Eldho Varghese

Degradation of metaflumizone in soil: Impact of varying moisture, light, temperature, atmospheric CO2 level, soil type and soil sterilization

Soil is a major sink for the bulk of globally used pesticides. Hence, fate of pesticides in soil under the influence of various biotic and abiotic factors becomes important for evaluation of stability and safety. This paper presents the impact of varying moisture, light, temperature, atmospheric CO(2) level, soil type and soil sterilization on degradation of metaflumizone, a newly registered insecticide in India. Degradation of metaflumizone in soil followed the first order reaction kinetics and its half life values varied from ~20 to 150 d. Under anaerobic condition, degradation of metaflumizone was faster (t(½) 33.4 d) compared to aerobic condition (t(½) 50.1 d) and dry soil (t(½) 150.4 d). Under different light exposures, degradation was the fastest under UV light (t(½) 27.3 d) followed by Xenon light (t(½) 43 d) and dark condition (t(½) 50.1 d). Degradation rate of metaflumizone increased with temperature and its half life values ranged from 30.1 to 100.3d. Elevated atmospheric CO(2) level increased the degradation in soil (t(½) 20.1-50.1 d). However, overall degradation rate was the fastest at 550 ppm atmospheric CO(2) level, followed by 750 ppm and ambient level (375 ppm). Degradation of metaflumizone was faster in Oxisol (pH 5.2, Total Organic Carbon 1.2%) compared to Inceptisol (pH 8.15, TOC 0.36%). In sterile soil, only 5% dissipation of initial concentration was observed after 90 d of sampling. Under various conditions, 4-cyanobenzoic acid (0.22-1.86 mg kg(-1)) and 4-trifluoromethoxy aniline (0.21-1.23 mg kg(-1)) were detected as major degradation products.

Degradation of kresoxim-methyl in soil: Impact of varying moisture, organic matter, soil sterilization, soil type, light and atmospheric CO2 level

In the present investigation, persistence of kresoxim-methyl (a broad spectrum strobilurin fungicide) was studied in two different soil types of India namely Inceptisol and Ultisol. Results revealed that kresoxim-methyl readily form acid metabolite in soil. Therefore, residues of kresoxim-methyl were quantified on the basis of parent molecule alone and sum total of kresoxim-methyl and its acid metabolite. Among the two soil types, kresoxim-methyl and total residues dissipated at a faster rate in Inceptisol (T1/2 0.9 and 33.8d) than in Ultisol (T1/2 1.5 and 43.6d). Faster dissipation of kresoxim-methyl and total residues was observed in submerged soil conditions (T1/2 0.5 and 5.2d) followed by field capacity (T1/2 0.9 and 33.8d) and air dry (T1/2 2.3 and 51.0d) conditions. Residues also dissipated faster in 5% sludge amended soil (T1/2 0.7 and 21.1d) and on Xenon-light exposure (T1/2 0.5 and 8.0d). Total residues of kresoxim-methyl dissipated at a faster rate under elevated CO2 condition (∼550μLL(-)(1)) than ambient condition (∼385μLL(-)(1)). The study suggests that kresoxim-methyl alone has low persistence in soil. Because of the slow dissipation of acid metabolite, the total residues (kresoxim-methyl+acid metabolite) persist for a longer period in soil. Statistical analysis using SAS 9.3 software and Duncans Multiple Range Test (DMRT) revealed the significant effect of moisture regime, organic matter, microbial population, soil type, light exposure and atmospheric CO2 level on the dissipation of kresoxim-methyl from soil (at 95% confidence level p<0.0001).

Simultaneous removal of multiple pesticides from water: Effect of organically modified clays as coagulant aid and adsorbent in coagulation–flocculation process

Contamination of drinking water sources with agrochemical residues became a major concern in the twenty-first century. Coagulation–flocculation is the most widely used water-treatment process, but the efficiency to remove pesticides and other organic pollutants are limited compared to adsorption process. Thus, simultaneous action of adsorption on normal bentonite or organo-modified montmorillonite clays [modified with octadecylamine (ODA-M) and octadecylamine + aminopropyltriethoxysilane (ODAAPS-M)] followed by coagulation–flocculation by alum and poly aluminium chloride has been evaluated for removal of 10 different pesticides, namely atrazine, lindane, metribuzin, aldrin, chlorpyriphos, pendimethalin, α-endosulphan, β-endosulphan, p, p′-DDT, cypermethrin and two of its metabolites, endosulphan sulphate and p, p′-DDE, from water. The coagulation without integration of adsorption was less effective (removal % varies from 12 to 49) than the adsorption–coagulation integrated system (removal % varies from 71 to 100). Further, coagulation integrated with adsorption was more effective when organically modified montmorillonite was used as adsorbent compared to normal bentonite. The removal efficiency of organic clay depends upon the concentration of pesticides, doses of clay minerals, and efficiency was more for ODAAPS-M as compared to ODA-M. The combination of ODAAPS-M-clay with coagulants was also used efficiently for the removal of pesticides from natural and fortified natural water collected and the results exhibit the usefulness of this remediation technique for application in water decontamination and in treatment of industrial and agricultural waste waters.

Exploitation of Nano-Bentonite, Nano-Halloysite and Organically Modified Nano-Montmorillonite as an Adsorbent and Coagulation Aid for the Removal of Multi-Pesticides from Water: A Sorption Modelling Approach

The objective of this study was to investigate the removal of multi-pesticides through a combined treatment process with coagulation–adsorption on nano-clay. Nano-clays like nano-bentonite, nano-halloysite and organically modified nano-montmorillonite were used as the adsorbent, and alum and polyaluminium chloride (PAC) were used as the coagulants. The coagulation method alone was not sufficient to purify water, whereas coagulation plus adsorption methods provided superior purification. Amongst the nano-clays used, organically modified nano-montmorillonite gave the best result in terms of pesticide removal from water. In order to evaluate the effect of coagulant addition on the removal efficiency of nano-clay, the respective adsorption isotherms were also calculated in the presence and absence of coagulants. Freundlich isotherm constants have shown that adsorption of pesticides on different nano-clay depends on the type of clay, presence and absence of coagulants as well as the properties of pesticides. The treatment combination having the maximum removal capacity was used efficiently for the removal of pesticides from natural and fortified natural water. The results indicated that alum–PAC coagulation aided by nano-clay as an adsorbent was the superior process for the simultaneous removal of multi-pesticides from water.

Removal of Poly Aromatic Hydrocarbons (PAHs) from Water: Effect of Nano and Modified Nano-clays as a Flocculation Aid and Adsorbent in Coagulation-flocculation Process

Water treatment process involving simultaneous action of adsorption on different nano and organo-modified nano-clays followed by coagulation-flocculation by alum and poly aluminium chloride (PAC) has been evaluated for the removal of PAHs (naphthalene, acenaphthalene, phenanthrene, fluoranthene, anthracene, and pyrene) from water. When clay minerals along with alum and PAC were used for treatment, 37.4–100.0% removal of PAHs was observed compared to 20–38% removal using normal water treatment process with either alum or alum + PAC. The effectiveness of clay minerals for removal of PAHs followed the order (P < 0.05): halloysitenano-clay (HN-clay) < normal bentonite (NB-clay) < hydrophilic nano-bentonite (HNB-clay) < nano-montmorillonite modified with dimethyl dialkyl amine (DMDA-M-clay) ≈ nano-montmorillonite modified with octadecylamine and aminopropyltriethoxysilane (ODAAPS-M-clay) ≈ nano-montmorillonite modified with octadecylamine (ODA-M-clay) in combination with alum + PAC. The modified treatment process (alum + PAC + clay minerals), where water was initially treated with clays followed by normal process of coagulation (alum + PAC), was found to be the most effective method with maximum removal for ODAAPS-M-clay (97.7–100.0%) which is at par wih ODA-M (97.0–100.0%), and DMDA-M-clay (94.8–100%). The removal of PAHs varied in the order: naphthalene ≈ acenaphthalene > anthracene ≈ pyrene > phenanthrene > fluoranthrene. The treatment combination having the maximum removal capacity was also used eficiently for the removal of PAHs from natural and fortified natural water. This article demonstrated adsorption-coagulation integrated system has the potential to remediate PAHs polluted water.

Identification of Differentially Expressed Genes in RNA-seq Data of Arabidopsis thaliana: A Compound Distribution Approach

Abstract Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product, which may be proteins. A gene is declared differentially expressed if an observed difference or change in read counts or expression levels between two experimental conditions is statistically significant. To identify differentially expressed genes between two conditions, it is important to find statistical distributional property of the data to approximate the nature of differential genes. In the present study, the focus is mainly to investigate the differential gene expression analysis for sequence data based on compound distribution model. This approach was applied in RNA-seq count data of Arabidopsis thaliana and it has been found that compound Poisson distribution is more appropriate to capture the variability as compared with Poisson distribution. Thus, fitting of appropriate distribution to gene expression data provides statistically sound cutoff values for identifying differentially expressed genes.

Neighbor-Balanced Row-column Designs

In this article, row-column designs incorporating directional neighbor effects have been studied. A row-column design is said to be neighbor balanced if every treatment has all other treatments appearing as a neighbor a constant number of times. We considered here three different situations under row-column setup incorporating neighbor effects viz., row-column design with one-sided neighbor effect, two-sided neighbor effect, and four-sided neighbor effect. The information matrices for all the situations for estimating the direct and neighbor effects of treatments have been derived. Methods of constructing neighbor-balanced row-column designs have been developed and its characterization properties have been studied.

Selection indices to identify maize (Zea mays L.) hybrids adapted under drought-stress and drought-free conditions in a tropical climate

Abstract. Drought stress is the most important production constraint in maize (Zea mays L.), especially in rainfed agriculture. To improve productivity of rainfed maize, the development of hybrids with tolerance to drought stress is an important objective in maize breeding programs. The present study was undertaken to identify maize hybrids that perform better under drought-stress and drought-free conditions by using various selection indices. These selection indices were calculated on the basis of yield (t ha–1) performance of hybrids measured under drought stress and optimum environments. A set of 38 cultivars was evaluated at 10 environments (representing five each of drought stress and optimum growing conditions). The average reduction in grain yield due to drought stress was 52%. Effects of genotype, environment and their interaction were significant sources of variation in determining grain yield, respectively explaining 5.0–7.4%, 55.0–60.2% and 12.0–15.0% of total variation in yield under drought-stress and drought-free conditions. Of eight selection indices considered for study, three indices such as harmonic mean, geometric mean, and stress tolerance index were identified as suitable for selection of genotypes capable of performing well both under drought-stress and drought-free environments. Drought response index and drought resistance index were found useful in identifying hybrids that performed better under drought stress. Stress susceptibility index was negatively correlated with yield measured under drought stress. Stress susceptibility index could be used as selection index but only in combination with yield performance data under water-deficit conditions in order to identify drought-tolerant hybrids with reasonable productivity. Test weight, shelling percentage, days to maturity, and ear girth were found to be useful traits for improving yield performance across diverse environments. Cultivation of identified drought-tolerant hybrids would be useful to enhance maize productivity in drought-stress environments.

Web generation of experimental designs balanced for indirect effects of treatments (WEB-DBIE)

Online software to generate designs balanced for indirect effects of treatments.It consists of randomized layout of Neighbour Balanced and Crossover Designs.Online catalogue of designs within a permissible range of parameters is provided.This software (WEB-DBIE) is deployed at www.iasri.res.in/webdbie.It is freely available for the researchers and students working in this area. Indirect effects are effects that occur in an experiment due to the units which are adjacent (spatially or temporally) to the unit being observed. Spatial indirect effects arise due to the treatments applied to the adjacent neighbouring units/plots and the designs so developed are called Neighbour Balanced Designs (NBDs). Whereas temporal indirect effects occur because of the carryover or residual effects in the periods following the periods of their direct application and the designs considering temporal effects are called Crossover Designs. A large number of such designs have been developed in the literature. For ready referencing and potential use of these designs, online software for generation of randomized layout of these designs is highly desirable. This paper describes the development of a web solution for generation of NBDs and Crossover Designs using client-server architecture along with an online catalogue of the designs within a permissible range. Designs generated through this software have wide applications in agricultural experiments, forestry and agro-forestry trials, polycross nurseries, serological experiments, animal nutritional trials, sensory evaluations, clinical trials, etc. WEB-DBIE is accessible any time from arbitrary platforms through internet. This software provides freely available solution for the researchers and students working in this area.

Universally optimal second order neighbour designs

This paper deals with optimality aspects of complete block designs with interference effects arising from the neighbouring units up to distance 2 (first and second order) from one side. Conditions have been obtained for the block design to be universally optimal for estimating direct and interference effects. Some classes of balanced and strongly balanced complete block designs have been identified to be universally optimal for the estimation of direct effects, first order neighbour effects and second order neighbour effects.