Polycyclic aromatic hydrocarbons (PAHs) in soils of the Moscow Region--concentrations, temporal trends, and small-scale distribution

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.

Speciation Variation and Bio-Activation of Soil Heavy Metals (Cd and Cr) in Rice-Rape Rotation Lands in Karst Regions

Heavy metals in soil are in a high background state in Karst areas, and agricultural activities will affect the bioactivity of heavy metals. The heavy metal (Cd and Cr) bioactivity and their activation effects in rice-rape rotation lands in Karst areas were studied based on field experiments and laboratory analysis, and the influencing factors of heavy metal activity were analyzed based on the physical and chemical properties of soil. The results suggest that the residual fraction was the largest and the exchangeable fraction was the smallest for both Cr and Cd in rice-rape rotation lands in Karst areas. During the rice-rape rotation process, Cd and Cr tended to be released from the residual fraction and transformed into the other four fractions. The fractions with high bioactivity, including the exchangeable fraction and carbonate fraction, increased to different degrees. Rice-rape rotation could activate the activity of soil Cd and Cr in Karst areas. It is also revealed that the activity of soil Cd and Cr in Karst areas was closely associated with soil pH and electric potential (Eh). In the 0–20 cm soil layer, Cr showed a significant negative correlation with pH (r = −0.69, p < 0.05), while both Cr and Cd showed significant negative correlations with Eh, and the correlation coefficients were −0.85 (p < 0.01) and −0.83 (p < 0.01), respectively. In the 20–40 cm soil layer, Cr showed significant negative correlations with Eh, and the correlation coefficient was −0.95 (p < 0.01). No significant correlation between the activity of soil Cd and Cr and soil mechanical composition was observed. This study revealed that special attention should be paid to changes in pH and Eh in consideration of heavy metal activity in the rice-rape rotation process.

Spatial distribution of polycyclic aromatic hydrocarbon contamination in urban soil of China

Soil pollution is becoming increasingly prominent and polycyclic aromatic hydrocarbons (PAHs) are key pollutants in urban areas. Understanding the sources of PAH pollution is an effective step toward its control and reduction. The main purpose of this review was to collate the spatial distribution, pollution level, pollution sources, and potential risks of PAHs in urban soils of different regions of China. Relevant data of PAH soil contamination in Chinese provinces and cities were extracted from studies published from 2000 to 2018. The concentrations of total PAHs (Σ₁₆PAHs) ranged from 65.01 to 23603.05 μg/kg for urban soils with a mean of 2801.98 μg/kg. According to the Maliszewska-Kordybach classification criteria, about 47% of the regions of China were heavily contaminated, 23% of the regions were contaminated, and 17% of the regions were weakly contaminated, while only 13% of regions were not contaminated. Based on the results of the total PAHs data from 30 provinces and cities and the results of individual compounds from 27 cities, 18 provinces and cities were classified as "severely" contaminated with a Nemero Comprehensive Index (PI) > 3.0. The results of this review indicate that the main sources of PAH pollution in urban soils of China are coal combustion and automobile exhaust emissions, followed by oil, biomass, and coke tar combustion. This review comprehensively collates the spatial distribution of PAH concentration, their composition, and dominant sources in urban soils of North and South China. Coal and oil combustion contribute more to total PAHs in North China while vehicle emissions and biomass combustion contribute more in South China. This regional difference suggests that PAH pollution in urban soils is a side-effect of a combination of regional development levels and human activities, which differ between North and South China. Risk assessment based on the benzo[a]pyrene toxicity equivalent factor indicates that the concentration of PAHs is low in most parts of China; however, several sensitive areas should receive increased attention. This review aims to provide improved decision-making support toward soil pollution control and monitoring based on the distribution and main pollution sources of PAHs in urban soil of China.

Polycyclic aromatic hydrocarbon and heavy metal contents in the urban soils in southern Poland

In this study, we examined how urban and industrial sprawl has affected the concentrations of polycyclic aromatic hydrocarbons (PAHs) and heavy metals (HMs) in the soils of two towns with different levels of urbanisation and industrial development. The concentrations, sources and spatial distributions of PAHs and Zn, Pb and Cd in the soils of the central, residential and green areas of the second largest town in Poland (Krakow) were compared to similar parameters in analogous areas of Zakopane, a small tourist town. The concentration ranges of the PAHs were much higher in the Krakow (337-59,694 μg kg^-1) than in the Zakopane (55-1180 μg kg^-1) soils. The Krakow soils were also characterised by higher levels of Cd (2.33-4.18 mg kg^-1) and Pb (24.2-82.1 mg kg^-1) than the Zakopane soils, in which the Cd and Pb concentrations amounted to 0.57-2.29 and 17.8-67.8 mg kg^-1, respectively. Positive matrix factorisation (PMF) analysis identified the emission sources of the soil PAHs in both studied towns. In the Krakow soils, the main sources of the PAHs were traffic emissions, petroleum combustion and the steel-industry, while in the Zakopane soils, they were coal and biomass combustion, used for heating houses, followed by vehicle and gasoline emissions. A human health risk assessment, based on the toxic equivalency factors of benzo(a)pyrene (BaP_eq), indicated a low level of PAHs contamination in most of the studied areas. Only in one area in central Krakow the BaP_eq concentration exceeded the permissible value by nine-fold.

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).

Distribution of polychlorinated biphenyls, phthalic acid esters, polycyclic aromatic hydrocarbons and organochlorine substances in the Moscow River, Russia

The purpose of this study was to investigate the levels of polychlorinated biphenyl (PCB), phthalic acid esters (PAE), polycyclic aromatic hydrocarbons (PAH) and organochlorine substances (OCP) in the Moscow River water. Some studies have reported the occurrence of these substances in the soil of the Moscow region; however, no study has yet established an overview for these compounds in the Moscow River water. In this study the Moscow River water contamination with PAEs, PAHs and OCPs was determined. Obtained results were associated with the resident area located on the river bank, and the possible contamination sources were considered. The obtained data were compared with the data on the contamination of the different world-wide rivers. This research indicates the further study necessity of the Moscow region to cover more contaminated sites and environmental compartments.

Association of polycyclic aromatic hydrocarbons (PAHs) and lead co-exposure with child physical growth and development in an e-waste recycling town

Informal e-waste recycling activities results in serious environmental pollution of PAHs. We evaluated the body burden of 16 PAH congeners and potential health risks for children. A total of 167 children from exposed and reference area entered this study. Child blood samples were collected; height, weight, head and chest circumferences were measured. Blood PAH and lead concentrations were determined. The blood median of total PAHs from the exposed group was significantly higher than the reference group (68.53μg/L vs. 26.92μg/L, P<0.01). The major sources of Σ16-PAH and Σ7 carcinogenic-PAH were residence adjacent to e-waste workshop, paternal occupation related to e-waste recycling and house as a workshop. Inverse correlations were observed in the age and milk consumption with these two PAH groups, while a positive association was found between BMI and Σ7 carcinogenic-PAH, and between child height and blood lead. When divided into high and low exposure groups by Σ16-PAH, a significant negative association was found between body height and blood PAHs (β and 95%CI: -3.838, -6.469 to -1.206), while for weight and chest circumferences, negative associations were obtained only in the male subgroup before adjustment. After adjustment by sex, age, child milk products consumption per month and blood lead, child height was negatively associated with Σ16-PAH (β and 95%CI: -3.884, -6.736 to -1.033). Same trends were observed for child chest circumference (β and 95%CI: -1.147, -2.229 to -0.065). We suggest a negative association of PAHs and child height and chest circumference, while the correlation is more obvious in boys.

Polycyclic aromatic hydrocarbons (PAHs) in sediments from lake Lille Lungegårdsvannet in Bergen, western Norway; appraising pollution sources from the urban history

This study aims to determine the temporal character and concentration variability of polycyclic aromatic hydrocarbon (PAH) during the last 5,400 years in urban lake sediments through a combination of dating and chemo-stratigraphical correlation. We investigate the chemical history of the city of Bergen and determine the effect of specific point sources, as well as diffuse sources, and also help assess the risk of remediation plans. By using several organic compounds, metals and cyanide, we demonstrate the more accurate timing of sedimentation. The PAH results display very low concentrations in pre-industrial times, followed by a general increase that is punctuated by a few significant concentration increases. These most probably correspond to urban fires, domestic heating, gaswork activity and most recently due to traffic pollution. At the same depth as a significant rise in concentration from background levels occurred, the high relative occurrence of low-molecular-weight PAH-compounds, such as naphthalene, were replaced by heavier compounds, thus indicating a permanent change in source. The general observation, using ratios, is that the sources have shifted from pre-industrial pure wood and coal combustion towards mixed and petrogenic sources in more recent times. The (14)C dating provides evidence that the sedimentation rate stayed more-or-less constant for 4,500 years (from 7200 to 2700 calibrated years before present (calyr BP)), before isostatic uplift isolated the water body and the sedimentation rate decreased or sediments were eroded. The sediment input increased again when habitation and industrial activities encroached on the lake. The (14)C dating does not provide consistent data in that period, possibly due to the fact that the lake has been used as a waste site throughout the history of Bergen city. Therefore, results from (14)C dating from anthropogenically influenced sediments should be used with caution.

Composition, sources, and potential toxicology of polycyclic aromatic hydrocarbons (PAHs) in agricultural soils in Liaoning, People's Republic of China

Surface soil (0-20 cm) samples (n = 143) were collected from vegetable, maize, and paddy farmland used for commercial crops in Liaoning, China. Sixteen priority polycyclic aromatic hydrocarbons (PAHs) listed in US Environmental Protection Agency were analyzed by high-performance liquid chromatography using a fluorescence detector. The soil concentrations of the 16 PAH ranged from 50 to 3,309 ng/g with a mean of 388 ng/g. The highest concentration of total PAHs found in soil of the vegetable farmland was 448 ng/g in average, followed by maize and paddy with total PAHs of 391 and 331 ng/g, respectively. Generally, the low molecular weight PAHs were more predominant than the high molecular weight PAHs in most of the soils. The evaluation of soil PAH contamination based on the Canadian criterion indicated that only naphthalene, phenanthrene, and pyrene were over the target values in several sampling sites. Isomer pair ratios and principal component analysis indicated that biomass and coal combustion were the main sources of PAHs in this area. And the average value of total B[a]Peq concentration in vegetable soils was higher than paddy and maize soils. We suggest that biomass burning should be abolished and commercial farming should be carried out far from the highways to ensure the safety of food products derived from commercial farming.

Polycyclic aromatic hydrocarbons profile of kitchen dusts

Concentrations and profiles of polycyclic aromatic hydrocarbons (PAHs) were determined in thirty dust samples collected from kitchens that use wood cook system (WCS), kerosene stove cook system (KSCS) and butane gas cook system (BGCS). The total PAHs concentrations ranged from 52 to 497, 39 to 96 and 37 to 155 μg kg(-1) for WCS, KSCS and BGCS respectively. The results indicate predominance of lower molecular weight (2-3 rings) over higher molecular weight PAHs and users of wood cook system are more exposed to higher levels of PAHs than the users of either kerosene cook system or butane gas cook system.

Concentration, distribution and sources of polyaromatic hydrocarbons in soils from the Karst tiankengs, South China

Polycyclic aromatic hydrocarbons (PAHs) were investigated in the surface soils from Dashiwei and Datuo Karst tiankengs, Guangxi Province, South China. Concentrations of total PAHs ranged from 16.93 ng g(-1) to 190 ng g(-1) with a mean of 58.29 ng g(-1). In Dashiwei more PAHs were concentrated than in Datuo (mean 74.42 ng g(-1) > 42.15 ng g(-1)). Dashiwei and Datuo accounted for the majority of all PAHs concentrated in the lower location through increased rates (58% and 37%) from the upper to lower geographical levels, respectively. Dashiwei presented the stronger trapping ability for heavier molecular weights on the tiankeng floor with a concentration increase rate of 167% when compared to that of the lighter molecular weights (which had a concentration increase of rate 6%), which was in contrast to the Datuo with a concentration increase rate of 37% for lighter molecular weights and 31% for heavier molecular weights. In Dashiwei, it was found that the ratio of heavier PAH compound molecular weight resulted in its higher precipitation recording on the tiankeng floor. The differentia between two tiankengs, therefore, are related to their environmental characteristics and the PAHs physiochemical properties. The analytical result from the PAHs indicators suggest that a petrogenic source was dominant in the area studied. Therefore, the karst tiankeng has the potential to act as a geophysical well for PAHs deposition, especially for the heavier molecular weighted PAH.

Distribution of polycyclic aromatic hydrocarbons in Datuo karst Tiankeng of South China

Levels of polycyclic aromatic hydrocarbons (PAHs) were measured in surface soils of Datuo karst Tiankeng (large sinkholes) in South China with the use of a gas chromatography-mass spectroscopy (GC-MS) system. This paper provides data on the levels and distribution of PAHs from the top to the bottom of the Datuo karst Tiankeng. The results showed that the sum of the 16 EPA priority PAHs from the sampled locations from top to bottom had a relative increment in PAHs concentration. summation operatorPAHs ranged from 16.93 ng/g to 68.07 ng/g with a mean concentration of 42.15 ng/g. The correlated results showed the bottom of the large sinkhole, which accounts for the higher concentrations, probably acts like a trap for the PAHs. Thus, the low evaporation rate at the bottom may play a key role in controlling the high concentration of PAHs at the bottom.

Residue level of polycyclic aromatic hydrocarbons in Japanese paddy soils from 1959 to 2002

The residue level of 21 polycyclic aromatic hydrocarbons (PAHs) and the temporal changes in this level were investigated in paddy soils collected from particular experimental sites in Japan from 1959 to 2002. The average total PAH concentration in all the samples was 496 microg kg(-1), and it ranged from 52.9 to 2180 microg kg(-1). The residue level of the PAHs was the highest during the 1960s, rapidly decreased during the 1970s, and remained almost constant thereafter. Relatively high PAH concentrations were observed in soils from areas that experienced heavy snowfall and that had relatively low air temperature. The predominant PAHs were phenanthrene, fluoranthene, naphthalene, and pyrene, and their concentration overall and in relation to that of the total PAHs decreased each year since the 1960s. Similarities in the PAH profiles among the locations were determined using the concentration correlation matrix and cluster analysis, and ratios of the levels of specific PAH pairs were also calculated to determine their origin. The collected data suggested that the origins of soil PAHs changed chronologically from the burning of agricultural wastes such as stubble before the mid-1970s to the combustion of fossil fuel and its secondary products after the mid-1970s.

Soil pollution by PAHs in urban soils: a comparison of three European cities

The purpose of this study was to determine the degree of contamination with polycyclic aromatic hydrocarbons (PAHs) in samples of urban soil from three European cities: Glasgow (UK), Torino (Italy) and Ljubljana (Slovenia). Fifteen PAHs (naphthalene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenzo[a,h]anthracene, benzo[g,h,i]perylene, indeno[1,2,3-c,d]pyrene) were measured in urban soil samples, using harmonised sampling, sample extraction and analyte quantification methods. Although the mean concentration of each PAH in urban soils of each city showed a wide range of values, high levels of contamination were only evident in Glasgow, where the sum of concentrations of 15 PAHs was in the range 1487-51,822 microg kg(-1), cf. ranges in the other two cities were about ten-fold lower (89.5-4488 microg kg(-1)). The three predominant PAHs were phenanthrene, fluoranthene and pyrene, with the sum of these compounds about 40% of the total PAH content. These data, together with some special molecular indices based on ratios of selected PAHs, suggest pyrogenic origins, especially motor vehicle exhausts, to be the major sources of PAHs in urban soils of the three cities. The largest concentrations for PAHs were often found in sites close to the historic quarters of the cities. Overall, the different climatic conditions, the organic carbon contents of soil, and the source apportionment were the dominant factors affecting accumulation of PAHs in soil.

Polychlorinated biphenyls (PCBs) in soils of the Moscow region: concentrations and small-scale distribution along an urban-rural transect

In soils of the Moscow region, we examined PCB concentrations in bulk samples and aggregate fractions. Topsoils under grassland and forest at five locations along a southeast-bound transect from Moscow and at a northeastern background location (grassland only) were analysed. We collected aggregates >1 cm and fractionated them into interior and exterior portions and also analysed the remaining soil without the aggregates >1 cm. The concentrations of the sum of 17 PCBs (sigma17PCBs) in 35 bulk soil samples ranged from 3.1 to 42 microg kg(-1). This was 48-61% of the sigma33PCBs determined in 23 selected samples. The congeners 138(+158), 101 and 52 were most abundant. All PCB concentrations and the degree of chlorination declined with increasing distance from Moscow. The PCBs were accumulated in the aggregate exterior (on average 146% of the sigma17PCBs in bulk soil). We conclude that the ecotoxicological risk of PCBs in soils may not be properly assessed with the conventional bulk soil analysis.