Human carcinogenic risk analysis and utilization of shale gas water-based drilling cuttings in road materials.

Water-based drilling cuttings (WDC) generated during shale gas development will endanger human health and ecological security. The modern analytical techniques are used to analyze the organic pollutants in WDC, and the human health and ecological security risks of harmful pollutants in WDC under specific scenarios are evaluated. The results showed that the content of organic pollutants in WDC was evaluated by human health and safety risk assessment. The comprehensive carcinogenic risks of all exposure pathways of single pollutant benzo(a)anthracene, benzo(a)pyrene, benzo(k)fluoranthene, and indeno(1,2,3-cd)pyrene were acceptable. However, the cumulative carcinogenic risk of exposure to dibenzo(a,h)anthracene particles via skin exposure was not acceptable. It was considered that only dibenzo(a,h)anthracene had carcinogenic effect, and the risk control limit of dibenzo(a,h)anthracene in WDC was 1.8700 mg/kg by calculation. As well as, the "WDC-cement" gel composite structure was deeply analyzed, and the physical and chemical properties and mechanism of organic pollutants in cement solidified WDC were analyzed, which provided theoretical support for the study of WDC pavement cushion formula. Based on the above conclusions and combined with the actual site, by studying and adjusting the formula of WDC pavement cushion, the WDC pavement cushion was finally designed by 6% cement + 50% WDC + 44% crushed stone. The 7d unconfined compressive strength met the requirements of the Chinese standard "Technical Guidelines for Construction of Highway Roadbases" (JTG/T F20-2015). Also, the process route of WDC as road cushion product was sampled and analyzed. In addition, the leaching concentration of main pollutants all met the relevant standards of China. Therefore, this study can provide a favorable way for the efficient, safe, and environmentally friendly utilization of WDC, and ensure the ecological environment safety and human health safety of WDC in resource utilization.

Characteristic pollutants risk assessment of modified manganese residue utilization in sintered product.

The resource disposal of electrolytic manganese residue can effectively solve the problem of environmental pollution caused by it, among which the problem of heavy metal pollution is the most prominent. In this study, a new type of eco-friendly brick mixed with electrolytic manganese residue was designed. The influence of the content of electrolytic manganese residue on its macroscopic properties, microscopic properties, and leaching characteristics was analyzed by test methods such as compressive strength test, radioactivity test, XRF, XRD, FTIR, and ICP test of bricks. The results showed that the manganese content in the EMR leachate was 8120 mg/L, which exceeded the Chinese standard. The leaching experiment of ordinary aqueous solution of sintered bricks mixed with 20% EMR showed that the content of heavy metals was far lower than the Chinese national standard. There was no non-carcinogenic risk of heavy metals in the strong acid leaching solution of sintered bricks mixed with 20% EMR. Only the carcinogenic risk values of Cr for adults and children were 4.21 × 10-4 and 9.82 × 10-4 respectively, both exceeding the USEPA limit, but the application scene of sintered bricks was difficult to achieve strong acidity, so it was judged that it had no carcinogenic risk to the human body. Characteristic heavy metals such as Mn, Cr, and As existed stably in sintered bricks through substitution and encapsulation. In addition, the compressive strength and radioactivity of EMR sintered bricks met the requirements of the Chinese national standard "Fired Ordinary Bricks." This product can be used as national standard MU20 grade brick. This study provided an efficient method for the safe and environmentally friendly disposal of EMR in a sustainable control system.

Property of concrete made of recycled shale gas drilling cuttings.

Exploration and development of shale gas generate a lot of water-based drilling cuttings (WDC), which can then be used in concrete engineering. This work studied mix ratio optimization, mechanical properties, leaching characteristics and the microstructure of the WDC concrete. The results showed that the pH and COD values of these WDC were slightly above 9.0 and 60, respectively. All other indices satisfied the first grade standard of Chinese standard GB8978. On the other hand, a moderate amount of WDC can be improved concrete properties, especially its workability and compressive strength. When the water-binder ratio is 0.52 and the sand ratio is 41%, we can obtain C25 strength grade and 130 ~ 140 mm slump grade concrete by adding high efficiency water reducing agent and fly ash. XRD and SEM analysis showed that the silica and aluminum oxide in WDC reacted with calcium hydroxide to form secondary hydration products: C-S-H gel and ettringite, which are conducive to the formation of concrete strength and solidified the heavy metals and other contaminants. EDX analysis found it is known that the hydration products in WDC concrete can bind metal elements well. The environmental leaching test shows that the recycled WDC added to concrete products as aggregate and admixture is very environmentally friendly and sustainable.

Marinobacter aromaticivorans sp. nov., a polycyclic aromatic hydrocarbon-degrading bacterium isolated from sea sediment.

A rod-shaped, Gram-stain-negative, slightly halotolerant bacterium, designated strain D15-8PT, was isolated from a sediment sample from the South China Sea. The strain could grow in NaCl concentrations ranging from 0.5 % to 10 % (w/v) (optimum 0.5-1.5 %), and could be cultivated at 10-40 °C (optimum 25 °C) and pH 5.5-9.5 (optimum pH 7.0-8.0). The strain was positive for catalase, oxidase, and hydrolysis of Tween 80, but negative for hydrolysis of DNA and gelatin, nitrite reduction, indole production, Voges-Proskauer reaction, and methyl red test. Strain D15-8PT could biodegrade naphthalene, phenanthrene, and anthracene. The major respiratory quinone was Q-9. The main cellular fatty acids were C12 : 0 (11.5 %), C14 : 0 3-methyl (22.0 %), C16 : 0 (19.2 %), C16 : 1ω9c (22.9 %), and C18 : 1ω9c (6.7 %). The polar lipids were phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, an unidentified aminophospholipid and an unidentified phospholipid. The DNA G+C content was 56.8 mol%. Phylogenetic analyses based on 16S rRNA genes showed that strain D15-8PT was most closely related to Marinobacter maritimus JCM 12521T (98.5 % 16S rRNA gene sequence similarity), Marinobacter antarcticus CGMCC 1.10835T (98.1 %), Marinobacter lipolyticus DSM 15157T (97.1 %), and Marinobacter guineae CECT 7243T (97.0 %). Results of the gyrB gene analysis and DNA-DNA hybridization were both less than the cut-off values (90 % for gyrB gene sequence similarity and 70 % for DNA-DNA hybridization). On the basis of this taxonomic study using a polyphasic approach, strain D15-8PT represents a novel species of the genus Marinobacter, for which the name Marinobacter aromaticivorans sp. nov. is proposed. The type strain is D15-8PT ( = CGMCC 1.11015T = KCTC 23781T).

Bioassessment of marine sediment quality using meiofaunal assemblages in a semi-enclosed bay.

In order to assess marine sediment quality of a semi-enclosed bay, sediment and meiofaunal samples were analyzed at 35 stations in coastal waters of Bohai Bay, China. Concentrations of heavy metals (Cd, Cr, Cu, Ni, Pb, Zn, Co and Mn) in sediment were measured and the Hakanson potential ecological risk index coupled with the ratio of nematodes to copepods (N/C ratio) was used. Results showed that the concentration of Mn was the highest while Cd was the main risk contributor. The Hakanson potential ecological risk index indicated that all pollutants posed low risks in the study area. However, the N/C ratio exhibited different results compared with Hakanson potential ecological risk index. BIOENV analysis identified the concentration of Ni and sediment grain size as the most important environmental variables influencing meiofaunal assemblages. The present study indicated that, in marine sediment quality assessments, meiofaunal assemblages should be involved besides pollutant concentrations.

[Assemblage composition and distribution of meiofauna in the southern Yellow Sea cold water mass during summer and autumn].

In order to study the impact of the Yellow Sea cold water mass (YSCWM) on meiofauna, the composition, abundance, biomass of meiofauna and their relationships with environmental variables were analyzed through the samples from 8 stations investigated by R/V 'Dongfanghong II' in June and November, 2013. The results showed that the average abundances of meiofauna were 900.8 and 758.4 ind · 10 cm(-2), and biomasses were 886.9 and 615.7 µg · 10 cm(-2) in June and November, 2013, respectively. Results of ANOVA showed that no significant differences of meiofaunal abundance and biomass were detected among the 8 stations in the two study cruises. A total of 17 meiofaunal groups were identified. The most dominant taxonomic group was free-living marine nematodes, with relative dominance of 88.5% in June and 94.0% in November. The following groups were also important, including benthic copepods, polychaetes, kinorhynchs and ostracods. Analysis of meiofaunal vertical distribution indicated that 92.5% and 95.4% of meiofauna distributed in the top 5 cm of the sediment in the two study cruises, while 59.1% of nematodes and 78.2% of copepods were found in the top 2 cm of the sediment. Correlation analysis among meiofaunal abundance and biomass, nematode and copepod abundance and environmental variables showed that meiofaunal abundance and biomass had significant negative correlations with bottom water temperature (BWT) and sediment silt-clay percentage. Copepod abundance also had significant negative correlations with BWT and silt-clay percentage while it had significant positive correlation with sediment median diameter. The results of BIOENV indicated that BWT, bottom water salinity, sediment water content, sediment chlorophyll a and phaeophorbide contents were the most important factors to influence meiofaunal assemblages.

[Effects of sewage discharge on abundance and biomass of meiofauna].

In order to elucidate the effects of sewage discharge on abundance and biomass of meio- fauna, a seasonal survey was carried out on meiofauna at stations with different distances to a sewage outlet in the middle intertidal zone of No. 1 bathing beach in Huiquan Bay, Qingdao in spring (April), summer (August), autumn (October) and winter (December), 2011. The results showed that the annual average meiofaunal abundance was (1859.9 ± 705.1) ind · 10 cm(-2), with higher values of (2444.9 ± 1220.5) ind · 10 cm(-2) at Station S2 (20 m to the sewage outlet) and (2492.2 ± 1839.9) ind · 10 cm(-2) at Station S3 (40 m to the sewage outlet), while the lowest value of (327.9 ± 183.2) ind · 10 cm(-2) was observed at Station S1 (0 m to the sewage outlet) in terms of horizontal distribution. The annual average biomass was (1513.4 ± 372.7) µg · 10 cm(-2). Meiofaunal abundance and biomass varied seasonally with the highest values in spring and the lowest values in summer. A total of 11 meiofaunal groups were identified, including nematodes, copepods, polychaetes, oligochaetes, tardigrades, halacaroideans, planarians, ostracods, isopods, crustacean nauplii and others. Free-living marine nematodes were the dominant group constituting 83. 1% of the total abundance, followed by benthic copepods, accounting for 12. 8% of the total abundance. In terms of vertical distribution, most of the meiofauna concentrated in the top 0-2 cm, and the meiofauna abundance decreased with increasing the sediment depth. Meiofauna was also noted to migrate deeper into the sediment in the winter. Pearson correlation analysis showed that meiofaunal abundance and biomass had highly significant negative correlations with sediment median particle diameter and organic matter content. In addition, tourism-induced activities affected meiofaunal abundance and distribution. A comparison with historical data from similar studies was carried out, and the applicability of the ratio of abundance of nematodes to copepods in monitoring organic pollution was discussed.

Nanotribological properties of precision-controlled regular nanotexture on H-passivated Si surface by current-induced local anodic oxidation.

Nano-sized textures resulted from localized electrochemical oxidation by using atomic force microscopy (AFM) were fabricated on H-passivated Si surface. In this paper, the fabrication and nanotribological properties of nanotexture by local anodic oxidation (LAO) on H-passivated Si surface are presented. A special attention is paid to find the relation between the size of oxide nanotexture and operational parameters such as tip-sample pulsed bias voltage, pulsewidth, and relative humidity to fabricate oxide nanotexture. The nanotribological properties were investigated by a colloidal probe. The results indicate that the nanotextures exhibited low adhesion and greatly reduced friction force at nanometer scale.