Roxarsone biotransformation by a nitroreductase and an acetyltransferase in Pseudomonas chlororaphis, a bacterium isolated from soil.

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.

Characteristics and provenances of rare earth elements and Nd isotopes in surface sediments of mangrove wetlands in the Jiulong River Estuary, China.

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.

Identification and characterization of a phosphinothricin N-acetyltransferase from Enterobacter LSJC7.

Phosphinothricin (PPT) is a widely used and non-selective herbicide. PPT-resistance genes, especially PPT N-acetyltransferase genes, have been used in the development of transgenic PPT-resistant crops. However, there are only a limited number of available PPT-resistance genes for use in plant biotechnology. In this study, we found that Enterobacter LSJC7 is highly resistant to PPT and can acetylate PPT to N-acetyl phosphinothricin (Ac-PPT). Furthermore, a novel PPT N-acetyltransferase gene, named LsarsN, was identified from LSJC7. When LsarsN was expressed in E. coli AW3110, it confered resistance to PPT. Ac-PPT was detected in both the culture medium and cells of AW3110 expressing the LsarsN-pET22b plasmid. The purified LsArsN protein also showed strong N-acetylation ability in vitro, and its enzymatic kinetic curve was fitted with the Michaelis-Mentan equation. Compared with wild-type LsArsN, both R72A and R74A mutants showed significantly lower PPT N-acetylation ability. In summary, our results systematically characterized LsArsN with strong ability for PPT N-acetylation, which lays the groundwork for future research into the use of this novel gene, LsarsN, to create PPT-resistant crops.

Inhibitory effect of polyethylene microplastics on roxarsone degradation in soils.

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.

Randomized Trial of First-Line Tyrosine Kinase Inhibitor With or Without Radiotherapy for Synchronous Oligometastatic EGFR-Mutated Non-Small Cell Lung Cancer.

BACKGROUND: Adding radiotherapy (RT) to systemic therapy improves progression-free survival (PFS) and overall survival (OS) in oligometastatic non-small cell lung cancer (NSCLC). Whether these findings translate to epidermal growth factor receptor (EGFR)-mutated NSCLC remains unknown. The SINDAS trial (NCT02893332) evaluated first-line tyrosine kinase inhibitor (TKI) therapy for EGFR-mutated synchronous oligometastatic NSCLC and randomized to upfront RT vs no RT; we now report the prespecified interim analysis at 68% accrual. METHODS: Inclusion criteria were biopsy-proven EGFR-mutated adenocarcinoma (per amplification refractory mutation system or next generation sequencing), with synchronous (newly diagnosed, treatment naïve) oligometastatic (≤5 metastases; ≤2 lesions in any one organ) NSCLC without brain metastases. All patients received a first-generation TKI (gefitinib, erlotinib, or icotinib), and randomization was between no RT vs RT (25-40 Gy in 5 fractions depending on tumor size and location) to all metastases and the primary tumor/involved regional lymphatics. The primary endpoint (intention to treat) was PFS. Secondary endpoints included OS and toxicities. All statistical tests were 2-sided. RESULTS: A total of 133 patients (n = 65 TKI only, n = 68 TKI with RT) were enrolled (2016-2019). The median follow-up was 23.6 months. The respective median PFS was 12.5 months vs 20.2 months (P < .001), and the median OS was 17.4 months vs 25.5 months (P < .001) for TKI only vs TKI with RT. Treatment yielded no grade 5 events and a 6% rate of symptomatic grade 3-4 pneumonitis in the TKI with RT arm. Based on the efficacy results of this prespecified interim analysis, the ethics committee recommended premature cessation of this trial. CONCLUSIONS: As compared with a first-line TKI alone, addition of upfront local therapy using RT statistically significantly improved PFS and OS for EGFR-mutated NSCLC.

[Speciation and Pollution Assessment of Heavy Metals in Mangrove Surface Sediments in Jiulong River Estuary].

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.

Bioaccessibility of microplastic-associated heavy metals using an in vitro digestion model and its implications for human health risk assessment.

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.

[Occurrence Characteristics of Microplastics in Mangrove Sediments in the Jiulong River Estuary and the Association with Heavy Metals].

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.

Incorporating bioaccessibility and source apportionment into human health risk assessment of heavy metals in urban dust of Xiamen, China.

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.

[Bioaccessibility and Health Risks of the Heavy Metals in Soil-Rice System of Southwest Fujian Province].

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.

Bioaccumulation and biotransformation of arsenic in Leptolyngbya boryana.

Leptolyngbya boryana (L. boryana) is a typical filamentous cyanobacterium that is widely distributed in aquatic ecosystems and is considered to play an important role in the arsenic biogeochemical cycle. Our results showed that L. boryana resisted arsenite (As(III)) and arsenate (As(V)) concentrations up to 0.25 mM and 5 mM, respectively. When exposed to 100 µM As(III) or As(V) for 4 weeks, L. boryana accumulated as much arsenic as 570.0 mg kg-1 and 268.5 mg kg-1, respectively. After the 4-week exposure to As(III) and As(V), organoarsenicals including dimethylarsenate (DMAs(V)) and oxo-arsenosugar-phosphate (Oxo-PO4) were detected in the cells of L. boryana, while inorganic arsenic, especially As(V), was still the main species in both the cells and medium. Furthermore, arsenic oxidation was observed to be solely caused by L. boryana cells and was considered the dominant detoxification pathway. In conclusion, due to its powerful arsenic accumulation, biotransformation, and detoxification abilities, L. boryana might play an important role in arsenic remediation in aquatic environments.

Provenance and bioaccessibility of rare earth elements in atmospheric particles in areas impacted by the optoelectronic industry.

Rare earth elements (REEs) are widely used in optoelectronic industries, and they can be emitted into the environment and may induce biological effects. In this study, we investigated the provenance and bioaccessibility of REEs in atmospheric particles (APs) collected from areas impacted by the optoelectronic industry. The geoaccumulation index (Igeo) values showed that Y, Eu, and Tb were much more enriched in the APs from the optoelectronic recycling sites than in those from the optoelectronic producing sites and were not enriched in the APs from the optoelectronic administrative sites and background sites. The characteristic parameters and the distribution patterns of REEs demonstrated that the AP samples from the recycling sites and producing sites showed remarkably positive Eu and Tb anomalies. According to the positive matrix factorization (PMF) model, the optoelectronic industry was quantitatively determined to contribute 82.8% of Y, 86.5% of Eu, and 83.4% of Tb. Furthermore, an in vitro physiologically based extraction test (PBET) was performed to assess the bioaccessibility of REEs in the APs. The results showed that the bioaccessibility of all the REEs in the APs was below 50.0% in the human gastrointestinal tract, with higher values in the gastric phases than in the intestinal phases. In particular, extremely low gastric bioaccessibilities of Tb and Ce and relatively high gastric bioaccessibilities of Y and Eu were observed in the APs from the recycling sites and producing sites, which may due to the chemical composition of the compounds containing REEs that are used in the optoelectronic industry. In conclusion, our results provide additional information about the contribution and influence of the optoelectronic industry on the provenance and bioaccessibility of REEs in APs.

[Source Appointment of Heavy Metals in Agricultural Soils of the Jiulong River Basin Based on Positive Matrix Factorization].

In order to study the source appointment of heavy metals in agricultural soils of the Jiulong River Basin, Fujian Province, China. 71 agricultural soil samples were collected in July 2017. The concentrations of heavy metals in agricultural soils were determined by inductively coupled plasma mass spectrometry (ICP-MS) and atomic fluorescence spectrometry (AFS). Here, we use a positive matrix factorization (PMF) model for the source appointment of heavy metals in the sampled soils. The results showed that most of the heavy metal concentrations in the sampled agricultural soils were higher than soil background concentrations for the Fujian Province. The concentrations of Cd, Zn, Pb, and Cu in some soil samples were greater than the screening value of the Chinese soil pollution risk levels for agricultural land (GB 15618-2018). The spatial distributions of heavy metals showed a moderate variation across three regions of the study area (i.e., the North River watershed, West River watershed, and the estuary area). The highest concentration of Cr, Ni, Cu, Zn, and Cd were found in Longyan City (North River watershed), the highest concentrations of Pb were found in the West River watershed, and the highest concentrations of Co, Hg, and As were found in the estuary area. The non-negative properties of the source component spectrum and source contribution rate (obtained by the PMF model), as well as the significant correlation between the measured and PMF predicted concentrations, indicated that the results of the PMF model were relatively reasonable and can meet research needs. The source apportionment results of the PMF model showed that natural sources, agricultural sources, coal combustion, and industrial sources were the four major potential sources for heavy metals in the sampled agricultural soils, contributing 37.0%, 26.7%, 17.6%, and 18.7%, respectively.

[Migration and Source Analysis of Heavy Metals in Vertical Soil Profiles of the Drylands of Xiamen City].

The concentrations of eight heavy metal elements (V, Cr, Co, Ni, Cu, Zn, Sr, and Pb) and the isotopic composition of Pb and Sr were determined in vertical soil profiles of the drylands of Xiamen City using ICP-MS and TIMS. The vertical distributions and leaching migration patterns of the heavy metals were also analyzed. The results showed that most of the heavy metals (except for Sr) were not enriched relative background values at most profile depths, which indicated that heavy metal content is less affected by exogenous sources. The migration coefficients of Sr were greater than 0 throughout the entire soil profile; Zn and Co were enriched in the surface soil; and Cr, Ni, and Cu were depleted throughout the profile. V and Pb were less influenced by external activities. Sr and Pb showed clear vertical migration characteristics, and the migration depth of Sr was greater than that of Pb. Factor analysis showed that the heavy metals mainly originated from natural sources, followed by agricultural activities, transportation, and other complex anthropogenic activities. Enrichment factor analysis showed that Sr was affected by exogenous sources to varying extents. The isotopic composition analysis of Pb and Sr showed that Pb was mainly derived from the parent material, whereas Sr was interpreted as deriving from both the parent material and anthropogenic activities, and tended to migrate to the subsurface soil horizons (30-70 cm).

[Sources Analysis and Health Risk Assessment of Polycyclic Aromatic Hydrocarbons in the PM2.5 Fraction of Fugitive Dust in Nanchang City].

In order to understand the sources and health risks of polycyclic aromatic hydrocarbons in the PM2.5 fraction of road dust and soil dust in Nanchang city, PM2.5 samples were collected by a resuspension sampler and the concentrations of sixteen polycyclic aromatic hydrocarbons (PAHs) were detected. The results showed that the ΣPAHs of the road dust ranged from 48.85 to 166.16 µg·kg-1, with a mean of (114.22±39.95) µg·kg-1. The ΣPAHs of the soil dust ranged from 31.05 to 62.92 µg·kg-1 with a mean of (40.79±9.39) µg·kg-1. The PAHs in the PM2.5 fraction of fugitive dust were mainly composed of 4-5 rings. The results of the principal component analysis and multiple linear regression analysis indicated that the PAHs in PM2.5 samples of road dust mainly originated from motor vehicle emissions, coal sources, and oil leakage, with contribution rates of 51.7% and 48.3%, respectively. For children and adult males, the carcinogenic risk values of PAHs in different exposure pathways followed the order dermal contact > ingestion > inhalation, while those for adult females followed the order ingestion > dermal contact > inhalation. For all exposure pathways, the carcinogenic risks of the PAHs to adults were higher than those to children. For all populations, the total carcinogenic risk values of the PAHs were lower than the US EPA recommended carcinogenic risk threshold of 10-6, indicating no carcinogenic risk.

[Assessment of the Speciation and Pollution of Heavy Metals in Paddy Soils from the Jiulong River Basin].

Speciation characteristics of twelve heavy metals in 71 paddy soils from the Jiulong River Basin were analyzed using inductively coupled plasma mass spectrometry (ICP-MS) and the modified BCR protocol. The risk assessment coding method (RAC), ratio of secondary phase and primary phase (RSP), and geoaccumulation index (Igeo) were applied to evaluate the pollution degree of heavy metals in the area. The results show that most of these elements are abundant in the paddy soils and the speciation characteristics of different heavy metals vary. The elements Cd and Mn mainly exist as acid soluble fractions in the soils, with a mean proportion of 46.2% and 35.2%, respectively; Fe and Pb mainly exist as reducible fractions in the soils, with a mean proportion of 64.5% and 41.5%, respectively; and V, Cr, Ni, As, Co, Sr, Zn, and Cu mainly exist as residual fractions in the soils, with a mean proportion of 79.6%, 78.4%, 73.1%, 67.7%, 51.9%, 49.7%, 45.3%, and 38.4%, respectively. The three pollution assessment methods focus on the acid-soluble phase, secondary phase, and total amount of heavy metals, respectively. All have their own application value and disadvantages of incompletion. The comprehensive analysis of these three pollution assessment methods helps to more accurately and comprehensively assess the pollution characteristics of the heavy metals. The results show that the paddy soils are moderately to severely polluted with Cd; the Mn and Sr pollution is mild to severe; the Zn, Pb, Cu, and Co pollution is mild to moderate; the As and Ni pollution is absent or moderate; and V, Fe, and Cr pollution is non-existent or mild.

[Composition Characteristics and Sources Apportionment of Lanthanoid in PM2.5 of Quanzhou].

Samples of PM2.5 were collected from 5 sites in Quanzhou in March, April and July, 2014. The concentrations of lanthanoid and other trace metals in the PM2.5 were determined by Inductively Coupled Plasma Mass Spectrometry(ICP-MS). The total lanthanoid concentration (ΣLoid), the ratio of light-lanthanoid(L Loid, including, La, Ce, Pr, Nd, Sm and Eu) to heavy-lanthanoid(H Loid, including Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu) in PM2.5 were 2.490-5.708 ng·m-3(65.682-126.529 µg·g-1) and 12.086-14.319, respectively. The distribution pattern of Loid in PM2.5 was also evaluated in this study. All PM2.5 samples showed similar distribution pattern with local topsoil. And positive Ce and negative Eu anomalies were observed in PM2.5. La-Ce-V plots and chemical mass balance(CMB) model were used for source identification and apportionment of PM2.5in Quanzhou. The CMB model was used to identify four main sources:urban fugitive dust, coal combustion, vehicle exhaust and waste incineration emission which had a contribution of 18.9%, 10.9%, 30.6% and 30.2%, respectively.

[Assessment of Heavy Metal Pollution and Tracing Sources by Pb & Sr Isotope in the Soil Profile of Woodland in Quanzhou].

The contents of 8 heavy metal elements (Sr, Ni, Fe, Cr, Cu, Mn, Pb, Zn) and the lead & strontium isotope composition of soil profile of woodland in Quanzhou city were analyzed by AAS and ICP-MS, respectively. A modified BCR four-step sequential extraction procedure was carried out to obtain the speciation fractionation of heavy metals in the soil profile from 4 stations. The results of the heavy metal elements and the speciation fractionation of heavy metals in the soil profile showed that the heavy metal pollution in the woodland in Quanzhou was relatively light, and the main pollution factor was Sr. The non-residue state of Pb was the highest, leading to the highest activity. The result of Nemero comprehensive pollution index showed that Sr in the depth of 0-60 cm was at heavy pollution level. The results of the RSP showed that the activity of Pb was the highest. The results of EF showed that Pb, Sr, Mn and Zn had exogenous sources. Factor analysis showed that the main sources of heavy metals were the compound pollution of agricultural activities, natural resources, and the vehicle exhaust. Composition of Pb isotopic ratios showed that, Pb in soil profile of woodland in Quanzhou was from vehicle exhaust and parent material. The contribution rates of the two sources in the soil profile were calculated by using the two-mixed model. The contribution rates of parent material and vehicle exhaust were 85.14%(62.53%-98.36%) and 14.86%(1.640%-37.47%) on average, respectively. Strontium isotope tracing results showed that the main sources of strontium were also vehicle exhaust and parent material. Coupling both Pb and Sr isotope ratios agreed with the above mentioned results.

[Seasonal Variation and Source Apportionment of Water-Soluble Ions in PM2.5 in Quanzhou City].

In this study, the seasonal characteristics of water-soluble ions (WSIs) present in fine particulate matter (PM2.5) in Quanzhou City were investigated. PM2.5 samples were collected at five different sites in the city from March 2014 to January 2015 and the concentrations of Na+, NH4+, K+, Ca2+, Mg2+, F-, Cl-, NO3-, and SO42- were determined by ion-exchange chromatography. In order to identify the sources of these WSIs, the positive matrix factorization (PMF) analysis was applied. The seasonal variations in total WSI concentrations were found to decrease in the order of spring > winter > summer > autumn. The ions SO42-, NO3-, and NH4+ were the major WSIs found in PM2.5, accounting for 90.3%±3.3%, 68.8%±11.7%, 78.9%±7.1%, and 74.0%±18.4% of the total amount of ions found in spring, summer, autumn, and winter, respectively. These results suggested that the level of secondary ions was relatively high in the spring season. The anion-to-cation ratio in each of the four seasons was less than one, which indicated that PM2.5 in Quanzhou City was slightly alkaline. Furthermore, NH4+ ions in PM2.5 mostly existed in the form of (NH4)2SO4, NH4HSO4, and NH4NO3 during spring and winter, while they were primarily found as NH4HSO4 and NH4NO3 in the summer and autumn seasons. PMF analysis revealed that marine salt, secondary sources, fugitive dust from construction, municipal incineration, and biomass burning were the main potential sources of the ionic components of PM2.5.

[Pollution Assessment and Source Analysis of Metals in PM2.5 in Haicang District, Xiamen City, China].

To determine the spatial-temporal distributions and potential sources of metals in PM2.5 and assess health risks from heavy metals, 348 PM2.5 samples were collected in the Haicang District of Xiamen, China from April 2015 to January 2016. Metals (K, Ca, Na, Mg, Al, Zn, Cu, Fe, Ti, As, V, Mn, Ba, Co) in PM2.5 were detected using an X-ray fluorescence analyzer (XRF). Pollution assessment was performed via enrichment factor calculation and health risk assessment. Potential sources were explored using Pearson's correlation coefficient, principal component analysis, and the HYSPLIT Trajectory Model. Results showed that the total concentration of 14 metal elements contributed to 5.4%-10.6% of PM2.5 during the sampling period. The total concentration of metals was higher in spring and winter than those in summer and autumn. The concentrations were higher in the port and the industrial areas than in residential areas and background locations, in agreement with the seasonal and spatial distribution of PM2.5. The frequency of PM2.5 daily concentrations exceeding the Chinese Ambient Air Quality Standards was higher in the port and residential areas in the summer due to operations at the port and the wind direction. Zn concentration was the highest in the industrial area followed by the background location. Meanwhile, the highest concentration of V was observed in the port area; V concentration in the residential area was high in the summer. These variations in Zn and V indicated that the elements emitted in the polluted areas migrated easily to residential and background areas. K concentrations were the highest in winter and As showed a higher rate of exceeding the standard in winter and spring, indicating that activities, such as biomass burning and coal combustion in the winter severely impacted air quality. The enrichment factors of Cu, Zn, As, Co, Na, and Mn varied considerably, from 67 to 8,449. The total risk level for non-carcinogenic heavy metals (Zn, Cu, Mn) was lower than the average level of risk acceptance (1×10-6 a-1) and Mn contributed 74%-88% of the total risk level of Zn, Cu, and Mn. The combined results of the correlation analysis and the principal component analysis revealed that metals in PM2.5 were mainly came from re-suspension of ground dust, motor vehicle emissions, coal combustion, industrial emissions, and heavy oil combustion, with contributions of 34.5%, 12.5%, 10.6%, and 7.8% respectively. The HYSPLIT Trajectory Model showed that Xiamen was affected by the local air mass in spring, autumn, and winter, but not in summer. Moreover, the rise of PM2.5 in spring and winter was attributed to air masses traveling through the Yangtze River Delta.