Remediating petroleum hydrocarbons in highly saline-alkali soils using three native plant species.

Phytoremediation of total petroleum hydrocarbons (TPHs) contamination is a process that uses the synergistic action of plants and rhizosphere microorganisms to degrade, absorb and stabilize pollutants in the soil, and has received increasing attention in recent years. However, this technology still has some challenges under certain conditions (e.g., highly alkaline and saline environments). The present study was selected three native plant species (alfalfa, tall fescue, and ryegrass) to remediate petroleum pollutants in greenhouse pot experiments. The results indicate that TPH contamination not only inhibited plant growth, soil chemical properties and soil fertility (i.e. lower plant biomass, chlorophyll, pH, and electrical conductivity), but also increased the malondialdehyde, glutathione, and antioxidant enzyme activities (catalase and polyphenol oxidase). Further, correlation analysis results illustrated that TPH removal was strongly positively correlated with chlorophyll, soil fertility, and total organic carbon, but was negatively correlated with dehydrogenase, polyphenol oxidase, pH, and electrical conductivity. The highest TPHs removal rate (74.13%) was exhibited by alfalfa, followed by tall fescue (61.79%) and ryegrass (57.28%). The degradation rates of short-chain alkanes and low rings polycyclic aromatic hydrocarbons (PAHs) were substantially higher than those of long-chain alkanes and high rings PAHs. The findings of this study provide valuable insights into petroleum decontamination strategies in the highly saline - alkali environments.

Status, distribution, source, and risk of polychlorinated biphenyl levels in soils of five cities from the Hexi Corridor, Northwest China.

Few studies have been performed on the persistent organic pollutant contamination in soil from the plateau and remote areas, particularly the mid-latitude arid and semi-arid regions of Northwest China. The occurrence, spatial distribution, source, and potential risk of 12 polychlorinated biphenyls (PCBs) were investigated in soil collected from five Hexi Corridor cities in Northwest China. All of the PCBs were detected individually in the soil samples. The concentration of Σ12PCBs in the Hexi Corridor ranged from 2.0 to 148.5 ng/g, with an average of 21.3 ng/g. The tetra-CBs and hexa-CBs were the dominant PCB components in the soil. Higher PCB levels were found in the industrial city of Jiuquan, and the fewest PCBs were detected at Jinchang. Source analysis by principal component analysis showed that the dominant sources of PCBs were automobile exhaust, paint additives, insulation materials, and other industrial products. The carcinogenic health risk of PCBs in the Hexi Corridor soil was within acceptable levels, but the exposure risk of PCBs in soil for children was higher than that for adults.

Source apportionment and health risk assessment of potentially toxic elements in soil from mining areas in northwestern China.

Soil contaminated with toxic elements from mining activities is a public health concern. In order to obtain a comprehensive understanding of the status and potential risks of inorganic toxic elements in soil resulting from mining activities, Cu, Pb, Cr, Zn, Ni, As, and Cd were selected to evaluate a total of 42 soil samples collected from Gannan mining areas in northwestern China. The concentrations of As and Cd were much higher than their respective background values, while the concentrations of the other elements fluctuated around their background values. Results of combined multivariate statistical analyses and the distribution patterns of the individual pollutants imply that the toxic elements were originated from different sources even for one element in different sampling locations. The pollution index values indicated that As and Cd have a moderate to high pollution levels. The geo-accumulation indexes (Igeo) indicated that Cu, Pb, Cr, Zn, and Ni are likely of geologic origin, while As and Cd have been significantly affected by anthropogenic activities. Potential ecological risk indexes further showed that soils from mining areas within the study area pose a high potential ecological risk, and As and Cd were major risk contributors. Based on the calculated Hazard Index, the ingestion of soil particles appeared to be the main exposure route resulting in a higher risk, followed by dermal contact. The potential health risks of children and adults for As were greater than the safe level. The carcinogenic risk associated with As for local residents was also higher than the accepted levels, indicating a serious health risk to local residents. These results suggest that proper management strategies and various remediation practices should be implemented in the Gannan mining area in northwestern China.

Status, Sources and Potential Risk of Polycyclic Aromatic Hydrocarbons in Soils from Hexi Corridor in Northwest China.

The Hexi Corridor is the main commodity grain base in northwest China and plays a special role in ensuring food security in northwest China. However, the multiple pollution transport pathways of PAHs and complex and co-existing potential pollution sources around the study areas require a combination of pollution status, source identification, and risk assessment to explore pollution distribution and potential risks. In this study, the total PAHs concentration (∑18PAHs) in soils ranged from 69.6 to 1300 ng/g. Spatially, the higher content of PAHs was detected in the Jinchang, followed by Jiayuguan, Jiuquan, Wuwei, and Zhangye, indicating a remarkable influence of different industrial activities. Although high-molecular-weight PAHs were predominated, the compositions of PAHs in most of the soil samples were varied. The isomer ratios of PAHs and principal component analysis were also revealed the PAHs probably originate from the sources different significantly. The total health risk values indicated a low health risk.

Distribution, Composition, Sources, and Potential Ecological Risks of PAHs in the Sediments of the Lanzhou Reach of the Yellow River, China.

The distribution, composition, sources, and potential ecological risks of polycyclic aromatic hydrocarbons (PAHs) in the sediments of the Lanzhou Reach of the Yellow River, China were investigated. The total concentration of the 18 individual PAHs (∑18PAHs) in the sediments ranged from 638 to 1620 ng/g, with a mean value of 901 ng/g. The pollution level of PAHs in the sediments was low to moderate. Spatially, the distribution of PAHs in the sediments showed an increasing trend along the direction of water flow. ∑18PAHs predominantly consisted of low molecular weight PAHs. The principal component analysis and isomer ratios of PAHs suggested the mixed sources of petroleum and those from the combustion of petroleum, coal, and biomass. The results showed that the PAHs in the sediments of the Lanzhou Reach of the Yellow River have a low ecological risk. However, the BaP equivalent exposure values suggested a potential cancer risk.

Influence mechanism of organic matter and low-molecular-weight organic acids on the interaction between minerals and PAHs.

Investigate the effect of soil organic matter (SOM) and low molecular weight organic acids (LMWOAs) on minerals adsorption of PAHs. Batch adsorption experiments have been carried out to study the adsorption of PAHs (Naphthalene (NaP), Phenanthrene (Phe) and Pyrene (Pyr)) by minerals (Montmorillonite (Mnt), kaolinite (Kln) and calcite (Cal)). This research found that compared with Kln and Cal, Mnt showed the maximum adsorption capability for PAHs. And the order of PAHs adsorption by Mnt was: Pyr > Phe > Nap, which corresponds to the octanol-water partition coefficient (Kow) of different PAHs. The adsorption kinetic and isotherm were well fitted by Pseudo-second-order kinetic model, Freundlich and Linear isotherm model. Furthermore, inorganic ions (Ca2+) impacted PAHs adsorption by competitive adsorption and cation-π interactive. Cal has the maximum desorption of PAHs among three minerals, and there was desorption hysteresis phenomenon. Field emission-scanning electron microscope (Fe-SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) analysis indicated that SOM enhanced the sorption of PAHs by van der Waals, hydrogen bonding, π-π interactions, and chemical bonding. LMWOAs significantly inhibited PAHs adsorption and promote PAHs desorption from the minerals. As a result, LMWOAs increased of PAHs bioavailability, which provide a new strategy to improve PAHs cleanup efficiency.

Spatial distribution, composition, and source analysis of petroleum pollutants in soil from the Changqing Oilfield, Northwest China.

Petroleum contamination surrounding oilfields has attracted more concerns. However, the levels, distribution and source of petroleum of Changqing Oilfield soil still remain lots of knowns, which is important for local environmental protection. Given soil contamination issues in Changqiong Oilfield were investigated. The maximum concentrations of total petroleum hydrocarbons (TPHs), N-alkanes (TNAs) and polycyclic aromatic hydrocarbons (PAHs) were determined to be 1960.29, 96.13 and 0.82 mg/kg, respectively. TPHs were higher in the north than the south of the study area. TPHs decreased in the horizontal and vertical distribution as soil depth and distance from oil wells increased. Source analysis showed that TNAs mainly originated from petroleum, PAHs were controlled by petroleum spills, combustion and traffic. Correlation analysis implied that TPHs residues had an effect on soil environmental quality. This study have important implications for understanding the environmental behavior of petroleum and can provide support for petroleum remediation and risk control.

New insights into the sorption of U(VI) on kaolinite and illite in the presence of Aspergillus niger.

The regulation effect of Aspergillus niger to the sorption behavior of U(VI) on kaolinite and illite was studied through investigating the enrichment of U(VI) on kaolinite-Aspergillus niger and illite-Aspergillus niger composites. Kaolinite- or illite-A. niger composites were prepared through co-culturation method. Results showed that U(VI) sorption on kaolinite and illite in different pH ranges could be attributed to ion exchange, outer-sphere complexes (OSCs), and inner-sphere complexes (ISCs), while only the ISCs on the bio-composites. Moreover, micro-spectroscopy tests revealed that U(VI) coordinate with phosphate, amide, and carboxyl groups on illite- and kaolinite- A. niger composites. X-ray photoelectron spectroscopy (XPS) further found that U(VI) was partly reduced to non-crystalline U(IV) by A. niger in the bio-composites, occurring as phosphate coordination polymers or biomass-associated monomers. The findings herein provide further insight into the immobilization and migration of uranium in environments.

Polybrominated diphenyl ethers in the environment and human external and internal exposure in China: A review.

Polybrominated diphenyl ethers (PBDEs) are widely used as brominated flame retardants. Because of their toxicity and persistence, some PBDEs were restricted under the Stockholm Convention in 2009. Since then, many studies have been carried out on PBDEs in China and in many other countries. In the present review, the occurrences and contamination of PBDEs in air, water, sediment, soil, biota and daily food, human blood, hair, and other human tissues in China are comprehensively reviewed and described. The human exposure pathways and associated health risks of PBDEs are summarized. The data showed no obvious differences between North and South China, but concentrations from West China were generally lower than in East China, which can be mainly attributed to the production and widespread use of PBDEs in eastern regions. High levels of PBDEs were generally observed in the PBDE production facilities (e.g., Jiangsu Province and Shandong Province, East China) and e-waste recycling sites (Taizhou City, Zhejiang Province, East China, and Guiyu City and Qingyuan City, both located in Guangdong Province, South China) and large cities, whereas low levels were detected in rural and less-developed areas, especially in remote regions such as the Tibetan Plateau. Deca-BDE is generally the major congener. Existing problems for PBDE investigations in China are revealed, and further studies are also discussed and anticipated. In particular, non-invasive matrices such as hair should be more thoroughly studied; more accurate estimations of human exposure and health risks should be performed, such as adding bioaccessibility or bioavailability to human exposure assessments; and the degradation products and metabolites of PBDEs in human bodies should receive more attention. More investigations should be carried out to evaluate the quantitative relationships between internal and external exposure so as to provide a scientific basis for ensuring human health.