Pesticides, particle size distribution

Japan and Korea accoimt for 80-85% of the world s annual production of about 2 million metric tons. US pyrophyllite, 3% of the world s total, is all dry groimd and more or less abrasive depending on the particle size distribution of its quartz content. As such, it is generally overlooked in filler applications in favor of kaolin or talc. In the US the ceramics and refractories industries consume about 75% of the pyrophyllite produced. Pesticides take 10% of production, and filler uses (paint, joint cements, mastics) take 3-5%. 

Lewis, R.G., Fortune, C.R., Willis, R.D., Camann, D.E. and Andey, J.T. (1999) Distribution of pesticides and polycyclic aromatic hydrocarbons in house dust as a function of particle size. Environmental Health Perspectives, 107, 721-6. 

The transport phenomenon for any spray material released In the air Is foremost a function of the particle size and size distribution of the released spray. The particle density plays a minor role, the settling rate from Stokes law for example varies as the square root of the density. Further, the density differences between liquids commonly used for pesticides Is very little, varying only slightly from water at density of 1 gm/ml. Other formulation physical factors of surface tension, viscosity and viscoelasticity play significant roles In the atomization process. These are altered by the addition of petroleum and vegetable oil as solvents and carriers as well as a host of adjuvants In varying... 

A novel device was designed to estimate the dislodgeability of dust-associated pesticide residues by skin contact (Edwards and Lioy, 1999). Called the EL Sampler , the device consists of a spring-loaded assembly that permits the sampling medium to be pressed lightly (12g/cm or 1160 Pa) onto the surface to be monitored. A 10-cm x 15-cm Empore C-18 extraction membrane was used for the sampling medium. The material was chosen after controlled experiments on particle adhesion showed it to pick up the same distribution of test dust particle sizes as the human hand. In studies in which the EL sampler was pressed onto polyethylene surfaces coated with house dust and then sprayed with a solution of pesticides in 2-propanol, the device was found to collect 35%, 31 %, 32% and 18 %, respectively, of chlorpyrifos, diazinon (0,0-diethyl 0-[6-methyl-2-(l-methylethyl)-4-pyrimidinyl] phosphorothioate), malathion and atrazine (6-chloro-A -ethyl-A -isopropyl-l,3,5-triazine-2,4-diamine). Parallel studies with human hand presses (full hand at 6.8 kg = ca. 6900 Pa) yielded collection efficiencies of 42 %, 29 %, 43 % and 21 %, respectively. 

Chao MR, Hu CW, Ma HW, Chang-Chien GP, Lee WJ, Chang LW, Wu KY (2003) Size distribution of particle-bound polychlorinated dibenzo-p-dioxins and dibenzofurans in the ambient air of a municipal incinerator. Atmos Environ 37 4945-4954 Chiysikou LP, Gemenetzis PG, Samara CA (2009) Wintertime size distributions of polycyclic aromatic hydrocarbons (PAH), polychlorinated biphenyls (PCB) and organochlorine pesticides (OCPs) in the urban environment street- vs. rooftop-level measurements. Atmos Environ 43 290-300... 

Perhaps the most common use for EHDA is the production of fine particles in narrow size distributions. These particles are applicable for drug-delivery systems, synthesis of nanoparticles, thin film deposits, superconductors, quantum dots, photoionic crystals, paint technology, and agricultural applications like pesticide spraying. Several examples of applications for electrospraying in published studies demonstrate the abilities of EHDA for mass production. 

Wu, S.P., Cao, J., et al., 2003. Residues and distribution of organochlorine pesticides in airborne particles of different sizes from urban areas. Res. Environ. Sci. (Chinese) 16,... 

Other than AUNPs, Quantum dots have also been employed in the development of pesticide sensors. Li et al. have synthesized Poly (N-vinyl-2-pyrrolione) (PVP)-capped CdS quantum dots (QCdS-PVP) from CdC and Na2S in the presence of PVP [37], AChE was immobilized onto this QCdS-PVP matrix incorporated GCE surface. The resulting GCE/ QCdS-PVP/AChE sensor was used for the detection of OP pesticides, such as trichlorfon. The enzyme immobilization procedure was described as follows. About 3 ml of QCdS-PVP was deposited on the surface of the GCE and dried in air. Then 3 ml of 0.5 mg ml"1 AChE along with 2.5% GA was deposited on the surface of the QCdS-PVP modified GCE and dried for 1 h at room temperature. TEM results show that, the QCdS-PVP particles were homogeneously distributed and they possess an average size of 2-4 nm (Fig. 9). 

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