Dissipation of fenoxycarb and pyriproxyfen in fresh and canned peach

The objective of this work was to determine the dissipation of fenoxycarb and pyriproxyfen in fresh and canned peaches in order to know the levels of residues that can reach consumers in real circumstances. Two field dissipation studies were carried out, one of them at the pre-harvest interval (PHI) with good agricultural practice (GAP) and the other one in a situation of critical agricultural practice (CAP). Two canning dissipation studies were carried out for samples from both agricultural situations in an industrial pilot plant and the dissipation was determined in each relevant step. An analytical methodology was used including acetone-dichloromethane extraction, purification and analysis by liquid chromatography and diode array detection (LC-DAD) with a limit of quantification (LOQ) of 0.05 mg/kg. It was validated under SANCO/10232/2006 Guidelines. These pesticides complied with the official maximum residue limits (MRLs) in peaches at the PHI with good agricultural practices. In hypothetical situation of a second application at the PHI, fenoxycarb and pyriproxyfen residues were above the MRLs in peaches. The canning study reduced the residues to no detectable levels in the cans for consumers.     

Pesticide dissipation curves in peach,pear and tomato crops in Uruguay*

Dissipation curves of azoxystrobin and of the neonicotinoids acetamiprid and thiacloprid in peach; azinphos-methyl and carbaryl in pear and azoxystrobin, chlorfenapyr and chlorpyrifos in high-tunnel tomato crops were studied in the Southern region of Uruguay. An analytical methodology based on solid phase extraction (SPE) and detection by High Performance Liquid Chromatography with Diode Array Detector (HPLC/DAD) was used for acetamiprid and thiacloprid. Coupled SPE and detection by Gas Chromatography with Mass Selective Detector (GC/MSD) was used for the detection of azinphos-methyl, azoxystrobin, carbaryl, chlorfenapyr and chlorpyrifos residues. Curves were modeled mathematically with Solver program of Microsoft Excel®. The best fit for acetamiprid and thiacloprid in peach was achieved with the exponential model (r²=0.961 and 0.944, respectively). In the case of peach fruits there is not a Maximum Residue Limit (MRL) for acetamiprid in the Codex Alimentarius, while 0.5 mg/kg is the value rated for thiacloprid. The MRLs accepted by the European Union (EU) are 0.1 mg/kg for acetamiprid and 0.3 mg/kg for thiacloprid. According to the curves determined in these experiments, thiacloprid residues 10 to 12 days after application (daa) were below the MRLs established by both sources. In the case of acetamiprid, 25 daa would be required, according to the exponential mathematical model, to get residues levels below the MRL values established by the EU. For azinphos methyl in pear, the residues detected were mathematically fitted to an exponential model (r²=0.999). According to it, residue levels under the MRL established by the EU (0.05 mg/kg) are gotten in our conditions in 20 daa. In plastic tunnel tomato chlorfenapyr residues were not detected from 16 daa, having the dissipation curve an exponential trend. In the same condition, there was not a decay of the azoxystrobin concentration during a 24-day trial, being it around 0.40 ± 0.05 mg/kg.     

Dissipation gradients of phenanthrene and pyrene in the Rice rhizosphere

An experiment was conducted to reveal the effects of rice cultivation as well as polycyclic aromatic carbohydrates (PAHs) degrading bacterium (Acinetobacter sp.) on the dissipation gradients of two PAHs (PHE and PYR) in the rhizosphere. The results showed that the presence of rice root and bacteria significantly accelerated the dissipation rate of PHE and PYR. The root exudates contributed to the formation of dissipation gradients of PHE and PYR along the vertical direction of roots, with a higher dissipation rate in the rhizosphere and near rhizosphere zone than the soil far away the rhizosphere.     

Dissipation and translocation of saisenxin in tobacco and soil under conventional field and controlled laboratory conditions

Abstract

The aim of this investigation was to investigate the fate and translocation characteristics of saisenxin (SSX), a novel organic zinc fungicide, in the environment and tobacco plants under conventional field and laboratory conditions. A rapid and sensitive analytical technique based on high-performance liquid chromatography was used for determination of SSX, in soil samples and tobacco leaf, stem and root samples. The method had satisfactiry linearity (R^2?=?0.9999) and the limits of detection and of quantitation of the target compound were 0.06 and 0.20?mg kg^?1, respectively. The average recoveries were in the range of 89.74–94.24% in soil, leaf, stem and root samples, with relative standard deviations of <8%. For conventional field trials, the half-life (t_1/2) of SSX was 5.9–6.5 days in soil and 4.8–5.3 days in tobacco leaves; the corresponding values under controlled laboratory conditions were extended to 7.1 and 7.6?days. The translocation factor (TF) values were in the range of 0–2.25 and 0–0.25 for foliage and root irrigation treatments, respectively. The TFs of SSX in tobacco indicated that tobacco had a high ability to transfer SSX upward.     

Dissipation of glyphosate and aminomethylphosphonic acid in water and sediment of two Canadian prairie wetlands

Glyphosate [N-(phosphonomethyl)glycine] is the active ingredient of several herbicide products first registered for use in 1974 under the tradename Roundup. The use of glyphosate-based herbicides has increased dramatically over the last two decades particularly in association with the adoption of glyphosate-tolerant crops. Glyphosate has been detected in a range of surface waters but this is the first study to monitor its fate in prairie wetlands situated in agricultural fields. An ephemeral wetland (E) and a semi-permanent wetland (SP) were each divided into halves using a polyvinyl curtain. One half of each wetland was fortified with glyphosate with the added mass simulating an accidental direct overspray. Glyphosate dissipated rapidly in the water column of the two prairie wetlands studied (DT₅₀ values of 1.3 and 4.8 d) which may effectively reduce the impact of exposure of aquatic biota to the herbicide. Degradation of glyphosate to its major metabolite aminomethylphosphonic acid (AMPA) and sorption of the herbicide to bottom sediment were more important pathways for the dissipation of glyphosate from the water column than movement of the herbicide with infiltrating water. Presently, we are not aware of any Canadian guidelines for glyphosate residues in sediment of aquatic ecosystems. Since a substantial portion of glyphosate entering prairie wetlands will become associated with bottom sediments, particularly in ephemeral wetlands, guidelines would need to be developed to assess the protection of organisms that spend all or part of their lifecycle in sediment.     

Dissipation,residues, and risk assessment of imidacloprid in Zizania latifolia and purple sweet potato under field conditions using LC-MS/MS

A shortened version of Quick, Easy, Cheap, Effective, Rugged, and Safe method (QuEChERS) for determining the dissipation and residue of imidacloprid present in Zizania latifolia and purple sweet potato was established by using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The average recoveries of imidacloprid in the two crops ranged from 82.12 to 113.79%, with relative standard deviation (RSD) of <7.32%. The dissipation dynamics of imidacloprid in Z. latifolia plants and purple sweet potato plants followed first-order kinetics, with half-lives of 3.2–5.5?days in each of sampling locations. The terminal imidacloprid residues in Z. latifolia and purple sweet potato at each of location were <0.005–0.120?mg kg^?1. According to the risk assessment results, both the acute dietary risk quotient and chronic dietary risk quotient values were <1, indicating that imidacloprid is unlikely to pose health risks to humans with normal recommended use. The present study may serve as a valuable reference for the safe and reasonable use of imidacloprid in Z. latifolia and purple sweet potato fields.     

Dissipation of pendimethalin in the soil of field pea (Pisum sativum L.) and detection of terminal residues in plants

Dissipation of pendimethalin in the soil of field peas (Pisum sativum L.) at 0 to 110 days, and terminal residues in green and mature pea were studied under field conditions. Pendimethalin was applied as pre-emergence herbicide at 750, to 185 g a.i. ha^?1 in winter, in field peas. Dissipation of pendimethalin in the soil at 0 to 110 days followed first-order kinetics showing a half-life of 19.83 days averaged over all doses. Low pendimethalin residues were found in mature pea grain (0.004, 0.003, <0.001 μg g^?1), and straw (0.007, 0.002, <0.001 μg g^?1) at 750, 350 and 185 g a.i. ha^?1 treatments, respectively. The study indicated that residues of pendimethalin in green and mature pea were within the prescribed MRL limits.     

Persistence and distribution of pesticide residues in fresh agricultural food consumed in the province of Bologna

The presence of pesticide residues in fresh vegetables and fruit have been qualitatively and quantitatively determined at the laboratories of the Regional Agency for Environmental Protection (ARPA), Division of the Province of Bologna. More than 1,700 samples have been tested by routine analyses. The possible risks for consumers have been evaluated by various parameters. The most important ones were: the amount of each residue; the respective ADI (Acceptable Daily Intake) limit; the contemporary presence of different residues; an estimation of the daily intake, based on the amount of fruit and vegetables consumed per person. It has been possible to evaluate that the daily intake of pesticide residues in the province of Bologna during the period 2003–06 resulted lower than the ADI limits concerning the vegetables. According to the information on fruit consumption the daily intake of omethoate (O,O-dimethyl S-methylcarbamoylmethyl phosphorothioate) resulted higher than its ADI limit, of dicofol (2,2,2-trichloro-1,1-bis(trichloromethyl)benzenemethanol) very close to the admitted limit, under the respective limits for all the other residues.