Arideep Mukherjee

Pollution Response Score of Tree Species in Relation to Ambient Air Quality in an Urban Area

Multivariate statistical techniques were employed on twelve leaf traits in four selected common tree species (Mangifera indica L., Polyalthia longifolia Sonn., Ficus benghalensis L. and Psidium guajava L.) to evaluate their responses with respect to major air pollutants in an urban area. Discriminant analysis (DA) identified chlorophyll/carotenoid ratio, leaf dry matter content, carotenoids, net water content and ascorbic acid as the major discriminating leaf traits, which varied maximally with respect to the pollution status. Pollution response score (PRS), calculated on the basis of discriminate functional coefficient values, increased with an increase in air pollution variables for all the tested species, with the highest increase in P. longifolia and the lowest in F. benghalensis. The study highlights the usefulness of DA for evaluation of plant specific traits and PRS for selection of tolerant species.

Use of GLM approach to assess the responses of tropical trees to urban air pollution in relation to leaf functional traits and tree characteristics

Responses of urban vegetation to air pollution stress in relation to their tolerance and sensitivity have been extensively studied, however, studies related to air pollution responses based on different leaf functional traits and tree characteristics are limited. In this paper, we have tried to assess combined and individual effects of major air pollutants PM10 (particulate matter ≤ 10 µm), TSP (total suspended particulate matter), SO2 (sulphur dioxide), NO2 (nitrogen dioxide) and O3 (ozone) on thirteen tropical tree species in relation to fifteen leaf functional traits and different tree characteristics. Stepwise linear regression a general linear modelling approach was used to quantify the pollution response of trees against air pollutants. The study was performed for six successive seasons for two years in three distinct urban areas (traffic, industrial and residential) of Varanasi city in India. At all the study sites, concentrations of air pollutants, specifically PM (particulate matter) and NO2 were above the specified standards. Distinct variations were recorded in all the fifteen leaf functional traits with pollution load. Caesalpinia sappan was identified as most tolerant species followed by Psidium guajava, Dalbergia sissoo and Albizia lebbeck. Stepwise regression analysis identified maximum response of Eucalyptus citriodora and P. guajava to air pollutants explaining overall 59% and 58% variabilitys in leaf functional traits, respectively. Among leaf functional traits, maximum effect of air pollutants was observed on non-enzymatic antioxidants followed by photosynthetic pigments and leaf water status. Among the pollutants, PM was identified as the major stress factor followed by O3 explaining 47% and 33% variabilitys in leaf functional traits. Tolerance and pollution response were regulated by different tree characteristics such as height, canopy size, leaf from, texture and nature of tree. Outcomes of this study will help in urban forest development by selection of specific pollutant tolerant tree species and leaf traits, which is suitable as air pollution mitigation measure.

Assessment of Seasonal and Site Specific Variations in Soil Physical, Chemical and Biological Properties around Opencast Coal Mines

Coal mining activities adversely affect the soil quality around open cast coal mines. Therefore, a study was conducted to assess the seasonal and site specific variations in physical, chemical and biological properties of soil collected at different distances from mining areas in Jharia coal field, India. Sites near coal mines showed significantlyhigherbulk density, soil temperature, electrical conductivity, sulphate and heavy metalcontentsand significantly lower water holding capacity, porosity, moisture content, soil pH, total nitrogen and available phosphorus contents in soil compared to distant sites throughout the year. However,biological properties showed site specific as well as seasonal pattern. Soil microbial biomass C andN, microbialbiomass C/N ratio and soil respiration were highest during rainy and lowest during summer season with minimum values in soil near coal mining areas. Soil quality index showed significant influence of heavy metal contents on biological properties of soil.

The influence of urban stress factors on responses of ground cover vegetation

A comprehensive study was conducted to evaluate the effects of ambient air pollution, land use, and soil properties on ground cover vegetation in the urban area of Varanasi city, situated in the Indo Gangetic Plain of India. Twelve leaf functional traits were assessed on eight most dominant herbaceous species belonging to four angiospermic families in three different land uses with varying air pollution loads and soil properties. Particulate matter (PM10 and TSP), gaseous pollutants (SO2, NO2, and O3), land uses (built-up area, shrub, and grass cover), and soil properties showed significant variability among the land uses. Air pollution was identified as the major stress factor which influenced leaf functional traits of ground cover vegetation followed by soil properties and land uses. Among the plants, Croton sparsiflorus was found to be the most responsive plants to all the factors. Plants responded differently under varying environmental factors as Euphorbia hirta was maximally influenced by air pollution, whereas the effect of land use was maximum in C. sparsiflorus. Influence of soil properties was highest in Digitaria ciliaris and Scoparia dulcis. All the environmental factors in combination maximally influenced non-enzymatic antioxidants (ascorbic acid and polyphenolics) followed by photosynthetic pigments among the different leaf functional traits. Among the environmental factors, NO2 and PM were identified as the most influencing factors regulating leaf functional traits followed by K level in soil and shrub cover. It can be concluded that responses of different leaf functional traits of ground cover vegetation varied with different environmental factors and responses were mostly species specific.

Intra-urban variability of ozone in a tropical city—characterization of local and regional sources and major influencing factors

Tropospheric ozone (O3), a secondary air pollutant, was assessed to evaluate the intra-urban variability of O3, its local and distant sources, and the influence of O3 precursor gases and meteorological variables on seasonal and temporal trends of O3 from 2013 to 2017 in a tropical urban city located in the middle Indo-Gangetic Plains of India. Passive samplers and data from real-time air quality monitoring station were considered. Trajectory statistical models, multivariate statistical methods, and geographic information system were further used to identify spatial-temporal variability and source apportionment. O3 concentrations showed significant intra-urban variability with higher concentrations in suburban or background regions of the city, which were mostly attributed to the transport of O3 at high wind speed from distant and rural areas away from the city, while lower concentrations in traffic and commercial areas were due to titration of O3 by nitric oxide (NO). Variations in meteorological variables (temperature, relative humidity, wind speed) and planetary boundary layer height were responsible for seasonal variations in O3 concentrations. Long-range and regional transport of O3 and its precursors such as volatile organic compounds and NOx from the northwestern and eastern directions of the city significantly influenced O3 variability with distinct seasonal patterns. A negative trend in O3 levels was recorded during the study period which may be due to increase in NOx emission in the city. The observed outcomes suggest significant intra-urban variability of O3 in the city which is influenced by traffic as well as by distant and local sources.

Heavy Metal Accumulation Potential and Tolerance in Tree and Grass Species

Heavy metals (HM) are nondegradable, persistent, and toxic elements. Heavy metal contamination is a global concern and a major health hazard throughout the world. However, plants have evolved different mechanisms to combat these stresses and even have potential to accumulate them in large quantity. Natural flora has differential ability to metal tolerance with some plants showing induced tolerance at metal-enriched medium, whereas others find it difficult to sustain. Bioaccumulation potential of trees and grasses will be assessed based on peer-reviewed publications. Plants will be classified based on their accumulation potential of different heavy metals. Metal accumulation ability in plants and sources of heavy metals will be assessed for different regions of the world. Anthropogenic input of heavy metals from different sources significantly affects the biogeochemical cycling. Heavy metal depositions considerably affect the plant response. Heavy metal tolerance, uptake, and accumulation in different parts of the plant and possible metal-chelating compounds and their role in metal chelation in trees and grasses will be discussed. Morphological, physiological, biochemical, and molecular biomarkers of heavy metal tolerance or sensitivity among the trees and grasses will be correlated with bioaccumulation potential and heavy metal tolerance. This article will provide a broad overview of higher plant abilities and tolerance capabilities in heavy metal accumulation.