Enhancing soil petrochemical contaminant remediation through nutrient addition and exogenous bacterial introduction.

Biostimulation (providing favorable environmental conditions for microbial growth) and bioaugmentation (introducing exogenous microorganisms) are effective approaches in the bioremediation of petroleum-contaminated soil. However, uncertainty remains in the effectiveness of these two approaches in practical application. In this study, we constructed mesocosms using petroleum hydrocarbon-contaminated soil. We compared the effects of adding nutrients, introducing exogenous bacterial degraders, and their combination on remediating petroleum contamination in the soil. Adding nutrients more effectively accelerated total petroleum hydrocarbon (TPH) degradation than other treatments in the initial 60 days' incubation. Despite both approaches stimulating bacterial richness, the community turnover caused by nutrient addition was gentler than bacterial degrader introduction. As TPH concentrations decreased, we observed a succession in microbial communities characterized by a decline in copiotrophic, fast-growing bacterial r-strategists with high rRNA operon (rrn) copy numbers. Ecological network analysis indicated that both nutrient addition and bacterial degrader introduction enhanced the complexity and stability of bacterial networks. Compared to the other treatment, the bacterial network with nutrient addition had more keystone species and a higher proportion of negative associations, factors that may enhance microbial community stability. Our study demonstrated that nutrient addition effectively regulates community succession and ecological interaction to accelerate the soil TPH degradation.

Microbial diversity and metabolic pathways linked to benzene degradation in petrochemical-polluted groundwater.

The rapid advance in shotgun metagenome sequencing has enabled us to identify uncultivated functional microorganisms in polluted environments. While aerobic petrochemical-degrading pathways have been extensively studied, the anaerobic mechanisms remain less explored. Here, we conducted a study at a petrochemical-polluted groundwater site in Henan Province, Central China. A total of twelve groundwater monitoring wells were installed to collect groundwater samples. Benzene appeared to be the predominant pollutant, detected in 10 out of 12 samples, with concentrations ranging from 1.4 µg/L to 5,280 µg/L. Due to the low aquifer permeability, pollutant migration occurred slowly, resulting in relatively low benzene concentrations downstream within the heavily polluted area. Deep metagenome sequencing revealed Proteobacteria as the dominant phylum, accounting for over 63 % of total abundances. Microbial α-diversity was low in heavily polluted samples, with community compositions substantially differing from those in lightly polluted samples. dmpK encoding the phenol/toluene 2-monooxygenase was detected across all samples, while the dioxygenase bedC1 was not detected, suggesting that aerobic benzene degradation might occur through monooxygenation. Sequence assembly and binning yielded 350 high-quality metagenome-assembled genomes (MAGs), with 30 MAGs harboring functional genes associated with aerobic or anaerobic benzene degradation. About 80 % of MAGs harboring functional genes associated with anaerobic benzene degradation remained taxonomically unclassified at the genus level, suggesting that our current database coverage of anaerobic benzene-degrading microorganisms is very limited. Furthermore, two genes integral to anaerobic benzene metabolism, i.e, benzoyl-CoA reductase (bamB) and glutaryl-CoA dehydrogenase (acd), were not annotated by metagenome functional analyses but were identified within the MAGs, signifying the importance of integrating both contig-based and MAG-based approaches. Together, our efforts of functional annotation and metagenome binning generate a robust blueprint of microbial functional potentials in petrochemical-polluted groundwater, which is crucial for designing proficient bioremediation strategies.

Microbial functional heterogeneity induced in a petroleum-polluted soil profile.

Microbial taxonomic diversity declines with increasing stress caused by petroleum pollution. However, few studies have tested whether functional diversities vary similarly to taxonomic diversity along the stress gradient. Here, we investigated soil microbial communities in a petrochemically polluted site in China. Total petroleum hydrocarbon (TPH) concentrations were higher in the middle (2-3 m) and deep soil layer (3-5 m) than in the surface soil layer (0-2 m). Accordingly, microbial taxonomic α-diversity was decreased by 44% (p < 0.001) in the middle and deep soil layers, compared to the surface soil layer. In contrast, functional α-diversity decreased by 3% (p < 0.001), showing a much better buffering capacity to environmental stress. Differences in microbial taxonomic and functional ß-diversities were enlarged in the middle and deep soil layers, extending the Anna Karenina Principle (AKP) that a community adapts to stressful environments in its own way. Consistent with the stress gradient hypothesis, we revealed a higher degree of network connectivity among microbial species and genes in the middle and deep soil layers compared to the surface soil layer. Together, we demonstrate that microbial functionality is more tolerant to stress than taxonomy, both of which were amenable to AKP and the stress gradient hypothesis.

[Effects of Source Depletion on Vapor Intrusion Risk Assessment].

The current regulatory site investigation employs the J&E model to predict vapor intrusion risk. However, the J&E model assumes that the source concentration is constant for a given exposure period, which is not consistent with the actual site source under depletion. In this study, we compared the differences between the J&E model (constant source), SD source depletion model, and RBCA source depletion model for predicting indoor concentration variation as well as the risk levels during the exposure period with a case study in Beijing. The results showed that the source and indoor air concentrations predicted by the SD and RBCA models showed exponential decreases, whereas those predicted by the J&E model maintained high concentrations throughout the exposure period, which greatly overestimated the risk. The RBCA predicted source depletion at the fastest rate, but the predicted indoor air concentrations were still lower than those of the SD model, which was related to the fact that the RBCA did not consider the effect of buildings on source depletion and did not follow mass conservation. Further, the sensitivity analysis showed that the pressure difference (dP) had the greatest influence on the source concentration in the SD model. For the calculated carcinogenic risk and hazard quotients, the J&E constant source model, the SD source depletion model, and the RBCA source depletion model were ranked in descending order. The results indicated that in general the J&E model was too conservative, the RBCA model may have underestimated risk, and the SD model was more suitable for quantifying vapor intrusion risk in reality.

Petroleum pollution changes microbial diversity and network complexity of soil profile in an oil refinery.

Introduction: Petroleum pollution resulting from spills and leakages in oil refinery areas has been a significant environmental concern for decades. Despite this, the effects of petroleum pollutants on soil microbial communities and their potential for pollutant biodegradation still required further investigation. Methods: In this study, we collected 75 soil samples from 0 to 5 m depths of 15 soil profiles in an abandoned refinery to analyze the effect of petroleum pollution on soil microbial diversity, community structure, and network co-occurrence patterns. Results: Our results suggested soil microbial a-diversity decreased under high C10-C40 levels, coupled with significant changes in the community structure of soil profiles. However, soil microbial network complexity increased with petroleum pollution levels, suggesting more complex microbial potential interactions. A module specific for methane and methyl oxidation was also found under high C10-C40 levels of the soil profile, indicating stronger methanotrophic and methylotrophic metabolic activities at the heavily polluted soil profile. Discussion: The increased network complexity observed may be due to more metabolic pathways and processes, as well as increased microbial interactions during these processes. These findings highlight the importance of considering both microbial diversity and network complexity in assessing the effects of petroleum pollution on soil ecosystems.

Sini powder with paroxetine ameliorates major depressive disorder by modulating circadian rhythm: A randomized, double-blind, placebo-controlled trial.

Circadian rhythm disorder is a significant risk factor for mental diseases, and the recovery of circadian rhythm function has gradually become a signal of effective antidepressant therapy. Sini powder (SNP) is a classical, traditional Chinese formula for depression treatment. However, few clinical reports have been recorded. This randomized, double-blinded, controlled trial (ChiCTR1900022700) aimed to explore the efficacy of SNP on depression via regulating circadian rhythm. In total, 36 patients with major depressive disorder (MDD) were enrolled for 4-weeks medication and 6-weeks follow-up. HAMD-24 score and circadian rhythm index, including dim light melatonin onset (DLMO) and phase angle difference (PAD), were included in the assessment. DLMO and PAD were statistically significant in the SNP group after 4 weeks of treatment (p < .05) and with greater improvement in DLMO (p = .03). In addition, DLMO and the HAMD-24 score showed a positive correlation (p < .05); the HAMD-24 score degree decreased significantly over time (p < .001). Similarly, interaction effects were shown significantly between group and time (p = .049). The duration of SNP supplementation was relatively short, and the sample size was relatively small. SNP granules combined with paroxetine tablets have definite efficacy in improving the circadian rhythms of MDD patients, reflecting the therapeutic advantages of traditional Chinese medicine as antidepressants.

Effect of vapour-solid interfacial adsorption on benzene multiphase partition and its implication to vapour exposure assessment of contaminated soil in arid area.

The partitioning of volatile organic compounds (VOCs) in soil multiphase system is a critical process for vapour intrusion, however, the importance of vapour-solid interface adsorption doesn't receive the due attention, which causes the exposure assessment too conservative particularly in arid conditions. This paper proposed a multiphase partitioning equilibrium (MPE) model establishing the quantitative relationship between VOCs and its various partitioning phases in soil, including solid-liquid interface adsorption phase, vapour phase and dissolved phase and vapour-solid interface adsorption phase. Taking benzene as the targeted pollutant, the model was found in good agreement with the experimental data while the errors were within one magnitude basically. The role of vapour-solid interface adsorption under different soil moisture conditions was also investigated by the model. The results reveals that a) soil moisture is the conspicuous controlling factor that affects the benzene partitioning in soil; b) vapour-solid interface adsorption dominates benzene uptake when soil relative saturation (RS) is under 20% among three typical soils; c) as adsorption by soil minerals (vapour-solid interface adsorption) is reduced by increasing amounts of humidity (RS > 20%), uptake by partitioning into the soil organic matter (OM) increasingly becomes a controlling factor; d) the common sense that vapour concentration of benzene is particularly high with low level of RS may not occur since the vapour-solid interface adsorption dominates benzene uptake in arid environment. The MPE model is suitable for prediction of VOCs partitioning and vapour exposure risk assessment of contaminated soil in arid area.

Soil nutrient variability mediates the effects of erosion on soil microbial communities: results from a modified topsoil removal method in an agricultural field in Yunnan plateau, China.

Soil erosion can affect the nature and distribution of soil carbon and nutrients, directly and indirectly influencing microbially facilitated processes of mineralization, ammoniation, and nitrification, thus affecting soil nutrients cycling. However, little is known about how soil erosion affects soil microorganisms. Since 2012, we conducted a modified soil erosion simulation experiment of topsoil removal method in an agricultural field to simulate erosion depths of 5, 10, 20, 30, and 40 cm versus a control (0 cm). The results showed that Proteobacteria, Bacteroidetes, Acidobacteria, Chloroflexi, Actinobacteria, and Firmicutes were the dominant soil microbial (here: Bacteria and Archaea) phyla, and Acidothermus, Candidatus Solibacter, Acidibacter, Bryobacter, and Actinospica were the dominant genera in all samples. The relative abundance of Proteobacteria, Acidobacteria, Actinobacteria, Planctomycetes, Thaumarchaeota, Acidothermus, Candidatus Solibacter, Acidibacter, Bryobacter, Actinospica, and Rhodanobacter decreased with the increase of erosion depths, while Chloroflexi and Firmicutes increased with the increase of erosion depths. Soil microbial community structure was altered significantly at 30- and 40-cm soil erosion depth in comparison to control. Soil nutrient variability caused by soil erosion had a greater impact on soil microbial community composition than that of soil mechanical composition. Soil erosion indirectly affected microbial community composition through negative effects on soil available potassium, total phosphorus, total nitrogen, and sand content. We thus highlight the importance of soil nutrients monitoring in different soil erosion levels to make the proper ecological restoration strategies to improve soil environment which soil microorganisms depend on.

Investigating the Preventive Effects of 99Tc-Methylenediphosphonate on a Glucocorticoid-Induced Osteoporosis Rabbit Model.

BACKGROUND AND OBJECTIVE: Osteoporosis is a worldwide healthcare challenge. Conventional medications for osteoporosis prevention are not clinically effective or associated with gastrointestinal tract adverse effects. The present study aimed to comparatively investigate the effects of technetium-99 conjugated with methylene diphosphonate (99Tc-MDP) and calcium carbonate and alendronate on the prevention and treatment of osteoporosis in glucocorticoid-induced osteoporosis rabbit model through evaluating bone alkaline phosphatase (B-ALP), TRAP-5b levels and histopathological parameters. METHODS: Forty healthy female New Zealand rabbits were randomly divided into five groups (each n=8), including control group (Control Group), osteoporosis model group (GIO Group), osteoporosis model + 99Tc-MDP group (99Tc-MDP Group), osteoporosis model + alendronate group (Alendronate Group), and osteoporosis model + calcium carbonate group (calcium carbonate Group). Animals in each group were treated with corresponding interventions for 14 weeks. The blood samples were collected at the first and 14th week, and B-ALP and TRAP-5b levels were detected by enzyme- linked immunosorbent assay (ELISA). The rabbits were anesthetized at the 14th week, and pathological cytological observation was performed on both femurs. RESULTS: The age and weights of rabbits in different groups had no statistically significant differences (P>0.05). B-ALP levels in serum of all groups except for the Control Group decreased after treatment, but the differences were not statistically significant (P>0.05). TRAP-5b levels in serum of all groups increased after treatment. Specifically, differences in the GIO Group and calcium carbonate group were statistically significant (P<0.05), while differences in 99Tc-MDP Group and alendronate Group were not statistically significant (P<0.05). Pathological sections revealed that the control group presented normal bone tissue morphology. The bone tissue morphology of the 99Tc- MDP group and alendronate group was similar to control group and GIO group. Moreover, the calcium carbonate group and GIO group exhibited similar bone tissue morphology. CONCLUSION: 99Tc-MDP has a preventive effect on the glucocorticoid-induced osteoporotic rabbit model. This osteoporosis preventive effect might be attributed to the capacities of 99Tc-MDP in promoting the osteoblasts generation and inhibiting the generation and reducing the activity of osteoclasts.

Ultra-compact and broadband silicon polarizer employing a nanohole array structure.

An ultra-compact and broadband transverse magnetic (TM)-pass polarizer is experimentally demonstrated using a photonic crystal nanohole structure. By engineering the period of the circular holes, the fundamental transverse electric mode is suppressed due to the bandgap of the nanohole array, while the T M 0 mode propagates with a negligible insertion loss. Simulation results predict that the bandwidth of the device can reach 245 nm with a 33 dB polarization extinction ratio (PER). In the experiment, an insertion loss <1.2d B for the T M 0 mode and a PER over 20.8 dB are demonstrated in a 70 nm wavelength range from 1520 to 1590 nm, mainly limited by the grating couplers used for fiber-to-chip coupling. The fabricated device is compact with a total length of 7.21 µm.

Improving the regulatory health risk assessment of mercury-contaminated sites.

An alternative risk assessment strategy for mercury (Hg)-contaminated sites is proposed with bioaccessible fractions and soil Hg vapor (SHgV) concentrations. The new strategy avoids the conservatism of assessment rely on soil total Hg (THg) content and inaccuracy caused by predicted SHgV concentration. The exposure risk to Hg-contaminated soil associated with historical mining activities in Guizhou, China, was evaluated using the proposed strategy. The experimental results revealed that the average bioaccessibility in gastric, intestinal and lung phases was 10.39 % (2.09 % ∼ 35.28 %), 1.28 % (0.23 % ∼ 4.3 %), and 11.27 % (5.04 % ∼ 20.71 %), respectively. Via the proposed strategy, the Hg risk for the oral ingestion pathway, represented as the hazard quotient (HQ), decreased from 1.57 to an acceptable level of 0.19 (<1). The risk of SHgV inhalation sharply decreased from 1168 to 0.35 while the soil PM10 inhalation pathway did not exhibit significant variations. The dominant exposure pathways turned to oral intake and inhalation of SHgV by the strategy. The results indicated that the proposed assessment strategy can greatly improve the understanding of the exposure risk level at Hg-contaminated sites and provide a reasonable decision basis for decision makers.

A novel liposome-polymer hybrid nanoparticles delivering a multi-epitope self-replication DNA vaccine and its preliminary immune evaluation in experimental animals.

DNA vaccine is an attractive immune platform for the prevention and treatment of infectious diseases, but existing disadvantages limit its use in preclinical and clinical assays, such as weak immunogenicity and short half-life. Here, we reported a novel liposome-polymer hybrid nanoparticles (pSFV-MEG/LNPs) consisting of a biodegradable core (mPEG-PLGA) and a hydrophilic shell (lecithin/PEG-DSPE-Mal 2000) for delivering a multi-epitope self-replication DNA vaccine (pSFV-MEG). The pSFV-MEG/LNPs with optimal particle size (161.61 ±â€¯15.63 nm) and high encapsulation efficiency (87.60 ±â€¯8.73%) induced a strong humoral (3.22-fold) and cellular immune responses (1.60-fold) compared to PBS. Besides, the humoral and cellular immune responses of pSFV-MEG/LNPs were 1.58- and 1.05-fold than that of pSFV-MEG. All results confirmed that LNPs was a very promising tool to enhance the humoral and cellular immune responses of pSFV-MEG. In addition, the rational design and delivery platform can be used for the development of DNA vaccines for other infectious diseases.

PEGylated-PLGA Nanoparticles Coated with pH-Responsive Tannic Acid-Fe(III) Complexes for Reduced Premature Doxorubicin Release and Enhanced Targeting in Breast Cancer.

Biodegradable poly(lactic-co-glycolic acid) nanoparticles (PLGA NPs) have been widely used as delivery vehicles for chemotherapy drugs. However, premature drug release in PLGA NPs can damage healthy tissue and cause serious adverse effects during systemic administration. Here, we report a tannic acid-Fe(III) (FeIII-TA) complex-modified PLGA nanoparticle platform (DOX-TPLGA NPs) for the tumor-targeted delivery of doxorubicin (DOX). A PEGylated-PLGA inner core and FeIII-TA complex outer shell were simultaneously introduced to reduce premature drug release in blood circulation and increase pH-triggered drug release in tumor tissue. Compared to the unmodified NPs, the initial burst rate of DOX-TPLGA NPs was significantly reduced by nearly 2-fold at pH 7.4. Moreover, the cumulative drug release rate at pH 5.0 was 40% greater than that at pH 7.4 due to the pH-response of the FeIII-TA complex. Cellular studies revealed that the TPLGA NPs had enhanced drug uptake and superior cytotoxicity of breast cancer cells in comparison to free DOX. Additionally, the DOX-TPLGA NPs efficiently accumulated in the tumor site of 4T1-bearing nude mice due to the enhanced permeability and retention (EPR) effect and reached a tumor inhibition rate of 85.53 ± 8.77% (1.31-fold versus DOX-PLGA NPs and 3.12-fold versus free DOX). Consequently, the novel TPLGA NPs represent a promising delivery platform to enhance the safety and efficacy of chemotherapy drugs.

Peculiar attenuation of soil toluene at contaminated coking sites.

In the soil of contaminated coking sites, polycyclic aromatic hydrocarbons (PAHs) and benzene, toluene, ethylbenzene and xylene (BTEX) are typical indicator compounds. Generally, PAHs are enriched in the topsoil layer. BTEX, with higher water solubilities and lower organic carbon-water partitioning coefficients (Koc), are distributed deeper than PAHs. However, current models have employed predictions using single compounds to mimic the migration of BTEX at contaminated coking sites. Such models have not considered the influence of the upper soil layer, where PAHs are enriched. An attempt to fill this gap was made by setting up a control soil column experiment in this study. One column was filled with undisturbed soil (column #1) and the other with PAH-contaminated soil (column #2) to simulate the theoretical and actual surface soil layers, respectively. The results showed that in column #2, the toluene gas concentration of the headspace and time required to reach steady state were notably greater than those in column #1. High-throughput sequencing revealed that there were large microbial community structure differences between the two soil columns throughout the experiment, while some genera that degrade toluene with high efficiency emerged noteworthily in column #2. This implied that the upper soil layer enriched with PAHs was conducive to the degradation of toluene vapor. Applying this finding to human health exposure assessment of toluene suggests that the potential exposure level should be reduced from the current predicted level given the unanticipated attenuation at contaminated coking sites.

Shimian granules improve sleep, mood and performance of shift nurses in association changes in melatonin and cytokine biomarkers: a randomized, double-blind, placebo-controlled pilot study.

Shift nurses are prone to sleep problems and impaired nighttime alertness, with risk for reduced health status plus decreased performance, handling errors, and workplace accidents. Attention to and improvements in the situation of shift nurses are urgent. Shimian granules (SMG), an improved formula of Jieyuanshen with liver qingre and yangxin tranquilizing effects, for more than a decade has been used in China as a herbal treatment of sleep disorders in clinical practice. However, clinical data on SMG have rarely been reported. This double-blinded, randomized, placebo-controlled, pilot clinical trial (ChiCTR-IOR-17013031) aimed to explore whether Shimian granules (SMG) improves sleep and affective state in shift nurses and in association with changes in concentrations of salivary cytokines. Fifty-three rotating-shift female nurses with a Pittsburgh Sleep Quality Index (PSQI) score ≥8 were orally treated with 10.0 g SMG or placebo 2 times daily (30 min after breakfast and 30 min before bed) for 1 month. The Insomnia Severity Index (ISI), a psychomotor vigilance task, Hospital Anxiety and Depression Scale (HADS-A/HADS-D), and levels of four salivary cytokines were evaluated by single time-of-day sampling at baseline and after 1 month of treatment. Significantly lower ISI, HADS, HADS-A, and HADS-D scores, but higher 1/mean reaction time (1/mRT) score, were found in shift nurses treated with SMG than in those who received placebo, and these effects were associated with changes in salivary melatonin, TNF, IL-1ß, and IL-6 levels. These latter findings suggest melatonin, TNF, and IL-6 levels may be suitable biomarkers of ISI score in shift nurses, whereas TNF level may be a suitable biomarker of 1/mRT score and IL-6 level a suitable biomarker of HADS score in response to SMG treatment. The results of this pilot study suggest SMG can effectively improve sleep, alertness, plus anxiety and depression symptoms in shift nurses in association with changes in salivary cytokine levels. The results of this study provide an experimental basis for the evaluation of traditional Chinese medicines for the treatment of insomnia and underlying mechanisms of their actions that require detailed future exploration.

Derivation of site-specific remediation goals by incorporating the bioaccessibility of polycyclic aromatic hydrocarbons with the probabilistic analysis method.

Incorporating bioaccessibility into human health risk assessment is recognized as a valid way to reduce the conservative properties of conventional results, where the total concentration of a contaminant analysed by exhaustive chemical extraction is applied. Taking a coke production site in Beijing as an example, a mild chemical extraction technology was employed to profile the bioaccessibility of benzo[a]pyrene (BaP), indeno[1,2,3-cd]pyrene (IcP) and dibenz[ah]anthracene (DBA) in soils. The results that were regressed using two bi-phase desorption models (Karickhoff and Weibull) revealed that the rapid desorption fractions of BaP, IcP and DBA, which are taken for bioaccessible fractions, were basically less than half of the total contents in the soils. Probabilistic analysis (PA) was carried out with pre-set distributions of the exposure parameters to characterize the uncertainty in the assessment. The results incorporating bioaccessibility and PA were several times higher than the generic remediation goals which equal to national screening levels, and orders of magnitude higher than the baselines of the region and nation. The results of the Weibull fit were finally recommended as site-specific remediation goals (SSRGs) (10.59 mg/kg, 95.48 mg/kg and 9.24 mg/kg). Over-remediation was avoided while contributing to considerable economic and environmental benefits.

A source depletion model for vapor intrusion involving the influence of building characteristics.

If volatile organic compound (VOC)-contaminated soil exists underneath a building, vapors may migrate upwards and intrude into the interior air of the building. Most previous models used to simulate vapor intrusion (VI) were developed by assuming that the source was constant, although a few recent models, such as the Risk-Based Corrective Action (RBCA) Tool Kit (TK) model, have been developed to consider source depletion (SD). However, the RBCA TK model ignores the effects of building characteristics due to its assumption that the ground is not covered by the actual building it models, which leads to incorrect results since the presence of the building affects the SD. In this study, a SD model is developed based on the three processes of VI while considering the impact of key building parameters on SD. The proposed model (i.e., the SD model) still follows the law of mass conservation, and the sensitivity analysis shows that the soil-building pressure differential (dP) is an important building characteristic that affects SD. Taking trichloroethylene (TCE) for simulation in the case of a soil concentration below the saturation concentration, as the soil permeability decreases, the differences in the results between the SD model and RBCA TK model decrease; as the Peclet number decreases, the effect of the dP on the results of the SD model decreases. The new model only accounts for the migration of contaminants at the source of depletion; therefore, the model is more applicable for these contaminants, which are considered to have low-biodegradable characteristics. Furthermore, since the model emphasizes the impact of buildings on the source, it is applicable when there is a considerable building area above the source, such as large commercial buildings or residential communities with underground parking lots, which exist in most cities.

Applicability of Soil Concentration for VOC-Contaminated Site Assessments Explored Using Field Data from the Beijing-Tianjin-Hebei Urban Agglomeration.

A total of 128 available soil-soil gas data pairs of benzene were collected from 5 contaminated sites in the Beijing-Tianjin-Hebei urban agglomeration. Soil gas concentrations predicted by the linear model and the dual equilibrium desorption (DED) model were compared with measured values. Although the immersion of soil samples in methanol during sampling and preservation was specified to minimize volatilization losses and biodegradation, the study still found that many points with high soil gas concentrations correspond to unreasonably low soil concentrations. Further analysis revealed that the soil matrices of these points are basically composed of sandy and silty soils, given that soil gas collected may migrate from more contaminated soils nearby due to the large porosity and soil benzene escapes more easily during sampling in the coarser soil particles. Therefore, for sandy and silty soil, collecting soil gas would be more reasonable for screening the vapor intrusion (VI) pathway. For clay, the combination of bulk soil concentration and the DED model will be more convenient. Defaulting f as 1, as recommended by previous studies in the DED, would not be suitable for all cases, and this value needs to be further explored to revise the DED model for future applications.