Biomonitoring of metallic air pollutants in unique habitations of the Brahmaputra Valley using moss species-Atrichum angustatum: spatiotemporal deposition patterns and sources.

In this paper, we have evaluated the bioaccumulation of metals by Atrichum angustatum, which is a readily available moss species in the Brahmaputra valley, India. A systematic investigation of metallic pollutants in the atmosphere was carried out using A. angustatum as a biomonitor collected from representative locations during three seasons viz. winter, pre-monsoon, and monsoon (n = 99) during the year 2018. The study was done in four unique habitations of the Brahmaputra Valley, which were further divided into three landuse areas: residential, roadside, and industrial. The highest accumulations were seen against Ca, Mg, Zn, and Fe. The calculated contaminant factors and ecological risk indices suggest that the Brahmaputra Valley is mostly contaminated by Cr, Zn, Cu, Ni, and Pb, and these metals pose a maximum ecological risk. The accumulation trend of metallic pollutants was site-specific, but most metals showed positive seasonal accumulation. A significant difference in spatial and seasonal accumulation patterns was specific to metal species. Principal component analysis (PCA) and inter-species correlations revealed that the air quality of Brahmaputra valley was greatly affected by coal burning, vehicular emission, biomass burning, road dust, and crustal dust. Finally, the study led us to the conclusion that A. angustatum can serve as a potential biomonitor for metallic pollutants.

Seven-year study of monsoonal rainwater chemistry over the mid-Brahmaputra plain, India: assessment of trends and source regions of soluble ions.

This work is a 7-year study of monsoonal rainwater chemistry (n = 302), over mid-Brahmaputra plain during 2012 to 2018. The samples were analyzed for major chemical parameters viz. pH, electrical conductivity (EC), and ions (SO42-, NO3-, Br-, Cl-, F-, Mg2+, Ca2+, K+, NH4+, Na+, and Li+) to assess the chemistry. The mean pH of rainwater varied among the years, which was maximum in 2018 (6.18 ± 0.72) and minimum in the year 2014 (5.39 ± 0.54), and the variations were significant at p < 0.0001. Ridgeline plots were drawn to visualize interannual variations, which revealed that Ca2+ was the dominant cation in the early years, whereas NH4+ prevailed in the latter years. Mann-Kendall analysis and Sen's slope statistical tests were employed, and it was found that all the ions showed positive S values indicating increasing trends. Enrichment factors (EF) of K+, SO42-, and NO3- were found to be high with respect to both soil and seawater suggesting the influence of emissions from fossil fuel and biomass burning in the chemistry of rainwater. Principal component analysis (PCA) was applied to identify the sources of rain constituents, and five factors were obtained explaining crustal dust, biomass burning, fossil fuel combustion, agricultural emissions, and coal burning as possible sources. Airmass back trajectory clusters and Potential Source Contribution Function (PSCF) were computed by application of HYbrid Single-Particle Lagrangian Integrated Trajectory model to appreciate the terrestrial influence on the chemistry. The results indicated inputs from both local and regional dust and anthropogenic constituents that influenced the monsoonal rainwater chemistry over Brahmaputra Valley.

Particulate matter exposure in biomass-burning homes of different communities of Brahmaputra Valley.

Biomass burning for cooking prevalent in the developing countries is an issue which has been a concern for the past several decades for the noxious emissions and subsequent effects on the health of women and children due to the exposure of particulate matter (PM) and other gases. In this study, PM (PM1, PM2.5, and PM10) were measured in biomass-burning households for different communities of Brahmaputra Valley region northeast India by a 31-channel aerosol spectrometer. The levels of emission of PM in the case of different community households were found to be significantly different. Also, the emission characteristics of different cooking time of the day were found to be different across communities. The emission levels in the biomass-burning households were compared with emission in household using "clean" LPG fuel, and it was found that the biomass fuels emitted 10-12 times more PM2.5 and 6-7 times more PM10. The number densities of the emission were found to be more with smaller sizes of particulates which could explain why such biomass-burning emissions can pose with greater health risks. The exposure doses were calculated and were found to be about three times higher in biomass-burning houses than "clean" LPG fuel. It is important to note that the exposure from biomass burning while cooking has a gender perspective. The woman of the house generally takes care of the activities in the kitchen and get exposed to the noxious PM and the gases. Children often accompany their mothers and face the same fate.

Ambient ozone over mid-Brahmaputra Valley, India: effects of local emissions and atmospheric transport on the photostationary state.

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.

Anatomical, physiological, and chemical alterations in lichen (Parmotrema tinctorum (Nyl.) Hale) transplants due to air pollution in two cities of Brahmaputra Valley, India.

The lichen species Parmotrema tinctorum (Nyl.) Hale was transplanted in two cities-Tezpur (small) and Guwahati (large)-of the Brahmaputra Valley to assess the impact of air pollution on the anatomy and physiology, and accumulation of pollutants. Significant damage to the anatomy was observed in samples, and the degree of damage was found to be higher in the transplants of the larger city. In the lichen transplants from locations having high traffic density, the total chlorophyll content was found to fall; on the contrary, electrical conductivity was found to be higher. The exposed-to-control ratio showed severe accumulation of Cd in all the transplants. Elements such as Cd, Pb, and Zn were found to be enriched in all the lichen samples from both Guwahati as well as Tezpur city. Besides, Cr, Cu, K, and Ni were also realized to be enhanced to a moderate extent. The correlations of indicator metal species pairs showed that anthropogenic influence was quite clear.

Soil PAHs against varied land use of a small city (Tezpur) of middle Brahmaputra Valley: seasonality, sources, and long-range transport.

This study reports soil PAHs from a small city (Tezpur) of the mid-Brahmaputra Valley. The soil PAHs has been assessed from representative land use using detailed protocol of extracting, cleaning, and quantitative analysis by HPLC technique. The concentrations of PAHs showed minimum spatial variability and yet showed strong seasonal variability, which could be typical of small cities having weak local source strengths. On examining the air mass reaching the region, it appeared that there has been explicit effect of long-range transport. The HYSPLIT back trajectories reaching the study area during different seasons showed variations in terms of their origins and transport pathways. This might have led to differential long-range transport of PAHs, which is reflected in the seasonal variabilities of the concentrations of PAHs. The seasonal variations were much profound with the highest ΣPAHs concentration during post-monsoon (7961 ng g-1) followed by pre-monsoon (2414 ng g-1) and monsoon (773 ng g-1) season. The toxicity of the PAHs was examined as BaP equivalent (BaPeq) concentrations, which were found to be on the lower side as compared to the studies conducted elsewhere. The percentage contribution of 3- and 4-ring compounds was found to be greater. An attempt also was made to apportion the sources of the PAHs by application of diagnostic ratios, principal component analysis-multiple linear regression (PCA-MLR) and hierarchal cluster analysis (HCA), which revealed that coal and biomass burning and vehicular emissions are the major contributors to the PAHs load in Tezpur city.

Microzonation, ecological risk and attributes of metals in highway road dust traversing through the Kaziranga National Park, Northeast India: implication for confining metal pollution in the national forest.

Despite the abundant literature on metal contamination through road dust (RD) in urban/suburban and residential/highway regions, the RD of highways traversing through the Kaziranga National Park, NE India, has not been studied and lacks baseline data. The objective of the present study was to ascertain the possibility of highway microzonation based on temporal and spatial variability of metal pollution level and ecological risk. It was found that the RD contains an average content of (1.7-33.5 mg/kg) for Cd, Co, Cu and Pb and (121-574 mg/kg) for Ni, Zn, Cr and Mn across the highway passing through the national forest attributed by various sources. The study revealed three possible microzones present in the studied highway NH-37 based on spatial trend of metal as well as human interference. An attempt was made to understand the possible source of metals by principal component analysis, and four sources were identified: Three were of vehicular origin, and another was related to road surface and subsurface condition. The use of noise barrier walls as an effective measure to control the translocation of RD from one place to other was recommended to reduce the hostile effects of metal accumulation in the sensitive ecosystem. Thus, the study suggested and necessitated micronizing the system based on human interference level, ecological risk factors, spatial variability of pollutants and traffic pattern for their efficient management and conservation.