Carbaryl deposition

A similar air application made in absence of an inversion resulted in carbaryl deposits (2.29 v>g S-radian) at a maximum of 300 m and off-target downwind. In no instances was captan deposits detected with the carbaryl deposits found at the furthest off-target sites. 

The design and implementation of a portable fiber-optic cholinesterase biosensor for the detection and determination of pesticides carbaryl and dichlorvos was presented by Andreou81. The sensing bioactive material was a three-layer sandwich. The enzyme cholinesterase was immobilized on the outer layer, consisting of hydrophilic modified polyvinylidenefluoride membrane. The membrane was in contact with an intermediate sol-gel layer that incorporated bromocresol purple, deposited on an inner disk. The sensor operated in a static mode at room temperature and the rate of the inhibited reaction served as an analytical signal. This method was successfully applied to the direct analysis of natural water samples (detection and determination of these pesticides), without sample pretreatment, and since the biosensor setup is fully portable (in a small case), it is suitable for in-field use. 

Studies were initiated at Iowa State University in 1977 to determine if pesticides would be contained and degraded when deposited in water/soil systems. Although the addition of known amounts of the selected pesticides was controlled, the physical environment was not temperature, humidity, wind speed, etc. were normal for the climate of Central Iowa. Four herbicides and two insecticides were chosen on the basis of three factors. Firstly, they represented six different families of pesticides. The four herbicides, alachlor, atrazine, trifluralin, and 2,4-D ester, represent the acetanilides, triazines, dinitroanilines, and phenoxy acid herbicides, respectively. The two insecticides, carbaryl and para-thion, represent the carbamate and organophosphorus insecticides, respectively. Secondly, the pesticides were chosen on the basis of current and projected use in Iowa Q) and the Midwest. Thirdly, the chosen pesticides were ones for which analytical methodology was available. 

Unknown amounts of these formulations and Amiben, Carbaryl, Chlordane, Cythion, Heptachlor, Maneb, Pyrethrum, Toxaphene and Zineb were deposited prior to the commencement of record keeping beginning June 1977. In addition to the listed pesticides 2619 g of Citcop, NAA, N-Serve, Dipel, Omite and Metasytox were deposited but not analyzed. 

RJ Argauger, RE Webb. Rapid fluorometric evaluation of the deposition and persistence of carbaryl in the presence of an adjuvant on bean and tomato leaves. J Agric Food Chem 20 732-734, 1972. 

An MIP-QCM chemosensor for determination of carbamate pesticides, such as carbaryl, has been devised [130]. The chemosensor featured a thin film of PVC, containing carbaryl-imprinted polymer microspheres, which was deposited on top of the gold-sputtered quartz crystal transducer. The microspheres were prepared by thermo-induced co-polymerization in ACN of MAA and EGDMA, used as the functional monomer and cross-linker, respectively, in the presence of carbaryl and AIBN serving as the template and initiator, respectively. The chemosensor performance was evaluated for determination of carbaryl exhibiting the linear concentration range of 10-1000 ng mL-1 in the Britton-Robinson buffer of pH = 8.0. This chemosensor was highly stable. It selectively discriminated carbaryl from its structural counterparts, such as carbofuran and aldicarb, with LOD of 1.25 ng mL-1 carbaryl. 

Bystanders. The bystander had the lowest exposure to carbaryl of all the workers monitored. In keeping the bystander within 100 feet and downwind of the ground applicator, the bystander often had to walk into the field while it was being treated. This practice resulted in exposure when the hands of the bystander touched the crop foliage. Thus, with peas, there was no exposure because the plants were too small at the time of spraying for any inadvertent contact, but with relatively mature potatoes, measurable residues were deposited on the bystander. For example, when 80S was applied to this crop, the bystander had a total HDE of 0.5 mg/h... 

Evidence was obtained recently that pesticide vapors may enter the air by still another mechanism, involving plant circulation and water loss (57). Rice plants were found to efficiently transport root-zone applied systemic carbamate insecticides via xylem flow to the leaves, eventually to the leaf surface by the processes of guttation and/or stomatal transpiration, and finally to the air by surface volatilization. Results from a model chamber showed that 4.2, 5.8, and 5.7% of the residues of carbaryl, carbofuran, and aldicarb, respectively, present in rice plants after root soaking vaporized within 10 days after treatment. The major process was evaporation of surface residues deposited by guttation fluid. 

Recovery of deposits on the teflon discs were made by washing the disc in 70% acetonitrile for 30 min. During the course of these studies, a total of 395 carbaryl analyses, and 519 captan analyses were made. 

In 1980, five applications of a carbaryl/captan mixture were used, two by ground and three by air, as indicated in Table I. Analyses of off-target depositions showed that carbaryl consistently drifted further than captan when applied by air (Figure 1). One would expect that the drifting particulates would have both pesticides present, and that levels of each would be detected wherever drift occurred. This unexpected result cannot be readily attributed to sensitivity of the analyses since all samples were well above the sensitivity limits (10 ng for captan and 0.01 ng for carbaryl). The vapor pressure of captan is appreciably lower than that of carbaryl and if volatilization from drifting minute particulates was a factor, captan should have been found in greater quantities than carbaryl. 

Comparison of two ground carbaryl/captan applications, (Figure 2) showed that in absence of an inversion no off-target deposits were seen, whereas the application during an inversion resulted in maximum off-target downwind deposits of both captan (.62 pg N-radian) and carbaryl (.58 pg N-radian) at 150 m downwind. 

One example The use of the pinolene polymer (f-Pinene) with carbaryl allows an increased deposition and decreased rate of decay of the carbaryl on tomato leaves. There is a three-fold period of release that the carbaryl remains on the leaf. This residual extension of the pesticide by the use of pinolene results from the occlusion and dissolution of the pesticide within the pliant film that pinolene forms on the leaf.21... 

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