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

Comparative study on anthropogenic impacts on soil PAHs: Accumulation and source apportionment in tourist and industrial cities in Hebei Province, China

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous organic contaminants in urban soils. The accumulation and source identifications of PAHs within a city have been frequently studied. However, impacts of urbanization development modes on PAHs accumulation patterns by taking a city as a whole have been seldom reported. Four cities with two development modes in Hebei province, Chengde and Zhangjiakou (tourist cities) and Handan and Tangshan (industrial cities), were selected. The concentrations of 16 priority PAHs in soils in the study areas were investigated. The results showed that the average concentrations of Σ16PAHs in Handan (2517 μg/kg) and Tangshan (2256 μg/kg) were more than twice of those in Chengde (696 μg/kg) and Zhangjiakou (926 μg/kg) approximately. Lines of evidence, provided by a combination of diagnostic ratios, pairwise correlation, and PMF methods, revealed that the dominant sources of PAHs in either city were industrial emission, vehicle emission, and petrogenic/biogenic process but with different proportions. Linear fittings based on Bayesian kernel machine regression analysis (BKMR) were constructed to illustrate the impact of industrialization on PAHs accumulation. The probability of excessing the 10 % (376 μg/kg) and 50 % (1138 μg/kg) of current ∑16PAHs would be higher than 90 % given the gross industrial production per unit area >5.00 × 106 and 20.5 × 106 CNY/km2, respectively. The proposed threshold values of industrialization are of significance for determining industrial structure and proportion in urban management.

Introducing a land use-based weight factor in regional health risk assessment of PAHs in soils of an urban agglomeration

The high heterogeneity of land uses in urban areas has led to large spatial variations in the contents and health risks of polycyclic aromatic hydrocarbons (PAHs) in soils. A land use-based health risk assessment (LUHR) model was proposed for soil pollution on a regional scale by introducing a land use-based weight factor, which considered the differences in exposure levels of soil pollutants to receptor populations between land uses. The model was applied to assess the health risk posed by soil PAHs in the rapidly industrializing urban agglomeration of Changsha-Zhuzhou-Xiangtan Urban Agglomeration (CZTUA). The mean concentration of total PAHs (∑PAHs) in CZTUA was 493.2 μg/kg, and their spatial distribution was consistent with emissions from industry and vehicles. The LUHR model suggested the 90th percentile health risk value was 4.63 × 10-7, which was 4.13 and 1.08 times higher than those of traditional risk assessments that have adopted adults and children as default risk receptors, respectively. The risk maps of LUHRs showed that the ratios of the area exceeding the risk threshold (1 × 10-6) to the total area were 34.0 %, 5.0 %, 3.8 %, 2.1 %, and 0.2 % in the industrial area, urban green space, roadside, farmland, and forestland, respectively. The LUHR model back-calculated the soil critical values (SCVs) for ∑PAHs under different land uses, resulting in values of 6719, 4566, 3224, and 2750 μg/kg for forestland, farmland, urban green space, and roadside, respectively. Compared with the traditional health risk assessment models, this LUHR model identified high-risk areas and drew risk contours more accurately and precisely by considering both the spatial variances of soil pollution and their exposure levels to different risk receptors. This provides an advanced approach to assessing the health risks of soil pollution on a regional scale.

Spatial distribution, sources identification, and health risk assessment polycyclic aromatic hydrocarbon compounds and polychlorinated biphenyl compounds in total suspended particulates (TSP) in the air of South Pars Industrial region-Iran

South Pars Industrial Energy Zone, located in the southwest of Iran along the Persian Gulf coast, encompasses many industrial units in the vicinity of urban areas. This research study investigated the effects of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) on human health and the environment. Suspended particulate matters (SPM) in the air sampled, in summer and winter 2019, from ten stations next to industrial units and residential areas. The samples were analyzed by gas chromatography-mass spectrometry (GC-MS). Spatial distribution maps of pollutants in the region were prepared using GIS software. The highest carcinogenic risk due to PAHs and PCBs measured as ([Formula: see text]) and ([Formula: see text], respectively. According to the US Environmental Protection Agency limit ([Formula: see text]), the cancer risks from PAH compounds were significant and need further investigation. The PCB cancer risks were within acceptable ranges. The highest adsorption ratios for PAHs were obtained through skin and PCBs by ingestion. The maximum measured non-carcinogenic hazard indexes (HI) turned out to be 0.037 and 0.023 for PAH and PCB, respectively, and were reported as acceptable risks. The predominant source of PAH in industrial areas was liquid fossil combustion, and in urban areas replaced by coal-wood-sugarcane combustion. Petrochemical complexes, flares, power plants (69%), electric waste disposal sites, and commercial pigments (31%) were reported as PCB sources. Industries activities were the most effective factors in producing the highest level of carcinogenic compounds in the region, and it is necessary to include essential measures in the reform programs.

Seasonal assessment of the distribution, source apportionment, and risk of water-contaminated polycyclic aromatic hydrocarbons (PAHs)

The research aims to evaluate the seasonal differences in the distribution, source, and risks of water-contaminated PAHs. The PAHs were extracted by the liquid-liquid method and analyzed with GC-MS, and a total of eight PAHs were detected. There was a percentage increase in the average concentration of the PAHs from the wet to the dry season in the range of 20 (Anthracene)-350 (Pyrene)%. Total PAHs (∑PAHs) range from 0.31 to 1.23 mg/l in the wet period and from 0.42 to 1.96 mg/l in the dry period. The distribution of the average PAHs in mg/l showed that Fluoranthene ≤ Pyrene < Acenaphthene < Fluorene < Phenanthrene < Acenaphthylene < Anthracene < Naphthalene in wet period and while Fluoranthene < Acenaphthene < Pyrene < Fluorene < Phenanthrene < Acenaphthylene < Anthracene < Naphthalene in the dry period. The children were exposed to non-carcinogenic risk through non-dietary ingestion due to the accumulative effect (HI) of the PAHs in the dry period. Furthermore, the naphthalene was responsible for ecological and carcinogenic risk in the wet period, while the fluorene, phenanthrene, and anthracene were responsible for ecological and carcinogenic risk in the dry period. However, while adults and children are both susceptible to carcinogenic risk through the oral channel during the dry period, only children are susceptible to non-carcinogenic risk through this pathway. The multivariate statistical analysis revealed the influence of physicochemical parameters on the detected PAHs and also showed the PAHs' sources to be mainly combustion, pyrolysis, and vehicular emission.

Influence of temperature and precipitation on the fate of polycyclic aromatic hydrocarbons: simulation experiments on peat cores from a typical alpine peatland in Central China

The corresponding relationships between temperature, precipitation, and polycyclic aromatic hydrocarbon (PAH) concentration in a typical ombrotrophic peatland in Dajiuhu, Shennongjia, were quantitatively characterized by field sampling tests validated with simulation experiments. The PAH concentrations of peat cores in Dajiuhu peatland ranged from 262 to 977 ng·g^-1, with a mean value of 536 ± 284 ng·g^-1. PAHs were mainly composed of 2-3 ring PAHs, accounting for 31.7% ± 2.00% and 31.7% ± 5.00%, respectively. The concentration of PAHs in peat cores showed a significant decrease with increasing temperature, while the low molecular weight PAHs (LMW-PAHs) were more sensitive to temperature changes compared to the high molecular weight PAHs (HMW-PAHs). Besides, with the increase of quantity and velocity of leaching liquid, PAHs in peat were first transferred in the form of attached large-size particles and then gradually entered the aqueous phase. According to the IPCC projections of global warming, Dajiuhu peatland will release 956 ± 26.3 kg·°C^-1 PAHs into gas phase during 2030-2052, and a conservative projection based on local temperature trends showed that 459 ± 12.6 kg·°C^-1 PAHs will be released into gas phase by 2047 in Dajiuhu peatland. The projected release fluxes of PAHs in Dajiuhu peatland with precipitation volume and precipitation velocity are 381 ± 201 kg·100 mm^-1 and 1052 ± 167 kg·min·mL^-1, respectively, which are primarily from peat into particulate and aqueous phase.

Risk Control Values and Remediation Goals for Benzo[a]pyrene in Contaminated Sites: Sectoral Characteristics, Temporal Trends, and Empirical Implications

Benzo[a]pyrene (BaP) is a highly carcinogenic pollutant of global concern. There is a need for a comprehensive assessment of regulation decisions for BaP-contaminated site management. Herein, we present a quantitative evaluation of remediation decisions from 206 contaminated sites throughout China between 2011 and 2021 using the cumulative distribution function (CDF) and related statistical methodologies. Generally, remediation decisions seek to establish remediation goals (RGs) based on the risk control values (RCVs). Cumulative frequency distributions, followed non-normal S-curve, emerged multiple nonrandom clusters. These clusters are consistent with regulatory guidance values (RGVs), of national and local soil levels in China. Additionally, priority interventions for contaminated sites were determined by prioritizing RCVs and identifying differences across industrial sectors. Notably, we found that RCVs and RGs became more relaxed over time, effectively reducing conservation and unsustainable social and economic impacts. The joint probability curve was applied to model decision values, which afforded a generic empirically important RG of 0.57 mg/kg. Overall, these findings will help decision-makers and governments develop appropriate remediation strategies for BaP as a ubiquitous priority pollutant.

Anchoring ZnO on spinel cobalt ferrite for highly synergic sono-photo-catalytic, surfactant-assisted PAH degradation from soil washing solutions

In this study, the photocatalytic activity of ZnO was effectively improved via its combination with spinel cobalt ferrite (SCF) nanoparticles. The catalytic performance of ZnO@SCF (ZSCF) was investigated in coupling with UV irradiation and ultrasound (US), as a heterogeneous sono-photocatalytic process, for the decontamination of phenanthrene (PHE) from contaminated soil. Soil washing tests were conducted in a batch environment, after extraction assisted by using Tween 80. Several characterization techniques such as XRD, FESEM-EDS, BET, TEM, UV-vis DRS, PL and VSM were utilized to determine the features of the as-prepared catalysts. ZSCF showed an excellent catalytic activity toward degradation of PHE in the presence of US and UV with a significant synergic effect. It was found that more than 93% of PHE (35 mg/L) and 87.5% of TOC could be eliminated by the integrated ZSCF/US/UV system under optimum operational conditions (pH: 8.0, ZSCF: 1.5 g/L, UV power: 6.0 W and US power: 70 W) within 90 min of reaction. After five times of use, ZSCF illustrated good reusability in the decontamination of PHE (87%) and TOC (79%). Quenching tests revealed the contribution of h⁺, HO^• and e^- species during PHE degradation over ZSCF/UV/US and an S-scheme photocatalytic mechanisms was proposed for the possible charge transfer routes under the ZSCF system. This study provides the important role of SCF in enhancing the ZnO photocatalytic activity due to its high performance, easy recovery and excellent durability, which it make an efficient and promising catalyst in environmental clean-up applications.

Integrated Insights into Source Apportionment and Source-Specific Health Risks of Potential Pollutants in Urban Park Soils on the Karst Plateau, SW China

Polycyclic aromatic hydrocarbons (PAHs) and heavy metal(loid)s (HMs) pose risks to environmental and human health. Identification of priority control contaminants is important in guiding the management and control of these synchronous pollutants. A total of 247 soil samples were collected from 64 urban parks in the karst plateau city of Guiyang in SW China to determine the concentrations, spatial distributions, and health risks of PAHs and HMs. The results indicate that dibenz(ah)anthracene and benzo(a)pyrene are the main PAHs species of high ecological risk, and Cr, Mn, and Ni pose elevated ecological risk among the HMs. Four sources were identified for PAHs (biomass burning, coke oven, traffic sources, and coal burning) and HMs (traffic sources, coal burning, industrial sources, and natural sources). The non-carcinogenic risk (NCR) and total carcinogenic risk (TCR) of PAHs were all determined to be negligible and at acceptable levels, several orders of magnitude below those of HMs. The NCR and TCR values of HMs were relatively high, especially for children (11.9% of NCR > 1; 79.1% of TCR > 10-4). Coal burning and natural sources make the greatest contributions to the NCR and TCR values from karst park soils in Guiyang. Considering HMs bioavailability, NCR and TCR values were rather low, due to the high residual HM fractions. Integrated insights into source specific ecological and human health risk indicate future directions for management and control of synchronous PAH and HM pollution, particularly for karst plateau areas.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12403-023-00534-3.

Target and suspect analysis of liquid crystal monomers in soil from different urban functional zones

Recent studies have reported the occurrence of liquid crystal monomers (LCMs) in sediment, indoor dust, hand wipes, and human serum samples; however, information regarding their contamination status in soil is currently unavailable. The concentrations of 39 target LCMs were determined in n = 96 surface soil samples collected from five different urban functional zones including agricultural, scenic, industrial, commercial, and residential zones. We observed that 76 of 96 surface soil samples contained at least 19, 13, 16, 19, and 14 of the 39 target LCMs that were detectable in samples from agricultural, scenic, industrial, commercial, and residential zones, respectively. The LCMs in the samples from the agricultural zone exhibited the highest mean concentrations of 12.9 ng/g dry weight (dw), followed by those from commercial (5.23 ng/g dw), residential (3.30 ng/g dw), industrial (2.48 ng/g dw), and scenic zones (0.774 ng/g dw). Furthermore, strong and statistically significant (p < 0.05) correlations were observed for several pairs of LCMs (3cH2B vs. 5bcHdFB in the agricultural zone; 5bcHdFB vs. 2bcHdFB, 5bcHdFB vs. 3cH2B in the commercial zone; 5bcHdFB vs. 2bcHdFB in the industrial zone), indicating that they might have similar commercial applications and sources. Based on a newly established database containing 1173 LCMs, suspect screening was applied to discover other LCMs in these 96 soil samples using gas chromatograph coupled with quadrupole-time-of-flight mass spectrometry (GC-QTOF/MS). We tentatively identified 51 LCM formulas with 69 chemical structures. Collectively, this study provides the first evidence for the occurrence of LCMs in soil samples, and suggests that LCMs could be widely distributed across all five urban functional zones.

Toxicity determination, pollution source delineation, and microbial diversity evaluation of PAHs-contaminated sediments for an urban river

The Feng-Sang River is a metropolitan river in Kaohsiung City, Taiwan. In this study, Feng-Sang River sediments were analyzed to investigate the distributions and sources of polycyclic aromatic hydrocarbons (PAHs). The Sediment Quality Guidelines (SQGs), potentially carcinogenic PAHs (TEQcarc ), and toxic equivalence quotient (TEQ) were applied to evaluate influences of PAHs on ecosystems and microbial diversities. Results indicate that PAHs concentrations varied between seasons and locations. The concentrations of ∑16 PAHs ranged from 73.6 to 603.8 ng/kg in dry seasons and from 2.3 to 199.3 ng/kg in wet seasons. This could be because of the flushing effect during wet seasons, which caused the movement and dilution of the PAH-contaminated sediments. Diagnostic ratio analysis infers that high PAHs levels were generated by combustion processes and vehicle traffic, and results from multivariate descriptive statistical analysis also demonstrate that the vehicular traffic pollution could be the major emission source of PAHs contamination. Comparisons of PAHs with SQGs indicate that PAHs concentrations in sediment were below the effects range low (ERL) values, and thus, the immediate threat to organisms might not be significant. The diagnostic ratio analyses are effective methods for PAH source appointment. The metagenomic assay results imply that sediments contained essential microbial species with eminent diversity. The detected PAH-degrading bacteria (Desulfatiglans, Dechloromonas, Sphingomonas, Methylobacterium, Rhodobacter, Clostridium, and Exiguobacterium) played a key role in PAHs biotransformation, and Dechloromonas and Rhodobacter had a higher relative abundance. Results of microbial diversity analyses indicate that the contaminated environment induced the changes of governing microbial groups in sediments. PRACTITIONER POINTS: Diagnostic ratio analyses are effective methods for PAHs source appointment. Microbial composition in sediments are highly affected by anthropogenic pollution. Combustion and vehicle traffic contribute to urban river sediments pollution by PAHs. Dechloromonas and Rhodobacter are dominant PAHs-degrading bacteria in sediments.

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.

Source identification and toxicity apportionment of polycyclic aromatic hydrocarbons in surface soils in Beijing and Tianjin using a PMF-TEQ method

Beijing and Tianjin are two of the largest cities in northern China with high population densities and highly developed manufacturing industries. In the past decade, some authors have reported their PAH concentrations in surface soils, identified their sources and quantitatively reported their health risks. However, the contributions of different PAH sources to their toxicity have not been reported thus far. In this study, we reviewed the PAH concentrations, contributions of different sources to the toxicity, and cancer risks in soils from different land use types found within Beijing and Tianjin from data gathered by 41 studies. The total PAH concentration varied in the range of 175.7–1989.0 ng g-1 with a higher median PAH concentration detected in urban soils (789.7 ng g-1), followed by suburban soils (647.3 ng g-1) and rural soils (390.8 ng g-1). Source identification using diagnostic ratios and principal component analysis (PCA) suggested that the PAHs in all three land use types mainly originated from biomass and coal combustion, vehicular emissions, and petrogenic processes with contributions varying from 13% to 62%. Furthermore, results from a positive matrix factorization (PMF) model suggested that vehicular emissions and coal combustion in urban soils, and the vehicular emissions, coal combustion and biomass combustion in suburban and rural soils dominated the total PAH concentrations (>85%). These results were consistent with those of the PCA model. Results of the additional toxicity apportionment performed using the PMF model suggested that vehicular emissions and coal combustion contributed the most to the toxic equivalent quantity for Benzo(a)Pyrene (BaPTEQ) and, by extension, to the carcinogenic potencies. The incremental lifetime cancer risk (ILCR) values suggested a low risk level for adults exposed to PAHs in the different land use types found within Beijing and Tianjin.

Primary and Secondary Emissions of VOCs and PAHs in Indoor Air from a Waterproof Coal-Tar Membrane: Diagnosis and Remediation

Primary and secondary emissions of volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs) from a waterproof coal tar membrane and their effect on the indoor air quality were investigated through a case study in a residential building situated in Madrid, Spain. The air contaminants were analyzed in situ using photoionization method and several samples of contaminants were taken using three sorbents: activated carbon, XAD2 and Tenax GR. It was found that various VOCs such as toluene, p- and m-Xylene, PAHs such as naphthalene, methyl-naphthalenes, acenaphthene, acenaphthylene, phenanthrene and fluorine, volatile organic halogens including chloroform and trichlorofluoromethane, and alkylbenzene (1,2,4-trimethylbenzene) were found at concentrations, which exceeded the limits established by international and national agencies (WHO, EPA, OSHA). Some of the above organic compounds were found also in the samples of construction and building materials, which were obtained at different heights and places. The analysis of possible sources of the contaminants pointed at the original coal-tar membrane, which was applied on the terrace to be waterproof. During a posterior reparation the membrane was coated with a new one that hindered dissipation of emitted contaminants. The contaminants leached out and were absorbed by construction materials down in the dwelling. These materials then acted as secondary emission sources. To remediate the emission problem as the contaminated materials were removed and then a ventilation system was installed to force the gasses being emitted from the rest of contaminated slab outside. Follow-up has validated the success of the remediation procedure.

Performance of Fly Ash-Based Inorganic Polymer Mortar with Petroleum Sludge Ash

Petroleum sludge is a waste product resulting from petroleum industries and it is a major source of environmental pollution. Therefore, developing strategies aimed at reducing its environmental impact and enhance cleaner production are crucial for environmental mortar. Response surface methodology (RSM) was used in designing the experimental work. The variables considered were the amount of petroleum sludge ash (PSA) in weight percent and the ratio of sodium silicate to sodium hydroxide, while the concentration of sodium hydroxide was kept constant in the production of geopolymer mortar cured at a temperature of 60 °C for 20 h. The effects of PSA on density, compressive strength, flexural strength, water absorption, drying shrinkage, morphology, and pore size distribution were investigated. The addition of PSA in the mortar enhanced the mechanical properties significantly at an early age and 28 days of curing. Thus, PSA could be used as a precursor material in the production of geopolymer mortar for green construction sustainability. This study aimed to investigate the influence of PSA in geopolymer mortar.