Seasonal and diurnal characteristics of water soluble inorganic compounds in the gas and aerosol phase in the Zurich area

Gas and aerosol samples were taken using a wet effluent diffusion denuder/aerosol collector (WEDD/AC) coupled to ion chromatography (IC) in the city of Zurich, Switzerland from August to September 2002 and in March 2003. Major water soluble inorganic ions; nitrate, sulfate, and nitrite were analyzed online with a time resolution of two hours for the gas and aerosol phase. The fraction of water soluble inorganic anions in PM10 varied from 15% in August to about 38% in March. Seasonal and diurnal variations of nitrate in the gas and aerosol phase were observed with more than 50% of the total nitrate in the gas phase during August and more than 80% of nitrate in the aerosol phase during March exceeding the concentration of sulfate by a factor of 2. Aerosol sulfate, on the other hand, did not show significant variability with season. However, in the gas phase, the SO₂ concentration was 6.5 times higher in winter than in summer. Nitrous acid (HONO) also showed a diurnal variation in both the gas and aerosol phase with the lowest concentration (0.2–0.6 µg/m³) in the afternoon. The primary pollutants, NO, CO and SO₂ mixing ratios were often at their highest between 04:00–10:00 local time due to the build up of fresh vehicle emission under a nocturnal inversion

A touch and pair system for battery-free 802.15.4/ZigBee home automation networks

In this paper, 2 problems affecting the acceptance of wireless devices by a wider public are introduced, and possible solutions are suggested. The first obstacle is linked to the necessity of changing the batteries of autonomous wireless nodes after. Although this problem can be solved to a certain extent by using battery-less devices, the energy need of flexible protocols such as ZigBee increases the complexity of such a device autonomously joining a network (including association and binding). A solution based on RFID components that allow the transfer of pairing information using a “Touch and Pair” system is presented. It is shown that a consumer device such as an iPod/iPhone can be modified to serve as a user friendly pairing device. Using ultra low power components, battery-less switches sending ZigBee compatible frames are built. Key network parameters can be transferred from the iPod/iPhone to the switch or other endpoints and thus allow a fast and simple configuration of battery-less elements on the network

13-month climatology of the aerosol hygroscopicity at the free tropospheric site Jungfraujoch (3580 m a.s.l.)

A hygroscopicity tandem differential mobility analyzer (HTDMA) was operated at the high-alpine site Jungfraujoch in order to characterize the hygroscopic diameter growth factors of the free tropospheric Aitken and accumulation mode aerosol. More than ~5000 h of valid data were collected for the dry diameters <i>D</i><sub>0</sub> = 35, 50, 75, 110, 165, and 265 nm during the 13-month measurement period from 1 May 2008 through 31 May 2009. No distinct seasonal variability of the hygroscopic properties was observed. Annual mean hygroscopic diameter growth factors (<i>D</i>/<i>D</i><sub>0</sub>) at 90% relative humidity were found to be 1.34, 1.43, and 1.46 for <i>D</i><sub>0</sub> = 50, 110, and 265 nm, respectively. This size dependence can largely be attributed to the Kelvin effect because corresponding values of the hygroscopicity parameter κ are nearly independent of size. The mean hygroscopicity of the Aitken and accumulation mode aerosol at the free tropospheric site Jungfraujoch was found to be κ≈0.24 with little variability throughout the year. <br><br> The impact of Saharan dust events, a frequent phenomenon at the Jungfraujoch, on aerosol hygroscopicity was shown to be negligible for <i>D</i><sub>0</sub><265 nm. Thermally driven injections of planetary boundary layer (PBL) air, particularly observed in the early afternoon of summer days with convective anticyclonic weather conditions, lead to a decrease of aerosol hygroscopicity. However, the effect of PBL influence is not seen in the annual mean hygroscopicity data because the effect is small and those conditions (weather class, season and time of day) with PBL influence are relatively rare. <br><br> Aerosol hygroscopicity was found to be virtually independent of synoptic wind direction during advective weather situations, i.e. when horizontal motion of the atmosphere dominates over thermally driven convection. This indicates that the hygroscopic behavior of the aerosol observed at the Jungfraujoch can be considered representative of the lower free troposphere on at least a regional if not continental scale

Seasonal and elevational variations of black carbon and dust in snow and ice in the Solu-Khumbu, Nepal and estimated radiative forcings

Black carbon (BC) and dust deposited on snow and glacier surfaces can reduce the surface albedo, accelerate snow and ice melt, and trigger albedo feedback. Assessing BC and dust concentrations in snow and ice in the Himalaya is of interest because this region borders large BC and dust sources, and seasonal snow and glacier ice in this region are an important source of water resources. Snow and ice samples were collected from crevasse profiles and snow pits at elevations between 5400 and 6400 m a.s.l. from Mera glacier located in the Solu-Khumbu region of Nepal during spring and fall 2009, providing the first observational data of BC concentrations in snow and ice from the southern slope of the Himalaya. The samples were measured for Fe concentrations (used as a dust proxy) via ICP-MS, total impurity content gravimetrically, and BC concentrations using a Single Particle Soot Photometer (SP2). Measured BC concentrations underestimate actual BC concentrations due to changes to the sample during storage and loss of BC particles in the ultrasonic nebulizer; thus, we correct for the underestimated BC mass. BC and Fe concentrations are substantially higher at elevations \u3c 6000 m due to post-depositional processes including melt and sublimation and greater loading in the lower troposphere. Because the largest areal extent of snow and ice resides at elevations \u3c 6000 m, the higher BC and dust concentrations at these elevations can reduce the snow and glacier albedo over large areas, accelerating melt, affecting glacier mass balance and water resources, and contributing to a positive climate forcing. Radiative transfer modeling constrained by measurements at 5400 m at Mera La indicates that BC concentrations in the winter–spring snow/ice horizons are sufficient to reduce albedo by 6–10% relative to clean snow, corresponding to localized instantaneous radiative forcings of 75–120 W m−2. The other bulk impurity concentrations, when treated separately as dust, reduce albedo by 40–42% relative to clean snow and give localized instantaneous radiative forcings of 488 to 525 W m−2. Adding the BC absorption to the other impurities results in additional radiative forcings of 3 W m−2. The BC and Fe concentrations were used to further examine relative absorption of BC and dust. When dust concentrations are high, dust dominates absorption, snow albedo reduction, and radiative forcing, and the impact of BC may be negligible, confirming the radiative transfer modeling. When impurity concentrations are low, the absorption by BC and dust may be comparable; however, due to the low impurity concentrations, albedo reductions are small. While these results suggest that the snow albedo and radiative forcing effect of dust is considerably greater than BC, there are several sources of uncertainty. Further observational studies are needed to address the contribution of BC, dust, and colored organics to albedo reductions and snow and ice melt, and to characterize the time variation of radiative forcing

Effective density of Aquadag and fullerene soot black carbon reference materials used for SP2 calibration

The mass and effective density of black carbon (BC) particles generated from aqueous suspensions of Aquadag and fullerene soot was measured and parametrized as a function of their mobility diameter. The measurements were made by two independent research groups by operating a differential mobility analyser (DMA) in series with an aerosol particle mass analyser (APM) or a Couette centrifugal particle mass analyser (CPMA). Consistent and reproducible results were found in this study for different production lots of Aquadag, indicating that the effective density of these particles is a stable quantity and largely unaffected by differences in aerosol generation procedures and suspension treatments. The effective density of fullerene soot particles from one production lot was also found to be stable and independent of suspension treatments. Some differences to previous literature data were observed for both Aquadag and fullerene soot at larger particle diameters. Knowledge of the exact relationship between mobility diameter and particle mass is of great importance, as DMAs are commonly used to size-select particles from BC reference materials for calibration of single particle soot photometers (SP2), which quantitatively detect the BC mass in single particles