Sedimentary record of polycyclic aromatic hydrocarbons and DDTs in Dianchi Lake, an urban lake in Southwest 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.

Historical trends of traditional, emerging, and halogenated polycyclic aromatic hydrocarbons recorded in core sediments from the coastal areas of the Yellow and Bohai seas

Historical trends of polycyclic aromatic hydrocarbons (PAHs) contamination were reconstructed from eleven sediment cores located in intertidal zones of the Yellow and Bohai seas for a period encompassing the last 80 years. The analysis encompassed 15 traditional PAHs (t-PAHs), 9 emerging PAHs (e-PAHs), and 30 halogenated PAHs (Hl-PAHs), including 10 chlorinated PAHs (Cl-PAHs) and 20 brominated PAHs (Br-PAHs). Concentrations of target PAHs were highest in industrial and municipal areas situated along the coast of the Bohai Sea, including Huludao, Yingkou, Tianjin, and Dandong, constituting a substantial mass inventory. All target PAHs showed increasing trends since the 1950s, reflecting the development history of South Korea and China. High molecular weight PAHs accumulated in sampling sites more than low molecular weight PAHs. A positive matrix factorization model showed that the PAH sources were coal and gasoline combustion (35%), diesel combustion (33%), and biomass combustion (32%). Over the last 80 years, the contribution of coal and gasoline combustion increased in all regions, while diesel combustion and biomass combustion varied across regions and over time. Toxicity equivalence values were highest for t-PAHs (>99% contribution), followed by Cl-PAHs, Br-PAHs, and e-PAHs. Concentrations of t-PAHs in Eastern Asia seas have increased since the 1900s, particularly in intertidal areas compared to subtidal areas. The intertidal zone removed 83% of the total flux of PAHs originating from land and thus appears to serve as a buffer zone against marine pollution. Overall, this study provides novel knowledge on the historical trends and sources of PAHs on a large scale, along with insights for future coastal management.

Sedimentary records of human activities in China over the past two millennia and implications for the Anthropocene: A review

Human activities have profoundly transformed the natural environment and the Earth system, leading to the concept of the Anthropocene. This paper summarizes the effects of human activities on the environment in China as recorded in sedimentary archives. China is divided into core and marginal areas based on their natural and societal conditions, and changes in selected proxies for four stages since 2.0 ka are assessed. From 2.0 to 1.0 ka, tree pollen ratios, magnetic susceptibility values, stable organic carbon isotope ratios, and lead concentrations began to deviate from natural baseline (4.0-2.0 ka) values in the core area at different times depending on location. From 1.0 ka to 1950 CE, anthropogenic perturbations recorded by these proxies increased and exhibited regional changes in the core area. From 1950 to1980 CE, total organic carbon contents, stable organic carbon isotope ratios, total nitrogen contents, and stable nitrogen isotope ratios changed significantly in both the core and marginal areas. After 1980 CE, lead concentrations, black carbon and polycyclic aromatic hydrocarbons contents increased rapidly. In the latter two stages, the amounts and chronologies of artificial radionuclides and novel materials in the strata reflect their history of outputs or emissions. The boundaries for each stage correspond with important historical events. At 1.0 ka, the political center of China moved eastward, and a transportation network was established in the core area. In ca. 1950 CE, the People's Republic of China was established and the Global Acceleration began, while 1980 CE corresponds with the Reform and Opening-up of China that led to an accelerated industrialization. Our review shows that transportation networks and industries were key factors for intensification of human activities that caused Earth system to enter the Anthropocene.

The spatial-temporal chemical footprint of pesticides in China from 1999 to 2018

The massive use of pesticides brings considerable environmental and human health impacts. This study conducted an overall assessment of the ecological impact of the extensive pesticide use in China from 1999 to 2018 through the Chemical Footprint (ChF) calculation. The results demonstrated that the primary ecological impacts caused by pesticides occurred in the most central and eastern regions in China, e.g., provinces of Shandong, Henan, Hubei, Anhui, and Jiangsu. The northeastern, some southern and central provinces, e.g., Heilongjiang, Jilin, Liaoning, Yunnan, Guangxi, Guangdong, Ningxia, and Shaanxi, got moderate impacts, whereas the northwest regions, e.g., Qinghai, Xinjiang, and Tibet, had much lighter impacts relatively. The agricultural soil in inland areas and surface sea waters in coastal provinces bore the major impacts of the pesticide pollution in China, shared above 80% of the ChF across all environmental compartments. Chlorpyrifos, pymetrozine, fenpropathrin, pyridaben, atrazine, etc., were the pesticides that had the greatest impacts on the ecosystem, which contributed over 95% of the total ChF of pesticides used in China, although the use amount of these pesticides accounted for less than 10% of the total use amount of all pesticides annually. The study also indicated that the overall ChF of pesticide use in China has been declining since 2010, which was corresponding with the control actions of highly hazardous pesticides, especially the elimination of high toxic organophosphorus insecticides during the past decade.

Modern lake sedimentary record of PAHs and OCPs in a typical karst wetland, south China: Response to human activities and environmental changes

The sedimentary history of polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs) over the past 140 years in a lake sediment core from Huixian karst wetland was reconstructed. The total PAHs and OCPs concentrations ranged from 40.0 to 210 ng g^-1 and 0.98 to 31.4 ng g^-1, respectively. The vertical distribution of PAHs and OCPs in different stages was great consistent with the history of regional socio-economic development and the usage of OCPs. As the indicators of socio-economic development, gross domestic product (GDP), population, energy consumption, highway mileage, and private vehicles correlated with the PAHs concentrations, indicating the impact of human activities on PAHs levels. The PAHs and OCPs concentrations were also affected by environmental changes in the wetland, as reconstructed by total organic carbon (TOC), sand, silt, clay, quartz, and calcite in sediments. Redundancy analysis (RDA) results showed TOC was the dominant factor to explain the concentrations of PAHs and OCPs with the explanation of 86.7% and 43.5%, respectively. In addition, TOC content had significantly positive correlation with PAHs (0.96, p < 0.01) and OCPs (0.78, p < 0.01). In particular, the significantly positive correlation (p < 0.05) between calcite and PAHs and OCPs inferred that karstification might play an important role in the migration of PAHs and OCPs in the karst area. Therefore, the lake in Huixian wetland tended to be a sink more than a source of PAHs and OCPs influenced by the increasing TOC content and karstification under climate warming.

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.

Distribution, sources, and ecological risk assessment of polycyclic aromatic hydrocarbons in the sediments of Daihai Lake in Inner Mongolia, China

Polycyclic aromatic hydrocarbons (PAHs) are typical toxic organic pollutants that can accumulate in sediments and may be toxic to aquatic organisms. In the present study, the contamination level, composition pattern, and sources of sixteen PAHs listed by the United States Environmental Protection Agency were investigated in surface sediments and a sediment core from Daihai Lake, which is located in a typical semiarid area of Inner Mongolia, China, and the ecological risk of these PAHs was assessed. The results show that the total concentration of PAHs in the surface sediments ranged from 204.6 to 344.5 ng/g with an average value of 287.2 ng/g and that compared with other aquatic systems, the level of PAHs in the sediments from Daihai Lake was low. However, a general upward trend was observed for the concentrations of PAHs in the sediment core, which might be related to the increase in human activities in the area. Moreover, the PAH concentrations were significantly positively correlated with the total organic carbon (TOC) content in the sediments, and it is thus inferred that TOC regulates the distribution of PAHs in Daihai Lake. Three-ring and four-ring PAHs were found to be predominant in all the sediment samples, and phenanthrene (Phe) was the most abundant compound. According to the composition of PAHs and the anthracene (Ant)/(Ant+Phe) or fluoranthene (Flt)/(Flt+pyrene (Pyr)) ratios, the PAHs in Daihai Lake mainly originated from the combustion of domestic coal, grass, and wood, and petroleum cannot be ignored as a source considering the growth of industry. Risk assessment based on a comparison of PAH concentrations and the effect range low (ERL) and effect range median (ERM) values demonstrated that acenaphthene (Ace) at 11 sites and fluorene (Flu) at 7 sites had occasional adverse biological effects.

Sediment record of polycyclic aromatic hydrocarbons in Dianchi lake, southwest China: Influence of energy structure changes and economic development

Sixteen polycyclic aromatic hydrocarbons (PAHs) in a sediment core from Dianchi Lake, southwest China, were analysed. The influence of changes in China's energy structure for 2-6 ringed PAHs was investigated to assess sources and the impact of socioeconomic development on temporal changes in concentrations. The concentration of the ΣPAH₁₆ ranged from 746 to 2293 ng g^-1. Prior to the 1960s relatively low concentrations of the ΣPAH₁₆ and a larger proportion of 2-3-ring PAHs indicated that biomass combustion was the main source of PAHs. A rapid increase in the concentrations of 2-3 ring PAHs between 1975 and 2004 was attributed to population growth and coal consumption. A declining trend since 2004 was interpreted as being due to local changes in household energy usage. Increased concentrations of 4-ring PAH between 1975-2005 and 5-6-ring PAHs between the 1980s to 2004 showed correlations with increased coal consumption and the number of motor vehicles, respectively. These were caused by rapid urbanization and industrialization in the Dianchi watershed following the implementation of the Reform and Open Policy in 1978. A subsequent decline in the concentrations of 4-ring and 5-6-ring PAHs may have been due to decreased coal consumption and improvements in emission standards, respectively. Source apportionment by a PMF model revealed that coal combustion (29.2%), vehicle emissions (24.2%), petrogenic sources (21.8%), and biomass combustion (24.9%) were the sources of PAHs in the lake sediment core, and that coal combustion was the most important regional source of PAHs pollution.

Environmental Levels, Sources, and Cancer Risk Assessment of PAHs Associated with PM2.5 and TSP in Monterrey Metropolitan Area

In this work, the content of polycyclic aromatic hydrocarbons (PAHs) in total suspended particles and particulate matter with an aerodynamic diameter ≤ 2.5 µm (PM_2.5) was analyzed using gas chromatography-mass spectrometry. In addition, a sequential chemical analysis of C-rich particles was performed through the parallel coupling of micro-Raman spectroscopy and scanning electron microscopy with X-ray scattering detection. Samples were collected at four sites in the Monterrey metropolitan area, Mexico. A total of 13 PAHs were quantified; indeno(1,2,3-cd)pyrene, chrysene, and benzo(a)anthracene were the most abundant. The total PAH concentrations at the four sampling sites ranged from 1.34 to 8.76 μg/m³. The diagnostic relation of the PAHs indicates that these compounds were emitted by the burning of gasoline and diesel and by the burning of charcoal and biomass. The sequential analysis correlated the morphology and the elemental/molecular composition of the C-rich particles, associated with the PAHs, with their possible emission sources. The estimated lifetime excess cancer risk for inhalation was higher than that established by the World Health Organization, which clearly makes this a potential health risk for the population.

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.

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.

Differences in phytoaccumulation of organic pollutants in freshwater submerged and emergent plants

Plants play an important role as sinks for or indicators of semivolatile organic pollutants, however most studies have focused on terrestrial plants and insufficient information has been obtained on aquatic plants to clarify the accumulation of organic pollutants via air-to-leaf vs. water-to-leaf pathways. The presence of p, p'-dichlorodiphenyldichloroethylene (p, p'-DDE), hexachlorobenzene (HCB), 15 polycyclic aromatic hydrocarbons (PAHs), and 9 substituted PAHs (s-PAHs), including oxy-PAHs and sulfur-PAHs, in 10 submerged and emergent plants collected from Lake Dianchi was analyzed in this study. Relatively low concentrations of p, p'-DDE (ND to 2.22 ng/g wet weight [ww]) and HCB (0.24-0.84 ng/g ww) and high levels of PAHs (46-244 ng/g ww) and s-PAHs (6.0-46.8 ng/g ww) were observed in the aquatic plants. Significantly higher concentrations of most of the compounds were detected in the leaves of the submerged plants than in those of the emergent plants. The percentages of concentration difference relative to the concentrations in the submerged plants were estimated at 55%, 40%, 10%-69% and 0.5%-79% for p, p'-DDE, HCB, PAHs, and s-PAHs, respectively. The percentages were found to increase significantly with an increase in log Kow, suggesting that the high level of phytoaccumulation of pollutants in aquatic plants is due to hydrophobicity-dependent diffusion via the water-to-leaf pathway and the mesophyll morphology of submerged plants.

Ecological Risk Assessment of HCH and DDT Residues in a Sediment Core from the Küçükçekmece Lagoon, Turkey

The residues of organochlorine pesticides (HCHs and DDTs) in a dated (¹³⁷Cs and ²¹⁰Pb) sediment core from the Küçükçekmece Lagoon, an urban lake at the southern entrance of the future Canal Istanbul Project, an artificial watercourse, were analyzed with the gas chromatograph equipped with electron capture detector (GC ⁶³Ni-ECD). Concentrations of ∑HCH and ∑DDT along the core varied between 0.4 and 469.4 (average 51.4) ng g^-1 dw, and between 0.5 and 72.0 (average 7.4) ng g^-1 dw, respectively. α-HCH was the predominant isomer (98%) and followed by γ-isomer (2%). The highest concentrations of technical HCH were found in the sediments dated 1963-1972, whilst the DDT concentrations had their maximum around 1945. The highest concentrations of γ-HCH and p,p'-DDT exceeded probable-effect level values which can lead to frequently cause adverse effects on aquatic biota.

Historical Records and Source Apportionment of Polycyclic Aromatic Hydrocarbons Over the Past 100 Years in Dianchi Lake, a Plateau Lake in Southwest China

Two sediment cores were collected from Dianchi Lake, a plateau lake in Southwest China, to study the temporal trends and to investigate the sources of sedimentary deposited polycyclic aromatic hydrocarbon. The ΣPAH16 concentration in the two sediment cores ranged from 172.5 to 2244.8 ng/g and from 211.4 to 1777.8 ng/g, with mean values of 1106.2 and 865.1 ng/g, respectively. Three temporal trends for the ΣPAH16 concentration and the composition of PAHs in Dianchi Lake all showed three typical changing stages: (1) slight changes in deeper segments before the 1950s; (2) a rapid increase in PAH concentrations between the 1960s and 1990s; and (3) a slight reduction from the 1990s onward. These trends differ from those observed in developed countries due to differences in the timing of industrialization and urbanization processes. According to the results of the molecular ratios and principal component analysis, the PAH deposition was dominated by coal combustion, wood combustion, and vehicle emissions before and after the 1960s, respectively.

Analysis of Historical Sources of Heavy Metals in Lake Taihu Based on the Positive Matrix Factorization Model

Analysis of sediment grain sizes and heavy metal correlations in the western part of Lake Taihu shows that the grain size of the sediment is stable as a whole. With increasing depth, the grain size tends to decrease. Heavy metals such as Cr, Cd, Pd and Sr are strongly correlated and influence each other. Based on the positive matrix factorization (PMF) model, this study classified the origin of heavy metals in the sediments of western Lake Taihu into three major categories: Agricultural, industrial and geogenic. The contributions of the three heavy metal sources in each sample were analyzed and calculated. Overall, prior to the Chinese economic reform, the study area mainly practiced agriculture. The sources of heavy metals in the sediments were mostly of agricultural and geogenic origin, and remained relatively stable with contribution rates of 44.07 ± 11.84% (n = 30) and 35.67 ± 11.70% (n = 30), respectively. After the reform and opening up of China, as the economy experienced rapid development, industry and agriculture became the main sources of heavy metals in sediments, accounting for 56.99 ± 15.73% (n = 15) and 31.22 ± 14.31% (n = 15), respectively. The PMF model is convenient and efficient, and a good method to determine the origin of heavy metals in sediments.

Sediment evidence of industrial leakage-induced asynchronous changes in polycyclic aromatic hydrocarbons and trace metals from a sub-trophic lake, southwest China

It has been well established that regional patterns of atmosphere-borne polycyclic aromatic hydrocarbons (PAHs) and trace metals were predominantly associated with the trajectory of socio-economic development; however, they could be potentially modulated by anthropogenic fingerprint of local sources such as industrial spill. Here, we established historical pollution data of both PAHs and trace metals from a well-dated sediment core from Yangzong Lake of Southwest China, which experienced a severe tailing leakage accident derived from a zinc concentrate smelting plant in 2007, aiming to evaluate the heterogeneity in their temporal trajectories and their sources of contamination in the context of regional deposition patterns. Sedimentary records show that the concentrations and fluxes of both PAHs and trace metals remained a consistently low level before the 1950s. An increasing trend and the synchronous changes of both PAHs and trace metals during ~ 1950-2002 were well consistent with the temporal pattern of socio-economic development in western China, with coal combustion and smelting industries as the main sources of contamination in this region. However, arsenic (As) and PAHs exhibited a concurrent spike for the period of ~ 2007-2013, contrasting strongly to the regional pattern of these contaminants. The modern concentrations of As revealed a 5- to 14-fold increase over the pre-1950 level, with the contemporary concentrations of PAHs rising by ~ 10-14 times. The sediment records reveal that local fingerprints of smelting activities in the catchment of Yangzong Lake have overridden the temporary pattern of regional atmosphere-borne As and PAHs over the last decade. This highlights the important role of local pollution sources in modulating or even overriding the regional pattern of anthropogenic contamination in highly impacted systems.

Trophodynamics of Organic Pollutants in Pelagic and Benthic Food Webs of Lake Dianchi: Importance of Ingested Sediment As Uptake Route

Habitat is of great importance in determining the trophic transfer of pollutants in freshwater ecosystems; however, the major factors influencing chemical trophodynamics in pelagic and benthic food webs remain unclear. This study investigated the levels of p,p'-dichlorodiphenyldichloroethylene (p,p'-DDE), polycyclic aromatic hydrocarbons (PAHs), and substituted PAHs (s-PAHs) in 2 plankton species, 6 invertebrate species, and 10 fish species collected from Lake Dianchi in southern China. Relatively high concentrations of PAHs and s-PAHs were detected with total concentrations of 11.4-1400 ng/g wet weight (ww) and 5.3-115 ng/g ww, respectively. Stable isotope analysis and stomach content analysis were applied to quantitatively determine the trophic level of individual organisms and discriminate between pelagic and benthic pathways, and the trophodynamics of the detected compounds in the two food webs were assessed. P,p'-DDE was found to exhibit relatively higher trophic magnification rate in the pelagic food web than in the benthic food web. In contrast, PAHs and s-PAHs exhibited greater dilution rates along the trophic levels in the pelagic food web. The lower species differences of pollutants accumulated in benthic organisms compared to pelagic organisms is attributable to extra uptake via ingested sediment in benthos. The average uptake proportions of PAHs and s-PAHs via ingested sediment in benthic biotas were estimated to be 31-77%, and that of p,p'-DDE was 46%. The uptake routes are of importance for assessing the trophic magnification potentials of organic pollutants, especially in eutrophic freshwater ecosystems.

Historical Trends of Polycyclic Aromatic Hydrocarbons in the Reservoir Sediment of the Dianchi Watershed, Southwest China

Using gas-chromatography/mass spectrometry (GC-MS) method dating data (²¹⁰Pb and ¹³⁷Cs) and OCPs signatures, the temporal distribution of polycyclic aromatic hydrocarbons (PAHs) was investigated in dated sediment core from Baoxianghe reservoir in Dianchi watershed, Southwest China. The concentrations of total PAHs were in the range of 162.3-762.2 ng g^-1 from 1945 to 2013. There showed an obvious increase from 1960s to 2000s. The distributions of PAHs were influenced by local population and Gross Domestic Product (GDP) during the period between1962 and 2004. PAHs sources changed from biomass or domestic coal combustion (before 1980) to liquid fossil fuel combustion (after 1980). Total toxic toxicity equivalents (TEQs) of the carcinogenic PAHs were very low (3.03-28.08 ng g^-1).

Bound PAHs in Sediment and Related Environmental Significance

Extractable polycyclic aromatic hydrocarbons (EPAHs) and bound PAHs (BPAHs) were measured in a sediment core using conventional Soxhlet extraction and a more astringent extraction method, with the objectives of determining the influence of BPAHs on the historical reconstruction of PAHs and exploring the formation of BPAHs and long-term behaviors of PAHs in sediment. The results indicated that the formation of BPAHs was clearly sediment-depth and molecular-size dependent. BPAHs represents an important portion of PAHs in sediment and cannot be extracted by conventional Soxhlet extraction. This suggests that the previously developed vertical profile of PAHs is not the real chronology of PAHs and the plausible interpretation derived from the sedimentary records of PAHs needs reexamination. Based on the previous findings, a biphase model was proposed and the formation of BPAHs was predicted. Due to the different nature of geosorbents in sediment, redistribution of PAHs among these geosorbents logically leads to the formation of BPAHs and is kinetically favorable for smaller molecular PAHs. This is consistent with the obtained results. Many factors may influence the formation of BPAHs, such as the physicochemical structure of sediment and environmental conditions. There is still a long way to reveal the thermodynamical characteristics in action during the formation of BPAHs.

Historical records and sources of polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs) in sediment from a representative plateau lake, China

The PAH and OCP concentrations in sediment cores collected from a deep lake were measured and evaluated chronologically. The results indicated that the PAH and OCP concentrations significantly increased from the 1950s to the 1990s and subsequently decreased to recent years. Integrated molecular diagnostic ratios indicated that the predominant petrogenic sources occurred from the 1950s-1980s. Petroleum and fuel combustion dominated the source of contamination more recently as a result of energy structure changes in this region. Additionally, HCHs and DDTs were the dominant OCP compounds, making up a majority of the total OCPs present (>85%). HCHs accounted for a larger ratio of the OCPs between the 1950s and 1980s, suggesting that HCHs were the dominant POPs in this period. DDTs then became dominant in the 1980s and later. High α/γ-HCH ratios suggested that the emission and conversion of local technical HCHs were the predominant HCHs source. The ratios of (DDE + p,p'-DDD)/DDTs and p,p'-DDT/DDTs indicated that the DDTs mainly originated from historical input. In addition, the dramatic decrease since the 1980s may be the result of China's banning of DDTs. However, DDTs were still present in the 1990s, suggesting DDTs were still used in this region and beyond.

Sedimentary Record of Polycyclic Aromatic Hydrocarbons from the Shuanglong Catchment, Southwest China

Polycyclic aromatic hydrocarbons (PAHs) in the dated sediments from the Shuanglong catchment in the southwest of China were measured to characterize source inputs. The PAHs concentrations in the priority controlling list of US EPA (∑PAHs) ranged within 102.47~563.24 ng g−1, with an average value of 207.18 ng g−1. The 2-3 rings PAHs were predominant, accounting for 73.77% of ∑PAH. According to the classification of pollution levels, ∑PAHs concentrations in the sediments are within the range of moderate pollution level. Both the total and individual PAH concentrations changed with the depth. The profile distribution of PAHs concentration in the sediments suggested that PAHs acted as an effective way to reconstruct the historical trends of socioeconomic changes in the study areas. Results of Ant/(Ant + Phe), Fla/(Fla + Pyr), and BaA/(BaA + Chry) show that petroleum and petrogenic matter are attributed to the potential pollution source in the Shuanglong catchment. The coal combustion and incomplete combustion of gasoline and fossil fuel are dominant. TOC contents had positive correlation with ∑PAHs (R2=0.72, P<0.001), 2-3 rings (R2=0.44, P<0.001), 4-ring (R2=0.78, P<0.001), and 5-6 rings (R2=0.62, P<0.001).

Insecticides in sediment cores from a rural and a suburban area in South China: A reflection of shift in application patterns

A shift in pesticide application pattern has occurred in recent decades, yet little information is available in the consequence of this shift. To better understand how the shift is reflected in aquatic environment, two sediment cores were collected from a rural (RLY) and a suburban (SGZ) river in South China. A variety of legacy organochlorine pesticides (OCPs) and current-use pesticides (CUPs), including organophosphate, pyrethroid and phenylpyrazole insecticides were quantified at distinct increments of the sediment cores. Total insecticide concentrations were in the ranges of 67.6-1671 and 99.2-231ng/g dry weight in RLY and SGZ with pyrethroids and organochlorines being the dominant components, respectively. In general, the shifting profile of sediment-bound insecticides from legacy OCPs to CUPs over time followed their historical application pattern, but significant differences were noted between the temporal profiles of the rural and suburban cores in regards to concentrations and composition of insecticides. The observed difference between the suburban and rural cores was synchronous with land use pattern and local economic changes. A steep increased occurrence of CUPs in the 1990s was observed in the RLY core, which is consistent with the onset of economic growth in this area. In contrast, the suburban SGZ area has been historically contaminated by legacy OCPs, with fresh input of OCPs in SGZ believed to be caused by soil erosion, caused by land reclamation activities associated with urban expansion. The current study shows the shift in insecticide application pattern from legacy OCPs to CUPs leading to an elevated CUP occurrence in the environment. It also suggests a stronger need for understanding not only environmental fate and risk, but also how their use pattern and land use changes impact the occurrence of pesticides.

Sources appointment and ecological risk assessment of polycyclic aromatic hydrocarbons (PAHs) in sediments of Erhai Lake, a low-latitude and high-altitude lake in southwest China

Sixteen polycyclic aromatic hydrocarbons (PAHs) were analyzed from the surficial sediments in Erhai Lake, a plateau lake in China. The results showed that except for acenaphthylene (Ace) Ace and Dibenz(a,h)anthracene (DBA), the central region contained individual PAHs at concentrations lower than those in other lake regions. Total concentration of the PAHs (ΣPAHs) in the sediments from Erhai Lake ranged from 32.42 to 558.53 mg/kg with a mean value of 256.70 mg/kg. The maximum value of ΣPAHs was observed in the north region of the lake and more than 10-fold higher than the minimum values. Moreover, high molecular weight (HMW) PAHs, especially 5-ring PAHs, accounted for higher ratios up to 76 % relative to other PAHs compound in almost all sampling sites. Molecular diagnostic ratios including anthtacene (Ant)/(Ant + phenanthrene (Phe)), fluoranthene (Flt)/(Flt + pyrene (Pyr)), benz(a)anthracene (BaA)/(BaA + chrysene (Chr)), and indeno(1,2,3-cd)pyrene (IPY)/(IPY + benz(g,h,i)perylene (BPE)) were recorded at all sampling sites and indicated that the origin of PAHs in Erhai Lake was predominately pyrolytic. Furthermore, principal component analysis with component dominating by HMW PAHs showed that combustion origins were the primary contamination sources of PAHs in the sediments of Erhai Lake. Finally, ecological risk assessment indicated that the sediments from Erhai Lake are exposed to potential low risk for ΣPAHs, and the ecological risk decreases in the order of northern region > southern region > central region.

Spatial and temporal distribution and sources of polycyclic aromatic hydrocarbons in sediments of Taihu Lake, eastern China

Spatial and temporal distributions of concentrations of polycyclic aromatic hydrocarbons (PAHs) in surface sediments and dated sediment core from Taihu Lake in eastern China were determined. The sum of concentrations of PAHs (sum of total 16 USEPA priority PAH (∑PAHs)) of the entire Taihu Lake ranged from 2.9 × 10(2) to 8.4 × 10(2) ng/g dry mass (dm). Concentrations of ∑PAHs in surface sediments near more urbanized regions of the lake shore were greater than those in areas more remote from the urban centers. Temporal trends in concentrations of ∑PAHs ranged from 5.1 × 10(2) to 1.5 × 10(3) ng/g dm, increasing from deeper layers to surface sediments with some fluctuations, especially in the past three decades after the inception of China's Reform and Opening Up Policy, in which China's economy and urbanization underwent rapid development. Forensic analysis of surface sediments indicates that PAHs originated primarily from combustion of grass/wood/coal except for the special function water area, which was most likely influenced by petroleum products of traveling vessels. Vertical profiles of relative concentrations of PAHs suggested that the contribution of lesser-molecular-weight PAHs was gradually decreasing, while due to the heavier consumption of petroleum products, the proportion of greater-molecular-weight PAHs was increasing. When assessed by use of the rather conservative, apparent effect threshold method, concentrations of ∑PAHs in sediments from most locations in Taihu Lake are predicted to pose little risk of harm to benthic invertebrates.

PAHs in sediment cores at main river estuaries of Chaohu Lake: implication for the change of local anthropogenic activities

In the present study, 28 polycyclic aromatic hydrocarbons (PAHs) were investigated in four sediment cores collected from the main river estuaries of Chaohu Lake, one of the severely polluted lakes in China. The results indicate that elevated concentrations of total PAHs (Σ28PAH) were found in the samples from the estuary of Nanfei River (ENF), considering BaP-based total toxicity equivalent (TEQ-BaP) and toxic unit (TU) results; there are potential adverse environmental implications. The total organic carbon (TOC) played an important role on the accumulation of PAHs at ENF and the estuary of Tongyang River (ETY). The predominant PAHs are high molecular weight (HMW) homologous for all samples; as a result, industrial wastewater from a steel company is expectedly the key source of PAHs in ENF, while coke consumption would be the important source of PAHs at other three sampling sites. Vertical distribution of PAHs in the sediment cores could be explained by the local social and economic activities. Furthermore, a minor variation of PAH composition in the sediment core could be justified by the stable structure of energy consumption in the Anhui Province. These results justify the need for further enhancement of industrial wastewater treatment and development of renewable energies which are the key factors on the control of PAH pollution in China.

Analysis of HCHs and DDTs in a sediment core from the Old Yellow River Estuary, China

The present study analyzed the distribution of HCHs and DDTs in a sediment core from the Old Yellow River Estuary, China. The OCP levels were detected by Soxhlet extraction followed by gas chromatography (GC) using a mass-selective detector. Sediment age was analyzed for (210)Pb using an Ortec GWL HPGe gamma spectrometer. The results indicated that the concentrations of ∑DDT in the sediment core were much lower than those of ∑HCH. Compared with the other estuarine and coastal regions in Chinese rivers, HCHs levels in this area were higher or similar, while DDTs levels were lower. The compositional analysis indicated that β-HCH and p, p'-DDD were the predominant species. The temporal trends indicated that levels of HCHs and DDTs were related with their historical usage, emission and soil residues. According to the analysis of the ratio, HCHs in this area was mainly due to the technical historical residue and recent lindane. DDTs was mainly due to historical residue. The biodegradation conditions for DDTs were anaerobic. The dicofol-type DDTs application occurred in this area.