Strong sesquiterpene emissions from Amazonian soils.

The Amazon rainforest is the world's largest source of reactive volatile isoprenoids to the atmosphere. It is generally assumed that these emissions are products of photosynthetically driven secondary metabolism and released from the rainforest canopy from where they influence the oxidative capacity of the atmosphere. However, recent measurements indicate that further sources of volatiles are present. Here we show that soil microorganisms are a strong, unaccounted source of highly reactive and previously unreported sesquiterpenes (C15H24; SQT). The emission rate and chemical speciation of soil SQTs were determined as a function of soil moisture, oxygen, and rRNA transcript abundance in the laboratory. Based on these results, a model was developed to predict soil-atmosphere SQT fluxes. It was found SQT emissions from a Terra Firme soil in the dry season were in comparable magnitude to current global model canopy emissions, establishing an important ecological connection between soil microbes and atmospherically relevant SQTs.

Impact on short-lived climate forcers increases projected warming due to deforestation.

The climate impact of deforestation depends on the relative strength of several biogeochemical and biogeophysical effects. In addition to affecting the exchange of carbon dioxide (CO2) and moisture with the atmosphere and surface albedo, vegetation emits biogenic volatile organic compounds (BVOCs) that alter the formation of short-lived climate forcers (SLCFs), which include aerosol, ozone and methane. Here we show that a scenario of complete global deforestation results in a net positive radiative forcing (RF; 0.12 W m-2) from SLCFs, with the negative RF from decreases in ozone and methane concentrations partially offsetting the positive aerosol RF. Combining RFs due to CO2, surface albedo and SLCFs suggests that global deforestation could cause 0.8 K warming after 100 years, with SLCFs contributing 8% of the effect. However, deforestation as projected by the RCP8.5 scenario leads to zero net RF from SLCF, primarily due to nonlinearities in the aerosol indirect effect.

Primary and secondary organics in the tropical Amazonian rainforest aerosols: chiral analysis of 2-methyltetraols.

This work presents the application of a new method to facilitate the distinction between biologically produced (primary) and atmospherically produced (secondary) organic compounds in ambient aerosols based on their chirality. The compounds chosen for this analysis were the stereomers of 2-methyltetraols, (2R,3S)- and (2S,3R)-methylerythritol, (l- and d-form, respectively), and (2S,3S)- and (2R,3R)-methylthreitol (l- and d-form), shown previously to display some enantiomeric excesses in atmospheric aerosols, thus to have at least a partial biological origin. In this work PM10 aerosol fractions were collected in a remote tropical rainforest environment near Manaus, Brazil, between June 2008 and June 2009 and analysed. Both 2-methylerythritol and 2-methylthreitol displayed a net excess of one enantiomer (either the l- or the d-form) in 60 to 72% of these samples. These net enantiomeric excesses corresponded to compounds entirely biological but accounted for only about 5% of the total 2-methyltetrol mass in all the samples. Further analysis showed that, in addition, a large mass of the racemic fractions (equal mixtures of d- and l-forms) was also biological. Estimating the contribution of secondary reactions from the isomeric ratios measured in the samples (=ratios 2-methylthreitol over 2-methylerythritol), the mass fraction of secondary methyltetrols in these samples was estimated to a maximum of 31% and their primary fraction to a minimum of 69%. Such large primary fractions could have been expected in PM10 aerosols, largely influenced by biological emissions, and would now need to be investigated in finer aerosols. This work demonstrates the effectiveness of chiral and isomeric analyses as the first direct tool to assess the primary and secondary fractions of organic aerosols.

Rainforest aerosols as biogenic nuclei of clouds and precipitation in the Amazon.

The Amazon is one of the few continental regions where atmospheric aerosol particles and their effects on climate are not dominated by anthropogenic sources. During the wet season, the ambient conditions approach those of the pristine pre-industrial era. We show that the fine submicrometer particles accounting for most cloud condensation nuclei are predominantly composed of secondary organic material formed by oxidation of gaseous biogenic precursors. Supermicrometer particles, which are relevant as ice nuclei, consist mostly of primary biological material directly released from rainforest biota. The Amazon Basin appears to be a biogeochemical reactor, in which the biosphere and atmospheric photochemistry produce nuclei for clouds and precipitation sustaining the hydrological cycle. The prevailing regime of aerosol-cloud interactions in this natural environment is distinctly different from polluted regions.

New analytical method for the determination of levoglucosan, polyhydroxy compounds, and 2-methylerythritol and its application to smoke and rainwater samples.

Biomass burning is an important source of smoke aerosol particles, which contain water-soluble inorganic and organic species, and thus have a great potential of affecting cloud formation, precipitation, and climate on global and regional scales. In this study, we have developed a new chromatographic method for the determination of levoglucosan (a specific tracer for biomass burning particles), related polyhydroxy compounds, and 2-methylerythritol (recently identified as isoprene oxidation product in fine aerosols in the Amazon) in smoke and in rainwater samples. The new method is based on water extraction and utilizes ion-exclusion high-performance liquid chromatography (IEC-HPLC) separation and spectroscopic detection at 194 nm. The new method allows the analysis of wet samples, such as rainwater samples. In addition, aliquots of the same extracts can be used for further analyses, such as ion chromatography. The overall method uncertainty for sample analysis is 15%. The method was applied to the analysis of high-volume and size-segregated smoke samples and to rainwater samples, all collected during and following the deforestation fires season in Rondonia, Brazil. From the analysis of size-segregated samples, it is evident that levoglucosan is a primary vegetation combustion product, emitted mostly in the 0.175-1 microm size bins. Levoglucosan concentrations decrease below the detection limit atthe end of the deforestation fires period, implying that it is not present in significant amounts in background Amazon forest aerosols. The ratio of daytime levoglucosan concentration to particulate matter (PM) concentration was about half the nighttime ratio. This observation is rationalized by the prevalence of flaming combustion during day as opposed to smoldering combustion during night. This work broadens the speciation possibilities

Smoking rain clouds over the Amazon.

Heavy smoke from forest fires in the Amazon was observed to reduce cloud droplet size and so delay the onset of precipitation from 1.5 kilometers above cloud base in pristine clouds to more than 5 kilometers in polluted clouds and more than 7 kilometers in pyro-clouds. Suppression of low-level rainout and aerosol washout allows transport of water and smoke to upper levels, where the clouds appear "smoking" as they detrain much of the pollution. Elevating the onset of precipitation allows invigoration of the updrafts, causing intense thunderstorms, large hail, and greater likelihood for overshooting cloud tops into the stratosphere. There, detrained pollutants and water vapor would have profound radiative impacts on the climate system. The invigorated storms release the latent heat higher in the atmosphere. This should substantially affect the regional and global circulation systems. Together, these processes affect the water cycle, the pollution burden of the atmosphere, and the dynamics of atmospheric circulation.

Characterization of novel di- and tricarboxylic acids in fine tropical aerosols.

Three unknown di- and tricarboxylic acids were characterized in the fine size fraction of aerosols which were collected during the wet season in the Amazon basin (Rondonia, Brazil). For the structural characterization of the methyl esters of these unknown compounds, mass spectrometry with electron ionization (EI) and tandem mass spectral techniques combined with gas chromatographic (GC) separation were employed. Fragment and parent ion spectra were recorded during elution of the GC peaks by linked scanning of the B and E sectors in combination with high-energy collision-induced dissociation. The fragmentation patterns of significant ions in the first-order EI spectra were also obtained for nonanedioic acid, which was examined as a model compound. The compounds were tentatively identified as 4-acetyloxyheptanedioic acid and cis and trans isomers of 5-hexene-1,1,6-tricarboxylic acid. Since there were indications of biomass burning during the aerosol sampling the di- and tricarboxylic acids characterized in the present work could be markers for biomass burning. Furthermore, the characterization of di- and tricarboxylic acids in the fine size fraction of atmospheric aerosols may be important for assessing the effects of organic aerosols in cloud formation.

Acute effects of inhalable particles on the frog palate mucociliary epithelium.

This work was designed to evaluate the toxicity of inhalable particles [less than/equal to] 10 microm in aerodynamic diameter (PM(10)) collected from the urban air in São Paulo, Brazil, to the mucociliary apparatus using the frog palate preparation. Seven groups of frog palates were immersed in different concentrations of PM(10) diluted in Ringer's solution during 120 min: 0 (control, n = 31); 50 (n = 10); 100 (n = 9); 500 (n = 28); 1,000 (n = 10); 5,000 (n = 11); and 10,000 microg/m(3) (n = 10). Mucociliary transport and transepithelial potential difference were determined at 0, 30, 60, and 120 min exposure. Additional groups (control and 500 microg/m(3)) were studied by means of morphometric analyses (quantification of the amount of intraepithelial and surface mucins), measurement of cilia beat frequency, and quantification of total glutathione. Mucociliary transport and transepithelial potential difference were significantly decreased at higher concentrations of PM(10) (p = 0.03 and p = 0.02, respectively). Exposure to PM(10) also elicited a significant decrease of total glutathione (p = 0. 003) and depletion of neutral intraepithelial mucins (p = 0.0461). These results show that PM(10) can promote significant alterations in ciliated epithelium in vitro.

Effects of heavy industrial pollution on respiratory function in the children of Cubatao, Brazil: a preliminary report.

Under a cooperative agreement between New York University and the Environmental Protection Agency, and in collaboration with the University of Sao Paulo (USP), a study is ongoing in Cubatao, Brazil, to try to establish exposure-response relationships on the impact of specific industrial effluents on respiratory function in school-age children. Cubatao, located on the coast about 44 km from the city of Sao Paulo, is surrounded by U-shaped mountains (approximately 800 m) covered with subtropical forests. Its area is approximately 160 km2, and it has a population of approximately 90,000. The geography is such that it causes a consistent diurnal land-sea breeze pattern and the opposite during the night, with low dispersion of the air pollutants. In a small area (approximately 40 km2) against the mountains there is a concentration of over 20 large plants: oil refinery; iron and steel mill; fertilizer, cement, and gypsum production; coke kilns; and chemical, paint, and many other ancillary plants. During the 1988 school year, March through June, August through November, 600 six-year-old children, attending six different kindergarten schools, underwent monthly spirometry tests. Because the children live within a 500 m radius of their school, pollution monitors were located on each of the six schools. Particles were collected using dichotomous stacked filter units placed on 20 m towers to reduce the influence of dust from unpaved roads. The units use different pore size filters for coarse, 2 to 10 microns, and fine particles, (dp) less than 2 microns, and took separate samples for day and nighttime.(ABSTRACT TRUNCATED AT 250 WORDS)