Angela Marinoni

High frequency new particle formation in the Himalayas

Rising air pollution levels in South Asia will have worldwide environmental consequences. Transport of pollutants from the densely populated regions of India, Pakistan, China, and Nepal to the Himalayas may lead to substantial radiative forcing in South Asia with potential effects on the monsoon circulation and, hence, on regional climate and hydrological cycles, as well as to dramatic impacts on glacier retreat. An improved description of particulate sources is needed to constrain the simulation of future regional climate changes. Here, the first evidence of very frequent new particle formation events occurring up to high altitudes is presented. A 16-month record of aerosol size distribution from the Nepal Climate Observatory at Pyramid (Nepal, 5,079 m above sea level), the highest atmospheric research station, is shown. Aerosol concentrations are driven by intense ultrafine particle events occurring on >35% of the days at the interface between clean tropospheric air and the more polluted air rising from the valleys. During a pilot study, we observed a significant increase of ion cluster concentrations with the onset of new particle formation events. The ion clusters rapidly grew to a 10-nm size within a few hours, confirming, thus, that in situ nucleation takes place up to high altitudes. The initiation of the new particle events coincides with the shift from free tropospheric downslope winds to thermal upslope winds from the valley in the morning hours. The new particle formation events represent a very significant additional source of particles possibly injected into the free troposphere by thermal winds.

Saharan dust and daily mortality in Emilia-Romagna (Italy)

Objective To investigate the association between Saharan dust outbreaks and natural, cardiovascular and respiratory mortality. Methods A case–crossover design was adopted to assess the effects of Saharan dust days (SDD) on mortality in the Emilia-Romagna region of Italy. The population under study consisted of residents in the six main towns of the central-western part of the region who died between August 2002 and December 2006. The association of Saharan dust outbreaks and PM10 concentration with mortality was estimated using conditional logistic regression, adjusted for apparent temperature, holidays, summer population decrease, flu epidemic weeks and heat wave days. The role of the interaction term between PM10 and SDD was analysed to test for effect modification induced by SDD on the PM10-mortality concentration–response function. Separate estimates were undertaken for hot and cold seasons. Results We found some evidence of increased respiratory mortality for people aged 75 or older on SDD. Respiratory mortality increased by 22.0% (95% CI 4.0% to 43.1%) on the SDD in the whole year model and by 33.9% (8.4% to 65.4%) in the hot season model. Effects substantially attenuated for natural and cardiovascular mortality with ORs of 1.042 (95% CI 0.992 to 1.095) and 1.043 (95% CI 0.969 to 1.122), respectively. Conclusions Our findings suggest an association between respiratory mortality in the elderly and Saharan dust outbreaks. We found no evidence of an effect modification of dust events on the concentration–response relationship between PM10 and daily deaths. Further work should be carried out to clarify the mechanism of action.

Angular Illumination and Truncation of Three Different Integrating Nephelometers: Implications for Empirical, Size-Based Corrections

Integrating nephelometers are widely used for monitoring and research applications related to air pollution and climate. Several commercial versions of the instrument are available and are in wide use in the community. This article reports on results from a calibration and intercomparison workshop where several units of the three most widely used nephelometer models were tested with respect to their CO2 calibration accuracy and stability and non-idealities of their angular illumination function. Correction factors that result from the non-ideal illumination due to truncation of the sensing volumes in the near-forward and near-backward angular ranges and for non-Lambertian illumination from the light sources are presented, in particular for two models that have not previously been tested in this respect. The correction factors ranged from 0.95 to 1.15 depending on the model of nephelometer and aerosol size distribution. Recommendations for operational data analysis in context of these and previous performance tests are presented.

Light absorption properties of brown carbon in the high Himalayas

The light-absorbing properties of water-soluble brown carbon (WS-BrC) and methanol-soluble brown carbon (MeS-BrC) were studied in PM10 aerosols collected at the “Nepal Climate Observatory-Pyramid” (NCO-P) station (5079 m above sea level) during the period 2013–2014. The light absorption coefficients of WS-BrC and MeS-BrC were the highest during the premonsoon season and the lowest during monsoon. MeS-BrC absorbs about 2 times higher at 365 nm and about 3 times more at 550 nm compared to WS-BrC. The mass absorption cross section (MAC) of WS-BrC measured at 365 nm is similar to that observed previously at South Asian low-altitude sites. Fractional solar radiation absorption by BrC compared to BC considering the full solar spectrum showed that WS-BrC absorbs 4 ± 1% and MeS-BrC absorbs 9 ± 2% compared to BC at NCO-P. Such ratios become 8 ± 1% (for WS-BrC respect to BC) and 17 ± 5% (for MeS-BrC respect to BC) when accounting for correction factors proposed by previous studies to convert absorption coefficients in bulk solutions into light absorption by accumulation mode aerosol particles. These results confirm the importance of BrC in contributing to light-absorbing aerosols in this region of the world. However, the BrC absorption at 550 nm appears small compared to that of BC (1–5%, or 3–9% with conversion factors), and it is lower compared to global model estimates constrained by Aerosol Robotic Network observations. Finally, our study provides no clear evidence of a change in the fractional contribution of BrC with respect to BC to light absorption in the middle troposphere respect to the Indo-Gangetic plain boundary layer.

Transport of short-lived climate forcers/ pollutants (SLCF/P) to the Himalayas during the South Asian summer monsoon onset

Over the course of six years (2006–2011), equivalent black carbon (eqBC), coarse aerosol mass (PM1–10), and surface ozone (O3), observed during the monsoon onset period at the Nepal Climate Observatory–Pyramid WMO/GAW Global Station (NCO-P, 5079 m a.s.l.), were analyzed to investigate events characterized by a significant increase in these short-lived climate forcers/pollutants (SLCF/P). These events occurred during periods characterized by low (or nearly absent) rain precipitation in the central Himalayas, and they appeared to be related to weakening stages (or ‘breaking’) of the South Asian summer monsoon system. As revealed by the combined analysis of atmospheric circulation, air-mass three-dimensional back trajectories, and satellite measurements of atmospheric aerosol loading, surface open fire, and tropospheric NOx, the large amount of SLCF/P reaching the NCO-P appeared to be related to natural (mineral dust) and anthropogenic emissions occurring within the PBL of central Pakistan (i.e., Thar Desert), the Northwestern Indo-Gangetic plain, and the Himalayan foothills. The systematic occurrence of these events appeared to represent the most important source of SLCF/P inputs into the central Himalayas during the summer monsoon onset period, with possible important implications for the regional climate and for hydrological cycles.

Atmospheric Pollution in the Hindu Kush–Himalaya Region

Abstract This paper presents a detailed review of atmospheric pollution observed in the Hindu Kush–Himalaya (HKH) region and its implications for regional climate. Data from in situ measurements made at high-altitude stations in the HKH region, observations from satellite-based instruments, and global climate modeling study results are discussed. Experimental observations discussed include both atmospheric measurements and data from snow and ice core sampling from different glaciers in the HKH region. The paper focuses on the atmospheric brown cloud loadings over the Himalayas, particularly black carbon (BC) and ozone, which have links to regional climate and air-pollution–related impacts. Studies show elevated levels of anthropogenic ozone and BC over the Himalayas during the pre-monsoon season with concentrations sometimes similar to those observed over an average urban environment. The elevated concentration observed over the Himalayas is thought to come from the lowlands, especially the highly populated areas of the Indo-Gangetic Plains. The implications of high BC loading in the Himalayan atmosphere as well as elevated BC deposition on snow and ice surfaces for regional climate, hydrological cycle, and glacial melt are discussed.

Only coarse particles from the Sahara

REFERENCES 1. Lauer R, Burns T, Clarke W, et al. Childhood predictors of future blood pressure. Hypertension. 1991;18:74–81. 2. Brook RD, Rajagopalan S, Pope CA III, et al. Particulate matter air pollution and cardiovascular disease: An update to the scientific statement from the American Heart Association. Circulation. 2010;121:2331–2378. 3. Baumgartner J, Schauer JJ, Ezzati M, et al. Indoor air pollution and blood pressure in adult women living in rural China. Environ Health Perspect. 2011;119:1390–1395. 4. Clark ML, Bazemore H, Reynolds SJ, et al. A baseline evaluation of traditional cook stove smoke exposures and indicators of cardiovascular and respiratory health among Nicaraguan women. Int J Occup Environ Health. 2011;17: 113–121. 5. McCracken J, Smith K, Díaz A, et al. Chimney stove intervention to reduce long-term wood smoke exposure lowers blood pressure among Guatemalan women. Environ Health Perspect. 2007;115:996–1001. 6. Smith KR, Mehta S, Maeusezahl-Feuz M. Indoor air pollution from household solid fuel use. In: Ezzati M, Lopez AD, Rodgers A, Murray CJL, eds. Comparative Quantification of Health Risks: Global and Regional Burden of Disease Attributable to Selected Major Risk Factors. Geneva: World Health Organization; 2004:1435–1493. 7. Baumgartner J, Schauer J, Ezzati M, et al. Patterns and predictors of personal exposure to indoor air pollution from biomass combustion among women and children in rural China. Indoor Air. 2011;21:479–488.

Influence of lower stratosphere/upper troposphere transport events on surface ozone at the Everest-Pyramid GAW Station (Nepal): first year of analysis

In this work, we present the first systematic identification of episodes of air mass transport from the lower stratosphere/upper troposphere (LS/UT) in the middle troposphere of the southern Himalayas. For this purpose, we developed an algorithm to detect LS/UT transport events on a daily basis at the Everest-Pyramid GAW station (EV-PYR, 5079 m a.s.l., Nepal). In particular, in situ surface ozone and atmospheric pressure variations as well as total ozone values from OMI satellite measurements have been analysed. Further insight is gained from three-dimensional backward trajectories and potential vorticity calculated with the LAGRANTO model. According to the algorithm outputs, 9.0% of the considered data set (365 days from March 2006 to February 2007) was influenced by this class of phenomena with a maximum of frequency during dry and pre-monsoon seasons. During 25 days of LS/UT transport events for which any influence of anthropogenic pollution was excluded, the daily ozone mixing ratio increased by 9.3% compared to the seasonal values. This indicates that under favourable conditions, downward air mass transport from the LS/UT can play a considerable role in determining the concentrations of surface ozone in the southern Himalayas.

Vertical distribution of aerosol optical properties in the Po Valley during the 2012 summer campaigns

Studying the vertical distribution of aerosol particle physical and chemical properties in the troposphere is essential to understand the relative importance of local emission processes vs. long-range transport for column-integrated aerosol properties (e.g. the aerosol optical depth, AOD, affecting regional climate) as well as for the aerosol burden and its impacts on air quality at the ground. The main objective of this paper is to investigate the transport of desert dust in the middle troposphere and its intrusion into the planetary boundary layer (PBL) over the Po Valley (Italy), a region considered one of the greatest European pollution hotspots for the frequency that particulate matter (PM) limit values are exceeded. Events of mineral aerosol uplift from local (soil) sources and phenomena of hygroscopic growth at the ground are also investigated, possibly affecting the PM concentration in the region as well. During the PEGASOS 2012 field campaign, an integrated observing–modelling system was set up based on near-surface measurements (particle concentration and chemistry), vertical profiling (backscatter coefficient profiles from lidar and radiosoundings) and Lagrangian air mass transport simulations by FLEXPART model. Measurements were taken at the San Pietro Capofiume supersite (4439 N, 1137 E; 11 m a.s.l.), located in a rural area relatively close to some major urban and industrial emissive areas in the Po Valley. Mt. Cimone (4412 N, 1042 E; 2165 m a.s.l.) WMO/GAW station observations are also included in the study to characterize regional-scale variability. Results show that, in the Po Valley, aerosol is detected mainly below 2000 m a.s.l. with a prevalent occurrence of non-depolarizing particles (> 50 % throughout the campaign) and a vertical distribution modulated by the PBL daily evolution. Two intense events of mineral dust transport from northern Africa (19–21 and 29 June to 2 July) are observed, with layers advected mainly above 2000 m, but subsequently sinking and mixing in the PBL. As a consequence, a non-negligible occurrence of mineral dust is observed close to the ground (∼ 7 % of occurrence during a 1-month campaign). The observations unambiguously show Saharan dust layers intruding the Po Valley mixing layer and directly affecting the aerosol concentrations near the surface. Finally, lidar observations also indicate strong variability in aerosol on shorter timescales (hourly). Firstly, these highlight events of hygroscopic growth of anthropogenic aerosol, visible as shallow layers of low depolarization near the ground. Such events are identified during early morning hours at high relative humidity (RH) conditions (RH> 80 %). The process is observed concurrently with high PM1 nitrate concentration (up to 15 μg cm−3) and hence mainly explicable by deliquescence of fine anthropogenic particles, and during mineral dust intrusion episodes, when water condensation on dust particles could instead represent the dominant contribution. Secondly, lidar images show frequent events (mean daily occurrence of ∼ 22 % during the whole campaign) of rapid uplift of mineral depolarizing particles in afternoon– evening hours up to 2000 m a.s.l. height. The origin of such particles cannot be directly related to long-range transport Published by Copernicus Publications on behalf of the European Geosciences Union. 5372 S. Bucci et al.: Aerosol particle optical properties in the Po Valley events, being instead likely linked to processes of soil particle resuspension from agricultural lands.

28 Chemical composition of fresh snow in the Himalaya and Karakoram

Abstract The interpretation of firn and ice cores in high-altitude sites in central Asia requires a detailed knowledge of fresh-snow chemistry, especially in the extra-monsoon season. Since 1992 the Water Research Institute of CNR has been involved in sampling and analysis of wet and snow deposition in the Himalayan area. The first campaigns, which were based at the EV-K 2 -CNR Pyramid site in Khumbu Valley, were focused on the southern side of the Everest group in monsoon season with the aim of evaluating the long-range transport of inorganic pollutants from the Indian subcontinent to the Himalayan range. In the following years, involving climbing expeditions, we extended our research to other regions outside the monsoon season. This approach allowed us to get a better knowledge of spatial and temporal distribution of major ions in snow deposition of the Himalayan region. Furthermore, our results show that nitrate and ammonium concentrations can be biased by post-depositional gas absorption. In fact the interpretation of nitrate values in glaciochemistry is rather difficult because nitrate concentrations in snow are affected by post-exchange with the atmosphere over a broad range of environmental conditions.