Apportionment of long-term trends in different sections of total ozone column over tropical region.

The additive time-series decomposition analysis was performed on National Oceanic and Atmospheric Administration Solar Backscatter Ultraviolet Instrument Merge satellite dataset version 8.6 for the period January 1979 to December 2019 with an objective to detect and apportion long-term trends present in the total ozone column (TOC) and the long-term trends exist in the respective ozone contents present in the vertical sub-columns constituting the TOC viz. upper, middle and lower stratosphere as well as near-surface for the tropical region. Linear regression analysis was performed on the deseasonalized monthly mean time series of TOC and corresponding ozone contents present in each partitioned layer for three different time spans, viz. 1979-2019 (complete time series), 1979-1998 (pre-inflection years), and 1999-2019 (post-inflection years), where 1998 was taken as inflection year. For the complete time-series, statistically significant negative trends were observed in TOC and corresponding ozone contents in the sub-columns over most of the tropical region. Expectedly, during pre-inflection years, strong negative trends were noted for TOC and ozone contents in the partitioned vertical layers. In contrast, during the post-inflection year time span, long-term trends in TOC were statistically insignificant over two-third of the tropical region, but one-third of the subtropical region exhibited negative trends in TOC. During this time span, positive trends were observed in the ozone contents present in the upper stratospheric sub-column. However, negative trends in ozone contents persisted in the middle and the lower stratosphere. It was interesting to note that the ozone contents confined in near-surface layer manifested strong negative trends during pre-inflection years and the same reversed into strong positive trends that in post-inflection span. The observed, contrasting, long-term trends and variability in the respective partitioned layer of the TOC confounded any clear sign of recovery in the TOC over the tropical region. The continuation of declining trends in the middle stratosphere and increasing trends in the near-surface layer of ozone contents is a matter of concern.

Wintertime carbonaceous aerosols over Dhauladhar region of North-Western Himalayas.

Carbonaceous aerosols play an important role in affecting human health, radiative forcing, hydrological cycle, and climate change. As our current understanding about the carbonaceous aerosols, the source(s) and process(es) associated with them in the ecologically sensitive North-Western Himalayas are limited; this systematic study was planned to understand inherent dynamics in the mass concentration and source contribution of carbonaceous aerosols in the Dhauladhar region. During four winter months (January 2015-April 2015), 24-h PM10 samples were collected every week simultaneously at the rural site of Pohara (32.19° N, 76.20° E; 750 m amsl) and the urban location of Dharamshala (32.20° N, 76.32° E; 1350 m amsl). These samples were analyzed by using thermal/optical carbon analyzer for different carbon forms. Organic carbon (OC) dominated over elemental carbon (EC) and was found to be 59.3 and 64.1% in total carbon (TC) at Pohara and Dharamshala, respectively. The respective mass concentrations of OC and EC were higher at Pohara (6.8 ± 2.3 and 4.8 ± 2.0 µg.m-3) in comparison to that observed in Dharamshala (5.0 ± 3.1 and 2.5 ± 0.6 µg.m-3). The OC/EC ratio at Pohara (1.51 ± 0.41) indicates the dominance of fossil fuel combustion (coal and vehicular exhaust), while at Dharamshala, an OC/EC of 2.01 ± 1.07 signified additional contribution from secondary organic carbon (SOC). Diagnostic ratios (OC/EC and char-EC/soot-EC) suggested dominance of emissions from fossil fuel combustion sources over biomass burning sources in the region. Estimated non-sea salt (nss)K+/OC and nssK+/EC ratios indicated heterogeneity within the biomass burning sources over low and high altitude locations. A strong correlation between nssK+ and SOC over a high altitude urban location further suggested possible conversion of gaseous precursors to carbonaceous particles during coniferous wood burning.

Profile of particulate-bound organic compounds in ambient environment of Srinagar: a high-altitude urban location in the North-Western Himalayas.

Twenty-four hourly samples of total suspended particulate matter (TSPM) were collected once a week over 17 months in the ambient environment of Srinagar (altitude 1524 m), an urban montane location in the North-Western Himalayas. The samples were analyzed to identify and quantify the presence of diverse organic compounds (OCs) using thermal desorption gas chromatography mass spectroscopy (TD-GCMS). Non-polar organic compounds-n-alkanes, polycyclic aromatic hydrocarbons (PAHs), and molecular tracers (retene and nicotine), were detected in the TSPM samples. Molecular diagnostic ratios, derived from the quantified n-alkanes and PAHs in TSPM, assisted in characterization of the contributing sources. Significant variation in the planetary boundary layer height (meters) with change in season (summer to winter) in this region, also, affected the observed variation in the temporal profile of TSPM-bound OCs. TSPM-bound OCs were predominantly contributed from petroleum and biomass combustion; to a lesser extent from biogenic sources. High concentrations of retene and nicotine, known molecular tracers for coniferous wood combustion and tobacco smoke, respectively, were detected in the winter samples. Seasonal variation in TSPM-bound retene corresponded with the periodicity of biomass burning activity in the region. The benzo(a)pyrene equivalent (BAPE) concentrations, a measure for the carcinogenicity of TSPM-bound PAHs was calculated and the value exceeded the prescribed international standards in winter. This finding poses a major health concern for the inhabitants of this region. High BAPE concentration of PAHs during winter was linked to fossil fuel and biomass combustion, where the prevalent meteorology and topography played a synergistic role.

Characterization of aerosol associated non-polar organic compounds using TD-GC-MS: a four year study from Delhi, India.

Aerosol associated Non-Polar Organic Compounds (NPOCs)--25 n-alkanes, 17 Polycyclic Aromatic Hydrocarbons (PAHs), and 3 Isoprenoid hydrocarbons--have been identified and quantified in PM10 samples collected over four years in time sequence (2006-2009), using Thermal Desorption Gas Chromatography Mass Spectrometry, in Delhi region. Established organic markers, associated diagnostic parameters, and molecular diagnostic ratios were used to assess and discern the contributing biogenic, petrogenic and pyrogenic sources to NPOCs. Analysis show that anthropogenic contributions to NPOCs exhibit increase from 2006 to 2009. Distribution profiles of NPOCs were significantly affected by change in season. Lower concentrations of NPOCs during summer months, and higher during winter, once scaled to Planetary Boundary Layer height, suggests that contributing sources were most active during summer months. During monsoon season high mass fractions of Total n-alkanes (ppm), Total PAHs (ppm), and Black carbon (BC) % alludes at the role of differential washout process involving hydrophilic and hydrophobic fractions of ambient aerosols. Significantly high, four year average concentrations of TPAH and BC signify the dominance of pyrogenic source contributions to PM10. High correlation between monthly mean concentrations of TPAH and BC (R(2)=0.75) suggests that besides common emission source, they are also contributed, individually, by exclusive independent sources.

Emission estimates of particulate matter and heavy metals from mobile sources in Delhi (India).

An attempt has been made to make a comprehensive emission inventory of particulate matter (PM) of various size fractions and also of heavy metals (HMs) emitted from mobile sources (both exhaust and non-exhaust) from the road transport of Delhi, India (1991-2006). COPERT-III and 4 models were mainly used toestimate these emissions. Results show that the annual exhaust emission of PM of size upto 2.5 micrometer (PM2.5) has increased from 3Gg to 4.5Gg during 1991-2006 irrespective of'improvement in vehicle-technology and fuel use. PM emission from exhaust and non-exhaust sources in general has increased. Heavy commercial vehicles-need attention to control particulate emission as it emerged as a predominant source of PM emissions. Among non-exhaust emissions of total suspended particulate matter (TSP), road-surface wear (~49%) has the prime contribution. As a result of-introduction of unleaded gasoline Pb has significantly reduced (~8 fold) whereas share of Cu and Zn are still considerable. Among non-exhaust sources, Pb release was the most significant one from tyre-wear whereas from break-wear, Cu release was found to be the most significant followed by Pb and Cr + Zn. Because of public health concerns further policies need to be developed to reduce emissions of PM and HMs from the road transport of megacity Delhi.

Self-association of Zn-insulin at neutral pH: investigation by concentration gradient--static and dynamic light scattering.

Equilibrium self-association of Zn-insulin at pH 7.0 was characterized over the range 0.3-5mg/mL by simultaneous measurement of static and dynamic light scattering. Analysis of static light scattering yielded a concentration-dependent weight-average molecular weight, and analysis of dynamic light scattering yielded a concentration-dependent intensity-average diffusion coefficient. The concentration dependence of both quantities may be accounted for to within experimental precision by a simple model, according to which the basic structural unit of Zn-insulin at concentrations exceeding 0.3mg/mL is a hexamer H. With increasing total protein concentration, hexameric protomers may self-associate in accordance with an isodesmic scheme in which a protomer may add to any prexisting oligomer H(n) to form H(n+1) with an invariant stepwise equilibrium association constant.

pH-dependent self-association of zinc-free insulin characterized by concentration-gradient static light scattering.

Insulin self-association at pH 1.85, 1.95, 3.0, 7.2, 8.0 and 10 was studied via composition gradient light scattering (CG-SLS). At pH 1.95 in acetic acid, insulin was found to exist as a monomer, and in pH 1.85 HCl as a dimer. At pH values of 3.0-8.0, the dependence of scattering intensity upon total insulin concentration at concentrations of up to 1.5mg/mL may be quantitatively accounted for by a simple isodesmic association equilibrium scheme requiring only a single association constant for addition of monomer to monomer or any oligomer. At pH 10, the association constant for addition of monomer to monomer was found to be smaller than the association constant for addition of monomer to all higher oligomers by a factor of approximately five. The isodesmic association scheme was also found to quantitatively account for the concentration dependence of the weight-average molecular weight derived from previously published sedimentation equilibrium measurements made at pH 7.0, and the best-fit value of the stepwise equilibrium constant obtained therefrom was in excellent agreement with that obtained from analysis of the light scattering data obtained at pH 7.2.

New methods for measuring macromolecular interactions in solution via static light scattering: basic methodology and application to nonassociating and self-associating proteins.

A method for rapid detection and characterization of reversible associations of macromolecules in solution is presented. A programmable dual-syringe infusion pump is used to introduce a solution of time-varying composition into parallel flow cells for concurrent measurement of laser light scattering at multiple angles and ultraviolet-visible absorbance. An experiment lasting less than 15 min produces a large and information-rich set of data, consisting of several thousand values of the Rayleigh ratio as a function of solute concentration(s) and scattering angle. Using a novel treatment of the data, the entire data set may be equally rapidly analyzed in the context of models for self-association. Validation experiments conducted on previously characterized nonassociating and self-associating proteins yielded robust values for molecular weights in the range 10-330 kDa and equilibrium association constants for dimer formation in the range 2 x 10(3)-6 x 10(5) M(-1).

Composition gradient static light scattering: a new technique for rapid detection and quantitative characterization of reversible macromolecular hetero-associations in solution.

A method for rapid detection and quantitative characterization of associations between two proteins in solution is presented, based upon continuous measurement of the Rayleigh light scattering and UV absorbance of a solution whose composition is varied with time in a controlled fashion. Collection and subsequent analysis of data are both rapid and semiautomatic. The results of validation experiments demonstrate that the technique can correctly identify complexes and reliably evaluate equilibrium constants for hetero-association.