Regionalized concentrations and fingerprints of polycyclic aromatic hydrocarbons (PAHs) in German forest soils

Chronological distribution and potential sources of persistent toxic substances in soils from the glacier foreland of Midtre Lovénbreen, Svalbard

Despite its reputation as one of the cleanest regions globally, recent studies have identified the presence of various persistent toxic substances (PTSs) in the environmental matrices collected from Svalbard. This study investigated the chronological distribution and potential sources of 81 PTSs in soils from the glacier foreland of Midtre Lovénbreen. Soil samples (n = 45) were categorized by age based on exposure to the atmosphere due to glacier retreat in July 2014 into five age groups: 80-100 years (n = 7), 60-80 years (n = 12), 40-60 years (n = 16), 20-40 years (n = 7), and <20 years (n = 3). Concentrations of polychlorinated biphenyls (PCBs, n = 32) in soils varied with age, ranging from 0.29 to 0.74 ng g-1 dw. In addition, the concentrations of polycyclic aromatic hydrocarbons (PAHs, n = 28), perylene, and alkyl-PAHs (n = 20) in soils ranged from 21 to 80 ng g-1 dw, 2.9-62 ng g-1 dw, and 73-420 ng g-1 dw, respectively. The concentrations of PTSs were observed to be greater in older soils. Principal component analysis revealed that PCBs in soils originated from various product sources. Positive matrix factorization modeling estimated the association of PAHs in soils with potential origins, such as diesel emissions, petroleum and coal combustion, and coal. Potential sources of PAHs were mainly coal in younger soils and diesel emissions and petroleum combustion in older soils. Alkyl-PAH compositions in the soil were similar to those of bituminous coal, with a noteworthy degree of weathering observed in older soils. The accumulation rate and flux of PTSs in soils exhibited compound-specific patterns, reflecting factors such as long-range transport, fate, origin, and recent inputs. These findings can serve as baseline data for protecting and preserving polar environments.

Features of the polycyclic aromatic hydrocarbon's spatial distribution in the soils of the Don River delta

PAHs are one of the most toxic organic compounds classes which is obligatory controlled all over the world. There is a luck of studies devoted to the PAHs levels and sources identification in the south of Russia. The features of the PAHs accumulation and spatial distribution in hydromorphic soils (Fluvisol) were studied on the example of the soils of the Don River delta floodplain landscapes. It has been shown that changes in the PAHs content in soils depended on the type and intensity of the emission source. A factor analysis and multivariate linear regression analysis were carried out to determine the features of the spatial distribution for individual PAH compounds, considering the properties of soils and typical differences in the emission source. The most polluted areas in the studied area located along the transit line of the long-distance tankers, where the content of the most toxic high molecular PAHs compounds reached 8862 ng g-1. As a result of regression analysis, a relationship was established between the PAHs accumulation rate with the content of silt (particles less than 0.001 mm in size) and Ca2+ and Mg2+ exchangeable cations in the soil (at p-level < 0.0001). Differences in individual PAH content for medium and heavy loamy Fluvisol and depend on the influence of different types of pollution sources.

Concentrations, phase exchanges and source apportionment of polycyclic aromatic hydrocarbons (PAHs) In Bursa-Turkey

The present study aimed to determine the pollution levels derived from polycyclic aromatic hydrocarbons (PAHs) in air, plant and soil samples and to reveal the PAH exchange at the soil-air, soil-plant and plant-air interfaces. In this context, air and soil samples were collected in approximately 10-day periods between June 2021 and February 2022 from a semi-urban area in Bursa, an industrial city with a dense population. Also, plant branch samples were collected for the last three months. Total PAH concentrations in the atmosphere (∑₁₆PAH) and soil (∑₁₄PAH) ranged from 4.03 to 64.6 ng/m³ and 13-189.4 ng/g DM, respectively. PAH levels in the tree branches varied between 256.6 and 419.75 ng/g DM. In all air and soil samples, PAH levels were low in the summer and reached higher values in the winter. 3-ring PAHs were the dominant compounds, and their distribution in air and soil samples varied between 28.9%-71.9% and 22.8%-57.7%, respectively. According to the results of diagnostic ratios (DRs) and principal component analysis (PCA), both pyrolytic and petrogenic sources were found to be effective in PAH pollution in the sampling region. The fugacity fraction (ff) ratio and net flux (F_net) values indicated that the direction of movement of PAHs was from soil to air. In order to better understand the PAH movement in the environment, soil-plant exchange calculations were also achieved. The ratio of ∑₁₄PAH values measured to modeled concentrations (1.19<ratio<1.52) revealed that the model worked well for the sampling region and produced reasonable results. The ff and F_net levels showed that branches were saturated with PAHs and the direction of PAH movement was from plant to soil. The plant-air exchange results indicated that the direction of movement of PAHs was from plant to air for low molecular weight PAHs and the opposite was true for compounds with high molecular weight ones.

Polycyclic Aromatic Hydrocarbons Pollution Characteristics in Agricultural Soils of the Pearl River Delta Region, China

In order to investigate the pollution status of polycyclic aromatic hydrocarbons (PAHs) in the agricultural soil, 240 agricultural soil topsoil samples were collected from nine Pearl River Delta cities from June to September 2019. In addition, 72 samples were collected for vertical soil profiles, which soil profiles were excavated to a depth of 80 cm. After sample preparation, GC-MS was used for the separation of compounds on a HP-5MS quartz capillary column. ArcGIS software was used to map the spatial distribution. Health risk assessment was conducted using USEPA standard. The results showed that the total concentration of 16 PAHs ranged from 43.4 to 5630 ng/g, with an average of 219 ng/g. The spatial distribution showed that most of the seriously polluted areas were in the coastal area, near the port, and there was point source pollution in the Gaoming of Foshan. Vertically distributed display Zhuhai, Jiangmen, Zhaoqing, Shenzhen and Dongguan increased and then decreased from bottom to bottom, showing a low-high-low pattern, the concentration of PAHs in Zhongshan and Foshan decreased with the soil depth, while the concentration of PAHs in Guangzhou and Huizhou was enriched with human activities. The PAHs components in soil samples were mainly medium and high rings (4−6 rings). The analysis of the origin of PAH in soil samples showed that the mixture of incomplete combustion sources of fossil fuels such as coal and biomass and traffic emission sources were the main sources of soil PAHs. A small amount can be attributed to oil sources such as oil spills. The human health risk assessment showed no cancer risk for children, while for adults, may cause a potential risk of cancer, which needs to be noticed. Spearman correlation analysis showed that PAH content was significantly correlated with SOC (p < 0.01) and pH (p < 0.05). Port transport, road emissions and industrial production make the area a pollution hot topic, and supervision should be strengthened to protect the environment and food safety.

Dilution of concentrations of PAHs from atmospheric particles, bulk deposition to soil: a review

Polycyclic aromatic hydrocarbons (PAHs) are emitted to the atmosphere by various anthropogenic activities as well as natural sources, they undergo long-range transport, are degraded (e.g., by photolysis) and finally they are deposited onto the surface and potentially accumulate in topsoil. The dry deposition of particle-bound PAHs dominates the accumulation of PAHs in soil and their further fate in soil is governed by sorption/desorption from these airborne particles. This paper offers an overview on concentrations of particle-bound PAHs, the dry deposition fluxes and finally concentrations of PAHs in soil. In addition, spatial and temporal variations of PAHs are considered. The results show that concentrations of particle-bound PAHs typically range from 1 mg g^-1 up to 10 mg g^-1 in cities with coal-based heating in winter and in countries with coal-based industry incl. electrical power production. These values are very high and exceed the legal limits set in soils by orders of magnitude. Atmospheric deposition rates typically reach several mg m^-2 a^-1, but in winter, especially in countries with heating, deposition rates are up to 10 times higher. PAHs concentrations in soils show a very wide variation from less than 1 µg g^-1 in rural areas up to 10 µg g^-1 in urban space, which is about 1000 times lower than the concentration of PAHs on particles in the atmosphere. This demonstrates the relevance of high concentrations of PAHs on airborne particles deposited on soils, which also highlights the importance of considering incremental lifetime cancer risk models for both air and soil and assessing the total health risk of PAHs to humans.

Spatial Distribution, Potential Sources, and Health Risk of Polycyclic Aromatic Hydrocarbons (PAHs) in the Surface Soils under Different Land-Use Covers of Shanxi Province, North China

Polycyclic aromatic hydrocarbons (PAHs) are widespread in the environment and pose a serious threat to the soil ecosystem. In order to better understand the health risks for residents exposed to PAH-contaminated soil, 173 surface soil samples were collected in Shanxi Province, China, to detect the levels of 16 priority PAHs. The spatial distribution patterns of PAHs were explored using interpolation and spatial clustering analysis, and the probable sources of soil PAHs were identified for different land-use covers. The results indicate that the soil Σ16 PAH concentration ranged from 22.12 to 1337.82 ng g^-1, with a mean of 224.21 ng g^-1. The soils were weakly to moderately contaminated by high molecular weight PAHs (3-5 ring) and the Taiyuan-Linfen Basin was the most polluted areas. In addition, the concentration of soil PAHs on construction land was higher than that on other land-use covers. Key sources of soil PAHs were related to industrial activities dominated by coal burning, coking, and heavy traffic. Based on the exposure risk assessment of PAHs, more than 10% of the area was revealed to be likely to suffer from high carcinogenic risks for children. The study maps the high-risk distribution of soil PAHs in Shanxi Province and provides PAH pollution reduction strategies for policy makers to prevent adverse health risks to residents.

Environmental Risk Assessment of Polycyclic Aromatic Hydrocarbons in Farmland Soils near Highways: A Case Study of Guangzhou, China

Recently, the rapid growth in vehicle activity in rapidly urbanized areas has led to the discharge of large amounts of polycyclic aromatic hydrocarbons (PAHs) into roadside soils and these compounds have gradually accumulated in the soil, which poses a serious threat to national food security and public health. However, previous studies did not clearly investigate the seasonal differences in PAH pollution of roadside soil by different highways. Therefore, based on field investigations, this study collected 84 soil surface samples to compare the pollution characteristics of 16 PAHs in farmland soils located near different roads in different seasons in Guangzhou, China. The results showed that the concentration of Σ16PAHs in farmland soils in spring (with a mean value of 258.604 μg/kg) was much higher than that in autumn (with a mean value of 157.531 μg/kg). There are differences in the PAH compositions in spring (4 ring > 3 ring > 5 ring > 6 ring) and autumn (4 ring > 5 ring > 6 ring > 3 ring). The proportion of 4−6 ring PAHs was much higher than 2−3 ring PAHs in both seasons. The spatial differences were significant. The sampling areas with higher concentrations of 16 PAHs were Tanbu Town, Huadu District (TB), Shitan Town, Zengcheng District (ST), and Huashan Town, Huadu District (HS), while the lowest concentration was in Lanhe Town, Nansha District (LH). The results of the diagnostic ratios showed that the main source of soil PAHs consists of a mixed source from petroleum and biomass combustion. The results from the total pollution assessment method and Nemerow index method indicated that the pollution levels of PAHs in the farmland soils indicated weak contamination. Our study provides a scientific basis for the prevention and control of soil pollution in farmlands near highways.

Background concentration, risk assessment and regulatory threshold development: Polycyclic aromatic hydrocarbons (PAH) in Milwaukee, Wisconsin surface soils

Inputs of polycyclic aromatic hydrocarbons (PAHs) of regulatory interest from diffuse atmospheric sources within urban areas frequently elevate local soil concentrations to levels requiring remediation despite the lack of in-situ contamination. This research sought to determine the distribution and potential health effects of aerially deposited PAHs in soil within the urban core of metropolitan Milwaukee, Wisconsin, U.S.A. as part of a soil regulatory standards reevaluation. Park areas (n = 27) identified as undisturbed for 80+ years, containing no fill material, and receiving only atmospheric deposition were selected for composite surface and 92 cm core soil sample collection (n = 295). Samples were analyzed for the 16 USEPA priority PAHs, 1- and 2- methylnapthalene and ancillary soil properties. Soil core and ancillary data confirm lack of site disturbance. PAH diagnostic ratios and homologue summations indicate that diffuse multiple point source emissions contribute equally to PAH deposition throughout the area. Benzo(a)pyrene (BaP) and dibenz(a,h)anthracene mean concentrations exceed health-based clean up levels. Risk assessment shows only a worst-case exposure scenario (BaP at the 95% upper confidence limit) increasing cancer risk (1.67 × 10^-6) over current regulatory thresholds (1.0 × 10^-6). Health quotients show potential health risks from fluoranthene and pyrene for daily park users and from BaP for all others. Mean soil PAH values are similar to New Orleans, but lower than Chicago, Boston, and London reflecting industrial history and site selection protocols. The soil PAH results presented here for sites selected for non-manipulated soils combined with an almost 100-year uninterrupted atmospheric exposure effectively show the maximum potential PAH values that can be found at any given undisturbed location within the Milwaukee urban core due solely to atmospheric deposition.

Contamination and human health risks of polycyclic aromatic hydrocarbons in surface soils from Tianjin coastal new region, China

Polycyclic aromatic hydrocarbons (PAHs) in urban soils are of increasing concern because of their potential toxicity and persistence. However, there is limited information about PAHs in Tianjin coastal new region, although it is an important economic and industrial center in Northern China. Here we determined the concentrations of PAHs in 210 surface soil samples collected from this region according to administrative divisions covering Han'gu district, Tanggu district, and Dagang district, to evaluate their contamination and potential cancer risks. The concentrations of 16 PAHs ranged from 58.2 to 9160 ng g^-1, and the highest concentration was found in Han'gu district. According to the incremental lifetime cancer risk (ILCR) model, the soils from Han'gu district and Dagang district posed a moderate carcinogenic risk to residents, and dermal contact was the main exposure pathway. Besides, ILCRs for children through ingestion were comparable to those for adults but apparently higher than adolescents, while ILCRs of dermal contact for adults were higher than children and adolescents. Comparisons between the layout of industrial zones and the distributions of PAHs as well as ILCRs indicate that PAHs accumulating in soils and then incurring risk areas is partly controlled by the economic and industrial structure.

Potential sources, influencing factors, and health risks of polycyclic aromatic hydrocarbons (PAHs) in the surface soil of urban parks in Beijing, China

Urban parks are an important part of the urban ecological environment. The environmental quality of parks is related to human health. To evaluate sources of polycyclic aromatic hydrocarbons (PAHs) in soils of urban parks and their possible health risks, soil samples from 122 parks in Beijing, China, were collected and analyzed. The total content of 16 PAHs between 0.066 and 6.867 mg/kg. Four-ring PAHs were predominant, followed by 5-ring PAHs, while the fraction of 2-ring PAHs was the lowest. The dominant PAHs sources were found to be coal combustion and oil fuels such as gasoline and diesel. A conditional inference tree (CIT) was used to identify the key influencing factors for PAHs. Traffic emissions was the most important factor, followed by coal consumption, as well as the history and location of the park. Incremental lifetime cancer risk (ILCR) for urban park soil in Beijing were low under normal conditions. The soil PAHs exposure pathway risk for both children and adults decreased in the following order: ingestion > dermal contact > inhalation. The risk from soil in parks to children's health is slightly higher than that of adults, although the health risk due to exposure to PAHs was not extraordinary. Ecosystem risk was negligible.

Surface horizons of forest soils for the diagnosis of soil environment contamination and toxicity caused by polycyclic aromatic hydrocarbons (PAHs)

Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants that are released into soils primarily from the air, with wet and dry deposition. To assess the contamination of the forest soil environment, soil samples were collected from organic and mineral horizons from three study areas representing a gradient of pollution across Poland (the ‘pollution transect’). The soils examined varied in PAH contents, generally from 124.3 μg·kg^-1 dw in the areas deemed to be the background zone to 9165.5 μk·kg^-1 dw in industrial areas in the O horizon and from 12.6 μk·kg^-1 dw to 4454.6 μk·kg^-1 dw in the A horizon. The PAH toxicities oscillated from 20.0–2670.8 μg TEQ·kg^-1 dw in the O horizon and from 1.73–694.7 μg TEQ·kg^-1 dw in the A horizon. The enrichment factor values point to a more intensive accumulation of PAHs with relatively high molecular weights along the pollution transect. The PAH diagnostic ratio values indicated that the main PAH emission sources were from coal and wood combustion.

Investigation and Assessment for an effective approach to the reclamation of Polycyclic Aromatic Hydrocarbon (PAHs) contaminated site: SIN Bagnoli, Italy

Native plant species were screened for their remediation potential for the removal of Polycyclic Aromatic Hydrocarbons (PAHs) contaminated soil of Bagnoli brownfield site (Southern Italy). Soils at this site contain all of the PAHs congeners at concentration levels well above the contamination threshold limits established by Italian environmental legislation for residential/recreational land use, which represent the remediation target. The concentration of 13 High Molecular Weight Polycyclic Aromatic Hydrocarbons in soil rhizosphere, plants roots and plants leaves was assessed in order to evaluate native plants suitability for a gentle remediation of the study area. Analysis of soil microorganisms are provides important knowledge about bioremediation approach. Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria are the main phyla of bacteria observed in polluted soil. Functional metagenomics showed changes in dioxygenases, laccase, protocatechuate, and benzoate-degrading enzyme genes. Indolacetic acid production, siderophores release, exopolysaccharides production and ammonia production are the key for the selection of the rhizosphere bacterial population. Our data demonstrated that the natural plant-bacteria partnership is the best strategy for the remediation of a PAHs-contaminated soil.

25 years monitoring of PAHs and petroleum hydrocarbons biodegradation in soil

Biodegradation of polycyclic aromatic hydrocarbons (PAHs) and total petroleum hydrocarbons (TPH) in sediment and soil has been monitored on seven experimental fields during periods up to 25 years. With this unique dataset, we investigated long-term very slow biodegradation under field conditions. . The data show that three biodegradation rates can be distinguished for PAHs: 1) rapid degradation during the first year, 2) slow degradation during the following 6 years and 3), subject of this paper, a very slow degradation after 7 years until at least 25 years. Beside 2-, 3- and 4-ring PAHs, also 5- and 6-ring PAHs (aromatic rings) were degraded, all at the same rate during very slow degradation. In the period of very slow degradation, 6% yr^-1 of the PAHs present were removed in five fields and 2% yr^-1 in two other fields, while in the same period no very slow degradation of TPH could be observed. The remaining petroleum hydrocarbons were high boiling and non-toxic. Using the calculated degradation rates and the independently measured bioavailability of the PAHs (Tenax-method), the PAHs degradation curves of all seven monitored fields could be modelled. Applying the model and data obtained with the Tenax-method for fresh contaminated material, results of long-term biodegradation can be predicted, which can support the use of bioremediation in order to obtain a legally acceptable residual concentration.

Elevated temperature and CO2 affect responses of European aspen (Populus tremula) to soil pyrene contamination

High northern latitudes are climatic sensitive areas, and are also regions to which polycyclic aromatic hydrocarbons (PAHs) easily transport and accumulate with potential risk to natural ecosystems. However, the effect of PAHs on northern woody plant growth and defense under climate change is very little studied. Here, we conducted a unique experiment in greenhouses to investigate sex-related responses of the dioecious Populus tremula to pyrene (50mgkg^-1) and residue of pyrene in soils under ambient and elevated temperature (+1.8°C on average) and CO₂ (740ppm). Pyrene decreased stem biomass and leaf area by 9% and 6%, respectively under ambient conditions, and the reduction of leaf area was more severe under elevated temperature (38%), elevated CO₂ (37%), and combined T+CO₂ (42%). Other growth parameters were unchanged by pyrene. Pyrene did not affect the concentration of leaf total phenolics under ambient conditions, but increased it by 16%, 1%, and 20% compared to controls under elevated temperature, elevated CO₂, and T+CO₂, respectively. Pyrene had only minor sex-specific effects on plant growth and phenolics. The concentration of residual pyrene in pyrene-spiked soils was higher under elevated CO₂ than under ambient, elevated temperature, and combined T+CO₂. The results suggest that both sexes of P. tremula have the capacity to regulate growth and metabolism to adjust to the stress of the tested pyrene contamination under elevated temperature and CO₂, but potential risk of pyrene to plants still exists in the future changing climate.

Sources and fate of polycyclic aromatic compounds (PAHs, oxygenated PAHs and azaarenes) in forest soil profiles opposite of an aluminium plant

Little is known about oxygenated polycyclic aromatic hydrocarbons (OPAHs) and azaarenes (AZAs) in forest soils. We sampled all horizons of forest soils from five locations at increasing distances from an Al plant in Slovakia, and determined their polycyclic aromatic compound (PACs) concentrations. The ∑29PAHs concentrations were highest in the Oa and lowest in the Oi horizon, while the ∑14OPAHs and ∑4AZAs concentrations did not show a consistent vertical distribution among the organic horizons. The concentration ratios of PAHs and OPAHs between deeper O horizons and their overlying horizon (enrichment factors) were positively correlated with the octanol-water partition coefficients (K_OW) at several locations. This is attributed to the slower degradation of the more hydrophobic PACs during organic matter decomposition. PACs concentrations decreased from the organic layer to the mineral horizons. The concentrations of ∑29PAHs (2400-17,000 ng g^-1), ∑14OPAHs (430-2900 ng g^-1) and ∑4AZAs (27-280 ng g^-1) in the mineral A horizon generally decreased with increasing distance from the Al plant. In the A horizons, the concentrations of ∑29PAHs were correlated with those of ∑14OPAHs (r = 0.95, p = 0.02) and ∑4AZAs (r = 0.93, p = 0.02) suggesting that bioturbation was the main transport process of PACs from the organic layer into the mineral soil. At each location, the concentrations of PACs generally decreased with increasing depth of the mineral soil. Enrichment factors of PAHs in the mineral horizons were not correlated with K_OW, pointing at colloid-assisted transport and bioturbation. The enrichment factors of OPAHs (in mineral horizons) at a site were negatively correlated with their K_OW values indicating that these compounds were leached in dissolved form. Compared to a study 13 years before, the concentrations of PAHs had decreased in the O horizons but increased in the A and B horizons because of soil-internal redistribution after emissions had been reduced.

Polycyclic Aromatic Hydrocarbons Content in Contaminated Forest Soils with Different Humus Types

The aim of the study was to determine polycyclic aromatic hydrocarbon (PAH) content in different forest humus types. The investigation was carried out in Chrzanów Forest District in southern Poland. Twenty research plots with different humus types (mor and mull) were selected. The samples for analysis were taken after litter horizons removing from a depth of 0-10 cm (from the Of- and Oh-horizon total or A-horizon). pH, organic carbon and total nitrogen content, base cations, acidity, and heavy metal content were determined. In the natural moisture state, the activity of dehydrogenase was determined. The study included the determination of PAH content. The conducted research confirms strong contamination of study soil by PAHs and heavy metals. Our experiment provided evidence that different forest humus types accumulate different PAH amounts. The highest content of PAHs and heavy metals was recorded in mor humus type. The content of PAHs in forest humus horizon depends on the content and quality of soil organic matter. Weaker degradation of hydrocarbons is associated with lower biological activity of soils. The mull humus type showed lower content of PAHs and at the same time the highest biological activity confirmed by high dehydrogenase activity.

Effects of soil pyrene contamination on growth and phenolics in Norway spruce (Picea abies) are modified by elevated temperature and CO2

With the constant accumulation of polycyclic aromatic hydrocarbons (PAHs) in soil and increasing temperature and CO₂ levels, plants will inevitably be exposed to combined stress. Studies on the effects of such combined stresses are needed to develop mitigation and adaptation measures. Here, we investigated the effects of soil pyrene contamination (50 mg kg^-1) on growth and phenolics of 1-year-old Norway spruce seedlings from five different origins in Finland at elevated temperature (+ 2 °C) and CO₂ (+ 360 ppm). Pyrene significantly decreased spruce height growth (0-48%), needle biomass (0-44%), stem biomass (0-43%), and total phenolic concentrations in needles (2-13%) and stems (1-19%) compared to control plants. Elevated temperature alone did not affect growth but led to lower concentrations of total phenolics in needles (5-29%) and stems (5-18%) in both soil treatments. By contrast, elevated CO₂ led to higher needle biomass (0-39%) in pyrene-spiked soils and higher concentrations of stem phenolics (0-18%) in pyrene-spiked and control soils compared to ambient treatments. The decrease in height growth and phenolic concentrations caused by pyrene was greater at elevated temperature, while elevated CO₂ only marginally modified the response. Seedlings from different origins showed different responses to the combined environmental stressors. The changes in growth and in the quantity and quality of phenolics in this study suggest that future climate changes will aggravate the negative influence of soil pyrene pollution on northern conifer forest ecosystems.

Comparative study of dioxin contamination from forest soil samples (BZE II) by mass spectrometry and EROD bioassay

Dioxins and dioxin-like compounds can be analyzed by bioanalytical screening methods to evaluate their biotoxicity. In vitro bioassays, based on 7-ethoxyresorufin-O-deethylase (EROD) and the activity of cytochrome P450 1A1 and the aryl hydrogen receptor (AhR) pathway, are employed for the evaluation of bioanalytical equivalents (BEQ) of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs) from a wide variety of sample matrices. Here, we present the evaluation of 11 humic soil samples derived from forest stands across Germany and a comparison of the BEQ values against toxic equivalents (TEQ, PCDD/Fs+PCBs) derived by chemical analysis. BEQ values ranged from 8.8 to 34.1 while TEQ values from 13.9 to 60.5 pg/g dry weight. Additional two subsequent mineral layers were analyzed to identify the BEQ/TEQ gradient vertically, showing a TEQ decrease of 85.1 and 93.8 % from the humic to the first and second mineral layers, respectively. For BEQ values, a decrease as well as an increase was detected. BEQ measurements were performed with and without sample clean-up. Omitting clean-up revealed about 20 times increased BEQ values presumably due to non-persistent bioactive compounds not detected by chemical analysis. The results we present suggest that the EROD assay can be used for the screening of large sample quantities for the identification of samples showing dioxin and dioxin-like contaminations even at low levels, which can then be further analyzed by chemical analysis to identify the congener composition. The study also shows that EROD results give a qualitative image of the contamination. EROD seems to be interfered with cross-contaminants specifically for soils with high biological activity as forest layers.

Results of the second national forest soil inventory in Germany - Interpretation of level and stock profiles for PCDD/F and PCB in terms of vegetation and humus type

Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and polychlorinated biphenyls (PCBs) were detected in 86 humic topsoil layers and in a subset of 11 randomly selected top mineral forest soils at the depths of 0-5cm and 5-10cm collected from different federal states of Germany. The distribution of these persistent organic pollutants (POPs) in humic topsoils with respect to vegetation cover (coniferous vs. deciduous vs. mixed), total organic carbon (TOC), altitude and latitude data was investigated. There is cross correlation between the contents and TOC while the correlation with latitude indicates higher abundances of POPs in central Germany where there is high population density accompanied with industrial activities. The calculated stocks suggest that humus type (mor, mull, or moder) in conjunction with forest type can explain the relative POPs abundances in different soil layers. Generally, humic topsoils show highest contents of POPs compare to the two mineral soils with a ratio of 100:10:1. However, the stock humic layers of coniferous stands contribute about 50% to the total stock, whereas at deciduous stands the stock is mainly located in the upper mineral soil layer (0-5cm). The soil-water distribution coefficients (Kd) were calculated to estimate the potential translocation in the different soil types. The Kd values vary among the PCBs and PCDD/Fs congeners and are most variable for humic topsoils. There is pronounced chemical abundance in the top mineral soils with increasing Kd and this points to non-water bound transport processes for superlipophilic compounds.

Recirculation of biomass ashes onto forest soils: ash composition, mineralogy and leaching properties

In Denmark, increasing amounts of wood ashes are generated from biomass combustion for energy production. The utilisation of ashes on top of forest soil for liming purposes has been proposed asan alternative to landfilling. Danish wood ash samples were collected and characterised with respect to chemical composition, mineralogy and leaching properties (batch leaching at L/S 2 and 10L/kg, and pH-dependent leaching at 10L/kg). Large variations in the ash liming properties were observed (ANC_7.5: 1.8-6.4meqH⁺/g), indicating that similar soil application dosages may result in different liming effects. High contents of Ca, Si, P, K and Mg were observed in all samples, while the highest contents of S and N were found in fly ashes and mixed ashes (combination of fly and bottom ashes). Similarly, the highest contents of some trace metals, e.g. Cd, Mo and Se, were observed for fly ash. Releases of major, minor and trace elements were affected significantly by pH: high releases of PO₄^3-, Mg, Zn, Cu and Cd were found for acidic conditions relevant to forest soils, while the highest releases of Mo and Cr were observed in alkaline conditions. Mineral phases were selected based on XRD analyses and the existing literature, and they were applied as inputs for the geochemical modelling of pH-dependent leaching. Mineral dissolution was found adequate for a wide range of major elements and nutrients, while the description of trace elements could be done only for parts of the pH-range. Content and leaching of PAHs were observed below detection limits. The source-term release of Ca, K, Mg, Mn, and P in acidic conditions relevant to forest soils was higher than ten years of atmospheric deposition, in contrast to the relatively low release of Al, Fe and Na. The potential release of Cd was found to be the most critical element compared with soil quality criteria, whereas the maximum theoretical loads of Ba, Cd, Cr, Sr, Mo, Ni, Pb, Sb, Se, Sn and V were relatively low.

Seasonal variation and health risk assessment of organochlorine compounds in urban soils of Novi Sad, Serbia

The aim of this paper was to determine spatial and seasonal variation of 6 indicator polychlorinated biphenyls (PCBs) and 18 organochlorine pesticides (OCPs) in urban soils of Novi Sad, Serbia. Sixty surface soil samples were collected during both winter and summer season, from different types of locations: schools, recreational areas, residential and industrial zones. Samples were treated using the method of accelerated solvent extraction, which allows simultaneous extraction and clean up of PCBs and OCPs. Targeted compounds were analyzed by GC-μECD and confirmed by GC-MS. The total concentrations of studied PCBs varied from <LOD to 18.9 ng g^-1 (mean 2.84 ng g^-1 and median value of 1.21 ng g^-1) in winter and from <LOD to 24.6 ng g^-1 (mean 3.27 ng g^-1 and median value of 1.60 ng g^-1) in summer. Regarding the OCPs analyzed, dichlorodiphenyltrichloroethanes (DDTs) were only detected in both seasons. The total concentration of DDTs ranging from <LOD to 86.3 ng g^-1 (mean 7.57 ng g^-1 and median value of 1.87 ng g^-1) in summer and from <LOD to 182 ng g^-1 (mean 15.6 ng g^-1 and median value of 3.15 ng g^-1) in winter. There were no significant difference between seasons for studied PCBs and DDTs. Spatial distribution of PCBs and DDTs were also evaluated using Arc GIS. Additional, principle component analysis was performed to evaluate relationships between PCBs, DDTs and soil characteristics. Positive correlation was observed among p,p'-DDE, p,p'-DDD and organic matter. The total lifetime carcinogenic risk indicated that the lifetime cancer risk was acceptable.

Occurrence and geographic distribution of polycyclic aromatic hydrocarbons in agricultural soils in eastern China

Polycyclic aromatic hydrocarbons (PAHs) in agricultural soils, eastern China, were studied through a collection of surface samples at 109 sites. The study covered US EPA priority pollutants but also several non-priority isomers including some dibenzopyrenes which are expected to have higher toxic potentials. The total PAH concentrations varied extensively from 8.8 to 3880 μg/kg, with a geometric mean of 158 μg/kg. There were significant differences in both the concentrations and composition profiles between the south and the north regions. The overall geographical distribution pattern was strongly influenced by both the per capita gross domestic product and soil organic carbon (SOC) content. The former is an indicator of anthropogenic emissions while soil SOC content is associated with the accumulative capacities of the soils. The sequestration mechanism is an important process controlling fates of PAHs in agricultural soil.

The fingerprints of dioxin-like bromocarbazoles and chlorocarbazoles in selected forest soils in Germany

The occurrence of bromocarbazoles and chlorocarbazoles was studied in 86 forest soil samples from different regions in Germany. Carbazole, 3-chlorocarbazole, 3-bromocarbazole and 3,6-dibromocarbazole were qualitatively detected in the humic layer of 59 soil samples with bromocarbazoles reported here for the first time in soil. Furthermore, the halogenated carbazoles, PCDD/Fs and PCBs were detected in the humic and mineral soil horizons (0-5 cm and 5-10 cm) of a subset of 11 soil samples subjected to quantitative analysis. Concentrations ranged from 0.6 to 267.6 ng/g (carbazole); 0.2-7.2 ng/g (3-bromocarbazole); 0.0-9.1 ng/g (3-chlorocarbazole); 0.2-19.8 ng/g (3,6-dibromocarbazole); 0.4-67.6 ng/g (3,6-dichlorocarbazole); 0.0-0.7 ng/g (PCDDs); 0.0-0.3 ng/g (PCDFs) and 0.0-33.7 ng/g (PCBs). Concentrations decreased with depth and correlated positively to total organic carbon (TOC). When it was based on TOC%, an increase in concentration with depth was observed in most soil samples. With respect to dioxin-like toxicity, 3-bromocarbazole, 3-chlorocarbazole, 3,6-dibromocarbazole and 3,6-dichlorocarbazoles caused induction of CYP1A1-dependent EROD activity in HII4E rat hepatoma cell line. Their relative effect potency after 72 h exposure ranged from 0.00005 to 0.00013 and was directly related to the degree of halogenation with 2,3,7,8-tetrachlorodibenzo-p-dioxin as reference. Furthermore, their contribution to overall soil dioxin-like toxicity was not significant in comparison to PCDD/Fs and PCBs though the sum toxic equivalency was limited to three halogenated carbazole congeners. Bromocarbazoles and chlorocarbazoles are emerging dioxin-like toxic environmental contaminants with potential for wide distribution occurring simultaneously with PCDD/Fs and PCBs.

Investigation of spatial distributions and sources of persistent organic pollutants (POPs) in a heavily polluted industrial region using tree components

Spatial distributions of persistent organic pollutants (POPs) were investigated in Iskenderun industrial region in Turkey. POP concentrations were measured in different tree components (i.e., pine needle, branch, bark, and stem) collected at several industrial and background sites (n = 27). Also, air, litter, and soil samples were analyzed to determine the relationship of atmospheric pollutants with tree components, litter, and soil. Spatial variation of measured concentrations and factor analysis showed that the iron-steel plants are the most important POP sources in Iskenderun area. Correlations of ambient air levels to those measured in soil, litter, and tree components were significant showing that POPs are exchanged between atmosphere and these compartments. Results have suggested that tree components, litter and soil could be used to determine the spatial distributions and sources of atmospheric POPs in a region. POP quantities (mg/ha) accumulated in different tree components, litter, and soil were also predicted. Generally, the highest quantities were accumulated by stem and needles. In terms of overall inventory, including trees, litter and soil, the highest accumulated quantities were found in soil followed by trees and litter, indicating that in addition to soil, vegetation is a notable reservoir accumulating POPs. Ambient air POP concentrations were also estimated using a bark/air partitioning model. The estimated/measured ratios were close to 1.0 for several compounds and the results showed that the atmospheric POP concentrations could be estimated from the bark measurements within factors of 0.23-3.07, 1.02-6.67, 0.63-7.44, 1.07-3.37 for polycyclic aromatic hydrocarbons, polychlorinated biphenyls, polychlorinated naphthalenes, and polybrominated diphenyl ethers, respectively.

Climate change impact on the PAH photodegradation in soils: Characterization and metabolites identification

Polycyclic aromatic hydrocarbons (PAHs) are airborne pollutants that are deposited on soils. As climate change is already altering temperature and solar radiation, the global warming is suggested to impact the environmental fate of PAHs. This study was aimed at evaluating the effect of climate change on the PAH photodegradation in soils. Samples of Mediterranean soils were subjected to different temperature and light radiation conditions in a climate chamber. Two climate scenarios were considered according to IPCC projections: 1) a base (B) scenario, being temperature and light intensity 20°C and 9.6W/m(2), respectively, and 2) a climate change (CC) scenario, working at 24°C and 24W/m(2), respectively. As expected, low molecular weight PAHs were rapidly volatilized when increasing both temperature and light intensity. In contrast, medium and high molecular weight PAHs presented different photodegradation rates in soils with different texture, which was likely related to the amount of photocatalysts contained in both soils. In turn, the hydrogen isotopic composition of some of the PAHs under study was also investigated to verify any degradation process. Hydrogen isotopes confirmed that benzo(a)pyrene is degraded in both B and CC scenarios, not only under light but also in the darkness, revealing unknown degradation processes occurring when light is lacking. Potential generation pathways of PAH photodegradation by-products were also suggested, being a higher number of metabolites formed in the CC scenario. Consequently, in a more or less near future, although humans might be less exposed to PAHs, they could be exposed to new metabolites of these pollutants, which might be even more toxic.

Spatial Distribution of Polycyclic Aromatic Hydrocarbon (PAH) Concentrations in Soils from Bursa, Turkey

The objectives of this study were to identify regional variations in soil polycyclic aromatic hydrocarbon (PAH) contamination in Bursa, Turkey, and to determine the distributions and sources of various PAH species and their possible sources. Surface soil samples were collected from 20 different locations. The PAH concentrations in soil samples were analyzed using gas chromatography-mass spectrometry (GC-MS). The total PAH concentrations (∑12 PAH) varied spatially between 8 and 4970 ng/g dry matter (DM). The highest concentrations were measured in soils taken from traffic+barbecue+ residential areas (4970 ng/g DM) and areas with cement (4382 ng/g DM) and iron-steel (4000 ng/g DM) factories. In addition, the amounts of ∑7 carcinogenic PAH ranged from 1 to 3684 ng/g DM, and between 5 and 74 % of the total PAHs consisted of such compounds. Overall, 4-ring PAH compounds (Fl, Pyr, BaA and Chr) were dominant in the soil samples, with 29-82 % of the ∑12 PAH consisting of 4-ring PAH compounds. The ∑12 BaPeq values ranged from 0.1 to 381.8 ng/g DM. Following an evaluation of the molecular diagnostic ratios, it was concluded that the PAH pollution in Bursa soil was related to pyrolytic sources; however, the impact of petrogenic sources should not be ignored.

Persistent endosulfan sulfate is found with highest abundance among endosulfan I, II, and sulfate in German forest soils

Endosulfan - an agricultural insecticide and banned by Stockholm Convention - is produced as a 2:1 to 7:3 mixture of isomers endosulfan I (ESI) and endosulfan II (ESII). Endosulfan is transformed under aerobic conditions into endosulfan sulfate (ESS). The study shows for 76 sampling locations in German forests that endosulfan is abundant in all samples with an opposite ratio between the ESI and ESII than the technical product, where the main metabolite ESS is found with even higher abundance. The ratio between ESI/ESII and ESS show clear dependence on the type of stands (coniferous vs. deciduous) and humus type and increases from deciduous via mixed to coniferous forest stands. The study argues for a systematic monitoring of ESI, ESII, and ESS and underlines the need for further research, specifically on the fate of endosulfan including biomagnifications and bioaccumulation in soil.