A novel bioaccessibility prediction method for complex petroleum hydrocarbon mixtures in soil.

More evidence shows that bioaccessibility instead of total concentrations based on exhaustive extraction methods can better reflect the actual risk level of petroleum hydrocarbon contaminated sites, so it is essential to establish an effective assessment method for bioaccessibility. This study utilized Tenax extraction, butanol extraction, hydroxypropyl-ß-cyclodextrin (HPCD) extraction, and a composite extraction method involving HPCD with LMWOAs (citric acid, CA) and surfactants (rhamnolipid, RL; Tween80, TW80; sodium dodecyl sulfate, SDS) at varying concentrations. These methods were employed to predict the bioaccessibility of earthworms to soil at different aging time of petroleum hydrocarbons. The results showed that traditional extraction methods such as Tenax 6h extraction and n-butanol extraction were ineffective in evaluating petroleum hydrocarbons' bioaccessibility. In contrast, the composite extraction of HPCD and solubilizer enhanced the extraction efficiency of HPCD greatly, and the extraction results showed a significant positive correlation with earthworm accumulation. By the comparison of the extraction results of different fractions of petroleum hydrocarbons, heavy fractions of petroleum hydrocarbons (C29-C40) are essential factors affecting chemical extraction effects. The correlation coefficients of four composite extraction methods and total petroleum hydrocarbons (TPH) of earthworm accumulation by linear regression analysis ranged from 1.1797 to 1.7990, and the slopes ranged from 0.8727 to 0.9792. Among them, the combined extraction method of 50 mmol/L HPCD and 0.5 mmol/L rhamnolipid had the best effect (r2 = 0.9792, slope = 1.1797), which could be used as an evaluation method suitable for the bioaccessibility of petroleum hydrocarbons in soil. This study could provide a new method for evaluating the bioaccessibility of organic pollutants and technically supporting risk assessment and bioremediation of complex petroleum hydrocarbons in soil.

Bioremediation experiments and dynamic model of petroleum hydrocarbon contaminated soil.

Clarifying the occurrence and morphological characteristics of petroleum hydrocarbons (PHs) in soil can facilitate a comprehensive understanding of their migration and transformation patterns in soil/sediment. Additionally, by establishing the dynamic transformation process of each occurrence state, the ecological impact and environmental risk associated with PHs in soil/sediment can be assessed more precisely. The adsorption experiments and closed static incubation experiments was carried out to explore the PHs degradation and fraction distribution in aged contaminated soil under two remediation scenarios of natural attenuation (NA) and bioaugmentation (BA) by exogenous bacteria through a new sequential extraction method based on Tenax-TA, Hydroxypropyl-ß-cyclodextrin and Rhamnolipid (HPCD/RL), accelerated solvent extractor (ASE) unit and alkaline hydrolysis extraction. The adsorption experiment results illustrated that bioaugmentation could promote the desorption of PHs in the adsorption phase, and the soil-water partition coefficient Kd decreased from 0.153 L/g to 0.092 L/g. The incubation experiment results showed that compared with natural attenuation, bioaugmentation could improve the utilization of PHs in aged soil and promote the generation of non-extractable hydrocarbons. On the 90th day of the experiment, the concentrations of weakly adsorbed hydrocarbons in the natural attenuation and bioaugmentation experimental groups decreased by 46.44% and 87.07%, respectively, while the concentrations of strongly adsorbed hydrocarbons and non-extractable hydrocarbons increased by 77.93%, 182.14%, and 80.91%, and 501.19%, respectively, compared their initial values. We developed a novel dynamic model and inverted the kinetic parameters of the model by the parameter scanning function and the Markov Chain Monte Carlo (MCMC) method based on the Bayesian approach in COMSOL Multiphysics® finite element software combined with experimental data. There was a good linear relationship between experimental interpolation data and model prediction data. The R2 for the concentrations of weakly adsorbed hydrocarbons ranged from 0.9953 to 0.9974, for strongly adsorbed hydrocarbons from 0.9063 to 0.9756, and for non-extractable hydrocarbons from 0.9931 to 0.9982. These extremely high correlation coefficients demonstrate the high accuracy of the parameters calculated using the Bayesian inversion method.

An evaluation model for in-situ bioremediation technology of petroleum hydrocarbon contaminated soil.

Considering the interference of the complexity of underground environment to the bioremediation scheme, an evaluation model for bioremediation technology in the soil source area of oil contaminated sites was established. On the basis of traditional CDE model, a compartment model was coupled to express the adsorption and degradation process, and the spatial expression of biodegradation was enriched through environment-dependent factors. The visualization of the model was achieved based on COMSOL Multiphysics software platform. Two sets of indoor sandbox experiments on natural attenuation and bioaugmentation were carried out for 120 days to verify the prediction function of the model. The results showed that bioaugmentation greatly improved the remediation effect. Petroleum hydrocarbons with different occurrence states exhibited different spatial distributions under the influence of environmental factors. The prediction accuracy evaluation results of total petroleum hydrocarbons, bio available hydrocarbons and non extractable hydrocarbons showed excellent fitting degree, and the model had a good prediction function for petroleum hydrocarbon in soil under different bioremediation scenarios. This model can be used to screen bioremediation technical schemes, prevent pollution and assess risk of petroleum hydrocarbon contaminated sites.

Soil properties and functional genes in nitrogen removal process of bioretention.

The effects of different soil properties on hydrology and nitrogen removal were studied in a simulated bioretention system. Soil capacity of permeability and water retention, changes in the soil environment, leachate concentrations at the surface and bottom layers, quantification of N removal from soil, microorganism and plant by 15N isotope tracer technique, and functional genes abundance at different depths were evaluated. The results showed that shallow root plants, soil compaction, and low organic matter content were not conducive to the infiltration of bioretention systems. In the 72 h experiment, compaction (especially surface compaction) and planting of herbaceous plants (Ophiopogon japonicus) were not beneficial to the removal of TN, TP, and COD. Adding an appropriate amount of organic matter also affects nitrogen and phosphorus removal. In the process of denitrification, the order of the ability to remove nitrogen is soil adsorption > microbial assimilation > plant uptake. The contribution of soil denitrification is affected by soil compaction, compaction location, plant species and organic matter content. The abundance of 16S rRNA, nitrifying, denitrifying and nrfA genes decreased with soil depth. More copies of genes in topsoil were thought to be due to sufficient nutrients, aerobic condition, anaerobic microsites and submerged state. Soil compaction, organic matter content and plant species affected nitrification, denitrification and DNRA gene characteristics.

The payment scheme for ecosystem services in the coastal city based on the ecosystem services value and current payment efficiency: a case study in Jimo of Qingdao city, China.

The reasonable strategies of payment for ecosystem services (PES) play a key role in solving the contradiction between ecological protection and economic development in coastal cities. However, at present, the payment efficiency is relatively low and the determination method of PES is lack. Therefore, in this study, the Jimo district of Qingdao city in China, a typical coastal city, was selected as study area, and the equivalent factor method and marine ecological capital assessment method were used to obtain terrestrial and marine ecosystem services value (ESV) and its tempo-spatial variations from 2010 to 2018. Moreover, the payment efficiency of the sea area and 15 towns over 8 years was measured using the Super-efficient SBM-DEA model based on undesired output. ESV presented a clear reduction over 8 years. The marine ecosystem provided the main service value, and waste treatment, water regulation, and soil formation were the top 3 main functions in the land ecosystem. Regulating services provided the highest component among all functions. The high-value areas were mainly distributed in the northeast and northwest regions and the low-value areas were in the south-central regions. The average payment efficiency of the sea area and 15 towns over 8 years shown a stable trend at a low level. On the basis of the evaluation of ESV and efficiency, a new possible payment scheme including payment order and quota was proposed. The total quota of marine ecosystem was 5.226 billion RMB (88% of the total) and of terrestrial ecosystem was 0.713 billion RMB. Tian Heng, Jin Kou, Yi Fengdian, and Ling Shan are the first 4 priority towns, with compensation amounts of 0.205, 0.083, and 0.063 billion RMB respectively, while the last 3 towns are Tong Ji, Huan Xiu, and Chao Hai accounting for 6.02% of the total. The theoretical payment total quota was 5.939 billion RMB, and which accounted for a low proportion of local GDP. The study can provide some recommendations for making the reasonable and feasible payment schemes for ecosystem services in coastal city, and it is feasible in the practice of ecological environment protection and sustainable development.

[Human immunodeficiency virus/sexually transmitted infection, risk behavior and sexual networks among men who have sex with men in Taizhou city, Zhejiang province].

OBJECTIVE: To study the prevalence of human immunodeficiency virus (HIV), sexually transmitted infection (STI), risk behavior and the sexual networks among men who have sex with men (MSM) in Taizhou city, Zhejiang province. METHODS: A cross-sectional study was applied with venue-based sampling in 2 MSM gathering sites in Taizhou. 'Informed Consent' principle was applied and MSM were studied through a structured questionnaire. Blood samples were collected from those who accepted free and confidential HIV/STI counseling and then tested for HIV, syphilis, HCV and HSV-2 antibodies with ELISA. HIV positive sera were certified with western blot. RESULTS: 106 MSM were investigated and 97 qualified questionnaires were collected. 25.0% (23/92) of these MSM have ever had 1 female sex partner while 47.8% (44/92) had 2 or more. 14.3% (13/91) of them reported having had 1 male partner who had engaged in anal sex and 80.2% (73/91) had 2 or more. 22.1% (19/86) of them had participated in group sex but 62.5% (55/88) of them did not always use condom when having anal intercourse. 15.1% (14/93) of them had 1 oral sex partner while 75.3% (70/93) having 2 or more. 38.9% (37/95) of them had sex with female sex worker, and 35.5% (33/93) had sex with male-to-male sex worker. 15.3% (13/85) of them had once been male-to-male sex worker themselves. 3.9% (3/77) of them were found HIV positive in blood tests, with 24.7% (18/73) positive of syphilis, 15.1% (11/73) positive of HSV-2 but HCV appeared to be negative. 46 cases reported their egocentric recognition networks, with mean degree of 5.91 (ranging 0 - 10), and mean density of 0.548 (ranging 0.000 - 1.000). 43 sexual networks were identified, with mean degree of 2.70 (ranging 0 - 10), and mean density of 0.246 (ranging 0.000 - 1.000). CONCLUSION: Risk behaviors, such as multiple sex partners, low proportion of condom use and commercial sex engagement, both with heterosexuals and homosexuals, were extensively existed among MSM in Taizhou, and the prevalence of HIV/STI was relatively high. Their sexual networks seemed complicated but there might be in place of some substantially isolated MSM groups with high risk of HIV/STI infection. More study should be applied to identify the relationship between sexual networks and HIV/STI transmission.