Boron Isotopic Analysis of Representative Atmospheric Aerosols Derived From Long-Range Transported/Local Emission on an Islet Offshore NE Taiwan

To identify pollutant origins and their potential sources from either long-range transported (LRT) or local emissions, the Boron (B) concentrations and the B isotopic compositions (δ11B) in the water-soluble fraction of aerosols were determined. These aerosols were collected from an islet offshore in northeastern Taiwan, Peng Chia Yu (PCY), a non-residential islet, from January 1998 to March 2000. This islet may be influenced by various pollutants or chemical transport during monsoon periods, but suffers minimal human perturbation locally. The B in the specimens falls to 0.3–1.63 ng m−3 during the SW monsoon seasons when compared to 0.46–2.56 ng m−3 in the NE monsoon. However, the δ11B results show no clear variations in both monsoon seasons (10.7–24.3‰), regardless of differences in air mass origin. A two end-member mixing scenario is proposed to explain our observations using the obtained δ11B and 1/[B] results. The ocean endmember is characterized by high 1/[B] and high δ11B; while other endmember is from continental endmember or anthropogenic contributions that are characterized by of 1/[B] and lowδ11B (δ11B < 10‰). Based on these chemical and isotopic results, we found aerosol emissions in northern Taiwan are characterized as low B with nearly constant δ11B, when compared with long-range transported continental endmembers derived from nearby regions. This study provides preliminary B and δ11B levels in aerosols derived from LRT/local emissions and discusses potential monsoonal effects on aerosols offshore of NE Taiwan.

Retrieval of aerosol properties from ceilometer and photometer measurements: long-term evaluation with in situ data and statistical analysis at Montsec (southern Pyrenees)

Given the need for accurate knowledge of aerosol microphysical and optical properties with height resolution, various algorithms combining vertically resolved and column-integrated aerosol information have been developed in the last years. Here we present new results of vertically resolved extensive aerosol optical properties (backscattering, scattering and extinction) and volume concentrations retrieved with the GRASP (Generalized Retrieval of Aerosol and Surface Properties) algorithm over a 3-year period. The range-corrected signal (RCS) at 1064 nm measured with a ceilometer and the aerosol optical depth (AOD) and sky radiances from a sun/sky photometer have been used as input for this algorithm. We perform a detailed evaluation of GRASP retrievals with simultaneous in situ measurements performed at the same height, at the Montsec mountaintop observatory (MSA) in the Pre-Pyrenees (northeastern Spain). This is the first long-term evaluation of various outputs of this algorithm; previous evaluations focused only on the study of aerosol volume concentration for short-term periods. In general, our results show good agreement between techniques although GRASP inversions yield higher values than those measured in situ. The statistical analysis of the extinction coefficient vertical profiles shows a clear seasonality as well as significant differences depending on the air mass origin. The observed seasonal cycle is mainly modulated by a higher development of the atmospheric boundary layer (ABL) during warm months, which favors the transport of pollutants to MSA, and higher influence of regional and North African episodes. On the other hand, in winter, MSA is frequently influenced by free-troposphere conditions and venting periods and therefore lower extinction coefficients that markedly decrease with height. This study shows the potentiality of implementing GRASP in ceilometer and lidar networks for obtaining aerosol optical properties and volume concentrations at multiple sites, which will definitely contribute to enhancing the representativeness of the aerosol vertical distribution as well as to providing useful information for satellite and global model evaluation.

Impacts of Regional-transported Biomass Burning Emissions on Chemical and Optical Properties of Carbonaceous Aerosols in Nanjing, East China

Biomass burning can significantly impact the chemical and optical properties of carbonaceous aerosols. Here, the impacts of biomass burning emissions on chemical and optical properties of carbonaceous aerosols were studied during wintertime in a megacity of Nanjing, East China. The high abundance of biomass burning tracers such as levoglucosan (lev), mannosan (man), galactosan (gal) and non-sea-salt potassium (nss-K+) was found during the studied period with the concentration ranges of 22.4–1476 ng m−3, 2.1–56.2 ng m−3, 1.4–32.2 ng m−3, and 0.2–3.8 μg m−3, respectively. Backward air mass origin analysis, potential emission sensitivity of element carbon (EC), and MODIS fire spot information indicated that the elevations of the carbonaceous aerosols were due to the transported biomass-burning aerosols from Southeast China. The characteristic mass ratio maps of lev/man and lev/nss-K+ suggested that the biomass fuels were mainly crop residuals. Furthermore, the strong correlation (p

Lagrangian simulations of the transport of young air masses to the top of the Asian monsoon anticyclone and into the tropical pipe

We have performed backward trajectory calculations and simulations with the 3-dimensional Chemical Lagrangian Model of the Stratosphere (CLaMS) for two succeeding monsoon seasons using artificial tracers of air mass origin. With these tracers we trace back the origin of young air masses (age