Airborne collection

Two pheromonal components were detected in airborne collections from the vine mealybug, Planococcus ficus Signoret (Hemiptera Pseudococci dae) in Israel. They were identified as (5 )-lavandulyl senecioate (1) and (5)-lavandulyl isovalerate (II). Compound I has been identified as the sex pheromone of P. ficus in California. The report shows that feral P. ficus mealybugs produce and respond only to (I) whereas mealybugs reared in the laboratory on potato sprouts produce and respond to both (I) and (II). 

Other considerations relevant to airborne collection and determination of atmospheric samples speciated by phase include ... 

The discussion that follows first describes techniques for the airborne collection of a definable atmospheric phase for subsequent determinations, then continues with discussion of the analysis techniques themselves including those for nitrogen oxides and oxyacids, sulfur oxides, oxidants and selected organic species. Emphasis is on the modified instrumentation devised and used by Brookhaven National Laboratory staff to improve the selectivity and lower the limits of detection of these techniques (1). 

Maleic Anhydride. The ACGIH threshold limit value in air for maleic anhydride is 0.25 ppm and the OSHA permissible exposure level (PEL) is also 0.25 ppm (181). Maleic anhydride is a corrosive irritant to eyes, skin, and mucous membranes. Pulmonary edema (collection of fluid in the lungs) can result from airborne exposure. Skin contact should be avoided by the use of mbber gloves. Dust respirators should be used when maleic anhydride dust is present. Maleic anhydride is combustible when exposed to heat or flame and can react vigorously on contact with oxidizers. The material reacts exothermically with water or steam. Violent decompositions of maleic anhydride can be catalyzed at high temperature by strong bases (sodium hydroxide, potassium hydroxide, calcium hydroxide, alkaU metals, and amines). Precaution should be taken during the manufacture and use of maleic anhydride to minimize the presence of basic materials. 

High performance Hquid chromatography (hplc) may be used to determine nitroparaffins by utilizing a standard uv detector at 254 nm. This method is particularly appHcable to small amounts of nitroparaffins present, eg, in nitro alcohols (qv), which caimot be analyzed easily by gas chromatography. Suitable methods for monitoring and deterrnination of airborne nitromethane, nitroethane, and 2-nitropropane have been pubUshed by the National Institute of Occupational Safety and Health (NIOSH) (97). Ordinary sorbant tubes containing charcoal are unsatisfactory, because the nitroparaffins decompose on it unless the tubes are held in dry ice and analyzed as soon after collection as possible. 

As fibers in the feed mat pass between the feed toU and feed plate, they ate separated by metallic wine teeth on the lickerin toU and carried to an air venturi where they ate stripped and tumbled until they strike a moving, perforated collection surface. At the collection surface, the airborne fibers foUow paths of least resistance and accumulate in a self-leveling manner while the air passes through perforations. Fiber orientation in the web is isotropic in layers corresponding to the number of fibers transferred from the wine teeth to the air-transportation 2one, the intensity of the air, and the speed of the collection surface. 

Airborne organic sihcon has been detected in samples collected at Barrow, Alaska (509). Organic sihcon levels corresponding to an airborne concentration of 8 ng/m were detected. As a comparison, these samples were deterrnined to hold approximately 20 ng/m of phthalate-based plasticizers. 

The most common supported tubes are those with membranes cast in place (Fig. 17). These porous tubes are made of resin-impregnated fiber glass, sintered polyolefins, and similar materials. Typical inside diameters are ca 25 mm. The tubes are most often shrouded to aid in permeate collection and reduce airborne contamination. 

A large number of fibers ate cut to length, and potted in epoxy resin at each end (see Embedding). The fiber bundle is shrouded in a cylinder which aids in permeate collection, reduces airborne contarnination, and allows back pressing of the membrane. HoUow-fiber membranes (qv) have also found use in ultrafilttation. 

A fraction of airborne salt always passes through the filter. The method recommended for determining whether or not the foulants have a substantial salt base is to soap wash the turbine and collect the water from all drainage ports available. Dissolved salts in the water can then be analyzed. 

In the forcc-ventilated or drip-proof types, the cooling air passes directly over the motor winding insulation. As a rule of thumb, a motor requires about 4,000 cfm of cooling air per thousand horsepower. Therefore, the possibilities of airborne dust and dirt collecting on the winding must he considered carefully. Filters in the air intake will lessen the hazards of this condition. Not much can be done about moisture drawn in with the cooling air, but careful selection of motor location inside ihe shelter can minimize the amount of wind-blown rain striking the motor. 

List several types of air cleaning devices that can be used to remove airborne particulate matter. Rank these in order of their collection efficiency and typical maximum size particle capture. 

Airflow Systems, Inc Resource for the collection and filtration of dust, smoke, mist, fumes and other airborne contaminants generated during industrial and commercial manufacturing and processing applications. http., llwww.air, flowsvstems. com... 

The running of a cool airflow under a warm wind is another cause of temperature inversion. As a rule, the presence of an inversion implies a highly stable atmosphere one in which vertical air movements is rapidly damped out. In such a situation, fog and airborne pollutants collect, being unable to move freely or be dissipated by convection. 

Fig 10 shows the variation of airborne gunshot residue collected at various times after one firing. Following a general initial exponential fall-off, the rate of decrease slows at 48 hrs after firing. 

However, at the time the bulk samples were collected, NDMA was present in the air at all test sites in the tannery. The airborne data (see Table III), shows that dimethylamine (DMA) was always present. The amount of airborne NDMA was always approximately equal to 1% of the amount of airborne DMA. The apparent lack of correlation of the NDMA levels with nitrosating capacity is probably due to the relatively small variation in the measured NO levels. 

The intent of this article is to provide an overview of methodology and materials for sampling airborne pesticide spray and spray collection on surfaces by sedimentation deposition and impaction after release from field sprayers. The term pesticide will be used as a general term to represent chemicals such as herbicides, insecticides, fungicides and related products. 

Rotary sampling devices called Rotorods have also been widely used for sampling airborne sprays.These devices are similar to the rotary samplers described above, but do not use Teflon or magnesium oxide slides for spray collection. Rather, droplets... 

Vertical surfaces collect spray primarily by impaction. Plants and other entities with a vertical component will collect some material by impaction, and typically also by deposition, as discussed in the previous section. While horizontal collectors will tend to collect all or most material that falls out on to them, vertical collectors will have collection efficiencies that are more closely related to their physical characteristics, especially collector diameter. The SDTF used a-cellulose cards oriented perpendicular to the ground and strings made of cotton or Teflon in its field studies to assess spray volumes at locations above the ground. Many other researchers have used strings for assessing airborne spray volumes in drift studies. ... 

Farm worker exposure to pesticides has been studied extensively over the past 30 years.This scientitic discipline has evolved from the days when respiratory exposure of farm workers was measured using gauze dosimeters placed inside respirators to collect airborne pesticide residues to very sophisticated air sampling devices and remarkable dosimeter devices to measure dermal exposure to farm workers. ... 

---