Shape-dependent bactericidal activity of TiO2 for the killing of Gram-negative bacteria Agrobacterium tumefaciens under UV torch irradiation

This paper demonstrated the relative bactericidal activity of photoirradiated (6W-UV Torch, λ?>?340 nm and intensity?=?0.64 mW/cm²) P25–TiO₂ nanoparticles, nanorods, and nanotubes for the killing of Gram-negative bacterium Agrobacterium tumefaciens LBA4404 for the first time. TiO₂ nanorod (anatase) with length of 70–100 nm and diameter of 10–12 nm, and TiO₂ nanotube with length of 90–110 nm and diameter of 9–11 nm were prepared from P-25 Degussa TiO₂ (size, 30–50 nm) by hydrothermal method and compared their biocidal activity both in aqueous slurry and thin films. The mode of bacterial cell decomposition was analyzed through transmission electron microscopy (TEM), Fourier transform-infrared (FT-IR), and K⁺ ion leakage. The antimicrobial activity of photoirradiated TiO₂ of different shapes was found to be in the order P25–TiO₂?>?nanorod?>?nanotube which is reverse to their specific surface area as 54?<?79?<?176 m² g^?1, evidencing that the highest activity of P25–TiO₂ nanoparticles is not due to surface area as their crystal structure and surface morphology are entirely different. TiO₂ thin films always exhibited less photoactivity as compared to its aqueous suspension under similar conditions of cell viability test. The changes in the bacterial surface morphology by UV-irradiated P25–TiO₂ nanoparticles was examined by TEM, oxidative degradation of cell components such as proteins, carbohydrates, phospholipids, nucleic acids by FT-IR spectral analysis, and K⁺ ion leakage (2.5 ppm as compared to 0.4 ppm for control culture) as a measure of loss in cell membrane permeability.     

Determining distribution coefficients for low cost adsorbents

As with other construction materials, coal fly ash contains trace metals that can leach into the natural environment. As part of a broader effort to encourage appropriate coal combustion product use in infrastructure applications (e.g., road construction, stabilization, and structural fill), this study evaluated traditional and low‐cost adsorbent alternatives for their capacity to attenuate trace metals. Batch sorption tests were used as a preliminary screen for a wide variety of low cost (e.g., steel byproducts, rubber dust, and compost) and innovative materials (e.g., kudzu, biofilm, and pond weed) as well as conventional materials (activated carbon, alumina, and zeolites). The removal rates were demonstrated in this study by observing the calculated distribution coefficient (K_d) which were determined using a program called MATLAB. Limestone and steel byproducts were found to be particularly effective with large K_d values of 15,740, 1,520, and 540 L kg^?1 for cadmium, chromium, and selenium and, for ladle refractory and mill scale, K_d values of 3,910, 670, and 1,760 L kg^?1 were observed. Among the three metals tested for this study, it was observed that most low cost and innovative materials removed cadmium quite efficiently; however, the removal of selenium and chromium depended on the substrate and prevailing pH. In general, these results suggest that alternative materials may have relevance in niche applications where leaching is a concern that can be addressed through enhanced attenuation capacity via blending or layering of adsorbents.     

Wet scrubber analysis of volatile organic compound removal in the rendering industry

The promulgation of odor control rules, increasing public concerns, and U.S. Environmental Protection Agency (EPA) air regulations in nonattainment zones necessitates the remediation of a wide range of volatile organic compounds (VOCs) generated by the rendering industry. Currently, wet scrubbers with oxidizing chemicals are used to treat VOCs; however, little information is available on scrubber efficiency for many of the VOCs generated within the rendering process. Portable gas chromatography/mass spectrometry (GC/MS) units were used to rapidly identify key VOCs on-site in process streams at two poultry byproduct rendering plants. On-site analysis was found to be important, given the significant reduction in peak areas if samples were held for 24 hr before analysis. Major compounds consistently identified in the emissions from the plant included dimethyl disulfide, methanethiol, octane, hexanal, 2-methylbutanal, and 3-methylbutanal. The two branched aldehydes, 2-methylbutanal and 3-methylbutanal, were by far the most consistent, appearing in every sample and typically the largest fraction of the VOC mixture. A chlorinated hydrocarbon, methanesulfonyl chloride, was identified in the outlet of a high-intensity wet scrubber, and several VOCs and chlorinated compounds were identified in the scrubbing solution, but not on a consistent basis. Total VOC concentrations in noncondensable gas streams ranged from 4 to 91 ppmv. At the two plants, the odor-causing compound methanethiol ranged from 25 to 33% and 9.6% of the total VOCs (v/v). In one plant, wet scrubber analysis using chlorine dioxide (ClO2) as the oxidizing agent indicated that close to 100% of the methanethiol was removed from the gas phase, but removal efficiencies ranged from 20 to 80% for the aldehydes and hydrocarbons and from 23 to 64% for total VOCs. In the second plant, conversion efficiencies were much lower in a packed-bed wet scrubber, with a measurable removal of only dimethyl sulfide (20-100%).     

Microplastics pollution in Bangladesh: current scenario and future research perspective

ABSTRACT

Microplastics are emerging environmental pollutants that have gained tremendous scientific interest in recent years. These micropollutants are omnipresent both in the terrestrial and aquatic environments posing a deleterious threat to the ecosystem and biodiversity. So, it is important to develop a deep understanding of the environmental fate and potential adverse impacts of microplastics on the aquatic and terrestrial environments. By critically reviewing the previously published scientific literature, the present synthesis briefly outlines the characteristics, occurrence and potential toxic effects of microplastics on terrestrial and aquatic biota. The article also focuses on some innovative approaches for sustainable remediation of macroplastics as well as microplastics. Since the concept of microplastics pollution has yet in its infancy in Bangladesh, this synthesis provides an overview of the current scenario of microplastics pollution and some future research recommendations in the context of Bangladesh which might be helpful to the novice researchers of this field.     

Sources,controls, and probabilistic health risk assessment of fluoride contamination in groundwater from a semi-arid region in Gujarat,Western India: An isotope–hydrogeochemical perspective

Environmental Geochemistry and Health - Fluoride contamination in groundwaters of a rural region in semi-arid Western India has been studied using combination of geochemical-and-isotopic...     

Suppression of inhibition of substrate photodegradation by scavengers of hydroxyl radicals: the solvent-cage effect of bromide on nitrate photolysis

In this paper we show that bromide scavenges the ^·OH radicals formed upon photolysis of nitrate, before they leave the solvent cage. Bromide can thus inhibit the in-cage recombination between ^·OH and ^·NO₂. The consequence is an increased generation of ^·NO₂ and nitrite and of Br₂ ^?· + ^·OH, compared to ^·OH alone in the absence of bromide. We show that this effect compensates for the lower reactivity of Br ₂ ^?· compared to ^·OH toward certain organic substrates, e.g. phenol and tryptophan. Our findings could lead to a deep revision of the present views of the role of bromide in saltwater photochemistry.     

Consequences of manganese compounds: a review

Manufacturing of manganese (Mn) compounds, their industrial applications as well as mining overburden, has generated a potential environmental pollutant. Occupational exposure to elevated levels of Mn occurs during mining, welding, smelting and other industrial anthropogenic sources. Chronic and acute exposure of this metal pollutant leads to adverse consequences and is clinically categorized by various symptoms of neurotoxicity including cognitive, psychiatric symptoms, Parkinson's disease, extra pyramidal signs, manganism, dystonia, and motor system dysfunction. The aim of this review is to summarize the possible mechanism underlying Mn compounds-mediated neurotoxicity leading to neurodegenerative diseases. Our review endeavours to examine recent advances in research on Mn-related environmental pollution, Mn-induced poisoning, molecular mechanisms underlying Mn-induced neurotoxicity with case studies as well as current approaches employed for treatment and prevention of Mn exposure.     

Toxicity of cadmium nanoparticles to Bacillus subtilis

The study deals with the toxicological impact of cadmium nanoparticles (Cd NPs) on Bacillus subtilis as a model Gram-positive bacterium. Cadmium oxide (CdO) NPs (～22 nm) and cadmium sulfide (CdS) NPs (～3 nm) were used in this study. Both the NPs were found to inhibit the cell viability of B. subtilis when added to the culture at mid-log phase, the viable cell number declined with increasing concentration of Cd NPs. At mid-log phase, 15 mg L^?1 CdO NPs inhibited growth by ～50%, whereas at 30 mg L^?1 growth completely ceased. Under the same conditions, CdS NPs inhibited growth by ～50% at a concentration of 8 mg L^?1, and at 20 mg L^?1 growth was completely retarded. The cells changed their morphological features to a filamentous form with increasing Cd NPs exposure time, leading to associated with clumping. NPs treated cells when stained with 4′, 6-diamino-2-phenylindole, showed filamentous multinucleated bead structure, suggesting irregularities in cell division. Increasing intracellular oxidative stress due to Cd NPs exposure might be one of the reasons for the cell morphological changes and toxicity in B. subtilis.     

Natural radioactivity and radiation exposure in the high background area at Chhatrapur beach placer deposit of Orissa, India

A high natural background radiation area is reported for the Chhatrapur beach placer deposit of Orissa state, on the southeastern coast of India, due to the presence of radiogenic heavy minerals. The average activity concentrations of radioactive elements 232Th, 238U and 40K were measured by gamma-ray spectrometry using a HPGe detector, and found to be 2500 +/-1850, 230 +/- 140 and 120 +/- 35 Bq kg-1, respectively, for the bulk sand samples. The absorbed gamma dose rates in air due to the naturally occurring radionuclides varied from 375 to 5000 nGy h-1, with an average value of 1625 +/- 1200 nGy h-1. The external annual effective dose rate of the region ranged from 0.46 to 6.12 mSv y-1, with an average value of 1625 +/- 1200 mSv y-1. The absorbed gamma dose rate levels of Chhatrapur beach area were similar to the monazite sand-bearing high background radiation areas of southern and southwestern coastal tracts of India and other similar areas of the world. The major contributors to the enhanced level of radiation are monazite and zircon sands.