Trichlorfon Research Articles

Fe, Cu dual-atom catalysts assisted molecularly imprinted electrochemiluminescence sensor for ultrasensitive detection of trichlorfon

Trichlorfon (TCF) has the possibility of contaminating agricultural crops and posing some health risks to humans. Herein, an electrochemiluminescence (ECL) sensor based on Fe, Cu dual-atom catalysts (Fe/Cu-N-C DACs) and Au@Luminol was developed for the ultrasensitive detection of TCF. Fe/Cu-N-C with diatomic sites has a very high catalytic activity and can be used as a co-reaction accelerator to activate H2O2 to generate a large number of hydroxyl radicals which triggered a strong cathodic ECL signal of luminol. TCF molecularly imprinted polymer (MIP) was further introduced as a specific recognition element, and the interaction between the template molecule and the functional monomer was verified by molecular docking technique. The developed sensing platform was successfully applied to the ultrasensitive detection of TCF with a linear range from 1.0 pg/mL to 5.0 μg/mL with a low detection limit (0.39 pg/mL). This study broadens the application of DACs in ECL sensing.

A recyclable AChE-nanoprobe based on nano-Fe3O4@CHO-β-CD for trichlorfon detection

Trichlorfon (TCF) is an important chemical for pest and parasite control, but it poses risks to public and environmental health. Thus, the detection of TCF is of great value. In this study, we report a strategy to prepare an AChE-nanoprobe for detecting TCF. Benefiting from the unique and excellent structure of CHO-β-CD, this AChE-nanoprobe can wrap nano-Fe3O4 and covalently bind AChE. As a proof of concept, we prepared an AChE-nanoprobe with a hydrated particle size of 717 nm and a saturation magnetic strength of 64.11 emu/g Fe. The properties were studied in detail. Its catalytic activity was 90 % of that of free AChE, and it had broadened pH, thermal, organic solvents and storage in addition to good reusability, with a residual catalytic activity of 42 % after the 10th cycle and a cumulative catalytic activity 6.9 times higher than that of the free enzyme. The AChE-nanoprobe exhibited good performance in TCF detection; the linear range of TCF was 40–4000 ng/L, and the limit of detection for TCF was 2.8 ng/L. Furthermore, our results suggest that the AChE-nanoprobe has several attractive features, such as easy preparation, outstanding stability and reusability, providing a novel and promising tool for the analysis of TCF.

Hollow Prussian blue with ultrafine silver nanoparticle agents (Ag-HPB) integrated sensitive and flexible biosensing platform with highly enzyme loading capability

Herein, the hollow Prussian blue with ultra-small silver nanoparticle agents (Ag-HPB) was prepared by the coating-etching method by applying Prussian blue (PB) coating on Ag nanoparticles (Ag NPs) and diffusing Ag NPs into the PB framework. The flexible biosensing platform based on Ag-HPB nanocomposites incorporated the excellent electrical conductivity of Ag NPs and the superior enzyme loading capacity of the hollow structure, which significantly enhanced its sensing performance. Subsequently, take glucose oxidase (GOx) and acetylcholinesterase (AChE) as examples. The sensing platform displayed a good sensitive response to glucose (Glu) (24.37 μA mM−1 cm−2) and a considerable limit of detection (LOD) for trichlorfon (TCF) as 2.28 pg/mL while exhibiting high stability and good reproducibility. Moreover, it can be applied to monitor trichlorfon in apple samples. Promisingly, the Ag-HPB prepared by the coating-etching strategy provides a reliable strategy for further development of sensitive and flexible biosensing platforms with excellent electrical conductivity and high enzyme loading.

Phytoremediation of cadmium-trichlorfon co-contaminated water by Indian mustard (Brassica juncea): growth and physiological responses

In this study, the morphological and physiological responses of Brassica juncea to the stresses of Cadmium (Cd) and trichlorfon (TCF), and the phytoremediation potential of B. juncea to Cd and TCF were investigated under hydroponics. Results showed that Cd exhibited strong inhibition on biomass and root morphology of B. juncea as Cd concentration increased. The chlorophyll a fluorescence intensity and chlorophyll content of B. juncea decreased with the increased Cd concentration, whereas the malondialdehyde and soluble protein contents and superoxide dismutase activity increased. TCF with different concentrations showed no significant influence on these morphological and physiological features of B. juncea. The biomass and physiological status of B. juncea were predominantly regulated by Cd level under the co-exposure of Cd and TCF. B. juncea could accumulate Cd in different plant parts, as well as showed efficient TCF degradation performance. A mutual inhibitory removal of Cd and TCF was observed under their co-system. The present study clearly signified the physiological responses and phytoremediation potential of B. juncea toward Cd and TCF, and these results suggest that B. juncea can be used as an effective phytoremediation agent for the Cd-TCF co-contamination in water.

Effects of isolated and combined exposures of Boana curupi (Anura: Hylidae) tadpoles to environmental doses of trichlorfon and ultraviolet radiation

The biodiversity collapse strongly affects the amphibian group and many factors have been pointed out as catalytic agents. It is estimated that several events in the amphibian population decline worldwide may have been caused by the interaction of multiple drivers. Thus, this study aimed to evaluate the stressful effects of the exposure to environmental doses of trichlorfon (TCF) pesticide (0.5 μg/L; and an additional 100-fold concentration of 50 µg/L) and ultraviolet radiation (UV) (184.0 kJ/m² of UVA and 3.4 kJ/m² of UVB, which correspond to 5% of the daily dose) in tadpoles of the Boana curupi species (Anura: Hylidae). The isolated and combined exposures to TCF happened within 24 h of acute treatments under laboratory-controlled conditions. In the combined treatments, we adopted three different moments (M) of tadpole irradiation from the beginning of the exposures to TCF (0 h – M1; 12 h – M2; and 24 h – M3). Then, we evaluated tadpole survival, change in morphological characters, induction of apoptotic cells, lipid peroxidation (LPO), protein carbonyl content (PCC), glutathione S-transferase (GST), non-protein thiols (NPSH), and acetylcholinesterase (AChE), as well as the induction of genomic DNA (gDNA) damage. UVB treatment alone resulted in high mortality, along with a high level of apoptosis induction. Both UVA, UVB, and TCF increased LPO, PC, and AChE, while decreased GST activity. Regarding co-exposures, the most striking effect was observed in the interaction between UVB and TCF, which surprisingly decreased UVB-induced tadpole mortality, apoptosis, and gDNA damage. These results reinforce the B. curupi sensitivity to solar UVB radiation and indicate a complex response in face of UVB interaction with TCF, which may be related to activation of DNA repair pathways and/or inhibition of apoptosis, decreasing UVB-induced tadpole mortality.

First study on response of astrocytes in alevines of red-bellied pacu (Piaractus brachypomus) to subchronic exposure to chlorpyrifos and trichlorfon.

Background and Aim:Organophosphate pesticides (OPs) used in agricultural production pose environmental and public health risks whenever non-target organisms are exposed to them. Oxon-type OPs, such as trichlorfon (TCF) and chlorpyrifos (CPF), are frequently used in Colombia and have been detected in water bodies in the vicinity of croplands; however, their effect on aquatic organisms, especially fish, is largely unknown. The neurotoxicity of OPs includes inhibition of esterase enzymes, neuronal damage, and increased glial reactivity. This study aimed to assess the astrocytic response in the brain tissue of juvenile red-bellied pacu (Piaractus brachypomus) exposed to TCF and CPF.Materials and Methods:A 25-day subchronic assay was conducted in which juvenile red-bellied pacu were exposed to CPF and TCF. After 25 days of exposure, the fish were killed and brain samples were collected and processed for immunohistochemistry to assess the morphology and reactivity of astrocytes; glial acidic fibrillary protein was used as a biomarker.Results:The brain samples from animals under subchronic exposure to OPs for 25 days showed higher cellular density as well as changes in astrocyte phenotype characterized by shortening of cytoplasmic projections, hypertrophy, and ameboid morphology compared to those from nonexposed animals. Similarly, astrocyte hyperreactivity was detected in the optic tectum and medial longitudinal fasciculus of the exposed group.Conclusion:Immunoreactivity of brain glial cells under subchronic exposure to OPs measured through immunohistochemical tests as well as OPs-induced neuropathology may be useful as a biomarker for monitoring environmental pollution. The results also indicate that P. brachypomus is a suitable biomonitoring model for studying neurotoxicological and neurodegenerative diseases.

Correlation of bacterial community with phosphorus fraction drives discovery of Actinobacteria involved soil phosphorus transformation during the trichlorfon degradation

Trichlorfon (TCF) is a broad-spectrum phosphorus (P)-containing pesticide, yet its effects on soil P fraction transformation and bacterial communities during the TCF degradation in soils is unknown. In this study, we investigated soil TCF degradation behavior at different contents of 50, 100 and 200 mg/kg, and analyzed residual TCF contents and metabolites by gas chromatography mass spectrometry after 216-h incubation. Our results suggested that TCF was gradually degraded in soils and was be initially hydrolyzed to dichlorvos via P–C bond cleavage and then other P-containing metabolites. By analyzing different P fractions and soil microbial community composition, we found significant increases of soil available phosphorus contents from 2.76 mg/kg (control) to 3.23 mg/kg (TCF-50), 5.12 mg/kg (TCF-100) and 5.72 mg/kg (TCF-200), respectively. Inorganic CaCl2–P was easily and instantly transformed to primary mineral inorganic P (Pi) forms of HCl–P and citrate-P, while the proportion of enzyme-P (a labile organic P) fluctuated throughout TCF degradation process. Soil available P contents and Pi fractions were significantly correlated with the relative abundance of Actinobacteria. These results highlighted that Actinobacteria is the dominant soil species utilizing TCF as P sources to increase its community richness, and subsequently affect the transformation of P fractions to regulate soil P cycle. Our study gives new understanding on the microorganisms can involve soil P transformation during organophosphorus pesticides degradation in soils, highlighting the importance of bacteria in P transformation and pesticides soil decontamination.

Modulation of the cholinergic pathway induced by skin secretion of Phyllomedusa iheringii Boulenger, 1885 in a vertebrate model

Amphibians represent one of the main natural sources of bioactive molecules of interest to biotechnological research. The Phyllomedusidae family has several species occurring in Brazil and some studies demonstrate the biological potential of poisons of these species, however many still need to be characterized. Phyllomedusa iheringii is endemic in Brazilian and Uruguayan Pampa Biome and has little data in the literature regarding the action of its poison on experimental organisms. Thus, the present work evaluates the biological activity of P. iheringii secretion on the central and peripheral nervous system of a vertebrate model. The skin secretions of P. iheringii (SSPI) were collected through manual compression and electrical stimulation of the animal's bodies. The resulting content was used in neurobiological tests searching for modulatory effects on the main pathways involved in the neurotoxicity mechanism of vertebrates. SSPI affected the contraction force of the chick biventer cervicis muscle (Gallus gallus domesticus) at some concentrations used (5, 10, and 12 μg/mL). In slices from the cerebral cortex of G. gallus domesticus an increase in cell viability was observed after treatment with SSPI (10 μg/mL) and a neuroprotective effect when treated simultaneously with hydrogen peroxide (H2O2), Neostigmine (NEO) and Trichlorfon (TRI). The cholinergic pathway is possibly the main pathway modulated by SSPI since assays with the cerebral cortex and biventer cervicis muscle demonstrated the increased activity of the enzyme acetylcholinesterase (AChE) (SSPI 10 μg/mL and 12 μg/mL, respectively). SSPI (10 μg/mL) also prevented the modulation of NEO and TRI, two recognized anticholinesterase agents, in AChE activity in slices of the cerebral cortex. Therefore, our results have demonstrated the unpublished biotechnological potential of P. iheringii over the vertebrate model and its modulation on the nervous system, with apparent action on the cholinergic pathway.

Removal of pesticide residues from fresh vegetables by the coupled free chlorine/ultrasound process

Pesticide residue in vegetables has been considered as a serious food safety problem across the whole world. This study investigates a novel advanced oxidation process (AOP), namely the coupled free chlorine/ultrasound (FC/US) process for the removal of three typical pesticides from lettuce. The removal efficiencies of dimethoate (DMT), trichlorfon (TCF) and carbofuran (CBF) from lettuce reached 86.7%, 79.8% and 71.3%, respectively by the FC/US process. There existed a synergistic effect in the coupled FC/US process for pesticide removal and the synergistic factors reached 22.3%, 19.0% and 36.4% for DMT, TCF and CBF, respectively. Based on the analysis of mass balance of pesticides, the synergistic effect was probably attributed to the efficient oxidation of pesticides both in vegetables and in water by the generated free radicals and FC. The surface area and surface structure of vegetables strongly affected the removal of pesticides by FC/US. The removal efficiency of DMT increased from 80.9% to 88.1% as solution pH increased from 5.0 to 8.0, and then decreased to 84.1% when solution pH further increased to 9.0. When the ultrasonic frequency changed from 20 to 40 kHz, a remarkable improvement in pesticide removal by FC/US was observed. As the FC concentration increased from 0 to 15 mg L–l, the removal efficiencies of pesticides increased firstly, and then became stagnant when the FC concentration further increased to 25 mg L–l. The pesticide degradation pathways based on the identified intermediates were proposed. The total chlorophyll content was reduced by less than 5% after the FC/US process, indicating a negligible damage to the quality of vegetables. It suggests that the FC/US process is a promising AOP for pesticides removal from vegetables.

Temperature-dependent pharmacokinetics of trichlorfon in common carp (Cyprinus carpio L.) after bath immersion therapy.

The common carp (Cyprinus carpio L.) is one of the most important freshwater fish species. As C.carpio culture has escalated, bacterial and parasitic infections have become a real threat to the industry. Antibacterial and antiparasitic treatments are provided for infection control in C.carpio. However, adequate vaccines have not yet been developed. Trichlorfon (TCF), an organophosphate, is an antiparasitic agent used in aquaculture to treat external parasites. However, there are few pharmacokinetic (PK) studies on its use in fish. This study investigated the residue elimination and temperature-dependent PK characteristics of TCF in C.carpio at 15°C and 25°C after 30mg/L TCF bath immersion for 30min. TCF residue concentrations in plasma and muscle tissues were determined using liquid chromatography-tandem mass spectrometry and further analyzed using a noncompartmental model. Temperature significantly affected specific PK parameters. Increasing the temperature from 15°C to 25°C shortened the elimination half-life from 36.07 to 22.72h. The time to reach the maximum plasma TCF residue concentration (Cmax ) (Tmax ) remained the same (0.5h), but Cmax increased from 67.72 to 70.76µg/L. The area under the plasma concentration-time curve decreased from 1,057.31 to 962.14h∙µg/L. The muscle TCF Cmax was 446.99µg/L with a corresponding Tmax of 0.5h at 25°C, and 267.53µg/L, with a corresponding Tmax of 1.0h at 15°C. The temperature-sensitive PK parameters, such as increased in Cmax and decreased elimination and distribution rates, significantly affected the plasma TCF residue concentration and its overall exposure to increasing temperature. Temperature affected the therapeutic outcomes of TCF treatment in C.carpio and likely other freshwater fish. Therefore, proper dosing regimens should take temperature into consideration.

Determination of acute median lethal concentration and sublethal effects on AChE activity of Gymnotus carapo (Teleostei: Gymnotidae) exposed to trichlorfon

Trichlorfon (TRF) is a pesticide widely used in aquaculture to control fish ectoparasites. This pesticide is an inhibitor of acetylcholinesterase, an essential enzyme for termination of nerve impulses. High rates of TRF use generate risks to the environment and human health. In the environment, pesticides can affect the local fauna and generate an ecological breakdown. There are several studies performed with fish production; however, gaps are created for native fish with other commercial values. The tuvira (Gymnotus carapo) is a fish native to Brazilian fauna and has great commercial importance in sport fishing. The present study aimed to determine the lethal concentration of trichlorfon (Masoten) in Gymnotus carapo and its sublethal effects on the enzyme AChE. In this study, the acute toxicity (the concentrations to kill 50% of the fish LC50) of TRF in tuviras (Gymnotus carapo) and acetylcholinesterase inhibition in liver and muscle tissue of tuviras submitted to sublethal concentrations were evaluated. For the acute assay, concentrations of 0.0, 5.0, 7.5, 15, 22.5, 30, 37.5 and 45 mg L-1 were used for a period of 96 h. After the acute exposure period, a LC50 of 6.38 mg L-1 was determined. In the sublethal assay, concentrations of 0.0, 0.238, 0.438 and 0.638 mg L-1 were used, based on 10% of the LC50, over a period of 14 days. Two collections were performed: one at seven days and the other at the end (day 14). Inhibition of acetylcholinesterase in the liver was only shown (p < 0.05) for the treatment with 0.638 mg L-1 after 14 days of exposure. At seven days, muscle activity showed a significant difference only for the treatments 0.438 and 0.638 mg L-1, compared with the treatment 0.238 mg L-1 and control. At 14 days of exposure, only the treatment 0.638 mg L-1 showed significant differences in relation to the other groups, thus showing that enzyme recovery had occurred. The value found in the acute test allowed the conclusion that TRF presents moderately toxic characteristics to Gymnotus carapo. The toxicity parameter values calculated in the present study assisted in estimation of maximum allowable limits in bodies of water when combined with test data from other non-target organisms.

Toxicity, Biodegradation, and Metabolic Fate of Organophosphorus Pesticide Trichlorfon on the Freshwater Algae Chlamydomonas reinhardtii.

This study investigated the toxicity of trichlorfon (TCF) to the freshwater algae Chlamydomonas reinhardtii, as well as its biodegradation and metabolic fate. The growth of C. reinhardtii decreased with increasing TCF concentration, and the maximum inhibition ratio was 51.3% at 200 mg L-1 TCF compared to the control. Analyses of pigment content, chlorophyll fluorescence, and antioxidant enzymes indicated that C. reinhardtii can produce resistance and acclimatize to the presence of TCF. The variations in pH during cultivation suggested that photosynthetic microalgae have innate advantages over bacteria and fungi in remediating TCF. A 100% biodegradation rate was achieved at a maximum concentration of 100 mg L-1 TCF. Ten metabolites were identified by GC-MS, and the degradation pathways of TCF by the algae were proposed. This research demonstrated that C. reinhardtii is highly tolerant to and can efficiently degrade TCF. Thus, C. reinhardtii can be used to remove traces of TCF from natural water environments and to treat TCF-contaminated wastewater.

Enhanced removal of trichlorfon and Cd(II) from aqueous solution by magnetically separable chitosan beads immobilized Aspergillus sydowii

Simultaneous removal of heavy metals and organics from wastewater has always been an environmental problem with great concern. In this study, a novel ecofriendly bioborbent, magnetic chitosan beads immobilized Aspergillus sydowii (MCBAs) were synthesized and used to simultaneously remove trichlorfon (TCF) and Cd(II) from aqueous solution. MCBAs showed an increased special surface area (55.38 m2·g−1) through immobilizing A. sydowii and its saturation magnetization reached 14.62 emu·g−1. The equilibrium removal capacities of TCF and Cd(II) were 135.43 mg·g−1 and 56.40 mg·g−1 in the co-system with 200 mg·L−1 TCF and 50 mg·L−1 Cd(II), respectively. The removal capacities of TCF and Cd(II) were strongly depended on the immobilized A. sydowii spore concentration, initial concentrations of TCF and Cd(II), and MCBAs dose. TCF biodegradation intermediates were identified by gas chromatography–mass spectrometry system. Fourier transform infrared spectra displayed that –OH and –NH groups on MCBAs mainly participated in the Cd(II) sequestration and the CO stretching vibration was possibly related to the degradation intermediates of TCF. MCBAs exhibited excellent recyclability upto four cycles. Therefore, MCBAs are suitable and effective for the simultaneous removal of TCF and Cd(II) from wastewater.

Effects of trichlorfon on oxidative stress, neurotoxicity, and cortisol levels in common carp, Cyprinus carpio L., at different temperatures

Trichlorfon (TCF) is an organophosphate compound used extensively as an anti-parasitic in aquaculture. In this study, we investigated the effects of TCF on the antioxidant defense system, acetylcholinesterase (AChE) activity, and stress responses in various tissues of common carp (Cyprinus carpio L.). C.carpio L. were exposed to different concentrations of TCF (0, 0.5, 1.0, 2.0, and 4 mg L−1) at 25 and 15 °C for two weeks (measurements were taken after week 1 and 2). TCF exposure induced significant alterations in antioxidant responses in the gills and the liver. The activities of superoxide dismutase (SOD) and glutathione S-transferase (GST) increased considerably after TCF exposure, depending on water temperature, whereas catalase (CAT) and glutathione (GSH) levels decreased notably after one and two weeks. Remarkable antioxidant responses were observed in the gills, suggesting the gills were more sensitive to oxidative stress than the liver based on CAT, GST, and GSH levels. Notable increases in MDA levels were observed in the gills and the liver. AChE activity was significantly inhibited in the brain and muscles even at the lowest TCF concentration of 0.5 mg L−1, indicating neurotoxicity following TCF exposure. As a stress indicator, plasma cortisol was significantly elevated following exposure to TCF depending on water temperature, thereby enhancing stress. These results suggest that TCF exposure can induce considerable alterations in antioxidant responses, neurotoxicity, and stress reaction depending on water temperature. The assayed enzymes are potential biomarkers of organophosphate contamination.

Effect of trichlorfon on some haematological and biochemical changes in Cyprinus carpio: The ameliorative effect of lycopene

Trichlorfon (TCF) is an antiparasitic agent used in aquaculture to treat external parasites and it belongs to the chemical class of organophosphates. This study was conducted to investigate the ameliorating effects of lycopene on TCF-induced toxicity in carp by evaluating haematological parameters and oxidant/antioxidant status. Fish were randomly divided into seven experimental groups. These groups were arranged as follows: control (no treatment) group, corn oil group, lycopene (10 mg kg−1) group, TCF-I (11 mg L−1) group, TCF-I (11 mg L−1) plus lycopene (10 mg kg−1) group, TCF-II (22 mg L−1) group and TCF-II (22 mg L−1) plus lycopene (10 mg kg−1) group. At the end of 14 days administration, blood and tissue (liver, kidney, and gill) samples were collected. Haematological changes [red blood cell (RBC) and white blood cell (WBC) count, haemoglobin (Hb) concentration, haematocrit (Ht) level, and erythrocyte indices: mean corpuscular volume (MCV), mean corpuscular haemoglobin (MCH), and mean corpuscular haemoglobin concentration (MCHC)] were determined in the blood samples, while antioxidant parameters [(malondialdehyde (MDA) and reduced glutathione (GSH) levels and superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) activities] were evaluated in the liver, kidney and gill samples. The results demonstrated that all the haematological parameters were significantly decreased in the TCF-I and TCF-II groups when compared to the control group. Notable increases in the tissue MDA levels were observed in the TCF-treated groups. In contrast, significant decreases were observed in the tissue SOD, CAT and GSH-Px activities and GSH levels in the TCF-I and TCF-II groups. However, simultaneous treatment with lycopene provided a marked normalisation of the haematological and oxidant/antioxidant parameters compared with the TCF-I and TCF-II groups. The findings show that dietary lycopene supplementation might be helpful in abrogation of TCF toxicity by changing haematological conditions and antioxidant status in fish.

Development of a hydrophilic molecularly imprinted polymer for the detection of hydrophilic targets using quartz crystal microbalance

In this study, we describe the development and applicability of a molecularly imprinted polymer (MIP) based on the facile modification of a hydrophobic polymer, poly(vinylidene difluoride) (PVDF), in a sensor for the detection of trichlorfon (TCF) as a representative hydrophilic organophosphate pesticide. This sensor was developed from its polymer as opposed to conventional in-situ polymerization methods. The performance of the TCF MIP sensor was evaluated using a quartz crystal microbalance (QCM) achieving a good linear response between 0–250 ppb and a limit of detection (LOD) of 4.63 ppb and a limit of quantitation (LOQ) of 15.77 ppb. The sensor demonstrated high selectivity in the presence of structural analogues including dimethoate, acephate, dichlorvos, malathion as well as carbaryl and carbosulfan. The sensor was also found to have satisfactory stability when monitored over a 20-day period. The developed method was successfully applied to detect TCF in spiked lettuce samples. The novelty of the proposed method lies in the assimilation of concepts from membrane modification into MIP sensor fabrication and demonstrates the possibility of utilizing polymers directly for a simple yet effective sensor development.

Simultaneous degradation of trichlorfon and removal of Cd(II) by Aspergillus sydowii strain PA F-2.

Co-contamination with heavy metals and pesticides is a severe environmental problem, but little information is available regarding the simultaneous removal of these pollutants. In this study, we showed that Aspergillus sydowii strain PA F-2 isolated from soil contaminated with heavy metal and pesticides can simultaneously degrade trichlorfon (TCF) and adsorb Cd(II) from mineral salt medium. The maximum removal rates for TCF and Cd(II) were 55.52% and 57.90%, respectively, in the treatment containing 100 mg L-1 TCF and 2 mg L-1 Cd(II). As the initial Cd(II) concentration increased (2, 5, and 10 mg L-1), the PA F-2 biomass, TCF degradation rate, and Cd(II) adsorption efficiency decreased, whereas the Cd(II) adsorption capacity by PA F-2 increased. The addition of exogenous glucose and sucrose significantly increased the PA F-2 biomass as well as the removal of TCF and Cd(II). Moreover, the TCF degradation pathway and Cd(II) adsorption mechanism were investigated by gas chromatography-mass spectrometry, scanning electron microscopy, and Fourier transform infrared spectroscopy. These results suggest that PA F-2 has potential applications in the bioremediation of TCF and Cd(II) co-contamination.

Toxicological Interactions of Organophosphorus Pesticides Mixtures to Chlorella pyrenoidosa

The toxicity effects of combined pesticides pollution have potential risks to aquatic environment. To investigate the combined toxicity effects of organophosphorus pesticides (OPs) mixtures on green algae in freshwater ecosystems, five OPs, i.e. malathion (MIT), dichlorvos (DDVP), trichlorfon (TRC), dimethoate (DIT) and omethoate (OMT), were selected as the mixture components. Nine OPs binary mixture systems contained 45 mixture rays were designed by a direct equipartition ray design (EquRay) method. The growth inhibition toxicities of the five single OPs and 45 binary mixture rays to Chlorella pyrenoidosa (C. pyrenoidosa) were determined using the 96-well microplate. Combination index based on the confidence intervals method was applied to analyze the toxicological interactions in OPs binary mixtures. Taking the negative logarithm of median effective concentration (pEC50) as toxicity index, the toxicity order of five OPs was as follows: TRC > MIT > DDVP > OMT > DIT. The toxicity of single OPs to C. pyrenoidosa was affected by the electropositivity of its phosphorus. The combined toxicity of some OPs mixtures depended on component concentrations. The toxicological interactions of OPs mixtures on C. pyrenoidosa were dominated by additive action, and some mixtures presented antagonism behavior. In addition, the mixture systems with antagonism displayed additive effects at low-effect regions and showed antagonistic effects at high-effect regions. The antagonism of the mixture systems containing MIT were strengthened with the increasing of MIT concentration ratio. It was worth noting that the toxicological interactions of OPs mixtures were related to component concentration ratio. Meanwhile, the concentration-ratio-dependent interactions of OPs mixtures were not associated with their concentration-ratio-dependent toxicity.

Enantioseparation and enantioselective behavior of trichlorfon enantiomers in sediments.

Trichlorfon (TF), an organophosphorus insecticide, has been widely used in seawater aquaculture; it is easily degraded to the highly toxic insecticide, dichlorvos (DDVP). In this study, the enantioseparation of TF enantiomers, as well as their degradation behavior and product (DDVP) formation in mariculture pond sediments, was investigated. The results show that both TF enantiomers degrade into DDVP, which is the main degradation product. Furthermore, S-(+)-TF is preferentially degraded under natural conditions, suggesting that TF enantiomers degrade enantioselectively. Nevertheless, the degradation behavior of TF enantiomers is not enantiospecific under sterile conditions. The formation of DDVP and the enantiospecific degradation of TF enantiomers are attributed to the activities of microbes present in the sediments.

Performance of trichlorfon degradation by a novel Bacillus tequilensis strain PA F-3 and its proposed biodegradation pathway.

The novel trichlorfon (TCF)-degrading bacterium PA F-3, identified as Bacillus tequilensis, was isolated from pesticide-polluted soils by using an effective screening and domesticating procedure. The TCF biodegradation pathways of PA F-3 were also systematically elucidated. As revealed by high-performance liquid chromatography, the TCF residues in the mineral salt medium demonstrated that PA F-3 can utilize TCF as its sole carbon source and reach the highest degradation of 71.1% at an initial TCF concentration of 200mg/L within 5days. The TCF degradation conditions were optimized using response surface methodology as follows: temperature, 28°C; inoculum amount, 4%; and initial TCF concentration, 125mg/L. Biodegradation treatments supplemented with exogenous carbon sources and yeast extract markedly increased the microbial dry weights and TCF-degrading performance of PA F-3, respectively. Meanwhile, five metabolic products of TCF were identified through gas chromatography/mass spectrometry, and a biodegradation pathway was proposed. Results indicated that deoxidation and dehydration (including the cleavage of the P-C phosphonate bond and the C-O bond) were the preferred metabolic reactions of TCF in this TCF-degrading bacterium.