Water-soluble ions and carbon content of size-segregated aerosols in New Delhi, India: direct and indirect influences of firework displays

The particle size distribution and water-soluble inorganic ion (WSII) and carbonaceous species in size-segregated aerosols, Dp < 0.95, 0.95 < Dp < 1.5, 1.5 < Dp < 3.0, 3.0 < Dp < 7.2, and 7.2 < Dp < 10 μm, were investigated during Diwali firework displays in New Delhi, India. The firework activity had the maximum contribution to the mass loading of PM_0.95 (786 μg/m³) followed by PM_0.95-1.5 (216 μg/m³) with all other three fractions accounting to a total of 214 μg/m³. The percentage contributions of WSII to the total mass of aerosols were highest in first two size fractions (39 and 40 %, respectively), compared to other fractions. The firework marker ion (Mg²⁺, Cl^-, and K⁺) mass concentration shows higher values in PM_0.95 during Diwali compared to before Diwali period. The mass size distribution of particles, NH₄⁺, K⁺, Cl^-, SO₄^2-, Mg²⁺, and NO₃^-, also showed changes on the Diwali night compared to previous and after days. The high Cl^-/Na⁺ (5.6) and OC/EC (3.4) ratio of PM_0.95 can be used as the indicators of firework displays. The lowering of mixing height on Diwali night to 50 m compared to before (277 mts) and after (269 mts) Diwali period further concentrated the aerosols in ambient atmosphere. Therefore, the firework display not only released the gaseous or elemental constituent but also influenced the temperature profile and both put together result in high aerosol concentrations, WSII, OC, and BC contents in ambient atmosphere. The alveolar, respirable, and inhalable fractions accounted for 64.6, 90.8, and 97.8 %, respectively, of the total PM₁₀ mass. People stay exposed to such high pollution level in short span of 6-8 h and experience adverse health impacts due to high mass concentrations and the chemical components of fine aerosols.

Analysis of the vertical radon structure at the Spanish "El Arenosillo" tower station

This paper presents an analysis of one year of hourly radon and meteorological measurements at 10 m and 100 m a.g.l. at El Arenosillo tall-tower station, in the south-west of the Iberian Peninsula. Whole-year and seasonal composites of the diurnal radon cycle show the expected behaviour, with larger concentrations at 10 m than at 100 m during the night, due to poor vertical mixing, and similar concentrations at both heights during the daylight hours. Wind speed and wind direction analyses by sector show the prevailing contributions for each season. Sectors with air which has spent a longer period over the ocean and high wind speeds will lead to low concentrations at both levels, whereas inland sectors show a clear increase of the concentrations with similar overall averages for the two levels. The Sierra Morena, Guadalquivir and Bethics System sectors (continental pathways) are the sectors that show higher concentrations for mild to large wind speeds. The daily evolution of radon concentration differences at both heights has been grouped into four clusters by using a K-means algorithm method. The four clusters have been selected so that they sufficiently describe different characteristics in terms of stability. The temporal evolution of the mixing height (MH) and of the bulk diffusivity parameter (Kb) during the nocturnal period has been calculated by using the temporal variation of (222)Rn concentration at 10 m and the concentration gradient with height, respectively.

ESTIMATION OF ATMOSPHERIC MIXING HEIGHTS OVER LARGE AREAS USING DATA FROM AIRPORT METEOROLOGICAL STATIONS

For this study, ground and sounding meteorological data at 16 airports were used for estimating the atmospheric mixing heights in Hebei Province of China, including Beijing and Tanjing areas. Three methods were compared for this purpose, which are the dry adiabatic method, the conventional Nozaki model, and a modified Nozaki model. The feasibility of using airport meteorological data to determine mixing heights in large area was verified through the use of measured mixing heights and observed SO₂ vertical profiles. The study not only estimated the mixing heights over large areas but also compared different early morning sounding temperature profiles to identify feasibility of using 2:00 a.m. sounding profiles to estimate mixing height by the dry adiabatic method. The paper also described the mixing heights over different areas such as mountain, sea boundary and plain areas. The results have considerable significance for air quality prediction and environmental management. A novel approach to estimation of atmospheric mixing heights over large area is introduced, requiring only the input of readily available airport meteorological data.