Influencing factors and risk assessment of phthalate ester pollution in the agricultural soil on a tropical island.

Phthalate esters (PAEs) are widely prevalent in agricultural soil and pose potential risks to crop growth and food safety. However, the current understanding of factors influencing the behavior and fate of PAEs is limited. This study conducted a large-scale investigation (106 sites in 18 counties with 44 crop types) of 16 types of PAEs on a tropical island. Special attention was given to the impacts of land use type, soil environmental conditions, agricultural activity intensity, and urbanization level. The health risks to adults and children from soil PAEs via multiple routes of exposure were also evaluated. The results showed that the mean concentration of PAEs was 451.87 ± 284.08 µg kg-1 in the agricultural soil. Elevated agricultural and urbanization activities contributed to more pronounced contamination by PAEs in the northern and southern regions. Land use type strongly affected the concentration and composition of PAEs in agricultural soils, and the soil PAE concentration decreased in the order of vegetable fields, orchards, paddy fields, and woodlands. In paddy fields, di-isobutyl phthalate and di-n-butyl phthalate made more substantial contributions to the process through which the overlying water inhibited volatilization. Soil microplastic abundance, pesticide usage, crop yield, gross domestic product, and distance to the nearest city were calculated to be the major factors influencing the concentration and distribution of PAEs. Soil pH, organic matter content, microplastic abundance and the fertilizer application rate can affect the adsorption of PAEs by changing the soil environment. A greater risk was detected in the northern region and paddy fields due to the higher soil PAE concentrations and the dietary structure of the population. This study reveals important pathways influencing the sources and fate of PAE pollution in agricultural soils, providing fundamental data for controlling PAE contamination.

Farmland Microhabitat Mediated by a Residual Microplastic Film: Microbial Communities and Function.

How the plastisphere mediated by the residual microplastic film in farmlands affects microhabitat systems is unclear. Here, microbial structure, assembly, and biogeochemical cycling in the plastisphere and soil in 33 typical farmland sites were analyzed by amplicon sequencing of 16S rRNA genes and ITS and metagenome analysis. The results indicated that residual microplastic film was colonized by microbes, forming a unique niche called the plastisphere. Notable differences in the microbial community structure and function were observed between soil and plastisphere. Residual microplastic film altered the microbial symbiosis and assembly processes. Stochastic processes significantly dominated the assembly of the bacterial community in the plastisphere and soil but only in the plastisphere for the fungal community. Deterministic processes significantly dominated the assembly of fungal communities only in soil. Moreover, the plastisphere mediated by the residual microplastic film acted as a preferred vector for pathogens and microorganisms associated with plastic degradation and the nitrogen and sulfur cycle. The abundance of genes associated with denitrification and sulfate reduction activity in the plastisphere was pronouncedly higher than that of soil, which increase the potential risk of nitrogen and sulfur loss. The results will offer a scientific understanding of the harm caused by the residual microplastic film in farmlands.

Selective stepwise adsorption for enhanced removal of multi-component dissolved organic chemicals from petrochemical wastewater.

The coexistence of multi-component dissolved organic chemicals causes tremendous challenge in purifying petrochemical wastewater, and stepwise selective adsorption holds the most promise for enhanced treatments. This study is designed to enhance the removal of multiple dissolved organic chemicals by stepwise adsorption. Special attention is given to the selective removal mechanisms for the major pollutant N,N-dimethylformamide (DMF), the sensitive pollutant fluorescent dissolved organic matter (FDOM) and other components. The results indicated that the combination of coal activated carbon and aluminum silica gel produced a synergistic effect and broke the limitation of removing only certain pollutants. Combined removal rates of 80.5 % for the dissolved organic carbon and 86.7 % for the biotoxicity in petrochemical wastewater were obtained with the enhanced two-step adsorption. The adsorption performance of both adsorbents remained stable even after five cycles. The selective adsorption mechanism revealed that hydrophobic organics such as DMF was adsorbed by the macropores of coal activated carbon, while the FDOM was eliminated by π-π stacking, electrostatic interaction and hydrophobic interaction. The hydrophilic organics were removed by the mesopores of aluminum silica gel, the silica hydroxyl groups and hydrophilic interaction. This study provides a comprehensive understanding of the selective adsorption mechanism and enhanced stepwise removal of multiple pollutants in petrochemical wastewater, which will guide the deep treatment of complex wastewater.

Suppression of performance of activated carbon filter due to residual aluminum accumulation.

Extending the lifetime of granular activated carbon (GAC) filters with no significant loss in their effectiveness is a considerable challenge for drinking water supply utilities. However, the effects of residual Al from coagulants on GAC performance are rarely considered. Herein, in-service GAC samples obtained from full-scale water treatment plants were investigated to evaluate the amount of accumulated Al. Although the Al concentration in water was two to three times lower than the Ca concentration, Al exhibited considerable accumulation (second to Ca accumulation) in in-service GAC samples (0.68-8.63 mg g-1). Surface characterization results indicated that Al accumulation could have been caused by the co-precipitation of Al with Ca and Si to form Ca4Al2Si3O10·H2O and Ca4Al6O12SO4, self-precipitation or complexion with -OH/-COOH on the GAC or biofilm surfaces. Correlation analysis of the accumulated Al and GAC properties implied that Al accumulation considerably reduced the surface area of GAC by ∼30%. Lab simulation experiments indicated that the removal of dissolved organic matter was reduced by 6-10% when additional Al was loaded. In addition, results showed that the residual Al (up to 200 µg L-1) considerably affected the extracellular polymeric substance component and microorganism community structure. In summary, strict control of residual Al is beneficial for maintaining the efficacies of GAC and biologically activated carbon.

Efficiency and mechanism of micro- and nano-plastic removal with polymeric Al-Fe bimetallic coagulants: Role of Fe addition.

The occurrence of microplastics (MPs) and even nanoplastics (NPs) in tap water has raised considerable attention. As a pre-treatment and also the most important process in drinking water treatment plants, coagulation has been widely studied to remove MPs, but few studies focused on the removal pattern and mechanism of NPs, especially no study paid attention to the coagulation enhanced by prehydrolysed Al-Fe bimetallic coagulants. Therefore, in this study, polymeric species and coagulation behaviour of MPs and NPs influenced by Fe fraction in polymeric Al-Fe coagulants were investigated. Special attention was given to the residual Al and the floc formation mechanism. The results showed that asynchronous hydrolysis of Al and Fe sharply decreases the polymeric species in coagulants and that the increase of Fe proportion changes the sulfate sedimentation morphology from dendritic to layered structures. Fe weakened the electrostatic neutralization effect and inhibited the removal of NPs but enhanced that of MPs. Compared with monomeric coagulants, the residual Al decreased by 17.4 % and 53.2 % in the MP and NP systems (p < 0.01), respectively. With no new bonds detected in flocs, the interaction between micro/nanoplastics and Al/Fe was merely electrostatic adsorption. According to the mechanism analysis, sweep flocculation and electrostatic neutralization were the dominant removal pathways of MPs and NPs, respectively. This work provides a better coagulant option for removing micro/nanoplastics and minimizing Al residue, which has promising potential for application in water purification.

Identification of factors influencing the microplastic distribution in agricultural soil on Hainan Island.

Microplastics (MPs) are ubiquitous in agricultural soils, but to what extent and how environmental factors determine the source and fate of MPs in agricultural soils is not clear. In this study, Hainan Island, which has different climatic conditions, altitudes, and land uses across the island, was selected to investigate the MPs abundance and the shape, size, color, and polymer type of the MPs in agricultural soils. The main focus was on the role of land use type and the identification of environmental influencing factors. The results showed that MPs were detected in all the soil samples across the island, with an abundance range of 20 to 6790 items kg-1 and an average of 417 items kg-1. Fragments (46.8 %), MPs smaller than 0.5 mm (37.8 %), black MPs (48.3 %), and polypropylene MPs (56.8 %) were observed as the dominant MPs species. Significantly higher MPs abundance was found in mulched arable land, and higher contents of fibers and fragments were observed in woodland and paddy lands, respectively. With correlation and redundancy analyses, soil pH, soil organic matter content, and average annual temperature were found to be the main factors influencing the biotic/abiotic fragmentation of MPs. The regional population density, including tourism represented by the night light index, affects the input process of MPs. MPs transport and deposition were found to be affected by altitude, annual precipitation, and soil moisture content. This study represents the first large-scale study of MPs contamination in island agricultural soils and provides important data on the distribution, transport, and fate of MPs.

Effects of electrostatic neutralization of Keggin Fe13 on the removal of micro and nano plastic.

The successful preparation and identification of Keggin-structure Fe13 clusters in recent years further enriched the potential application scenarios of ferric coagulants. Comparing the coagulation efficiencies and mechanisms of Fe13 in the removal of nano/microplastics with conventional polymeric Al13 and monomeric Al/Fe, this work aimed to elucidate the coagulation behaviour of Fe13 compared with the traditional mono ferric coagulant, which has the coagulation applied bottleneck of quick and violet hydrolysis. The results showed that Fe13 has a similar electrostatic neutralization potential to Al13, which could keep a positively charged species, especially in acid conditions. The Fe13 species has a selective removal potential toward the microplastics with a polar functional group like ester. Moreover, Fe13 could hydrolyze to form active sol-gel hydroxides in neutral and alkalinity conditions, which is like the behaviour of traditional monomeric Fe coagulants but seldom restabilization. The electrostatic neutralization of Fe13 could enhance the removal of nano plastic from - 25-75% compared with monomeric Fe at pH 4. The higher floc density as a monomeric Fe coagulant and better electrostatic neutralization potential of Keggin Fe13 posed a good prospect for Fe13 to replace the monomeric Fe coagulants in conventional coagulation.

A review of freshwater benthic clams (Corbicula fluminea): Accumulation capacity, underlying physiological mechanisms and environmental applications.

Asian clams (Corbicula fluminea) have been extensively applied in biomonitoring and other environmental fields based on their high enrichment capacity and rapid response to pollutants. This review first summarizes the kinetic process of metals and organic pollutants enriched by C. fluminea and discusses the environmental behavior and application. The accumulation ability of Cu, Zn, and Mn were significantly higher than that of other metals, which were attributed to their high uptake rate constant and low elimination rate constant. The visceral mass was found to be the major burden tissue. However, large knowledge gaps existed regarding the accumulation capacity of C. fluminea for organic pollutants and nanoparticles. Moreover, physiological mechanisms underlying the accumulation of environmental pollutants were proposed. C. fluminea can improve the niche of benthic algae by ingesting pelagic algae, mitigating water eutrophication. It can also remove pathogens and parasites based on the biological assimilation of nonspecific immunity, interrupting disease transmission. The novel insight into the application of C. fluminea in wastewater treatment further broadens the range of pest management strategies and offers the feasibility of blocking the spread of invasive bivalves.

Microplastic bioaccumulation in estuary-caught fishery resource.

The environmental behavior of microplastics (MPs) in estuaries with saline and freshwater intersections is extremely complex. This increases the chance of MP ingestion by fishery resources, posing potentially tremendous health risks for humans. Herein, a total of 105 fishes from 14 different species, and 86 crustaceans (including shrimps and crabs) from five different species were sampled in the Yangtze River estuary and offshore, and MP bioaccumulation, accumulative organ, and the influencing factors were comprehensively studied. The results elucidated that MP accumulation in benthos was significantly higher than that in pelagic animals due to the lower acceptance threshold, assimilation efficiency and egestion rate for benthos. The MP content in crustaceans with the burrowing favoring the MP retention was significantly higher than that in fishes. MPs ingested by fish can accumulate in skin, gills and viscera rather than muscles. Most MPs accumulated in fishery resources were cellulose and polyethylene terephthalate characterized by black and gray fibrous and lengths ranging from 0.1 mm to 1 mm. The gill retention capacity of pelagic fish to smaller-size (<0.1 mm) MPs was pronouncedly stronger than that of benthic fish. It was more accurate to assess the ecological risk of MPs in terms of the maximum size of MPs accumulated in organisms. Compared with the offshore area, the incidence of MP uptake was higher in the estuary owing to anthropogenic impacts. This study helps understand the transfer of MPs in aquatic food webs and offers a foundation for assessing the risk of human exposure to MPs.

Synthesis and Characterization of Compounds Based on Carbazole and Sulfone Groups.

Two compounds containing carbazole and sulfone groups with different alkyl chain lengths have been designed and synthesized. The sulfone group has strong absorption characteristics and the alkoxy chain and carbazole group are electron-rich, forming D-δ-A-type symmetrical molecules. The molecules have the characteristics of charge transfer and high thermal stability, and the molecules stack to form a layered staggered stack, reducing the intermolecular π-π interactions. The target compounds also exhibit strong ultraviolet-fluorescent emission in the solid state at room temperature, and they are expected to be good luminescent materials.

Toxicity effects of ciprofloxacin on biochemical parameters, histological characteristics, and behaviors of Corbicula fluminea in different substrates.

Antibiotic toxicity and antibiotic resistance have become significant challenges to human health. However, the potential ecotoxicity of sediment-associated antibiotics remains unknown. In this study, biochemical responses, histological changes, and behavioral responses of Corbicula fluminea exposed to sediment-associated ciprofloxacin (CIP) were systemically investigated. Special attention was paid to the influence of different substrate types. Biochemical analyses revealed that the balance of the antioxidant system was disrupted, eventually leading to oxidative damage to the gills and digestive gland with increasing CIP concentration. Severe histopathological changes appeared along with the oxidative damage. An enlargement of the tubule lumen and thinning of the epithelium in the digestive gland were observed under exposure to high CIP concentrations (0.5 and 2.5 µg/g CIP). In a behavioral assay, the filtration rate of C. fluminea in high concentration exposure groups was clearly inhibited. Moreover, from the integrated biomarker response (IBR) index, the toxicity response gradients of the digestive gland (no substrate--NOS > Sand > Sand and kaolinite clay-- SKC > Sand, kaolinite clay, and organic matter--SCO) and gills (NOS > SCO > SKC > Sand) were different among substrate exposure groups. The most serious histopathological damage and highest siphoning inhibition were observed in the NOS group. The changes in the morphological structure of digestive gland cells in C. fluminea were similar in the other three substrate groups. The inhibition of the filtration rate in the higher concentration groups decreased in the order Sand > SKC > SCO.

Nanoplastic-Induced Genotoxicity and Intestinal Damage in Freshwater Benthic Clams (Corbicula fluminea): Comparison with Microplastics.

With the wide application of plastics in daily life, nanoplastics (NPs) are ubiquitous in freshwater environments. However, to date, few studies have focused on the mechanism underlying the toxicity of NPs, and the differences between this mechanism and that governing the toxicity of MPs have also not been thoroughly characterized. In this study, the genotoxicity, intestinal damage, and intestinal flora in Corbicula fluminea exposed to micro/nanoplastics were investigated through RNA sequencing, histopathology, and 16S rRNA sequencing, respectively. Significant differences in differentially expressed genes (DEGs) were observed between MP and NP exposure groups. It was observed that NPs preferentially elicited the process related to cellular components and triggered the apoptosis through the mitochondrial pathway in various tissues, especially in indirectly contacted tissues, while MPs induced the innate immune response and activated the complement and coagulation cascades (complement system) pathway. Both MPs and NPs can induce an inflammatory response and cause epithelial damage in the intestines, and they can notably change the gut microbial community structure. However, the abundance of pathogenic bacteria (e.g., Mycoplasma) was observed to increase only in the MP-treated group, which exacerbated intestinal damage. Unlike MPs, the effect of NPs on the intestinal microflora was highly limited, while NPs elicited more severe damage to the intestinal mucosal barrier. The results of this study may help to elucidate the toxicity mechanisms governing the responses of bivalves to MPs and NPs and to evaluate the detriment of MPs and NPs to the benthic ecosystem.

The identification of Al nanoclusters by electrospray ionization mass spectrometry (ESI-MS).

Lacking consolidated qualitative and quantitative analysis methods of Al nanoclusters in aqueous, the distributions and concentrations of each Al species could not be revealed with single method before or after coagulation, which limited the development of environmental Al clusters control. As the ESI-MS applied in the inorganic cluster's identification tentatively, the deficient identification of Al species could be analyzed qualitatively and quantitatively with mass spectrum directly. Although many studies have applied the ESI-MS to analyze Al species in aqueous, the experimental conditions were not compared and not reached an agreement. Therefore, this work is the first study to review the methodology developments of ESI-MS in Al identification and to summarize the qualitative and quantitative analysis promoted by ESI-MS. The principle and rationality of quantitative ESI-MS method were inducted and discussed from the prospects of resolving mass spectrum assignment and transforming species in ionization. The qualitative ESI-MS results in previous studies were also analyzed by quantitative ESI-MS analysis in this work. The quantitative Al species results are accordant with the distribution results concluded via Al-Ferron and 27Al NMR methods. The identification principles and instrumental parameters were summarized and unified, which would give hints to further methodological applications and modifications. This study puts forward the further possibilities and prospects of ESI-MS applied in the transformation and in-situ identification of Al13 nanocluster in aqueous.

Impact of water source mixture and population changes on the Al residue in megalopolitan drinking water.

This study establishes a new understanding of the contributions of Al residue in a megalopolitan drinking water supply system with mixed water sources. The different influences and contributions of foreign water source, resident migration and season changing to Al residue in drinking water were investigated. Especially, the role of Southern water transferred over 1200 km via the South-to-North Water Diversion Project in the Al residue of drinking water supply system of a northern megalopolitan were revealed for the first time. Comparisons of big data on Al residue in the water supply system with sole and mixed water sources showed that the introduction of Southern water enhanced the Al residue in drinking water by over 35%. The world's largest annual residents' migration during Chinese Lunar New Year and the changes of season affect the water pipework hydrodynamics, which were embodied as the periodic changes of particulate aluminium and the relations with resident's temporal-spatial distribution in the megalopolitan. Because of the differences in water quality, Southern water promotes the release of historically deposited Al and facilitates the cleaning of old pipes.

Impacts of nanoplastics on bivalve: Fluorescence tracing of organ accumulation, oxidative stress and damage.

The outcomes of this research offer novel insights into the toxic effects of nanoparticles (i.e., nanoplastics or other nanomaterials) on the benthos. Herein, this study aimed to evaluate the accumulation pathway, distribution characteristics and potential biotoxicity of polystyrene nanoplastics in C. fluminea. The results revealed that nanoplastics could accumulate in the mantle through adherence, in the visceral mass through ingestion and in the gill through respiration. The gill, intestine and stomach were the main accumulation organs for nanoplastics. The aggregation of nanoplastics was observed in C. fluminea, which may exacerbate their biotoxicity. Moreover, oxidative stress was observed in the visceral mass, gill and mantle. Liver damage, neurotoxicity and intestinal inflammation were caused by imbalance in the antioxidation system. Analysis of IBR values showed that the visceral mass had a more effective response to oxidative stress than the gill and mantle after exposure to nanoplastics.

Spatial distribution, source apportionment and risk assessment of antibiotics in the surface water and sediments of the Yangtze Estuary.

The "pseudo-durability" of antibiotics in estuaries is gaining increasing interest, especially in the Yangtze Estuary, a vital water supply source for the Shanghai city. To clearly describe the pollution level and risk of antibiotics in this estuary, the contents of 8 typical antibiotics in the surface water and the sediment along the nearshore zone and in the estuarine channel in the estuary were comprehensively analyzed. The results revealed that sulfonamides and tetracycline are the predominant antibiotics in the surface water, while tetracyclines and fluoroquinolones are the dominant ones in the sediments. The ranges of the eight antibiotic concentrations between the nearshore zone (not detected to 7.06 ng/L for water, below LOD to 10.94 ng/g for sediment) and the estuarine channel (not detected to 8.46 ng/L for water, not detected to 14.84 ng/g for sediment) showed no notable differences, but the degree of scatter was different for each antibiotic. The spatial distribution was different for each antibiotic in the north branch and the south branch; higher values for most of the target antibiotics were observed in the south branch of the estuary. The distribution and source analysis from a GIS map using the kriging method indicated that runoff input and the antibiotic residues from aquaculture were the two major sources of the antibiotic pollution in the Yangtze Estuary. A risk assessment of the individual antibiotic exposure in the surface water showed that sulfamethoxazole, ofloxacin and ciprofloxacin, tetracycline and oxytetracycline, and sulfadiazine, roxithromycin and erythromycin in this area exhibited a medium risk, low risk and almost no risk to the selected aquatic microorganisms, respectively.

A Simple and Rapid Fluorescent Probe for Detection of Cr3+ Based on a Coumarin Schiff Base in Aqueous Solution.

A new Cr3+ probe was synthesized using simple Schiff base reaction, which showed prominent fluorescence increasing switch before and after addition Cr3+. The probe proved to have excellent properties, based on both UV-vis absorption and fluorescence spectra. Those properties included high switching performance, good selectivity, and small interference with other metal ions. The fluorescent change mechanism of the probe was attributed to the combined action between the restricted C=N isomerization and the suppression of highly efficient photo-induced electron transfer (PET) process. Moreover, this fluorescence probe for Cr3+ detection also has great potential for bioimaging of cancer cells.

Enhanced adsorption of anionic toxic contaminant Congo Red by activated carbon with electropositive amine modification.

Anionic ionizable toxic organic contaminants, such as pesticides, herbicides, pharmaceuticals and dyestuffs, are widely detected in aqueous and can exert specific toxicity in organisms. They are hard removed by traditional adsorbents with negative surface charges and hydrophilic property. To solve that bottleneck problem, this study synthesized a carbon-based electropositive absorbent via surface activation and radical impregnation. The monolayer adsorption capacity and favorability of the novel adsorbent increased 4.2 and 16 times compared with activated carbon, evaluated by Congo Red. The adsorption kinetics could be described by pseudo-second-order equation, dominated by chemisorption and shortened 75% equilibrium time. The excellent adsorption behavior of synthesized material was attributed to created and bridged electropositive quaternary ammonium structure onto activated carbon, identified with XPS and FT-IR. Additionally, the abundant mesoporous structures of modified carbon provide more tunnels and facilitate adsorption of Congo Red, identified by AutoSorb-iQ. With the batch experiments of pH and ion strength influence, the absorbent behaved well in acidic low ion strength conditions and attenuated by coexisting cations. The study provides a high efficiency, large capacity and low cost materials to remove anionic ionizable organic contaminants in aqueous.

Biological toxicity response of Asian Clam (Corbicula fluminea) to pollutants in surface water and sediment.

As a typical test species, Asian Clam (Corbicula fluminea) is widely used in the identification and evaluation of freshwater toxicity. This study provides a summary of the research published from 1979 to 2018. The focus was on the bioaccumulation, morphological and behavioral changes, and biochemical index alterations of Corbicula fluminea to target pollutants (i.e., ammonia, metal(loid)s, and organic chemicals) in surface water and sediment. The applications on the evaluation of actual aquatic pollution, determination of toxicological mechanisms, prediction of toxicity, and bioremediation are also specifically discussed. The primary purpose is to facilitate the comprehensive understanding and accurate application of Corbicula fluminea in freshwater ecotoxicological studies.

Heavy metal partitioning of suspended particulate matter-water and sediment-water in the Yangtze Estuary.

The partitioning of ten heavy metals (As, Cd, Co, Cr, Cu, Hg, Ni, Pb, Sb, and Zn) between the water, suspended particulate matter (SPM), and sediments in seven channel sections during three hydrologic seasons in the Yangtze Estuary was comprehensively investigated. Special attention was paid to the role of tides, influential factors (concentrations of SPM and dissolved organic carbon, and particle size), and heavy metal speciation. The SPM-water and sediment-water partition coefficients (Kp) of the heavy metals exhibited similar changes along the channel sections, though the former were larger throughout the estuary. Because of the higher salinity, the Kp values of most of the metals were higher in the north branch than in the south branch. The Kp values of Cd, Co, and As generally decreased from the wet season to the dry season. Both the diagonal line method and paired samples t-test showed that no specific phase transfer of heavy metals existed during the flood and ebb tides, but the sediment-water Kp was more concentrated for the diagonal line method, owing to the relatively smaller tidal influences on the sediment. The partition coefficients (especially the Kp for SPM-water) had negative correlations with the dissolved organic carbon (DOC) but positive correlations were noted with the particle size for most of the heavy metals in sediment. Two types of significant correlations were observed between Kp and metal speciation (i.e., exchangeable, carbonate, reducible, organic, and residual fractions), which can be used to identify the dominant phase-partition mechanisms (e.g., adsorption or desorption) of heavy metals.