Analyzer, cotton dust

The prototype cotton-dust analyzer used in the initial study was designed to measure dust smaller than 100 pm, whereas a vertical elutriator in a card room measures only the dust that is smaller than about 15 pm. Differences in particle size distributions of dust from various types of cotton would likely affect the relationship between the two dust measurements. Therefore, we deemed it necessary to investigate the use of sizing screens with smaller openings i.e., openings whose size approximated the maximum size of particles collected by a vertical elutriator. The purpose of this report is to describe additional modifications to the cotton-dust analyzer and to present data on the performance of the machine when 17-, 50-, and 100-pm sizing screens were used. 

A new model of the cotton-dust analyzer was constructed to overcome some of the shortcomings of the prototype. It was more compact and easier to operate than the original machine. The sizing-screen arrangement in the new model was more accessible than in the original machine to facilitate the evaluation of various screen sizes. It was also equipped with an air regulator to maintain a constant air pressure on the spray bar for Improved airflow characteristics. Also, a high-efficiency particulate air... 

An aluminum enclosure housed the working components of the cotton-dust analyzer. The upper section of the enclosure, which was hinged to the lower section, contained the HEPA filter, the spray bar assembly, and the top, hold-down screen for the lint batt. The botton section housed the sizing screen, filter support, fan, and the electrical and pneumatic controls. The entire enclosure was 60 cm wide, 46 cm deep, and 72 cm tall. 

Collection Filters. The cotton-dust analyzer requires 20.3-cm X 25.4-cm glass-fiber filters for collection of dust particles. These filters are binder-free and specially designed for gravimetric analysis of air pollutants. The filters are rated at 99.9%... 

Figure 1. Schematic of cotton dust analyzer. 1, high efficiency particulate air filter 2, reversing drive 3, chain drive 4, spray bar 5, top screen 6, lint batt 7, sizing screen 8, glass fiber filter 9, high-pressure fan 10, pressure gages 11, compressed-air entrance 12, prefiiter/watertrap 13, air-pressure reguiator 14, solenoid vaive 15, secondary air filter 16, hose to spray bar.

Figure 2. Cotton dust analyzer showing top holding screen, sizing screen, and...

Figure 3. Schematic of electrical circuit for cotton dust analyzer.

After the filters were exposed in the cotton-dust analyzer, they were conditioned for at least 8 h then rewelghed to the nearest 0.01 mg. 

Two approaches were evaluated for increasing the size of the lint samples. In one approach, we simply used six speclments of 3.33 g each to comprise a 20-g lint sample. In the other approach, we doubled the thickness and weight of the specimens and used three specimens of 6.67 g each. We found that the cotton-dust analyzer technique was sensitive to variations in the thickness and weight of the batt. Doubling the batt weight and thickness reduced by about 50% the amount of dust extracted from a 20-g lint sample. Therefore, we decided to use six specimens... 

Repeat steps 1 through 6 to obtain three more specl-ments from the same sample of lint. The six specimens formed by the above procedures will comprise a single, 20-g lint sample for exposure in the cotton-dust analyzer. 

The following procedures were used to operate the new model of the cotton-dust analyzer ... 

Additional tests are underway to more accurately determine relationships between data from the cotton-dust analyzer and data on card-room dust levels as measured with a vertical elutrlator. At present, the Information available as a basis for comparing the two dust-measurement techniques Is limited. The comparisons shown In Figure 4 were based on several analyses of samples from six cotton lots. Although limited In scope, the data Indicate the likelihood that the correlation between the two measurement techniques will be reasonably good. 

Figure 4. Card room dust levels vs. dust content measurements by a cotton dust analyzer (17-iim sizing screen).

Chromatography and Electrophoresis of Antigens. Cotton dust (20-30 mg) was dissolved in water and passed through a small column (30 x 1.5 cm id) packed with 3 g of Sephadex G-75 that had been preswelled in water. Chromatograms were obtained with an LKB Uvicord ultraviolet monitor and a chopper bar recorder. Volumes of 5 ml each were collected in test tubes with an automatic fraction collector. Two components were detected at 250 nm. Samples of 10 mg were analyzed by disc gel electrophoresis according to procedures described by Davis (36), and Zacharius (37). 

Samples of dust from each of the two dust sources were collected for testing. They were dispersed in an electrolyte and analyzed for size on a volume basis. Model card dust had a mass mean diameter of 3.6 with a geometric standard deviation of 1.6. The cotton dust released by tapping the loaded filter varied from 4.5 to 6.7 urn mass mean diameter with a geometric standard deviation of about 2. All test concentrations were in the range of 0.5 to 1.5 mg/m, which are typical of cotton mill fine dust concentration. 

The results of this study showed that uncontrollable variations in wind direction and velocity during sampling adversely affected the reliability of the measurements and made the data difficult to analyze. It was also found that the airborne dust burden by winds from unpaved approach roads and cotton-trailer parking areas often overshadowed that emitted by the gins. It soon became apparent that the principal Impact of gins in Mississippi on ambient air quality was principally that of a nuisance. 

Additional measurements were made with the 17-)im sizing screen to obtain more information on the variability of our measurement techniques. Eight lint samples from a single source of cotton were analyzed by the procedures outlined previously. The dust levels obtained in this test were 11.7, 12.1, 13.5, 11.8, 10.8, 11.2, 10.9, and 9.7 mg, respectively, per 20 g of lint. The mean and standard deviation of these measurements were 11.5 and 1.1, respectively. The estimated standard error of the mean was 0.42, and the interval from 10.5 to 12.5 represented a 95% confidence interval for the lot mean. 

Monitoring dust and trash concentrations in cotton by a simple, rapid, on-line process analyzer with feedback control could provide ginners an incentive to produce cleaner cotton and thus improved rarketability of the coimiodity. Based on the dust and trash in the baled cotton, it may also be possible to predict airborne dust levels in textile milling. Bales could be automatically blended to minimize mean dust level in the workplace. (In... 

A 100 watt ultrasonic bath was used to detach dust from the fiber by wet assay. A Shirley Analyzer (9) was used to remove trash from cotton. In brief, the analyzer contains two rotating cyclinders with saw teeth to mechanically remove the trash from cotton. The Continuous Aerosol Monitoring (CAM) analyzer developed by ppm, Inc. (10) was used to measure airborne dust. 

A survey of 486 textile workers, from three cotton mills and one man-made fibers plant, was completed by investigators of Tulane Medical School (32). Measurements of dust, ° respiratory symptoms by the Schilling questionnaire and of ventilatory function were analyzed for correlation. The results indicated... 

In the other study. X-ray fluorescence spectroscopy was used to analyze trace element concentrations by observing dusts on 37 ram diameter cellulose acetate filters (20). Twenty-three elutriator and twenty-three area samples from 10 different bales of cotton were analyzed. The average fraction of total dust accounted for by the elements analyzed was 14.4% amd 7.6% for vertical elutriator and area samples, respectively. Although the variation in absolute quantity of atn element was high, the relative abundance of an element was consistent for measurements within a bale. Averaged over all the samples analyzed, calcium was the most abundant element detected (3.6%), followed by silicon (2.9%), potassium (2.7%), iron (1.1%), aluminum (1.1%), sulfur (1.0%), chlorine (0.8%) and phosphorous (0.6%). Other elements detected in smaller aunounts included titanium, manganese, nickel, copper, zinc, bromine, rubidium, strontium, barium, mercury amd lead. 

Wesley and Wall (4 ) and Brown and coworkers (18) collected dust samples at five cotton gins with high volume air samplers at three locations in the gin. The dust was removed from the filters in the seime manner as the weave room dusts discussed above. The average ash content was 32.9%. X-ray fluorescence analyses showed that silicon was the most abundant element detected (7.69%), followed by potassium (1.82%), aluminum (1.46%), calcium (1.15%), magnesium (1.05%), phosphorous (0.52%), iron (0.45%), sulphur (0.33%) and chlorine (0.16%). The total dust was separated into a "respirable fraction" (28) by the sonic sifting procedure and analyzed as above. The ash content of the respirable fraction of gin dusts increased to 46.0%. Only the... 

The spiked samples were incubated in an oven at 85°F, in dark, and in open system cotton plugs were used to prevent dust from entering the flasks. The experiment was set up for 90 days. The sampling times were 0.04 0.67 1.67 4 10 or 12 20 32 61 and 93 days from the initiation of the experiment. Three replicates were analyzed at each time interval for the test compounds. Soil moisture was maintained at 14 percent and 22 percent by addition of organics-free water and was verified twice a week during the experiment. Other details can be found in Reference 21. 

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