ABSTRACT
The direct effect of pandemic induced lockdown (LD) on environment is widely explored, but its secondary impacts remain largely unexplored. Therefore, we assess the response of surface greenness and photosynthetic activity to the LD-induced improvement of air quality in India. Our analysis reveals a significant improvement in air quality marked by reduced levels of aerosols (AOD, -19.27%) and Particulate Matter (PM 2.5, -23%) during LD (2020)from pre-LD (March-September months for the period 2017-2019). The vegetation exhibits a positive response, reflected by the increase in surface greenness [Enhanced Vegetation Index (EVI, +10.4%)] and photosynthetic activity [Solar Induced Fluorescence (SiF, +11%)], during LD from pre-LD that coincides with two major agricultural seasons of India; Zaid (March-May) and Kharif (June-September). In addition, the croplands show a higher response [two-fold in EVI (14.45%) and four-fold in SiF (17.7%)] than that of forests. The prolonged growing period (phenology) and high rate of photosynthesis (intensification) led to the enhanced greening during LD owing to the reduced atmospheric pollution. This study, therefore, provides new insights into the response of vegetation to the improved air quality, which would give ideas to counter the challenges of food security in the context of climate pollution, and combat global warming by more greening.
ABSTRACT
Atmospheric formaldehyde (HCHO) has significant adverse health effects at higher concentrations. It is an unstable and inflammable organic compound, and is an index for atmospheric pollution. Although the ambient HCHO is due to methane oxidation, the localised enhancement in HCHO is mostly from the emissions of non-methane volatile organic compounds (NMVOCs). Therefore, assessment of spatial and temporal changes in NMVOCs are key for monitoring air quality and climate change. Here, we analyse two decades of atmospheric HCHO measurements and investigate the HCHO sources in India using satellite observations in 1997–2020. The measurements show very high HCHO concentrations in the Indo-Gangetic Plain (IGP), and south and east India, about 8–12 × 1015 molec. cm−2. The northwest region shows moderate concentrations, but Kashmir and northern regions of northeast show very small values of about 1–2 × 1015 molec. cm−2. Our analyses reveal significant increase in HCHO over India in all seasons, with the highest trends during March–May, about 0.3–0.5 × 1015 molec. cm−2 yr−1;suggesting the spread of pollution even to rural regions. Many ports and mining areas exhibit high positive HCHO trends, which also show new source regions and transport pathways of pollution. Furthermore, the analyses for the COVID-19 lockdown period expose significant contributions from sources other than anthropogenic origin (e.g. biogenic and pyrogenic). Therefore, this study indicates the need of new policy interventions for controlling Volatile Organic Compound (VOC) pollution in rural and urban India, and at the international seaports of Indian Ocean.
ABSTRACT
COronaVIrus Disease (COVID) 2019 pandemic forced the countries to go into complete lockdown and India went on complete lockdown from March 24th – June 8th 2020. In order to understand the possible implications of lockdown, we analyse the long-term distribution of Net Primary Productivity (NPP) in the north Indian Ocean (NIO) and the factors that influence NPP directly and indirectly, for the period 2003–2019 and 2020 separately. There exists a seasonal cycle in the correlation between AOD, Chlorophyll–a (Chl–a) and NPP in agreement with the seasonal transport of aerosols and dust into these oceanic regions. In Arabian Sea (AS), the highest Chl–a (0.58 mg/m3), NPP (696.57 mg/C/m2/day) and AOD (0.39) are observed in JJAS (June, July, August and September) and In BoB, maximum Chl–a (0.48 mg/m3) and NPP (486.39 mg/C/m2/day) are found in JJAS and AOD (0.27) in MAM (March, April and May). The interannual variability of Chl–a and NPP with wind speed and Sea Surface Temperature (SST) is also examined, where the former has a positive and the latter has a negative feedback to NPP. The interannual variability of NPP reveals a decreasing trend in NPP, which is interlinked with the increasing trend in SST and AOD. The analysis of wind, SST, Chl–a, and AOD for the pre-lockdown, lockdown, and post lockdown periods of 2020 is used to understand the impact of COVID-19 lockdown. The assessment shows the reduction in AOD, decreased wind speeds, increased SST and reduced NPP during the lockdown period as compared to the pre-lockdown, post-lockdown and climatology. The year 2018 is also analysed separately during these periods to understand the influence of lockdown in NIO. This analysis will help to understand the impact of aerosols on the ocean biogeochemistry, nutrient cycles in the ocean biogeochemical models, and to study the effects of climate change on ocean ecosystems.