Sources and spatial distribution of polycyclic aromatic hydrocarbons in coastal sediments of the Basque Country (Bay of Biscay)

This contribution characterises the sources and distribution of polycyclic aromatic hydrocarbons (PAHs) in sediments of the Basque coast (Bay of Biscay). Different source characterisation approaches (i.e. GIS assisted-chemometrics, PAH diagnostic ratios and analyses of composition profiles) were used in combination to successfully identify the factors determining the origin and distribution of PAHs. Urban/industrial combustion processes were identified as the main PAH source. However, the analysis of PAH composition patterns and diagnostic ratios identified secondary natural and petrogenic PAH sources on small spatial scales. The median ∑18PAH concentration ranged from 66 μg kg^?1 (d.w.) to 7021 μg kg^?1 (d.w.). The Ibaizabal estuary, which supports most of the anthropogenic pressure in the region (i.e. urban development, industrialisation, commercial and recreational harbours), also showed the highest PAH concentrations. On the shelf, human activities, hydrodynamic conditions and geomorphological features led to spatial differences in the PAH concentrations among sectors: the offshore and west sectors were characterised by higher concentrations, while the lowest values were found in the mid and east sectors. The results enhance the knowledge on PAH-related contamination processes and could be used to support the environmental assessment process required under current European marine legislation.     

Promoting the use of BaP as a marker for PAH exposure in UK soils

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous environmental pollutants that frequently accumulate in soils. There is therefore a requirement to determine their levels in contaminated environments for the purposes of determining impacts on human health. PAHs are a suite of individual chemicals, and there is an ongoing debate as to the most appropriate method for assessing the risk to humans from them. Two methods predominate: the surrogate marker approach and the toxic equivalency factor. The former assumes that all chemicals in a mixture have an equivalent toxicity. The toxic equivalency approach estimates the potency of individual chemicals relative to the usually most toxic Benzo(a)pyrene. The surrogate marker approach is believed to overestimate risk and the toxic equivalency factor to underestimate risk. When analysing the risks from soils, the surrogate marker approach is preferred due to its simplicity, but there are concerns because of the potential diversity of the PAH profile across the range of impacted soils. Using two independent data sets containing soils from 274 sites across a diverse range of locations, statistical analysis was undertaken to determine the differences in the composition of carcinogenic PAH between site locations, for example, rural versus industrial. Following principal components analysis, distinct population differences were not seen between site locations in spite of large differences in the total PAH burden between individual sites. Using all data, highly significant correlations were seen between BaP and other carcinogenic PAH with the majority of r ² values > 0.8. Correlations with the European Food Standards Agency (EFSA) summed groups, that is, EFSA2, EFSA4 and EFSA8 had even higher correlations (r ² > 0.95). We therefore conclude that BaP is a suitable surrogate marker to represent mixtures of PAH in soil during risk assessments.     

Comprehensive characterization of PAHs profile in Serbian soils for conventional and organic production: potential sources and risk assessment

This study presents a comprehensive characterization of occurrence and levels of 16 polycyclic aromatic hydrocarbons (PAHs) in arable soils used for conventional and organic production in northern and central part of Serbia as well as cross-border region with Hungary. Furthermore, this study includes a characterization of PAH sources and carcinogenic/non-carcinogenic human health risk for PAHs accumulated in analysed arable soils. The total concentration of 16 PAHs varied between 55 and 4584 µg kg^?1 in agricultural soil used for conventional production and between 90 and 523 µg kg^?1 in agricultural soil used for organic production. High molecular weight (HMW) PAHs were dominant compounds with similar contribution in both soil types (86% and 80% in conventional and in organic soil, respectively). Principal component analysis and diagnostic ratios of selected PAHs were used for identification of PAH sources in the analysed soils. Additionally, positive matrix factorization was applied for quantitative assessment. The results indicated that the major sources of PAHs were vehicle emissions, biomass and wood combustion, accounting for?~?93% of PAHs. Exposure of farmers assessed through carcinogenic (TCR) and non-carcinogenic (THQ) risk did not exceed the acceptable threshold (TCR?<?10^–6 and THQ?<?1). Oral ingestion was the main exposure route which accounted for 57% of TCR and 80% of THQ. It was followed by dermal contact. This investigation gives a valuable data insight into the PAHs presence in arable soils and reveals the absence of environmental and health risk. It also acknowledges the importance of comprehensive monitoring of these persistent pollutants.

     

Spatial distribution of PAHs in a contaminated valley in Southeast China

A survey was conducted on the accumulation and spatial distribution of PAHs in surface soils under different land use patterns in a valley in the Yangtze Delta region with an area of 10 km² containing 15 small copper- and zinc-smelting furnaces. Sixty-five topsoil (0–20 cm) samples were collected and 16 PAHs were determined. The average amount of all the 16 PAHs ranged from 0 to 530 μg kg⁻¹ (oven dry basis), with a mean concentration of 33.2 μg kg⁻¹. Benzo[a]pyrene and indeno[1, 2, 3, -cd]pyrene were the two main PAHs present at high concentrations, while pyrene and fluorene had very low concentrations. PAH concentrations were higher in uncultivated than in cultivated soils, and areas of woods and shrubbery had the␣lowest soil PAH contents. The average PAH-homologue concentrations ranked as follows: 5-rings >> 3-rings, 4-rings > 6-rings >2-rings. Much higher concentrations of PAHs were found in the southern part of the sampling area, perhaps due to deposition of airborne particles by the southeasterly winds in winter and spring. We conclude that the small smelting furnaces were the dominant source of PAHs that accumulated in the soils and the southeasterly winds led to the spatial distribution of PAHs in the topsoils. Land vegetation cover and soil utilization patterns also affected the accumulation and distribution of soil PAHs.     

Effects of hydroxypropyl-β-cyclodextrin on pyrene and benzo[α]pyrene: bioavailability and degradation in sotil

Effect of hydroxypropyl-β-cyclodextrin (HPCD) on the bioavailability and biodegradation of the polycyclic aromatic hydrocarbons (PAHs) pyrene (PYR) and benzo[α]pyrene (BaP) in spiked soils was investigated in 14-week incubation experiments. To evaluate the effect of HPCD in soils with a different matrix, humic substance (HS) was added into soil samples. A 6-h Tenax TA extraction method was used to evaluate pollutants bioavailability. The biodegraded and extracted fractions were compared to evaluate the impact of HPCD on PAHs biodegradation. Results indicated positive effects of HPCD on fast desorption behaviours of PAHs. The biodegraded fraction was consistent with that of the extracted for PYR. However, in terms of BaP, the results were contrary which suggests that biological factors may be limiting factors for BaP pollution remediation. HS weakened the HPCD solubilisation effect while accelerated the decay of PYR and BaP, also implying that bioavailability was not the sole factor limiting PAH biodegradation. In addition, analysis of microbial communities demonstrated that HPCD inhibited the growth of some soil bacteria while HS promoted the evolution of some soil microorganisms. A limited population of hydrocarbon degrader populations led to observing incomplete PAH biodegradation even in the presence of HPCD.     

桑园土壤微生物群落功能多样性对PAHs污染的响应

为了探明桑园土壤微生物群落功能多样性与多环芳烃(PAHs)污染的关系,采用Biolog检测法研究某路域桑园土壤微生物功能多样性对PAHs污染的响应。结果表明,不同区域PAHs污染程度由大到小依次为区域2(位于区域1和3之间)、3(离公路最远)和1(离公路最近);Biolog分析发现不同区域土壤微生物对碳源利用的平均颜色变化率(AWCD)由大到小依次为区域2、3和1;区域2的Shannon指数和Gini指数均显著高于区域1和3,而区域1的Shannon均匀度显著低于区域2和3,区域2土壤微生物活性最强且群落结构最丰富,其后依次为区域3和1。主成分分析结果显示,3个区域微生物群落的生理功能差异明显,主要表现在对糖类和氨基酸类物质的代谢上。冗余分析表明,区域2土壤微生物与PAHs含量关系最密切,说明较高的PAHs含量更能激发桑园土壤微生物的生理活性,微生物群落代谢功能因PAHs污染而有所提高。     

固定化毛霉对工业和农田污染土壤中多环芳烃的降解和生物有效性评价

为了探讨微生物修复不同类型多环芳烃污染土壤的可行性,应用固定化毛霉对多环芳烃污染工业土壤及农田土壤进行微生物修复,用羟丙基-β-环糊精(HPCD)提取模拟评价多环芳烃的微生物可利用性,并分析多环芳烃微生物降解和生物可利用性的相关关系.焦化厂污染土壤中多环芳烃的30 d降解率为77.6%,沈抚灌区污染土壤中多环芳烃的30 d降解率为54.2%,焦化厂土壤和污灌区农田土壤中多环芳烃降解差异明显.焦化厂土壤和污灌区土壤中多环芳烃的30 d降解量和多环芳烃的环糊精可提取量具有相关性,各环数多环芳烃的环糊精可提取量变化解释了焦化厂和污灌区土壤中多环芳烃降解的差异机制,说明可用环糊精提取量预测微生物降解土壤多环芳烃的情况.     

Lichens reveal air PAH fractionation in the Himalaya

This paper shows that gas/particulate phase partitioning of polycyclic aromatic hydrocarbons (PAHs) can be monitored using lichens. Anthropogenic sources are responsible for the release of PAHs, which are bioaccumulated in plants at various spatial scales based on their physicochemical properties. Atmospheric PAHs are distributed both in the gaseous and particulate states. Here, a lichen species, Dermatocarpon vellereum Zschacke, has been collected at different altitudes in and around the Rudraprayag valley, located in Central Himalayan region of India, in order to study the spatial distribution of PAHs in the valley. Results show that PAH concentration ranged from 0.136 to 4.96 μg g^?1. Findings reveal that the bioaccumulation of 2- and 3-ringed PAHs was higher in high-altitude samples, whereas bioaccumulation of fluoranthene, a 4-ringed PAH, showed higher concentration in samples from localities away from town centre. 5- and 6-ring PAHs were then confined to the lower altitude at the base of the valley, thus justifying their particulate-bound nature. This is the first report showing the utility of lichen to biomonitor PAHs in the Himalayan ecosystem.     

Unexpected similar stability of soil microbial CO2 respiration in 20-year manured and in unmanured tropical soils

Soil respiration is one of the main CO₂ sources from terrestrial ecosystems. Soil respiration is therefore a major source of greenhouse gas. Knowledge of the impact of agronomic practices such as manuring on the stability, for example resistance and resilience, of heterotrophic C–CO₂ respiration to disturbance is scarce. Here, we studied the stability of soil microbial heterotrophic respiration of two tropical soils from plots annually enriched or not with manure applications during more than 20 years. Stability was quantified after heating soils artificially. We hypothesized that field manuring would change the stability of the microbial community. Additionally, the impact of both manured and unmanured soils to addition of an organic cocktail was assessed under controlled conditions in order to discriminate the metabolic capacity of the microbial community, and to link the metabolic capacity up with the microbial heterotrophic soil respiration. Our results show that total respiration was not significantly different in manured and unmanured pots. Moreover, contrary to our hypothesis, manure amendment did not affect the stability (resistance, resilience) of the microbial abundance or the basal metabolism, in our experimental conditions. By contrast, the diversity of the bacterial community in heated soils was different from that in unheated soils. After heating, surviving microorganisms showed different carbon utilization efficiency, manuring stimulating the growth of different resistant communities, that is, r-strategist or K-strategist. Microbial community of manured soils developed in the presence of the organic cocktail was less resistant to heating than microbial community of unmanured plots.     

Distribution,source apportionment and health risk assessment of polycyclic aromatic hydrocarbons (PAHs) in intertidal sediment of Asaluyeh,Persian Gulf

Surface sediment samples were collected from intertidal zone of Asaluyeh, Persian Gulf, to investigate distribution, sources and health risk of sixteen polycyclic aromatic hydrocarbons (PAHs). Total PAH concentrations ranged from 1.8 to 81.2 μg kg^?1 dry weight, which can be categorized as low level of pollution. Qualitative and quantitative assessments showed that PAHs originated from both petrogenic and pyrogenic sources with slight pyrogenic dominance. Source apportionment using principal component analysis indicated that the main sources of PAHs were fossil fuel combustion (33.59%), traffic-related PAHs (32.77%), biomass and coal combustion (18.54%) and petrogenic PAHs (9.31%). According to the results from the sediment quality guidelines, mean effects range-median quotient (M-ERM-Q) and benzo[a]pyrene toxic equivalents (BaP_eq), low negative ecological risks related to PAH compounds would occur in the intertidal zone of Asaluyeh. The total benzo[a]pyrene (BaP) toxic equivalent quotient (TEQ^carc) for carcinogenic compounds ranged from 0.01 to 7 μg kg^?1-BaP_eq, indicating low carcinogenic risk. The human health risk assessment of PAH compounds via ingestion and dermal pathways suggests low and moderate potential risk to human health, respectively.     

Distribution pattern of polycyclic aromatic hydrocarbons in particle-size fractions of coking plant soils from different depth

The concentrations of 16 priority polycyclic aromatic hydrocarbons (PAHs) in four size fractions (<2, 2–20, 20–200, >200 μm) in soils at different depth from a heavily contaminated crude benzol production facility of a coking plant were determined using GC–MS. Vertically, elevated total PAHs concentrations were observed in the soils at 3.0–4.5 m (layer B) and 6.0–7.5 m (layer C), relatively lower at 1.5–3.0 m (layer A) and 10.5–12.0 m (layer D). At all sampling sites, the silt (2–20 μm) contained the highest PAHs concentration (ranged from 726 to 2,711 mg/kg). Despite the substantial change in PAHs concentrations in soils with different particle sizes and lithologies, PAHs composition was similarly dominated by 2–3 ring species (86.5–98.3 %), including acenaphthene, fluorene, and phenanthrene. For the contribution of PAHs mass in each fraction to the bulk soil, the 20–200 μm size fraction had the greatest accumulation of PAHs in loamy sand layers at 1.0–7.5 m, increasing with depth; while in deeper sand layer at 10.5–12.0 m, the >200 μm size fraction showed highest percentages and contributed 81 % of total PAHs mass. For individual PAH distribution, the 2–3 ring PAHs were highly concentrated in the small size fraction (<2 and 2–20 μm); the 4–6 ring PAHs showed the highest concentrations in the 2–20 μm size fraction, increasing with depth. The distribution of PAHs was primarily determined by the sorption on soil organic matter and the characteristics of PAHs. This research should have significant contribution to PAH migration study and remediation design for PAHs-contaminated sites.     

Ecological risks of polycyclic aromatic hydrocarbons found in coastal sediments along the northern shores of the Bohai Sea (China)

The total concentrations of 16 United States Environmental Protection Agency (US EPA)-listed polycyclic aromatic hydrocarbons (PAHs) found in coastal and estuarine sediments along the northern shores of the Bohai and Yellow Seas, China, at any study location varied from 0.236 to 8.34 nM g^?1 dry weight (dw). For a given PAH, concentrations varied by one to two orders of magnitude. Ecological risk assessments based on biota–sediment accumulation factors (BSAFs) indicated that the potential ecological hazard of PAHs in the sediments was limited. The average total sediment PAH concentrations were less than the effects range low, indicating that PAHs currently present in the sediments were not harmful to aquatic organisms. The estimated PAH concentration in the aquatic organisms was 0.223 nM g^?1 and posed a limited threat to human health via biological concentration from sediment to harvest of the sea. Assuming no additional PAH inputs, 99% of the 16 PAH molecules currently present in the sediments would be degraded in 40 years.     

Biomarkers indicate mixture toxicities of fluorene and phenanthrene with endosulfan toward earthworm (<Emphasis Type="Italic">Eisenia fetida</Emphasis>)

α-Endosulfan and some polycyclic aromatic compounds (PAHs) are persistent in the environment and can reach crop products via contaminated agricultural soils. They may even be present as mixtures in the soil and induce mixture toxicity in soil organisms such as earthworms. In this study, the combined toxicities of PAHs with α-endosulfan were determined in Eisenia fetida adults using an artificial soil system. α-Endosulfan and five PAHs were tested for their acute toxicity toward E. fetida in artificial soils. Only α-endosulfan, fluorene, and phenanthrene showed acute toxicities, with LC₅₀ values of 9.7, 133.2, and 86.2 mg kg^?1, respectively. A mixture toxicity assay was conducted using α-endosulfan at LC₁₀ and fluorene or phenanthrene at LC₅₀ in the artificial soils. Upon exposure to the mixture of fluorene and α-endosulfan, earthworms were killed in increasing numbers owing to their synergistic effects, while no other mixture showed any additional toxicity toward the earthworms. Along with the acute toxicity results, the biochemical and molecular changes in the fluorene- and phenanthrene-treated earthworms with or without α-endosulfan treatment demonstrated that enhancement of glutathione S-transferase activity was dependent on the addition of PAH chemicals, and the HSP70 gene expression increased with the addition of α-endosulfan. Taken together, these findings contribute toward understanding the adverse effects of pollutants when present separately or in combination with other types of chemicals.     

Characterization and sources of PAHs in an urban river system in Beijing,China

Water samples from 20 locations on rivers in the Tongzhou District of Beijing were collected four times from July 2005 to March 2006. In addition, sediment samples were collected in July 2005. All samples were analyzed for 16 US Environmental Protection Agency (EPA) priority pollutants polycyclic aromatic hydrocarbons (PAHs). The concentration, distribution, seasonal variation, and sources of the 16 PAH compounds identified in the water samples, suspended particles, and surface sediments were then evaluated. The concentrations of PAHs in the water and suspended particle and surface sediment samples ranged from 87.3 to 1,890 ng l⁻¹, 1,330 to 27,700 ng g⁻¹, and 156 to 8,650 ng g⁻¹, respectively. These results demonstrated that rivers in the Tongzhou District of Beijing had a high level of PAH pollution, especially in the suspended particles. The highest and lowest concentrations of PAHs in the water samples were observed in summer and spring. However, the seasonal variations in the concentration of PAHs in the suspended particles were more complicated. The dominant compounds in the water, suspended particle, and surface sediment samples were two-, three- and four-ring PAH compounds, respectively. Ratio analysis illustrated that fuel-burning was the primary source of PAHs in the study area. Gasoline, diesel, coal, and coke oven sources were identified and the contributions of the different fuel-burning sources were then calculated using factor analysis and multiple linear regression. These analyses revealed that coal combustion, gasoline combustion plus coke oven emission, and diesel combustion accounted for 38.8%, 38.5%, and 22.7% of the PAHs in suspended particles, respectively.     

Historical record of anthropogenic polycyclic aromatic hydrocarbons in a lake sediment from the southern Tibetan Plateau

High-altitude lake sediments can be used as natural archives to reconstruct the history of pollutants. In this work, the temporal distribution of polycyclic aromatic hydrocarbons (PAHs) was determined in a sediment core collected from the southern Tibetan Plateau (TP), which was dated by using the ²¹⁰Pb dating method and validated with the ¹³⁷Cs fallout peak. The concentrations of the anthropogenic PAHs (Σ₈PAH) in the sediment core ranged from 0.83 to 12 ng/g dw, and the fluxes of the Σ₈PAH were in the range of 2.1–27 g/cm²/year. The temporal variations in the concentration and input flux of anthropogenic PAHs were low with little variability before the 1950s, and then gradually increased from the 1950s to the 1980s, and an accelerated increase was observed after the early 1980s. The content of total organic carbon played an insignificant role in affecting the time trends of PAHs in the sediment core. Diagnostic concentration fractions of PAH components indicate PAHs in the lake sediment of the southern TP which are mainly from biomass burning and/or from long-range atmospheric transport.     

Removal of high concentrations of polycyclic aromatic hydrocarbons from contaminated soil by biodiesel

Solubilizing experiments were carried out to evaluate the ability of biodiesel to remove polycyclic aromatic hydrocarbons (PAHs) from highly contaminated manufactured gas plant (MGP) and PAHs spiked soils with hydroxypropyl-β-cyclodextrin (HPCD) and tween 80 as comparisons. Biodiesel displayed the highest solubilities of phenanthrene (420.7 mg·L^-1), pyrene (541.0 mg·L^-1), and benzo(a)pyrene (436.3 mg·L^-1). These corresponded to several fold increases relative to 10% HPCD and tween 80. Biodiesel showed a good efficiency for PAH removal from the spiked and MGP soils for both low molecular weight and high molecular weight PAHs at high concentrations. Biodiesel was the best agent for PAH removal from the spiked soils as compared with HPCD and tween 80; as over 77.9% of individual PAH were removed by biodiesel. Tween 80 also showed comparable capability with biodiesel for PAH solubilization at a concentration of 10% for the spiked soils. Biodiesel solubilized a wider range of PAHs as compared to HPCD and tween 80 for the MPG soils. At PAH concentrations of 229.6 and 996.9 mg·kg^-1, biodiesel showed obvious advantage over the 10% HPCD and tween 80, because it removed higher than 80% of total PAH. In this study, a significant difference between PAH removals from the spiked and field MGP soils was observed; PAH removals from the MGP soil by HPCD and tween 80 were much lower than those from the spiked soil. These results demonstrate that the potential for utilizing biodiesel for remediation of highly PAH-contaminated soil has been established.     

Enrichment and transfer of polycyclic aromatic hydrocarbons (PAHs) through dust aerosol generation from soil to the air

● Compositional patterns of PAHs in dust aerosol vary from soil during dust generation. ● The EF of PAH in dust aerosol is affected by soil texture and soil PAH concentration. ● The sizes of dust aerosol play an important role in the enrichment of HMW-PAHs. Polycyclic aromatic hydrocarbons (PAHs) are major organic pollutants in soil. It is known that they are released to the atmosphere by wind via dust aerosol generation. However, it remains unclear how these pollutants are transferred through the air/soil interface. In this study, dust aerosols were generated in the laboratory using soils (sandy loam and loam) with various physicochemical properties. The PAH concentrations of these soils and their generated dust aerosol were measured, showing that the enrichment factors (EFs) of PAHs were affected by soil texture, PAH contamination level, molecular weight of PAH species and aerosol sizes. The PAHs with higher EFs (6.24–123.35 in dust PM_2.5; 7.02–47.65 in dust PM₁₀) usually had high molecular weights with more than four aromatic rings. In addition, the positive correlation between EFs of PAHs and the total OC_aerosol content of dust aerosol in different particle sizes was also statistically significant (r = 0.440, P < 0.05). This work provides insights into the relationship between atmospheric PAHs and the contaminated soils and the transfer process of PAHs through the soil-air interface.     

Residual levels and health risk of polycyclic aromatic hydrocarbons in freshwater fishes from Lake Small Bai-Yang-Dian, Northern China

The residual levels of polycyclic aromatic hydrocarbons (PAHs) in the liver, brain, gill and muscle tissues of four common edible freshwater fish species including crucian carp, snakehead fish, grass carp and silver carp collected from Lake Small Bai-Yang-Dian in northern China were measured by GC-MS. The distribution and composition pattern of PAHs in the fish tissues, and the effects of lipid contents in fish tissues and the octanol-water partition coefficient (Kow) of PAHs congeners on them were analyzed. The human health risk of PAHs though fish consumptions was estimated. The following results were obtained: (1) The average residual levels of total PAHs (PAH₁₆) on wet weight base in the different tissues of each fish species ranged from 4.764 to 144.254 ng/g ww. The differences in the average residual levels on wet weight base for PAH₁₆ within four fish species were not statistically significant (P > 0.05); however, these within four fish tissues were statistically significant (P < 0.01). (2) There were very similar distribution patterns of PAH congeners among both the fish tissues and the fish species, as indicated by statistically significant positive interrelationships (R = 0.58-0.97, P < 0.01 or P < 0.05). Low molecular weight (LMW) PAHs predominated the distribution in the fish tissues, accounting for 89.97% of total PAHs. Phe was the most dominant component, according for 37.79% of total PAHs, followed by Ant (18.59%), Flo (12.59%), Nap (10.79%), Fla (9.82%) and Pyr (6.43%). (3) The PAHs residues and distribution in the fish tissues are dependent on both the Kow of PAH congeners and the lipid contents in the fish tissues. There was a significant positive relationship (R = 0.7116, P < 0.0001) between lipid contents and PAHs residual levels. The statistically significant negative relationships (P < 0.05) were found between LogKow and log-transformed PAHs contents on wet weight base for all fish tissues except for the muscle tissue of snakehead fish, the brain and liver tissues of crucian carp. (4) The risk levels of total PAHs were lower than 10⁻⁵ for the muscle tissues of four studied fish species and for the brain tissues of grass carp and snakehead fish; while these were higher than 10⁻⁵ for the brain tissues of crucian carp and silver carp. The risk levels of total PAHs in the liver tissues of four studied fish species except for snakehead fish exceeded 10⁻⁵ for 2-4.5 times. However, the potency equivalent concentration (PEC) of total PAHs in four studied fish tissues were still lower than the maximum permissible BaP limits for crops and baked meat and for plants in the national criterions. The distributions of PAH congeners in fish were well simulated by a level III fugacity model, especially for low molecule weight PAHs.     

Polyzyklische aromatische Kohlenwasserstoffe aus diffusen Quellen

Goal and Scope

Polycyclic aromatic hydrocarbons (PAHs) are one group of persistent organic pollutants which are ubiquitous distributed in soils, even in rural areas. After their release into the atmosphere, transportation and deposition, they tend to accumulate in topsoils and sediments. Similar distribution pattern of PAHs in atmospheric deposition, soil samples as well as sediment samples indicate a close relationship between atmospheric input and accumulation of PAHs in the terrestrial environment. The intention of this paper was to estimate the time when precautionary values of the German law of soil protection will be exceeded in rural areas. Furthermore, current soil concentrations will be linked to the historical record of PAHs by means of enrichment factors.

Methods

The historical record of the atmospheric deposition rates of PAHs can be obtained from investigation of sediment cores. Based thereon, enrichment factors of PAHs in the environment were calculated. With these enrichment factors it was possible to estimate the recent PAH concentration in soils in rural areas from currently measured annual deposition rates. Furthermore, concentrations of PAHs in soils and deposition rates can be used to calculate the time when precautionary values will be reached.

Results and Conclusion

PAH deposition rates have been decreasing since about 1960 by a factor of 2–3, but stabilized during the last decade on a level high above pre-industrial time. Thus, further enrichment of PAH in topsoils has to be expected. Actual deposition rates in connection with historical enrichment factors allow to determine the median concentrations of PAHs in rural soils. The time when precautionary values will be reached was calculated to about 300 Years.

Outlook

The database to predict the further development of atmospheric deposition rates is very weak. There was a lack of validated methods concerning direct measurements of atmospheric POP deposition. Meanwhile, a national draft of a standard base on time-integrated passive sampling exists. This method can be implemented to establish a combined soil and deposition-monitoring program in order to assess the risk of further accumulation of POPs in soils.     

Polycyclic aromatic hydrocarbons in soils around Guanting Reservoir,Beijing, China

The concentrations of 16 polycyclic aromatic hydrocarbons (∑ 16PAHs) were measured by gas chromatography equipped with a mass spectrometry detector (GC-MS) in 56 topsoil samples around Guanting Reservior (GTR), which is an important water source for Beijing. Low to medium levels of PAH contamination (mean=394.2±580.7 ng g^?1 dry weight (d.w.)) was evident throughout the region. In addition, localised areas of high PAH contamination near steel and cement factories were identified, with ∑ 16PAHs concentrations as high as 4110 ng/g, dry weight (d.w.). There was a significant positive correlation (r²=0.570, p<0.01) between total organic carbon content and ∑ 16PAHs concentrations. Phenanthrene was the predominant compound, accounting for 27.2% of the ∑ PAH concentration, followed by chrysene>pyrene>benzo[a]anthracene≈ benzo[b]fluoranthene≈ benzo[a]pyrene. Four-ring PAH homologues (39%) were dominant. The higher proportion of 4–6 ring homologues, molecular indices, and the spatial distribution of PAH indicated that industrial discharges, incineration of wastes and traffic discharges were the major sources of soil PAHs around the water reservoir.