Insights to the formation of secondary inorganic PM_(2.5):Current knowledge and future needs

As a criteria pollutant,fine particulate matter(fine PM,i.e.PM_(2.5))adversely affects public health and environment,contributes to visibility degradation and regional haze.Atmospheric fine PM includes primary and secondary PM_(2.5).While the primary PM_(2.5) is from direct emissions,the secondary PM_(2.5) is formed in the atmosphere through photochemical reaction,condensation and other atmospheric processes.Although it is well known that ammonia(NH3)may react with acidic gas species to form secondary inorganic PM_(2.5)(iPM_(2.5))as ammonium salts,limited research has been done to quantify the impacts of NH_(3) emissions of animal feeding operations(AFOs)on the dynamics of such chemical reactions and gas-particle phases partitioning.This paper is to provide comprehensive review of existing research on AFO PM chemical speciation and on the formation of secondary iPM_(2.5) as impacted by AFO air emissions.Research gaps and future studies in characterizing AFO PM and assessing impacts of AFO air emissions on atmospheric PM are discussed.

Impact of downwind sampling location and height on inverse-Gaussian dispersion modeling: A theoretical study

In the studies of fate and transport of air emissions from animal feeding operations,Gaussian based dispersion models have been commonly used to predict downwind pollutant concentrations through forward modeling approach,or to derive emission rates and emission factors through inverse dispersion modeling approach.In the Gaussian dispersion modeling process,downwind sampling location and sampling height could generate significant impact on accuracy of the model validation,or inverse modeling results based upon field measurements.This study theoretically analyzed the impact of downwind locations and sampling height on Gaussian dispersion modeling.It was discovered that the field sampling needs to be conducted at the locations beyond the plume touching-ground distance,at a downwind distance as short as 5 m for the case scenario with zero rise of emission plume under the atmospheric stability class C,or as long as 297 m for the case scenario with 15 m rise of emission plume under the atmospheric stability class F.In order to measure the PM concentrations of the dispersion plume,the minimum sampling height at the locations within the plume touching-ground distance varied from ground level to as high as almost 14 m,whereas for the locations beyond the plume touching-ground distance,a sampling height of ground level would be acceptable.

Investigation of the Potential and Mechanism of Clove for Mitigating Airborne Particulate Matter Emission from Stationary Sources

Vegetative Barriers （VB） have the potential to mitigate air pollutants emitted from area sources, including concentrated Animal Feeding Operations （AFOs）. However, the mechanism has not been fully investigated, thereby limiting the application of vegetation systems in practice. An experimental method with repeatable and controllable conditions was developed to measure the change of Particulate Matter （PM） concentrations at upwind and downwind of VB in the wind tunnel and observe accumulated PM on leaves with Scanning Electron Microscope （SEM）, thus evaluating the ability of VB in mitigating PM emitted from AFOs. Branch-scale vegetation, clove （syzygium aromaticum） was selected because its leaves are one of the major factors affecting PM dispersion. The results show that the branch-scale barriers, as porous medium have the ability to interfere with airflow and reduce PM, which could be influenced by wind speed, particle size fraction and surface area density of clove. Moreover, clove elements could adjust to the wind and the micro structure of clove （such as the hierarchical structures of leaves） affected on the PM deposition. These results indicate that the methods developed in this study may be used to evaluate the potential of vegetation in mitigating PM from stationary sources, and some characteristics of vegetation can be further studied as bionic prototype for exploring engineering application of reducing particulates.

Seasonal variations and spatial distribution of particulate matter emissions from a ventilated laying hen house in Northeast China

With the development of concentrated animal feeding operations in China,the air pollution problem has drawn widespread public attention.Residents living near farms are suffering from the emissions of particulate matter(PM)and odors.However,scientific data on the characteristics of these emissions are limited to the establishment and evaluation of mitigation strategies in China.This study was conducted to provide fundamental information on the concentrations of PM inside and outside a typical ventilated laying hen house in northeastern China.The results showed that outdoor PM concentrations of this laying hen house did not meet the requirements of the environmental quality standard of China’s livestock and poultry farms in the two days out of six sampling days in summer,while indoor PM concentrations met the environmental requirements during this study.The indoor and outdoor PM concentrations were highly correlated in summer,and over 60%of particles indoor were emitted outside via mechanical ventilation.There were more fine particles dominated both inside and outside of the laying hen house.Besides,twelve and nine elements were measured from the PM sources inside and outside laying hen house,respectively.PM control strategies may be adjusted based on the status of exhaust fans,the ages of laying hens,atmospheric conditions,and routine house management to well reduce PM emissions and improve control efficiency.