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Extensive consumption, toxicity, and bioaccumulation of malathion (MLT) and lindane (γ-HCH) pesticides collectively attract the world’s attention. Herein, the nanocomposite of chitosan wrapped NiO@ZnO was synthesized by a green methodology using Azadirachta indica leaves extract. Structural and morphological analysis of chitosan-NiO@ZnO showed hollow sphere-flake shaped image adsorbed on a solid chitosan surface with a large surface area of 73 m2g-1. A decrease in values of lattice strain, dislocation density and crystallite size described the imperfection in crystal geometry and new peaks in FT-IR spectra at 698 cm-1 and 448 cm-1 of Ni-N and Zn-N, respectively confirms the coupling. The chitosan- NiO@ZnO nanocomposite with a reduced band gap due to the generation of new energy levels in the vicinity of of conduction and valence band. Chitosan-NiO@ZnO and individuals nanoparticles (NiO and ZnO) were well-characterized and utilized for degradation MLT and γ- HCH under direct sunlight and dark conditions. The highest degradation of pesticides (above 94%) resulted with 2 mg L-1 and 10 mg L-1 of MLT (π_π) and γ- HCH, respectively with a 20 mg catalyst dose, and pH of ~7 under daylight exposure (5 h). Chitosan-NiO@ZnO substantially suppressed the half-life of the targeted pesticides (MLT: 0.48 h; HCH 0.51 h) and demonstrated the first- order kinetics with a high adsorption capacity, Xm (MLT: 14.5 mg g-1 and γ- HCH 20.7 mg g-1), which also confirmed the strong binding with the pesticides, followed by their conversion into safer and smaller metabolites. The charge separation mechanism was elucidated by UV reflectance and photoluminescence data. Hydroxyl radicals were most frequently responsible for the degradation of pesticides as confirmed by scavenger analysis. The synthesized green-nano photocatalyst showed high reusability (up to 10th cycles), sensitivity, and stability within the degradation process, presumably making it suitable for industrial applications.

Large use of flame retardants or additives in plastic industries have caused scientific attention as their leaching from consumer products is indicative of environmental concern. Moreover, plastic additives have proven features of endocrine disruptors, genotoxicity and persistence. Therefore, photodegradation of tetrabromobisphenol A (TBBPA) and bisphenol A (BPA) were explored in water. Seeing environmental safety, titanium dioxide decorated magnesium substituted cadmium ferrite (CdMgFe

Dyes and phenols are extensively used chemicals in petrochemicals, pharmaceuticals, textile, and paints industries. Due to high persistence, bioaccumulation, and toxicity, their removal from the environment is highly imperative by advanced techniques. Single metal oxide nanomaterials are generally associated with limitations of large bandgap (> 3eV) and charge recombination. Therefore, heterometallic oxides (HMOs) as CuFe2O4, CuMn2O4, and MnZn2O4 have been synthesized via green route by employing leaf extract of Azadirachta indica. XRD revealed the crystalline nature of HMOs nanospheres with particle size less than 100 nm. Subsequently, HMOs nanocatalysts were used as photocatalyst for removal of 3-amino phenols (3-AP) and eriochrome black T (EBT) from water under sunlight. Reaction parameters namely pollutant concentration (50–130 mgL-1), catalyst dose (20–100 mg), and pH (3–11) were optimized in order to get best results. Substantial degradation (80–95%) of pollutants (50 mgL-1) by HMOs (80 mg) was achieved at neutral pH under sunlight exposure. Highest removal by CuFe2O4 might be due to its high surface area (35.7 m2g-1), low band gap (2.4 eV), larger particle stability (Zeta potential: -22.0 mV), and lower photoluminescence intensity. Sharp declines in curves were visually confirmed by color change and indicated for first-order kinetics of degradation with initial Langmuir adsorption. Spectrophotometric analysis revealed that half-life (t1/2) of 3-AP (0.9-1.7 h) and EBT (0.6-0.8 h) were significantly reduced. Faster degradation of EBT than 3-AP was because of less electronegative N-atom at the diazo group. Scavenger analysis indicated the presence of active radicals in photo-catalytic degradation of 3-AP and EBT. All HMOs have shown high reusability (n=8) which ensures their stability, sustainability, and efficiency. Overall, green synthesized HMOs nanoparticles with prominent surface characteristics offer a viable alternative photocatalyst for industrial applications.

The wide-ranging uses of pesticides in agriculture practices are forming various scums in aquatic life. In developing countries, the continued use of banned pesticides is the reason for their high persistence in the environment. The major reason for the restriction of various pesticides in some parts of the world is the greater half-lives of organochlorines. Because of high toxicity coupled with persistence and bioaccumulation, the removal of such contaminants from the environment is imperative. Several techniques such as the use of microbial methods, commercial adsorbents (activated carbon, agricultural, and natural waste) were employed for the effective removal of pesticides. Nowadays, high surface-active nanomaterials including nanocomposite and nanobiocomposite techniques have been reported as highly effective in the removal of pesticides. Distinct organic, biotic, and physical characteristics of silver (decent metal) make it relevant for utilization in different areas of numerous industries. Their reusability, cost effectiveness, and environmentally friendly nature of silver-based nanomaterials (polymeric film, alumina, stimulated carbon) make them more noteworthy. The shape and size distribution of silver nanoparticles changes in various properties such as optical, catalytic, and electromagnetic properties by synthetic approaches, variable stabilizers, and reducing agents. This chapter provides an inclusive report synthesis of several Ag-based (supported or modified) nanomaterials for the degradation of pesticides. Different techniques used to remove pesticides are summarized as photochemical, redox, adsorption, and reactive degradation with silver nanoparticles. Moreover, the significance of green-fabricated silver nanoparticles is also discussed.

Release of colouring agents into the environment alarms the need to design a cheap, quick and safe process. Owing to environmental safety concern, synthesis of two metal hexacyanoferrates (MHCFs) based on cadmium (CdHCF) and manganese (MnHCF) was carried out using natural plant extract of Azadirachta indica and water as a solvent. Synthesized MHCFs were utilized for the removal of an acid dye (fuchsin acid, FA) and a xanthenes dye (rhodamine B, RB). The reactions were optimized at various conditions of dye concentration, catalyst dose, reaction pH, time and source of light. The MHCFs showed excellent results with both the dyes within very limited span of time (2 h). Consequently, 98% of FA and 97% of RB were degraded with 10 mg of CdHCF, at neutral pH and under sunlight. The degradation process followed the first-order reaction kinetics having t1/2 around 0.3 min. The MHCFs exhibited difference of only little percentage in degradation owing to a very slight difference between their surface areas (CdHCF: 54.1 m2 g−1; MnHCF: 49.7 m2 g−1). The synthesised nanocatalysts were stable as indicated by their higher negative zeta potential values. The adsorption of dyes was found to be maximum with CdHCF having Xm value 19.69 mg g−1 and 18.15 mg g−1 for FA and RB, respectively. Photocatalytic degradation involved the main role of hydroxyl radical as indicated by decline in activity of nanocatalyst in the presence of scavengers. All in all, this study presents highly active nanomaterials with higher surface area, stability and semiconducting properties under natural conditions.

Chrysene is a high molecular weight polycyclic aromatic hydrocarbon and priority pollutant due to its persistent nature and toxicity. Ecological concern of this emerging contaminant calls for low-cost and efficient removal practices. Recently, doped or coupled nanomaterials with advanced characteristics are fascinating. Therefore, we have synthesized crystalline nanocubes (∼100 nm) of Fe2O3@ZnHCF nanocomposite using plant extract of Azadirachta indica and subsequently used it for degradation of chrysene. Under sunlight, a rapid initial exponential decrease in concentration of chrysene over time revealed high photo-activity of doped Fe2O3@ZnHCF because of remarkably improved surface area (343.436 m2 g−1) and band gap energy (2.18 eV). At optimum catalyst dose (25 mg) and neutral pH photodegradation of chrysene (2 mg L−1) up to 92% followed first order kinetics and Langmuir isotherms. Comparing with constituents, doped nanocubes (Xm = 45.45 mg g−1) were more effective for degradation as revealed by three to six times greater adsorption of chrysene than ZnHCF (Xm = 16.22 mg g−1) and Fe2O3 (Xm = 7.348 mg g−1). Moreover, it reduced the t1/2 value of chrysene (0.54 h) manifolds than that of Fe2O3 (t1/2 = 23.41 h) and ZnHCF (t1/2 = 8.66 h) nanoparticles. GC–MS results revealed the presence of smaller and safer by-products like malealdehyde, propionic acid and but-2-ene-1,2,4-triol that are formed by oxidation of chrysene by OH radical. Catalysts were also found reusable for ten cycles without significant loss in activity. Overall, Fe2O3@ZnHCF nanocubes might be believed to be a promising photocatalyst for environmental protection by virtue of greater active sites, high surface activity, low band gap with charge separation and semiconducting nature.

The low-cost and highly efficient pesticides are largely used in residential, agricultural, and commercial applications. Their prevalent occurrence, bioaccumulation, and chronic toxicity to living beings have raised environmental concern and call for their whole eradication, especially from water. By virtue of semiconducting nature and high surface area, nanomaterials have become efficient adsorbent and photocatalyst in removal of toxins. To confirm this, the potential of highly crystalline metal hexacyanoferrates (MHCFs) of Zn, Cu, Co, and Ni was evaluated in deprivation of selected hazardous pesticides, viz., chlorpyrifos (CP), thiamethoxam (TH), and tebuconazole (TEB). Sharp nanocubes of ZnHCF (~ 100 nm), distorted nanocubes of CuHCF (~ 100 nm), and nanospheres of CoHCF and NiHCF (

Expanded polystyrene (EPS) is a major component of marine debris globally. Recently, hazardous hexabromocyclododecanes (HBCDDs) were detected in EPS buoys used for aquaculture farming. Subsequently, enrichment of HBCDDs was found in nearby marine sediments and mussels growing on EPS buoys. It was suspected that EPS buoys and their debris might be sources of HBCDDs. To confirm this, the release of HBCDDs from EPS spherules detached from a buoy to seawater was investigated under field (open sea surface and closed outdoor chambers with sun exposure and in the dark) and laboratory (particle-size) conditions. In all exposure groups, initial rapid leaching of HBCDDs was followed by slow desorption over time. Abundant release of HBCDDs was observed from EPS spherules exposed to the open sea surface (natural) and on exposure to sunlight irradiation or in the dark in controlled saline water. Water leaching and UV-light/temperature along with possibly biodegradation were responsible for about 37% and 12% of HBCDDs flux, respectively. Crumbled EPS particles (≤1 mm) in samples deployed on the sea surface for 6 months showed a high degree of weathering. This implies that surface erosion and further fragmentation of EPS via environmental weathering could enhance the leaching of HBCDDs from the surface of EPS. Overall, in the marine environment, HBCDDs could be released to a great extent from EPS products and their debris due to the cumulative effects of the movement of large volumes of water (dilution), biodegradation, UV-light/temperature, wave action (shaking), salinity and further fragmentation of EPS spherules.

Rapid industrialization and extensive use of pesticides in agriculture practices have contributed to the leaking of pesticide residues into water. Among them, organochlorines are highly toxic with half-lives of many years followed by organophosphates (OPs). Being banned in many countries, most of the pesticides are still persisting in the environment. Due to high perseverance, toxicity and potential to bioaccumulation, their removal is imperative. In this direction, conventional adsorbents such as commercial activated carbon, agricultural and natural waste were highly employed. In modern era, nanomaterials (including nanocomposites and nanobiocomposite) with high surface area come out as most economic, rapid and effective catalyst. TiO2 (photocatalyst) and Fe0 by itself or with oxidizing agents are playing a promising role in elimination of pesticide pollution and open the opportunities for exploring other nanoparticles as well. Further, their modified, doped or composites form showed enhanced characteristics due to introduction of new energy levels or increase in surface area. In contrast to TiO2 and Fe0, various nanostructured metal oxides found to degrade OP pesticides by rapid reactive adsorption followed by cleavage of P–O bond via SN2 mechanism. The present review focuses on the present status of pesticide removal using nanoparticles through adsorption together with photocatalytic or redox or reactive degradation. Herein, detailed information on several pesticides, problems related to pesticide, their metabolites, environmental concentration and need for degradation has been presented. In addition, importance of green synthesized nanoparticles along with limitation and potential health risk of nanomaterials in degradation of various organic pollutants has been highlighted.

There is about 700,000 tonnes of dyes, of more than 10,000 types, that are used as coloring agents in industries, mainly for textile. The release of dyes in natural media is of concern due to their high persistence, toxicity and potential to the bioaccumulate in living organisms. In particular, the most commercialized and carcinogenic azo dyes, that pocess a benzidine function, needs urgent attention. Here, we review the current status of cationic and anionic dyes. We present dye removal techniques using nanoparticles through adsorption and degradation. Among dye removal techniques, adsorption was found the most efficient and cheap. For that, conventional adsorbents such as commercial activated carbon, chitosan and natural waste are often employed. We discuss the use of ZnO, TiO2 and Fe0 to remove dye pollution.

This study reports the distribution of Cr, Ni, Cu and Pb in waters, sediments, macrophytes and fish of the Yamuna River’s patch in Delhi (India). This is one of the most polluted stretches of rivers in the world. Water from this river is used fosr irrigation, industrial and domestic purposes, including drinking water. The effects of season and anthropogenic practices were identified. Almost zero dissolved oxygen and high levels of lead and phosphate indicate the polluted state of the aquatic system. The enrichment factors in sediments (with respect to reference site) vary in the range of 0.60–82.9% (Cr), 1.40–90.5% (Ni), 1.00–85.3% (Cu) and 3.80–86.6% (Pb). The toxic effects due to Ni and Pb could frequently be visible in aquatic life as their values fall above the probable effect level (36 mg Kg−1 for Ni and 91.3 mg Kg−1 for Pb). The metal contents in the macrophyte (Eichhornia crassipes) and the fish (Oreochromis niloticus) generally increase in the summer season. Cu and Pb accumulate preferenti...

Aromatic substituted phenols and their by-products discharged from numerous industries are of environmental concern due to their toxic, carcinogenic, recalcitrant, and bioaccumulating properties. Therefore, their complete removal from waters by low-cost, efficient, environmentally friendly nanomaterial-based treatment techniques is desirable. Double metal cyanide complexes (DMCC) are the extremely useful heterogeneous and recoverable catalyst. Hence, green route has been developed for several DMCC and their photocatalytic efficiency was evaluated for degradation of toxic phenols. Herein, nanocubes for hexacyanocobaltate of iron (FeHCC ~ 200 nm), nickel (NiHCC 94% FeHCC > 93% NiHCC) > phenol (94% ZnHCC > 92% FeHCC > 91% NiHCC) > 2,4-DNP (92% ZnHCC > 91% FeHCC > 90% NiHCC). This is attributed to highest basicity of 3-aminophenol containing excess of free electrons. Highest catalytic potential of ZnHCC (Xm = 0.54–0.43 mg/g) is because of its highest surface area and negative zeta potential along with sharp morphology and crystallinity. Adsorption of phenols over catalyst was statistically significant with Langmuir isotherms (R2 ≥ 0.96; p value ≤ 0.05). Small and non-toxic by-products like oxalic acid, benzoquinone, (Z)-hex-3-enedioic acid, (Z)-but-2-enal, and (Z)-4-oxobut-2-enoic acid were identified in GC-MS. Degradation modes involving hydroxylation, oxidative skeletal rearrangement, and ring opening clearly supported enhanced oxidation of phenols by •OH. Overall, due to greater active sites, high surface activity, low band gap, and semiconducting nature, DMCC revealed promising potential for solar photocatalytic remediation of wastewater.

The analysis of microplastics in various environmental samples requires the identification of microplastics from natural materials. The identification technique lacks a standardized protocol. Herein, stereomicroscope and Fourier transform infrared spectroscope (FT-IR) identification methods for microplastics (1mm) were compared using the same samples from the sea surface microlayer (SML) and beach sand. Fragmented microplastics were significantly (p0.05) underestimated and fiber was significantly overestimated using the stereomicroscope both in the SML and beach samples. The total abundance by FT-IR was higher than by microscope both in the SML and beach samples, but they were not significantly (p0.05) different. Depending on the number of samples and the microplastic size range of interest, the appropriate identification method should be determined; selecting a suitable identification method for microplastics is crucial for evaluating microplastic pollution.

Polycyclic aromatic hydrocarbons (PAHs) the ubiquitous, persistent and carcinogenic environmental contaminants have raised concern worldwide. Recently, their removal methodologies are advanced after exploring nanomaterials. Therefore, degradation of selected toxic PAHs (3–5 rings) using potassium zinc hexacyanoferrate (KZnHCF) nanocubes was studied. Highly crystalline and sharp KZnHCF nanocubes (∼100 nm) were obtained by green route using sapindus mukorossi. In both water and soil, anthracene and phenanthrene were degraded to maximum extent (80–93%), whereas, the degradation of fluorene, chrysene and benzo (a) pyrene were ∼70–80%.Because of small size (lower molecular weight), large number of anthracene and phenanthrene molecules were adsorbed on catalyst as compared to other PAHs. Higher degradation of PAHs in water than in the soil is attributed to the easy absorption of PAHs on catalyst in water and slow diffusion of PAHs on organic content of soil. PAHs were degraded at the concentration of 50 mg/L, 25 mg catalyst dose, neutral pH and solar irradiation. Higher proficiency of the catalyst was revealed by degradation of PAHs into small and non-toxic by-products such as malealdehyde, 4-oxobut-2-enoic acid and o-xylene. Overall, the potential KZnHCF nanostructures open future scope for eradication of other pollutants from the environment.

The role of marine plastic debris and microplastics as a carrier of hazardous chemicals in the marine environment is an emerging issue. This study investigated expanded polystyrene (EPS, commonly known as styrofoam) debris, which is a common marine debris item worldwide, and its additive chemical, hexabromocyclododecane (HBCD). To obtain a better understanding of chemical dispersion via EPS pollution in the marine environment, intensive monitoring of HBCD levels in EPS debris and microplastics was conducted in South Korea, where EPS is the predominant marine debris originate mainly from fishing and aquaculture buoys. At the same time, EPS debris were collected from 12 other countries in the Asia-Pacific region, and HBCD concentrations were measured. HBCD was detected extensively in EPS buoy debris and EPS microplastics stranded along the Korean coasts, which might be related to the detection of a quantity of HBCD in non-flame-retardant EPS bead (raw material). The wide detection of the flame retardant in sea-floating buoys, and the recycling of high-HBCD-containing EPS waste inside large buoys highlight the need for proper guidelines for the production and use of EPS raw materials, and the recycling of EPS waste. HBCD was also abundantly detected in EPS debris collected from the Asia-Pacific coastal region, indicating that HBCD contamination via EPS debris is a common environmental issue worldwide. Suspected tsunami debris from Alaskan beaches indicated that EPS debris has the potential for long-range transport in the ocean, accompanying the movement of hazardous chemicals. The results of this study indicate that EPS debris can be a source of HBCD in marine environments and marine food web.

Persistent organic pollutants (POPs) levels in resident and migratory birds collected from an urbanized coastal region of South Korea were investigated. As target species, resident birds that reside in different habitats-such as inland and coastal regions-were selected and their POP contamination status and accumulation features evaluated. Additionally, winter and summer migratory species were analysed for comparison with resident birds. Black-tailed gull and domestic pigeon were selected as the coastal and inland resident birds, respectively, and pacific loon and heron/egret were selected as the winter and summer migratory birds, respectively. The overall POP concentrations (unit: ng/g lipid) in resident birds were 14-131,000 (median: 13,400) for PCBs, 40-284,000 (11,200) for DDTs,1.0-2850 (275) for CHLs, 23-2020 (406) for HCHs, 2-1520 (261) for HCB,0.2-48 (5) for pentachlorobenzene (PeCB), 71-7120 (1840) for PBDEs, and1.8-2300 (408) for HBCDs. In resident birds, the overall level of POPs was higher in seagull compared to pigeon. The stable isotope ratio of nitrogen and carbon indicates that seagull occupies a higher trophic position in the environment than pigeon. However, the POP accumulation profiles in these species differed. Pigeon tends to accumulate more recently used POPs such as PBDEs than seagull. The high-brominated BDE congeners, γ-HBCDs and γ-HCH (also called lindane) were enriched in pigeon compared to seagull, implying the widespread use of Deca-BDE, technical HBCDs, and lindane in the terrestrial environment of South Korea. The different accumulation profile of POPs in both resident species would be related to their habitat difference and trophic positions. For urban resident bird such as pigeon, an intentional intake of dust or soils during feeding is likely to be an additional route of exposure to POPs. Resident birds generally accumulated higher POPs concentrations than migratory birds, the exceptions being relatively volatile compounds such as HCB, PeCB and HCHs.

In this study, the fractionation and ecotoxic potential of Cr, Ni, Cu and Pb in water and sediments of the river Yamuna (Delhi stretch) is presented. The river water is used for various purposes such as irrigation, industrial, domestic and drinking. The investigations suggest that the availability of metals in water follows the sequence Ni>Cr>Pb>Cu whereas a different pattern (Pb>Cu>Ni>Cr) is observed in sediments. Statistically significant spatial variations are indicated by two-way ANOVA in different geochemical forms of the metals and physicochemical parameters of water and sediments of the river Yamuna. Principal component analysis (PCA) suggests a similar source for all four metals probably from the sewage from municipal drains. PCA also indicates some independent sources of Cu and Pb. The hot spots were identified using hierarchical cluster analysis considering bioavailable forms of the metals in water and sediments as objects and the sampling sites as variables. Risk assessment code analysi...

Polycyclic aromatic hydrocarbons (PAHs), pervasive and precedence pollutants have potential to decimate the bionetwork and human health. Therefore, photocatalytic degradation of toxic three membered PAHs, namely acenaphthene (ACN), phenanthrene (PHN) and fluorene (FLU) was explored in water and soil. Titanium dioxide based zinc hexacyanoferrate framework (TiO2@ZnHCF) nanocomposite was synthesized via a two step A. indica mediated co-precipitation method. Under sunlight, fall in concentration of PAHs (Water- 93%–96%, soil- 82%–86% and river sediment- 81.63%–85.43%) with time revealed superior activity of nanocomposite (TiO2@ZnHCF) as compared to the bared one. Slower degradation in soil and sediment could be attributed to the reduced diffusion caused by the interaction between the organic content of soil/sediment with PAHs. Doping caused an increase in surface area (118.15 m2g-1) with decrease in band gap energy (1.65 eV) and photoluminescence intensity. PAHs removal (Xm = 9.48 mg g−1 of ACN, 9.35 mg g−1 of PHN and 8.96 mg g−1 of FLU) involved role of “cation- π” interaction with nanocomposite. Besides, it reduced t1/2 values of ACN (1.88 h), PHN (2.09 h) and FLU (2.86 h) and resulted into smaller by-products. Smaller by-products like (Z)-prop-1-ene-1,2,3-triol (m/z = 91) and (E)-3-hydroxyacrylaldehyde (m/z = 71) identified in GC–MS, evidently braced e− excitement from encapsulated nanocatalyst followed by OH (active species) based oxidation of PAHs. Lower photoluminescence intensity indicates the least charge carrier recombination with highest photocatalytic activity of nanocomposites. Inclusive of the present study provides promising photocatalyst with greater surface activity, low quantum yield with charge separation, reusable up to ten cycles deprived of substantial loss of its action and suppressing the cost of process.

The speciation pattern of heavy metals namely chromium, nickel, copper and lead in water and sediments of an urban lake system of high ecological significance was studied. The total available metal (dissolved) in water follows the sequence Ni>Cr>Pb>Cu. However, a different pattern Pb>Cu>Ni>Cr is observed for total available metal (metal in non-residual phases) in sediments. Significant spatial variations are observed in different geochemical forms of the metals as indicated by two-way ANOVA. This is attributed to localized anthropogenic activities. The anthropogenic parameters of water not only show statistically significant correlations among themselves but also positively correlate with the particulate forms of Cr, Cu and Pb. The total available forms of copper and lead correlate with the organic content of the sediments. Principal component analysis (PCA) separates the metals into three groups: I (Cr); II (Ni); III (Cu and Pb). The polluted sites were identified using hierarchical cluster analysis. Risk assessment code (RAC) analysis indicates low to medium risk due to Cr at most of the sites. However, Ni, Cu and Pb pose medium to high risk. But Pb at a few sites presents very high risk (RAC > 50%).

Organochlorines (OCs) are the most hazardous class of pesticides, therefore, banned or restricted in several countries. The major sources of OCs include food industries, agriculture and sewage wastes. Their effluents discharged into the water bodies contain extremely high concentration of OCs which ultimately causes environmental concern. Because of their high persistence, toxicity and potential to bioaccumulation, their removal from wastewater is imperative. The degradation techniques are now advanced using nanomaterials of various kinds. During the last few years, nanoparticles such as TiO2 and Fe are found to be excellent adsorbents and efficient photocatalysts for degrading more or less whole OCs as well as their toxic metabolites, which opens the opportunities for exploring various other nanoparticles as well. It is noteworthy that such methodologies are economic, fast and very efficient. In this review, the detailed information on different types of OC pesticides, their metabolites, environmental concern and present status on degradation methods using nanoparticles have been reviewed. An attempt has also been made to highlight the research gaps prevailing in the current research area.

The widespread occurrence of pesticide residues in different agricultural and food commodities has raised concern among the environmentalists and food chemists. In order to keep a proper track of these materials, studies on their decay profiles in the various segments of ecosystem under varying environmental conditions are needed. In view of this, the metabolites of quinalphos in water and soil under controlled conditions and in plants, namely tomato and radish in field conditions have been analysed and possible pathways suggested. In order to follow the decay of the pesticide, an HPLC procedure has been developed. Studies conducted in water at different temperatures, pH and organic content reveal that the persistence of the pesticide decreases with the increase in all the three variables. In the three different types of soils studied, the effect of pH is more or less apparent on a similar line. On an average a faster decay is observed in the case of plants than in water and soil. The decay profiles in all these cases follow first order kinetics. The metabolites were identified by GC-MS. The investigations reflect that degradation occurs through hydrolysis, S-oxidation, dealkylation and thiono-thiol rearrangement. The pathways seem to be complex and different metabolites were observed with the change in the matrix. Quinalphos oxon, O-ethyl-O-quinoxalin-2-yl phosphoric acid, 2-hydroxy quinoxaline and quinoxaline-2-thiol were observed in all the matrices. Results further indicate that the metabolites, 2-hydroxy quinoxaline and oxon, which are more toxic than parent compound, persist for a longer time.

A comprehensive study was conducted to evaluate the persistence of thiram in water and soil under controlled conditions and on two plants, namely tomato and radish, in field conditions. In order to follow the decay of the pesticide, an HPLC procedure was developed employing an octadecyl endcapped RP-C18 column using a mixture of acetonitrile and water as the mobile phase and an ultraviolet detector. Studies conducted in water at different temperature, pH and organic content revealed that the persistence of the pesticide decreases with the increase in all the three variables. In the three different types of soils studied, the effect of pH was more or less apparent on a similar line. On average a slower decay was observed in the case of plants than in water and soil. Copyright © 2011 John Wiley & Sons, Ltd.

In order to evaluate the deleterious effects of exposure to pesticides on a target population, a comprehensive study on their degradation in the various segments of ecosystem under varying environmental conditions is needed. In view of this, a study has been carried out on the metabolic pathways of thiram, a dithiocarbamate fungicide, in a variety of matrices namely water and soil under controlled conditions and plants in field conditions. The identification of degradation products was carried out in samples collected at various time points using LC-MS. The degradation products identified can be rationalized as originating by a variety of processes like hydrolysis, oxidation, N-dealkylation and cyclization. As a result of these processes the presence of some metabolites like dimethyl dithiocarbamate, bis(dimethyl carbamoyl) disulphide, bis(dimethyl dithiocarbamoyl) trisulphide and N-methyl-amino-dithiocarbamoyl sulphide was observed in all the cases. However, some different metabolites were observed with the change in the matrix or its characteristics such as cyclised products 2(N, N-dimethyl amino)thiazoline carboxylic acid and 2-thioxo-4-thiazolidine were observed only in plants. The investigations reflect that degradation initiates with hydrolysis, subsequently oxidation/dealkylation, followed by different types of reactions. The pathways seem to be complex and dependent on the matrices. Dimethyl dithiocarbamate and oxon metabolites, which are more toxic than parent compound, seem to persist for a longer time. Results indicate persistence vis-a-vis toxicity of pesticide and its metabolites and also provide a data bank of metabolites for forensic and epidemiological investigations.

A pharmacokinetic in vitro and in vivo degradation study has been carried out in rat to evaluate the deleterious effects of exposure to quinalphos on a target population. Degradation of quinalphos in simulated gastric and intestinal phases has been investigated. The metabolic intermediates of quinalphos in serum and urine of albino rats at different time intervals were identified after dosing the animals with 5 mg kg(-1) body weight. All the samples were lyophilised, extracted and analysed by HPLC and GC-MS. The rate of degradation of quinalphos was accelerated in the presence of the enzymes pepsin and pancreatin contained in the gastric and intestinal simulations, respectively. Quinalphos oxon, O-ethyl-O-quinoxalin-2-yl phosphoric acid, 2-hydroxy quinoxaline and ethyl phosphoric acid are among the important metabolites identified both in in vitro and in vivo investigations. In simulated in vitro study some isomerised derivatives which were missing in the blood and urine of treated animals were identified. This could possibly be either due to non-formation or faster decay of the isomerised derivatives because of slightly different conditions prevailing in the two cases. The results also indicate that the metabolites, 2-hydroxy quinoxaline and oxon, which are more toxic than the parent compound, seem to persist for a longer time.