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Anthropogenic CO2 emission reduction strategies depend on how well we track emission enhancements at the urban scale. The estimation system, based on inverse modeling, relies on our knowledge of atmospheric transport and prior flux distributions. Hence, the analysis framework must account for uncertainties associated with each component in order to interpret the variations in observed CO2. Using an ensemble of simulations, we quantify the uncertainties in simulating anthropogenic CO2 mixing ratio enhancements at 15 locations in India. Differences in the representation of transport mechanisms and prior emission in the forward model induce a consistently large model spread of 62.2% and 41.9%, respectively, in the simulated mixing ratio over cities. The analysis reports an average uncertainty of 2.2 ppm with a maximum of 8 ppm for representing diurnally averaged anthropogenic CO2 enhancement. Diurnal variations in emissions and transport induce a rectification effect in those enhancements. The outcome of this study can thus inform future atmospheric CO2 inversion modeling at an urban scale on the expected forward model uncertainties, which are the essential components in the Bayesian inversion framework, typically lacking in the Indian region. The first‐order inversion experiments show that the change in the transport model induces significant uncertainty (up to 84.9%) in anthropogenic CO2 flux estimation at the national scale. Hence, the confidence level of inverse‐based emission estimation in India depends considerably on the accuracy of atmospheric transport modeling. Plain Language Summary: India has pledged in Paris Agreement to significantly reduce its carbon emission by 2030 to combat the adverse effects of climate change. To attain the above goal, we need an improved and detailed understanding of carbon source‐sink distribution. Further, the urban emission reduction strategies call for city‐scale CO2 enhancement tracking. We can address this vital requirement by the combined use of atmospheric trace gas measurements and CO2 simulations via inverse modeling. Atmospheric inverse modeling relates the concentration of trace gases with the underlying surface fluxes and improves our existing knowledge about emissions. Using a multitude of simulations with different initial conditions and data inputs, this study shows that the details of how atmospheric transport is modeled in the inverse modeling system have a larger influence on the national carbon budget estimation than the prior assumptions of surface flux distribution over India. The transport errors cause a significant uncertainty of up to 84.9% in carbon emission estimates. Incorporating the temporal variability of prior emission estimates in the model enables us to better understand the dilution of the anthropogenic CO2 in certain conditions. The inferences from this study can be helpful in designing an urban CO2 emission monitoring system in India. Key Points: Anthropogenic urban CO2 enhancements and their uncertainties are quantified for the Indian region using Lagrangian ensemble simulationsThe model bias can be as high as 8 ppm in predicting daily anthropogenic CO2 enhancements in Indian citiesThe transport model errors alone cause a significant uncertainty of up to 84.9% in the Indian anthropogenic CO2 flux estimates [ABSTRACT FROM AUTHOR]

Priority 16 polycyclic aromatic hydrocarbons were examined in the surface water from urbanized rivers and drains. The concentration in the Hindon River, Yamuna River, and drains, respectively, varied from 1.64 to 73.4, 1.98 to 93.0, and 1.99 to 67.4 µg L−1. Total concentrations of PAHs in winter were 4.1, 2.9, and 3.6 times higher than in summer, respectively. Naphthalene, acenaphthylene, fluorene, (low molecular weight compounds) and chrysene contributed 62.3% to 74.4% and 17.7% to 24.8%, respectively, to the overall concentration. Their predominance suggested emissions from the combustion of industrial oil, wood, and grass. Due to the impact of waste water discharges, the spatial distribution was unpredictable. In comparison to the lower section of the rivers, the upper stretch had a low concentration. This suggested that it came from sources of urban emissions. Emission sources from unintentional spills and auto shops, along with local emissions and long-range atmospheric transport, were found in the source apportionment analysis. Locations where some PAHs surpassed chronic values could be hazardous to aquatic life. A thorough investigation was necessary because there are relatively few studies on persistent organic contaminants, such as polycyclic aromatic hydrocarbons, in surface waters from the area. [ABSTRACT FROM AUTHOR]

Regional weather and climate are generally impacted by global climatic phenomenon′s. Understanding the impact of global climate phenomenon′s on an atmospheric branch of the hydrological cycle is crucial to make advances in skillful precipitation forecast. The present study adopts a multiscale approach based on wavelets for unravelling the linkages between teleconnections and atmospheric moisture transport over homogeneous regions of Indian sub-continent. We investigated linkages between atmospheric moisture transport quantified as monthly integrated water vapor transport (IVT) during 1951–2022 over selected homogeneous regions and eight large scale climate oscillations using wavelet and global wavelet coherence. Our results indicate significant heterogeneity in linkages across different regions and across multiple timescales. In particular, the Indian Ocean Dipole (IOD) influence monthly IVT at intra-annual to inter-annual scale over all regions. The El Niño–Southern Oscillation (ENSO) have strong connection to monthly IVT at inter-annual scale whereas over west central region both IOD and ENSO strongly influence IVT at inter-decadal scale. While the Atlantic Multi-Decadal Oscillation and Pacific Decadal Oscillation have an impact on IVT in the north-east and southern regions, the Arctic Oscillation and North Atlantic oscillation have a strong inter-annual connection to IVT, majorly in the northwest and hilly regions. Overall, the methodology offers an effective approach for capturing the dynamics of atmospheric moisture transport in time–frequency space and provide a practical reference for prediction of atmospheric moisture transport linked precipitation over different regions of Indian subcontinent. [ABSTRACT FROM AUTHOR]

COVID-19 lockdown has given us an opportunity to investigate the pollutant concentrations in response to the restricted anthropogenic activities. The atmospheric concentration levels of nitrogen dioxide (NO2), carbon monoxide (CO) and ozone (O3) have been analysed for the periods during the first wave of COVID-19 lockdown in 2020 (25th March–31st May 2020) and during the partial lockdowns due to second wave in 2021 (25th March–15th June 2021) across India. The trace gas measurements from Ozone Monitoring Instrument (OMI) and Atmosphere InfraRed Sounder (AIRS) satellites have been used. An overall decrease in the concentration of O3 (5–10%) and NO2 (20–40%) have been observed during the 2020 lockdown when compared with business as usual (BAU) period in 2019, 2018 and 2017. However, the CO concentration increased up to 10–25% especially in the central-west region. O3 and NO2 slightly increased or had no change in 2021 lockdown when compared with the BAU period, but CO showed a mixed variation prominently influenced by the biomass burning/forest fire activities. The changes in trace gas levels during 2020 lockdown have been predominantly due to the reduction in the anthropogenic activities, whereas in 2021, the changes have been mostly due to natural factors like meteorology and long-range transport, as the emission levels have been similar to that of BAU. Later phases of 2021 lockdown saw the dominant effect of rainfall events resulting in washout of pollutants. This study reveals that partial or local lockdowns have very less impact on reducing pollution levels on a regional scale as natural factors like atmospheric long-range transport and meteorology play deciding roles on their concentration levels. [ABSTRACT FROM AUTHOR]

The study differentiates and quantifies the impacts of aerosols emitted locally within the north-east (NE) India region and those transported from outside this region to ascertain whether local or transported aerosols are more impactful in influencing this region's rainfall during the pre-monsoon season (March–April–May). Due to the existence of a declining pre-monsoon rainfall trend in NE India, the study also quantified the role of different aerosol effects in radiative forcing (RF) and rainfall. The study has been carried out using the WRF-Chem model by comparing simulation scenarios where emissions were turned on and off within and outside the NE region. The impact of all emissions as a whole and black carbon (BC) specifically was studied. Results show that aerosols transported primarily from the Indo-Gangetic Plain (IGP) were responsible for 93.98 % of the PM 10 mass over NE India's atmosphere and 64.18 % of near-surface PM 10 concentration. Transported aerosols contributed >50 % of BC, organic carbon, sulfate, nitrate, ammonium and dust aerosol concentration and are hence a major contributor to air pollution. Hence, the aerosol effects were much greater with transported aerosols. An indirect aerosol effect was found to be the major effect and more impactful, with transported aerosols that dominated both rainfall and RF and suppressed rainfall more significantly than the direct and semi-direct effect. However, the increase in direct radiative effects with an increase in transported BC counteracted the rainfall suppression caused by relevant processes of other aerosol effects. Thus, this study shows atmospheric transport to be an important process for this region, as transported emissions, specifically from the IGP, were also found to have greater control over the region's rainfall. Thus, emission control policies implemented in the IGP will reduce air pollution as well as the climatic impacts of aerosols over the NE India region. [ABSTRACT FROM AUTHOR]

The upper tropospheric ozone (O3) strongly influences the atmosphere's radiative budget. Using the Aerosol and Chemistry Model Intercomparison Project simulations, we study the influence of present‐day and future anthropogenic nitrogen oxides (NOx) emissions on the upper tropospheric O3 concentrations over India during the Asian summer monsoon (ASM). We observe that the upper tropospheric O3 concentrations increased 1.5 times over the ASM anticyclone region during the ASM due to higher NOx emissions in 2014 compared to 1850, and their transport due to convection. These NOx‐induced O3 changes exert a regional positive radiative forcing of 0.6 Wm−2 at the top of the atmosphere. The upper tropospheric O3 increases in the future with increasing NOx emissions. However, air quality policies to reduce surface NOx emissions also reduce the upper tropospheric O3 over India during the ASM. Plain Language Summary: This study estimates the change in the upper tropospheric ozone concentration, during the Asian Summer Monsoon (ASM) over India, due to the changes in atmospheric nitrogen oxides (NOx) emissions. NOx emissions have increased globally over the last 150 years due to human activities such as fuel combustion. During the ASM, some of the surface NOx and ozone from India are transported to the upper troposphere due to the vertical winds. In the upper troposphere, this transported NOx chemically reacts with other atmospheric species to form more ozone there. The upper tropospheric ozone efficiently traps atmospheric heat and thus warms the planet. Using output from community atmospheric transport simulations of NOx and ozone, we estimate that the NOx‐induced changes in the upper tropospheric ozone concentration have increased the atmospheric heat considerably in the last 150 years over India during monsoon. The upper tropospheric ozone is projected to increase in the future if all countries continue emitting more NOx from combustion activities. However, cleaner air policies aimed at reducing surface NOx emissions also reduce the upper tropospheric ozone because of reduced near‐surface NOx and ozone available for vertical transport. Key Points: Higher NOx in 2014 compared to 1850 increased the upper tropospheric O3 by 1.5 times over India during the Asian summer monsoon (ASM)NOx‐induced O3 changes exert a radiative forcing of 0.6 Wm−2 at the top of the atmosphere over the ASM anticyclone region during the ASMProjected increase in future NOx emissions leads to an increase in the upper tropospheric O3 over India during the ASM [ABSTRACT FROM AUTHOR]

Improving the estimates of CO 2 sources and sinks over India through inverse methods calls for a comprehensive atmospheric monitoring system involving atmospheric transport models that make a realistic accounting of atmospheric CO 2 variability along with a good coverage of ground-based monitoring stations. This study investigates the importance of representing fine-scale variability in atmospheric CO 2 in models for the optimal use of observations through inverse modelling. The unresolved variability in atmospheric CO 2 in coarse models is quantified by using WRF-Chem (Weather Research and Forecasting model coupled with Chemistry) simulations at a spatial resolution of 10 km × 10 km. We show that the representation errors due to unresolved variability in the coarse model with a horizontal resolution of 1 ∘ (∼ 100 km) are considerable (median values of 1.5 and 0.4 ppm, parts per million, for the surface and column CO 2 , respectively) compared to the measurement errors. The monthly averaged surface representation error reaches up to ∼ 5 ppm, which is even comparable to half of the magnitude of the seasonal variability or concentration enhancement due to hotspot emissions. Representation error shows a strong dependence on multiple factors such as time of the day, season, terrain heterogeneity, and changes in meteorology and surface fluxes. By employing a first-order inverse modelling scheme using pseudo-observations from nine tall-tower sites over India, we show that the net ecosystem exchange (NEE) flux uncertainty solely due to unresolved variability is in the range of 3.1 % to 10.3 % of the total NEE of the region. By estimating the representation error and its impact on flux estimations during different seasons, we emphasize the need to take account of fine-scale CO 2 variability in models over the Indian subcontinent to better understand processes regulating CO 2 sources and sinks. The efficacy of a simple parameterization scheme is further demonstrated to capture these unresolved variations in coarse models. [ABSTRACT FROM AUTHOR]

This study is the first attempt to assess the presence of 16 priority polycyclic aromatic hydrocarbons (PAHs) enlisted by the US Environmental Protection Agency in PM2.5 and PM10 from industrial areas of Odisha State, India. During 2017–2018, bimonthly sampling of PM10 and PM2.5 was carried out for 24 h in the industrial and mining areas of Jharsuguda and Angul in Odisha during the pre-monsoon, monsoon, and post monsoon seasons. Highest mean concentration of ∑16PAHs in PM2.5 was observed during the post monsoon (170 ng/m3) period followed by pre-monsoon (48 ng/m3) and monsoon (16 ng/m 3) periods, respectively. A similar trend of ∑16PAHs was also observed in PM10 with higher levels observed during post monsoon (286 ng/m3) followed by pre-monsoon (81 ng/m3) and monsoon (27 ng/m3) seasons. Diagnostic ratios and principal component analysis suggested diesel, gasoline and coal combustion as the major contributors of atmospheric PAH pollution in Odisha. Back trajectory analysis revealed that PAH concentration was affected majorly by air masses originating from the northwest direction traversing through central India. Toxic equivalents ranged between 0.24 and 94.13 ng TEQ/m3. In our study, the incremental lifetime cancer risk ranged between 10–5 and 10–3, representing potential cancer risk. [ABSTRACT FROM AUTHOR]

We use the idealized tracer experiments and investigate the summertime transport from the surface region of northern India and Tibetan Plateau to the lower stratosphere. It is found that the transport, compared to other surrounding regions, has an overall younger modal age in the northern lower stratosphere away from the tropopause. Analysis of the tracer budget reveals that the tracer is transported to the tropical lower stratosphere rapidly in the first 5 days due to vertical eddy transport and afterward in a month or two advection associated with the Brewer‐Dobson circulation. Meanwhile the tracer is also transported to the northern extratropical lower stratosphere in the first 3 months due to horizontal eddy mixing. The results highlight the uniqueness of the northern India region in the summertime transport to the lower stratosphere and implications for the transport of short‐lived chemical species in the destruction of stratospheric ozone. Plain Language Summary: The atmospheric transport plays a critical role in determining the concentration and distribution of chemical species in the stratosphere, in addition to emission and chemistry. In this study, we have shown the sensitivity of the transport and its associated timescale to the surface emission region. Specifically, tracers emitted from the surface region of northern India and Tibetan Plateau travel to the Northern Hemisphere lower stratosphere in an overall shorter timescale, compared to tracers that are emitted from the surrounding regions. This suggests that short‐lived chemical species with lifetimes generally under 6 months, when emitted from the surface region of northern India and Tibetan Plateau, could be transported efficiently to the Northern Hemisphere middle and high latitude stratosphere and destruct the stratospheric ozone there. Key Points: Transport from northern India has an overall younger age in the northern lower stratosphereTransport pathway to tropical lower stratosphere due to vertical eddy transport first and Brewer‐Dobson circulation advection afterwardTransport pathway to northern extratropical lower stratosphere mostly due to horizontal eddy mixing [ABSTRACT FROM AUTHOR]

Carbonyl sulfide (COS) is an atmospheric trace gas of interest for C cycle research because COS uptake by continental vegetation is strongly related to terrestrial gross primary productivity (GPP), the largest and most uncertain flux in atmospheric CO 2 budgets. However, to use atmospheric COS as an additional tracer of GPP, an accurate quantification of COS exchange by soils is also needed. At present, the atmospheric COS budget is unbalanced globally, with total COS flux estimates from oxic and anoxic soils that vary between -409 and -89 GgS yr -1. This uncertainty hampers the use of atmospheric COS concentrations to constrain GPP estimates through atmospheric transport inversions. In this study we implemented a mechanistic soil COS model in the ORCHIDEE (Organising Carbon and Hydrology In Dynamic Ecosystems) land surface model to simulate COS fluxes in oxic and anoxic soils. Evaluation of the model against flux measurements at seven sites yields a mean root mean square deviation of 1.6 pmol m -2 s -1 , instead of 2 pmol m -2 s -1 when using a previous empirical approach that links soil COS uptake to soil heterotrophic respiration. However, soil COS model evaluation is still limited by the scarcity of observation sites and long-term measurement periods, with all sites located in a latitudinal band between 39 and 62 ∘ N and no observations during wintertime in this study. The new model predicts that, globally and over the 2009–2016 period, oxic soils act as a net uptake of -126 GgS yr -1 and anoxic soils are a source of + 96 GgS yr -1 , leading to a global net soil sink of only -30 GgS yr -1 , i.e. much smaller than previous estimates. The small magnitude of the soil fluxes suggests that the error in the COS budget is dominated by the much larger fluxes from plants, oceans, and industrial activities. The predicted spatial distribution of soil COS fluxes, with large emissions from oxic (up to 68.2 pmol COS m -2 s -1) and anoxic (up to 36.8 pmol COS m -2 s -1) soils in the tropics, especially in India and in the Sahel region, marginally improves the latitudinal gradient of atmospheric COS concentrations, after transport by the LMDZ (Laboratoire de Météorologie Dynamique) atmospheric transport model. The impact of different soil COS flux representations on the latitudinal gradient of the atmospheric COS concentrations is strongest in the Northern Hemisphere. We also implemented spatiotemporal variations in near-ground atmospheric COS concentrations in the modelling of biospheric COS fluxes, which helped reduce the imbalance of the atmospheric COS budget by lowering soil COS uptake by 10 % and plant COS uptake by 8 % globally (with a revised mean vegetation budget of -576 GgS yr -1 over 2009–2016). Sensitivity analyses highlighted the different parameters to which each soil COS flux model is the most responsive, selected in a parameter optimization framework. Having both vegetation and soil COS fluxes modelled within ORCHIDEE opens the way for using observed ecosystem COS fluxes and larger-scale atmospheric COS mixing ratios to improve the simulated GPP, through data assimilation techniques. [ABSTRACT FROM AUTHOR]

The Tibetan Plateau is generally considered to be a significantly clean area owing to its high altitude; however, the transport of atmospheric pollutants from the Indian subcontinent to the Tibetan Plateau has influenced the Tibetan environments. Nyingchi is located at the end of an important water vapor channel. In this study, continuous monitoring of gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM), and particle-bound mercury (PBM) was conducted in Nyingchi from 30 March to 3 September 2019, to study the influence of the Indian summer monsoon (ISM) on the origin, transport, and behavior of Hg. The GEM and PBM during the preceding Indian summer monsoon (PISM) period (1.20±0.35 ng m -3 and 11.4±4.8 pg m -3 for GEM and PBM, respectively) were significantly higher than those during the ISM period (0.95±0.21 ng m -3 , and 8.8±6.0 pg m -3); the GOM during the PISM period (13.5±7.3 pg m -3) was almost at the same level as that during the ISM period (12.7±14.3 pg m -3). The average GEM concentration in the Nyingchi region, obtained using passive sampler, was 1.12±0.28 ng m -3 (from 4 April 2019 to 31 March 2020). The GEM concentration showed that the sampling area was very clean compared to other high-altitude sites. The GEM has several patterns of diurnal variation during different periods. Stable high GEM concentrations occur at night and low concentrations occur in the afternoon during PISM, which may be related to the nocturnal boundary layer structure. High values occurring in the late afternoon during the ISM may be related to long-range transport. Low concentrations of GEM observed during the morning in the ISM may originate from vegetation effects. The results of the trajectory model demonstrate that the sources of pollutants at Nyingchi are different with different circulation patterns. During westerly circulation in the PISM period, pollutants mainly originate from central India, northeastern India, and central Tibet. During the ISM period, the pollutants mainly originate from the southern part of the SET site. The strong precipitation and vegetation effects on Hg species during the ISM resulted in low Hg concentrations transmitted to Nyingchi during this period. Further, principal component analysis showed that long-distance transport, local emissions, meteorological factors, and snowmelt factors are the main factors affecting the local Hg concentration in Nyingchi. Long-distance transport factor dominates during PISM and ISM3, while local emissions is the major contributor between PISM and ISM3. Our results reveal the Hg species distribution and possible sources of the most important water vapor channel in the Tibetan Plateau and could serve as a basis for further transboundary transport flux calculations. [ABSTRACT FROM AUTHOR]

This study presents the characteristics of ground level atmospheric ozone (O3) over the rural mid-Brahmaputra Valley region of the northeastern India. Ozone and oxides of nitrogen (NOx = NO + NO2) concentration data were obtained from continuous measurement of O3 and NOx housed at the MAPAN-AQM station at Tezpur University. The meteorological parameters were obtained from the same station. The diel, monthly, and seasonal variations of O3 were studied. The O3-NOx photostationary state (PS) was carefully examined and it was found that the net O3 concertation deviated substantially from the PS during the winter season. The deviation could be attributed to local biomass burning, biogenic VOC emission from forest and agriculture, and long-range transport of peroxyacyl nitrate (PAN). The long-range transport has been ascertained by examining the ventilation coefficients (VC), which correlated with the steep growth of net O3 concentrations in the morning hours. The HYSPLIT air mass back trajectories were used in concentration-weighted trajectory (CWT) analyses of O3 to assess the long-range regional transport of O3 precursors, which positively influenced local O3 concentrations. [ABSTRACT FROM AUTHOR]

Eastern India is characterized by high aerosol loading of primarily anthropogenic origin due to both local emissions and long-range transport and hence outflow of air mass from the Indo-Gangetic Plains. Using a year-long measurement of atmospheric aerosol optical properties over Bhubaneswar, one of the fastest growing tier-two cities in the Eastern India, we show that the aerosol optical depth (AOD) varied between 0.39 and 0.96 with high loading during February and low during July. The Angstrom exponent (AE) was found to be mostly higher than unity indicating large dominance of fine mode particles with a larger AE. Further analysis using spectral curvature of AOD and satellite-based estimates indicates that more than 80% of the time, fine mode aerosols dominate the region. It is observed that there is a large diurnal variability in AOD (AE) of the order of 15% (5%) indicating a large change in loading (spectral characteristics) over a short period of within a day. The aerosols types inferred from spectral curvature method match reasonably well with those from MERRA-2 chemical reanalysis. Further, it is found that satellite-derived AOD's are low biased with respect to ground measurements and are unable to capture seasonality consistently. These findings show that additional research is required to assess the causes for such inconsistency especially during the monsoon period. [ABSTRACT FROM AUTHOR]

Atmospheric PM2.5-bound polycyclic aromatic hydrocarbons (PAHs) were analyzed over urban and rural sites during January to December 2018. Total annual average concentration of PM2.5 was 74.41 ± 24.96 μg/m3 over urban and 52.03 ± 13.11 μg/m3 over rural site during study time. The annual average concentration of PM2.5 over urban and rural atmospheres were found approximately twice in urban and found also higher over rural site, with respect to National Ambient Air Quality (NAAQ) standard of 40 μg/m3 for PM2.5 concentration. The annual concentration of PAHs was 750.80 ± 19.49 ng/m3 over urban, and, over rural, it was 559.59 ± 17.56 ng/m3. The seasonal variation of concentration of PAHs was in order of winter > post-monsoon > summer > monsoon. The most predominant PAHs were IcP (17.21%), B(ghi) P(15.22%), BkF (11.60%), DBahA (11.34%) and BbF (10.91%) to the total PAH concentration over urban site; over rural site, most predominant PAHs were IcP (16.02%), B(ghi)P, (15.63%), BkF (11.46%), DBahA (11.12%) and BbF (8.99%) of total PAHs. DBahA concentration was contributed approximately 46% carcinogenicity over both urban and rural sites, and BaP contributes 33.56% carcinogenicity over urban site and 34.62% carcinogenicity over rural site of total PAH samples. The Excess Life Time Cancer Risk (ELCR) values over urban were found at acceptable limit 10-6–10-4 given by the United States Environmental Protection Agency. Over rural site, the ELCR value was found near about acceptable limit. Diagnostic ratio analysis demonstrated that major sources of PAHs were pyrogenic sources and vehicular emission over study. Air parcel through trajectories over study site also contributed in PAH concentration. [ABSTRACT FROM AUTHOR]

To date Indian summer monsoon (ISM) dynamics have been assessed by changes in stalagmite δ18O. However, stalagmite δ18O is influenced by multiple environmental factors (e.g., atmospheric moisture transport, rainfall amount at the study site, and ISM seasonality), precluding simple and clear reconstructions of rainfall amount or variability. This study aims to disentangle these environmental factors by combining δ18O, δ44Ca, and elemental data from a stalagmite covering Termination II and the last interglacial from Mawmluh Cave, NE India, to produce a semiquantitative reconstruction of past ISM rainfall. We interpret δ18O as a mixed signal of rainfall source dynamics and rainfall amount and coupled δ44Ca and X/Ca ratios as indicators of local infiltration rate and prior calcite precipitation in the karst zone. The wettest conditions in our studied interval (135 and 100 kyrs BP; BP = before present, with the present being 1950 CE) occurred during Marine Isotope Stage 5e. Our multiproxy data set suggests a likely change in seasonal distribution of Marine Isotope Stage 5e rainfall compared to the Holocene; the wet season was longer with higher‐than‐modern dry season rainfall. Using the last interglacial as an analogue for future anthropogenic warming, our data suggest a more erratic ISM behavior in a warmer world. Key Points: This study represents a first multiproxy stalagmite record from the Indian summer monsoon domain covering Termination II and Marine Isotope Stage 5eCombining δ18O, δ44Ca, and elemental data helps to discriminate between rainfall source and amount and local infiltrationThe rainy season during Marine Isotope Stage 5e was wetter, likely with more extreme rainfall events, compared to the Holocene [ABSTRACT FROM AUTHOR]

Black carbon (BC) is known to have major impacts on both climate and human health and is therefore of global importance, particularly in regions close to large populations that have strong sources. The size-resolved mixing state of BC-containing particles was characterised using a single-particle soot photometer (SP2). The study focusses on the Indo-Gangetic Plain (IGP) during the pre-monsoon and monsoon seasons. Data presented are from the UK Facility for Airborne Atmospheric Measurements BAe-146 research aircraft that performed flights during the pre-monsoon (11 and 12 June) and monsoon (30 June to 11 July) seasons of 2016. Over the IGP, BC mass concentrations were greater (1.95 µgm-3) compared to north-west India (1.50 µgm-3) and north-east India (0.70 µgm-3) during the pre-monsoon season. Across northern India, two distinct BC modes were recorded; a mode of small BC particles (core diameter <0.16 µm and coating thickness <50 nm) and a mode of moderately coated BC (core diameter <0.22 µm and coating thickness of 50–200 nm). The IGP and north-east India locations exhibited moderately coated black carbon particles with enhanced coating thicknesses, core sizes, mass absorption cross sections, and scattering enhancement values compared to much lower values present in the north-west. The coating thickness and mass absorption cross section increased with altitude (13 %) compared to those in the boundary layer. As the monsoon arrived across the region, mass concentration of BC decreased over the central IGP and north-east locations (38 % and 28 % respectively), whereas for the north-west location BC properties remained relatively consistent. Post-monsoon onset, the coating thickness, core size, mass absorption cross section, and scattering enhancement values were all greatest over the central IGP much like the pre-monsoon season but were considerably reduced over both north-east and north-west India. Increases in mass absorption cross section through the atmospheric column were still present during the monsoon for the north-west and central IGP locations, but less so over the north-east due to lack of long-range transport aerosol aloft. Across the Indo-Gangetic Plain and north-east India during the pre-monsoon and monsoon seasons, solid-fuel (wood burning) emissions form the greatest proportion of BC with moderately coated particles. However, as the monsoon develops in the north-east there was a switch to small uncoated BC particles indicative of traffic emissions, but the solid-fuel emissions remained in the IGP into the monsoon. For both seasons in the north-west, traffic emissions form the greatest proportion of BC particles. Our findings will prove important for greater understanding of the BC physical and optical properties, with important consequences for the atmospheric radiative forcing of BC-containing particles. The findings will also help constrain the regional aerosol models for a variety of applications such as space-based remote sensing, chemistry transport modelling, air quality, and BC source and emission inventories. [ABSTRACT FROM AUTHOR]

The study of the fate of atmospheric release and transport of Tritium requires an understanding of the exchange/transfer of Tritium (HTO) from within the compartments; air, soil, and plant systems. The Tritium transfer parameters within these compartments are used in specific activity models to compute TFWT and OBT in terrestrial plants and are highly dependent on the site-specific conditions. Hence a study was carried out to generate site-specific Tritium transport model parameters in the tropical environment of Tarapur which receives the atmospheric releases of Tritium from nuclear facilities operating at this site, on the West coast of India. The paper presents the details of the study carried out in Tarapur, India. The transfer parameters generated through this study are soil water to air moisture HTO transfer ratio: CR s , plant water to air moisture HTO transfer ratio: R pa, and plant water to soil water HTO transfer ratio: R pw. The geometric mean and geometric standard deviation (GSD) of the transfer ratios, CR s , R pa and R pw determined were found to be 0.50 (GSD: 3.52), 0.53 (GSD: 2.51) and 1.12 (GSD: 2.58), respectively. In addition, the Tritium scavenging ratio, surface loading, and wet deposition velocity were also derived and were found to be 1.59 ± 1.32, 1.21 × 10−2 Bq m−2 s−1, and 7.91 × 10−2 m s−1, respectively. The study has generated a set of site-specific model input parameters for a tropical coastal site of Tarapur, India, and details are discussed in the manuscript. • The terrestrial tritium transport model assumes air, soil, and plant compartments. • HTO or TFWT was determined in air moisture, soil water, vegetation, and rainwater. • Derived tritium scavenging ratio, surface loading, and wet deposition velocity. • Site-specific tritium transport model parameters generated at Tarapur. [ABSTRACT FROM AUTHOR]

ABSTRACT: Atmospheric rivers (ARs), filamentary patterns of strong water vapour fluxes, play a prominent role in global poleward moisture transport and have profound impacts on extreme rainfalls (ERs). Previous AR research has mainly focused on the mid‐latitude regions, whereas the characteristics of ARs in low latitudes and their relationship with local ERs remain largely unknown. This study investigates the spatiotemporal characteristics of ARs over the Bay of Bengal and their relationship with ERs after landing on the northern Indian subcontinent using the ERA‐Interim reanalysis data. During the study period from 1979 to 2011, a total of 149 ARs have been identified, which feature a bimodal temporal pattern with more events observed in May and October. The AR axes generally stretch northeastwards over the bay and land in Bangladesh and Burma. A total of 24% of ARs occurring during tropical cyclones implies a possible connection between them, in addition to the similar intra‐annual distribution. In summer, as the tropical cyclones are weak and the northward water vapour flux decreases due to topographic blocking of the Western Ghats, it is less likely to form intensified water vapour pathway, though the atmospheric humidity is high in the study region. Furthermore, a close correlation between ARs and ERs is manifested. A large proportion of ARs would lead to ERs, with a small fraction of ERs occur after ARs. In addition, although persistent ARs constitute the majority of identified events, rainfall intensity will not be enhanced by the increase in AR duration. This study enriches the knowledge of AR characteristics in low latitudes and provides new pathways to understand the hydrological cycles in the Indian Peninsula and the Bay of Bengal. [ABSTRACT FROM AUTHOR]

In the present study, we have examined extreme rainfall events during the southwest monsoon and their relationship with vertically integrated atmospheric moisture transport. For the analysis, we have used daily rainfall data from IMD, wind and humidity data from NCEP from 1951 to 2020. Extreme rainfall events are identified when the daily rainfall value exceeds three times the standard deviation and also this rainfall amount exceeds the threshold value of 100 mm day−1 in a grid point on the spatial domain. The entire study period was divided into the first (1951–1985) and the second (1986–2020) epochs. The significant epochal differences in some key aspects of extreme rainfall events related to moisture transport mechanisms were examined in detail. For the selected epochs, distinct variabilities in monsoon rainfall were observed, especially in the northern parts of India. Furthermore, we have observed spatial variability in the frequency of occurrence of extreme rainfall events, the Central Indian region indicates an increasing trend in the frequency and its relative contribution. Whereas a significant negative trend is found in the northeast sector of the Indian subcontinent. Moreover, prominent moisture sources and their pathways that account for the extreme events were also identified using a 5-day back trajectory. Comparing the two epochs, a notable westward shift was obtained in the seasonal moisture flux and trajectories of selected rainfall events in the second epoch. The moisture from the Arabian Sea, Bay of Bengal and the Red Sea regions were contributing primarily towards the extreme rainfall events over the Indian subcontinent. In certain cases, land regions of northeast India and the Ganga basin played a crucial role in generating ample moisture. Moisture River (MR) patterns associated with extreme rainfall events were identified using vertically integrated moisture flux. During the last two decades of the study period, the MR patterns are observed to be more intense. The MR patterns are significantly influenced by the low-level wind patterns in addition to the prominent role of atmospheric moisture. First epoch -(1951–1985), Second epoch- (1986–2020), VIMF- vertically integrated moisture flux, EREs- Extreme rainfall events, MR- Moisture River patterns. [Display omitted] • Epochal variation of extreme rainfall events has been investigated for the last 70 years. • A northward shift in VIMF and Moisture convergence zones is found. • Northwestward movement in 5-day back trajectories of EREs. • Increase in EREs associated with MR patterns in the second epoch. • Increase in the frequency and relative distribution of EREs towards the seasonal total in the second epoch. [ABSTRACT FROM AUTHOR]

We use two-dimensional pre-stack depth migrated seismic reflection profiles and seafloor bathymetry to describe the continental margin structure and a massive mass-transport deposit off the west coast of India. This giant slide runs from the Gujurat–Saurashtra margin to the Laxmi Basin. It is over 330 km long, a maximum of 190 km wide and its run-out basal gradient is 1.2°. We name this giant mass wasting deposit the Nataraja Submarine Slide. This slide covers 49 ± 16 × 10 3 km 2 and represents a volume of 19 × 10 3 ± 4 × 10 3 km 3 , making it the second by volume of any passive margin landslide/mass-transport deposit. Seismic facies analysis allows the internal structure of the mass-transport deposit to be described as far as the toe. This slide has been able to circumvent massive seamounts, thus highlighting the capacity of the flow and its potential energy during emplacement in a funnel between the slope of the Western Indian passive margin and the Laxmi Ridge. Stratigraphically, the emplacement of the Nataraja Slide predates the main pulse of sedimentation during the late Miocene–Recent associated with the Indus Fan but follows rapid sedimentation across S and SE Asia during the Early–Middle Miocene. The margin architecture at the head of this slide is associated with a gravity-controlled fold and thrust belt that may have caused slope steepening and triggering of the slide. [ABSTRACT FROM AUTHOR]

Endosulfan, as an organochlorine pesticide (OCPs), was widely used in agriculture. As the largest endosulfan user country in the world and adjacent to China, it is interesting to know to what extent the endosulfan usage of India could affect the environment in China. In this study, we established gridded endosulfan usage, atmospheric emission, and soil residue inventories in 2010 based on its application in different crops in China and India. We employed an atmospheric transport model CanMETOP to simulate atmospheric and soil concentrations, as well as dry and wet deposition flux of α- and β-endosulfan. Results were used to assess the signatures of Indian endosulfan usage in the China's environment. In 2010, endosulfan usage, atmospheric emissions, and highest soil residue in China were 3083.9, 1312.7, and 587.5 tonnes, and 3204.8, 1441.4, and 463.7 tonnes in India, respectively. The spatial distribution of modeled atmospheric and soil concentrations, and dry deposition fluxes of endosulfan were in line with its usage but wet deposition fluxes were mainly identified in Southern China and Sichuan basin with heavy rainfall, especially for α-endosulfan. Endosulfan tended to transport from India to Tibetan plateau, Yunnan-Kweichow Plateau, and some provinces in southern China under the Indian Summer Monsoon regime. Due to its stronger volatility, α-endosulfan posed a more significant impact on China's environment via the atmospheric transport from India compared to β-endosulfan. Although rainfall during Indian Summer Monsoon reduced endosulfan levels in the air during its journey from India to China, it was observed that Indian endosulfan usage in 2010 contributed more than 50% of atmospheric concentrations and 30% of soil concentrations of α-endosulfan in some regions in Tibetan plateau. [Display omitted] • Endosulfan usage, atmospheric emission, and soil residue inventories were developed. • Environmental fate of endosulfan across China and India was simulated. • Indian endosulfan usage has a great impact on southwest and south of China. • α-endosulfan exhibited more significant impact on China's environment. [ABSTRACT FROM AUTHOR]

In Asia, the evaluation of black carbon (BC) using global aerosol-transport models has been incomplete due to a lack of available measurements. Recently, new measurements and datasets at various Asian sites have become available for use in model validation. In this study, we compared the BC mass concentrations obtained by an aerosol-coupled global nonhydrostatic model adopting a uniform-grid system with in-situ measurements and other models over Asia. The results revealed that our model, as well as other global models, was unable to reproduce the observed BC values at most sites in China and India, most likely due to strong local hotspots. To overcome the inconsistency between the models and measurements, we developed a new aerosol-transport model using a stretched-grid system for high-resolution simulations with up to approximately 10 km grids. Our model can be used as a global-to-regional seamless aerosol-transport model for low to high horizontal resolution simulations. [ABSTRACT FROM AUTHOR]

Water vapour transport over the Indian Ocean has been computed for the 30-year period (1979-2009). The monthly evolution of meridional moisture fluxes across different sections is presented. March and April clearly indicate the north to south flow of moisture across the equatorial region. During May there is intensification in the northward cross-equatorial moisture transport, which may act as a precursor of the rainy season. During the monsoon season maximum transport occurs in June with values of 1.24 × 1011 and 5.58 × 1012 tonnes/day for moisture and air flux across the equator respectively, which occurs in the lower atmospheric level between 1000 and 650 hPa. Our finding clearly shows that during the monsoon season across the equatorial cross-section major transport occurs between 42°E and 60°E. Analysis of moisture transport over two regions, i.e. (i) 6°S-6°N and 42- 60°E and (ii) 1.5°S-1.5°N and 42-60°E for two good (1988, 2008) and two bad (1987, 2009) monsoon years shows that during 1987, which was a drought year, the amount of moisture crossing the equator was less by about one order of magnitude compared to 1988. While during 2008, which was a normal/good monsoon year, the amount of moisture transported was almost three times compared to 2009. This clearly indicates that the moisture transport in May can be used as a predictor of monsoon performance. [ABSTRACT FROM AUTHOR]

Abstract: Polychlorinated naphthalenes (PCNs) are now under review by the Stockholm Convention as candidates for persistent organic pollutants (POPs) due to their persistence, toxicity, bioaccumulation, and long-range atmospheric transport. Data on PCN levels are sparse in South Asia. Atmospheric PCNs in India and Pakistan were monitored during the winter by polyurethane foam disk passive air samplers (PUF-PAS). The average concentrations were 29pg/m3 and 7.7pg/m3 in the Indian and Pakistani samples, respectively. Those concentration levels were relatively lower than the previously reported values in other Asian countries, but still considerably higher than in other sites in the world. Tri-CNs and tetra-CNs were the dominant homologues in the air, especially in India. Spatially, the PCNs were ubiquitous in the target areas, and local distribution was generally impacted by the proximity to potential sources. Major sources of PCNs in this study were the re-emission of Halowax and industrial thermal processes. Biomass burning influenced some sites in Pakistan. However, the enrichment of tri-CNs in Indian cities cannot be ascribed to either the signature of a specific source or the preferential volatilization and/or photodegradation in tropical areas. Despite this unclear issue in South Asia, the present study indicates that the potential health impact was generally comparable to that in non-urban sites worldwide. [Copyright &y& Elsevier]

Three models, including an atmospheric transport model, a multimedia exposure model, and a risk assessment model, were used to assess cancer risk in China caused by γ-HCH (gamma-hexachlorocyclohexane) emitted from Chinese and Indian sources. Extensive model investigations revealed the contribution of different sources to the cancer risk in China. Cancer risk in Eastern China was primarily attributable to γ-HCH contamination from Chinese sources, whereas cancer risk in Western China was caused mostly by Indian emissions. The contribution of fresh use of lindane in India to the cancer risk in China was almost 1 order of magnitude higher than that of the reemission of γ-HCH from Indian soils. Of total population, 58% (about 0.79 billion) residents in China were found to live in the environment with high levels of cancer risk exceeding the acceptable cancer risk of 10–6, recommended by the United States Environmental Protection Agency (U.S. EPA). The cancer risk in China was mostly induced by the local contamination of γ-HCH emitted from Chinese sources, whereas fresh use of lindane in India will become a significant source of the cancer risk in China if Indian emissions maintain their current levels. [ABSTRACT FROM AUTHOR]

Prediction of downwind tritium air concentrations in the environment around Narora Atomic Power Station was studied on the basis of Gaussian plume dispersion model. The tritium air concentrations by field measurement [measured tritium air concentrations in the areas adjacent to NAPS] were compared with the theoretically calculated values (predicted) to validate the model. This approach will be useful in evaluating environmental radiological impacts due to standard pressurised heavy water reactors. [ABSTRACT FROM AUTHOR]

Abstract: Columnar aerosol properties retrieved from Multi-Wavelength solar Radiometer (MWR) measurements during the period 2001–2010 over Dibrugarh (27.3°N, 94.6°E, 111 m amsl), North-Eastern India are analyzed to identify the types of aerosols in the atmospheric column. Highest Aerosol optical depth (AOD) characterizes the pre-monsoon (March–May), while lowest AOD has been observed during the post-monsoon (Oct–Nov) season. The Ångström exponent (α) indicates predominance of fine aerosols during post-monsoon and winter (Dec–Feb) and dominance of coarse mode in pre-monsoon and monsoon (June–Sept). NOAA HYSPLIT back trajectory analysis suggests that the seasonal heterogeneity in aerosol characteristics can be attributed to the varying contribution from different source regions. Using the relationship between AOD500 and α, the aerosols can be classified into five main types viz. continental average (CA), marine continental average (MCA), urban/industrial and biomass burning (UB) and desert dust (DD) while the remaining cases are considered as unidentified or mixed type (MT). These aerosol types exhibit seasonal heterogeneity in their contribution depending upon variability in sources. In winter, local production contributes to observed appreciable CA aerosol type, while highest percentage of UB type is attributed to both local and transported aerosols. On the other hand, transported UB and DD types play a significant role in the pre-monsoon season. Post-monsoon season is indicative of background continental average aerosol condition with a significant contribution from CA and MCA aerosols. Monsoon aerosols couldn''t be distinguished properly due to different particle growth processes like humidification, hygroscopic growth etc. and hence MT aerosol type is predominant in this season. This is the first ever attempt to classify aerosols over this environment. [Copyright &y& Elsevier]

Recent studies from India reported polychlorinated biphenyls (PCBs) associated with incomplete combustion processes. In this study we have monitored atmospheric PCBs in Agra, a non-metropolitan city of northern India. During first month of summer and winter of 2017, polyurethane foam based passive air sampler (PUF-PAS) was deployed at each of 14 locations across urban, suburban and rural transects and one background site. Range of Σ 25 PCBs varied between 25 and 1433 pg/m3 (Avg ± Stdev: 460 ± 461) in summer and 26–205 pg/m3 (Avg ± Stdev: 106 ± 59) in winter. Mean Σ 25 PCBs concentration, showed an urban > suburban > rural trend in summer while, in winter a rural > urban > suburban trend was observed. PCB-52 was the dominant congener and after excluding this congener no significant difference was observed between summer and winter PCB concentrations. Using a combination of K-means cluster and principal component analysis (PCA) four major source types were identified. Open burning source accorded 80% of atmospheric PCBs, majorly indicator PCBs while the remaining 20% was contributed by atmospheric transport, petrogenic combustion and biomass burning. From the ten days back trajectory of the air mass it can be suggested that atmospheric transport from the hotspots resulted in a minor percentage of dioxin like PCBs in Agra. Maximum TEQs was accorded by PCB-77 (30%) and it is consistent with previous observations from Agra. Levels observed in the current study are well within the public health guideline based on inhalation unit risk (10 ng/m3) and United States Environmental Protection Agency's regional screening level high risk tier (4.9 ng/m3) for ambient air. Image 1 • During summer distinct urban > suburban > rural trend was observed in Agra. • Elevated PCBs in the rural transect during winter is presumably due to biomass burning. • PCB-52 is the dominant congener and related to open burning of dumped municipal waste. • Minor fraction of dioxin like PCBs might have resulted from short range atmospheric transport. [ABSTRACT FROM AUTHOR]

We present here spectroscopic compositional analysis of brown carbon (BrC) and humic-like substances (HULIS) in the Indian context under varying conditions of source emissions and atmospheric processing. To this end, we study bulk water-soluble organic matter (WSOM), neutral- and acidic-HULIS (HULIS-n and HULIS-a), and high-polarity (HP)-WSOM collected in the eastern Indo-Gangetic Plain (IGP) with respect to UV–Vis, fluorescence, FT-IR, 1H NMR and 13C characteristics under three aerosol regimes: photochemistry-dominated summer, aged biomass burning (BB)-dominated post-monsoon, and fresh BB-dominated winter. Absorption coefficients (b abs_365 nm ; Mm−1) of WSOM and HULIS fractions increase by a factor of 2–9 during winter as compared to summer, with HULIS-n dominating total HULIS + HP-WSOM absorption (73–81%). Fluorophores in HULIS-n appear to contain near-similar levels of aromatic and unsaturated aliphatic conjugation across seasons, while HULIS-a exhibits distinctively smaller-chain structures in summer and post-monsoon. FT-IR spectra reveals, among others, strong signatures of aromatic phenols in winter WSOM suggesting a BB-related origin. 1H NMR-based source attribution coupled with back trajectory analysis indicate the presence of secondary and BB-related organic aerosol (SOA and BBOA) in the post-monsoon and winter, and marine-derived OA (MOA) in the summer, which is supported by 13C measurements. Overall, these observations uncover a complex interplay of emissions and atmospheric processing of carbonaceous aerosols in the IGP. Image 1 • Bulk BrC and HULIS fractions were enriched during biomass burning (BB) periods. • HULIS-n dominated (73–81%) the seasonal total HULIS + HP-WSOM absorption at 365 nm. • Polar functional groups from atmospheric photooxidation prevailed in summer. • Strong signatures of aromatic phenols were observed in BB-influenced samples. • Marine, secondary formation, and BB sources dominated seasonal organic aerosol. We use multiple spectroscopic approaches to characterize the sources and atmospheric processing of aerosol brown carbon and humic-like substances in the eastern Indo-Gangetic Plain, India. We find that secondary formation, marine and biomass burning sources constrain seasonal organic aerosol composition and its optical properties in this region. [ABSTRACT FROM AUTHOR]

South-west coast of India has a history of using pesticidal persistent organic pollutants (POPs) particularly endosulfan until aerial spraying was banned during early 2000. Since soil acts as a repository for such pesticidal persistent organic contaminants, we have monitored residues of seventeen organochlorine pesticides (OCPs) in the surface soil samples from the agricultural, coastal, and backwater transects along the south-west coast of India. OCPs concentration in soil were in the order agricultural > coastal > backwaters transects. Endrins, hexachlorocyclohexane (HCH) and heptachlors were among the dominant OCPs quantified in this study. Dominance of metabolites such as dichlorodiphenyldichloroethylene (DDE), dichlorodiphenyldichloroethane (DDD) and endosulfan sulfate indicates past usage. All the OCPs were dominant in the agricultural transect where plantations/agricultural activities are prevalent. In some specific sites, traces of HCH isomers showed ongoing usage of technical HCH in those sites contradicting the ban in agricultural sector. Backwater sites which are background locations showed positive correlation between soil organic carbon and soil borne OCPs thereby indicating an aged source possibly due to the short/long atmospheric transport from the site of application. Based on the policies regarding control, prevention and other measures for the management of pesticides in Kerala, it was concluded that the implementation on the ground level and the legal framework should be strengthened to prevent further illegal use of the banned pesticides. Image 1 • Maximum OCPs were observed in the agricultural transect over coastal and backwaters transects. • About 60% of endosulfan residues were from Kasargod district where it was previously used in cashew plantations. • Pesticidal residues in pristine backwaters locations might be due to redistribution from past usage. [ABSTRACT FROM AUTHOR]

• We calculated the Excess Lifetime Cancer Risk (ELCR). • Diagnostic Ratio Analysis (DRA) & Principal component analysis (PCA) has demonstrated to better understand source apportionment. • Backward trajectory calculations were performed to predict the air parcel trajectories. • DBahA and BaP were the responsible for high health risk among all PAHs. Occurrence and persistence of Polycyclic Aromatic Hydrocarbons (PAHs) in the environment pose a serious human health risk. In this study, the sources and characteristics of 16 Polycyclic Aromatic Hydrocarbons (PAHs) associated with the emission of particulate matter (PM) from semi-urban, urban, and rural sections of Jamshedpur City, India was investigated using advanced gas chromatography. The results of sampling conducted during winter and summer seasons suggest that the total PAHs average concentration level were higher in the winter season than the concentration level in the summer season. During the winter season, the average concentration of total PAHs from semi-urban, urban, and rural sites were found to be 47.73 ± 10.65, 37 ± 9.56, and 109.06 ± 18.21 ng/m3 respectively while in summer season, the concentration was observed to be 39.61 ± 6.87, 81.14 ± 13.30 and 36.33 ± 9.97 ng/m3 over semi-urban, urban and rural site respectively. Of all the PAHs, Phenanthrene (Phe) was among the most abundant PAH in both winter and summer seasons over the entire study site. Diagnostic Ratio Analysis (DRA) & Principal component analysis (PCA) demonstrated that major emission sources of PAHs were; the vehicles, petrogenic, and biomass and coal combustion sources over semi-urban, urban, and rural site. BaP & DBahA were used as the surrogate compounds in assessing PAHs health risk. The Excess Lifetime Cancer Risk (ELCR) value over the semi-urban, urban, and rural site was calculated as 10.25 × 10−6, 23.09 × 10−6 and 18.86 × 10−6 respectively. [ABSTRACT FROM AUTHOR]

Krypton-85 activity concentrations in surface air have been measured at Darwin, which is located in northern Australia and is influenced by seasonal monsoonal activity. Measurements between August 2007 and May 2010 covered three wet seasons. The mean activity concentration of krypton-85 measured during this period was 1.31±0.02Bqm(-3). A linear model fitted to the average monthly data, using month and monsoon as predictors, shows that krypton-85 activity concentration measured during the sampling period has declined by 0.01Bqm(-3) per year. Although there is no statistically significant difference in mean activity concentration of krypton-85 between wet and dry season, the model implies that activity concentration is higher by about 0.015Bqm(-3) during months influenced by the monsoon when a north westerly flow prevails. Backward dispersion runs using the Lagrangian particle dispersion model Hysplit4 highlight possible source regions during an active monsoon located deep in the northern hemisphere, and include reprocessing facilities in Japan and India. However, the contribution of these facilities to krypton-85 activity concentrations in Darwin would be less than 0.003Bqm(-3)., (Crown Copyright © 2013. Published by Elsevier Ltd. All rights reserved.)