Articles written in Journal of Earth System Science

    • Major ion chemistry of the Son River, India: Weathering processes, dissolved fluxes and water quality assessment

      Chinmaya Maharana Sandeep Kumar Gautam Abhay Kumar Singh Jayanth K Tripathi

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      River Son, draining diverse lithologies in the subtropical climate of the peninsular sub-basin of the Ganga basin, is one of the major tributaries of the Ganga River. The chemistry of major ions in the surface water of the Son River was studied in detail to determine various source(s) and processes controlling its water chemistry, seasonal and spatial variations in water chemistry, dissolved fluxes and chemical denudation rate (CDR). The study shows that Ca2+, Mg2+ and HCO$^{-}_{3}$ are major ionic species in the river water. Most of the measured parameters exhibit a relatively lower concentration in the post-monsoon as compared to pre-monsoon season. The water chemistry highlights the influence of continental weathering aided by secondary contributions from ground water, saline/alkaline soils and anthropogenic activities in the catchment. Results also reflect the dominance of carbonate weathering over silicate weathering in controlling water composition. The Son River delivers about 4.2 million tons of dissolved loads annually to the Ganga River, which accounts for $\sim$6% of the total annual load carried by the Ganga River to the Bay of Bengal. The average CDR of the Son River is 59.5 tons km−2 yr−1, which is less than the reported 72 tons km−2 yr−1 of the Ganga River and higher than the global average of 36 tons km−2 yr−1. The water chemistry for the pre-monsoon and post-monsoon periods shows a strong seasonal control on solute flux and CDR values. The water chemistry indicates that the Son River water is good to excellent in quality for irrigation and also suitable for drinking purposes.

    • Metal contamination of agricultural soils in the copper mining areas of Singhbhum shear zone in India

      Soma Giri Abhay Kumar Singh Mukesh Kumar Mahato

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      The study was intended to investigate the heavy metal contamination in the agricultural soils of the copper mining areas in Singhbhum shear zone, India. The total concentrations of the metals were determined by inductively coupled plasma-mass spectrometer (ICPMS). Pollution levels were assessed by calculating enrichment factor (EF), geo-accumulation index (Igeo), contamination factors (CF), pollution load index (PLI), Nemerow index and ecological risk index (RI). The metal concentrations in the soil samples exceeded the average shale values for almost all the metals. Principal component analysis resulted in extraction of three factors explaining 82.6% of the data variability and indicated anthropogenic contribution of Cu, Ni, Co, Cr, Mn and Pb. The EF and Igeo values indicated very high contamination with respect to Cu followed by As and Zn in the agricultural soils. The values of PLI, RI and Nemerow index, which considered the overall effect of all the studied metals on the soils, revealed that 50% of the locations were highly polluted with respect to metals. The pollution levels varied with the proximity to the copper mining and processing units. Consequently, the results advocate the necessity of periodic monitoring of the agricultural soils of the area and development of proper management strategies to reduce the metal pollution.

    • Fluvial geochemistry of Subarnarekha River basin, India

      Abhay Kumar Singh Soma Giri Aaditya Chaturvedi

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      The fluvial geochemistry of the Subarnarekha River and its major tributaries has been studied on a seasonal basis in order to assess the geochemical processes that explain the water composition and estimate solute fluxes. The analytical results show the mildly acidic to alkaline nature of the Subarnarekha River water and the dominance of Ca$^{2+}$ and Na$^{+}$ in cationic and HCO$_{3}^{-}$ and Cl$^{-}$ in anionic composition. Minimum ionic concentration during the monsoon and maximum concentration in the pre-monsoon seasons reflect concentrating effects due to decrease in the river discharge and increase in the base flow contribution during the pre-monsoon and dilution effects of atmospheric precipitation in the monsoon season. The solute acquisition processes are mainly controlled by weathering of rocks, with minor contribution from marine and anthropogenic sources. Higher contribution of alkaline earth (Ca$^{2+} + $Mg$^{2+}$) to the total cations (TZ$^{+}$) and high (Na$^{+}+$K$^{+}$)/Cl$^{-}$, (Na$^{+}+$K$^{+}$)/TZ$^{+}$, HCO$_{3}^{-}$/(SO$_{4}^{2-}+$Cl$^{-}$) and low (Ca$^{2+}+$Mg$^{2+}$)/(Na$^{+}+$K$^{+}$) equivalent ratios suggest that the Subarnarekha River water is under the combined influence of carbonate and silicate weathering. The river water is undersaturated with respect to dolomite and calcite during the post-monsoon and monsoon seasons and oversaturated in the pre-monsoon season. The pH–log H$_{4}$SiO$_{4}$ stability diagram demonstrates that the water chemistry is in equilibrium with the kaolinite. The Subarnarekha River annually delivered 1.477$\times 10^{6}$ ton of dissolved loads to the Bay of Bengal, with an estimated chemical denudation rate of 77 ton km$^{-2}$ yr$^{-1}$. Sodium adsorption ratio, residual sodium carbonate and per cent sodium values placed the studied river water in the ‘excellent to good quality’ category and it can be safely used for irrigation.

    • COVID-19 lockdown induced air pollution reduction over India: A lesson for future air pollution mitigation strategies


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      Air pollution is one of the biggest problems worldwide and needs to be addressed potentially with the implementation of updated stringent policies and legislative laws. The nationwide lockdown imposed to prevent the COVID-19 outbreak, has given us a unique opportunity to understand the contribution of anthropogenic emissions to the total atmospheric pollutant burden on a global as well as regional scale. Thus, in the present study, we try to investigate the impact of COVID-19 induced lockdown on common ambient air pollutants (i.e., PM$_{2.5}$, NO$_2$, and SO$_2$) concentration over 22 cities in India using in-situ measurement under a network of Centre Pollution and Control Board (CPCB). A significant reduction in the mean mass concentration of all the studied air pollutants (i.e., PM$_{2.5}$, NO$_2$, and SO$_2$) (nearly 10–70%) is found during different phases of lockdown which reached within the National Ambient Air Quality Standard (i.e., NAAQS). The reduction in studied air pollutants is more prominent during the first phase of lockdown (mainly NO$_2$) which could be due to the complete shutdown of industrial activities. The outcome of the present study will be helpful for policymakers to design cost-effective and accurate air pollution mitigation strategies for the development of a sustainable environment. The study also suggests that well-planned short-term and periodical lockdown could be an alternative effective tool of air pollution mitigation.

    • Measurements of limb-darkening effect and solar radiation during the partial solar eclipse of 21 June 2020 at Varanasi


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      In this study, we have for the first time discussed the effect of a partial solar eclipse on limb-darkening effect, incoming solar radiation and atmospheric temperature at the surface with the help of a solar telescope with the back-end instrument as the charge-coupled device camera and data of net radiometer installed at the Department of Physics, Banaras Hindu University, Varanasi, India. We have also calculated the eclipse parameters, magnitude and obscuration. A partial eclipse occurred at Varanasi on 21 June 2020 from 10:30:51 am to 02:04:01 pm (IST) for 3 h 33 min. The path of this rare solstice ring of fire was of long duration. Observation of six phases of the partial solar eclipse was recorded and it showed a variation in the intensity over the sun’s diameter from one limb to another at different phases of the eclipse. We also estimated the limb-darkening coefficient for six phases of the partial solar eclipse. The average value of the solar limb-darkening coefficient was found to be about 0.61. The observed values of the limb-darkening coefficient; incoming solar radiation and atmospheric temperature at the surface are consistent with earlier studies.

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