effect between Cd and Na levels in sea rice, and the Cd level rose significantly with a concomitant increase in Na level in both shoot (r = 0.54, p < 0.01) and root (r = 0.66, p < 0.01) of sea rice. Lower MDA content was found in sea rice, implying that the salt addition probably triggered the defensive ability against oxidative stress. The pot experiment indicated that the coexistent Cd and salinity stress further inhibited the rice growth and rice yield, and the Cd concentration in rice grain was below 0.2 mg/kg. Collectively, this work provides a general understanding of the co-stress of Cd and salinity on the growth and Cd accumulation of sea rice. Additional work is required to precisely identify the phytoremediation potential of sea rice in Cd-polluted saline soil.

Luffa cylindrica Intercropping with Semen cassiae-A Production Practice of Improving Land Use in Soil Contaminated with Arsenic.

In recent years, research on the safe utilization and green remediation of contaminated soil by intercropping has become common. In this study, the growth of an intercropping system of Luffa cylindrica-Semen cassiae in soil contaminated with medium amounts of arsenic (As) was studied using field (91.60 mg kg-1) and pot (83.34 mg kg-1) experiments. The field experiments showed that intercropping significantly increased the yield per plant of L. cylindrica by 27.36%, while the yield per plant of S. cassiae decreased by 21.66%; however, this difference was not significant. Intercropping reduced the concentration of As in all organs of L. cylindrica but increased the concentration of As in all parts of S. cassiae. The accumulation of As per plant of L. cylindrica was reduced by 20.72%, while that in a single plant of S. cassiae was increased by 201.93%. In addition, the concentration of As in the fruit of these two crops in these two planting modes was low enough to meet the National Food Safety Standard of China (GB2762-2017). In addition, the land equivalent ratio and As metal removal equivalent ratio of the intercropping mode was 1.03 and 2.34, indicating that the intercropping mode had advantages in land use and As removal. In the pot experiment, the biomass and As concentration of L. cylindrica and S. cassiae were roughly consistent with those in the field experiment. During the sampling period, intercropping reduced the concentration of As in the rhizosphere soil solution of L. cylindrica by 3.1-23.77%, while it increased the concentration of As in the rhizosphere soil solution of S. cassiae by 13.30-59.40%. The changes in pH and redox potential were also closely related to the content of water-soluble As in the rhizosphere environment, which affects the absorption of As by plants. In general, the L. cylindrica-S. cassiae intercropping system is a planting mode that can effectively treat soil that is moderately contaminated with As and remove it from the soil to an extent.