[1] The aerosol characterization experiment performed within the Large-Scale BiosphereAtmosphere Experiment in Amazonia-Smoke, Aerosols, Clouds, Rainfall and Climate (LBA-SMOCC) field experiment carried out in Rondônia, Brazil, in the period from September to November 2002 provides a unique data set of size-resolved chemical composition of boundary layer aerosol over the Amazon Basin from the intense biomassburning period to the onset of the wet season. Three main periods were clearly distinguished on the basis of the PM 10 concentration trend during the experiment: (1) dry period, with average PM 10 well above 50 mg m À3 ; (2) transition period, during which the 24-hour-averaged PM 10 never exceeded 40 mg m À3 and never dropped below 10 mg m À3 ; (3) and wet period, characterized by 48-hour-averaged concentrations of PM 10 below 12 mg m À3 and sometimes as low as 2 mg m À3 . The trend of PM 10 reflects that of CO concentration and can be directly linked to the decreasing intensity of the biomass-burning activities from September through November, because of the progressive onset of the wet season. Two prominent aerosol modes, in the submicron and supermicron size ranges, were detected throughout the experiment. Dry period size distributions are dominated by the fine mode, while the fine and coarse modes show almost the same concentrations during the wet period. The supermicron fraction of the aerosol is composed mainly of primary particles of crustal or biological origin, whereas submicron particles are produced in high concentrations only during the biomass-burning periods and are mainly composed of organic material, mostly water-soluble, and $10% of soluble inorganic salts, with sulphate as the major anion. Size-resolved average aerosol chemical compositions are reported for the dry, transition, and wet periods. However, significant variations in the aerosol composition and concentrations were observed within each period, which can be classified into two categories: (1) diurnal oscillations, caused by the diurnal cycle of the boundary layer and the different combustion phase active during day (flaming) or night (smouldering); and (2) day-to-day variations, due to alternating phases of relatively wet and dry conditions. In a second part of the study, three subperiods representative of the JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 112, D01201, doi:10

There has been a significant increase in use of wood pellets in residential and commercial scale boiler systems within New York State, such an increase will lead to increased storage of bulk pellets in homes and buildings. Serious accidents in Europe have been reported over the past decade in which high concentrations of carbon monoxide (CO) have been found in bulk pellet storage bins. Thus, additional exposure data for CO in pellet bin storage areas are needed to assess the potential hazards. Using calibrated CO sensors, continuous CO measurements were made from the spring 2013 to spring 2014 in a number of wood pellet storage bins in New York State. The CO sensors, in some cases, in conjunction with sensors for CO 2 , O 2 , relative humidity, and temperature, were installed in a residential basement, an external storage silo, and several boiler room storage areas in schools and a museum. Peak concentrations in these pellet storage locations ranged from 14 ppm in the basement residence to 155 ppm inside the storage silo at a school. One-hour CO concentrations in the boiler rooms were typically 10−15 ppm. The measured concentrations were compared to regulatory standards of 50 ppm and recommended guidelines of 35 and 9 ppm for work and nonworking environments, respectively. The concentrations at the three locations in the middle school never exceeded the 35 ppm guideline. At the museum, the CO concentrations after pellets delivery did reach a maximum of 55 ppm for a 1-h average. However, high concentrations remained for only 4 days due to natural ventilation in this storage location. Storage areas for pellets must be considered confined spaces and require appropriate entry procedures. As the biomass heating with pellets becomes more prevalent, improved designs for storage bins must be considered to minimize the risk of exposure to CO to building occupants.

Wood pellet storage safety is an important aspect for implementing woody biomass as a renewable energy source. When wood pellets are stored indoors in large quantities (tons) in poorly ventilated spaces in buildings, such as in basements, off-gassing of volatile organic compounds (VOCs) can significantly affect indoor air quality. To determine the emission rates and potential impact of VOC emissions, a series of laboratory and field measurements were conducted using softwood, hardwood, and blended wood pellets manufactured in New York. Evacuated canisters were used to collect air samples from the headspace of drums containing pellets and then in basements and pellet storage areas of homes and small businesses. Multiple peaks were identified during GC/MS and GC/FID analysis, and four primary VOCs were characterized and quantified: methanol, pentane, pentanal, and hexanal. Laboratory results show that total VOCs (TVOCs) concentrations for softwood (SW) were statistically (p < 0.02) higher than blended or hardwood (HW) (SW: 412 ± 25; blended: 203 ± 4; HW: 99 ± 8, ppb). The emission rate from HW was the fastest, followed by blended and SW, respectively. Emissions rates were found to range from 10−1 to 10−5 units, depending upon environmental factors. Field measurements resulted in airborne concentrations ranging from 67 ± 8 to 5000 ± 3000 ppb of TVOCs and 12 to 1500 ppb of aldehydes, with higher concentrations found in a basement with a large fabric bag storage unit after fresh pellet delivery and lower concentrations for aged pellets. These results suggest that large fabric bag storage units resulted in a substantial release of VOCs into the building air. Occupants of the buildings tested discussed concerns about odor and sensory irritation when new pellets were delivered. The sensory response was likely due to the aldehydes.

There is a potential hazard associated with bulk storage of wood pellets because they have been shown to off-gas carbon monoxide (CO). The risk to building occupants from the emission of and exposure to CO from stored pellets has not yet been fully studied. The present study was designed to measure the emission rates from wood pellets and develop a model to predict the CO emission rate. The 20 gallon steel drums were filled to approximately 50% of their volume with wood pellets and CO, and oxygen (O 2 ), carbon dioxide (CO 2 ), temperature (T), and relative humidity (RH) were measured as a function of time.A variety of conditions were tested including the type of wood, age of the pellets, volume of the headspace, humidity, surface/ volume ratio, and temperature. An improved kinetic model was developed to predict the CO emission rate. The model assumes that the reaction generating CO is surface-area-limited. The measurements were well-fit by the mathematical model (R 2 in the range of 0.93−0.99), suggesting that the model is a good predictor of the CO emission rates. ■ INTRODUCTIONWood pellets, a renewable biomass solid fuel, are becoming a more attractive source of energy for heating and power in the U.S., Canada, and Europe as oil prices rise and/or the need to reduce greenhouse gases increases the use of renewable energy. 1,2 Wood pellets are made from compacted sawdust from cut trees or wastes from sawmilling and other wood product manufacture. Pellets are formed by extruding the sawdust through a die, resulting in a typical size of 12−20 mm long and 6 mm diameter cylinder. They have a low moisture content (4.5−8.0%) and a low ash content (0.5−0.8) that allows them to be burned with a very high combustion efficiency, resulting in gross calorific values of the order of 8100−8470 Btu/lb. 3 In New York State, a series of demonstration projects has been initiated to introduce highefficiency, low-emission wood pellet boilers based on European designs into homes, schools, and commercial buildings. 2,4 After wood pellets are manufactured, they are stored in pellet bins, shipping vessels, boxcars, or at the owner's facility. While in storage, pellets emit a variety of gases, including carbon monoxide (CO), carbon dioxide (CO 2 ), methane (CH 4 ), and volatile organic compounds (VOCs), that can result in CO concentrations and depleted O 2 that can reach toxic concentrations. 5−8 A recent study has shown that concentrations of CO in domestic and commercial-scale pellet bins can exceed guidance and regulatory limits for CO exposure. 9 These emissions have also been observed from other hydrocarbon products. 10,11 The amount of emitted gases will depend upon the temperature (T), relative humidity (RH), headspace (HS) volume, surface of pellets available, mass, and type of wood. 12−17 The proposed mechanism of CO emission has been studied by Levitt et al.,10 observing that organic matter, stored at room temperature, particularly in the presence of air and light, emitted small amounts of CO and the emission rate increases ...

The concentrations of the water-soluble inorganic aerosol species, ammonium (NH ; when filter-based samplers measured on average 40-90% less than the WAD/SJAC. The differences were not due to consistent systematic biases of the analytical techniques, but were apparently a result of prevailing environmental conditions and different sampling procedures. For the transition period and wet season, the significance of our results is reduced by a low number of data points. We argue that the observed differences are mainly attributable to (a) positive and negative filter sampling artifacts, (b) presence of organic compounds and organosulfates on filter substrates, and (c) a SJAC sampling efficiency of less than 100%.