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Presents the findings of a study where elastic lidar was applied to PM10 emissions from agricultural nonpoint sources. Why PM10 emissions from nonpoint sources needs to be quantified; Identification of various objects for measurement of PM10 missions from agricultural nonpoint sources; Qualitative capabilities of the lidar instrument.

Examines sorption rates of hydrophobic organic compounds (HOC) in iron oxide- and aluminosilicate clay-coated aquifer sands. Quantification of coating thickness; Sand textures and coating properties; HOC transport through coated sands; Unavailable organic matter in intact aquifer sands.

Tillage-induced erosion of herbicides bound to airborne soil particles has not been quantified as a mechanism for off- site herbicide transport. This study quantifies the release of two preemergent herbicides, metolachlor and pen-dimethalin, to the atmosphere as gas- and particle-phase species during soil incorporation operations. Fine particulate matter (PM2.5) and gas-phase samples were collected at three sampling heights during herbicide disking into the soil in Davis, CA, in May 2000 and May 2001 using filter/PUF sampling. Quartz fiber filters (QFFs) were used in May 2000, and Teflon membrane filters (TMFs) were used in May 2001. The field data were combined with laboratory filter/PUF partitioning experiments to account for adsorption to the filter surfaces and quantify the mass of PM2.5-bound herbicides in the field samples. Laboratory results indicate a significant adsorption of metolachlor, but not pendimethalin, to the quartz filter surfaces. Metolachlor partitioning to PM2.5 collected on TMF filters resulted in corrected PM23 field partition coefficient values, Kp,corr = Cp/ Cg of ≈ 10-3.5 m3/μg, indicating its preference for the gas phase. Pendimethalin exhibited more semivolatile behavior, with Kp,corr values that ranged from 10-3 to 10-1 m3/ μg and increased with sampling height and distance downwind of the operation. An increase in pendimethalin enrichment at a height of 5 m suggests winnowing of finer, more sorptive soil components with corresponding higher transport potential. Pendimethalin was enriched in the PM2.5 samples by up to a factor of 250 compared to the field soil, indicating that further research on the processes controlling the generation of PM-bound herbicides during agricultural operations is warranted to enable prediction of off-site mass fluxes by this mechanism. [ABSTRACT FROM AUTHOR]

A microfabricated electrostatic precipitator successfully demonstrated its airborne liquid phase particles precipitation functionality. The particles used in the experiments were polydispersed liquid phase oleic acid particles with sizes ranging from 30 nm to 300 nm. Two configurations with electrode gaps of 1.8 mm and 2.0 mm were tested at 2.2 kV and 2.6 kV, respectively. During the test, the microfabricated electrostatic precipitator was inserted into a flow chamber with an aerosol stream containing oleic acid particles. Particle precipitation is demonstrated via both visual observation and the measurement of the corona current during aerosol exposure. The corona current for the 2.0 mm electrode gap configuration was decreased by approximately 50% and the circuit resistivity is increased by the corresponding magnitude as the oleic acid particles precipitated during a 60 s exposure. The recovery of corona current is observed when the aerosol source is turned off. Wicking of precipitated oleic acid away from the collection grid to its anchoring feature is observed. The analytical and experimental corona current versus time elapsed during the aerosol exposure are calculated and compared. The discrepancy between the analytical and experimental corona currents is consistent with the observed wicking effect and variation in percent coverage on the collector grid by precipitating particles. \hfill[2013\--0016] [ABSTRACT FROM AUTHOR]

Airborne particles are separated according to their electrical mobilities using a microfabricated corona ionizer and separator electrodes. Oleic acid particles with sizes ranging from 30 to 300 nm are used to characterize the device. They are generated using a TSI 3075 constant output atomizer. These particles are electrically charged by a microfabricated corona ionizer, and the resultant particle electrical mobility is a function of the size of the particle. A varying dc potential difference of 0-2 kV across the separator electrodes selects charged particles of various electrical mobilities. These separated particles are subsequently counted using a TSI 3025A Condensation Particle Counter. The device demonstrated its ability to separate particles between 50 and 130 am into five distinct size bins. The operational flow rate is 0.5 L/min, and the micropin-between-planes corona ionizer operates at 1.3 kV with 7μA. The theoretical and experimental electrical mobilities of the particles are compared. [ABSTRACT FROM AUTHOR]

A microfabricated corona ionizer is developed for miniaturized air particle monitoring instruments. Peek's breakdown criterion and Warburg's Law are used to calculate the required electrode geometries. Single mask electroplating is employed as the microfabrication technique. Devices with discharge pin radius of 20 µm and interelectrode spacing of 1.4, 1.8, 2.0, and 2.2 mm are fabricated and tested. The inception voltages in the range from 1.4 to 2 kV are achieved without substrate breakdown. It consumes relatively low power at 150 mW or less. Corona charging currents of more than 50 µA were achieved before streamers break down. The experimental results also demonstrated the nondependency of the inception voltage on the pin's radius of curvature so long as it is significantly smaller than the interelectrode spacing. There is only one value of inception voltage for each given interelectrode spacing (1.4 to 2.2 mm) with the pin's radius of curvature ranging from 10 to 200 µm. This implies that strict dimensional control is not required in the microfabrication process in order to ensure the same inception voltage for each device. [ABSTRACT FROM AUTHOR]