Local PM_(10) and PM_(2.5) emission inventories from agricultural tillage and harvest in northeastern China

Mineral particles or particulate matters（PMs） emitted during agricultural activities are major recurring sources of atmospheric aerosol loading.However,precise PM inventory from agricultural tillage and harvest in agricultural regions is challenged by infrequent local emission factor（EF） measurements.To understand PM emissions from these practices in northeastern China,we measured EFs of PM_（10） and PM_（2.5） from three field operations（i.e.,tilling,planting and harvesting） in major crop production（i.e.,corn and soybean）,using portable real-time PM analyzers and weather station data.County-level PM_（10） and PM_（2.5） emissions from agricultural tillage and harvest were estimated,based on local EFs,crop areas and crop calendars.The EFs averaged（107 ± 27）,（17 ± 5） and 26 mg/m^2 for field tilling,planting and harvesting under relatively dry conditions（i.e.,soil moisture 〈15%）,respectively.The EFs of PM from field tillage and planting operations were negatively affected by topsoil moisture.The magnitude of PM_（10） and PM_（2.5） emissions from these three activities were estimated to be 35.1 and 9.8 kilotons/yr in northeastern China,respectively,of which Heilongjiang Province accounted for approximately45%.Spatiotemporal distribution showed that most PM_（10） emission occurred in April,May and October and were concentrated in the central regions of the northeastern plain,which is dominated by dryland crops.Further work is needed to estimate the contribution of agricultural dust emissions to regional air quality in northeastern China.

Temporal variability of atmospheric particulate matter and chemical composition during a growing season at an agricultural site in northeastern China

This study presents the observations of PM10 and PM2.5 concentrations at an agricultural site from April to October 2012 in Dehui city,China.Ambient air was sampled by filter-based samplers and online PM monitors.The filter samples were analyzed to determine the abundance of ionic/inorganic elements,organic carbon（OC） and elemental carbon（EC）.The daily PM10 concentrations varied significantly over the monitoring period,with an average of168 ± 63（in the range of 52-277） μg/m^3 during the land preparation/planting period（26 April-15 June）,85 ± 65（36-228） μg/m^3 during the growing season（16 June-25 September）,and 207 ±88（103-310） μg/m^3 during the harvest period（26 September-31 October）.PM2.5 accounted for44%,56%and 66%of atmospheric PM10 during these periods,respectively.The PM10 diurnal variation showed a distinct peak from 16：00 to 21：00（LST） during the growing and harvesting seasons,while a gradual increase throughout the daytime until 17：00 was observed during tilling season.Mineral dust elements（Al,Ca,Fe,and Mg） dominated the PM10 chemical composition during the tilling season;OC,NO3^-,SO4^（2-） and NH4~＋ during the growing season;and carbonaceous species（i.e.,OC and EC） during the harvesting season.Our results indicate that the soil particles emitted by farm tillage and organic matter released from straw burning are the two most significant sources of PM10 emissions contributing to the recurring high pollution events in this region.Therefore,development of agricultural PM inventories from soil tillage and straw burning is prioritized to support air quality modeling.