Urinary Metabolites of Polycyclic Aromatic Hydrocarbons of Rural Population in Northwestern China: Oxidative Stress and Health Risk Assessment.

Polycyclic aromatic hydrocarbon (PAH) exposure is suspected to be linked to oxidative damage. Herein, ten PAH human exposure biomarkers [hydroxylated PAH metabolites (OH-PAHs)] and five oxidative stress biomarkers (OSBs) were detected in urine samples collected from participants living in a rural area (n = 181) in Northwestern China. The median molar concentration of ΣOH-PAHs in urine was 47.0 pmol mL-1. The 2-hydroxynaphthalene (2-OHNap; median: 2.21 ng mL-1) was the dominant OH-PAH. The risk assessment of PAH exposure found that hazard index (HI) values were <1, indicating that the PAH exposure of rural people in Jingyuan would not generate significant cumulative risks. Smokers (median: 0.033) obtained higher HI values than nonsmokers (median: 0.015, p < 0.01), suggesting that smokers face a higher health risk from PAH exposure than nonsmokers. Pearson correlation and multivariate linear regression analysis revealed that ΣOH-PAH concentrations were significant factors in increasing the oxidative damage to deoxyribonucleic acid (DNA) (8-hydroxy-2'-deoxyguanosine, 8-OHdG), ribonucleic acid (RNA) (8-oxo-7,8-dihydroguanine, 8-oxoGua), and protein (o, o'-dityrosine, diY) (p < 0.05). Among all PAH metabolites, only 1-hydroxypyrene (1-OHPyr) could positively affect the expression of all five OSBs (p < 0.05), suggesting that urinary 1-OHPyr might be a reliable biomarker for PAH exposure and a useful indicator for assessing the impacts of PAH exposure on oxidative stress. This study is focused on the relation between PAH exposure and oxidative damage and lays a foundation for the study of the health effect mechanism of PAHs.

Bioadsorption, bioaccumulation and biodegradation of antibiotics by algae and their association with algal physiological state and antibiotic physicochemical properties.

Bioadsorption, bioaccumulation and biodegradation processes in algae, play an important role in the biomagnification of antibiotics, or other organic pollutants, in aquatic food chains. In this study, the bioadsorption, bioaccumulation and biodegradation of norfloxacin [NFX], sulfamethazine [SMZ] and roxithromycin [RTM]) is investigated using a series of culture experiments. Chlorella vulgaris was exposed to these antibiotics with incubation periods of 24, 72, 120 and 168 h. Results show the bioadsorption concentration of antibiotics in extracellular matter increases with increasing alkaline phosphatase activity (AKP/ALP). The bioaccumulation concentrations of NFX, SMZ and RTM within cells significantly increase after early exposure, and subsequently decrease. There is a significant positive antibiotics correlation to superoxide dismutase (SOD), the photosynthetic electron transport rate (ETR) and maximum fluorescence after dark adaptation (Fv/Fm), while showing a negative correlation to malondialdehyde (MDA). The biodegradation percentages (Pb) of NFX, SMZ and RTM range from 39.3 - 97.2, 41.3 - 90.5, and 9.3 - 99.9, respectively, and significantly increase with increasing Fv/Fm, density and chlorophyll-a. The accumulation of antibiotics in extracellular and intracellular substances of C. vulgaris is affected by antibiotic biodegradation processes associated with cell physiological state. The results succinctly explain relationships between algal growth during antibiotics exposure and the bioadsorption and bioaccumulation of these antibiotics in cell walls and cell matter. The findings draw an insightful understanding of the accumulation of antibiotics in algae and provide a scientific basis for the better utilization of algae treatment technology in antibiotic contaminated wastewaters. Under low dose exposures, the biomagnification of antibiotics in algae is affected by bioadsorption, bioaccumulation and biodegradation.

Physiological and Cellular Ultrastructural Responses of Sesuvium portulacastrum under Cd Stress Grown Hydroponically.

This study aimed to investigate the physiological and cellular mechanisms of Sesuvium portulacastrum under heavy metal stress to evaluate possible tolerance and adaptation mechanisms in a metal-polluted environment. The physiological and cellular ultrastructural responses of S. portulacastrum were studied hydroponically under exposure to a range of cadmium (Cd) concentrations (50 µM to 600 µM) for 28 days. The activity of antioxidant enzymes like catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD), changes in chlorophyll, and cellular ultrastructural content were examined. There was no significant difference in chlorophyll content in the leaf under the stress of 300 µM, but 400 µM and 600 µM Cd stress showed significantly decreased chlorophyll content. The SOD activity indicates an increase under the Cd stress of 100 µM for leaves, 300 µM for stems, and 50 µM for roots; after that, the SOD activity gradually decreased with increasing Cd concentrations. But POD activity was considerably increased with increasing Cd stress. CAT activity showed a gradual increase in concentrations until 300 µM of Cd stress and then decreased sharply in roots, stems, and leaf tissues. Cd stress had a considerable impact on the structure of the roots, stems, and leaves cells, such as distorted and thinner cell walls and the deformation of chloroplasts, mitochondria, and other organelles. Therefore, the increased number of nucleolus in the cell nucleus suggests that cells may be able to maintain their protein synthesis in a stressful environment. This study concludes that SOD is the dominant antioxidant enzyme activity during low Cd toxicity (<100 µM), while POD is the dominant enzyme activity during higher Cd toxicity (>100 µM).

Bioaccumulation and toxicity of perfluorooctanoic acid and perfluorooctane sulfonate in marine algae Chlorella sp.

The ocean is an important sink for perfluorinated alkyl acids (PFAAs), but the toxic mechanisms of PFAAs to marine organisms have not been clearly studied. In this study, the growth rate, photosynthetic activity, oxidative stress and bioaccumulation were investigated using marine algae Chlorella sp. after the exposure of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate acid (PFOS). The results showed that PFOA of <40 mg/L and PFOS of <20 mg/L stimulated algal reproduction, and high doses inhibited the algal growth. The absorbed PFOA and PFOS by algal cells damaged cell membrane and caused metabolic disorder. The photosynthesis activity was inhibited, which was revealed by the significantly reduced maximal quantum yield (Fv/Fm), relative electron transfer rate (rETR) and carbohydrate synthesis. However, the chlorophyll a content increased along with the up-regulation of its encoding genes (psbB and chlB), probably due to an overcompensation effect. The increase of ROS and antioxidant substances (SOD, CAT and GSH) indicated that PFOA and PFOS caused oxidative stress. The BCF of marine algae Chlorella sp. to PFOA and PFOS was calculated to be between 82 and 200, confirming the bioaccumulation of PFOA and PFOS in marine algae. In summary, PFOA and PFOS can accumulate in Chlorella sp. cells, disrupt photosynthesis, trigger oxidative stress and inhibit algal growth. PFOS shows higher toxicity and bioaccumulation than PFOA. The information is important to evaluate the environmental risks of PFAAs.

Bioaccumulation and emission of organophosphate esters in plants affecting the atmosphere's phosphorus cycle.

The imbalance of atmospheric, terrestrial and aquatic phosphorus budgets remains a research conundrum and global concern. In this work, the uptake, distribution, bioaccumulation and emission of organophosphate esters (OPEs) by clove trees (Syzygium aromaticum), lemon trees (Citrus limon) and cape jasmine trees (Gardenia jasminoides var. fortuniana) was investigated as conduits for phosphorus transfer or sinks and sources. The objective was to assess the role OPEs in soils play as atmospheric phosphorus sources through plant bioaccumulation and emission. Results demonstrated OPEs in experimental soil plots ranging from 0.01 to 81.0 ng g-1 dry weight, were absorbed and transported through plants to the atmosphere. The total emission of OPEs varied greatly from 0.2 to 588.9 pg g-1 L-1 h-1, with a mean of 47.6 pg g-1 L-1 h-1. There was a negative linear relationship between the concentrations of total phosphorus and four OPEs, tri-iso-butyl phosphate, tri-n-butyl phosphate, tris (2-chloroisopropyl) phosphate and tripentyl phosphate. Trimethyl phosphate levels were positively correlated with total nitrogen, and the concentrations of tri-iso-butyl phosphate, tri-n-butyl phosphate, tris (2-chloroisopropyl) phosphate and tripentyl phosphate decreased along with available potassium in leaves after 72 h. There was a significantly positive linear relationship between higher emission concentrations of OPEs and the emission factor of OPEs concentration (F = 4.2, P = 0.002), with lower emissions of OPEs and the bioaccumulation of OPEs in leaves (F = 4.8, P = 0.004). OPEs releases to the atmosphere were enriched in aerosols, and participate in atmospheric chemical reactions like photolysis, thereby affecting the phosphorus balance and cycling in the atmosphere.

Toxicity of perfluooctane sulfonate (PFOS) and perfluorobutane sulfonate (PFBS) to Scenedesmus obliquus: Photosynthetic characteristics, oxidative damage and transcriptome analysis.

With the wide application as an alternative for perfluorooctane sulfonate (PFOS), perfluorobutane sulfonate (PFBS) has been frequently detected in the aquatic environment. However, the aquatic toxicity of PFBS is still poorly understood. The present work studied the aquatic toxicity of PFBS using freshwater algae Scenedesmus obliquus (S. obliquus) as indicator, and the toxicity of PFOS was also examined for comparison. The results showed that PFBS exhibited much lower toxicity to S. obliquus than PFOS. The EC50 value was higher than 1800 mg L-1 after 7 days of exposure to PFBS. By contrast, a much lower EC50 value of 136.69 mg L-1 was obtained for PFOS. Photosynthetic efficiency analyzed by chlorophyll fluorescence also verified that PFOS induced a higher toxic effect on the algae than PFBS. The malondialdehyde, catalase and superoxide dismutase results indicate that PFOS exposure led to the accumulation of ROS, which caused oxidative damage to the algae, thereby resulting in the inhibition in the growth and photosynthesis of the algae. Furthermore, transcriptome analysis indicates that the significant down-regulation of key genes related to photosynthesis induced by PFOS was the fundamental mechanism for the inhibition in photosynthetic efficiency and biomass growth of S. obliquus.

Distribution and Relationships of Polycyclic Aromatic Hydrocarbons (PAHs) in Soils and Plants near Major Lakes in Eastern China.

The distributions and correlations among polycyclic aromatic hydrocarbons (PAHs) in soils and plants were analyzed. In this study, 9 soil samples and 44 plant samples were collected near major lakes (Hongze Lake, Luoma Lake, Chaohu, Changhu, Danjiangkou Reservoir, Wuhan East Lake, Longgan Lake, Qiandao Lake and Liangzi Lake) in eastern China. The following results were obtained: The total contents of PAHs in soil varied from 99.17 to 552.10 ng/g with an average of 190.35 ng/g, and the total contents of PAHs in plants varied from 122.93 to 743.44 ng/g, with an average of 274.66 ng/g. The PAHs in soil were dominated by medium- and low-molecular-weight PAHs, while the PAHs in plants were dominated by low-molecular-weight PAHs. The proportion of high-molecular-weight PAHs was the lowest in both soil and plants. Diagnostic ratios and principal component analysis (PCA) identified combustion as the main source of PAHs in soil and plants. The plant PAH monomer content was negatively correlated with Koa. Acenaphthylene, anthracene, benzo[k]fluoranthene, benzo[b]fluoranthene and dibenzo[a,h]anthracene were significantly correlated in plants and soil. In addition, no significant correlation between the total contents of the 16 PAHs and the content of high-, medium-, and low-molecular-weight PAHs in plants and soil was found. Bidens pilosa L. and Gaillardia pulchella Foug in the Compositae family and cron in the Poaceae family showed relatively stronger accumulation of PAHs, indicating their potential for phytoremediation.

How reliable is chlorophyll-a as algae proxy in lake environments? New insights from the perspective of n-alkanes.

Chlorophyll-a (Chl-a) has been employed as the "golden proxy" of algae biomass and algae cell densities in lake environments for many years. However, how reliable Chl-a is as algae proxy in lake environments needs further evaluation. Here, we take the eutrophic Lake Chaohu and 46 lakes and reservoirs across China as objects on temporal and spatial scales, respectively, to resolve this issue from the perspective of n-alkanes. Our results showed that Chl-a ranged from 10.5 to 735 µg∙L-1 with a geometric mean of 92.4 µg∙L-1 in Lake Chaohu. There were no statistically significant correlations between Chl-a and algae cell densities in all seasons (Pearson's correlation, p > 0.05), and also for macrophytes and terrestrial plants input (p > 0.05). It was related to the complex changes of environmental factors. By contrast, Chl-a ranged from 7.1 to 1608 µg∙L-1 with a geometric mean of 125 µg∙L-1 in nationwide lakes and reservoirs, and its occurrence was not only related to algae, but also associated with macrophytes and terrestrial plants (p < 0.05). In summary, Chl-a can be applied as an algae proxy, but its application is subject to certain restrictions. Besides, the multiple sources of Chl-a in lake environments may result in an overestimation of algae cell densities. Compared to Chl-a, biogenic n-heptadecane (bio C17) could be regarded as a potential alternative. Hence, we compared the advantages and disadvantages of bio C17 and Chl-a in the aspects of specificity, accuracy, sensitivity and applicability. We found that for most scenarios, their limitations could be surmounted by each other, but failed in some scenarios. Accordingly, an ensemble proxy system may be used for more reliable representation of algae in lake environments.

Ecological risk assessment of toxic metal(loid)s for land application of sewage sludge in China.

Sewage sludge, including those after biological or thermochemical treatments, has the potential to be used as fertilizers for recycle of resources. However, its potential ecological risk is also of great concern to policy making. This study employed comprehensive ecological risk assessment (ERA) methods to evaluate the risk caused by the toxic metal(loid)s in sewage sludge throughout China. The conventional geo-accumulation index and potential ecological risk index revealed that cadmium (Cd) and mercury (Hg) were of significant concern in treating sewage sludge before land application, but chromium (Cr) and zinc (Zn) were preferred by potential affected proportion (PAF) and overall risk probability (ORP) of species sensitivity distribution (SSD). Because SSD considered both the community and the ecotoxicity of toxic metal(loid)s, it was more advantageous and promising in assessing ecological risks caused by land application of sewage sludge. Based on the predicted no-effect concentration (PNEC) of toxic metal(loid) calculated by hazardous concentration that cause death of 50% of species (HC50) by SSD, the maximum allowable disposal amount (MADA) of sewage sludge in the whole China indicated that chromium (Cr) should be totally eliminated because of its high risks in the present background soil. After excluding Cr, the MADA of sewage sludge in China was 3.24 × 106 t and 6.47 × 107 t under land application scenarios with high and low ecological risks, respectively. Additionally, the MADA could be increased by mixing sewage sludge with deeper soil in wider areas. This study emphasized that local laws and regulations on land application of sewage sludge and the subsequent ERA system need to be addressed in the future.

Can biogenic n-heptadecane be utilized to represent algae cell density dynamics in water environment? Evidences from field investigation and laboratory validation.

The monitoring and prediction of algae cell density are the fundamental supports for eutrophication management. As the molecular marker of algae, n-heptadecane has been successfully utilized to reflect algae biomass in sedimentary studies. However, whether biogenic n-heptadecane (bio C17) can be utilized to represent algae cell density dynamics in water environment still remains an issue. Current study aims to provide novel evidences from both field investigation and laboratory validation for it. Firstly, we found a strinkingly positive correlation between algae cell density dynamics and bio C17 variations (p = 4.34 × 10-10) via meta-analysis using field dataset in Lake Chaohu. Then, we selected Microcystis aeruginosa, Chlorella vulgaris and Melosira sp. as model species of cyanobacteria, green algae and diatom, respectively, for laboratory validation. Our results illustrated that n-heptadecane was synchronized with the growth for cyanobacteria and green algae but not for diatom. The association between bio C17 and algae cell density was species-dependent, and the relationship between bio C17 and cell density was linear within 107 cells∙mL-1. Therefore, we established and optimized a generalized additive model to fit observed algae cell density in Lake Chaohu. In the optimal model, bio C17, Pielou evenness index J and Shannon-Wiener index H' were included, totally explaining 66% of the variance of algae cell density. Model comparisons revealed that considering algae community could indeed improve the interpretation of algae cell density in natural environment. In conclusion, our study provided novel evidences that bio C17 can be utilized to represent the cell density dynamics of cyanobacteria and green algae in the environment.

Comparing Photoactivities of Dissolved Organic Matter Released from Rice Straw-Pyrolyzed Biochar and Composted Rice Straw.

Here, we systematically compared the photoactivity and photobleaching behavior between dissolved black carbon (DBC) from rice straw biochar and leached dissolved organic carbon (LDOC) from rice straw compost using complementary techniques. The Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis showed that DBC was dominated by polycyclic aromatic (55.1%) and tannin-like molecules (24.1%), while LDOC was dominated by lignin-like (58.9%) and tannin-like molecules (19.7%). Under simulated sunlight conditions, DBC had much higher apparent quantum yields for 3DOM* and 1O2 but much lower apparent quantum yields for •OH than LDOC. After a 168 h irradiation, the total number of LDOC formulas identified by FT-ICR MS decreased by 40.1% with concurrent increases in O/C and H/C ratios and also decreases in double bond equivalence minus oxygen (DBE - O) and average molecular weight identified by gel permeation chromatography. However, despite the large decreases in UVA254 and DOC, the total number of DBC formulas decreased only by 12.0% with nearly unchanged O/C ratio, DBE - O values, molecular weight distribution, and benzenepolycarboxylic aromatic condensation (BACon) index regardless of the decreased percentage of condensed aromatic carbon (ConAC %). Compared with LDOC, the photolysis of DBC was much less oxidative and destructive mainly via breakup of a small portion of the highly condensed aromatic rings, probably accompanied by photodecarboxylation.

Dustfall-bound polycyclic aromatic hydrocarbons (PAHs) over the fifth largest Chinese lake: residual levels, source apportionment, and correlations with suspended particulate matter (SPM)-bound PAHs in water.

Residual levels and temporal-spatial distribution characteristics of polycyclic aromatic hydrocarbons (PAHs) in dustfall were studied at the seasonal scale between June 2010 and May 2011 in the fifth largest shallow lake in China. PAHs flux of atmospheric deposition and the impact on the PAHs in the lake water column were estimated. The major sources of PAHs were identified by multiple methods. We found that (1) the seasonal residual levels of 16 priority controlled PAHs (PAH16) were spring (8.89 ± 3.93 µg g-1) > summer (6.68 ± 4.31 µg g-1) > winter (6.06 ± 2.95 µg g-1) > autumn (3.55 ± 2.21 µg g-1). (2) Significant positive correlations were found between the PAH levels in the dustfall and the suspended particle material (SPM) content, as well as between the deposition flux and the PAH content in the water in all four seasons. (3) Vehicle emissions, coal combustion, biomass combustion, and coke ovens were the four major sources in Lake Chaohu, accounting for 12.7%, 40.9%, 14.5%, and 31.9% of the total PAHs, respectively. (4) Compared to long-distance trajectories, short-distance trajectories played a more important role in the external sources of atmospheric PAHs in the region of Lake Chaohu.

Dissipation Behavior, Residue, and Risk Assessment of Benziothiazolinone in Apples.

Benziothiazolinone is the first independently developed fungicide in China. It has been used to effectively control fungal diseases in a variety of fruits, vegetables, and crops. In this study, the degradation behavior and final residue of benziothiazolinone in apples is discussed, and the dietary risk to consumers was evaluated. High-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to determine benziothiazolinone residues in apple samples from eight different regions of China. The average recovery of benziothiazolinone in apples was 85.5-100.2%, and the relative standard deviation (RSD) was 0.8-14.9%. The limits of the method of quantification of benziothiazolinone in apples was 0.01 mg/kg. Under good agricultural practices (GAP) conditions, the final residues of benziothiazolinone in apples were below 0.01 mg/kg, lower than the maximum residual limit (MRL) of China. Although the degradation half-lives of benziothiazolinone were 23.9 d-33.0 d, the risk quotient (RQ) of benziothiazolinone was 15.5% by calculating the national estimated daily intake and comparing it with the acceptable daily intake. These results suggested that under GAP conditions, the intake of benziothiazolinone from apples exhibits an acceptably low health risk on consumers.

Variations of root-associated bacterial cooccurrence relationships in paddy soils under chlorantraniliprole (CAP) stress.

Root-associated microbiomes are beneficial for plant development and health. However, the assembly of root-associated bacterial communities and their feedback under chlorantraniliprole (CAP) stress are unclear. This study investigated the response of root-associated bacterial microbiota to CAP dosage during the two developmental phases of rice. The results showed that CAP application had little effect on the bacterial diversity of bulk and rhizosphere soils, whereas that of the endosphere samples demonstrated a large variability. Moreover, the CAP stress exhibited less influence than the plant compartment and developmental stage contributing to microbiome variation. The core bacterial co-occurrence relationships also changed with the CAP application, especially, in the endosphere of the roots. These results further elucidate the impacts of CAP application on root-associated bacterial communities in intensive agricultural ecosystems and provide new insights for CAP ecological risk assessments.

Mercury and methylmercury in China's lake sediments and first estimation of mercury burial fluxes.

Lake sediments are key materials for mercury deposition and methylation. To understand the mercury concentrations in China's lakes, 100 lake surface sediment samples were collected from 35 lakes in 2014. Total mercury (THg), methylmercury (MeHg) concentrations and the annual Hg burial rates in lake sediments were measured. THg and MeHg concentrations in the sediment ranged from 13.6 to 1488 ng‧g-1 and 0.05 to 1.70 ng‧g-1, respectively, and urban lakes reported most high values, indicating direct anthropogenic inputs. The Inner Mongolia-Xinjiang Region (MX) and Qinghai-Tibet Plateau Region (QT) reported relatively lower mercury burial rates, while the Eastern Plain Region (EP), Northeast Mountain and Plain Region (NE), and Yunnan-Guizhou Plateau Region (YG) reported higher mercury burial rates. Regional variances of THg burial fluxes were dominated by atmospheric deposition, terrestrial input, and sediment accumulation rates in different lakes. In 2014, the estimated average THg burial rate in China's lakes was 139 µg‧m-2‧yr-1, comparable to the average in mid-latitude North America in recent years; however, due to China's much smaller lake area relative to NA, the annual THg burial flux in China was much lower than that in North America. EP and NE, where most freshwater aquatic products in China are harvested, accounted for 58.2% and 22.9%, respectively, of the THg burial flux. High sedimentary MeHg concentrations and MeHg:THg ratios were reported in most of the NE but low MeHg concentrations and MeHg:THg ratios were reported in EP. MeHg concentrations and MeHg:THg ratios were positively correlated with water COD levels and negatively correlated with average temperature. The results of this study indicate that in addition to the adjacent seas, lake sediments are an important mercury sink in China's aquatic environment, which could cause health risks due to MeHg intake, especially in NE.

The impacts of algae biological pump effect on the occurrence, source apportionment and toxicity of SPM-bound PAHs in lake environment.

The algae biological pump (ABP) effect for hydrophobic organic contaminants in deep oligotrophic lakes and oceans has been well studied. Suspended particulate matter (SPM) plays a connective role in ABP processes. However, little is known about the impacts of ABP effect on the occurrence, source apportionment and toxicity of SPM-bound polycyclic aromatic hydrocarbons (PAHs) in a typically shallow eutrophic lake under strong anthropogenic emissions of PAHs. In this study, we study this gap knowledge on the eutrophic Lake Chaohu, China. SPM-bound PAHs in Lake Chaohu were controlled by anthropogenic emissions in all seasons. Apparent ABP effect only occurred in spring and summer in lake area. Algae blooms in spring and summer significantly increased 46.5% ± 7.9% (mean ± standard deviation) and 19.8% ± 2.4% of Σ21 SPM-bound PAHs, and greatly enhanced their toxicity (1.98 ± 0.46 times in spring and 32.9% ± 4.2% in summer). Therefore, there need more attentions focusing on the coupling effect of persistent toxic substances such as PAHs and harmful algae blooms in aquatic environment for sustainable development. The apparent ABP effect had little influence on their source apportionment. However, it may cause a regime shift for the source apportionment on a short-term scale. Further study could pay more attentions on in-depth and short-term studies on ABP effect.

Suspended particulate matter (SPM)-bound polycyclic aromatic hydrocarbons (PAHs) in lakes and reservoirs across a large geographical scale.

Suspended particulate matter (SPM) plays a key role in the environmental fate of polycyclic aromatic hydrocarbons (PAHs) in lake environment. However, less is known about the occurrence, compositions and sources of SPM-bound PAHs as well as the correlations between SPM-bound PAHs and different suspended particulate organic matter (SPOM) on large geographical scale. In this study, we focused on the SPM-bound PAHs in 46 lakes and reservoirs across China to fill this gap. Our results showed that the concentrations of Σ20 PAHs ranged from 334 to 38427 ng·g-1 with a geometric mean (GM) of 3915 ng·g-1. The occurrence of SPM-bound PAHs in this study was at a moderate level with large variations, which was associated with location and water depth according to linear discriminant analysis (LDA). Phenanthrene (Phe) was investigated as the overwhelming species with a GM of 1777 ng·g-1, and was followed by fluoranthene (Fla), fluorene (Flu) and pyrene (Pyr) with GMs of 499 ng·g-1, 276 ng·g-1 and 184 ng·g-1, respectively. The profiles of SPM-bound PAHs were primarily dominated by low-ring PAHs ranging from 56.0% to 97.1% (85.5% ± 7.7%, mean ± standard deviation). Four diagnostic ratios were applied for preliminary diagnoses, but inconsistent results were obtained in most samples. Ridge regression was applied to ascertain the potential influences of different SPOM on SPM-bound PAHs. The results revealed that the presence of SPM-bound PAHs was not only influenced by anthropogenic emissions, but also associated with biogenic organic matter. Our results provided a higher explanation than those just preliminarily estimated by total organic carbon (TOC). Nevertheless, there still exist over 50% of variance unexplained for most PAHs, and further study could focus more on the information of SPOM structures and potential local effects.

Geographical location and water depth are important driving factors for the differences of suspended particulate organic matter (SPOM) in lake environment across nationwide scale: Evidences from n-alkane fingerprints.

Suspended particulate organic matter (SPOM) plays a connective role in global biogeochemical carbon cycles and energy flows in aquatic ecosystems. However, little is known about the occurrence and source of SPOM in lake environment and their driving factors across nationwide scale. Here, we utilize the molecular markers of n-alkanes and their fingerprints in 46 typical lakes and reservoirs with different water depths across China from both sides of the Hu Line to study this issue. Σ29n-alkanes, Σ biogenic n-alkanes and Σ anthropogenic n-alkanes ranged from 104.8 to 10332 ng·L-1, from 88.5 to 4843 ng·L-1, and from 16.2 to 5488 ng·L-1, respectively. Their occurrences were only associated with water depth. Then, we compared the differences of carbon-chain distribution of both biogenic and anthropogenic n-alkanes and related proxies in different lake groups. The profiles of different biogenic and anthropogenic n-alkanes posed large differences in different lake groups. Finally, linear discriminant analysis (LDA) was applied to test the possible effects of geographical location and water depth on the holistic differences of SPOM in different lakes and reservoirs across China. The results illustrated that both geographical location and water depth were important driving factors for the holistic differences of SPOM in different lakes and reservoirs across China. Intensive anthropogenic activities narrowed the differences between shallow and deep lakes in eastern China. In conclusion, this study provided new insights into the driving factor analysis of SPOM in lakes and reservoirs on large scale.

Residual concentrations and ecological risks of neonicotinoid insecticides in the soils of tomato and cucumber greenhouses in Shouguang, Shandong Province, East China.

Neonicotinoid insecticides (NNIs) are the most widely used insecticides in China and worldwide. Continuous use of NNIs can lead to their accumulation in soil, causing potential ecological risks due to their relatively long half-life. We used liquid chromatography-tandem mass spectrometry (LC-MS/MS) to investigate the residual levels of nine neonicotinoids in greenhouse soils in Shouguang, East China, at different soil depths and with different crops (tomato and cucumber) after varying periods of cultivation. Seven neonicotinoids were detected in the soils of the tomato greenhouses and six were detected in the soils of the cucumber greenhouses, with total concentrations ranging from 0.731 to 11.383 µg kg-1 and 0.363 to 19.224 µg kg-1, respectively. In all samples, the neonicotinoid residues in the soils cultivated for 8-9 years were lower than in those cultivated for 2 years and 14-17 years. In the tomato greenhouse soils, the residual levels of NNIs were highest in the topsoil, with progressively lower concentrations found with depth. Under cucumber cultivation, the NNI residue levels were also highest in the topsoil but there was little difference between the middle and lower soil layers. Total organic carbon (TOC) decreased with soil depth while pH showed the opposite trend, showing a significant negative correlation in both types of soils (tomato soils ρ = -0.900, p = .001; cucumber soils ρ = -0.883, p = .002). Furthermore, TOC was significantly positively correlated, and pH was negatively correlated, with total NNI concentrations in both types of soils (TOC: tomato soils ρ = 0.800, p = .010; cucumber soils ρ = 0.881, p = .004; pH: tomato soils ρ = -0.850, p = .004; cucumber soils ρ = -0.643, p = .086). The results of an ecological risk analysis showed that acetamiprid represents a particularly high toxicity risk in these soils. Based on our analysis, NNI residues in the soils of tomato greenhouses and their associated ecological risks deserve more attention than those of cucumber greenhouse soils.

Tissue distribution, bioaccumulation, and carcinogenic risk of polycyclic aromatic hydrocarbons in aquatic organisms from Lake Chaohu, China.

Freshwater products consumed in the diet are among the major sources of exposure of humans to polycyclic aromatic hydrocarbons (PAHs). In this study, eight freshwater organisms and environmental samples were collected from Chaohu Lake, the fifth-largest lake in China. The levels of PAHs in the collected organisms were measured using GC-MS. Tissue distribution characteristics in three fish species were studied. Relationship between residual levels and environment concentrations were analyzed and bioaccumulation effect and influencing factors were identified. Finally, the potential carcinogenic risk of aquatic product intake was estimated. The concentrations of ΣPAHs in aquatic organisms varied from 18.4 to 398 ng/g, with a mean value of 157 ± 125 ng/g. For carp, the highest ΣPAHs level was detected in the brain with concentration of 591 ng/g. For topmouth culter, and bighead fish, the organs with the greatest ΣPAHs concentration were gills (440 ng/g) and muscles (200 ng/g), respectively. Significant correlations were found between the PAH content in environment media including water, SPM, sediment and PAH content in aquatic animals. The calculation of food web magnification factors and risk assessment indicates that although the PAH concentration diluted with the increase of the trophic level, PAHs exposure through the aquatic products intake still poses potential carcinogenic risk. The incremental lifetime cancer risk values were 7.68 × 10-6 and 4.75 × 10-6 in urban and rural populations, respectively.