Insight into the interaction of tetrabromobisphenol A with sediment-derived dissolved organic carbon in a multiphase system by direct immersion solid phase microextraction

Tetrabromobisphenol A (TBBPA), a ubiquitously used commercial brominated flame retardant (BFR), has been widely detected in aquatic environments, and has aroused much attention due to its potential adverse effects on aquatic organisms. However, current research on the environmental fate and transport of TBBPA in the sediment-dissolved organic carbon (DOC)-water polyphase system is lacking. In this study, the sorption behavior of TBBPA in a water-DOC-sediment system was investigated using the direct-immersion solid-phase microextraction (DI-SPME) method, and the free dissolved concentration (Cw-SPME) and DOC adsorption concentration (CDOC) of TBBPA in water were measured by applying this DI-SPME approach. In addition, the effects of pH, ionic strength, and soluble organic concentration on the adsorption of TBBPA in the multiphase system were evaluated. The adsorption kinetics experimental results show that the adsorption behavior of TBBPA on sediments conforms to a linear model, suggesting that it could be mainly absorbed by sediments. The solid-water partition coefficient (Kd) of TBBPA was artificially reduced 1.54 times using the traditional liquid-liquid extraction method because the sorption behavior of the DOC was ignored, which could be accurately corrected using the DI-SPME method. The logKd and logKOC of TBBPA in the multiphase system were 4.12 ± 0.25 and 6.48 ± 0.25, respectively. Finally, the interference experiment revealed that the sorption behavior of TBBPA was affected by the pH, ionic strength (calcium ion), and humic acid concentration, apart from the lead ion concentration itself.

Sediment core records and impact factors of polycyclic aromatic hydrocarbons in Chinese lakes

Lake sediment is a natural sink for polycyclic aromatic hydrocarbons (PAHs). PAH sedimentation characteristics and their impact factors of Chinese lakes have mainly been qualitative assessed. However, quantitative impacts of PAH sedimentation from different factors have not been well analyzed. To fill this gap, we screened PAH sedimentation records from the literature, for 51 lakes in China and other regions of the world, to identify historical concentration variation and the impact factors of PAHs in different regions, in lake sediment. The results show that PAH concentrations in the sediment core in the selected Chinese lakes (478 ± 812 ng/g dry weight (dw)) were significantly lower than those in North America (5518 ± 6572 ng/g dw) and Europe (3817 ± 4033 ng/g dw). From 1900 to 2015, most of the lakes in China showed an increasing trend of PAH sedimentation concentrations, with the lakes in Southeastern China showed a decreasing trend of PAH concentration in the period of 2001-2015, which was later than the peak times shown in Western countries (1941-1970). The 2-3-ring PAHs were the main components in the sediment core of Chinese lakes, but the proportion to the total PAHs decreased from 72% in 1900-1940 to 55% in 2001-2015. Generalized additive modeling (GAM) was adopted to simulate the associations between PAH sedimentation records and the impact factors. There are large regional variations of economic and industrial development in China. The impact factors of PAH accumulation in the lake sediments differ in different regions. However, population and the consumption of coal, pesticides, and fertilizer were identified to be the most important impact factors influencing PAH sedimentation. The Chinese government needs to strengthen control measures on pollutant discharge to reduce the anthropogenic impact of PAH sedimentation in lakes.

Polycyclic aromatic hydrocarbons (PAHs) in a sediment core from Lake Taihu and their associations with sedimentary organic matter

Sediment core is the recorder of polycyclic aromatic hydrocarbon (PAH) pollutions and the associated sedimentary organic matter (SOM), acting as crucial supports for pollution control and environmental management. Here, the sedimentary records of PAHs and SOM in the past century in Lake Taihu, China, were reconstructed from a 50-cm sediment core. On the one hand, the presence of PAHs ranged from 8.99 to 199.2 ng/g. Vertically, PAHs declined with the depth increased, and the sedimentation history of PAHs was divided into two stages with a discontinuity at 20 cm depth. In composition, PAHs in the sediment core were dominated by three-ring PAHs (44.6% ± 9.1%, mean ± standard deviation), and were followed by four-ring (27.0% ± 3.3%), and five-ring (12.1% ± 4.0%) PAHs. In toxicity assessment, the sedimentary records of benzo[a]pyrene-based toxic equivalency were well described by an exponential model with R-square of 0.95, and the environmental background toxic value was identified as 1.62 ng/g. On the other hand, different components of SOM were successfully identified by n-alkane markers (p < 0.01) and the variations of SOM were well explained (84.6%). A discontinuity of SOM was recognized at 22 cm depth. Association study showed that the sedimentary PAHs were associated with both anthropogenic and biogenic SOM (p < 0.05) with explained variances for most individual PAHs of 60%. It indicated the vertical distributions of PAHs were driven by sedimentary SOM. Therefore, environmental processes such as biogenic factors should attract more attentions as well as PAH emissions to reduce the impacts of PAHs.

Polycyclic aromatic hydrocarbons (PAHs) in the upstream rivers of Taihu Lake Basin, China: spatial distribution, sources and environmental risk

The polycyclic aromatic hydrocarbon (PAH) pollution in Taihu Lake Basin has caused widespread concern. However, the spatial temporal distribution of PAHs in the upstream rivers of Taihu Lake Basin remains largely unknown. Thus, this study aims to investigate the level, spatial distribution, sources, and environment risk caused by PAHs in upstream rivers of Taihu Lake Basin. The concentrations of total 16 PAHs (∑16PAHs) ranged from 188.64 to 1060.39 ng/g, with an average of 472.62 ng/g. High-molecular-weight (HMW) PAHs were the predominant compounds in most sample sites. The results of source analysis demonstrated that the PAH pollution was mainly sourced from mixture of combustion and direct petroleum spillage. The ecological risk assessment showed that moderate ecological risk caused by the PAH contaminants might occur in most sample sites. The incremental lifetime cancer risks (ILCRs) ranged from 2.07 ×10-4 - 2.66 × 10-3 for children and 9.66 ×10-5 - 1.24 × 10-3 for adult, indicating moderate cancer risk of PAH-contaminated sediments.

Effects of organic matter on polycyclic aromatic hydrocarbons in riverine sediments affected by human activities

Organic matter (OM) is an important component of riverine environments and a major factor in the migration and transformation of hydrophobic organic substances, such as polycyclic aromatic hydrocarbons (PAHs), to sediments. We studied the distributions, sources, and correlations between PAHs and OM in sediments from the Duliujian and the Beiyun rivers in North China. Sixteen PAHs were detected in the surface sediments at total concentrations ranging from 356 to 4652 ng·g^-1 dry weight, which caused a moderate to high level of pollution. The PAH distributions were significantly and positively correlated with OM (p < 0.01) and higher concentrations were detected downstream of areas affected by human activity. Petroleum, coal, and wood combustion were the main sources of PAHs in riverine sediments, and the sources of OM in sediment included terrestrial and aquatic higher plants, soil, and sewage discharge. The OM accumulated and aged along the river, with increases in the degree of aromaticity and condensation, which led to stronger adsorption of PAHs. Our results will help to promote the management and restoration of contaminated riverine sediments.

Spatial occurrence and sources of PAHs in sediments drive the ecological and health risk of Taihu Lake in China

To study the spatial occurrence, sources, and ecological risks of 16 PAHs, surface sediments had been collected from seven major areas of Taihu Lake, China in April 2021. Results showed that the concentrations of ∑₁₆PAHs varied between 1381.48 and 4682.16 ng g⁻¹, and the contents of BghiP in each sample were the highest. The PAHs concentrations in the sediments near the lakeshore were much higher than those in the central area of the lake. The sedimentary ∑₁₆PAHs were mainly composed of molecular-weight monomers and 4-ring PAHs showed superiority (35.69–45.02%). According to the ratio of PAH monomer, the sedimentary PAHs in Taihu Lake were dominantly derived from the combustion. Through the biological toxicity assessment and the BaP equivalent (BaPE), great biological risks of PAHs monomers i.e. DahA and IcdP were found. Both concentrations of ∑₁₆PAHs and dominant 4–6-ring monomers accompanied by carcinogenic risks in many areas of Taihu Lake increased. It is necessary to strengthen monitoring and take measures to control the input of organic pollutants.

Spatial Distributions, Sources and Risks of Polycyclic Aromatic Hydrocarbons in Sediments from Ziya River System, Northern China

With the development of urbanization and industrialization, Ziya River Plain (ZYRP) had become one of the most polluted regions of polycyclic aromatic hydrocarbons (PAHs) in north China. The distribution of PAHs in sediments were investigated, and then their sources and risks were evaluated. The results showed that the total PAHs varied from 3372 to 92,948 μg/kg, and heavy pollution was found in the upstream. Both the isomer pair ratios of PAH and principal components analysis (PCA) revealed that fossil fuel combustion was the mainly contributes (69.1%), followed by wood and coal combustion (26.7%). The ecological risk for the whole area was moderate, with the highest risk in Niuwei River (NWR). and significant correlation was found between the ecological risk and high-molecular-weight (HMW) of PAHs (r² > 0.99, p < 0.01). Our findings would give insights into the mitigation of sedimentary PAHs pollution in north China.

Occurrences, Retention and Risk Assessments of PAHs in Beidagang Wetland in Tianjin, China

Coastal wetlands are the last barriers for pollutants from land to the sea. In this study, a coastal wetland that locates in the lower reach of Haihe River Systems was selected to speculate the removal and retention of polycyclic aromatic hydrocarbons (PAHs) by analyzing their spatial distributions and the changes of composition. The results showed that the overall removal efficiency of PAHs in water phase was 58.1%. There was an accumulation for sedimentary PAHs, reaching 431 ng/g (181 ng/g in the inlet). The compositions of sedimentary PAHs were also changed, high-molecular-weight PAHs were the main component (70-50%), with a steady decreasing trend and the influence of water flow direction. The risk assessment by mean effect range media quotients (M-ERM-Qs) depicted that there was in low ecological risk, due to the degradation of PAHs in the wetlands. Our results clearly demonstrated the coastal wetlands could effectively retain the PAHs, thus we recommend an active protection strategy for the coast wetlands in Tianjin in the future.

Evaluating the effect of dam construction on the phosphorus fractions in sediments in a reservoir of drinking water source, China

It is widely acknowledged that dams affect sediment transport and water quality. To support water management of reservoirs, it is useful to explore how the fractions of phosphorus (P) in sediments were changed after the dam was built. The aim of this study was to assess the spatial and temporal trends of the P fractions in sediments from the Miyun Reservoir, a pivotal drinking water supply for Beijing City, the capital of China. Nine surface sediment samples, together with a sediment core, were collected. The concentrations of total P (TP) and their fractions were then determined by using a sequential extraction method. The results showed that the reservoir was classified into three areas spatially based on the TP concentrations, i.e., high (Baihe area), medium (transitional area), and low (Chaohe area) concentrations. The concentrations of iron-bound P (BD-P) and metal oxide-bound P (NaOH-P) were higher in the Baihe and Chaohe regions than those in the transitional area and tended to increase with water depth. Dam construction can lead to the concentrations of P increased in sediments and further increase the potential of internal P loadings. This study revealed the effect of dam construction on sedimentary P accumulation. The results will be helpful in better understanding the mobility and bioavailability of P in the aquatic ecosystem, which aim to achieve a more highly targeted environmental management for this important region.

Historical variation of black carbon and PAHs over the last ~200 years in central North China: Evidence from lake sediment records

As the largest coal-producing province in China, the coal production of Shanxi Province accounts for one third of the country's total. Thus it is of great importance to study the pollution history of typical pollutants in Shanxi Province and their links with energy usage in North China. Sediment cores from two relatively remote lakes in central North China were retrieved to investigate historical evolutions of black carbon (BC) and polycyclic aromatic hydrocarbons (PAHs) in the last ~200 years. The two records show several-fold increases in both concentrations and depositional fluxes of BC, char, soot, and PAHs in recent five decades, which were associated with the influence of anthropogenic activities resulting from socio-economic development in Shanxi Province. However, after ~2000 their fluxes decreased sharply due to China's effort on environmental protection. These changes indicate that atmospheric BC and PAHs loads in the region were affected significantly by recent anthropogenic activities and environmental policies. Ratios of individual PAHs and char/soot indicate pyrogenic sources of these increased pollutants in recent decades, with coking industry and coal combustion as the two major sources. Significant positive correlations between BC and PAHs were observed in both cores of Lake Gonghai and Lake Mayinghai, indicating that they were likely co-transported by BC particles from similar sources. This study provides new and important understanding of the atmospheric pollution history of BC and PAHs in North China.

Pollution and Risk of PAHs in Surface Sediments from the Tributaries and Their Relation to Anthropogenic Activities, in the Main Urban Districts of Chongqing City, Southwest China

Concentrations, sources and risk of 16 priority polycyclic aromatic hydrocarbons (PAHs) were investigated in surface sediments from 19 representative tributaries in a regional scale of Chongqing City. The total concentration of 16 PAHs (ΣPAHs) ranged from 221 to 3205 ng g^-1 with a mean of 1055 ng g^-1. Most tributaries of the Jialing River exhibited significantly higher ΣPAHs concentrations (mean 1864 ng g^-1) compared to those flowing into the Yangtze River (mean 787 ng g^-1). Isomeric ratio and hierarchical clustering analysis showed combustion may impact sedimentary PAHs at most center sites of the City, while PAHs at most sites were mixed of petrogenic and pyrogenic sources. Toxicity equivalency concentration for carcinogenic PAH were 2-4 times more than the Dutch limit. More comprehensive assessment of safety is suggested to reduce environmental risk of PAHs in sediments.

Determination of influencing factors on historical concentration variations of PAHs in West Taihu Lake, China

The adsorption of polycyclic aromatic hydrocarbons (PAHs) by components such as elemental carbon (EC), total organic carbon (TOC), and particles is different, and EC and PAHs are good materials for reconstructing historical human activity patterns and pollution conditions. In this study, the effects of EC (soot and char), TOC and particles of different grain size on PAHs in surface sediments were quantitatively analysed, and their historical concentrations in a sediment core from western Taihu Lake were reconstructed. The contents of soot, TOC, clay, EC and char explained 57.2%, 27.6%, 26.0%, 24.0% and 16.4%, respectively, of the PAH concentrations in surface sediments. The correlation between the soot and PAH levels was significantly higher than that between the char, TOC, and clay contents and PAH levels, and PAHs were mainly affected by the local economic development and human activity, as indicated by metrics of population, highway mileage, coal burning, and industrial output. With the development of the economy of the Taihu Lake Basin, the composition of PAHs in the sediments has changed: the proportion of low-molecular-weight PAHs decreased from 42.4% to 17.5%, and that of high-molecular-weight PAHs increased from 58.7% to 82.5%. The concentration of PAHs in pore water from Taihu Lake over the past 100 years was reconstructed and ranged from 43.1 to 961.2 μg L^-1, with an average of 180.7 μg L^-1. After China's reform and opening up, the concentrations of various PAHs in Taihu Lake changed from safe to chronic pollution levels. The ratios of lead (Pb) isotopes and the diagnostic ratios of PAHs showed that the main sources of PAHs in western Taihu Lake sediments were human activities such as coal and petroleum combustion.

Sedimentary archive of Polycyclic Aromatic Hydrocarbons and perylene sources in the northern part of Taihu Lake, China

In the present work, we analyzed the concentration patterns of 20 Polycyclic Aromatic Hydrocarbons (PAHs) in 25 surface sediments and 11 sediment cores from the northern part of Taihu Lake, China. Three of the cores were dated based on ¹³⁷Cs activity for the deposition age of the sediment. The spatial distributions of the PAH concentrations show that the inflow rivers into Zhushan Bay and Meiliang Bay were the main pathway for PAHs and sediment input to the northern part of the lake. This results in substantially higher PAH concentrations (up to 5000 ng/g) and sedimentation rates (higher than the average of 3-4 mm/a) in the area close to the river outlets. In addition, results also show that PAH concentrations in the sediments considerably increased from the early 1960s, but the decreasing concentrations in the upper layers of the sediment could be attributed to the introduction of measures on environmental improvement from ca. 2000. There were both anthropogenic and biogenic origins of perylene in the lake sediments, which were distinguished based on spatial distribution patterns and also the concentration proportions of perylene to the sum of the 20 PAHs. In the cores collected close to river outlets, the concentration proportions of perylene typically range from 0.02 to 0.18 and there are significant positive linear correlations between the concentration of perylene and three anthropogenic PAHs (Benzo[a]pyrene, Benzo[e]pyrene, Pyrene), suggesting that perylene was dominated by anthropogenic input. However, the cores collected further away from the river outlets show the concentration proportions between 0.13 and 0.96, and present significant negative correlations or no correlations between perylene and the three PAHs, suggesting that perylene was mainly formed by biogenic activities. Furthermore, the different perylene sources accompanied with the location distributions imply that anthropogenic activities could inhibit its biogenic formation.

Anthropogenic PAHs in lake sediments: a literature review (2002-2018)

Lake sediments are an important reservoir for toxic and hydrophobic polycyclic aromatic hydrocarbons (PAHs). Monitoring of PAHs in sediment is helpful to understand pollution mechanisms and anthropogenic activities. This study reviews studies of PAHs in lake sediments published during 2002-2018. The studies' findings are analyzed, distributions of PAHs in lake sediments are summarized, and the applicability of lake sediments for tracking changes in PAH emission sources is emphasized. Lake sediments heavily polluted with PAHs are distributed in China, Egypt, the USA, and some urban lakes in Africa. The high levels of PAHs are predominantly associated with human activities such as anthropogenic combustion, petroleum industries, road traffic, and socioeconomic factors. However, the concentrations of sedimentary PAHs in most lakes were below the international guideline values.

Influence of Industrialization and Environmental Protection on Environmental Pollution: A Case Study of Taihu Lake, China

In order to quantitatively study the effect of environmental protection in China since the twenty-first century and the environmental pollution projected for the next ten years (under the model of extensive economic development), this paper establishes a Bayesian regulation back propagation neural network (BRBPNN) to analyze the typical pollutants (i.e., cadmium (Cd) and benzopyrene (BaP)) for Taihu Lake, a typical Chinese freshwater lake. For the periods 1950–2003 and 1950–2015, the neural network model estimated the BaP concentration for the database with Nash-Sutcliffe model efficiency (NS) = 0.99 and 0.99 and root-mean-square error (RMSE) = 3.1 and 9.3 for the total database and the Cd concentration for the database with NS = 0.93 and 0.98 and RMSE = 45.4 and 65.7 for the total database, respectively. In the model of extensive economic development, the concentration of pollutants in the sediments of Taihu reached the maximum value at the end of the twentieth century and early twenty-first century, and there was an inflection point. After the early twenty-first century, the concentration of pollutants was controlled under various environmental policies and measures. In 2015, the environmental protection ratio of Cd and BaP reached 52% and 89%, respectively. Without environmental protection measures, the concentrations of Cd and BaP obtained from the neural network model is projected to reach 2015.5 μg kg⁻¹ and 407.8 ng g⁻¹, respectively, in 2030. Based on the results of this study, the Chinese government will need to invest more money and energy to clean up the environment.