Effects of organic carbon content on in situ remediation time using steam–air injection

Groundwater contamination by chlorinated hydrocarbons (CHC) is a common phenomenon that poses health risks to both humans and animals. These halogenated hydrocarbons infiltrate into the soil matrices and form pools at the bottoms of the aquifers thus contaminating the groundwater sources. Thermally enhanced soil vapour extraction (TSVE) using steam–air injection has gained popularity as an alternative technique to remediate the saturated and vadose source zones contaminated with CHC. This technique has been successfully applied in the remediation of contaminated sites (brownfields, industrial sites) and groundwater. However, the presence of organic carbon (OC) contents within the soil matrices has not been intensively studied. This paper, therefore, intends to contribute toward increasing the understanding of the effects of OC on the remediation time using TSVE. A 2-D flume experimental model was conducted in VEGAS laboratory using coarse sand, fine sand and silty soil with 0, 1 and 2% addition of the activated carbon as OC to investigate the desorption time of PCE and TCE as CHC during TSVE extraction using steam–air injection. 100 kg of soil mixed with the activated carbon was treated with 50 g TCE and 50 g PCE and then remediated using TSVE. The remediation times were recorded and recovered CHC was documented. It was discovered that the presence of OC enhanced the adsorption of the CHC onto the soil matrices thereby increasing the time required for the complete remediation of the contaminant from the soil. An increase of OC by 1% resulted in desorption time by a factor of 4–7.

Performance and Mechanism of the in-situ Restoration Effect on VHCs in the Polluted River Water Based on the Orthogonal Experiment: Photosynthetic Fluorescence Characteristics and Microbial Community Analysis.

Volatile halogenated hydrocarbons (VHCs) attracted many attentions due to its toxic and persistent in the environment. In this research, a novel in situ ecological restoration reactor was applied to the degradation of VHCs in polluted river water. The optimized working condition adaptation of the in-situ restoration technique was evaluated through orthogonal tests. The experiments showed that when the water depth was 0.4 m, the HRT was 5d and the current velocity was 1 m/s, VHCs removal efficiencies could achieve favorable value. The CHCl3 CCl4, C2HCl3 and C2Cl4 removal efficiency could reach 70.27%, 70.59%67.74% and 81.82%, respectively. F test results showed that both HRT and water depth were significantly related to the removal efficiency of reactor. Besides, using underwater modulated chlorophyll fluorometer analyzed the rapid light curves (RLC) of plants in the experiment, which showed that the VHCs of damaged river was harmful to the physiological state of the plants. Moreover, the microbial community structures of fillers in the reactor were tested by high-throughput sequencing, the findings supported that the microbial community made a great response to adapt to the changes of environment of the reactor. The relative abundance of Rhodocyclaceae increased slightly, which hinted that it had good adaptability to VHCs in polluted river water. The research results confirmed that in situ ecological restoration reactor was an economical technology for removal VHCs in polluted river water.

Insight into the environmental monitoring and source apportionment of volatile organic compounds (VOCs) in various functional areas

Atmospheric aerosol contamination has caused widespread concern about human and environmental health. However, research about VOCs as an important precursor of secondary aerosols in ambient air is still limited. In this study, VOCs at sites from three typical functional areas in Hefei, China, were monitored using GC–MS/FID. The VOCs in ambient air from different functional areas showed significantly different characteristics. The highest concentrations and the biggest diurnal difference of VOCs were found in the High-tech Zone (industrial area) with serried emission sources. Additionally, lower VOC concentration was observed in Changjiang West Road, the center area of studied city. The VOC concentration in this area is strongly related to other pollutants. The composition of VOCs at all sampling sites showed certain common characteristics, i.e., alkanes, OVOCs, and halogenated hydrocarbons account for more than 75% of the total VOCs’ quality. The High-tech Zone with the highest concentration of VOCs also has the highest proportion of alkanes. Besides, the positive matrix factorization analysis results revealed that vehicle exhaust, LPG volatilization sources, and chemical solvents were the most important VOC emission sources in Hefei. In terms of the contribution of VOC components to the OFP at the three sites, the olefins and alkynes at the Changjiang West Road site and the Science Island site contribute the most significant proportion. In contrast, the OVOCs at the High-tech Zone site contribute the largest proportion.

Mangrove Ecosystem, Seagrass, Coral Reef: its Role in Self-Purification and Carrying Capacity in Coastal Areas

The coast is an area that has very high activity. It is estimated that 60% of the world's population lives in coastal areas. Various types of pollution enter this area. Halogenated hydrocarbons, pesticides, marine biotoxins, synthetic fertilizers, livestock and fishery waste, heavy metals, hot water discharges and radioactive substances. Coastal areas are natural ecosystems built by unique ecosystems including mangrove forests, seagrass beds and coral reefs. The three ecosystems interact dynamically and are interdependent. One of the characteristics of natural ecosystems is the ability to self-purify so that their carrying capacity is optimal. The coastal self-purification capacity is built by the synergy between the physical, chemical and biological components as well as their hydrological-morphological components. The self-purification mechanism includes filtration, transformation, degradation and decomposition. Self-purification is the ability of coastal ecosystems to accept a certain amount of waste in a complex natural process and before there is an indication of a decrease in its intended function. The implementation of self-purification effectively will support the optimization of carrying capacity, namely the ability of the ecosystem to support the life of the population. There are three factors related to carrying capacity, namely the availability of natural resources, population and consumption levels.

Indoor pet allergen exposures modify the effects of chemical air pollutants on respiratory symptoms

SETTING: Indoor volatile organic compound (VOC) levels, which are generally correlated with each other, may have an additive or synergistic effect on health. VOC synergy with allergens is a suspected mechanism affecting respiration.OBJECTIVE: To determine the effect of exposure to interactions between VOCs and allergens on respiratory symptoms in individuals aged ≥15 years.DESIGN: A national cross‐sectional survey measured 20 VOCs and dog and cat aeroallergens in 490 main residential dwellings in France. A standardised questionnaire was used to elicit responses on respiratory conditions in 1012 inhabitants. Four VOC factor scores (linear combinations of VOCs) were generated using principal component analysis. In order to take into account the phenomenon of multi‐pollution, marginal models were used to model the relationships between exposure to VOC mixture and respiratory conditions. Stratified models were used to examine the interaction between allergens and VOCs.RESULTS: The aromatic hydrocarbon score was associated with rhinitis and wheezing, the aliphatic hydrocarbon score with asthma and cough, the halogenated hydrocarbons with asthma, wheezing and rhinitis. Aldehydes and Can f1 had a significant synergistic effect on wheezing and rhinitis. Aliphatic hydrocarbons had an antagonist effect with Can f1 on wheezing.CONCLUSION: Our data support evidence of adverse effects of exposure to VOC mixture on respiratory conditions; this effect is aggravated in the presence of pet allergens.

Hepatoprotective activity against acetaminophen-induced liver dysfunction and GC-MS profiling of a brown algae Sargassum ilicifolium

Background Drug-induced hepatotoxicity is one of the most important causes of liver dysfunction. Acetaminophen (paracetamol) an analgesic-antipyretic drug is generally considered safe but its overdose may cause liver toxicity. Marine macro-algae (seaweeds) especially brown seaweeds possess unique biological activities including hepatoprotective potential. The current study focused on the hepatoprotective effect of different solvent fractions of Sargassum ilicifolium and characterization of its n-hexane soluble fraction. Methods The ethanol extract (20 g) of S. ilicifolium was mixed with solvents of increasing polarity, starting with n-hexane followed by chloroform and methanol. All three (n-hexane, chloroform and methanol) soluble fractions were administered to the rats at dose of 150 mg/kg, b.w. Intraperitoneal administration of acetaminophen (600 mg/kg b.w.) to rats was used to cause liver injury. The hepatic damage was evaluated by liver markers enzymes; aspartate aminotransferases (AST), alanine aminotransferases (ALT), alkaline phosphatase (ALP), lactate dehydrogenase (LDH), bilirubin along with other metabolites i.e., triglycerides, cholesterol, urea, glucose and creatinine. Lipid peroxidation and glutathione and were estimated in liver tissue. n-Hexane fraction was subjected to GC-MS analysis in order to identify potent compounds. Results The oral administration of n-hexane and methanol soluble fractions reduced the acetaminophen-augmented liver marker enzymes ALT, AST, ALP, LDH, along with bilirubin, urea, creatinine, glucose and triglycerides. The n-hexane and methanol soluble fractions also improved hepatic antioxidant level via enhancing hepatic glutathione and reversing lipid peroxidation. GC-MS spectroscopy of n-hexane fraction of S. ilicifolium revealed the presence of some new compounds. Among them, fatty acids were found to be in highest concentration followed by halogenated hydrocarbons, benzene derivatives, and sterols. Fatty acid in seaweed may be one of the factors for hepatoprotection from drug-induced hepatotoxicity. Conclusion From the results, it is evident that n-hexane and methanol soluble fractions of S. ilicifolium have the ability to protect the liver against toxicity, which is comparable with silymarin used as a standard drug. Sargassum ilicifolium contains bioactive compounds with pharmaceutical importance.

Reductive Cytochrome P450 Reactions and Their Potential Role in Bioremediation

Cytochrome P450 enzymes, or P450s, are haem monooxygenases renowned for their ability to insert one atom from molecular oxygen into an exceptionally broad range of substrates while reducing the other atom to water. However, some substrates including many organohalide and nitro compounds present little or no opportunity for oxidation. Under hypoxic conditions P450s can perform reductive reactions, contributing electrons to drive reductive elimination reactions. P450s can catalyse dehalogenation and denitration of a range of environmentally persistent pollutants including halogenated hydrocarbons and nitroamine explosives. P450-mediated reductive dehalogenations were first discovered in the context of human pharmacology but have since been observed in a variety of organisms. Additionally, P450-mediated reductive denitration of synthetic explosives has been discovered in bacteria that inhabit contaminated soils. This review will examine the distribution of P450-mediated reductive dehalogenations and denitrations in nature and discuss synthetic biology approaches to developing P450-based reagents for bioremediation.

Occurrence, Potential Sources, and Risk Assessment of Volatile Organic Compounds in the Han River Basin, South Korea

Increasing public awareness about the aesthetics and safety of water sources has shifted researchers’ attention to the adverse effects of volatile organic compounds (VOCs) on humans and aquatic organisms. A total of 17 VOCs, including 10 volatile halogenated hydrocarbons and seven volatile non-halogenated hydrocarbons, were investigated at 36 sites of the Han River Basin, which is the largest and most important drinking water source for residents of the Seoul metropolitan area and Gyeonggi province in South Korea. The VOC concentrations ranged from below detection limits to 1.813 µg L−1. The most frequently detected VOC was 1,2-dichloropropane, with a detection frequency of 80.56%, as it is used as a soil fumigant, chemical intermediate, and industrial solvent. In terms of geographical trends, the sampling sites that were under the influence of sewage and industrial wastewater treatment plants were more polluted with VOCs than other areas. This observation was also supported by the results of the principal component analysis. In the present study, the detected concentrations of VOCs were much lower than that of the predicted no-effect concentrations, suggesting low ecological risk in the Han River. However, a lack of available ecotoxicity data and limited comparable studies warrants further studies on these compounds.