The sizes of particulate sulfate and nitrate in the atmosphere--a review

Source Apportionment of Aerosol at a Coastal Site and Relationships with Precipitation Chemistry: A Case Study over the Southeast United States

This study focuses on the long-term aerosol and precipitation chemistry measurements from colocated monitoring sites in Southern Florida between 2013 and 2018. A positive matrix factorization (PMF) model identified six potential emission sources impacting the study area. The PMF model solution yielded the following source concentration profiles: (i) combustion; (ii) fresh sea salt; (iii) aged sea salt; (iv) secondary sulfate; (v) shipping emissions; and (vi) dust. Based on these results, concentration-weighted trajectory maps were developed to identify sources contributing to the PMF factors. Monthly mean precipitation pH values ranged from 4.98 to 5.58, being positively related to crustal species and negatively related to SO4 2-. Sea salt dominated wet deposition volume-weighted concentrations year-round without much variability in its mass fraction in contrast to stronger seasonal changes in PM2.5 composition where fresh sea salt was far less influential. The highest mean annual deposition fluxes were attributed to Cl-, NO3 -, SO4 2-, and Na+ between April and October. Nitrate is strongly correlated with dust constituents (unlike sea salt) in precipitation samples, indicative of efficient partitioning to dust. Interrelationships between precipitation chemistry and aerosol species based on long-term surface data provide insight into aerosol-cloud-precipitation interactions.

Mass concentration and elemental composition of PM10 in classrooms

OBJECTIVES

To investigate the sources of high concentrations of particles of < 10 microns diameter (PM10) in classrooms, observed in a previous study on childhood exposure to PM10, and to study the correlation between classroom and outdoor concentrations of mass and elements of PM10.

METHODS

Measurements of PM10 were conducted in two schools and outdoors in Amsterdam, the Netherlands. Averaging time was 24 hours for the outdoor measurements and both 8 hours (school time) and 24 hours for the classroom measurements. Analysis by x ray fluorescence was used to measure the elemental composition of 55 samples from the 11 days when measurements were conducted simultaneously in both classrooms and outdoors.

RESULTS

For most elements, classroom concentrations were considerably higher than outdoor concentrations, especially during school hours. The highest classroom/outdoor ratios were found for the elements from soils Si, Ca, and Ti. The only measured elements that were not increased were S, Br, Pb, and Cl, which are dominated by non-crustal sources. For S, Br, and Pb, which are generally associated with particles < 1 micron, significant correlations between classroom and outdoor concentrations and between the two classrooms were found. The other elements generally had low correlations.

CONCLUSIONS

The results show that the high PM10 concentrations found in our classrooms are probably due to resuspension of coarse particles or suspension of soil material. Due to these excess coarse particles, the correlation between classroom and outdoor concentrations is lower for elements associated with coarse particles than for elements associated with fine particles. As the general composition of PM10 in classrooms differs from the composition of PM10 in ambient air, the high PM10 mass concentrations in classrooms can probably not be directly compared with ambient air quality guidelines.