The discovery that negatively charged aggregates of C60 fullerene (nC60) are stable in water has raised concerns regarding the potential environmental and health effects of these aggregates. In this work, we show that nC60 aggregates produced by extended mixing in the presence of environmentally relevant carboxylic acids (acetic acid, tartaric acid, citric acid) have surface charge and morphologic properties that differ from those produced by extended mixing in water alone. In general, aggregates formed in the presence of these acids have a more negative surface charge and are more homogeneous than those produced in water alone. Carboxylic acid identity, solution pH, and sodium ion concentration, which are all intricately coupled, play an important role in setting the measured surface charge. Comparisons between particle sizes determined by analysis of TEM images and those obtained by dynamic light scattering (DLS) indicate that DLS results require careful evaluation when used to describe nC60 aggregates. The effects of carboxylic acids on the formation of nC60 aggregates are discussed.

Canopy leaf area index (LAI) is an important structural parameter of the vegetation controlling pollutant uptake by terrestrial ecosystems. This paper presents a computationally efficient algorithm for retrieval of vegetation LAI and canopy clumping factor from satellite data using observed Simple Ratios (SR) of near-infrared to red reflectance. The method employs numerical inversion of a physics-based analytical canopy radiative transfer model that simulates the bi-directional reflectance distribution function (BRDF). The algorithm is independent of ecosystem type. The method is applied to 1-km resolution AVHRR satellite images to retrieve a geo-referenced data set of monthly LAI values for the conterminous USA. Satellite-based LAI estimates are compared against independent ground LAI measurements over a range of ecosystem types. Verification results suggest that the new algorithm represents a viable approach to LAI retrieval at continental scale, and can facilitate spatially explicit studies of regional pollutant deposition and trace gas exchange. The paper presents a physics-based algorithm for retrieval of vegetation LAI and canopy-clumping factor from satellite data to assist research of pollutant deposition and trace-gas exchange. The method is employed to derive a monthly LAI dataset for the conterminous USA and verified at a continental scale.

During the last decades, carbonaceous aerosol extinctions such as black carbon and organic carbon extinctions exhibit an increasing trend across the globe. Measurements of carbonaceous aerosol in Jordan were done using satellite data during the period 2007 to 2018. These measurements were done in four locations of Jordan - Irbid in the north, Amman and Az-Zarqa in the middle, and Ma’an in the south. Black carbon extinction in Jordan increased slightly (slope = 0.0001) during this period, while organic carbon extinction increased slightly (slope = (0.7 – 10) x10-5) in three locations and decreased slightly in one location (Irbid location (slope = -2x10-5)). Organic carbon extinction measurements were greater than black carbon extinction measurements in all locations with varying ratios depending on the location of the measurements. Black carbon and organic carbon scattering measurements have the same behavior as extinction, with larger values in the north and smaller values in the south. Scattering values of organic carbon are larger than black carbon scattering values. Scattering values of organic carbon increased slightly in all locations (slope = 0.0001) while scattering values of black carbon decreased in three locations (Irbid, Amman, and Ma’an) and increased in one location (Az-Zarqa). Column mass density and surface mass concentration measurements show that organic carbon had larger values than black carbon in all locations besides that both organic carbon and black carbon had values decreasing when we go from north to south.