Fungal Degradation of Poly(l-lactide) in Soil and in Compost

The biodegradability of polymers by microorganisms is generally studied in a real environment that contains a natural mixture of fungi and bacteria. The present research mainly focused on the purely fungal degradation of poly(l-lactide), PLLA, to enclose the part of fungi in a real process of biodegradation and to understand the kinetics of biodegradation. Respirometric tests were realized in soil at 30?°C, and in compost at 30?and 58?°C. Results indicated that temperature is the predominant parameter governing the fungal degradation of PLLA. Moreover, in real compost, the biodegradation kinetics of the PLLA revealed a synergy between bacteria and fungi. The curves of PLLA and cellulose biodegradation were modeled by Hill sigmo?d. Fungal degradation was completed by investigating the physical and the chemical properties of the polymer during the process of degradation using several analytical methods such as matrix assisted laser desorption ionization-time of fly spectroscopy, infrared spectroscopy, size exclusion chromatography, and differential scanning calorimetry. These experiments led to a better understanding of the various stages of fungal degradation of PLLA: hydrolysis as well as mineralization. Furthermore, metabolizing products (by-products) of PLLA was investigated also.     

A multiobjective optimization framework for multicontaminant industrial water network design

The optimal design of multicontaminant industrial water networks according to several objectives is carried out in this paper. The general formulation of the water allocation problem (WAP) is given as a set of nonlinear equations with binary variables representing the presence of interconnections in the network. For optimization purposes, three antagonist objectives are considered: F(1), the freshwater flow-rate at the network entrance, F(2), the water flow-rate at inlet of regeneration units, and F(3), the number of interconnections in the network. The multiobjective problem is solved via a lexicographic strategy, where a mixed-integer nonlinear programming (MINLP) procedure is used at each step. The approach is illustrated by a numerical example taken from the literature involving five processes, one regeneration unit and three contaminants. The set of potential network solutions is provided in the form of a Pareto front. Finally, the strategy for choosing the best network solution among those given by Pareto fronts is presented. This Multiple Criteria Decision Making (MCDM) problem is tackled by means of two approaches: a classical TOPSIS analysis is first implemented and then an innovative strategy based on the global equivalent cost (GEC) in freshwater that turns out to be more efficient for choosing a good network according to a practical point of view.     

Expression of copper-resistance genes in microbial communities under copper stress and oxic/anoxic conditions

Microorganisms have developed copper-resistance mechanisms in order to survive in contaminated environments. The abundance and expression of the copper-resistance genes cusA and copA, encoding respectively for a Resistance Cell Nodulation protein and for a P-type ATP-ase pump, was assessed along a gradient of copper concentration in microcosms prepared from Seine estuary mudflat sediment. We demonstrated that the abundance of copA and cusA genes decreased with the increase of copper concentration and that cusA gene was up to ten times higher than the copA gene. Only the copA gene was expressed in both oxic and anoxic conditions. The abundance and activity of the microbial community remained constant whatever the concentrations of copper along the gradient. The molecular phylogeny of the two copper-resistance genes was studied and revealed that the increase of copper increased the diversity of copA and cusA gene sequences.     

Effects of medium-pressure UV lamps radiation on water quality in a chlorinated indoor swimming pool

The aim of our study was to determine the impact of medium-pressure UV lamps radiation on water quality in a chlorinated indoor swimming pool. An indoor swimming pool was equipped with two medium-pressure UV lamps. We collected eight samples of water daily over a four-weeks period and measured total and free chlorine, pH, water temperature, bacteriological parameters, total organic carbon and trihalomethanes. During the first week, which served as control, medium-pressure UV lamps were turned off. During the next three weeks, medium-pressure UV lamps were kept on 24 h per day. The third week, we reduced the level of the injected chlorine into water, and the last week we also reduced the water renewal volume by 27%. Our results showed that bacteriological parameters remained within allowable french limits. When medium-pressure UV lamps were kept on, total, free and active chlorine levels were significantly increased (P<0.001), whereas combined chlorine level were significantly decreased (P<0.001 and P<0.05, respectively). The levels of chloroform and bromodichloromethane were significantly increased when medium-pressure UV lamps were kept on (P<0.001), whereas chlorodibromomethane and bromoform levels significantly decreased (P<0.05 and P<0.001, respectively). The additional formation of chloroform and bromodichloromethane may be explained by the increase in active chlorine and by radicalizing mechanisms initiated by UV radiation.     

Heavy metal pollution and risks in a highly polluted and populated Indian river–city pair using the systems approach

Environmental Science and Pollution Research - A sectorial approach for assessing heavy metal pollution in rivers neglects the inter-relationship between its environmental compartments and thus...     

A DFT study of the reactions of O3 with Hg° or Br

In the mid 1980s the study of ozone reactivity gained a significant interest with the discoveries of the stratospheric ozone hole (Farman et al., 1985) and of the ozone depletion events in the polar boundary layer (Oltmans et al., 1989). In the stratosphere, the mechanism involves heterogeneous reactions on polar stratospheric clouds that lead to chlorine activation (Solomon et al., 1986). In contrast, tropospheric ozone depletion occurring during polar springtime rather involves reactive bromine species. They are released during a series of photochemical and heterogeneous reactions often called the bromine explosion (see the review of Simpson et al., 2007). In this reaction sequence, an essential step is the generation of photolyzable Br₂, the precursor of two Br atoms, via the multiphasic reaction (1):

(1)

HOBr + Br⁻ + H⁺ → H₂O + Br₂

The production of reactive HOBr could occur with the oxidation of BrO by HO₂.     

Bacterial community composition characterization of a lead-contaminated <Emphasis Type="Italic">Microcoleus</Emphasis> sp. consortium

Introduction  

A Microcoleus sp. consortium, obtained from the Ebro delta microbial mat, was maintained under different conditions including uncontaminated, lead-contaminated, and acidic conditions.     

Strategies for reducing the environmental impact of reprocessing mercury-contaminated tailings in the artisanal and small-scale gold mining sector: insights from Tapajos River Basin,Brazil

Worldwide, the environmental impacts of artisanal and small-scale gold mining (ASGM) are extensive. Annual losses from mercury, which is used to amalgamate gold, are in the range of 1000 tonnes, and at advanced sites, there is the additional threat of cyanide contamination.Recent developments in The Brazilian Amazon, an area populated by 200,000 small-scale gold miners, have the potential to reduce these impacts considerably. In the locality of Garimpo Ouro Roxo, miners are presently using amalgamation and cyanidation in vat-leaching. Each cycle typically recovers 50% of the gold and lasts 20 days (per tank), consuming around 3300 kg NaCN/month. A new process has been developed and implemented in a pilot plant in this area, involving gravity concentration followed by cyanidation in a ball mill. Concentrate leaching is conducted with a PVC capsule filled with activated carbon inserted in the cyanide solution in the mill. The cycle takes less than 24 h and recovers up to 98% of the gold in the concentrate. The main advantages of wide adoption of this method, apart from a reduced gold recovery cycle and improved recovery, include possible phase out of amalgamation altogether, and marked reductions in cyanide consumption (from current 22,000 kg–980 kg annually).