Effect of pre-exposure on acute toxicity of organophosphorus insecticides to white mice.

LD50 and in vitro ChE I50 values of Chlorpyrifos, Leptophos, Phosfolan, and Stirophos against white mice showed that the formulated insecticides were higher in their mammalian toxicity than the corresponding technical materials. Pretreatment of mice with a sublethal dose of Phosfolan potentiated the toxicity of post-treatment with formulated Stirophos, Phosfolan, or Chlorpyrifos, but antagonized the toxicity of post-treatment with Leptophos. On the other hand, pretreatment with sublethal doses of Leptophos resulted in potentiation of Stirophos or Phosfolan, but decreased the toxicity of Chlorpyrifos or Leptophos. Pretreatment of mice by sublethal dose of Phosfolan synergized the in vivo inhibitory power of post-treatment by Phosfolan, Chlorpyrifos or Leptophos against brain and Plasma ChE. On the other hand pretreatment with sublethal doses of Leptophos antagonized the inhibitory power of post-treatment with either Chlorpyrifos, Leptophos or Stirophos against mice brain-ChE.     

Use of treated bark for the removal of lipids from water

Raw, biologically treated bark and bark impregnated with transition metal ions were used to retain the lipids from synthetic emulsions. Several experimental parameters affecting the lipid removal efficiency (RE) were studied (initial concentration of lipids, temperature, time, pH, carboxylic acid chain length, etc.). Saturated bark was characterized using Fourier transform infrared (FTIR) spectroscopy and light microscopy, and the treated bark wetting index was determined. Results show that lipid removal can exceed 95% of the initial concentration at a pH lower than 7. The uptake of lipids by these sorbents varied from 0.2 to 2.5 g/g of dry bark. Trials for regenerating the sorbent saturated by lipids allowed the recovery of approximately 95% of lipids. The calorific value of the saturated bark was approximately 79% that of domestic fuel and can be considered as an energy source, thus avoiding its waste disposal. These results may upgrade the treatment of wastewater generated by several industrial sectors, such as the food industry, surface treatment, and so on.     

Occurrence and potential toxicity of pyrethroids and other insecticides in bed sediments of urban streams in central Texas

Despite heavy insecticide usage in urban areas, only a few studies have investigated the impact of current-use insecticides on benthic invertebrates in urban streams. The objective of this study was to measure the presence and concentration of current-use pesticides in sediments of residential streams in central Texas. Additionally, toxicity of these sediments to Hyalella azteca was evaluated. Sediment samples were collected from several sites in urban streams over the course of a year, of which, 66% had greater than one toxic unit (TU) of insecticide. Bifenthrin was the greatest contributor accounting for 65% of the TUs, and sediment toxicity to H. azteca correlated with the magnitude of total insecticides and bifenthrin TUs. The results of this study further raise concerns over the environmental consequences posed by many current-use insecticides, especially pyrethroids, in urban settings.     

Methyl parathion toxicity to and removal efficiency by Typha latifolia in water and artificial sediments

Methyl parathion (MeP) is a very hazardous pesticide freely used in agriculture in Mexico. This pesticide and others, arriving through different processes, exert significant effects on water quality with serious consequences for environmental and human health. This study evaluates the removal efficiency of common cattail Typha latifolia L. on MeP in water and artificial sediments. The effects of the pesticide on this macrophyte after 10 days of exposure were determined using a concentration range of 0-200 mg l(-1), 198.1+/-1.79 g average biomass, pH 7.0, 18-22 degrees C temperature and natural daylight/darkness periods, using chlorophyll production as a biomarker. Removal kinetics were conducted under similar conditions on days 0, 3, 7, 9, 11 and 14 of exposure, using 6 mg l(-1) in each system. Pesticide concentration, chlorophyll content and glutathione S-transferase (GST) activity were quantified. Results show a high removal efficiency of cattails on MeP in water and sediments relative to controls. An increase in GST activity and a decline in chlorophyll content in the test systems were not significantly different relative to controls. Cattails may thus be a good candidate for development of a phytoremediation system for MeP-contaminated water and artificial sediments.     

Altered physiology, cell structure, and gene expression of Theobroma cacao seedlings subjected to Cu toxicity

Seedlings of Theobroma cacao CCN 51 genotype were grown under greenhouse conditions and exposed to increasing concentrations of Cu (0.005, 1, 2, 4, 8, 16, and 32 mg Cu L^?1) in nutrient solution. When doses were equal or higher than 8 mg Cu L^?1, after 24 h of treatment application, leaf gas exchange was highly affected and changes in chloroplasts thylakoids of leaf mesophyll cells and plasmolysis of cells from the root cortical region were observed. In addition, cell membranes of roots and leaves were damaged. In leaves, 96 h after treatments started, increases in the percentage of electrolyte leakage through membranes were observed with increases of Cu in the nutrient solution. Moreover, there was an increase in the concentration of thiobarbituric acid-reactive substances in roots due to lipid peroxidation of membranes. Chemical analysis showed that increases in Cu concentrations in vegetative organs of T. cacao increased with the increase of the metal in the nutrient solution, but there was a greater accumulation of Cu in roots than in shoots. The excess of Cu interfered in the levels of Mn, Zn, Fe, Mg, K, and Ca in different organs of T. cacao. Analysis of gene expression via RTq-PCR showed increased levels of MT2b, SODCyt, and PER-1 expression in roots and of MT2b, PSBA, PSBO, SODCyt, and SODChI in leaves. Hence, it was concluded that Cu in nutrient solution at doses equal or above 8 mg L^?1 significantly affected leaf gas exchange, cell ultrastructure, and transport of mineral nutrients in seedlings of this T. cacao genotype.     

Altered toxicity of organic pollutants in water originated from simultaneous exposure to UV photolysis and CdSe/ZnS quantum dots

The paper reports unforeseen results of increased toxicity of water, subsequent to interactions between CdSe/ZnS quantum dots (QDs), phenol and toluene under UV irradiation. The consistent pattern of changes in measured toxicity (TU) was observed and correlated with degradation of phenol and/or toluene. Spearman rank coefficients (SRCs) for data pairs sum-parameters vs. TU were calculated. The highest correlation between toxicity and degradation by-products was observed for hydroquinone (0.86) and catechol (0.89). The presence of QDs in tested concentration range in the absence of UV has shown low toxicity and no interactions with phenol and/or toluene. The leak of constituent core and shell metal ions was observed. The minor differences in physical characteristics of tested QDs of the same chemical composition led to rather different degradation patterns of phenol and toluene, and the amount of leak of the metal ions as well.     

Photodegradation of organophosphorus insecticides - investigations of products and their toxicity using gas chromatography-mass spectrometry and AChE-thermal lens spectrometric bioassay

Four organophosphorus compounds: azinphos-methyl, chlorpyrifos, malathion and malaoxon in aqueous solution were degraded by using a 125 W xenon parabolic lamp. Gas chromatography-mass spectrometry (GC-MS) was used to monitor the disappearance of starting compounds and formation of degradation products as a function of time. AChE-thermal lens spectrometric bioassay was employed to assess the toxicity of photoproducts. The photodegradation kinetics can be described by a first-order degradation curve C=C0e(-kt), resulting in the following half lives: 2.5min for azinphos-methyl, 11.6 min for malathion, 13.3 min for chlorpyrifos and 45.5 min for malaoxon, under given experimental conditions. During the photoprocess several intermediates were identified by GC-MS suggesting the pathway of OP degradation. The oxidation of chlorpyrifos results in the formation of chlorpyrifos-oxon as the main identified photoproduct. In case of malathion and azinphos-methyl the corresponding oxon analogues were not detected. The formation of diethyl (dimethoxy-phosphoryl) succinate in traces was observed during photodegradation of malaoxon and malathion. Several other photoproducts including trimethyl phosphate esters, which are known to be AChE inhibitors and 1,2,3-benzotriazin-4(3H)-one as a member of triazine compounds were identified in photodegraded samples of malathion, malaoxon, and azinphos-methyl. Based on this, two main degradation pathways can be proposed, both result of the (P-S-C) bond cleavage taking place at the side of leaving group. The enhanced inhibition of AChE observed with the TLS bioassay during the initial 30 min of photodegradation in case of all four OPs, confirmed the formation of toxic intermediates. With the continuation of irradiation, the AChE inhibition decreased, indicating that the formed toxic compounds were further degraded to AChE non-inhibiting products. The presented results demonstrate the importance of toxicity monitoring during the degradation of OPs in processes of waste water remediation, before releasing it into the environment.     

Occurrence,compositional distribution,and toxicity assessment of pyrethroid insecticides in sediments from the fluvial systems of Chaohu Lake,Eastern China

Surface sediment-associated synthetic pyrethroid insecticides (SPs) are known to pose high risks to the benthic organisms in Chaohu Lake, a shallow lake of Eastern China. However, the pollution status of the lake’s tributaries and estuaries is still unknown. The present study was conducted to investigate the occurrence, compositional distribution, and toxicity of 12 currently used SPs in the surface sediments from four important tributaries, as well as in the sediment cores at their estuaries, using GC-MS for quantification. All SPs selected were detectable, with cypermethrin, es/fenvalerate, and permethrin dominant in both surface and core sediments, suggesting that these compounds were extensively applied. Urban samples contained the highest summed concentrations of the 12 SPs analyzed (Σ₁₂SP) in both surface and core sediments compared with rural samples, suggesting that urban areas near aquatic environments posed high risks for SPs. The mean concentration of Σ₁₂SP in surface sediments of each river was generally higher than that found in core sediments from its corresponding estuary, perhaps implying recent increases in SP usage. Surface sediments were significantly dominated by cypermethrin and permethrin, whereas core sediments were dominated by permethrin and es/fenvalerate. The compositional distributions demonstrated a spatial variation for surface sediments because urban sediments generally contained greater percentages of permethrin and cypermethrin, but rural sediments had significant levels of es/fenvalerate and cypermethrin. In all sediment cores, the percentage of permethrin gradually increased, whereas es/fenvalerate tended to decrease, from the bottom sediments to the top, indicating that the former represented fresh input, whereas the latter represented historical residue. Most urban samples would be expected to be highly toxic to benthic organisms due to the residue of SPs based on a calculation of toxic units (TUs) using toxicity data of the amphipod Hyalella azteca. However, low TU values were found for the samples from rural areas. These results indicate that the bottom sediments were exposed to high risk largely by the residual SPs from urban areas. The summed TUs were mostly attributable to cypermethrin, followed by λ-cyhalothrin and es/fenvalerate. Despite permethrin contributing ～28.7 % of the Σ₁₂SP concentration, it only represented 6.34 % of the summed TUs. Therefore, our results suggest that high levels of urbanization can increase the accumulation of SPs in aquatic environments.     

The impact of material design on the photocatalytic removal efficiency and toxicity of two textile dyes

Environmental Science and Pollution Research - This study deals with the toxicity of the treated solutions of two types of dyes, namely, the anthraquinonic Reactive Bleu 19 dye (RB19) and the...     

Use of hairy roots extracts for 2,4-DCP removal and toxicity evaluation by Lactuca sativa test

2,4-Dichlorophenol (2,4-DCP) is widely distributed in wastewaters discharged from several industries, and it is considered as a priority pollutant due to its high toxicity. In this study, the use of different peroxidase extracts for 2,4-DCP removal from aqueous solutions was investigated. Tobacco hairy roots (HRs), wild-type (WT), and double-transgenic (DT) for tomato basic peroxidases (TPX1 and TPX2) were used to obtain different peroxidase extracts: total peroxidases (TPx), soluble peroxidases (SPx), and peroxidases ionically bound to the cell wall (IBPx). All extracts derived from DT HRs exhibited higher peroxidase activity than those obtained from WT HRs. TPx and IBPx DT extracts showed the highest catalytic efficiency values. The optimal conditions for 2,4-DCP oxidation were pH 6.5, H₂O₂ 0.5 mM, and 200 U mL^?1 of enzyme, for all extracts analyzed. Although both TPx extracts were able to oxidize different 2,4-DCP concentrations, the removal efficiency was higher for TPx DT. Polyethylene glycol addition slightly improved 2,4-DCP removal efficiency, and it showed some protective effect on TPx WT after 2,4-DCP oxidation. In addition, using Lactuca sativa test, a reduction of the toxicity of post removal solutions was observed, for both TPx extracts. The results demonstrate that TPx extracts from both tobacco HRs appear to be promising candidate for future applications in removing 2,4-DCP from wastewaters. This is particularly true considering that these peroxidase sources are associated with low costs and are readily available. However, TPx DT has increased peroxidase activity, catalytic efficiency, and higher removal efficiency than TPx WT, probably due to the expression of TPX1 and TPX2 isoenzymes.     

The effect of certain intrinsic and extrinsic variables on the acute toxicity of selected organophosphorus insecticides to the mummichog,Fundulus heteroclitus

Abstract

The acute toxicity of two organophosphorus (OP) insecticides, azinphosmethyl and acephate, was evaluated in the mummichog, Fundulus heteroclitus. In addition, the effects of certain intrinsic (sex) and extrinsic (salinity and multiple toxicant interraction) variables on the toxic response were also investigated. Azinphosmethyl was by far the most toxic of the two OP insecticides with a 96h LC50 ～ 100,000 x lower than that for acephate. Slight sex differences were observed in the sensitivity of mummichogs to each of the OP insecticides with male fish being marginally more sensitive. Significant effects of low salinity stress were observed only with acephate exposure and, in this case, low salinity appeared to be slightly protective. In general, all of the insecticide mixtures (azinphosmethyl/endosulfan, azinphosmethyl/fenvalerate and acephate/fenvalerate) tested exhibited simple additive toxicity.     

Acute contact toxicity test of insecticides (Cipermetrina 25, Lorsban 48E, Thionex 35) on honeybees in the southwestern zone of Uruguay

Glyphosate-resistant soybean cultivation is expanding rapidly in Uruguay, with its land area having increased by 95 times during the past 10 years. Because of the region's Neotropical conditions, insecticide use is required to ensure adequate soybean productivity. However, in areas shared by soybean crops and beekeepers - such as the southwestern zone of Uruguay (SWZU) - the use of insecticides can increase the risks of honeybee death and honey contamination. Uruguayan commercial and legal guidelines set out practices and field doses designed to prevent acute intoxication with insecticides. However, honeybees in the SWZU are predominantly a polyhybrid subspecies different from that used to set international reference values, and hence they may have a different acute toxicity response, thus rendering such precautions ineffective. The aim of this work was to assess the acute toxicity response of polyhybrid honeybees in the SWZU to cypermethrin (commercial formulation: Cipermetrina 25 Agrin?), chlorpyrifos (commercial formulation: Lorsban 48E?), and endosulfan (commercial formulation: Thionex 35?). Acute toxicity bioassays were conducted to determine the median lethal dose (LD(50)) of each insecticide for the honeybees. The results indicate that, compared with EU reference values, SWZU honeybees have a higher toxicological sensitivity to chlorpyrifos and endosulfan, and a lower toxicological sensitivity to cypermethrin, based on the commercial formulations tested. However, when these results were adjusted according to their field dose equivalents, only chlorpyrifos emerged as a potential problem for beekeeping, as the maximum recommended field dose of Lorsban 48E? for soybean crops in Uruguay is 23 times the corresponding LD(50) for honeybees in the SWZU.     

Selective removal of organic contaminants from sediments: a methodology for toxicity identification evaluations (TIEs)

Aqueous slurries of a test sediment spiked with dibenz[a,h]anthracene, 2,4,5,2',4',5'-hexachlorobiphenyl, p,p'-DDE, or phenanthrene were subjected to decontamination experimentation. The spiked sediments were agitated at elevated temperatures for at least 96 h in the presence of either of the two contaminant-absorbing media: clusters of polyethylene membrane or lipid-containing semipermeable membrane devices (SPMDs). The effects of treatment temperature and surface area of media on the removal of contaminants were explored. This work is part of a larger methodology for whole-sediment toxicity identification evaluation (TIE). A method is being sought that is capable of detoxifying sediments with respect to organic contaminants while leaving toxicity attributable to inorganic contaminants unaffected.     

The effect of certain intrinsic and extrinsic variables on the acute toxicity of selected organophosphorus insecticides to the mummichog, Fundulus heteroclitus.

The acute toxicity of two organophosphorus (OP) insecticides, azinphosmethyl and acephate, was evaluated in the mummichog, Fundulus heteroclitus. In addition, the effects of certain intrinsic (sex) and extrinsic (salinity and multiple toxicant interraction) variables on the toxic response were also investigated. Azinphosmethyl was by far the most toxic of the two OP insecticides with a 96h LC50 approximately 100,000 x lower than that for acephate. Slight sex differences were observed in the sensitivity of mummichogs to each of the OP insecticides with male fish being marginally more sensitive. Significant effects of low salinity stress were observed only with acephate exposure and, in this case, low salinity appeared to be slightly protective. In general, all of the insecticide mixtures (azinphosmethyl/endosulfan, azinphosmethyl/fenvalerate and acephate/fenvalerate) tested exhibited simple additive toxicity.     

Screening of physical-chemical methods for removal of organic material, nitrogen and toxicity from low strength landfill leachates

Physical-chemical methods have been suggested for the treatment of low strength municipal landfill leachates. Therefore, applicability of nanofiltration and air stripping were screened in laboratory-scale for the removal of organic matter, ammonia, and toxicity from low strength leachates (NH4-N 74-220 mg/l, chemical oxygen demand (COD) 190-920 mg O2/l, EC50 = 2-17% for Raphidocelis subcapitata). Ozonation was studied as well, but with the emphasis on enhancing biodegradability of leachates. Nanofiltration (25 degrees C) removed 52-66% of COD and 27-50% of ammonia, the latter indicating that ammonia may in part have been present as ammonium salt complexes. Biological pretreatment enhanced the overall COD removal. Air stripping (24 h at pH 11) resulted in 89% and 64% ammonia removal at 20 and 6 degrees C, respectively, the stripping rate remaining below 10 mg N/l h. COD removals of 4-21% were obtained in stripping. Ozonation (20 degrees C) increased the concentration of rapidly biodegradable COD (RBCOD), but the proportion of RBCOD of total COD was still below 20% indicating poor biological treatability. The effect of the different treatments on leachate toxicity was assessed with the Daphnia acute toxicity test (Daphnia magna) and algal growth inhibition test (Raphidcocelis subcapitata). None of the methods was effective in toxicity removal. By way of comparison, treatment in a full-scale biological plant decreased leachate toxicity to half of the initial value. Although leachate toxicity significantly correlated with COD and ammonia in untreated and treated leachate, in some stripping and ozonation experiments toxicity was increased in spite of COD and ammonia removals.     

Removal mechanisms and fate of insecticides in constructed wetlands

Constructed wetlands (CWs), along with other vegetative systems, are increasingly being promoted as a mitigation practice to treat non-point source runoff to reduce contaminants such as pesticides. However, studies so far have mostly focused on demonstrating contaminant removal efficiency. In this study, using two operational CWs located in the Central Valley of California, we explored the mechanisms underlying the removal of pyrethroids and chlorpyrifos from agricultural runoff water, and further evaluated the likelihood for the retained pesticides to accumulate within the CWs over time.In the runoff water passing through the CWs, pyrethroids were associated overwhelmingly with suspended solids >0.7 μm, and the sorbed fraction accounted for 38-100% of the total concentrations. The derived K_d values for the suspended solids were in the order of 10⁴-10⁵, substantially greater than those reported for bulk soils and sediments. Distribution of pyrethroids in the wetland sediments was found to mimic organic carbon distribution, and was enriched in large particles that were partially decomposed plant materials, and clay-size particles (<2 μm). Retention of suspended particles, especially the very large particles (>250 μm) and the very fine particles, is thus essential in removing pyrethroids and chlorpyrifos in CWs. Under flooded and anaerobic conditions, most pyrethroids and chlorpyrifos showed moderate persistence, with DT₅₀ values between 106-353 d. However, the retained pyrethroids were very stable in dry and aerobic sediments between irrigation seasons, suggesting a possibility for accumulation over time. Therefore, the long-term ecological risks of CWs should be further understood before their wide adoption.     

Sorption and degradation of neonicotinoid insecticides in tropical soils

ABSTRACT

Neonicotinoids are the most widely applied class of insecticides in cocoa farming in Ghana. Despite the intensive application of these insecticides, knowledge of their fate in the Ghanaian and sub-Saharan African environment remains low. This study examined the behavior of neonicotinoids in soils from cocoa plantations in Ghana by estimating their sorption and degradation using established kinetic models and isotherms. Studies of sorption were conducted using the batch equilibrium method on imidacloprid, thiamethoxam, clothianidin, acetamiprid and thiacloprid, while degradation of imidacloprid, thiamethoxam and their respective deuterated counterparts was studied using models proposed by the European forum for coordination of pesticide fate and their use (FOCUS). Analytes were extracted using the quick, easy, cheap, effective, rugged and safe (QuEChERS) procedure and quantified by liquid chromatography-tandem mass spectrometry (LC–MS/MS). Average recoveries were high (≥ 85%) for all analytes. The findings from the study suggest that neonicotinoid insecticides may be persistent in the soils studied based on estimated half-lives > 150 days. The study also revealed generally low-sorption coefficients for neonicotinoids in soils, largely influenced by soil organic carbon.     

Treatment of two insecticides in an electrochemical Fenton system

Abstract

The ability of an electrochemical Fenton system to degrade the organophosphorous insecticides malathion and methyl parathion was studied. A combination of hydrogen peroxide and electrochemically‐generated iron was found to be successful in degrading the two insecticides, and optimization of the system was pursued. Augmentation with near UV light at an intensity of 1.67xl0¹⁷ quanta/sec and centered at a wavelength of 370 nm improved the degradation of malathion at low iron concentrations but did not affect other treatments. Adding the hydrogen peroxide slowly over the course of treatment rather than all at once at the beginning of each treatment did, however, greatly improve the system. Removal efficiencies of 98.0% or greater were achieved for both pesticides.     

Distribution of organophosphate insecticides in a Thai biomass-water system

Sorption and leaching of the organophosphate (OP) pesticides chlorpyrifos, profenofos, methyl parathion and malathion were investigated with four different types of biomass: coconut husk, rice husk, peat moss and peanut shell. Organic carbon contents of the biomass were in the range of 35.4–45.4%. Sorption studies were carried out by the batch (equilibrium) method at 4 different OP spike concentrations and at pH 3–7. Sorption isotherms conformed to a linear Freundlich equation and the Freundlich constant or sorption coefficient (K_D) confirmed that biomass organic carbon content was the principal sorbent factor affecting OP sorption. For a given sorbent, correlation of the extent of sorption with sorbate chemical properties was examined. Column leaching experiments involving different masses of coconut husk and peanut shell pre-spiked with OPs at the level equivalent to actual spraying concentrations in some Thai tangerine orchards were conducted. These experiments included repeated spikings and leaching. A water flow rate of 20 mL min^?1 was employed corresponding to the current average watering regime. Retardation and biodegradation with these sorbents were also examined.     

Distribution of organophosphate insecticides in a Thai biomass-water system

Sorption and leaching of the organophosphate (OP) pesticides chlorpyrifos, profenofos, methyl parathion and malathion were investigated with four different types of biomass: coconut husk, rice husk, peat moss and peanut shell. Organic carbon contents of the biomass were in the range of 35.4-45.4%. Sorption studies were carried out by the batch (equilibrium) method at 4 different OP spike concentrations and at pH 3-7. Sorption isotherms conformed to a linear Freundlich equation and the Freundlich constant or sorption coefficient (KD) confirmed that biomass organic carbon content was the principal sorbent factor affecting OP sorption. For a given sorbent, correlation of the extent of sorption with sorbate chemical properties was examined. Column leaching experiments involving different masses of coconut husk and peanut shell pre-spiked with OPs at the level equivalent to actual spraying concentrations in some Thai tangerine orchards were conducted. These experiments included repeated spikings and leaching. A water flow rate of 20 mL min(-1) was employed corresponding to the current average watering regime. Retardation and biodegradation with these sorbents were also examined.