Historical PCB fluxes in the Mexico City Metropolitan Zone as evidenced by a sedimentary record from the Espejo de los Lirios lake

Occurrence, sources and risk assessment of 12 dioxin-like polychlorinated biphenyls (DL-PCBs) in sediments from the Soummam River protected area, Algeria: A potential threat to the Mediterranean Sea

The levels, the sources and the potential risks associated with twelve dioxin-like PCBs were investigated in the sediments of the Soummam River in northeastern Algeria. Total dl-PCBs concentrations ranged from 3.64 ng/g to 9.38 ng/g with PCB 118 and PCB 105 being the predominant congeners. Principal component analysis suggested that commercial mixtures and municipal waste incineration could be responsible for the presence of PCBs in the region. TEQ values ranged from 12.93 pg/g to 60.98 pg/g indicating adverse effects on aquatic organisms. Moreover, cancer risk assessed via Total Lifetime Cancer Risk (TLCR) suggested that for all the stations, the risk was low but not negligible. Additionally, the non-cancer risk was significant at half of the stations for children but negligible for adults at all the stations. Consequently, measures must be taken by local authorities to protect the environment and the human health.

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.

A 110 Year Sediment Record of Polycyclic Aromatic Hydrocarbons Related to Economic Development and Energy Consumption in Dongping Lake, North China

A sedimentary record of the 16 polycyclic aromatic hydrocarbon (PAH) pollutants from Dongping Lake, north China, is presented in this study. The influence of regional energy structure changes for 2–6-ring PAHs was investigated, in order to assess their sources and the impact of socioeconomic developments on the observed changes in concentration over time. The concentration of the ΣPAH₁₆ ranged from 77.6 to 628.0 ng/g. Prior to the 1970s, the relatively low concentration of ΣPAH₁₆ and the average presence of 44.4% 2,3-ring PAHs indicated that pyrogenic combustion from grass, wood, and coal was the main source of PAHs. The rapid increase in the concentration of 2,3-ring PAHs between the 1970s and 2006 was attributed to the growth of the urban population and the coal consumption, following the implementation of the Reform and Open Policy in 1978. The source apportionment, which was assessed using a positive matrix factorization model, revealed that coal combustion was the most important regional source of PAHs pollution (>51.0%). The PAHs were mainly transported to the site from the surrounding regions by atmospheric deposition rather than direct discharge.

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.

Recent history of persistent organic pollutants (PAHs, PCBs, PBDEs) in sediments from a large tropical lake

²¹⁰Pb-dated sediment cores and surface sediments from Lake Chapala (LC), Mexico, were analyzed to assess the temporal trends in concentrations and fluxes of persistent organic pollutants (POPs: PAHs, PCBs and PBDEs). Total sediment concentrations of PAHs (95-1,482 ng g^-1), PCBs (9-27 ng g^-1) and PBDEs (0.2-2.5 ng g^-1) were indicative of moderate to intense contamination. The POP concentrations have progressively increased since the 1990s. The light molecular weight PAHs, and the prevalence of PCB congeners with low-chlorination levels (e.g., di- to tri-CB) and low-to medium-brominated (tri- to penta-BDE) PBDEs in most sections of the sediment profiles, suggested that these POPs have most likely reached these sediments by long-range atmospheric transport from distant sources; although the significant presence of heavier PAH, PCB and PBDE congeners in the topmost sediments, indicate that other nearby and local sources (soil erosion from the catchment, urban and industrial wastewaters discharges, as well as navigation) might have also contributed to the recent input of POPs to LC. Taking into account the relevance of LC as regional freshwater supply and commercial fishing ground, the potential risk posed by the organic contaminated sediments to the biota and human population should not be underestimated.

Historical Characteristics of Contamination and Risk of Heavy Metals in Weishan Lake, China

Combined with the dating analysis of ²¹⁰Pb and ¹³⁷Cs, the historical concentration and risk of As, Cd, Cr, Cu, Hg, Ni, Pb and Zn in the core sediment of Weishan Lake were determined. Pollution concentrations, enrichment factor, geo-accumulation index, and ecological risk index of these metals and C/N ratio indicate that the natural inputs prevailed till early 1900s. From late 1970s onwards, the risk posed by these metals was significantly increased. Cu and Hg might cause adverse biological effects. The increase of soil erosion and wastewater discharge in the watershed promoted input and accumulation of these metals in the lake. The coal and petroleum industry in the catchment led the more accumulation of Hg, Cd and Cu in the lake.

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.

Concentration and fractionation of heavy metals in the old yellow river estuary, china

A sequential extraction procedure was applied to determine the concentration and fractionation characteristics of eight heavy metals (HMs) (Cu, Zn, Pb, Cd, Cr, Fe, Mn, and Ni) in a sediment core collected from the old Yellow River Estuary, China. The results revealed that the mean deposition rate of this sediment core, which spanned 87 yr (1925-2012), was approximately 0.5 cm yr. The mean concentrations and ranges of HMs were Cu: 26.9 (18.3-38.5), Zn: 76.4 (51.0-107), Pb: 37.3 (17.8-53.8), Cd: 0.23 (0.20-0.27), Cr: 84.7 (45.5-116), Fe: 24,000 (16,500-31,700), Mn: 709 (388-1020), and Ni: 36.1 (24.8-47.2) mg kg (dry weight). Six HMs (Cu, Zn, Cr, Cd, Fe, and Ni) were present in their highest proportion in the residual fraction; their lowest proportion was observed in the exchangeable fraction. Lead primarily existed in the oxidizable or residual fraction. Manganese was mainly presented in the exchangeable fraction. The risk assessment code results revealed that the sediments displayed a low risk for Cu, Zn, Pb, Cr, Cd, Fe, Mn, and Ni. The HMs Cu, Zn, Cr, Cd, Mn, and Ni displayed minor enrichment in the sediment core, whereas for Pb, moderate contamination enrichment was observed. Overall, an increase in and total concentration of HMs occurred since 1925 and reached a maximum value around 1980, after which there was a larger fluctuation or decline until 2012. We also found that the degree of HM pollution during the 1976-1996 period was less serious than before 1976. All the sediment samples exceeded the effect range low (ERL) for Ni, whereas 56.1, 7.32, and 17.1% exceeded the ERL values for Cr, Cu, and Pb; no samples exceeded the ERL for Zn or Cd.

Long-range atmospheric transport of persistent organic pollutants to remote lacustrine environments

Concentrations, temporal trends and fluxes of persistent organic pollutants (POPs: PAHs, PCBs and PBDEs) were determined in soil and (210)Pb-dated sediment cores from remote lacustrine environments (El Tule and Santa Elena lakes) in rural areas of Central Mexico. In both areas, the concentrations of target analytes in soil and sediment samples were comparable and indicative of slightly contaminated environments. The prevalence of low-molecular-weight PAHs in soils suggested their mainly atmospheric origin, in contrast to the aquatic sediments where runoff contribution was also significant. Increasing contamination trends of PCBs and PBDEs were evident, showing maximum fluxes of 4.8 ± 2.1 and 0.3 ± 0.1 ng cm(-2) a(-1) for PCBs and PBDEs, respectively. The predominance of lower-brominated PBDEs and lower-chlorinated PCBs in soils and sediments indicated that their presence is mostly due to long-range atmospheric transport.

Historical records of organic pollutants in sediment cores

Analyses of sediment core samples are primary sources of historical pollution trends in aquatic systems. Determining organic compounds, such as POPs, in the dated sediments enables the estimation of their temporal concentration changes and the identification of the contaminant origin in local regions. Wars, large-scale fires, economical transitions, and bans on certain chemicals are reflected in the sediment organic compound concentrations. The high POP concentrations in surficial sediments suggest that these chemicals, even after being banned, remain in the environment. Furthermore, vertical profiles can help in understanding the sedimentation process and in estimating effective countermeasures against pollution. Moreover, studies published during the period 1991-2013 on PAHs, PCBs, OCPs, dioxins and dioxin-like compound concentrations in sediment core samples are reviewed.

Halogenated organic contaminants (HOCs) in sediment from a highly eutrophicated lake, China: occurrence, distribution and mass inventories

Halogenated organic contaminants (HOCs) including 16 polybrominated diphenyl ethers (PBDEs) and 37 polychlorinated biphenyls (PCBs) were determined in 49 surfacial sediments from Chaohu Lake, a highly eutrophicated lake, China. PBDEs were detected in almost samples with the range of the total concentration (defined as Σ(16)PBDEs) from 0.84 to 86.6 ng g(-1). Compared with the occurrence of PBDEs in Pearl River Delta and Yangtze River Delta in China, lower percentage of BDE-209 over the concentration of Σ(16)PBDEs was inferred by the high-volume application of penta-BDE mixture product for local domestic furniture purpose. The total concentration of 37 PCBs (Σ(37)PCBs) ranged from 0.05 to 3.36 ng g(-1) with the most detection of PCB-1, -4, -52 and -71. Both the concentrations of Σ(16)PBDE and Σ(37)PCB poorly correlated with total organic carbon (TOC), suggesting the significant contribution of phytoplankton organic carbons to sediment TOC. The contamination by PBDEs and PCBs in western region of the lake was significantly more serious than in eastern lake. Our findings about the higher residues of PBDEs and PCBs in sediments at the estuary of Nanfei River compared to the other estuaries also supported the conclusion that urban area (Hefei city) was the main source of PBDEs and PCBs. The comparison with the concentration of HOC in the present study with those in other lacustrine sediments around the world suggested the contamination by PBDEs in Chaohu Lake is at middle of the global concentration range, whereas PCBs is at low end of the global range which could be elucidated by local economic development and historical usage of PBDEs and PCBs. The mass inventories of HOCs in the lake were estimated at 561 and 38 kg, which corresponds to only 0.000006% and 0.0001% of these global historical produce volumes, respectively.

Polychlorinated biphenyls (PCBs) residues in milk from an agroindustrial zone of Tuxpan, Veracruz, Mexico

The coasts of the Gulf of Mexico are zones exposed to the exploration and exploitation of petroleum sources, and the products generated in agricultural zones may become contaminated by persistent organic pollutants (POPs). The objective of the present study was to evaluate the presence of polychlorinated biphenyl compounds (PCBs) in milk from dairy production units near sources of environmental pollutants. It was confirmed that the seven congeners of nondioxin-like PCBs (NDL-PCBs) are present in milk where compounds PCB101, PCB118, PCB153 and PCB180 appear in 100% of the samples analyzed, the rank of concentration for the sum of the seven congeners fluctuating between 2.6 and 26 ng g(-1) with a median of 6 ng g(-1). None of the samples surpassed the provisional value established by the EU of 40 ng g(-1) of milk fat for the sum of the seven congeners, indicator that was not affected by the season of the year (p<0.05), whose median of 8.6 ng g(-1) and 6.3 ng g(-1) for rain and drought respectively. The concentrations of NDL-PCBs found in milk do not represent a problem for human health; however, they alert the existence of spontaneously generated, uncontrolled sources that may represent a potential danger for human and animal health.

Historical changes in polycyclic aromatic hydrocarbons (PAHs) input in Lake Baiyangdian related to regional socio-economic development

The accumulation of polycyclic aromatic hydrocarbons (PAHs) over a period of almost 180 years was studied in a sediment core collected from Lake Baiyangdian in northern China. Total PAHs concentration varied from 97.2 to 2402 ng g(-1) dry weight. We found the highest total PAH concentration in 1940s and 1990s, and a decreasing trend from 1990 until present. The warfare and increasing economic activity had the largest impact on the PAH vertical distribution. The implemented measures for pollution control in catchment since 1990 might reduce point source input of PAH in some degree in recently. The historical record of PAHs is different from the developed countries and areas due to difference in socio-economic development condition. PAHs in the core are dominantly pyrogenic in source, i.e., they are mainly from the incomplete combustion of wood and coal. PAHs from terrigenous organic matter input decreased obviously from the 1950s due to rainfall reduction during this period.