Comparison of methods for measurement of dust deposition in South African mining sectors

[摘要] Dust particles in the atmosphere are a key cause of nuisance, health and otherenvironmental problems. The mining sector is a major source of airborne particulatematter caused by operations like terrain clearing, drilling, blasting, tipping and loadingand the passage of vehicles on unpaved roads. The nuisance effect of airborne dustcan be measured by using dust buckets and/or directional dust deposition gauges. Dustbuckets are used to determine vertical dust deposition rates and directional dustdeposition gauges are used to determine the direction of the sources.Traditionally the measurement of the vertical flux of dust, or dust deposition has beenused as to indicate the nuisance caused by coarse suspended particulate matter.Several countries have produced standards for permissible dust deposition rates.Although alternative deposition measurement methods have been proposed, ASTMD1739 has remained the method most often used in the South African mining andindustrial sectors to measure dust deposition. In addition, a number of non-standarddirectional dust deposition gauges have been used.SANS 1929:2005 (South African National Standards, 2005) prescribes the use of ASTMD1739:98 for measuring dust deposition. However, for historical reasons the previousversion, ASTM D1739:70 (re-approved as ASTM D1739:82) is still widely used and inthe recently promulgated South African Dust Management regulations the use of thisversion is prescribed. In order to determine the difference in the results obtained by thetwo versions, ASTM D1739:82 and ASTM D1739:98 were used to measure dustdeposition levels arising from a coal mining operation in the Mpumalanga Province anda gold mining operation in North-West Province.In order to determine whether a correlation exists between vertical dust flux (dustdeposition) and horizontal dust flux, standard directional horizontal dust flux gaugesaccording to BS 1747 part 5 were also set up at both sites. The measurement of dustdeposition using three dust deposition gauges (i.e. ASTM D1739:82, ASTM D1739:98and BS 1747 part 5, directional dust deposition gauges) was undertaken monthly over aperiod of fourteen (14) months at the two sites.The findings of the study indicate that the dust deposition rates for an opencast coalmine are generally higher than the dust deposition rates for an underground gold mine.ASTM D1739:98 was shown to be a more efficient dust deposition collection methodthan ASTM D1739:82, with the ratio between the mean values slightly more than 2. Theaddition of water to the dust bucket does not make a statistically significant difference toretention of dust in the bucket. There is a weak correlation between results for thevertical dust gauges and horizontal dust flux.It is recommended that the South African mining sector continue dust depositionmonitoring and reporting using the more recent version of ASTM D1739, as highdeposition levels may indicate a potential health impact from PM10 thoracic dust.

[发布机构] University of Pretoria