Influence of some abiotic environmental factors on acute toxicity of inorganic lead to Cyprinus carpio var communis (Linn.) and Catla catla (Ham.) in simulated toxic aquatic environment

With the increase of water hardness from 60 to 720?mg/L CaCO₃, total alkalinity from 32 to 376?mg/L CaCO_3, pH from 7.6 to 7.9 and chloride from 28 to 350?mg/L, 96?h LC₅₀ on the basis of total lead increased from 8.2 to 1291?mg/L for Cyprinus carpio and 5.3 to 865?mg/L for Catla catla, when soil sediments were included these values were further raised to 1356 and 874?mg/L, respectively. The dissolved lead LC₅₀ values in all the treatments of soil and water was consistent with fixed amount of dissolved lead (1.04–1.78?mg/L) being needed for median lethal toxicity. Total lead toxicity also decreased with increase in pH from 6.3 to 11.3. 96?h LC₅₀ values increased for common carp 15 to 631?mg/L and for catla, 8 to 355?mg/L. But dissolved lead toxicity was found to increase with the increase of pH from 6.3 to 11.3 for both common carp (LC₅₀, 3.53 to 0.24?mg/L) and catla (LC₅₀, 2.21 to 0.09?mg/L). Removal of dissolved Pb with increasing carbonate content, particulate matter and pH due to adsorption, precipitation or coprecipitation reaction, reduced the dissolved lead concentration and thus the total lead toxicity. Increase in toxicity of lead with increase of exposure time was the biological response of longer contact time and decrease in dissolved lead toxicity with decrease in pH was due to increase H⁺ ion competition.     

The microcystins-induced DNA damage in the liver and the heart of zebrafish,Danio rerio

Microcystins (MCYST) are the freshwater cyanobacterial toxins, known to induce hepatocellular carcinoma, necrosis, intrahepatic bleeding, as well as human and livestock mortality. Within hepatocytes, MCYST selectively bind to protein phosphatases 1 and 2A, resulting in severe liver damage. The toxicology of MCYST in mice and rats has been well studied, but little is known regarding genotoxicity in aquatic animals. In this study, the zebrafish, Danio rerio was exposed to crude extract of Microcystis aeruginosa bloom. Liver and heart were examined for MCYST-induced toxicity. Light microscopy at 36?h revealed severe, widespread apoptotic necrosis of the majority of hepatocytes, and cytoskeletal deformation in myocardiocytes. Hepatocytes were dissociated with cell shrinkage and margination of nuclear chromatin. Laddering of genomic DNA from the liver and heart of the exposed fish in an increment of 180–200?bp was consistent with apoptosis. Fluorimetric analysis of DNA unwinding was carried out to determine the DNA strand breakage. After 36?h exposure, the % double-stranded DNA was significantly reduced in hepatocytes and myocardiocytes. In conclusion, the results obtained in this study indicate that, the extract of M. aeruginosa bloom is genotoxic to fish. The DNA damage observed in this study may be attributed to the activation of DNA endonucleases. This model of DNA damage may contribute for identifying novel molecular mechanisms of interest for therapeutic application.     

Persistence and dissipation of dazomet in soil and tomato (lycopersicon esculentum mill) seedlings

The persistence and dissipation pattern of dazomet residues in nursery bed soil and tomato seedlings under field condition and in submerged soil and surface water under laboratory condition was studied. In nursery bed soil the half life (t _1/2) of dazomet ranged from 1.85 to 3.09 days indicating very rapid dissipation. No residues existed in tomato seedlings sown on the treated plots 3 weeks after application and the seedlings were healthy and devoid of any deformation. Under submerged condition dissipation was much faster both in soil and surface water, t_1/2 being 0.82–0.84 days only in water.     

Watershed land use as a determinant of metal concentrations in freshwater systems

Concentrations of Fe, Mn, Cu, dissolved organic matter (DOM), and pH were synthesized from 30 publications to determine the factors regulating concentrations and behavior of metals in freshwater systems. Results from the review suggest that contrasting watershed land use can directly (erosion and runoff) and indirectly (in-lake processes including metal–DOM–pH interactions) affect the metal concentrations in freshwater systems. Among the watershed land uses considered here, concentrations of Fe, Mn, and Cu were observed in the following order: arctic lakes < forested < agricultural < urbanized < mined. A drastic difference in mean metal concentrations has been observed when undisturbed or low impact watersheds (arctic and forested) were changed by agricultural, urban, and mining developments. Relationships between metal concentrations and pH revealed that metals precipitate at high pH (pH > 5). Additionally, at pH < 5, metal concentrations were significantly correlated with DOM due to metal–DOM complexation. High ratios of metal: DOM occur only at low DOM concentrations. Collectively, two general conclusions can be drawn from this review. First, lakes, rivers, and streams with urbanized watersheds are the most susceptible to increased concentrations of metals. Secondly, these results also suggest that regardless of high or low DOM in the water column, pH would affect metal concentrations in freshwater systems. Nonetheless, free metal ions would be higher in freshwater systems with acidic water and low DOM.     

Essential oils and their bioactive compounds as green preservatives against fungal and mycotoxin contamination of food commodities with special reference to their nanoencapsulation

Environmental Science and Pollution Research - Fungal and mycotoxin contamination of stored food items is of utmost concern throughout the world due to their hazardous effects on mammalian systems....     

Microbial diversity,community composition and metabolic potential in hydrocarbon contaminated oily sludge: prospects for in situ bioremediation

Microbial community composition and metabolic potential have been explored in petroleum-hydrocarbon-contaminated sludge of an oil storage facility. Culture-independent clone library-based 16S rRNA gene analyses revealed that the bacterial community within the sludge was dominated by the members of β-Proteobacteria (35 %), followed by Firmicutes (13 %), δ-Proteobacteria (11 %), Bacteroidetes (10 %), Acidobacteria (6 %), α-Proteobacteria (3 %), Lentisphaerae (2 %), Spirochaetes (2 %), and unclassified bacteria (5 %), whereas the archaeal community was composed of Thermoprotei (54 %), Methanocellales (33 %), Methanosarcinales/Methanosaeta (8 %) and Methanoculleus (1 %) members. Methyl coenzyme M reductase A (mcrA) gene (a functional biomarker) analyses also revealed predominance of hydrogenotrophic, methanogenic Archaea (Methanocellales, Methanobacteriales and Methanoculleus members) over acetoclastic methanogens (Methanosarcinales members). In order to explore the cultivable bacterial population, a total of 28 resident strains were identified and characterized in terms of their physiological and metabolic capabilities. Most of these could be taxonomically affiliated to the members of the genera Bacillus, Paenibacillus, Micrococcus, Brachybacterium, Aerococcus, and Zimmermannella, while two strains were identified as Pseudomonas and Pseudoxanthomonas. Metabolic profiling exhibited that majority of these isolates were capable of growing in presence of a variety of petroleum hydrocarbons as sole source of carbon, tolerating different heavy metals at higher concentrations (≥1 mM) and producing biosurfactant during growth. Many strains could grow under a wide range of pH, temperature, or salinity as well as under anaerobic conditions in the presence of different electron acceptors and donors in the growth medium. Correlation between the isolates and their metabolic properties was estimated by the unweighted pair group method with arithmetic mean (UPGMA) analysis. Overall observation indicated the presence of diverse groups of microorganisms including hydrocarbonoclastic, nitrate reducing, sulphate reducing, fermentative, syntrophic, methanogenic and methane-oxidizing bacteria and Archaea within the sludge community, which can be exploited for in situ bioremediation of the oily sludge.     

Applicability of sustainable urban drainage systems: an evaluation by multi-criteria analysis

Urban flooding has become more serious and worldwide in recent years, especially in the big cities of developing countries. This study uses a multi-criteria analysis (MCA) approach to evaluate the applicability of sustainable urban drainage systems (SUDS), a flood control measure, in the central part of Ho Chi Minh City, Vietnam. The output of the personal computer storm water management model along with interviews with 140 households was used to assess the efficacy and acceptability of four SUDS alternatives: rainwater harvesting, green roof, urban green space and pervious pavement. On technical performance, green roof was the best alternative, followed by pervious pavement, urban green space and rainwater harvesting. Results of the social survey, however, diverged largely from the results of the technical assessments. In particular, people generally prefer public SUDS such as urban green space and pervious pavements to household solutions. With respect to the MCA, we applied four different procedures: Borda count, pair-wise voting, range of value and analytic hierarchy process. Despite some differences, the integrated results from MCA largely agree that urban green space is the most favourable type of SUDS, followed by green roof, pervious pavement and rainwater harvesting.     

Effectiveness of urea in enhancing the extractability of 2,4,6-trinitrotoluene from chemically variant soils

One of the major challenges in developing an effective phytoremediation technology for 2,4,6-trinitrotoluene (TNT) contaminated soils is limited plant uptake resulting from low solubility of TNT. The effectiveness of urea as a solubilizing agent in increasing plant uptake of TNT in hydroponic systems has been documented. Our preliminary greenhouse experiments using urea were also very promising, but further characterization of the performance of urea in highly-complex soil-solution was necessary. The present study investigated the natural retention capacity of four chemically variant soils and optimized the factors influencing the effectiveness of urea in enhancing TNT solubility in the soil solutions. Results show that the extent of TNT sorption and desorption varies with the soil properties, and is mainly dependent on soil organic matter (SOM) content. Hysteretic desorption of TNT in all tested soils suggests irreversible sorption of TNT and indicates the need of using an extractant to increase the release of TNT in soil solutions. Urea significantly (p < 0.0001) enhanced TNT extraction from all soils, by increasing its solubility at the solid/liquid interface. Soil organic matter content and urea application rates showed significant effects, whereas pH did not exert any significant effect on urea catalysis of TNT extraction from soil. The optimum urea application rates (125 or 350 mg kg⁻¹) for maximizing TNT extraction were within the limits set by the agronomic fertilizer-N rates used for major agricultural crops. The data obtained from this batch study will facilitate the optimization of a chemically-catalyzed phytoremediation model for cleaning up TNT-contaminated soils.     

Effect of pH and Temperature on the Kinetics of Odor Oxidation Using Chlorine Dioxide

Abstract

Increasing public concerns over odors and air regulations in nonattainment zones necessitate the remediation of a wide range of volatile organic compounds (VOCs) generated in the poultry-rendering industry. Currently, wet scrubbers using oxidizing chemicals such as chlorine dioxide (ClO₂) are utilized to treat VOCs. However, little information is available on the kinetics of ClO₂ reaction with rendering air pollutants, limiting wet scrubber design and optimization. Kinetic analysis indicated that ClO₂ does not react with hexanal and 2-methylbutanal regardless of pH and temperature and implied that alde-hyde removal occurs primarily via mass transfer. Contrary to the aldehydes, ethanethiol or ethyl mercaptan (a model compound for methanethiol or methyl mercaptan) and dimethyl disulfide (DMDS) rapidly reacted with ClO₂. The overall reaction was found to be second and third order for ethanethiol and DMDS, respectively. Moreover, an increase in pH from 3.6 to 5.1 exponentially increased the reaction rate of ethanethiol (e.g., k ₂ = 25– 4200 L/mol/sec from pH 3.6 to 5.1) and significantly increased the reaction rate of DMDS if increased to pH 9 (k ₃ = 1.4 × 10⁶ L²/mol²/sec). Thus, a small increase in pH could significantly improve wet scrubber operations for removal of odor-causing compounds. However, an increase in pH did not improve aldehyde removal. The results explain why aldehyde removal efficiencies are much lower than methanethiol and DMDS in wet scrub-bers using ClO₂.     

Environmental factors affecting thyroid function of wild sea bass (Dicentrarchuslabrax) from European coasts

Thyroid functional status of wild fish in relation with the contamination of their environment deserves further investigation. We here applied a multi-level approach of thyroid function assessment in 87 wild sea bass collected near several estuaries: namely the Scheldt, the Seine, the Loire, the Charente and the Gironde. Thyroxine (T₄) and triiodothyronine (T₃) concentrations in muscle were analyzed by radioimmunoassay. The activity of hepatic enzymes involved in extrathyroidal pathways of thyroid hormone metabolism, viz. deiodination, glucuronidation and sulfatation were analyzed. Last, follicle diameter and epithelial cell heights were measured. We observed changes that are predicted to lead to an increased conversion of T₄-T₃ and lowered thyroid hormone excretion. The changes in the metabolic pathways of thyroid hormones can be interpreted as a pathway to maintain thyroid hormone homeostasis. From all compounds tested, the higher chlorinated PCBs seemed to be the most implicated in this perturbation.