Abundances, depositional fluxes, and homologue patterns of polychlorinated biphenyls in dated sediment cores from the Pearl River Delta, China

Centurial deposition records of polychlorinated biphenyls and organochlorine pesticides in sediment cores from a plateau deep-water lake of China: Significance of anthropogenic impacts, transformation signals and ecological risks revealed by full congener analysis

Lake Fuxian, the largest deep freshwater lake in China, has been suffering from increasing ecological and environmental issues along with the rapid urbanization and industrialization in the past 40 years. To better understand the historical pollution of persistent organic pollutants (POPs) in Lake Fuxian, comprehensive analyses of 209 polychlorinated biphenyl (PCB) congeners and 20 organochlorine pesticides (OCPs) were conducted in two intact sediment cores (Core V1 and Core V2). The total mass concentrations of PCBs ranged from 7.60 to 31.47 ng/g (dry weight basis) and 5.55 to 28.90 ng/g during the period of 1908-2019 in Core V1 and 1924-2019 in Core V2, respectively. PCBs exhibited a consecutive increasing trend from 1940s to 2019 in Core V1. The temporal trend of PCBs in Core V2 basically matched to the history of PCB usage and prohibition in China (increasing from 1940s to mid-1960s, a remarkable drop in mid-1970s, and then increasing until 2019). Moreover, low-chlorinated PCBs were dominant among PCB homologues. Mono-CBs, di-CBs, tri-CBs and tetra-CBs accounted for 86.71 %-98.57 % in sediment segments. The PCB sources included unintentional emission and atmospheric deposition, as well as biological transformation. The total mass concentrations of OCPs ranged from 0.74 to 3.82 ng/g in Core V1 and 0.35 to 2.23 ng/g in Core V2, respectively. Similar trend was observed in the two sediment cores with peaks in the early 1990s. The predominant OCPs were γ-hexachlorohexane (γ-HCHs), dieldrin and p,p'-DDD. The ecological risks posed by PCBs and p-p'-DDD in Lake Fuxian were relatively low. In contrast, dieldrin might pose a potential threat to exposed organisms and apparently adverse ecological effects were caused by γ-HCH. This study will provide important baseline information on historical POPs contamination of Lake Fuxian.

Unexpectedly high levels and health risks of atmospheric polychlorinated biphenyls in modern mechanical dismantling of obsolete electrical equipment: Investigations in a large integrated e-waste dismantling industrial estate

Large industrial estates for electrical and electronic waste (e-waste) mechanical dismantling and recycling are gradually replacing outmoded small factories and intensive domestic workshops for e-waste manual and chemical dismantling. However, the air pollution and health risks of persistent organic pollutants during the modern mechanical processing of e-waste, especially obsolete electrical equipment, still remain unclear. Here, unexpectedly high levels (409.3 ng/m3) and health risks of airborne polychlorinated biphenyls (PCBs) were found during the mechanical processing of obsolete electric equipment or parts in a large integrated dismantling industrial estate, which is comparable to or a dozen times higher than those reported during chemical processing. In contrast, the levels (936.0 pg/m3) and health risks of particulate polybrominated diphenyl ethers (PBDEs) were all lower than those of previous studies. PCB emissions (44.9-3300.5 ng/m3) varied significantly across six mechanical dismantling places specifically treating waste motors, electrical appliances, hardware, transformers, and metals, respectively. The high PCB content and mass processing number of obsolete electrical equipment probably result in the highest PCB emissions from the mechanical dismantling of obsolete motors, followed by waste electrical appliances and metals. The PCB non-cancer and cancer risks associated with inhalation and dermal exposure in different mechanical dismantling places were all above the given potential risk limits. In particular, the health risks of dismantling obsolete motor exceeded the definite risk levels. Little difference in PCB emissions and health risks between working and non-working time suggested the importance of PCB volatilization from most e-waste. Such high PCB emissions and health risks of PCBs undoubtedly posed a severe threat to frontline workers, but fortunately, they decreased significantly with the increasing distance from the industrial estate. We highlight that PCB emissions and associated health risks from obsolete electrical equipment with high PCB content during mechanical dismantling activities should be of great concern.

Distribution characteristics of photoinitiators and their flux estimation from the Pearl River Delta to the coastal waters of the South China Sea

Photoinitiators (PIs) are widely used in industrial polymerization processes. It has been reported that PIs are ubiquitous in indoor environments and that humans are exposed to PIs, but the occurrence of PIs in natural environments are rarely known. In the present study, 25 PIs, including 9 benzophenones (BZPs), 8 amine co-initiators (ACIs), 4 thioxanthones (TXs) and 4 phosphine oxides (POs), were analyzed in water and sediment samples collected from eight riverine outlets of the Pearl River Delta (PRD). Eighteen, 14, and 14 of the 25 target PIs were detected in water, suspended particulate matter (SPM) and sediment samples, respectively. The total concentrations of PIs in water, SPM, and sediment were in the ranges of 2.88‒96.1 ng/L, 9.25‒923 ng/g dry weight (dw), and 3.79‒56.9 ng/g dw, with geometric mean concentration (GM) of 10.8 ng/L, 48.6 ng/g dw, and 17.1 ng/g dw, respectively. A significant linear regression was observed between the log partitioning coefficients (K_d) values of PIs and their log octanol water partition coefficient (K_ow) values (R² = 0.535, p < 0.05). The annual riverine input of PIs to the coastal waters of the South China Sea via eight main outlets of the PRD was estimated to be 4.12 × 10³ kg/year, and the ∑BZPs, ∑ACIs, ∑TXs and ∑POs contributed to 1.96 × 10³, 1.24 × 10³, 89.6 and 830 kg/year, respectively. This is the first report of a systematic description of the occurrence characteristics of PIs exposure in water, SPM, and sediment. The environmental fate and risks of PIs in aquatic environments need further investigations.

Comprehensive understanding of electrochemical treatment systems combined with biological processes for wastewater remediation

The presence of toxic pollutants in wastewater discharge can affect the environment negatively due to presence of the organic and inorganic contaminants. The application of the electrochemical process in wastewater treatment is promising, specifically in treating these harmful pollutants from the aquatic environment. This review focused on recent applications of the electrochemical process for the remediation of such harmful pollutants from aquatic environments. Furthermore, the process conditions that affect the electrochemical process performance are evaluated, and the appropriate treatment processes are suggested according to the presence of organic and inorganic contaminants. Electrocoagulation, electrooxidation, and electro-Fenton applications in wastewater have shown effective performance with high removal rates. The disadvantages of these processes are the formation of toxic intermediate metabolites, high energy consumption, and sludge generation. To overcome such disadvantages combined ecotechnologies can be applied in large-scale wastewater pollutants removal. The combination of electrochemical and biological treatment has gained importance, increased removal performance remarkably, and decreased operational costs. The critical discussion with depth information in this review could be beneficial for wastewater treatment plant operators throughout the world.

Chronology of PAH and PCB pollution using sediment core in the Golden Horn estuary (Sea of Marmara)

The sources and depositional history of 16 polycyclic aromatic hydrocarbons (PAHs) and 18 polychlorinated biphenyl (PCBs) congeners in the Golden Horn estuary (İstanbul) were investigated using a dated sediment core for the period between 1880 and 2012. The concentrations of PAHs and PCBs were calculated for every 4 cm slices of the sediment core and ranged from 1203.5 to 3441.4 ng/g and 5.4 to 41.4 ng/g, respectively. The diagnostic ratios indicated that the maximum PAH values correspondence to combustion after a crude oil-carrying Romanian tanker (Independenta) accident in the İstanbul Strait in 1979. The historical deposition of PAHs and PCBs in the Golden Horn was influenced by municipal effluent and heavy industrial dischargers approximately 50 years. When the Silahtarağa thermal power plant (TPP) was operating, PCB pollution rose; however, after a thorough rehabilitation effort and the outlawing of PCB use in the 1990s, pollution levels significantly tended to decrease.

Deposition records of persistent organic pollutants and black carbon in dated sediment cores from China marginal seas: Implications for terrestrial sources and transport processes

Black carbon (BC) and persistent organic pollutants (POPs) were analyzed from three sediment cores collected offshore in the East China Marginal Seas. The results showed steadily increasing or stable BC concentrations and fluxes. By contrast, time trends of POPs fluxes were consistent with historical records of commercial production and use in China. Although the POP inventories decreased significantly with increase in offshore distance, the relatively consistent trends for individual POPs in different sea areas confirmed that the main sources are derived from mainland China and that atmospheric input was an important contribution. POPs inventories decreased by 59-91 % during transport from the Yellow Sea to the remote East China Sea and deposition to the sediment. This suggests that the source signal for POPs may be preserved under stable depositional environments, even though only a fraction of those pollutants are buried in open sea sediments.

Low levels of persistent organic pollutants in sediments of the Doce River mouth, South Atlantic, before the Fundão dam failure

The Doce River mouth (DRM) was severely impacted by the rupture of the Fundão Dam in 2015, considered the greatest Brazilian environmental tragedy in terms of tailings volume released (>40 million m³) and traveled distance (~600 km until the Atlantic Ocean). Environmental monitoring has been performed since then, but background levels are scarce or absent to Persistent Organic Pollutants (POPs), making impact assessments difficult. In the current study, we presented the baseline levels, inventories, and risk assessment of the POPs polychlorinated biphenyl (PCBs) and organochlorinated pesticides (OCPs), in surface sediment of the DRM. Samples were collected in December 2010 and July 2011, i.e., four years before the Fundão dam failure. The total PCBs and the OCPs (Aldrin, HCHs, and Chlordanes) were detected in both sampling campaigns, with levels up to 9.50 and 1.64, 0.28, and 0.63 ng g^-1, respectively. The decrease of the Doce River flow was the main factor contributing to seasonal variations in the spatial distribution, and to a slight decline in the levels and frequency of the analyzed POPs in sediments collected in the dry season (July 2011). Environmental risk assessment, inventories, and total mass results suggest a low potential of PCBs and OCPs accumulation before the dam failure. This is the first POPs assessment in the study area that helped identify some unexpected impacts of the Fundão dam failure and contributed to the understanding of POPs cycles in the Southern Atlantic, data that are still scarce in the region.

Are chlorine isotopologues of polychlorinated organic pollutants binomially distributed? Theoretical evaluation, numerical simulation, experimental evidences and implications for chlorine isotope analysis and source identification

Relative abundances of chlorine isotopologues of polychlorinated organic compounds (POCs) are commonly recognized to comply with binomial distribution. This study investigated whether chlorine isotopologue distributions of polychlorinated organic pollutants are binomial and evaluated implications of the distributions to relevant analytical and environmental research by theoretical derivation, numerical simulation and experiment. Chlorine kinetic isotope effects and equilibrium isotope effects vary in stepwise chlorination reactions, leading to inconsistent chlorine isotope ratios on different reaction positions of products, which results in non-binomial chlorine isotopologue distributions of the products. After physical changes and dechlorination, chlorine isotopologues of POCs are unlikely binomially distributed. The experimental results demonstrated that the chlorine isotopologue distributions of perchloroethylene, trichloroethylene, methyl-triclosan, and 2,3,7,8-tetrachlorodibenzofuran in standards and four polychlorinated biphenyls in both standard solutions and sediments were non-binomial. The patterns of chlorine isotope ratios derived from pairs of neighboring chlorine isotopologues of POCs from different sources were different, implying different isotopologue distributions, which might cause biases in compound-specific isotope analysis of chlorine (CSIA-Cl) and source identification. A complete-isotopologue scheme for isotope ratio calculation is recommended to CSIA-Cl for obtaining accurate data. Gas chromatography-double focusing magnetic-sector high resolution mass spectrometry is a promising instrument for CSIA-Cl that uses the complete-isotopologue scheme due to its excellent sensitivity, selectivity and ruggedness. This study yields new insights into chlorine isotopologue distributions of polychlorinated organic pollutants and proposes practicable solutions to improve CSIA-Cl that uses gas chromatography-mass spectrometry and facilitate source identification of polychlorinated organic pollutants.

Microbial sulfur metabolism and environmental implications

Sulfur as a macroelement plays an important role in biochemistry in both natural environments and engineering biosystems, which can be further linked to other important element cycles, e.g. carbon, nitrogen and iron. Consequently, the sulfur cycling primarily mediated by sulfur compounds oxidizing microorganisms and sulfur compounds reducing microorganisms has enormous environmental implications, particularly in wastewater treatment and pollution bioremediation. In this review, to connect the knowledge in microbial sulfur metabolism to environmental applications, we first comprehensively review recent advances in understanding microbial sulfur metabolisms at molecular-, cellular- and ecosystem-levels, together with their energetics. We then discuss the environmental implications to fight against soil and water pollution, with four foci: (1) acid mine drainage, (2) water blackening and odorization in urban rivers, (3) SANI® and DS-EBPR processes for sewage treatment, and (4) bioremediation of persistent organic pollutants. In addition, major challenges and further developments toward elucidation of microbial sulfur metabolisms and their environmental applications are identified and discussed.

Characterization of Compound-Specific Chlorine Isotopologue Distributions of Polychlorinated Organic Compounds by GC-HRMS for Source Identification

Distributions of chlorine isotopologues are potentially a fingerprint feature of organochlorines. However, the exact distributions remain little known. This study measured compound-specific chlorine isotopologue distributions of six polychlorinated organic compounds (POCs) for source identification. Complete chlorine isotopologues of POCs were detected by gas chromatography coupled to high-resolution mass spectrometry. The measured relative abundances (A_meas), theoretical relative abundances (A_theo), and relative variations between A_meas and A_theo (ΔA) of chlorine isotopologues were determined. These ΔA values were applied to characterize differences in isotopologue distribution patterns, and the ΔA patterns directly illustrated the distribution characteristics. Perchloroethylene (PCE) and trichloroethylene (TCE) from two manufacturers were chosen as model analytes to develop and validate the analytical method, including precision, concentration dependency, and temporal drift. The ΔA values of isotopologues of the PCE and TCE chemicals were from -82.5 to 19.9‰ with standard deviations (SDs) of 0.3-16.9‰. In addition, the ΔA values of the first three isotopologues (with 0-2 ³⁷Cl atoms) were from -15.5 to 19.9‰ with SDs of 0.3-1.6‰, showing sufficient precisions. No concentration dependency and temporal drift of ΔA were observed. The method has been successfully applied to source identification for PCE and TCE in commercial chemicals and plastic materials, and four polychlorinated biphenyls in chemicals and sediments, demonstrating that the ΔA values and ΔA patterns were discernable for POCs from different sources. This study demonstrates that compound-specific chlorine isotopologue distributions of POCs are differentiable and measurable, proposing a novel approach to perform fingerprinting analysis for the distributions, which is anticipated to facilitate source identification for organochlorine pollutants.

Sedimentary evolution of PAHs, POPs and ECs: Historical sedimentary deposition and evolution of persistent and emerging organic pollutants in sediments in a typical karstic river basin

Knowledge on the occurrence and distributions of organic compounds, especially PAHs, POPs and ECs, in karstic river basins is limited. This study aims to determine the depositional history and sources of PAHs, PCBs, OCPs, antibiotics, EDCs and phenolic compounds and the ecological risk they have in the Panyang River Basin, an area with a typical karstic landscape and a high-longevity population. Sediment core analysis was adopted, correlation and principal component analyses were conducted to analyze pollution sources, and lead isotope technology was implemented for dating analysis. The sediment core covered 108 years. PCBs were detected with concentrations ranging from 3.80 to 16.18 μg/kg in the core with two concentration peaks in 1950 and 2005 that were related to anthropogenic effects. Eight of the 20 targeted phenolic compounds were detected, with concentrations ranging from 0.42 to 1.10 mg/kg. All PAHs were detected in the cores, with concentrations from 12.91 to 37.80 μg/kg. They were mainly related to natural diagenetic processes and domestic and agricultural sources. The concentrations of different OCP compounds ranged from undetected to 213.43 μg/kg and were mainly related to agricultural activities and long-range transportation. These key findings can assist environmental planning and management in this river basin.

Mechanistic Aspects Regarding the Ultraviolet Degradation of Polychlorinated Biphenyls in Different Media: Insights from Carbon and Chlorine Isotope Fractionation

In this study, the carbon and chlorine isotope fractionation during ultraviolet-photolysis of polychlorinated biphenyls (PCBs, including PCB18, PCB77, PCB110, and PCB138) in n-hexane (Hex), methanol/water (MeOH/H₂O), and silica gel was first investigated to explore their mechanistic processes. We observed a significant variation in Λ_Cl-C (ε_Cl/ε_C) for the same PCBs in different photochemical systems, implying that PCB degradation processes in various photoreaction systems could differ. Although all substrates showed normal apparent carbon/chlorine kinetic isotope effects (C-/Cl-AKIE >1), the putative inverse C-AKIE of nondechlorinated pathways was suggested by ¹³C depletion of the average carbon isotope composition of PCB138 and corresponding dechlorinated products in MeOH/H₂O, which might originate from the magnetic isotope effect. Significant negative correlations were found between C-AKIE and relative disappearance quantum yields ("Φ") of ortho-dechlorinated substrates (PCB18, PCB110, and PCB138) in Hex and MeOH/H₂O. However, the C-AKIE and "Φ" of PCB77 (meta/para-dechlorinated congener) obviously deviated from the above correlations. Furthermore, significantly different product-related carbon isotope enrichment factors of PCB77 in Hex were found. These results demonstrated the existence of dechlorination position-specific and masking effects in carbon isotope fractionations.

Sources of polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethanes (DDTs) found in surface sediment from coastal areas of Beibu Gulf: A reflection on shipping activities and coastal industries

The presence of polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethanes (DDTs) was determined in the sediments of Beibu Gulf, a newly developing industry and port in South China, to evaluate whether the rapid development of coastal cities has accelerated the organic pollution in the region. The levels of PCBs and DDTs ranged from 1.17 to 8.00 ng g^-1 and ND (not detected) to 3.82 ng g^-1, respectively. The levels were higher in the east of Beibu Gulf than in the west, which influenced by the industrialisation and urbanisation in the east. Additionally, penta-PCBs were the dominant PCB congeners, which are related to shipping activities, and DDTs may have originated from the historical use of technical DDT. The levels of pp'-DDD and PCBs did not have the potential to cause ecological risks in Beibu Gulf; however, residues of DDTs were at relatively higher ecotoxicological levels, thereby having the potential to cause adverse biological effects.

Investigating the spatial distribution of polychlorinated biphenyls in sediment in the Pearl River Delta, South China

One hundred forty-three surface sediment (0-5 cm depth) samples were collected from locations representing industrialized areas, less-industrialized areas, and e-waste recycling areas in the Pearl River Delta (PRD). The spatial distribution of polychlorinated biphenyls (PCBs) and their potential adverse effects on aquatic organisms were investigated. The average PCB concentration in the less-industrialized areas (background) in the PRD was approximately 10 ng/g dry weight (dw), which was generally half that found in the industrialized areas (approximately 22 ng/g dw). Severe PCB contamination, with concentrations ranging from 1000 to 26500 ng/g dw, was found in pond sediments collected from e-waste recycling areas. It is very likely that such contamination would have had adverse effects on the aquatic biota there. PCBs in the e-waste recycling areas were dominated by penta- and hex-PCB congeners, which made them significantly different from those found in other regions, where tri- and tetra-PCB congeners were predominant. Higher abundances of less chlorinated congeners were seen in the less-industrialized areas compared to the industrialized areas. Differences in the transport abilities of different congeners, together with dechlorination of higher chlorinated congeners, is the most likely reasons for this.

Persistent organic pollutants (POPs) and personal care products (PCPs) in the surface sediments of a large tropical bay (Todos os Santos Bay, Brazil)

The occurrence and spatial distribution of persistent organic pollutants (POPs) and personal care products (PCPs) were investigated in surface sediments of Todos os Santos Bay. Samples were Soxhlet-extracted and analyzed by gas chromatography coupled with tandem mass spectrometry. Quantification limits (QL) ranged from 0.0025 ng g^-1 for POPs to 0.25 ng g^-1 for PCPs. Of the POPs studied, only PCBs and DDTs were detectable, with concentrations ranging from <QL to 4.66 ng g^-1, with increased concentrations near urban and industrial areas. PCPs ranged from <QL to 27.5 ng g^-1 and presented a homogeneous spatial distribution, probably related to the continuous inputs of these compounds from diffuse sources. Mean contaminant inventories ranged from 0.33 ± 0.23 ng cm^-2 for DDTs to 8.3 ± 8.4 ng cm^-2 for fragrances. To the best of our knowledge, this is the first study on the occurrence of UV filters in sediments from Brazilian coastal environments.

Spatial distribution, source identification, and risk assessment of organochlorines in wild tilapia from Guangxi, South China

Seventy-five wild tilapia samples from six rivers (ten sites) in Guangxi province were collected and analyzed for 53 organochlorine compounds. DDTs, endosulfan, and PCBs were the most dominant compounds found in this study. Tiandong County (TD) and Guigang City (GG) sites were found to be heavily contaminated with high levels of endosulfan (385-925 ng/g lw) and/or DDTs (20.1-422 ng/g lw). The diagnostic ratios indicated that the residues of DDTs and endosulfan in wild tilapia are associated with historical applications as well as the recent introduction of technical DDTs and endosulfan at some sampling sites. The correlation between total length, body mass, and organochlorines (OCs) was higher than the correlation between age and lipid content. There was no significant correlation between organochlorine pesticides (OCPs) and lipid content. Therefore, for organisms, the feeding intensity (related to length and mass) of fish could better reflect degree of pollution than exposure time (age) of fish. The hazardous ratios for the 50th and 95th percentile data of OCPs and PCBs in fish were both below 1, suggesting that daily exposure to OCPs and PCBs yields a lifetime cancer risk lower than 1 in 10,000.

Tracing the sources and microbial degradation of PCBs in field sediments by a multiple-line-of-evidence approach including compound-specific stable isotope analysis

Comprehensive monitoring is crucial for tracing micropollutants in the natural environment. To better evaluate the sources and natural attenuation of polychlorinated biphenyls (PCBs), three composite sediment cores were sampled from a closed pond near e-waste recycling plants, and a multiple-line-of-evidence approach (MLEA) including quantification, enantiomer analysis, microbial community profiling, and compound-specific isotope analysis (CSIA) was used to investigate the fate of PCBs in sediment cores. The difference in the maximum PCB concentrations and associated depths between sites 1/2 and 3 and the corresponding significant (p < 0.01) difference in δ¹³C values strongly indicated two different PCB inputs at sites 1/2 and 3. A significant (p < 0.01) negative correlation between the variation in chlorine per biphenyl (CPB) and Log the abundance of Dehalococcoides/total molar concentration of PCBs (Log Dhc/TPCB) along the cores suggested that different degrees of PCB degradation occurred and that Dehalococcoides likely participated in PCB degradation in these sediments. Nonracemic compositions and pronounced stable carbon isotope fractionation (Δδ¹³C > 1‰) of PCB congeners were observed, confirming that in situ degradation occurred in the sediment cores. The progressive enrichment in ¹³C with increasing core depth suggested strengthened microbial degradation of the residual congener pools. The results of this study suggested that MLEA analysis of PCBs can provide reliable information to better monitor the sources and fate of these compounds in the environment.

Assessment of persistent organic pollutants in surface sediments along Lebanese coastal zone

The levels of some persistent organic pollutants (POPs) along the Lebanese coastal zone (LCZ) were assessed by collecting15 surface sediments from five hotspot stations. Such stations were influenced by various industrial units, riverine input, and touristic activities. The levels of polycyclic aromatic hydrocarbons (∑16PAHs), their methylated derivatives (∑18Me-PAHs), and polychlorinated biphenyls (∑28PCBs) were in the range of 537-3773 μg∙kg^-1 dw, 187-1541 μg∙kg^-1 dw, and 143-303 μg∙kg^-1 dw respectively. Significant contamination was found at Beirut Port that is surrounded by a densely populated area and is subjected to multidisciplinary activities. Source identification of PAHs was confirmed by using the diagnostic ratio of PAHs with low molecular weight and high molecular weight (LMW/HMW). For PCBs, LCZ is polluted by higher chlorinated congeners with 4 to 9 chlorinated atoms generated from volatilization and combustion processes. Toxicity and biological risks were assessed using toxic equivalent quantity (TEQcarc) and sediment quality guideline quotient (SQGq).

Distribution, sources and ecological risks of organochlorine compounds (DDTs, HCHs and PCBs) in surface sediments from the Pearl River Estuary, China

The Pearl River Estuary is an important sink of organochlorine compounds (OCs), and OC pollution levels in surface sediments remain largely unknown at present. We collected and analysed residual DDTs, HCHs and PCBs of 45 surface sediments from the Pearl River Estuary in 2017. The values of DDTs (1.83 to 6.98 ng·g^-1) and HCHs (0.43 to 2.14 ng·g^-1) were higher in the Humen outlet, and the values of PCBs (4.6 to 187.4 ng·g^-1) were higher in the coastal areas of Shenzhen. The DDTs and HCHs have generally decreased while the PCBs have been rapidly increasing in recent decades. The DDTs might originate from technical DDT and dicofol. The major source of HCHs was lindane. The main potential sources of PCBs were increased industrial products, ship painting, E-waste disassembly, maricultural and agricultural pollution. The total PCBs and DDTs had medium ecological risks according to the sediment quality guidelines.

Sedimentary records of polychlorinated biphenyls in the East China Marginal Seas and Great Lakes: Significance of recent rise of emissions in China and environmental implications

Polychlorinated biphenyls (PCBs) in dated sediment cores from the East China Marginal Seas (ECMSs) and the chronology of the net fluxes to sediments were analyzed. The accumulation of 27 PCBs (ΣPCBs) in the ECMS sediments is about 5-26 ng cm^-2, with the net depositional fluxes of ΣPCBs 10 times lower than those observed in the Great Lakes during the 1960s-1970s. Exponential increases in PCB deposition to the ECMS sediments since the 1990s were observed, which closely follows the fast growth of PCB emissions from industrial thermal processes and e-waste related sources in China. Recent PCB fluxes to the study sites in the ECMSs and the Great Lakes are comparable; the former surged forward with a rising tendency, while the latter showed continued decline after the late 1970s. Due to the different PCB application histories and sources between the two regions, the ECMS sediments may remain as a net sink for land-derived PCBs, while sediments in the Great Lake may have been acting as a secondary source releasing PCBs to water. A higher proportion of trichlorobiphenyls in the ECMS sediments than the Great Lakes was indicated, which may imply the net transport of atmospheric PCBs from China.

Levels of NP and BPA in the Pearl River Estuary, China: Fluctuations with Country Policy Changes over the Past 40 Years

Sediment cores were collected from four outlets in the Pearl River Estuary (Guangdong Province, China) and dated using the ²¹⁰Pb method to investigate the pollution history of the area due to its relatively stable sedimentation status and hydrographic conditions in recent decades. The ages of the sediment cores were dated over 40 years (1968–2015). The concentrations at the four outlets ranged from 2.21 to 48.52 ng g⁻¹ dw for nonylphenol and were non-detectable for 23.64 ng g⁻¹ dw for bisphenol A (BPA), which exhibited a decreasing trend from north to south as well as seaward. The fluxes (2.84 to 112.91 ng cm⁻² yr⁻¹ and non-detectable to 59.33 ng cm⁻² yr⁻¹ for nonylphenol and bisphenol A, respectively) stabilized in the 1980s to 1990s due to the construction of sewage treatment systems. The fluxes increased again in the 21st century, which reached a peak ca. 2010 but declined in recent years due to the establishment of regulations and the decreasing number of industrial enterprises. Fluctuations in the pollution composition coincided with industrial development and governmental policies.

Organochlorines in fish from the coastal coral reefs of Weizhou Island, south China sea: Levels, sources, and bioaccumulation

Eight fish species were sampled from a coastal coral reef ecosystem near Weizhou Island, South China Sea, to investigate the composition profiles and bioaccumulation of organochlorines (OCs). The total concentrations of 18 organochlorine pesticides (OCPs) and 22 polychlorinated biphenyls (PCBs) were found to be 26.5-452 ng/g lw and 0.87-19.8 ng/g lw, respectively. The contaminant distribution pattern indicated that agrochemical sources were more important than industrial sources, and that historical residues remain the primary source of OCs in Weizhou Island. Bioaccumulation factors (BAFs) indicated that dichlorodiphenyltrichloroethanes was bioaccumulating with log BAFs ranging from 3.53 to 5.21. Some congeners diverged from the general trend predicted by the logarithm octanol-water partition coefficient (log K_ow); this was mainly attributable to differences in the bioaccumulation potentials of these congeners in the studied samples. Trophic magnification factors demonstrated that aldrin, endrin, and dieldrin undergo significant trophic dilution, while the other six OC compounds undergo trophic magnification in the food chain. The presence of OCP congeners was also probably affected by their metabolism in fish tissues. The estimated daily intakes of OCPs via fish consumption by residents ranged from 0.05 to 5.45 ng/kg body weight/day, which is below the acceptable daily intake recommended by the FAO/WHO.

The hitchhiker's guide to core samples: Key issues and lessons learned

Core samples may be used as valuable geochronometers for storing historical pollution footprints of organic pollutants. A number of studies have used core samples to evaluate temporal depositions, loading inventories, and effectiveness of environmental mitigation measures. However, in order to get a reliable estimation, certain prerequisites must be satisfied to rule out various confounding factors such as biomixing and melting. This review aims to understand when core samples can or cannot be used as natural archives for organic pollutants. First, we systematically review existing studies of organic pollutants in soil, sediment and ice cores and possible factors that may influence post-depositional fate of chemicals. Then, building on field evidence, model simulation and laboratory leaching tests findings, we discuss issues of post-depositional downward movement in detail. To assist future core sample studies, we summarize lessons learned on study design in the context of sampling design, data analysis, and data reporting. In particular, the combination of a careful study design and appropriate numerical model(s) will help to elevate core samples as a more reliable tool for retrospective understanding of chemical pollution. This review is an initial step toward a better and more accurate use of core samples, and further interdisciplinary cooperation is needed to develop standardized protocols, guidelines and tools.

Apparent relationships between anthropogenic factors and climate change indicators and POPs deposition in a lacustrine system

Climate change and anthropogenic activities are expected to impact the environmental behaviors and fates of persistent organic pollutants (POPs), however, quantitative studies on these combined factors are scarce. In this study, dichlorodiphenyltrichloroethane (DDTs), polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs) were used as examples to identify how and when those factors may be related to the deposition of POPs in the sediment of Lake Chaohu, China, using generalized additive models (GAMs). Three historical trends of DDT, PAH, and PCB deposition were delineated in a dated sediment core encompassing ~100 years of historical record: a steady state or gradually increasing stage, a rapidly increasing stage, and a declining stage. The GAM results showed that aquatic total phosphorus (TP) concentrations and regional GDP (anthropogenic factors) were dominant contributors to POP accumulation rates in the lake sediment. The fitted relationships between air temperature and sedimentary DDT and PAH concentrations were linear and negative, while a positive linear relationship was found for PCBs, suggesting that Lake Chaohu may have become a net source for DDTs and PAHs, and a sink for PCBs, under a progressively warming climate.

Organophosphorus flame retardants in fish from Rivers in the Pearl River Delta, South China

Twelve organophosphorus flame retardants (PFRs) were detected in the muscle of 3 species of fish, mud carp (Cirrhinus molitorella), tilapia (Tilapia nilotica), and plecostomus (Hypostomus plecostomus), from rivers in the Pearl River Delta (PRD) region. The total concentrations of PFRs in the mud carp, tilapia, and plecostomus ranged from 2.3 to 16, 3.4 to 16, and 3.5 to 30 ng/g wet weight (ww), respectively. Generally, tris(2-ethylhexyl) phosphate (TEHP), tris (2-chloro-isopropyl) phosphate (TCPP), tris (2-chloroethyl) phosphate (TCEP), and tri-n-butyl phosphate (TnBP) were the dominant compounds of the PFRs, collectively accounting for up to 90% of the total PFR levels. Concentrations of PFRs were significantly higher in the plecostomus than in the mud carp and tilapia (p < 0.05), which could be explained by differences in habitat and feeding habits of the fish species. High concentrations of PFRs were found mainly in the Guangzhou section of the Pearl River (site P1, P2, and P3) and site B3, which was similar to our previous study of PFRs in sediment from the Pearl River Delta, indicating a relatively high level of PFRs pollution in these regions. The estimated daily intake (EDI) of total PFRs from consumption of fish was 17 ng/kg bw/day to 98 ng/kg bw/day for adults and children, which was three to four orders of magnitude lower than reference dose values.

Occurrence, sources and ecotoxicological risks of polychlorinated biphenyls (PCBs) in sediment cores from urban, rural and reclamation-affected rivers of the Pearl River Delta, China

Sediment cores were collected to a depth of 40 cm (50 cm for urban river sediments) in the Pearl River Delta of China from rural river sediments and river sediments undergoing the process of urbanization and reclamation. Polychlorinated biphenyls (PCBs) in sediment cores were determined to evaluate their levels, distribution, possible sources and potential risks aimed at providing effective information of management practices for local governments. Our results showed that the total concentrations of PCBs (∑16PCBs) in urban, rural and reclamation-affected river sediments ranged from 16.15 to 477.85 μg kg^-1 (dry weight), with mean values of 121.94, 150.49 and 124.20 μg kg^-1 (dry weight), respectively. The most abundant PCB congeners among the study area were light PCBs. Generally, PCBs showed a decreasing trend with depth along sediment cores at most sampling sites. Source analysis indicated that PCBs in the three types of river sediments mainly originated from Aroclor 1242, 1248, 1254 and 1016. Risks evaluation based on sediment quality guideline quotient (SQGQ) showed PCBs at most sampling sites would cause no or moderate adverse biological effects on benthic organisms except surface sediments of U4 and R5 (high adverse biological effects). However, threshold effects level (TEL) is ignored when calculating SQGQ, which might underestimate the risks of PCBs. Thus, a new SQGQ (NSQGQ) taken TEL into consideration was established. Results showed that NSQGQ could evaluate ecotoxicological risks of PCBs better. Redundancy analysis (RDA) showed that PCBs in sediments were positively correlated with sand content and microbial biomass carbon (MBC) (p < 0.05).

Deposition flux and mass inventory of polychlorinated biphenyls in sediments of the Yangtze River Estuary and inner shelf, East China Sea: Implications for contributions of large-river input and e-waste dismantling

Surface sediment samples were collected from the Yangtze River Estuary (YRE) to the inner-shelf mud area of the East China Sea (ECS) for a comprehensive study of the sources and fates of polychlorinated biphenyls (PCBs) based on their spatial distribution, deposition flux, and mass inventory. The total concentrations of 32 PCBs (Σ₃₂PCBs) varied from 0.3 to 11.9 ng/g dry weight. Under strong hydrodynamic conditions, the weak correlations between TOC or MD and Σ₃₂PCB concentrations were observed in the YRE. In contrast, there were relatively well relationships of PCBs with TOC content and sediment grain size in the inner shelf of the ECS due to the influence of hydrological sorting from the YRE to the inner shelf of the ECS. This suggests that the Yangtze River input plays a considerable role in controlling the distribution of PCBs in the coastal ECS. Compared with the annual discharge of Σ₃₂PCBs from the Yangtze River to the sea (3.21 t/yr), the deposition flux was estimated to be ~2.63 t/yr. Furthermore, a total mass inventory of 50 tons in the sediments suggests that the YRE and inner shelf mud of the ECS represents an important global sink of PCBs. Estimated 21-39% of sedimentary PCBs were derived from local emissions (mainly dismantling of electronic waste) aside from Yangtze River input. Higher proportions of penta-CBs were also observed near the central Zhejiang Coast, providing further evidence that the local emission from e-waste dismantling near the coast is a significant contributor to sedimentary PCBs in the coastal ECS.

Historical records and spatial distribution of high hazard PCBs levels in sediments around a large South American industrial coastal area (Santos Estuary, Brazil)

The depositional history of polychlorinated biphenyls (PCBs) was studied from surficial sediments and three sediment cores sampled in the Santos Estuary, an important industrial and urban centre in South America. The maximum concentration (190.7 ng g^-1 dry weight) and inventory (295.50 ng cm^-2) were detected in sediments related to the 1980s, representing a ten-year delay of the emission peak in Brazil. PCB consumption, the congener patterns, and multivariate statistical analyses indicated that the levels started to increase with the intensification of regional urban and industrial development that continued to interfere in the magnitude of input during the past 50 years. In addition, the risk assessment indicates that levels observed in most of the samples are in a range capable of producing ecological risks to the marine biota. This study provides the first estimates of historic sediments PCB inventories in the Southwestern Atlantic, contributing data for regional and global management and highlighting the role of sediment as a compartment for permanently storing POPs and the risks involved in their resuspension, especially in regions that are constantly dredged such as the Santos Estuary.

Polychlorinated biphenyls in the Yellow River of Henan section: occurrence, composition, and impact factors

The levels, spatial variation, congener profiles, impact factors, and ecological risk of polychlorinated biphenyls (PCBs) in the sediment from the Yellow River of Henan section, China, were investigated in this paper. Total concentration of 31 PCBs and seven indicator PCBs varied from ND to 1015 pg g^-1 and ND to 423 pg g^-1, respectively. Compared with other aquatic environments around China, PCB levels in the studied area were relatively low. Spatial variations revealed that tributaries possessed higher PCB levels, in comparison to mainstream, which acted as input sources of PCBs in the mainstream. The homolog profiles were dominated by lighter PCBs (Tri-PentaCBs), contributing above 70% of total PCBs. Correlation analysis between PCB concentrations and total organic carbon indicated that local input or atmospheric deposition was the primary controls of spatial variation of PCBs. According to simple sediment quality guidelines (SQG), the risks posed by PCBs in the sediments might be negligible.

Legacy and emerging organohalogenated contaminants in wild edible aquatic organisms: Implications for bioaccumulation and human exposure

Highly industrialized and urbanized watersheds may receive various contaminants from anthropogenic activities. In this study, legacy and emerging organohalogenated contaminants (OHCs) were measured in edible wild aquatic organisms sampled from the Pearl River and Dongjiang River in a representative industrial and urban region in China. High concentrations of target contaminants were observed. The Pearl River exhibited higher concentrations of OHCs than the Dongjiang River due to high industrialization and urbanization. Agrochemical inputs remained an important source of OHCs in industrialized and urbanized watershed in China, but vigilance is needed for recent inputs of polychlorinated biphenyls (PCBs) originated from e-waste recycling activities. Bioaccumulation of dichlorodiphenyltrichloroethane and its metabolites (DDTs), hexachlorocyclohexanes (HCHs), PCBs, polybrominated diphenyl ethers (PBDEs), and Dechlorane Plus (DP) was biological species- and compound-specific, which can be largely attributed to metabolic capability for xenobiotics. No health risk was related to the daily intake of DDTs, HCHs, and PBDEs via consumption of wild edible species investigated for local residents. However, the current exposure to PCBs through consuming fish is of potential health concern.

Organophosphorus flame retardants in mangrove sediments from the Pearl River Estuary, South China

Forty-eight surface sediments were collected from three mangrove wetlands in the Pearl River Estuary (PRE) of South China to investigate the distribution of organophosphorus flame retardants (OPFRs) and the relationship between OPFRs and microbial community structure determined by phospholipid fatty acid. Concentrations of ΣOPFRs in mangrove sediments of the PRE ranged from 13.2 to 377.1 ng g^-1 dry weight. Levels of ΣOPFRs in mangrove sediments from Shenzhen and Guangzhou were significantly higher than those from Zhuhai, indicating that OPFRs were linked to industrialization and urbanization. Tris(chloropropyl)phosphate was the predominant profile of OPFRs in mangrove sediments from Shenzhen (38.9%) and Guangzhou (35.0%), while the composition profile of OPFRs in mangrove sediments from Zhuhai was dominated by tris(2-chloroethyl) phosphate (25.5%). The mass inventories of OPFRs in the mangrove sediments of Guangzhou, Zhuhai and Shenzhen were 439.5, 133.5 and 662.3 ng cm^-2, respectively. Redundancy analysis revealed that OPFRs induced a shift in the structure of mangrove sediment microbial community and the variations were significantly correlated with tris(1,3-dichloro-2-propyl)phosphate and tris(2-butoxyethyl) phosphate.

Depositional history and inventories of polychlorinated biphenyls (PCBs) in sediment cores from an Antarctic Specially Managed Area (Admiralty Bay, King George Island)

Temporal patterns, fluxes and inventories of polychlorinated biphenyls (PCBs) were assessed in nine sediment cores collected from selected areas of Admiralty Bay off the Antarctic Peninsula. Concentrations of total PCBs were low, but slightly higher in comparison to low-impacted, remote environments in the world, ranging from below the detection limit to 11.9ngg^-1 in dry weight. PCB concentrations and inventories suggest a possible minor influence related to the nearby logistic activities, especially in the sediment core collected close to the Ferraz Station. Despite being the most remote and protected area on the planet, the Antarctic continent is no longer a pristine environment.

Long-Term Temporal Trends of Polychlorinated Biphenyls and Their Controlling Sources in China

Polychlorinated biphenyls (PCBs) are industrial organic contaminants identified as persistent, bioaccumulative, toxic (PBT), and subject to long-range transport (LRT) with global scale significance. This study focuses on a reconstruction and prediction for China of long-term emission trends of intentionally and unintentionally produced (UP) ∑₇PCBs (UP-PCBs, from the manufacture of steel, cement and sinter iron) and their re-emissions from secondary sources (e.g., soils and vegetation) using a dynamic fate model (BETR-Global). Contemporary emission estimates combined with predictions from the multimedia fate model suggest that primary sources still dominate, although unintentional sources are predicted to become a main contributor from 2035 for PCB-28. Imported e-waste is predicted to play an increasing role until 2020-2030 on a national scale due to the decline of intentionally produced (IP) emissions. Hypothetical emission scenarios suggest that China could become a potential source to neighboring regions with a net output of ∼0.4 t year^-1 by around 2050. However, future emission scenarios and hence model results will be dictated by the efficiency of control measures.

Atmospheric deposition exposes Qinling pandas to toxic pollutants

The giant panda (Ailuropoda melanoleuca) is one of the most endangered animals in the world, and it is recognized worldwide as a symbol for conservation. A previous study showed that wild and captive pandas, especially those of the Qinling subspecies, were exposed to toxicants in their diet of bamboo; the ultimate origin of these toxicants is unknown. Here we show that atmospheric deposition is the most likely origin of heavy metals and persistent organic pollutants (POPs) in the diets of captive and wild Qinling pandas. Average atmospheric deposition was 199, 115, and 49 g·m^-2 ·yr^-1 in the center of Xi'an City, at China's Shaanxi Wild Animal Research Center (SWARC), and at Foping National Nature Reserve (FNNR), respectively. Atmospheric deposition of heavy metals (As, Cd, Cr, Pb, Hg, Co, Cu, Zn, Mn, and Ni) and POPs was highest at Xi'an City, intermediate at SWARC, and lowest at FNNR. Soil concentrations of the aforementioned heavy metals other than As and Zn also were significantly higher at SWARC than at FNNR. Efforts to conserve Qinling pandas may be compromised by air pollution attendant to China's economic development. Improvement of air quality and reductions of toxic emissions are urgently required to protect China's iconic species.

Distribution, mass inventories, and ecological risk assessment of legacy and emerging contaminants in sediments from the Pearl River Estuary in China

This study focused on comparing the occurrences and environmental toxic risks for diverse priority and emerging contaminants (>100 chemicals) in the sediments from the Pearl River Estuary (PRE, China). The most predominant compounds were cationic surfactants, organophosphate flame retardants (e.g., triisobutylphosphate), and polycyclic aromatic hydrocarbons (PAHs), accounting for >75% of the total mass inventory (∼330 metric tons). Wastewater discharges seem to be one of the main sources of pollution in the area, as the highest concentrations (>1000ngg^-1 for some chemicals) were reported in the upper part of the PRE (near Guangzhou city) and Macau. Highest levels of ultraviolet (UV) filters, however, were observed in recreational areas, revealing the importance of direct sources (e.g., outdoor activities). An environmental risk assessment showed that PAHs and dichlorodiphenyl dichloroethylene had the highest hazard quotient (HQ) values (up to 233). Nonylphenol, a metabolite from nonionic surfactant, and two UV filters (2-ethyl-hexyl-4-trimethoxycinnamate and 4-methylbenzylidene camphor) also posed a significant threat to benthic species (HQ>1). Further research through the realization of monitoring campaigns and toxicity tests is encouraged, as the exposure of the resident aquatic organisms and human population to these and other emerging chemicals is expected to increase over the years.

National investigation of semi-volatile organic compounds (PAHs, OCPs, and PCBs) in lake sediments of China: Occurrence, spatial variation and risk assessment

In this study, a large scale investigation of semi-volatile organic compounds (SVOCs) in sediments from 52 lakes, located in five geographic regions across China, was conducted to assess sediment quality in terms of organic contaminants. Concentrations of polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs), and polychlorinated biphenyls (PCBs) in sediment were found to range between 17.00-6,633, 0.12-45.24, and 0.03-13.99ngg^-1, respectively. Lake sediments from different regions exhibited variation in contamination levels, and in the compositions of isomers. The descending order of contamination levels for the three SVOCs groups (i.e., ∑PAHs, ∑OCPs, ∑PCBs) were as follows: the eastern plain region (EPR)>the Yunnan-Guizhou plateau (YGP)>the northeast China region (NCR)>the Qinghai-Tibet plateau (QTP)>the Mongolia-Xinjiang plateau (MXP). High molecular weight PAHs, OCPs and PCBs were found at high concentrations in parts of the EPR and YGP, while lighter isomers were likely to be atmospherically transported, resulting in their nationwide distribution. The sources and type variation (local input or atmospheric deposition) are the primary controls of spatial variation. Additionally, human related socio-economic factors, and geographic conditions also played important roles in influencing the spatial differentiation. According to simple sediment quality guidelines (SQG), the risks posed by PCBs in sediments were not as serious as those posed by PAHs and DDT.

Distributions of organochlorine compounds in sediments from Jiulong River Estuary and adjacent Western Taiwan Strait: Implications of transport, sources and inventories

Estuaries and coastal areas strongly influenced by terrestrial inputs resulted from anthropogenic activities. To study the distributions, origins, potential transport and burden of organochlorine compounds (OCs) from river to marginal sea, organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) were investigated in surface sediments collected from a subtropical estuary (Jiulong River Estuary, JRE) and the inner shelf of adjacent Western Taiwan Strait (WTS). The concentrations of OCPs and PCBs were from 5.2 to 551.7 and 1.0-8.1 ng g^-1 (dry weight), respectively. OCP concentrations in the JRE were higher than in adjacent WTS, and a decreasing trend with the ascending distance from the estuary to the open sea was observed. Concentrations of DDTs were quite high in the upper reach of the estuary, inferred from antifouling paint on fishing boats of a local shipping company. According to established sediment quality guidelines, DDTs in the JRE posed potential ecological risk. HCHs in the estuary were mainly derived from the weathered HCHs preserved in the agriculture soils via local major river runoffs. OCPs patterns showed that OCPs in the south coast of WTS were resulted from local sources via river input, while OCPs in the north coast attributed to the long-range transport derived by the Fujian-Zhejiang Coastal Current. Minor variations of PCB concentrations and homologs indicated that PCBs were not the main pollutant in the agricultural region, consistent lighter PCBs reflected industrial PCBs were transported via atmospheric deposition derived by East Asia Monsoon. Moreover, the primary distribution pattern founded for DDTs and the considerable mass inventories and burdens calculated (258.1 ng cm^-2 and 10.4 tones for OCPs) that higher than Pearl River Delta and Yangtze River Delta, together suggested that the contaminated sediments in the study area may be a potential source of OCPs to the global ocean.

PCBs and OCPs in fish along coastal fisheries in China: Distribution and health risk assessment

PCBs and OCPs were analyzed in fish (bass) taken along Chinese coastal fisheries. In the bass muscle, PCB, DDT and HCH concentrations were in the range of 1.02-2.2ng/g, 0.44-1.74 and 2.84-106.11ng/gww, respectively. Spatial distribution showed that the concentrations of target contaminants in bass from south fisheries were in general much lower than those from north fisheries in China. The ratios of OCP congeners suggested that technical DDT was not the main input and a recent usage of lindane or old technical HCH residuals could be the source of HCHs. The OCC concentrations in liver (127-442.43ng/gww) from selected samples were 8-12 and 10-14 times higher than those in gills and muscles, respectively. Based on the maximum allowable fish assumption rate (CRlim and CRmm), it could cause human health risk, by consuming bass samples taken from highly contaminated fisheries including QD and ST.

Polychlorinated biphenyls (PCBs) in sediments from the western Adriatic Sea: Sources, historical trends and inventories

Sources, historical trends and inventories of polychlorinated biphenyls (PCBs) were investigated in sediments collected in five transects along the north-south axis of the western Adriatic Sea. The concentration of total PCBs (∑28 PCBs) ranged from <LOD (limit of detection) to 9.0ngg(-1) in the sediment cores and between 0.1 and 2.2ngg(-1) in recent sediments. Chronological records of PCB concentrations displayed a common pattern with historical PCB production and use, with the maximum peak values detected between the 1960s and the 1980s. Sediments deposited within the last two decades presented a ~40% to ~80% PCB reduction in comparison to the peak levels, reflecting the ban on PCB production and use since the late 1970s. PCB levels along with the presence of high-chlorinated congeners decreased southwards, indicating the Po River as the major source of PCBs in the western Adriatic Sea. This is further corroborated by the estimated inventories of PCBs, which were ~4-7 times higher in the Po River prodelta (256ngcm(-2)) in comparison to the middle and southern Adriatic, respectively, and about 100 times higher than the in the deep Adriatic Sea.

Levels, congener profile and inventory of polychlorinated biphenyls in sediment from the Songhua River in the vicinity of cement plant, China: a case study

This study investigated the contamination levels, homologue, and congener profiles and evaluated the residue inventory of polychlorinated biphenyls (PCBs) in sediment of the Songhua River in the vicinity of cement plant. The total concentration of detected 35 PCB congeners ranged from 1.12 to 2.19 ng/g dry weight (dw) in sediment, with a mean value of 1.56 ng/g dw, and the concentration of PCBs decreased in the following order: the downstream > cement plant > upstream. The results of total organic carbon (TOC)-normalized PCB concentrations indicate that the sediments have low potential ecological risk in this area. The study results on homologue and congener of PCBs show that the emissions from cement production could be the major sources of PCBs in sediment, and the low-chlorinated PCBs will be exchanged among air, water, and sediment with increasing temperature during summer and flow to downstream with water during the wet season. The spatial density and total burden of PCBs in the surface sediments were 17.2 ng/cm(2) and 1.2 kg, respectively. To our knowledge, this study is the first to explore the pollution characteristics of unintentionally produced PCB emissions from cement industry by means of monitoring sediment samples.

Polychlorinated biphenyls (PCBs) in sediments/soils of different wetlands along 100-year coastal reclamation chronosequence in the Pearl River Estuary, China

PCBs (polychlorinated biphenyls) were determined in sediment/soil profiles to a depth of 30 cm from three different wetlands (i.e., ditch wetlands, riparian wetlands and reclaimed wetlands) of the Pearl River Estuary to elucidate their levels, distribution and toxic risks along a 100-year chronosequence of reclamation. All detected PCB congeners and the total 15 PCBs (∑15 PCBs) decreased with depth along sediment/soil profiles in these three wetlands. The ∑15 PCBs concentrations ranged from 17.68 to 169.26 ng/g in surface sediments/soils. Generally, old wetlands tended to have higher PCB concentrations than younger ones. The dominant PCB congeners at all sampling sites were light PCB homologues (i.e., tetra-CBs and tri-CBs). According to the sediment quality guideline, the average PCB concentrations exceeded the threshold effects level (TEL, 21.6 ng/g) at most of the sampling sites, exhibiting possible adverse biological effects, which were dominantly caused by light PCB congeners. The total toxic equivalent (TEQ) concentrations of 10 dioxin-like PCBs (DL-PCBs) detected at all sampling sites ranged from 0.04 to 852.7 (10(-3) ng/g), mainly affected by PCB126. Only DL-PCB concentrations in ditch and riparian wetland sediments with 40-year reclamation histories (i.e., D40 and Ri40) exhibited moderate adverse biological effects according to SQGQ values. Principal component analysis indicated that PCBs in three wetland sediments/soils mainly originated from Aroclor 1016, 1242, and 1248. Correlation analysis showed that sediment/soil organic carbon content had a significant correlation with the concentrations of several PCB congeners (P < 0.05), whereas no significant correlations were observed between any PCBs congeners and grain size or aggregate content (P > 0.05).

Spatial-temporal variation, possible source and ecological risk of PCBs in sediments from Songhua River, China: Effects of PCB elimination policy and reverse management framework

The spatial variation, possible sources and ecological risk of polychlorinated biphenyls (PCBs) in the sediment from the Songhua River, China were investigated and evaluated in this paper. The total concentration of PCBs ranged from 0.59 to 12.38ng/gdw, with a mean value of 3.82ng/gdw. The seven indicators of PCB concentrations are significantly correlated with the total PCB concentrations (R=0.950, p=0.000). The temporal trend of PCBs in sediments showed that the total PCBs in the Songhua River have decreased since 2008. Point source pollution, discharge of historical usage and industrial sewage, and emissions of unintentionally produced PCBs were the predominant sources in sediment. A risk assessment indicated that most of the sampling sites in the sediment were at low potential ecological risk. The apparent decrease of PCBs in the sediment appeared after the China National Coordination Group for Implementation of the Stockholm Convention was established. A conceptual reverse management framework for PCBs and other organic pollutants was established in this study.

Short-chain chlorinated paraffins in marine organisms from the Pearl River Estuary in South China: Residue levels and interspecies differences

There is limited information available on the bioaccumulation of short-chain chlorinated paraffins (SCCPs), a complicated group of persistent organic pollutants (POPs) candidates listed in the Stockholm Convention, in estuarine ecosystem. This study analyzed SCCPs in marine organisms (five fish and six invertebrates) from the Pearl River Estuary in South China. The concentrations of total SCCPs ranged from 210 to 21,000 ng · g(-1) lipid weight, with relatively higher levels in benthic invertebrates (shrimp, crabs and bivalves) than in non-benthic species (pelagic and mesopelagic fish and squid). SCCPs were biomagnified from prey fish (tapertail anchovy, Coilia mystus) to predator fish (Bombay duck, Harpadon nehereus), and the biomagnification factors (BMFs) of SCCP congeners ranged from 1.1 (C10H16Cl6) to 3.4 (C13H18Cl10). Species-specific homologue group patterns were also observed, with significantly lower proportions of C10 congeners in the shrimp, bivalves and Bombay duck than in the other species.

Persistent halogenated compounds in fish from rivers in the Pearl River Delta, South China: Geographical pattern and implications for anthropogenic effects on the environment

Three fish species, mud carp (Cirrhinus molitorella), tilapia (Tilapia nilotica), and plecostomus (Hypostomus plecostomus), from rivers in the Pearl River Delta (PRD) were analyzed for dichlorodiphenyltrichloroethane and its metabolites (DDTs), hexachlorocyclohexanes (HCHs), polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), decabromodiphenyl ethane (DBDPE), and Dechlorane Plus (DP). The concentrations of DDTs, HCHs, PCBs, PBDEs, DBDPE, and DP ranged from 380-57,000, 5.5-100, 30-4200, 6.9-690, 0.29-460, and 0.09-20ng/g lipid weight, respectively. Congener profiles or chemical compositions of PBDEs, DPs, DDTs, and HCHs in plecostomus differed significantly from those in the other two fish species, which can be ascribed to species-specific metabolism. DDTs derived from historical residue and land erosion remained the predominant pollutants in the PRD, while industrial and urban activities resulted in elevated levels of PCBs and PBDEs in the metropolitan area. E-waste recycling activities have greatly impacted on the adjacent aquatic environment, and the potential point source for DBDPE was also revealed.

Current levels, composition profiles, source identification and potentially ecological risks of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in the surface sediments from Bohai Sea

Polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) were analyzed to assess the environmental quality in the surface sediments from Bohai Sea (BS), China. Concentrations of ∑37PCBs, ∑7PBDEs and BDE-209 were 0.157-1.699, 0.100-0.479 and 0.464-6.438 ng/g (dry weight), respectively. All of these concentrations decreased generally from the coastal areas towards the outer sea, indicating intensive influences of anthropogenic activities. Principal component analysis (PCA) coupled with multiple linear regression (MLR) revealed that 82.1% of the PCBs in BS came from direct discharge of local anthropogenic activities, 16.3% from surface runoff of contaminated soils and 1.6% from atmospheric deposition. PBDEs were mainly derived from the usage and dismantling of products containing commercial Penta-, Octa- and Deca-BDEs. According to sediment quality guidelines (SQGs), the ecological risks of PCBs could be negligible, and penta- and deca-BDE homologs might be the major contributors of ecological risks in the BS sediments.

Legacy and emerging halogenated organic pollutants in marine organisms from the Pearl River Estuary, South China

A suite of legacy and emerging halogenated organic pollutants (HOPs) were measured in marine organisms (coastal fish and invertebrates) from the Pearl River Estuary, South China, to investigate the current contamination status after the Stockholm Convention was implemented in China. Dichlorodiphenyltrichloroethane and its metabolites (DDTs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs) were detected in all samples at concentrations of 54-1500, 16-700, and 0.56-59ng/g lipid weight, respectively. Dechlorane Plus (DP), decabromodiphenyl ethane (DBDPE), 2,3,5,6-tetrabromo-p-xylene (pTBX), and pentabromotoluene (PBT) were also found at concentrations of ND (non-detectable) to 37ng/g lipid weight. The concentrations of these investigated contaminants in the present study were at moderate levels, as compared with those reported in other regions. Significant interspecies differences were found in the levels of DDTs, PCBs, PBDEs and the alternative halogenated flame retardants (AHFRs). DDTs were the predominant HOPs in those species and represented >50% of the total HOPs, followed by PCBs, PBDEs, and AHFRs. The total estimated daily intakes (EDIs) of DDTs, PCBs, PBDEs, and AHFRs were 28, 12, 1.0, and 0.18 (ng/kg)/d, respectively, via seafood consumption. These concentrations are not expected to pose health risks to humans.

An assessment of human influences on sources of polycyclic aromatic hydrocarbons in the estuarine and coastal sediments of China

Sediments collected from the coastal area of China, embracing west coast of Bohai Sea, south coast of Shandong Peninsula, and the Changjiang estuary (listed in order of decreasing north latitude), were analyzed for polycyclic aromatic hydrocarbons (PAHs). ∑PAH (Sixteen US EPA priority PAHs) were 2.7-350.9ng/g. Petroleum residue was the major contributor of PAHs in the coastal sediments of China due to oil leakage from ships and offshore oil fields. The contribution of vehicular emissions in coast of North China was significantly lower than that in the Changjiang Estuary, and the reverse was true for coal combustion. PAH concentrations in the sediment core of the Changjiang estuary steadily increased upward and the variation was primarily due to economic development and severe floods. The impact on PAHs by vehicular emissions (37.2%) and petrogenic sources (45.8%) overwhelmed combustion sources (17.0%).

Residual Distribution and Risk Assessment of Polychlorinated Biphenyls in Surface Sediments of the Pearl River Delta, South China

We analyzed residual PCBs in surface sediments at 19 sites in the Pearl River Delta in the wet and dry seasons. Seven indicative PCB congeners (PCB28, PCB52, PCB101, PCB118, PCB153, PCB138 and PCB180) were detected in the surface sediments, among which the detection rate and mass concentrations of PCB52 were the highest. Total concentrations of the seven PCBs ranged from 19.8 to 111 μg/kg, with an average of 48.2 μg/kg. For the spatial distribution, the sum of the seven PCB (∑PCB) concentrations for the stations that were located in the city region of the Pearl River Delta were significantly higher than the ∑PCB concentrations for the eight outlets of the Pearl River Delta (p < 0.05). According to the US National Oceanic and Atmospheric Administration ERL and ERM guideline concentrations, the PCB concentrations may occasionally lead to adverse effects, especially in the dry season.