Pollution characteristics, sources, and health risks of phthalate esters in ambient air: A daily continuous monitoring study in the central Chinese city of Nanchang.

In recent years, the atmospheric pollution caused by phthalate esters (PAEs) has been increasing due to the widespread use of PAE-containing materials. Existing research on atmospheric PAEs lacks long-term continuous observation and samples from cities in central China. To investigate the pollution characteristics, sources, and health risks of PAEs in the ambient air of a typical city in central China, daily PM2.5 samples were collected in Nanchang from November 2020 to October 2021. In this study, the detection and quantification of six significant PAE contaminants, namely diethyl phthalate (DEP), di-n-butyl phthalate (DnBP), diisobutyl phthalate (DIBP), Di-2-ethylhexyl phthalate (DEHP), di-n-octyl phthalate (DnOP), and diisodecyl phthalate (DIDP), were accomplished using gas chromatography and mass spectrometry. The results revealed that the concentrations of DEP, DnBP, DEHP, and DnOP were relatively high. Higher temperatures promote the volatilization of PAEs, leading to an increase in the gaseous and particulate PAE concentrations in warm seasons and winter pollution scenarios. The results of principal component analysis show that PAEs mainly come from volatile products and polyvinylchloride plastics. Using positive matrix factorization analysis, it is shown that these two sources contribute 67.0% and 33.0% in atmosphere PAEs, respectively. Seasonally, the contribution of volatile products to both gaseous and particulate PAEs substantially increases during warm seasons. The residents in Nanchang exposed to PAEs have a negligible non-cancer risk and a potential low cancer risk. During the warm seasons, more PAEs are emitted into the air, which will increase the toxicity of PAEs and their impact on human health.

Sources and influences of atmospheric nonpolar organic compounds in Nanchang, central China: Full-year monitoring with a focus on winter pollution episodes.

Nonpolar organic compounds (NPOCs) are found in atmospheric aerosols and have significant implications for environmental and human health. Although many studies have quantitatively estimated the sources of NPOCs in different cities, few have evaluated their main influencing factors (e.g., emissions and meteorological conditions) at relatively long (e.g., different seasons) and short timescales (e.g., several days during pollution episodes). A better understanding of this issue could optimise strategies for dealing with organic contamination in atmospheric particulate matter. NPOCs (including n-alkanes, PAHs and hopanes) in fine particulate matter (PM2.5) were sampled daily at Nanchang, China, from 1 November 2020 to 31 October 2021. Analyses of specific biomarkers and diagnostic ratios indicate that the NPOCs mainly had anthropogenic sources. The quantitative estimates of a positive matrix factorization model show that fossil fuel and biomass combustion were the main sources of n-alkanes (contributing 64.8 %), while vehicle exhaust was the main source of PAHs (47.0 %) and hopanes (52.3 %). Seasonally, the contributions from coal and/or biomass combustion were higher in autumn and winter (40.2-56.3 %) than in spring and summer (25.7-44.3 %), while contributions from natural plants, petroleum volatilization and vehicle exhaust were higher in spring and summer (14.7-63.5 %) than in autumn and winter (8.1-48.9 %). Redundancy analysis shows that increased emissions, especially from coal and/or biomass combustion, are the main cause of increases in NPOCs, during both annual sampling periods and winter pollution episodes. Over the year, higher temperature and longer sunshine hours correspond to lower NPOC concentrations. In winter pollution episodes, increases in temperature and relative humidity correspond to increases in NPOC concentrations. Our results suggest that controlling primary emissions, especially from coal and biomass combustion, may be an effective way to prevent increases in NPOC concentrations.

Changes in nitrate accumulation mechanisms as PM2.5 levels increase on the North China Plain: A perspective from the dual isotopic compositions of nitrate.

Nitrate (NO3-) has become recognized as the most important water-soluble ion in fine particulate (PM2.5), and has been proposed as a driving factor for regional haze formation. However, nitrate formation mechanisms are still poorly understood. In this study, PM2.5 samples were collected from September 2017 to August 2018 in Shijiazhuang, a city located on the North China Plain, and NO3-concentration, δ18O-NO3- and δ15N-NO3- values in PM2.5 were analyzed. NO3- concentrations increased as PM2.5 levels increased during both polluted and non-polluted days over the entire year. δ18O-NO3- values during cold months (63.5-103‰) were higher than those during warm months (50.3-85.4‰), these results suggested that the nitrate formation pathways shifted from the NO2 + OH (POH) in warm months to the N2O5 + H2O (PN2O5) and NO3 + VOCs (PNO3) pathways in cold months. Especially during cold months, δ18O-NO3- values increased from 65.2-79.9‰ to 80.7-96.2‰ when PM2.5 increased from ∼25 to >100 µg/m3, but when PM2.5 > 100 µg/m3, there were relatively small variations in δ18O-NO3-. These results suggested that nitrate formation pathways changed from POH to PN2O5 and PNO3 pathways when PM2.5 < 100 µg/m3, but that PN2O5 and PNO3 dominated nitrate production when PM2.5 > 100 µg/m3. Higher δ15N-NO3- values in warm months (-11.8-13.8‰) than in cold months (-0.7-22.6‰) may be attributed to differences in NOx emission sources and nitrogen isotopic fractionation among NOx and NO3-. These results provide information on the dual isotopic compositions of nitrate to understand nitrate formation pathways under different PM2.5 levels.

Methylmercury biomagnification in aquatic food webs of Poyang Lake, China: Insights from amino acid signatures.

As the dominant mercury species in fish, methylmercury (MeHg) biomagnifies during its trophic transfer through aquatic food webs. MeHg is known to bind to cysteine, forming the complex of MeHg-cysteine. However, relationship between MeHg and cysteine in large-scale food webs has not been explored and contrasted with MeHg biomagnification models. Here, we quantified the compound-specific nitrogen isotopic analysis of amino acids (CSIA-AA), MeHg, and amino acid composition in aquatic organisms of Poyang Lake, the largest freshwater lake in China. The trophic positions (TPAA) of organisms ranged from 1.0 ± 0.1-3.7 ± 0.2 based on CSIA-AA approach. The trophic magnification factor (TMF) of MeHg, derived from the regression slope of Log-transformed MeHg in organisms upon their TPAA for the entire food web was 9.5 ± 0.5. Significantly positive regression between MeHg and cysteine (R2 = 0.64, p < 0.01) was documented, suggesting MeHg-cysteine complex may potentially play a critical role in the bioaccumulation of MeHg. Furthermore, TMFs of MeHg calculated with and without cysteine normalization compared well (7.7-8.7) when excluding primary producers. Our results implied that MeHg may biomagnify as the complex of MeHg-cysteine and contribute to our understanding of MeHg trophic transfer at the molecular level.

Spatial variability of inhalable fungal communities in airborne PM2.5 across Nanchang, China.

Although fungi are ubiquitous in the atmosphere and have important effect on human health, their spatial variability about diversity and taxonomic composition, remain poorly understood. Considering the differences of environmental conditions, distinct airborne fungal communities were expected in the urban, suburban and forest areas. To test this hypothesis, PM2.5 samples were consecutively collected for 14 days across Nanchang, China. The results showed that fungal diversities of samples from forest were higher than that from the other two areas. Even though the airborne fungal communities at one sampling site fluctuated during the short-term period, the compositions in the forest significantly diverged from the other two areas (Anosim and Adonis: p < 0.01). Canonical correspondence analysis (CCA) and mantel test (p < 0.01) indicated that these disparities among sampling sites were partly drove by air pollutants. High concentrations of air particles (PM2.5 and PM10) and gaseous pollutants (NO2 and CO) associated with human activities were accompanied by high relative abundances of several genera such as Alternaria, Penicillium and Coprinellus. Likewise, Pearson correlation analysis showed that rainfall and relative humidity enhanced the relative abundances of 13 genera like Malassezia and Schizophyllum. Notably, part of these genera was potential allergens and pathogens to human, and it seemed that there were higher health risks in urban and suburban. This study furthers our understanding of the variation of airborne fungal community in different land-use types and different treatments may be applied to deal with the potential threat of airborne fungi.

Compound-specific δ15N composition of free amino acids in moss as indicators of atmospheric nitrogen sources.

Haplocladium microphyllum moss samples were collected in Nanchang, China. Free amino acid (FAA) concentrations and N isotope compositions (δ15NFAA) in the samples were determined and compared with the bulk N concentrations and δ15Nbulk values. The aim was to determine whether δ15NFAA values in moss (which are very variable) indicate the sources of atmospheric N. The δ15NFAA values among individual FAA varied widely (from -19.3‰ to +16.1‰), possibly because of the different sources of N and isotope fractionation in amino acids metabolic pathways. Total 15N-enrichment for the individual FAAs was equal to total 15N-depletion relative to δ15Nbulk. The concentration-weighted mean δ15N value for total FAAs (TFAA) (δ15NTFAA) was -3.1‰ ± 3.2‰, which was similar to δ15Nbulk (-4.0‰ ± 2.9‰). We concluded that a N isotope balance occurred during amino acid metabolism and that little isotope disparity occurred between the concentration-weighted TFAA and bulk N. We concluded that δ15NTFAA ≈ δ15Nbulk ≈ δ15Nsource. The mean δ15Nalanine (-4.1‰), δ15Nglutamate (-4.2‰), and δ15Nlysine (-4.0‰) were similar to the mean δ15Nbulk, which we attributed to little isotope fractionation occurring during their in situ the metabolic pathways. This suggests that δ15Nalanine, δ15Nglutamate, and δ15Nlysine in moss can be used to indicate the sources of atmospheric N deposition.

A reliable compound-specific nitrogen isotope analysis of amino acids by GC-C-IRMS following derivatisation into N-pivaloyl-iso-propyl (NPIP)esters for high-resolution food webs estimation.

The signatures of natural stable nitrogen isotopic composition (δ(15)N) of individual amino acid (AA) have been confirmed to be a potentially effective tool for elucidating nitrogen cycling and trophic position of various organisms in food webs. In the present study, a two-stage derivatisation approach of esterification followed by acylation was evaluated. The biological samples underwent acid hydrolysis and the released individual AA was derivatived into corresponding N-pivaloyl-isopropyl (NPIP) esters for nitrogen isotopic analysis in gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS). Usually, 13 individual AA derivatives were separated with fine baseline resolution based on a nonpolar gas chromatography column (DB-5ms). The minimum sample amount required under the presented conditions is larger than 20ngN on column in order to accurately determine the δ(15)N values. The δ(15)N values determined by GC-C-IRMS with a precision of better than 1‰, were within 1‰ after empirical correction compared to the corresponding measured by element analysis (EA)-IRMS. Bland-Altman plot showed highly consistency of the δ(15)N values determined by the two measurement techniques. Cation-exchange chromatography was applied to remove interfering fraction from the extracts of plant and animal samples and without nitrogen isotope fractionation during the treatment procedure. Moreover, this approach was carried out to estimate the trophic level of various natural organisms in a natural lake environment. Results highly proved that the trophic level estimated via the presented AA method well reflected the actual food web structure in natural environments.

[Sulfur isotopic signatures in leaves of Pinus massoniana Lamb. and source apportionment].

This study analyzed the inorganic sulfur (SSO4) and total sulfur (ST) content as well as the isotopic signatures (delta34SSO4 and 834ST) in leaves of Pinus massoniana lamb. collected from Guizhou and Yunnan areas. The results indicated that the SSO4 and ST content in leaves at Guiyang areas was significantly higher than that at Yunnan areas, and the content of inorganic sulfur in the leaves was found to be directly related to the concentration of ambient sulfur dioxide, but no correlation was seen between the ST content and the ambient sulfur dioxide, showing the SSO4 content in leaves was more reliable to reflect the ambient sulfur input. The average value of delta34SSO4 in leaves at Guiyang areas ( -7. 22%o) was significantly lower than that at Yunnan areas(3. 85 per thousand) , which was related to the fact that the sulfur isotopic composition of coal at Guiyang areas is lower than that at Yunnan areas. The SSO4 and ST content in leaves around Kunming steel and Qujing power plant was inversely proportional to the distance from the factories, while around Kunming steel plant the value of 83SSO4 in leaves became more negative when the distance became larger while around Qujing power plant the value of 834Sso4 became more positive when the distance became larger, indicating that the SSO4 content and delta34SSO4, in leaves around Kunming steel and Qujing power plant were controlled by coal sources of atmospheric sulfur deposition.

[Nitrogen concentrations and stable isotope in epilithic mosses to investigate atmospheric N deposition and N sources in Jiangxi Province].

Atmospheric N deposition and N sources in Jiangxi Province were investigated on the basis of the nitrogen concentrations and nitrogen isotope in epilithic mosses which collected from 11 cities of the province during 2009-2010. Mean nitrogen concentrations ranged from 2.46% to 3.48% and showed a significant regional difference. The highest was found in the northwestern of the province and the lowest in the southeastern, reflecting that the level of the atmospheric N deposition gradually decreased from the north to the south in the province. The higher N concentrations in urban mosses than in suburban mosses indicated that the urban areas received higher rates of nitrogen deposition than suburbs areas. Mosses 15N values varied from (-9.74 +/- 0.25) per thousand to (-1.96 +/- 1.30) per thousand. More negative delta15N values of urban mosses (-5.51 per thousand-9.74 per thousand) indicated that more NH3 was released from excretory wastes and sewage, while less negative delta15N values of suburban mosses (-4.81 per thousand-1.96 per thousand) suggested an important contribution from agricultural NH3 emission due to intensive fertilizer application. This research provides basic information for further study on the ecological and environmental effects of atmospheric N deposition.

Tracing sources of coal combustion using stable sulfur isotope ratios in epilithic mosses and coals from China.

In China, coal combustion is the most important source of atmospheric sulfur pollution. Moss sulfur isotopic signatures have been believed to hold source-specific information that can serve as a fingerprint to identify atmospheric sulfur sources. In cities where only local coals were combusted, we observed a good correspondence of average sulfur isotope ratios in urban mosses (Haplocladium microphyllum) to the values of local coals (δ(coals) = 1.455δ(mosses)- 3.945, R(2) = 0.975, p = 0.01). But if different types of coals were combusted, we did not know whether moss sulfur isotope ratios can indicate mixed coals. To confirm this, using a mixing model we estimated the ratios of imported coal to local coals at cities where both coals were used. We found that the estimated ratios at large cities (>1 million people) where both coals were used were similar to the reported ratios in their respective provinces. For small cities (<0.5 million people) in Jiangxi Province and other provinces, the estimated ratios were higher than the reported ratios because the relatively cheaper local coals were less used in all the small cities except in cities where local coal deposits were found nearby. The comparison results showed that moss sulfur isotope is a useful tool for indicating coal-derived sulfur even in cities where mixed coals were combusted.

Sulfur isotopic signatures in rainwater and moss Haplocladium microphyllum indicating atmospheric sulfur sources in Nanchang City (SE China).

Sulfur source identification previously reported has been based on sulfur isotopic ratios in either rainwater or mosses. The δ(34)S values of rainwater sulfate and the epilithic moss Haplocladium microphyllum in Nanchang region (China) were determined for comparisons and used to delineate atmospheric sulfur sources. At the urban and rural sites, similar mean δ(34)S values were observed between rainwater sulfate (+1.6‰ and -0.2‰, respectively) and epilithic mosses (+1.7‰ and +0.6‰, respectively), suggesting that mosses acquire δ(34)S values similar to those found for rainwater sulfate. This has further demonstrated that moss δ(34)S signatures hold valuable source-specific information as rainwater δ(34)S values do. The δ(34)S values of both rainwater sulfate and epilithic mosses indicated that atmospheric sulfur in Nanchang region was mainly associated with coal combustion. The lower δ(34)S values at the rural site can be explained by higher contribution of local coals (lower δ(34)S values relative to those of north Chinese coals) and biogenic sulfur.

Nitrogen isotope variations in camphor (Cinnamomum Camphora) leaves of different ages in upper and lower canopies as an indicator of atmospheric nitrogen sources.

Nitrogen isotopic composition of new, middle-aged and old camphor leaves in upper and lower canopies has been determined in a living area, near a motorway and near an industrial area (Jiangan Chemical Fertilizer Plant). We found that at sites near roads, more positive δ(15)N values were observed in the camphor leaves, especially in old leaves of upper canopies, and ∆δ(15)N=δ(15)N(upper)-δ(15)N(lower)>0, while those near the industrial area had more negative δ(15)N values and ∆δ(15)N<0. These could be explained by two isotopically different atmospheric N sources: greater uptake from isotopically heavy pools of atmospheric NO(x) by old leaves in upper canopies at sites adjacent to roads, and greater uptake of (15)N-depleted NH(y) in atmospheric deposition by leaves at sites near the industrial area. This study presents novel evidence that (15)N natural abundance of camphor leaves can be used as a robust indicator of atmospheric N sources.