Sources, Occurrences, and Risks of Polycyclic Aromatic Hydro-Carbons (PAHs) in Bangladesh: A Review of Current Status

Polycyclic aromatic hydrocarbons (PAHs) pollution has emerged as a significant environmental issue in Bangladesh in the recent years, driven by both economic and population growth. This review aims to investigate the current trends in PAHs pollution research, covering sediments, water, aquatic organisms, air particles, and associated health risks in Bangladesh. A comparative analysis with PAHs research in other countries is conducted, and potential future research directions are explored. This review suggests that the research on PAHs pollution in Bangladesh is less well studied and has fewer research publications compared to other countries. Dominant sources of PAHs in Bangladesh are fossil fuel combustion, petroleum hydrocarbons, urban discharges, industrial emissions, shipbreaking, and shipping activities. The concentrations of PAHs in sediments, water, air particles, and aquatic organisms in Bangladesh were found to be higher than those in most of the other countries around the world. Therefore, coastal sediments showed higher PAHs pollution than urban areas. Health risk assessments reveal both carcinogenic and non-carcinogenic risks to residents in Bangladesh due to the consumption of aquatic organisms. According to this investigation, it can be concluded that there are considerably higher PAHs concentrations in different environmental compartments in Bangladesh, which have received less research attention compared with other countries of the world. Considering these circumstances, this review recommends that future PAHs pollution research directions should focus on aquatic ecosystems, shipbreaking areas, air particles, and direct exposure to human health risks. Therefore, this study recommends addressing the identification of PAH sources, bioaccumulation, biomagnification in the food web, and biomarker responses of benthic organisms in future PAHs pollution research

A review on perfluoroalkyl acids studies: Environmental behaviors, toxic effects, and ecological and health risks

Perfluoroalkyl acids (PFAAs) are emerging persistent organic pollutants that are globally distributed in the environment. In the present review, the occurrence of PFAAs and their behavior in aquatic ecosystem were summarized, and the health and ecological risk assessment and the multimedia fate simulation were investigated. PFAAs are most likely to exist in the aqueous phase, and PFAAs in atmosphere are also able to enter water bodies through diffusion and wet and dry deposition and eventually become widely distributed in various environmental media. The air-solid partition is considered to be one of the major factors in the long-distance transportation of the pollutants. The pKa values and organic carbon fraction of the sediment could influence the partition of PFAAs between water and sediment. Otherwise, PFAAs have teratogenic, mutagenic and other toxic effects and they could be accumulated by biota, and magnified through trophic level. The ecological and health risks of PFOA and PFOS were assessment. In order to explore the partition mechanism and reduce the uncertainty of the simulation of the transport, transformation and fate, the experimental methods on physicochemical properties of PFAAs should be developed. Moreover, further studies on toxicities of PFAAs are necessary for health and ecological risk assessment

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

Multimedia fate modeling of perfluorooctanoic acid (PFOA) and perfluorooctane sulphonate (PFOS) in the shallow lake Chaohu, China

Freshwater shallow lake ecosystems provide valuable ecological services to human beings. However, these systems are subject to severe contamination from anthropogenic sources. Per- and polyfluoroalkyl substances (PFASs), including perfluorooctanoic acid (PFOA) and perfluorooctane sulphonate (PFOS), are among the contaminants that have received substantial attention, primarily due to abundant applications, environment persistence, and potential threats to ecological and human health. Understanding the environmental behavior of these contaminants in shallow freshwater lake environments using a modeling approach is therefore critical. Here, we characterize the fate, transport and transformation of both PFOA and PFOS in the fifth largest freshwater lake in China (Chaohu) during a two-year period (2013–2015) using a fugacity-based multimedia fate model. A reasonable agreement between the measured and modeled concentrations in various compartments confirms the model's reliability. The model successfully quantifies the environmental processes and identifies the major sources and input pathways of PFOA and PFOS to the Chaohu water body. Sensitivity analysis reveals the critical role of nonlinear Freundlich sorption, which contributes to a variable fraction of the model true uncertainty in different compartments (8.1%–93.6%). Through additional model scenario analyses, we further elucidate the importance of nonlinear Freundlich sorption that is essential for the reliable model performance. We also reveal the distinct composition of emission sources for the two contaminants, as the major sources are indirect soil volatilization and direct release from human activities for PFOA and PFOS, respectively. The present study is expected to provide implications for local management of PFASs pollution in Lake Chaohu and to contribute to developing a general model framework for the evaluation of PFASs in shallow lakes

Estimation of the long-term nutrient budget and thresholds of regime shift for a large shallow lake in China

In this study, we apply an integrated empirical and mechanism approach to estimate a comprehensive long-term (1953-2012) total nitrogen (TN) and total phosphorus (TP) loading budget for the eutrophic Lake Chaohu in China. This budget is subsequently validated, firstly, by comparing with the available measured data in several years, and secondly, by model simulations for long-term nutrient dynamics using both Vollenweider (VW) model and dynamic nonlinear (DyN) model. Results show that the estimated nutrient budget is applicable for further evaluations. Surprisingly, nutrient loading from non-point sources (85% for TN and 77% for TP on average) is higher than expectation, suggesting the importance of nutrient flux from the soil in the basin. In addition, DyN model performs relatively better than VW model, which is attributed to both the additional sediment recycling process and the parameters adjusted by the Bayesian-based Markov Chain Monte Carlo (MCMC) method. DyN model further shows that the TP loading thresholds from the clear to turbid state (631.8 ± 290.16 t y-1) and from the turbid to clear state (546.0 ± 319.80 t y-1) are significantly different (p <0.01). Nevertheless, the uncertainty ranges of the thresholds are largely overlapped, which is consistent with the results that the eutrophication of Lake Chaohu is more likely to be reversible (74.12%) than hysteretic (25.53%). The ecosystem of Lake Chaohu shifted from the clear to turbid state during late 1970s. For managers, approximately two-thirds of the current TP loading must be reduced for a shift back with substantial improvement in water quality. Because in practice the reduction of loading from a non-point source is very difficult and costly, additional methods beyond nutrient reduction, such as water level regulation, should be considered for the lake restoration

Multi-Media Exposure to Polycyclic Aromatic Hydrocarbons at Lake Chaohu, the Fifth Largest Fresh Water Lake in China: Residual Levels, Sources and Carcinogenic Risk

The residual levels of 16 priority polycyclic aromatic hydrocarbons (PAHs) in environment media and freshwater fish were collected and measured from Lake Chaohu by using Gas chromatography-mass spectrometry. Potential atmospheric sources were identified by molecular diagnostic ratios and the positive matrix factorization (PMF) method. PAH exposure doses through inhalation, intake of water and freshwater fish ingestion were estimated by the assessment model recommended by US EPA. The carcinogenic risks of PAH exposure were evaluated by probabilistic risk assessment and Monte Carlo simulation. The following results were obtained: (1) The PAH16 levels in gaseous, particulate phase, water and fish muscles were 59.4 ng·m−3, 14.2 ng·m−3, 170 ng·L−1 and 114 ng·g−1, respectively. No significant urban-rural difference was found between two sampling sites except gaseous BaPeq. The relationship between gaseous PAHs and PAH in water was detected by the application of Spearman correlation analysis. (2) Three potential sources were identified by the PMF model. The sources from biomass combustions, coal combustion and vehicle emission accounted for 43.6%, 30.6% and 25.8% of the total PAHs, respectively. (3) Fish intake has the highest lifetime average daily dose (LADD) of 3.01 × 10−6 mg·kg−1·d−1, followed by the particle inhalation with LADD of 2.94 × 10−6 mg·kg−1·d−1. (4) As a result of probabilistic cancer risk assessment, the median ILCRs were 3.1 × 10−5 to 3.3 × 10−5 in urban and rural residents, which were lower than the suggested serious level but higher than the acceptable level. In summary, the result suggests that potential carcinogenic risk exists among residents around Lake Chaohu. Fish ingestion and inhalation are two major PAH exposure pathways

Optimized Multiresidue Analysis of Organic Contaminants of Priority Concern in a Daily Consumed Fish (Grass Carp)

The organic contaminants, including polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs), polybrominated diphenyl ethers (PBDEs), and polychlorinated biphenyls (PCBs), are of priority concern because of their persistence, toxicity, and long-distance transportation in global environment. Their residues in a daily consumed fish (grass carp) pose potential threat to human health and aquatic ecosystems. The present study optimized an analytical protocol of microwave-assisted extraction (MAE), lip-removal by gel permeation chromatography (GPC), cleanup by solid phase cartridge (SC) or adsorption chromatography column (CC), and gas chromatography-mass spectrometry (GC/MS). Besides traditional statistical parameters, some indicators were calculated to judge the performances of extraction by various methods. The optimization experiment showed that n-hexane/acetone was the best MEA extraction solvent; an optimal fraction time of 10–39 min could simultaneously elute all the target chemicals in a single GPC run. Both CC and SC showed good recoveries. However, CC performed better than SC (p<0.05) for OCPs, and SC performed better than CC for PBDEs (p<0.05). We also emphasized the limitations and advantages of SC and CC and finally proposed SC as the promising cleanup method because of its low-cost materials, time-saving steps, being free of manual filling, and operation by automated SPE system

Changes in food web structure and ecosystem functioning of a large, shallow Chinese lake during the 1950s, 1980s and 2000s

Food web structure dynamics and ecosystem functioning are strongly linked, and both are indispensable in evaluating ecosystem development in lakes under multiple anthropogenic stressors. However, model-based approaches concerning the changes in food web structure and ecosystem functioning in a certain lake during distinct periods are scarce. In this study, we focus on Lake Chaohu, the fifth-largest lake in China, which has undergone drastic changes over the last several decades. Data from the 1950s, 1980s and 2000s were used to create three Ecopath mass-balance models. These Ecopath models were validated by the stable isotope-determined trophic level (TL) for each functional group, which indicated an acceptable model performance. Over time, we observed a collapse of the food web toward a simplified structure and decreasing biodiversity and trophic interactions. The lake ecosystem was approaching an immature but stable status from the 1950s to the 2000s, as indicated by the multiple related indicators and the distribution of energy flows in slow detrital-based and fast primary producer-based channels. We further discuss the potential driving factors and underlying mechanisms, hypothesizing that hydrological regulation may play a significant role in driving all of these changes in Lake Chaohu in addition to eutrophication and intensive fishery. Overall, we strongly advocate the identification of a threshold in abundance of zooplanktivorous fish, an integrated strategy for future ecological restoration in Lake Chaohu, and the consideration of using Ecopath as a new management tool for other lakes, thereby bridging the strategies from both environmental and ecological perspectives.</p

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