Effects of Slip Length and Inertia on the Permeability of Fracture with Slippery Boundary Condition.

Although the slippery boundary condition (BC) has been validated to enhance fracture permeability (k), the coupling effects of heterogeneous slippery BC and inertia on k remain less understood. We used computational fluid dynamics to investigate the competing roles of slippery BC and inertial forces in controlling k evolution with increasing pressure gradient by designing six cases with different slip length scenarios for a two-dimensional natural fracture. Our results suggest that pronounced inertial effects were directly related to and demonstrated by the growth of recirculation zone (RZ); this caused flow regimes transitioning from Darcy to non-Darcy and significantly reduced k, with an identical tailing slope for six cases, regardless of the variability in slip lengths. Moreover, the slippery BC dominantly determine the magnitude of k with orders depending on the slip length. Lastly, our study reveals that the specific k evolution path for the case with a varying slip length was significantly different from other cases with a homogeneous one, thus encouraging more efforts in determining the slip length for natural fractures via experiments.

Biodegradation of carbon tetrachloride from groundwater in an upflow solid-phase biofilm system.

In the present study, an upflow solid-phase denitrification biofilm reactor (US-DBR) was applied for simultaneous carbon tetrachloride (CT) and nitrate removal from groundwater by using poly(butylene succinate) (PBS) as carbon source and biocarrier. After 80 days continuous operation, the nitrate and CT removal efficiencies in the biofilm reactor were high of 98% and 94.3%, respectively. After PBS-biofilm formation, protein (PN) content in loosely bound extracellular polymeric substances (LB-EPS) and tightly bound EPS (TB-EPS) significantly increased 2.6 and 4.0 times higher in the presence of CT than those of absence of CT, while PS increased 1.9 and 2.0 times higher. According to excitation-emission matrix (EEM), CT exposure contributed to the increased fluorescent intensities of the aromatic PN-like and tryptophan PN-like substances. Along with the height of US-DBR, the denitrification activity was inhibited by the CT exposure, and most of CT was significant transformed accompanied by nitrate removal. Two components of soluble microbial products (SMP) were identified, including humic-like substances for component 1 and PN-like substances for component 2, respectively. It was found from high-throughput 16S rRNA gene sequencing analysis that significant differences were observed at genus level by taxonomic assignments to CT exposure. Thiobacillus, Thauera, Candidatus_Competibacter and Hydrogenophaga were the main genus in the presence of CT at the proportion of 6.77%, 5.47%, 3.59% and 3.17%, respectively.

Detection of semi-volatile organic compounds (SVOCs) in surface water, soil, and groundwater in a chemical industrial park in Eastern China.

China is suffering from serious water and soil pollution, especially in the North China Plain. This work investigated semi-volatile organic compounds (SVOCs) in surface water, groundwater and soil within a chemical industrial park in Eastern China, for which the volatile organic compound (VOC) results have been previously reported. A total of 20 samples were collected from the field, and analyzed in the laboratory. A 100% detection frequency of SVOCs in samples from this chemical industrial park was observed (same as VOCs). Moreover, the detection frequency of 113 SVOCs in each sample reached 15.93, 12.39 and 20.35% for surface water, groundwater and soil, respectively. The most detected SVOCs in the park included N-containing SVOCs, polycyclic aromatic hydrocarbons, phthalates, organic pesticides and polychlorodiphenyls. The elevated detecting frequencies and concentration levels of SVOCs identified in the groundwater were attributed to the intensive chemical production activities in the park. In addition, the agricultural activities in the area might also have contributed to the SVOCs to the groundwater. The results of VOCs and SVOCs from this and previous studies suggest that the groundwater in this industrial park has been severely contaminated, and the contamination likely spreads beyond the park. Imminent hydrogeological assessments and remedial actions are warranted to eliminate the source and mitigate the potential plume expansion beyond the park boundary.

Distribution of volatile organic compounds (VOCs) in surface water, soil, and groundwater within a chemical industry park in Eastern China.

This paper focuses on the distribution of volatile organic compounds (VOCs) in the surface water, soil, and groundwater within a chemical industry park in Eastern China. At least one VOC was detected in each of the 20 sampling sites, and the maximum number of VOCs detected in the surface water, groundwater, and soil were 13, 16, and 14, respectively. Two of the 10 VOCs with elevated concentrations detected in surface water, groundwater, and soil were chloroform and 1,2-dichloroethane. The characteristics of VOCs, which include volatility, boiling point, and solubility, could significantly affect their distribution in surface water, soil, and groundwater. However, due to the direct discharging of chemical industry wastewater into surface water, higher concentrations of VOCs (except chloroform) were detected in surface water than in soil and groundwater. Fortunately, the higher volatility of VOCs prevents the VOCs from impacting groundwater, which helps to maintain a lower concentration of VOCs in the groundwater than in both surface water and soil. This is because pollutants with relatively higher boiling points and lower solubilities have higher detection frequencies in soil, and contaminants with relatively lower boiling points and higher solubilities have higher detection frequencies in water, notably in surface water.