Mechanisms of biodegradation of dibenzoate plasticizers

Biodegradation mechanisms were elucidated for three dibenzoate plasticizers: diethylene glycol dibenzoate (D(EG)DB), dipropylene glycol dibenzoate (D(PG)DB), both of which are commercially available, and 1,6-hexanediol dibenzoate, a potential green plasticizer. Degradation studies were done using Rhodococcus rhodochrous in the presence of pure alkanes as a co-substrate. As expected, the first degradation step for all of these systems was the hydrolysis of one ester bond with the release of benzoic acid and a monoester. Subsequent biodegradation of the monobenzoates of diethylene glycol (D(EG)MB) and dipropylene glycol (D(PG)MB) was very slow, leading to significant accumulation of these monoesters. In contrast, 1,6-hexanediol monobenzoate was quickly degraded and characterization of the metabolites indicated that the biodegradation proceeded by way of the oxidation of the alcohol group to generate 6-(benzoyloxy) hexanoic acid followed by β-oxidation steps. This pathway was blocked for D(EG)MB and D(PG)MB by the presence of an ether function.The use of a pure hydrocarbon as a co-substrate resulted in the formation of another class of metabolites; namely the esters of the alcohols formed by the oxidation of the alkanes and the benzoic acid released by hydrolysis of the original diesters. These metabolites were biodegraded without the accumulation of any intermediates.     

空气污染对儿童及其父母呼吸系统健康的影响

 根据空气污染数据对广州、武汉、兰州、重庆4城市8个点位进行了空气污染的聚类分析,并按空气污染程度进行了排序.在此基础上,分析了空气污染程度与儿童及其父母呼吸系统健康的关系.发现儿童11种患病率随空气污染程度加重而呈上升趋势.污染最重组的患病率是污染较轻组的1.71(3.95倍.污染最重组的比数比(即OR值)是污染较轻组的3.313(6.942倍.空气污染对儿童父母的呼吸系统患病率也有轻度至中度的影响.     

Incineration of kitchen waste with high nitrogen in vortexing fluidized-bed incinerator and its NO emission characteristics

Some municipal solid waste (MSW) can be used as the fuel. Combustion of MSW with high nitrogen content is successfully conducted in a lab-scale vortexing fluidized-bed incinerator (VFBI). Pigskin with 16.5 wt.% nitrogen content was used to simulate the high nitrogen content kitchen waste, and silica sand was used as the bed material. The effects of operating conditions, such as the bed temperature, freeboard temperature, excess oxygen ratio, and static bed height on the CO and NO concentrations at the exit of combustor and cyclone were investigated. The experimental results show that the freeboard temperature is the most important factor for CO emission. The order of operating conditions impact on the NO emission is: (1) excess oxygen ratio; (2) bed temperature; (3) freeboard temperature; and (4) static bed height. Utilizing cyclone can significantly reduce the CO emission concentration when the CO concentration released from the freeboard is higher than 50 ppm. On the other hand, the cyclone has no significant effect on the NO emission. Despite having high nitrogen content, a low conversion from fuel-N to NO was attained. Compared with other types of combustors, VFBI reduces the CO and NO emission concentrations much better when burning MSW with high nitrogen content.     

Drastic decline of an extensive eelgrass bed in Nova Scotia due to the activity of the invasive green crab (Carcinus maenas)

In 2001–2002, there were severe declines of eelgrass (Zostera marina) in estuaries along the Nova Scotia coast of the southern Gulf of St. Lawrence. We examined the relationship between the recent invasion of European green crabs (Carcinus maenas) and the eelgrass decline in Benoit Cove in Tracadie Harbour. The abnormally abundant eelgrass wrack consisted mainly of entire shoots, not the usual blades. Three separate methods yielded similar estimates of the rate of shoot removal from the eelgrass beds (direct quadrat counts, “mark–recapture” of tagged shoots in the eelgrass bed, and rate of shoot appearance in the shore wrack). From 14 July to 8 September 2002, the shoot density in the bed fell by about 75 %. Similar rates of decline occurred in crab enclosures (4.4 crabs m^?2) placed in the eelgrass bed. Green crab foraging, involving the tearing of shoots and the digging of large pits, was the reason for the drastic decline of the eelgrass bed in Benoit Cove. It is clear that an invasion of green crabs to a region where they had not previously existed can both destroy eelgrass beds and restrict their recovery.     

What’s the Problem? River Management,Education, and Public Beliefs

This paper invokes the theory of planned behavior (TPB) as a diagnostic tool to explain an existing public education program's limited success at improving river water quality in the City of Perth, Western Australia. A reflective, client-driven research approach was used. A facilitated expert workshop defined an environmental problem (excess nutrients leaving gardens and entering waterways) and a desired behavior (residents purchasing environmentally sensitive fertilizer) to address the problem. A TPB-based belief elicitation survey captured respondents' beliefs regarding the desired behavior. The findings suggest respondents were aware of the links between purchasing environmentally sensitive fertilizer and river water quality. However, this behavior is compromised by the challenges in identifying appropriate products, product quality concerns, and cost. Viewing the content of a public education program through the lens of the TPB reveals insights into how and why the program fell short in achieving one of its key behavioral change goals.     

Factor Biases and Promoting Sustainable Development: Adaptation to Drought in the Senegal River Basin

The ongoing drought in the Sahel region of West Africa highlights the vulnerability of food-producing systems to climate change and variability. Adaptation to climate should therefore increase the sustainability of agriculture under a long-term drought. Progress towards sustainability and adaptation in the the Senegal River Basin is hampered by an existing set of social and ecological relationships that define the control over the means of production and how people interact with their environment. These relationships are sensitive to the technological inputs and the administration of food production, or the factor bias in the different policy alternatives for rural development. One option is based on state-controlled, irrigated plantations to provide rice (Oryza) for the capital, Dakar. This policy emphasizes a top-down management approach, mechanized agriculture and a reliance on external inputs which strengthens the relationships introduced during the colonial period. A time series decomposition of the annual flow in the Senegal River at Bakel in Senegal suggests that water resources availability has been substantially curtailed since 1960, and a review of the water resources budget or availability in the basin suggests that this policy's food production system is not sustainable under the current climate of the basin. Under these conditions, this program is exacerbating existing problems of landscape degradation and desertification, which increases rural poverty. A natural resource management policy offers two adaptation strategies that favour decentralized management and a reduction of external inputs. The first alternative, “Les Perimetres Irrigués”, emphasizes village-scale irrigation, low water consumption cereal crops and traditional socio-political structures. The second alternative emphasizes farm-level irrigation and agro-forestry projects to redress the primary effects of desertification.     

Remedial Process Optimization and Ozone Sparging for Petroleum Hydrocarbon‐Impacted Groundwater

A former natural gas processing station is impacted with total petroleum hydrocarbons (TPH) and benzene. Remedial process optimization (RPO) was conducted to evaluate the effectiveness of the historical air sparging/soil vapor extraction (AS/SVE) system and the current groundwater extraction and treatment system. The RPO indicated that both remedial activities offered no further benefit in meeting remediation goals. Instead, an in situ chemical oxidation (ISCO) system was recommended. Ozone was selected, and the results of a bench test indicated that the ozone demand was 8 to 12 mg ozone/mg TPH and that secondary by‐products would include hexavalent chromium and bromate. A capture zone analysis was conducted through groundwater flow modeling (MODFLOW) to ensure containment of the injected oxidant using the existing groundwater extraction system. Results of a pilot study indicated that the optimum frequency of ozone sparging is 60 minutes in order to reach a maximum radius of influence of 20 feet. TPH concentrations within the treatment zone decreased by 97 percent over two months of ozone sparging. Concentrations of hexavalent chromium and bromate increased from nondetect to 44 and 110 mg/L, respectively, during the ozone sparging but attenuated to nondetectable concentrations within three months of system shut down. ©2016 Wiley Periodicals, Inc.     

Sustainable Remediation Considerations for Treatment of 1,4‐Dioxane in Groundwater

1,4‐Dioxane remediation is challenging due to its physiochemical properties and low target treatment levels. As such, applications of traditional remediation technologies have proven ineffective. There are a number of promising remediation technologies that could potentially be scaled for successful application to groundwater restoration. Sustainable remediation is an important consideration in the evaluation of remediation technologies. It is critically important to consider sustainability when new technologies are being applied or new contaminants are being treated with traditional technologies. There are a number of social, economic, and environmental drivers that should be considered when implementing 1,4‐dioxane treatment technologies. This includes evaluating sustainability externalities by considering the cradle‐to‐grave impacts of the chemicals, energy, processes, transportation, and materials used in groundwater treatment. It is not possible to rate technologies as more or less sustainable because each application is context specific. However, by including sustainability thinking into technology evaluations and implementation plans, decisions makers can be more informed and the results of remediation are likely to be more effective and beneficial. There are a number sustainable remediation frameworks, guidance documents, footprint assessment tools, life cycle assessment tools, and best management practices that can be utilized for these purposes. This paper includes an overview describing the importance of sustainability in technology selection, identifies sustainability impacts related to technologies that can be used to treat 1,4‐dioxane, provides an approximating approach to assess sustainability impacts, and summarizes potential sustainability impacts related to promising treatment technologies. ©2016 Wiley Periodicals, Inc.     

Application of the electrochemical speciation of heavy metals in tracking groundwater pollution

The application of the electrochemical speciation of heavy metals in tracking groundwater is presented. Three fractions interchangeable, associated to the organic materials and associated to the matter in suspension of the metals Zn, Cd, Pb and Cu by means of the anodic stripping voltammetry were determined. The parameters of the determination were: electrodeposition potential ‐1.2 V, time of deaerating with nitrogen 300 s, time of the electrolysis 90 s (with stirring) and the rest time 40 s. The core of this work was to determine the validity of this scheme of electrochemical speciation in the pursuit of the follow‐up of groundwater pollution caused by heavy metals after the breakdown of the mining raft at the River Guadiamar Basin (Andalusia, Spain).     

Agricultural chemical exposure in small farmers in Guyana

A study of self-reported injury from agricultural chemical exposure was conducted in farmers in rural Guyana. One hundred and ninety agricultural workers were studied, of which 167 (88%) were male. Morbidity from agricultural chemical exposure was common, with 87 farmers (46%) reporting having experienced at least one episode of illness after agricultural chemical exposure. Relatively few of the farmers sought medical assistance for their symptoms, with only 20 farmers (11%) visiting a local doctor and only two farmers (1%) reporting going to a hospital for treatment. Local farmer use of protective equipment was limited. Pyrethroids and herbicides paraquat and glyphosate were the most commonly used agricultural chemicals in the population studied. Data showed that exposure to agricultural chemicals remains frequent, with incidence of severe injury requiring less frequent medical attention.