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Purpose: In recent years, microplastic (MP) contamination has raised enormous concern. However, data on the influence of solid waste treatment systems on MP pollution around agricultural soil are lacking. This study investigated the distribution and characteristics of MPs in agricultural soil surrounding a solid waste treatment center in southeastern China. Materials and methods: Fifty-seven agricultural topsoil samples around the solid waste treatment center were collected. The samples were pretreated by drying, flotation separation using NaCl solution, and digestion by H2O2. The abundance and morphological characteristics of MPs were determined by a microscope, followed by Raman spectroscopy analysis identified polymer types and SEM-EDS analysis observed surface morphology and the type of metals accumulated on the MPs. Results and discussion: Soil MPs' abundance ranged from 280 to 2360 items/kg, while a higher abundance of MPs was distributed in the downwind area. The < 1-mm MPs were dominant, and white fragment MPs were widely found. Polyethylene (52.86%) and polypropylene (27.14%) were the most common. Moreover, SEM-EDS images illustrated that MPs were significantly weathered and showed the uneven distribution of metal(loid) elements on the surface, implying that MPs may migrate as heavy metal vectors to threaten agroecosystem safety. Conclusions: This study reveals the distribution and characteristics of MPs in agricultural soil surrounding a solid waste treatment center in southeastern China, as well as the potential source of soil MPs, and provides systematic data for further research on MP pollution in agricultural soil. Supplementary Information: The online version contains supplementary material available at 10.1007/s11368-022-03341-6.
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Oyster shell (OS) is a kind of reusable resource that can serve as carbon source, biofilms carrier and basifying agent, suggesting it is an attractive filler option for biofiltration, but studies on its application in drinking water treatment are limited. In this study, one pilot-scale up-flow filter filled with OS media were designed to pretreat surface source water. Filter performance and biological functions were investigated to determine its application scope. The results showed that effluent pH increased and was stable around 7.5 due to the alkalinity provided by OS and its buffering capacity. High and stable removal efficiencies of turbidity (mostly >60%) were achieved. The removal efficiencies of NH4+-N changed in a wide range (mostly <30%). TOC and UV254 removal rate was low (<10%). The biofilms formation period took about 45 days. During this period, this filter mainly removed pollutants through adsorption by OS. High-throughput sequencing results showed that functional taxa did not play a key role after adsorption saturation in early operation period. Functional microbial taxa formed on the OS surface after long-term operation and NH4+-N removal rate increased to some extent. Our results suggested that unburned OS filter can be used as rough filter for turbidity removal instead of coagulation and sedimentation process. Preoxidation, calcination of OS, mixed with other filler and are recommended to improve the performance if it would be used for biofiltration. This study provides an insight for the reuse of OS in drinking water treatment.
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Água Potável , Ostreidae , Poluentes Químicos da Água , Purificação da Água , Animais , Estudos de Viabilidade , Filtração , Águas Residuárias , Poluentes Químicos da Água/análise , Purificação da Água/métodosRESUMO
Heavy metals in urban dust could pose noticeable human health risks, but there are few studies focusing on comprehensive human health risk assessment with the incorporation of both bioaccessibility and source apportionment in urban dust. Thus, fifty-eight urban dust samples were collected from kindergartens in Xiamen to analyze the bioaccessibility-based, source-specific health risk of heavy metals (V, Co, Ni, As, Mo, Cr, Mn, Cu, Zn, and Pb). Most heavy metals, except for V and Mn, were significantly enriched in urban dust based on their values of geoaccumulation index (Igeo) and may be influenced by human activities. The oral bioaccessibility values of heavy metals, which were estimated by the Solubility/Bioaccessibility Research Consortium (SBRC) in vitro model, ranged from 1.563% to 76.51%. The source apportionment determined by applying the absolute principal component analysis-multiple linear regression (APCS-MLR) model indicated five main potential sources, coal combustion, traffic and industrial, natural, construction and furniture sources, and unidentified sources, with contributions of 34.09%, 20.72%, 18.72%, 7.597% and 18.87%, respectively, to the accumulation of heavy metals in urban dust. After incorporating bioaccessibility adjustments, lower non-carcinogenic and carcinogenic risks of heavy metals were observed than those based on total metal content, with the mean hazard index (HI) values being less than the threshold value (1) and the mean total carcinogenic risk (TCR) values exceeding the precautionary criterion (10-6) for both adults and children. By combining bioaccessibility-based health risk assessment and source apportionment, traffic and industrial emissions and coal combustion dominated the noncarcinogenic and carcinogenic risks induced by heavy metals in urban dust, respectively. This study is expected to promote the systematic integration of source apportionment and bioaccessibility into health risk estimation for heavy metal contamination in urban dust, thus providing useful implications for better human health protection.
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The metal content of Tieguanyin tea from Anxi, Southeast China, was studied. Leaching experiments were designed based on the local tea-drinking habits, and tea infusions were prepared using three types of water and two methods of soaking tea. Twelve metals (Cd, As, Cr, Pb, Se, Sb, Ag, Tl, Cu, Zn, Be, and Ba) were measured by inductively coupled plasma mass spectrometry (ICP-MS), and a human health risk assessment was performed. The results showed that the quality of water used for steeping tea has a direct effect on the leaching concentrations of metals in the tea infusion and this effect can be reduced by using pure water or commercially available drinking water. Further, the two tea-soaking methods used by local residents can reduce the metal intake. The health risk assessment determined that the carcinogenic risk values of Cr, As, and Pb (Cr > Pb > As) were within an acceptable range (10-7-10-4); therefore, the concentrations of these metals in tea infusions do not pose substantial carcinogenic risk to tea drinkers. The results also indicate that the high concentrations of Tl in the tea infusions pose a substantial noncarcinogenic risk and may result from the dissolution characteristics of Tl and the water quality.
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Exposição Dietética/análise , Metais/análise , Chá/química , China , Exposição Dietética/efeitos adversos , Água Potável/análise , Água Potável/química , Contaminação de Alimentos/análise , Humanos , Medição de Risco , Poluentes Químicos da Água/análise , Qualidade da ÁguaRESUMO
Microbially-mediated arsenic biotransformation plays a pivotal role in the biogeochemical cycling of arsenic; however, the presence of arsenic biotransformation genes (ABGs) in urban dust remains unclear. To investigate the occurrence and spatiotemporal distributions of ABGs, a total of one hundred and eighteen urban dust samples were collected from different districts of Xiamen city, China in summer and winter. Although inorganic arsenic species, including arsenate [As(V)] and arsenite [As(III)], were found to be predominant, the methylated arsenicals, particularly trimethylarsine oxide [TMAs(V)O] and dimethylarsenate [DMAs(V)], were detected in urban dust. Abundant ABGs were identified in urban dust via AsChip analysis (a high-throughput qPCR chip for ABGs), of which As(III) S-adenosylmethionine methyltransferase genes (arsM), As(V) reductase genes (arsC), As(III) oxidase genes (aioA), As(III) transporter genes (arsB), and arsenic-sensing regulator genes (arsR) were the most prevalent, collectively constituting more than 90 % of ABGs in urban dust. Microbes involved in arsenic methylation were assigned to bacteria (e.g., Actinomycetes and Alphaproteobacteria), archaea (e.g., Halobacteria), and eukaryotes (e.g., Chlamydomonadaceae) in urban dust via the arsM amplicon sequencing. Temperature, a season-dependent environmental factor, profoundly affected the abundance of ABGs and the composition of microbes involved in arsenic methylation. This study provides new insights into the presence of ARGs within the urban dust.
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Despite global concerns about metal(loid)s in atmospheric particulate matter (PM), the presence of metal(loid) resistance genes (MRGs) in PM remains unknown. Therefore, we conducted a comprehensive investigation of the metal(loid)s and associated MRGs in PMs in two seasons (summer and winter) in Xiamen, China. According to the geoaccumulation index (Igeo), most metal(loid)s, except for V and Mn, exhibited enrichment in PM, suggesting potential anthropogenic sources. By employing Positive Matrix Factorization (PMF) model, utilizing a dataset encompassing both total and bioaccessible metal(loid)s, along with backward trajectory simulations, traffic emissions were determined to be the primary potential contributor of metal(loid)s in summer, whereas coal combustion was observed to have a dominant contribution in winter. The major contributor to the carcinogenic risk of metal(loid)s in both summer and winter was predominantly attributed to coal combustion, which serves as the main source of bioaccessible Cr. Bacterial communities within PMs showed lower diversity and network complexity in summer than in winter, with Pseudomonadales being the dominant order. Abundant MRGs, including the As(III) S-adenosylmethionine methyltransferase gene (arsM), Cu(I)-translocating P-type ATPase gene (copA), Zn(II)/Cd(II)/Pb(II)-translocating P-type ATPase gene (zntA), and Zn(II)-translocating P-type ATPase gene (ziaA), were detected within the PMs. Seasonal variations were observed for the metal(loid) concentration, bacterial community structure, and MRG abundance. The bacterial community composition and MRG abundance within PMs were primarily influenced by temperature, rather than metal(loid)s. This research offers novel perspectives on the occurrence of metal(loid)s and MRGs in PMs, thereby contributing to the control of air pollution.
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Poluentes Atmosféricos , Monitoramento Ambiental , Material Particulado , Material Particulado/análise , Poluentes Atmosféricos/análise , China , Metais/análise , Estações do Ano , Atmosfera/químicaRESUMO
The source apportionment and transfer of Pb in a paddy soil-rice-human system within the Jiulong River Basin in southeast China was investigated by analyzing (1) the chemical fractionation of Pb in paddy soils using a modified BCR four-step sequential extraction procedure, and (2) the bioaccessibility of Pb in both paddy soils and rice grains using a Simple Bioaccessibility Extraction Test method. In addition, a qualitative Pb isotopic model was used in combination with IsoSource software to quantify the contribution of potential Pb sources. The results show the enrichment of Pb in agro-ecosystems in the Jiulong River Basin. Contaminant Pb in paddy soils was mainly present in the reducible (42.9%) and the residual fractions (27.1%). The average bioaccessibility of Pb in rice grains was significantly higher than that in paddy soil, with values of 77.85% and 37.44%, respectively. Lead in paddy soils was primarily derived from agricultural (35.3%), natural (25.5%), industrial (24.5%) and coal combustion sources (14.7%), while Pb in rice grains was primarily derived from coal combustion (54.1%), agricultural (35.1%), industrial (6.0%) and natural sources (4.8%). The bioaccessible Pb was mainly derived from anthropogenic sources [agricultural (42.3% for soil and 25.3% for grain) and coal combustion sources (25.3% for soil and 59.3% for grain)]. Lead isotopic ratios are an effective tracer of Pb transfer from potential sources to rice plants and within the rice plants. Rice plants absorb Pb from the soil and the atmosphere through the roots and leaves, respectively. Most of the Pb was accumulated in roots. The integrated use of chemical fractionation, bioaccessibility and Pb isotopic data provides an effective method to study the source apportionment and transfer characteristics of Pb in paddy soil-rice-human systems.
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Oryza , Poluentes do Solo , Humanos , Solo , Chumbo , Ecossistema , Rios , Poluentes do Solo/análise , China , Carvão Mineral/análise , Monitoramento AmbientalRESUMO
Deliberate media selection can be conducted to achieve targeted objective in filters. In this study, three biofilters (BFs) packed with calcinated oyster shell (COS), granular activated carbon (GAC), and COS + GAC (Mix) were set up in parallel following a rough filter packed with natural oyster shell to compare the performance for treating micro-polluted source water. Different media showed selective removal effects for different pollutants. GAC outperformed COS in terms of TOC and UV254. COS achieved higher reduction in turbidity than GAC. Due to the removal of total bacteria, the absolute and relative abundance of antibiotic resistance genes (ARGs) both decreased much in rough filter treated water (1.16 × 1014 to 1.40 × 1013 copies L-1 and 81.6 to 36.9%, respectively). The highest diverse and rich bacterial community was found in the biofilms on the COS filler, so microbial leakage gave rise to high bacterial content, leading to the highest absolute abundance of ARGs in COS BF effluent (2.11 × 1013 copies L-1). The highest relative abundance of ARGs (41.2%) was found in GAC BF effluent. SourceTracker and biomarker analysis both suggested that treatment process played a more important role in shaping the bacterial community structure in Mix BF effluent than single media BFs, which contributed to the lowest absolute (8.69 × 1012 copies L-1) and relative abundance (25.2%) of ARGs in Mix BF effluent among the three BFs. Our results suggested that mix COS + GAC can not only give full play to their respective advantages for traditional pollutants, but also achieve highest reduction in ARGs.
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Água Potável , Poluentes Ambientais , Ostreidae , Poluentes Químicos da Água , Purificação da Água , Animais , Carvão Vegetal/química , Água Potável/química , Filtração/métodos , Bactérias/genética , Purificação da Água/métodos , AntibacterianosRESUMO
Little information is available on different contribution of TMPs from tire wear particles (TWPs), recycled tire crumbs (RTCs) and tire repair-polished Debris (TRDs) in the environment at national scale and their potential tendency. In this study, the TWPs were predicted using machine learning method of CNN (Convolutional Neural Networks) algorithms under different potential socioeconomic and climate scenarios based on the estimation of TMPs in China. Results showed that TWPs emission exhibited the most important part of TMPs, followed by RTCs and TRDs in China. The three mentioned tire microplastics largely distributed in Chinese coastal provinces. After machine learning applied in CNN using the dataset of estimated emission of TWPs from 2008 to 2018, the express delivery volume and education funding at the current increased rate would not have significant impacts on TWPs emissions; Additionally, TWPs emissions were also sensitive to changes of economic and transportation development; Low temperature conditions would further promote TWPs emissions. Accordingly, the rational development of logistics and green economy, the equilibrium improvement of education quality, and the increase of public traffic with new energy would be helpful to mitigate TWPs emissions. The obtained findings can enhance the understanding TMPs emission at particular scale and their corresponding precise management.
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Microplásticos , Plásticos , China , Monitoramento Ambiental , Aprendizado de Máquina , Fatores SocioeconômicosRESUMO
Roxarsone (3-nitro-4-hydroxyphenylarsonic acid, Rox), a widely used organoarsenical feed additive, can enter soils and be further biotransformed into various arsenic species that pose human health and ecological risks. However, the pathway and molecular mechanism of Rox biotransformation by soil microbes are not well studied. Therefore, in this study, we isolated a Rox-transforming bacterium from manure-fertilized soil and identified it as Pseudomonas chlororaphis through morphological analysis and 16S rRNA gene sequencing. Pseudomonas chlororaphis was able to biotransform Rox to 3-amino-4-hydroxyphenylarsonic acid (3-AHPAA), N-acetyl-4-hydroxy-m-arsanilic acid (N-AHPAA), arsenate [As(V)], arsenite [As(III)], and dimethylarsenate [DMAs(V)]. The complete genome of Pseudomonas chlororaphis was sequenced. PcmdaB, encoding a nitroreductase, and PcnhoA, encoding an acetyltransferase, were identified in the genome of Pseudomonas chlororaphis. Expression of PcmdaB and PcnhoA in E. coli Rosetta was shown to confer Rox(III) and 3-AHPAA(III) resistance through Rox nitroreduction and 3-AHPAA acetylation, respectively. The PcMdaB and PcNhoA enzymes were further purified and functionally characterized in vitro. The kinetic data of both PcMdaB and PcNhoA were well fit to the Michaelis-Menten equation, and nitroreduction catalyzed by PcMdaB is the rate-limiting step for Rox transformation. Our results provide new insights into the environmental risk assessment and bioremediation of Rox(V)-contaminated soils.
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Arsênio , Pseudomonas chlororaphis , Roxarsona , Humanos , Pseudomonas chlororaphis/metabolismo , Solo , Acetiltransferases , RNA Ribossômico 16S/genética , RNA Ribossômico 16S/metabolismo , Escherichia coli/metabolismo , Arsênio/metabolismo , Biotransformação , Nitrorredutases/metabolismoRESUMO
The production of methylmercury (MeHg) in flooded paddy fields determines its accumulation in rice grains; this, in turn, results in MeHg exposure risks for not only rice-eating humans but also wildlife. Nitrogen (N) fertilizers have been widely applied in rice cultivation fields to supply essential nutrients. However, the effects of N fertilizer addition on mercury (Hg) transformations are not unclear. This limits our understanding of MeHg formation in rice paddy ecosystems. In this study, we spiked three Hg tracers (200HgII, Me198Hg, and 202Hg0) in paddy slurries fertilized with urea, ammonium, and nitrate. The influences of N fertilization on Hg methylation, demethylation, and reduction and the underlying mechanisms were elucidated. The results revealed that dissimilatory nitrate reduction was the dominant process in the incubated paddy slurries. Nitrate addition inhibited HgII reduction, HgII methylation, and MeHg demethylation. Competition between nitrates and other electron acceptors (e.g., HgII, sulfate, or carbon dioxide) under dark conditions was the mechanism underlying nitrate-regulated Hg transformation. Ammonium and urea additions promoted HgII reduction, and anaerobic ammonium oxidation coupled with HgII reduction (Hgammox) was likely the reason. This work highlighted that nitrate addition not only inhibited HgII methylation but also reduced the demethylation of MeHg and therefore may generate more accumulation of MeHg in the incubated paddy slurries. Findings from this study link the biogeochemical cycling of N and Hg and provide crucial knowledge for assessing Hg risks in intermittently flooded wetland ecosystems.
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Mercúrio , Compostos de Metilmercúrio , Oryza , Humanos , Nitratos , Metilação , Ecossistema , Ureia , Fertilizantes , DesmetilaçãoRESUMO
Rare earth elements (REEs) and Nd isotopes are frequently employed to determine provenance, although their characteristics and provenances in the surface sediments of mangrove wetlands are rarely analyzed. In this study, a thorough analysis of the characteristics and provenances of REEs and Nd isotopes in the surface sediments of mangrove wetland in the Jiulong River Estuary was carried out. According to the results, the mean concentration of REEs in the surface sediments was 290.9 mg·kg-1, which was greater than the background value. Unpolluted to moderately polluted for La and Ce, as well as a moderate ecological risk for Lu, were indicated by the geoaccumulation index (Igeo) and potential ecological risk of individual factors ([Formula: see text]), respectively. The surface sediments showed substantial negative Eu anomalies but no significant Ce anomalies. The enrichments in LREE and flat HREE patterns are visible in the chondrite-normalized REE patterns. REEs in the surface sediments might be attributed to both natural sources (granite and magmatic rocks) and anthropogenic activities, including coal combustion, vehicle exhaust, steel smelting, and fertilizer, based on the (La/Yb)N-∑REE and ternary (La/Yb)N-(La/Sm)N-(Gd/Yb)N plots. The three-dimensional ∑LREE/∑HREE-Eu/Eu*-εNd(0) plot, when combined with the Nd isotope, further demonstrated that the REEs in the surface sediments appeared to have come from additional nonlocal potential sources.
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Monitoramento Ambiental , Metais Terras Raras , Poluentes Químicos da Água , China , Estuários , Sedimentos Geológicos/química , Isótopos , Metais Terras Raras/análise , Rios , Áreas Alagadas , Poluentes Químicos da Água/análiseRESUMO
Roxarsone (3-nitro-4-hydroxyphenylarsonic acid, Rox(V)), an extensively used organoarsenical feed additive, enters soils through the application of Rox(V)-containing manure and further degrades to highly toxic arsenicals. Microplastics, as emerging contaminants, are also frequently detected in soils. However, the effects of microplastics on soil Rox(V) degradation are unknown. A microcosm experiment was conducted to investigate soil Rox(V) degradation responses to polyethylene (PE) microplastics and the underlying mechanisms. PE microplastics inhibited soil Rox(V) degradation, with the main products being 3-amino-4-hydroxyphenylarsonic acid [3-AHPAA(V)], N-acetyl-4-hydroxy-m-arsanilic acid [N-AHPAA(V)], arsenate [As(V)], and arsenite [As(III)]. This inhibition was likely driven by the decline in soil pH by PE microplastic addition, which may directly enhance Rox(V) sorption in soils. The decreased soil pH further suppressed the nfnB gene related to nitroreduction of Rox(V) to 3-AHPAA(V) and nhoA gene associated with acetylation of 3-AHPAA(V) to N-AHPAA(V), accompanied by a decrease in the relative abundance of possible Rox(V)-degrading bacteria (e.g., Pseudomonadales), although the diversity, composition, network complexity, and assembly of soil bacterial communities were largely influenced by Rox(V) rather than PE microplastics. Our study emphasizes microplastic-induced inhibition of Rox(V) degradation in soils and the need to consider the role of microplastics in better risk assessment and remediation of Rox(V)-contaminated soils.
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Roxarsona , Roxarsona/química , Microplásticos , Plásticos , Solo/química , PolietilenoRESUMO
Atmospheric nitrate has been attracting increasing attention because it is one of the important components of PM2.5. Understanding the sources and formation mechanism of nitrate in PM2.5 is essential to take effective measures to prevent and control the emission of nitrogen oxides in the atmosphere and reduce the formation of haze. In this study, PM2.5 samples were collected from Ganzhou, an inland city in southeast China, during summer and winter. The concentrations of PM2.5 and NO3- were determined, and the isotopic compositions of NO3- (δ15N-NO3- and δ18O-NO3-) were analyzed in order to quantify the relative contributions of different emission sources and formation pathways of nitrate in PM2.5. The results showed that PM2.5 and NO3- concentrations were lower in summer (39.80 ± 11.10 µg·m-3 and 1.79 ± 0.70 µg·m-3) while higher in winter (69.85 ± 29.58 µg·m-3 and 10.83 ± 9.89 µg·m-3). The values of δ18O-NO3- and δ15N-NO3- ranged from 42.84 to 56.80 and from -11.17 to -2.08 in summer, while from 55.86 to 78.66 and from -10.63 to -1.88 in winter, respectively. The results of δ15N-NO3- combined with Bayesian isotope mixing model showed that the relative contributions of vehicle exhaust, soil microbial activity, biomass combustion and coal fired power plants were 59.3%, 28.5%, 8.7% and 3.4% in summer, while 65.1%, 20.1%, 10.6% and 4.1% in winter, respectively. The results of δ18O-NO3- combined with Bayesian isotope mixing model showed that the possible relative contributions of pathway 1 (P1) (NO2 + ·OH), pathway 2 (P2) (NO3 + HC) and pathway 3 (P3) (N2O5 + H2O) were 73.5%, 12.4% and 14.1% in summer, while 41.6%, 28.9% and 29.5% in winter, respectively. Moreover, P2 and P3 contributed more when NO3- concentrations were higher, suggesting that P2 and P3 were of significance to the formation of nitrate in PM2.5, especially during winter.
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Monitoramento Ambiental , Nitratos , Teorema de Bayes , China , Carvão Mineral , Monitoramento Ambiental/métodos , Nitratos/análise , Dióxido de Nitrogênio , Isótopos de Nitrogênio/análise , Óxidos de Nitrogênio/análise , Material Particulado/análiseRESUMO
Microplastics can act as carriers of heavy metals and may enter humans through ingestion and threaten human health. However, the bioaccessibility of heavy metals associated with microplastics and its implications for human health risk assessments are poorly understood. Therefore, in this study, four typical heavy metals (As(V), Cr(VI), Cd(II), and Pb(II)) and one typical microplastic (polyvinyl chloride, PVC) were chosen to estimate the human health risk of microplastic-associated heavy metals by incorporating bioaccessibility. Significant adsorption of heavy metals was observed with the following order for adsorption capacity: Pb(II) > Cr(VI) > Cd(II) > As(V); the efficiencies for desorption of these four heavy metals from PVC microplastics were all below 10%. The Fourier transform infrared spectroscopy results indicated that the functional groups on the surface of the virgin PVC microplastics did not play an important role in the capture process. Heavy metals in both gastric and small intestinal phases were prone to release from PVC microplastics when bioaccessibility was evaluated with the in vitro SBRC (Soluble Bioavailability Research Consortium) digestion model. In addition, Pb(II) bioaccessibility in the gastric phase was significantly higher than those in the other phases, while As(V), Cr(VI), and Cd(II) bioaccessibilities showed the opposite trend. After incorporating bioaccessibility adjustments, the noncarcinogenic hazards and carcinogenic risks determined were lower than those based on total metal contents. The individual hazard quotients (HQ) and carcinogenic risks (CR) for ingestion of these four heavy metals from PVC microplastics were all lower than the threshold values for adults and children. In summary, this study will provide a new view of the human health risks of heavy metals associated with microplastics.
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Metais Pesados , Microplásticos , Criança , Adulto , Humanos , Plásticos , Cloreto de Polivinila , Cádmio , Chumbo , Monitoramento Ambiental/métodos , Metais Pesados/análise , Medição de Risco/métodos , Digestão , ChinaRESUMO
The abundance and morphological characteristics of microplastics in the surface sediments of mangrove wetlands in the Jiulong River estuary were analyzed. The main sources of microplastics were also explored in detail. The results showed that the abundance of microplastics ranged from 640 to 1140 n·kg-1 (dry sediment), with an average of 935 n·kg-1, exhibiting a medium level compared with other domestic and abroad mangrove areas. The microscopic observation found that the microplastics were granular (39%), fragmented (31%), and fibrous (30%); the color was mainly transparent (55%); and the particle size was less than 1 mm (92%). As observed via Raman spectroscopy, the main polymer types of the microplastics were identified to be polyethylene, polyethylene terephthalate, and polypropylene, accounting for 57%, 34%, and 9%, respectively. The main sources of microplastics were the plastic waste from aquaculture nearby, urban and rural domestic or industrial wastewater in the basin, and the plastic waste transported here by the tide. Additionally, SEM-EDS results showed that the surface of the microplastics had the characteristics of depression, porosity, and tearing, and some heavy metal elements such as Pb, Cd, Hg, Cr, Fe, Mn, Zn, and Cu were attached to the microplastics. Microplastics may be transferred to the sediments as carriers of heavy metals, posing a potential threat to wetland ecological security.
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Metais Pesados , Poluentes Químicos da Água , China , Monitoramento Ambiental , Estuários , Sedimentos Geológicos , Metais Pesados/análise , Microplásticos , Plásticos , Medição de Risco , Rios , Poluentes Químicos da Água/análiseRESUMO
The speciation of heavy metals was analyzed using modified BCR four-step extraction methods to analyze the pollution of heavy metals in surface sediments collected from the mangrove wetland in Jiulong River Estuary. Subsequently, the pollution degree and the ecological risk of heavy metals were evaluated by using the ratio of secondary phase to primary phase (RSP), risk assessment code (RAC), and modified potential ecological risk index (MRI) assessment methods. The results of BCR four-step extraction showed that Cd (52.55%) and Mn (47.71%) mainly existed in weak-acid extractable fractions. Pb, Y, and Cu mainly existed in reducible and oxidizable fractions. Ba, Tl, V, Th, Cr, As, U, Hg, Ni, Zn, and Co mainly existed in residue fractions. The results of RSP showed that the sediments were heavily polluted by Cd and Mn and moderately polluted by Pb. Cu, Y, and Co were slightly polluted, whereas Zn, Hg, As, U, Ni, Cr, Th, V, Ba, and Tl were not polluted. The results of RAC showed that Cd and Mn were high risk, whereas Co and Zn were moderate risk. Ni, Cu, Hg, and Y were slight risk, and the other elements (U, As, Pb, Cr, V, Tl, Ba, and Th) presented no risk. The MRI results showed that the comprehensive potential ecological risk of heavy metals was serious in the surface sediments, whereas Hg and Cd were the main contribution factors. Hg was a serious potential hazard, followed by Cd. Tl was a medium potential hazard, and the other elements were low potential hazards. These results demonstrated that the mangroves were polluted by heavy metals in Jiulong River Estuary, and effective strategies should be employed to remediate the mangrove sediment in the future.
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Mercúrio , Metais Pesados , Poluentes Químicos da Água , Cádmio , China , Monitoramento Ambiental/métodos , Estuários , Sedimentos Geológicos/química , Chumbo , Metais Pesados/análise , Medição de Risco , Rios/química , Poluentes Químicos da Água/análiseRESUMO
The article presents the distribution and enrichment of acid-leachable heavy metals (ALHMs) Cu, Zn, Pb, Cr, Mn, and Fe in the intertidal sediments collected from Quanzhou Bay, southeast coast of China. The contents of ALHMs along with sediment texture, total organic carbon, S2-, and CaCO3 in surface sediments were analyzed to identify the input of heavy metals from various sources. The enrichment of ALHMs in the sediments is mainly attributed to the intense industrial activities around Quanzhou Bay and to the serried activities of intertidal breed aquatics along the seacoast. The results also illustrate the association between the ALHMs with the finer fractions, organic matter, and Fe oxyhydroxides in the sediments. The above results were very supported by the multivariate statistical analyses, including correlation, principal component analysis, and hierarchical clustering analysis. Comparative results of ALHMs in the intertidal sediments from Quanzhou Bay with those in other domestic bays and estuaries indicate that the study area has been enriched with heavy metals, especially with Zn, Cu, and Pb, during the past few decades. The results of the present study suggest that the authorities should pay attention to the current status and take some measures to control the heavy metal pollution in the study area.
Assuntos
Monitoramento Ambiental/métodos , Sedimentos Geológicos/análise , Metais Pesados/análise , Poluentes Químicos da Água/análise , China , Água do Mar/análiseRESUMO
The bioaccessibility and health risks of heavy metals in soil-rice system of southwestern Fujian province were studied by combining a simple bioavailability extraction method (SBET) with a health risk assessment model. The results showed that some heavy metals in the agricultural soils and rice of southwestern Fujian province were enriched. The contents of Cd, Zn, Pb, and Cu were greater than the screening value of soil pollution risk for agricultural land (GB 15618-2018) by 32.4%, 15.5%, 14.1%, and 12.7% in the study areas, respectively. The accumulation ability of heavy metals was different and followed the approximately decreasing order of Cd > Zn > Cu > Ni > Hg > As > Cr > Pb. The bioaccessibility of heavy metals in soils and rice were quite different. The bioaccessibility of each heavy metal in rice was greater than the bioaccessibility of the heavy metals in soil, which indicated that the heavy metals in rice were more easily absorbed by the human body. The comprehensive non-carcinogenic risk index (HI) of heavy metals to adults and children was 2.71 and 4.06, respectively, indicating that there were non-carcinogenic risks. The comprehensive carcinogenic risk index (TCR) of heavy metals to adults and children was 1.42×10-3 and 5.28×10-4, respectively, indicating that there was a carcinogenic risk present. The non-carcinogenic risks were mainly due to As, while the carcinogenic risks were mainly contributed by Cd. The non-carcinogenic risk of children was higher than that of adults, while the carcinogenic risk of children was lower than that of adults. This result may be related to physiological characteristics, exposure period, and dietary intake. The dietary intake route may be the main pathway for heavy metals in the soil-rice system of southwest Fujian province to cause health risks. Therefore, more attention should be paid to the risks of dietary exposure in the risk management of heavy metals.
Assuntos
Metais Pesados , Oryza , Poluentes do Solo , Adulto , Criança , China , Monitoramento Ambiental , Humanos , Metais Pesados/análise , Medição de Risco , Solo , Poluentes do Solo/análiseRESUMO
The concentration and speciation of heavy metals (Cr, Ni, Cu, Zn, Cd, Pb) in surface sediments (phi < or = 63 microm) of Jinjiang River tidal reach are determined to evaluate the metal behavior. A modified BCR three-step sequential extraction procedure is carried out, and the residual fraction is undertaken by microwave-assisted acid digestion. The index of geo-accumulation indicates that Cd appeared highest among all these heavy metals in surface sediments, Cr, Cu, Zn lower, and Ni, Pb the least. The percentage of Zn, Cd is comparatively higher in the acid soluble fraction, Pb and Cu higher in the reductive fraction, indicating larger potential danger to the environment. So it is essential for developing the future remediation plans and pollution control strategies.