| Recent years,the number of construction projects has been increasing continuously in China.Fugitive dust from building construction has become one of the major sources seriously affecting ambient air quality.However,there are few reports on construction dust related research,especially the on-site measurement of fugitive dust emission and localized emission factors.In this study,the research method of emission factor based on practical experiments was improved.Systematic research including size distribution,chemical profiles and localized emission factors were carried out in typical construction sites at different stages in Shanghai.This paper attempts to provide scientific basis for formulating emission inventory,preventing and controlling local dust pollution as well as assisting other related works,which is of great significance to improve the regional ambient air quality.Typical construction sites during earthwork excavation,foundation construction and main structure period were selected as the study area.Continuous TSP on-line monitoring and synchronous observation of wind speed and wind direction were conducted at 8-24 points in the horizontal and vertical directions surrounding the sites for 15-20 days,in accordance with the principle of optimized sampling points distribution.The collected construction dust samples were resuspended and then measured by wide-range particle spectrometer.The number concentration distribution of atmospheric particulate matter at the construction sites was also measured in the range of 10nm10?m.Besides,the contents of metal elements,water soluble ions and carbon components in resuspended TSP,PM100 and PM2.5.5 samples were analyzed.The analysis of enrichment factor,potential ecological risk and human health risks were conducted to evaluate pollution extent.Moreover,based on the continuous monitoring data,the emission factors of TSP,PM100 and PM2.5.5 and the corresponding emission characteristics of chemical substances at different stages were obtained.The results indicated that:?1?Considering the fugitive dust emission and its variations in the whole construction space at a certain height,the horizontal and vertical monitoring points are arranged around the site and the real-time wind speed along with wind direction are observed.Thus the quantitive measuring process of emissions according to exposure profiling method and corresponding measurement scheme can be improved.An emission factor calculation approach based on practical measurements is obtained,combined with localized size multipliers and construction activity levels.?2?The net fugitive dust?TSP?concentration from different construction stages showed the following regularity:earthwork excavation??172.30±77.67??g/m3?>main structure??47.84±19.63??g/m3?>foundation construction??37.91±18.93??g/m3?.The vertical distribution of net concentration generally decreased with height increasing.The number concentration distribution displayed a single peak,and the average number concentration of ultrafine particles occupied?93.84±1.19?%in PM10.For the atmospheric particulate matter at construction sites,the Aigen nucleus mode accounted for the largest proportion??60.87±9.26?%?.The results indicated that the size distribution of on-site atmospheric particles could be influenced by fugitive dust.?3?In construction fugitive dust(TSP,PM100 and PM2.5)profiles,the relationship among components accounting for more than 1%showed Ca>OC>Ca2+>Fe>Al>NO3-.The descending order of five kinds of components in construction fugitive dust profiles was as follows:metal crust elements?19.70122.455%?,water soluble ions?8.69012.710%?,carbon components?3.9824.467%?,heavy metals?0.1560.161%?and other trace elements?0.0910.125%?,with Ca,Ca2+,OC,Mn and Ti as predominant element respectively.Moreover,the ions abundance decreased in an order from PM2.5,PM100 and TSP.The contributions of EC?0.3510.651%?at foundation construction and Ca?17.69219.312%?,Ca2+?8.7799.961%?,OC?4.7645.162%?at the structure process were highest.For PM100 and PM2.5,the enrichment factor of Ca was the largest.Zn,As and Pb were significantly enriched.What's more,the total potential ecological hazards of heavy metals was relatively weak,with the intensive harm shown in PM2.5.5 of main structure stage.The non-cancer risk index of As was highest,the cancer risk of individual metals followed the decreasing trend of Cr>As>Co>Ni.The potential of multiple metals was able to cause non-cancer health risk without cancer risk.?4?The fugitive dust emission factor from building construction was largest at earthwork stage,followed by the structure stage and the foundation stage,in which,the localized emission factors of TSP were1.75×10-2,3.99×10-33 and 2.53×10-3g/?m2.h?,the localized emission factors of PM100 were 1.41×10-2,3.13×10-33 and 2.19×10-3g/?m2.h?,the localized emission factors of PM2.5.5 were 7.34×10-3,1.64×10-33 and 1.10×10-3g/?m2.h?,respectively.For the emission intensity of chemicals,the metal crust elements had maximum value in the same particulate matter.And the emission intensity of five kinds of chemical substances all presented the following regularity:earthwork excavation>main structure>foundation construction in the same particulate matter,TSP>PM10>PM2.5.5 at the same stage. |
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