A Study Of The Influences Of Sweeping On The Concentration Of Particulate Matter In The Indoor And Outdoor Air

Three experiments were done in a classroom and an office with DustMateenvironmental dust detector. They are dust load experiment, humidity of dustexperiment, sweeping strength experiment. In addition, ventilation dry sweepingexperiment was done in the office, and cleaning the blackboard experiment done inthe classroom. Also concentration of particulate matter was monitored before andafter the campus rode sweeping. A one-dimensional mathematical model forinstantaneous source was applied to experimental data for source strength and eddydiffusivity of fine particles, and finally a preliminary two-dimensional numericalsimulation was performed to simulate particulate matter in indoor sweeping events.The following conclusions are obtained:(1) With dust load doubling, the average mass concentration of TSP, PM10, PM2.5,PM1after sweeping respectively increased0.37,0.60,0.31and0.30times in theoffice, and respectively increased0.17,0.12,0.09and0.04times in the classroom.With the half decreasing of dust and humidity, the average mass concentration of TSP,PM10, PM2.5, PM1after sweeping respectively increased1.53,1.17,0.55and0.02times in the office, and respectively increased0.09,0.08,0.007and0.03times in theclassroom. As sweeping strength doubling the average mass concentration of TSP,PM10, PM2.5, PM1after sweeping respectively increased3.88,15.74,0.09and0.10times in the office, and respectively increased0.35,0.33,0.14and0.13times in theclassroom. It is seen that office sweeping affects the concentration of air boneparticulate matter more than classroom sweeping.(2) In the case of ventilation, the ratio of the average concentration of TSP,PM10, PM2.5and PM1during cleaning and before cleaning was1.46,1.14,1.01and1.46. In the case of without ventilation, the ratio was8.34,3.96,1.67and8.34. Fordry cleaning the blackboard, the ratio of the average concentration of TSP, PM10,PM2.5and PM1during cleaning and before cleaning was1.21,1.16,0.98and0.92. Forwet cleaning the blackboard, the ratio of the average concentration was1.00,1.00,1.00and1.01. (3) The concentrations of PM10and TSP, as well as PM2.5and PM10in thecontrol experiment in the office are linearly related The linear fitting equation are y=0.2487+39.783x (R2=0.9192) and y=0.0544+21.555x (R2=0.6404) respectively;(4) At a distance of0.5m, the ratio of average concentration of TSP, PM10,PM2.5and PM1during cleaning to before cleaning in the office is8.40,5.00,1.71,1.00times in the classroom, the ratio is7.15,3.48,1.55,1.21in the1.5m experiment. Andthe ratio is6.35,3.28,1.3,1.05in the3m experiment. The ratio of TSP and PM10inoffice and after cleaning are much higher than those for classroom, but those forPM2.5and PM1are not much different. Size of room affects TSP and PM10muchlarger than PM2.5and PM1;(5) Indoor sweeping influences the monitoring point at least7700s, urban roadsweeping about2800s, and campus road sweeping about1500s. The particleconcentration influence time of campus road sweeping is smaller than that for cityroad sweeping, and even smaller than that for indoor sweeping.(6) By applying an one-dimensional instantaneous mathematical model to theindoor sweeping data, it is obtained the source strength and eddy diffusivity for PM2.5are65.36μg/m2/s and0.00049m2/s respectively, PM10are785.44μg/m2/s and0.00053m2/s respectively, TSP are3235.18μg/m2/s and0.00065m2/s respectively.(7) Two-dimensional numerical simulation performed with the source strengthand eddy diffusivity obtained from afore-mentioned analytic model well reproducedthose of experimental data..In summary, our study shows that indoor and outdoor sweeping should ideally beimplemented with wet sweeping in a ventilation state. The experimental data and theresults of two-dimensional numerical simulation can provide a benchmark data and agood basis for future three-dimensional numerical simulation of particulate matter inthe air for sweeping events.