Mutagenicity evaluation of industrial sludge from common effluent treatment plant

Sludge from common effluent treatment plant (CETP) receiving effluents from textile industries at Mandia Road, Pali, was analyzed to assess the level of mutagenicity. Mutagenicity assay using Salmonella typhimurium tester strains TA 98 and TA 100 gave positive results, thus suggesting presence of genotoxic contaminants in the samples investigated. Further, mutagenic activity of chemical sludge was found to be lesser than that of biological sludge. This result is very surprising and unexpected as it is indicating that some mutagenic compounds are either being formed or certain promutagenic compounds are being converted into stable mutagenic metabolites during the biological treatment of the wastewater effluents. There have been no previous reports giving similar or contrary results. Most of the previous studies have reported effects of single combined sludge.     

Bioconcentration and Phytotoxicity of Cd in Eichhornia crassipes

Plants of Eichhornia crassipes grown at various levels of cadmium ranging from 0.1 to 100 μg ml⁻¹ accumulated Cd in a concentration and duration dependent manner. At all levels, Cd accumulation by various plant tissues followed the order roots shoot leaves. Approximately 80% of total Cd was accumulated by plant at highest concentration (100 μg ml⁻¹) used in the experiment. Cadmium induced phytotoxicity appears at 25.0 μg ml⁻¹ resulting into reduced levels of chlorophyll, protein and in vivo nitrate reductase activity of the plant. However, a slight induction of these physiological variables was obtained at lowest Cd (0.1 μg ml⁻¹) concentration. In contrast, carotenoid content increased at highest Cd concentration i.e., 100 μg ml⁻¹. Similar effects at low and high levels of Cd was obtained with respect to mitotic index and micronuclei in root meristem of the plant. It could be inferred that Cd toxicity in plant is differential depending upon the low and high concentration of Cd in the medium.     

Toxic metals and organochlorine pesticides residue in single herbal drugs used in important ayurvedic formulation – ‘Dashmoola’

Herbal formulations are getting popularity throughout the world and commercialized extensively for various medicinal properties. WHO has emphasized the need for quality assurance of herbal products, including testing of heavy metals and pesticides residues. 'Dashmoola', a popular herbal formulation, with immunomodulator and febrifugal properties, consists of ten single root drugs. In view of WHO guidelines, single herbal drugs used in 'Dashmoola', were collected from different places of India for testing heavy metals and persistent pesticides residue. Although use of roots in 'Dashmoola' is prescribed in original ayurvedic literature but now many pharmacies use stem in place of roots. Therefore, in the present study both roots and stems were selected for estimation of six heavy metals namely arsenic (As), mercury (Hg), lead (Pb), cadmium (Cd), chromium (Cr) and nickel (Ni). Apart from these, the organochlorine pesticides residue viz. different metabolites of DDT, DDE, isomers of HCH and alpha-endosulfan were checked in total 40 samples of single crude drugs. Heavy metals except Hg, were present in most of the samples. In few samples Pb and Cd concentration were beyond the WHO permissible limits. Although alpha-HCH and gamma-HCH were present in almost all the samples, but other pesticides were not detected in these samples. DDT and DDE were found only in two samples.     

Metal concentrations in water, sediment, and fish from sewage-fed aquaculture ponds of Kolkata, India

The concentrations of lead, cadmium, chromium, copper, and zinc were investigated in the sewage-fed pond water, sediment, and the various organs of Labeo rohita, Catla catla, Cirrhinus mrigala, Oreochromis mossambicus, and Cyprinus carpio cultured in sewage-fed ponds, Kolkata, India. Among the metals, cadmium, lead, and zinc were detected in water and, except lead, were below the water quality guideline levels for the protection of freshwater aquatic life proposed by CEQG (Canadian Environmental Quality Guidelines) and AENV (Alberta Environment). Therefore, lead could pose danger to aquatic organisms. All the five metals were detected in the sediment and, except cadmium and lead, were below the sediment quality guideline levels for aquatic life proposed by EPA (Environmental Protection Agency). Therefore, these two metals could be toxic to aquatic organisms. Significant (P > 0.05) differences were observed among the five fish species for all these metals accumulation. Also, significant (P > 0.05) differences were noticed among these metals accumulation in fish organs. Cadmium showed the least bioaccumulation, while zinc showed the highest bioaccumulation in all the fish species. Though the metal concentration in the different fish tissues was variable, the highest concentration was found in kidney and the lowest in the muscle. Concentrations of these metals in the muscle tissue of all the fish species were well below the consumption safety tolerance in fish set by WHO/FAO, and thus, so far as these metals are concerned, these sewage-fed cultured fishes are safe and suitable for human consumption.     

Effect of ultrasonic pretreatment on secondary sludge and anaerobic biomass to enhance biogas production

Journal of Material Cycles and Waste Management - Anaerobic digestion studies were carried out with tannery excess secondary sludge obtained from common effluent treatment plant. The excess sludge...     

Arsenic tolerances in rice (Oryza sativa) have a predominant role in transcriptional regulation of a set of genes including sulphur assimilation pathway and antioxidant system

World wide arsenic (As) contamination of rice has raised much concern as it is the staple crop for millions. Four most commonly cultivated rice cultivars, Triguna, IR-36, PNR-519 and IET-4786, of the West Bengal region were taken for a hydroponic study to examine the effect of arsenate (As^V) and arsenite (As^III) on growth response, expression of genes and antioxidants vis-à-vis As accumulation. The rice genotypes responded differentially under As^V and As^III stress in terms of gene expression and antioxidant defences. Some of the transporters were up-regulated in all rice cultivars at lower doses of As species, except IET-4786. Phytochelatin synthase, GST and γ-ECS showed considerable variation in their expression pattern in all genotypes, however in IET-4786 they were generally down-regulated in higher As^III stress. Similarly, most of antioxidants such as superoxide dismutase (SOD), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), catalase (CAT), monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR) increased significantly in Triguna, IR-36 and PNR-519 and decreased in IET-4786. Our study suggests that Triguna, IR-36 and PNR-519 are tolerant rice cultivars accumulating higher arsenic; however IET-4786 is susceptible to As-stress and accumulates less arsenic than other cultivars.     

Poor efficacy of herbicides in biochar-amended soils as affected by their chemistry and mode of action

We evaluated wheat straw biochar produced at 450 °C for its ability to influence bioavailability and persistence of two commonly used herbicides (atrazine and trifluralin) with different modes of action (photosynthesis versus root tip mitosis inhibitors) in two contrasting soils. The biochar was added to soils at 0%, 0.5% and 1.0% (w/w) and the herbicides were applied to those soil-biochar mixes at nil, half, full, two times, and four times, the recommended dosage (H₄). Annual ryegrass (Lolium rigidum) was grown in biochar amended soils for 1 month. Biochar had a positive impact on ryegrass survival rate and above-ground biomass at most of the application rates, and particularly at H₄. Within any given biochar treatment, increasing herbicide application decreased the survival rate and fresh weight of above-ground biomass. Biomass production across the biochar treatment gradient significantly differed (p < 0.01) and was more pronounced in the case of atrazine than trifluralin. For example, the dose-response analysis showed that in the presence of 1% biochar in soil, the value of GR₅₀ (i.e. the dose required to reduce weed biomass by 50%) for atrazine increased by 3.5 times, whereas it increased only by a factor of 1.6 in the case of trifluralin. The combination of the chemical properties and the mode of action governed the extent of biochar-induced reduction in bioavailability of herbicides. The greater biomass of ryegrass in the soil containing the highest biochar (despite having the highest herbicide residues) demonstrates decreased bioavailability of the chemicals caused by the wheat straw biochar. This work clearly demonstrates decreased efficacy of herbicides in biochar amended soils. The role played by herbicide chemistry and mode of action will have major implications in choosing the appropriate application rates for biochar amended soils.     

Abiotic degradation (photodegradation and hydrolysis) of imidazolinone herbicides

The abiotic degradation of the imidazolinone herbicides imazapyr, imazethapyr and imazaquin was investigated under controlled conditions. Hydrolysis, where it occurred, and photodegradation both followed first-order kinetics for all herbicides. There was no hydrolysis of any of the herbicides in buffer solutions at pH 3 or pH 7; however, slow hydrolysis occurred at pH 9. Estimated half-lives for the three herbicides in solution in the dark were 6.5, 9.2 and 9.6 months for imazaquin, imazethapyr and imazapyr, respectively. Degradation of the herbicides in the light was considerably more rapid than in the dark with half lives for the three herbicides of 1.8, 9.8 and 9.1 days for imazaquin, imazethapyr and imazapyr, respectively. The presence of humic acids in the solution reduced the rate of photodegradation for all three herbicides, with higher concentrations of humic acids generally having greater effect. Photodegradation of imazethapyr was the least sensitive to humic acids. The enantioselectivity of photodegradation was investigated using imazaquin, with photodegradation occurring at the same rate for both enantiomers. Abiotic degradation of imidazolinone herbicides on the soil surface only occurred in the presence of light. The rate of degradation for all herbicides was slower than in solution, with half-lives of 15.3, 24.6 and 30.9 days for imazaquin, imazethapyr and imazapyr, respectively. Abiotic degradation of these herbicides is likely to be slow in the environment and is only likely to occur in clear water or on the soil surface.     

Sorption–desorption of indaziflam and its three metabolites in sandy soils

Indaziflam is a relatively new herbicide for which sorption–desorption information is lacking, and nothing is available on its metabolites. Information is needed on the multiple soil and pesticide characteristics known to influence these processes. For four soils, the order of sorption was indaziflam (N-[1R,2S)-2,3-dihydro-2,6-dimethyl-1H-inden-1-yl]-6-[(1R)-1-fluoroethyl]-1,3,5-triazine-2,4-diamine) (sandy clay loam: K_f = 5.9, 1/n_f = 0.7, K_foc = 447; sandy loam: K_f = 3.9, 1/n_f = 0.9, K_foc = 276) > triazine indanone metabolite (N-[(1R,2S)-2,3-dihydro-2,6-dimethyl-3-oxo-1H-inden-1-yl]-6-[(1R)-1-fluoroethyl]-1,3,5-triazine-2,4-diamine) (sandy clay loam: K_f = 2.1, 1/n_f = 0.8, K_foc = 177; sandy loam: K_f = 1.7, 1/n_f = 0.9, K_foc = 118) > fluoroethyldiaminotriazine metabolite (6-[(1R-1-Fluoroethyl]-1,3,5-triazine-2,4-diamine) (sandy clay loam: K_f = 0.3, 1/n_f = 0.9, K_foc = 28; sandy loam: K_f = 0.3, 1/n_f = 0.9, K_foc = 22) = indaziflam carboxylic acid metabolite (2S,3R)-3-[[4-amino-6-[(1R)-1-fluoroethyl]-1,3,5-triazin-2-yl]amino]-2,3-dihydro-2-methyl-1H-indene-5-carboxylic acid) (sandy clay loam: K_f = 0.3, 1/n_f = 0.9, K_foc = 22; sandy loam: K_f = 0.5, 1/n_f = 0.8, K_foc = 32). The metabolites being more polar than the parent compound showed lower sorption. Desorption was hysteretic for indaziflam and triazine indanone metabolite, but not for the other two metabolites. Unsaturated transient flow K_d's were lower than batch K_d's for indaziflam, but similar for fluoroethyldiaminotriazine metabolite. Batch K_d's would overpredict potential offsite transport if desorption hysteresis is not taken into account.