Pre-monsoon Season Research Articles

Investigation of Tropical Cyclones in the North Indian Ocean and the Linkage to Extreme Weather Events over Sri Lanka

Heavy rainfall due to tropical cyclones (TCs) in the North Indian Ocean (NIO) adversely impacts nations frequently. Though extensive research has focused on TCs in the NIO, less attention has been given to the connection between TCs and extreme events in Sri Lanka. This study examined atmospheric characteristics during sixteen extreme events, focusing on linkages between TCs, the Indian Ocean Dipole (IOD), and mechanisms behind heavy rainfall associated with TCs over Sri Lanka. The results showed that in the pre-monsoon period, TCs move northward with high water vapor (WV) content accumulated in the Southern Hemisphere. This main WV flow over the equatorial Indian Ocean (EIO) is connected with TCs, causing considerable damage in the southwestern part of Sri Lanka. During negative IOD years, strong westerly winds create cyclonic circulations on either side of the equator. Conversely, during the post-monsoon period, the IOD phase has no significant effect. TCs generally followed westward tracks, supported by winds from the Northern Hemisphere, and caused heavy rainfall in the Eastern, Northern, and Northcentral provinces in Sri Lanka. These TCs are isolated from the main WV flow over EIO. Such observed common characteristics during pre-monsoon and post-monsoon seasons are key factors contributing to extreme rainfall in Sri Lanka.

The monsoon-groundwater nexus, impacts and adaptation strategies in the northern part of Chennai region, South India

The variations in groundwater quality and their influence on hydrochemical and microbial properties in the metropolitan cities of North Chennai have been scientifically examined in an attempt to comprehend the effects of urbanization. For this ongoing investigation, 50 groundwater samples from surface bore wells were collected in and around north Chennai, South India, during the pre-monsoon (PRm) season in June 2022 and 50 samples during post-monsoon (POm) in January 2023. Southeast of the desired extent, where urban enclaves predominate, has elevated salinity (12,500 mg/L) and electrical conductivity (EC) of 21,200 μS/cm. The predominant types shown in the Piper and Chadha models were sodium-chloride (Na-Cl). Additionally, the Gibbs diagram revealed the observation of evaporation dominance. The interaction between freshwater and seawater has been shown using ionic ratio analysis. A majority of the sample locations indicated the levels of standard plate count (SPC) and total coliforms (TC) contamination in the groundwater were above allowable limits (WHO). There was a slight improvement in groundwater quality during the post-monsoon session suggesting to a possible effect from recently recharged groundwater. In general, the groundwater quality of the research area is impacted by lithological changes, land use, and urban development. Water quality study may be useful in identifying potential health concerns and notify decisions about water management and treatment policies.

Spring tropical cyclones modulate near-surface isotopic compositions of atmospheric water vapour in Kathmandu, Nepal

Abstract. While westerlies are recognized as a significant moisture transport in Nepal during the pre-monsoon season, precipitation is also attributed to moisture from cyclones originating in the Bay of Bengal (BoB) or the Arabian Sea (AS). Tropical cyclones exhibit negative isotopic values in both precipitation and atmospheric water vapour; however, the factors influencing isotopic fractionation during tropical cyclones remain poorly understood. We present the results of continuous measurements of the isotopic composition of atmospheric water vapour (δ18Ov, δDv, and d-excessv) in Kathmandu from 7 May to 7 June 2021 during two pre-monsoon cyclones: cyclone Tauktae, formed over the Arabian Sea, and cyclone Yaas, formed over the Bay of Bengal. Our study reveals that tropical cyclones originating from the BoB and the AS during the pre-monsoon season modulate isotopic signals of near-surface atmospheric water vapour in Nepal. Comparing conditions before and after, we observed a significant depletion of δ18Ov and δDv during both cyclones, attributed to changes in moisture sources (local vs. marine). Convective activity plays a pivotal role in the variability of δ18Ov and δDv during both cyclones, confirmed by the spatial variations of outgoing longwave radiation (OLR) and regional precipitation during both cyclones. We also found a significant negative correlation between δ18Ov and/or δDv and rainfall amount along the trajectories during cyclone Tauktae, probably resulting from integrated upstream processes linked to the earlier Rayleigh distillation of water vapour via rainfall rather than local rainfall. The decrease in δ18Ov and/or δDv during cyclone Yaas is associated with the intensified convection and moisture convergence at the measurement site, while the lower cloud top temperatures (CTTs) and lower cloud top pressure (CTP) during intense convection contribute to higher d-excessv values during the final stage of cyclone Yaas. This characteristic is missing during cyclone Tauktae. Our results shed light on key processes governing the isotopic composition of atmospheric water vapour in Kathmandu with implications for the monsoon moisture transport and paleoclimate reconstructions of tropical cyclone activity.

Analysis of Rainfall Trend in North Interior Karnataka (NIK) Meteorological Subdivision of Karnataka by Non-Parametric Methodologies

The present study analyzed the trend in the month-wise, seasonal and annual rainfall employing three non-parametric tests viz. Mann-Kendall (M-K), Modified Mann-Kendall (MM-K) tests and Sen’s slope estimator for North Interior Karnataka (NIK) meteorological subdivision of Karnataka using 60 years (1960-2019) rainfall data. The M-K test results revealed that there is no monotonic trend in all data sets which indicates that there may exist the influence of serial correlation in the rainfall data. The MM-K test was applied to rainfall data of the NIK subdivision, the result of the test revealed that January, February, March and August months have a monotonic increasing trend whereas April, May, July and September months have a monotonic decreasing trend whereas June, October, November and December have no monotonic trend in monthly rainfall data. The winter season has a monotonic increasing trend, monsoon and post-monsoon seasons have a monotonic decreasing trend, and the pre-monsoon season has no monotonic trend in seasonal rainfall data. The MM-K test statistic (Tau) value for the NIK (-0.12) subdivision was found to be significant and negative indicating that there is a monotonic decreasing trend. Larger negative Sen’s slope values for NIK (-1.40) subdivision indicate the high decreasing rate of change of rainfall for annual rainfall data. Therefore, to know the trend in rainfall data most accurately in the presence of outliers and serial correlation, the Modified Mann-Kendall (MM-K) test and Sen’s slope estimator are recommended instead of Mann-Kendall (M-K) and Sen’s slope estimator.

Interdecadal variability of the pre-monsoon cyclone characteristics over the Bay of Bengal

The low-pressure systems intensified to cyclones prior to the onset of the Indian summer monsoon season over the North Indian Ocean are referred to as pre-monsoon season (PMS) cyclones. Climate change is amplifying the pre-monsoon cyclone landscape, fostering more frequent and intense storms with altered tracks, resulting in heightened risks for coastal communities and economies. This study investigates the interdecadal variations in tropical cyclone and key large-scale atmospheric parameters that influence the characteristics of cyclones, including track, frequency over the Bay of Bengal (BoB) during the pre-monsoon season from 60 years of data. The large-scale atmospheric parameters are analyzed by calculating climatological anomalies. It is noted that the frequency of cyclones making landfall over the eastern Indian coastal landmass has increased in the recent decade compared to the past five decades. Compared to the past fifty years, the percentage frequency has increased in the recent ten years by 50%. At the low level, stronger easterlies are dominant and upper-level jet streams shift to lower latitudes, indicating that the path of cyclones has shifted from the north (N)-northeast (NE) to the northwest (NW), i.e. towards the east Indian coastal landmass, over the recent decade. In contrast to the previous five decades, an unusual low-pressure region has emerged over the NW India and Pakistan regions, creating a favorable path for cyclones moving towards the Indian region in recent decade. Cyclones have been more intense in the recent decade than they were in the previous five decades, according to the rise in low- and mid-level specific humidity and temperature over the BoB.

Deciphering the seasonal dynamics of microplastic morphotypes and associated co-contaminants along the northwest coast of India

In the present study, the northwest coast of India, bordering the Arabian Sea, was selected to evaluate the microplastic (MP) abundance. This is the first study to emphasize the effects of different seasons on MP distribution. The collected MPs were dried, segregated, and evaluated based on their morphotype, size, color, and polymer type. A total of 1756.6, 7326.6, and 202 particles/kg of sand were estimated in the pre-monsoon, monsoon and post-monsoon seasons, respectively, with a dominance of polypropylene (PP) type of plastic in the pre-monsoon and high-density polyethylene (HDPE) in monsoon and post-monsoon seasons. HDPE and PP collected MPs during the monsoon season were further characterized for associated contaminants. Metal absorbance was detected using SEM-EDX mapping and ICP-MS. The presence of organic compounds (OCs) was analyzed using GC-MS. MPs exhibit distinct associations with metals, among which the HDPE pellet morphotype exhibits a higher range of metal adsorption. Total 61 different OCs were associated with MPs. The HDPE pellets contained the highest amounts of hydrophobic organic compounds. PP pellets were found to contain triglycerides, fatty aldehydes, and alkaloids, along with HOCs. Among morphotypes, pellet forms of MPs were found to adsorb more contaminants. These co-contaminants infiltrate the study area through sewage runoff and shoreline debris deposition, subsequently interacting with MPs. Furthermore, the MP diversity was studied by employing the MP diversity integrated index, which suggests that most of the MP diversity was observed in the pre-monsoon period. The pollution load index employed an MP risk assessment, which presented a low degree of MP contamination. In contrast, the polymer hazard index was calculated as 21650.3 in post-monsoon, placing the area under the extreme danger category. It is evident from the data that the types of MP is more important than their number. Thus, MP morphotypes have importance in the adsorption of co-contaminants.

Health risk assessment and characterization of PM2.5 bound bioaerosols at the municipal solid waste landfill site of Nagpur, India

Landfill being the reservoir of organic waste, serves as the most important source in the generation and emission of bioaerosols in the environment, and these bioaerosols have a significant impact on the environment and public health. In India, there are limited studies on the characterization of culturable bacteria and fungi in the bioaerosols originating from landfills. Therefore, the present study aimed to quantify and identify the bioaerosols and study their characteristics at a landfill site in Nagpur, India. The study describes the seasonal variation of PM2.5, PM2.5-associated bacteria and fungi in the landfill air, their molecular identification, antibiotic resistance, pathogenicity, dispersion and health risk assessment during winter and pre-monsoon seasons at the landfill site and surrounding residential sites in upwind and downwind directions. The study showed PM2.5 concentration was highest in the winter season (265.56 μg/m3) followed by the pre-monsoon season (173.1 μg/m3) at the landfill site. The culturable bioaerosol level was also significantly higher in winter (11056 CFU/m3) in comparison to pre-monsoon season (2244 CFU/m3) at the landfill site. Upon isolating and characterizing the microorganisms in the bioaerosols, some of the bacterial isolates, like Bacillus, Staphylococcus gallinarum, and Streptomyces speibonae were found to be resistant to chloramphenicol, netillin, nitrofurantoin, streptomycin etc. About 30% of the bacterial isolates were found to show β-hemolytic virulence activity. This indicated the presence of multi-drug resistant and potentially pathogenic bacteria in the bioaerosols over the landfill. The health risk assessment in adults indicated that the workers at the landfill site were at risk of bacterial aerosol in the winter season (hazard quotient i.e., HQ>1). The impact of bioaerosols on children needs to be investigated in the further studies and regular monitoring of bioaerosols is suggested to avoid any morbidity. To the best of our knowledge, this is the first study on the characterization of microorganisms from the bioaerosols over an open landfill site in India.

A comprehensive multivariate investigation of the water quality of Kallada River in Kerala, India

The Kallada River is a remarkable water resource in Kerala and reviving several villages through its glorifying journey. An investigation was directed to evaluate the spatial and temporal status of water quality in Kallada River, Kerala using multivariate statistical tools from February 2019 to January 2021. The status of fifteen environmental variables was detected by using standard methodology. The increased levels of conductivity, total dissolved solids, biochemical oxygen demand, hardness, alkalinity, calcium, and magnesium were detected during the post-monsoon (PoM) season and those parameters were tend to increase towards the downstream stations. Some other variables such as turbidity, dissolved oxygen, NO3−, SiO2, and PO43− were higher during the monsoon (MoN) season. Temperature, pH, and chemical oxygen demand were higher during the pre-monsoon (PrM) season. Furthermore, multivariate statistical tools like principal component analysis (PCA), agglomerative cluster analysis (AHC), and pearsons correlation were used to assess spatio-temporal changes in water quality to reveal pollution. Contrarily, the midstream stations such as K6, K10, and the entire downstream area (K11 to K15) of the Kallada River is under the threats of many anthropogenic activities such as sewage effluents, sand mining and agricultural runoff when compared to the entire upstream stations (K1 to K5), and three midstream stations (K7 to K9). The presence of various organic and inorganic pollutants begins from K6 and drastically rises at K11. Hence, efforts are required to prevent the contamination in the Kallada River.

New particle formation induced by anthropogenic–biogenic interactions on the southeastern Tibetan Plateau

Abstract. New particle formation (NPF) plays a crucial role in the atmospheric aerosol population and has significant implications on climate dynamics, particularly in climate-sensitive zones such as the Tibetan Plateau (TP). However, our understanding of NPF on the TP is still limited due to a lack of comprehensive measurements and verified model simulations. To fill this knowledge gap, we conducted an integrated study combining comprehensive field measurements and chemical transport modeling to investigate NPF events on the southeastern TP during the pre-monsoon season. NPF was observed to occur frequently on clear-sky days on the southeastern TP, contributing significantly to the cloud condensation nuclei (CCN) budget in this region. The observational evidence suggests that highly oxygenated organic molecules (HOMs) from monoterpene oxidation participate in the nucleation on the southeastern TP. After updating the monoterpene oxidation chemistry and nucleation schemes in the meteorology–chemistry model, the model well reproduces observed NPF and reveals an extensive occurrence of NPF across the southeastern TP. The dominant nucleation mechanism is the synergistic nucleation of sulfuric acid, ammonia, and HOMs, driven by the transport of anthropogenic precursors from South Asia and the presence of abundant biogenic gases. By investigating the vertical distribution of NPF, we find a significant influence of vertical transport on the southeastern TP. More specifically, strong nucleation near the surface leads to an intense formation of small particles, which are subsequently transported upward. These particles experience enhanced growth to larger sizes in the upper planetary boundary layer (PBL) due to favorable conditions such as lower temperatures and a reduced condensation sink. As the PBL evolves, the particles in larger sizes are brought back to the ground, resulting in a pronounced increase in near-surface particle concentrations. This study highlights the important roles of anthropogenic–biogenic interactions and meteorological dynamics in NPF on the southeastern TP.

Groundwater quality characterization using an integrated water quality index and multivariate statistical techniques.

This study attempts to characterize and interpret the groundwater quality (GWQ) using a GIS environment and multivariate statistical approach (MSA) for the Jakham River Basin (JRB) in Southern Rajasthan. In this paper, analysis of various statistical indicators such as the Water Quality Index (WQI) and multivariate statistical methods, i.e., principal component analysis and correspondence analysis (PCA and CA), were implemented on the pre and post-monsoon water quality datasets. All these methods help identify the most critical factor in controlling GWQ for potable water. In pre-monsoon (PRM) and post-monsoon (POM) seasons, the computed value of WQI has ranged between 28.28 to 116.74 and from 29.49 to 111.98, respectively. As per the GIS-based WQI findings, 63.42 percent of the groundwater samples during the PRM season and 42.02 percent during the POM were classed as 'good' and could be consumed for drinking. The Principal component analysis (PCA) is a suitable tool for simplification of the evaluation process in water quality analysis. The PCA correlation matrix defines the relation among the water quality parameters, which helps to detect the natural or anthropogenic influence on sub-surface water. The finding of PCA's factor analysis shows the impact of geological and human intervention, as increased levels of EC, TDS, Na+, Cl-, HCO3-, F-, and SO42- on potable water. In this study, hierarchical cluster analysis (HCA) was used to categories the WQ parameters for PRM and POR seasons using the Ward technique. The research outcomes of this study can be used as baseline data for GWQ development activities and protect human health from water-borne diseases in the southern region of Rajasthan.

Estimation of Natural Uranium and Its Risk-Assessment in Groundwater of Bangalore Urban District of Karnataka, India

In this study, 56 groundwater samples were taken from diverse sources in Bangalore Urban district during the pre-monsoon and post-monsoon seasons to measure the uranium concentration and its correlation with different waterquality parameters. The uranium concentration varied from 0.94–98.79 µg/L during the pre-monsoon season and from 1.38–96.52 µg/L during the postmonsoon season. Except for a few readings, all were within the safe limit of 60 µg/L as prescribed by India’s Atomic Energy Regulatory Board (AERB), Department of Atomic Energy (DAE). Owing to its slightly higher concentration, a study on the radiological and chemical risks that are caused due to the ingestion of uranium was assessed. Based on the radiological aspect, cancer mortality and its risks were assessed, wherein all of the samples were well within the acceptable limit of 10−4; therefore, consuming these water samples was radiologically safe. However, when the risk that was caused by chemical toxicity was assessed, a few samples exceeded the hazard quotient (HQ) value of more than 1, thus illustrating that individuals were vulnerable to chemical risk. This paper features assessments of uranium and its risks to public health in groundwater samples if it exceeded the safe limit. Additionally, it recognizes the value of periodically assessing and treating the area’s drinking water sources.

Sea-level rise and mental health among coastal communities: A quantitative survey and conditional process analysis

This is the first large-scale empirical study examining the impact of sea-level rise induced by climate change on mental health outcomes among coastal communities. The study focuses on Bangladesh, a country severely affected by salinity ingress, flood risks, and agricultural damage due to sea-level changes. Participants (n = 1,200) randomly selected from three coastal regions each having high, moderate, or low vulnerability to sea-level rise were surveyed during the pre-monsoon season in 2021. The cross-sectional survey included validated measures of psychological distress, depression, anxiety, stress, environmental stressors, resource loss, and demographics. The results indicated significantly higher levels of psychological distress, depression, anxiety, and stress in residents of high-vulnerability areas compared to moderate or low-vulnerability regions. Resource loss served as a mediating variable between environmental stressors and mental health outcomes. Furthermore, demographic analyses showed that older adults and women reported higher levels of psychological distress. These findings align with the Sendai Framework for Disaster Risk Reduction, highlighting urgent need for targeted mental health interventions and sustainable models of care in coastal areas increasingly threatened by sea-level rise.

Neighbouring effect of land use changes and fire emissions on atmospheric CO2 and CH4 over suburban region of India (Shadnagar)

The present study investigated the effects of land use/land cover (LU/LC) changes on atmospheric carbon dioxide (CO2) and methane (CH4) concentrations over the sub-urban region of India (Shadnagar) using continuous decadal CO2 and CH4in-situ data measured by the greenhouse gas analyser (GGA). Data was collected from 2013 to 2022 at a 1 Hz frequency. Analysis of the current study indicates that during pre-monsoon, the seasonal maximum of CO2 was 409.91 ± 9.26 ppm (μ ± 1σ), while the minimum during monsoon was about 401.64 ± 7.13 ppm. Post-monsoon has a high seasonal mean CH4 concentration of 2.08 ± 0.06 ppm, while monsoon has a low seasonal mean CH4 concentration of 1.88 ± 0.03 ppm. The primary classes, such as forest, crop, and built-up, were considered to estimate the effect of LU/LC changes on atmospheric CO2 and CH4 concentrations. Between 2005 and 2021, the study's results show that the built-up area at radii of 10 km, 20 km, and 50 km increased by 0.17 %, 0.10 %, and 0.4 %, respectively. While other LU/LC categories declined by 30 %, agriculture areas increased by 30 % on average. As a result, the CO2 and CH4 concentrations at the study site are increased by 6 % (26 ppm) and 6.5 % (140 ppb), respectively. The present study utilised the fire-based carbon emissions data from the Global Fire Emissions Database (GFED) to understand the impact on atmospheric CO2 and CH4. Analysis of the present work investigated the influence of transported airmass on CO2 and CH4 during the pre-monsoon and post-monsoon seasons using the HYSPLIT trajectories and found emissions were from the northwest, southeast, and northeast of the study site. Further, in-situ CO2 and CH4 records are compared against the MIROC4-ACTM simulation, and strong agreement was found with bias of 1.80 ppm and 0.98 ppb for CO2 and CH4, respectively.

New evidence for CH4 enhancement in the upper troposphere associated with the Asian summer monsoon

The Asian summer monsoon (ASM) region is a key region transporting air to the upper troposphere (UT), significantly influencing the distribution and concentration of trace gases, including methane (CH4), an important greenhouse gas. We investigate the seasonal enhancement of CH4 in the UT over the ASM region, utilizing retrievals from the Atmospheric Infrared Sounder (AIRS), model simulations and in-situ measurements. Both the AIRS data and model simulation reveal a substantial enhancement in CH4 concentrations within the active monsoon region of up to 3%, referring to the zonal means, and of up to 6% relative to the pre-monsoon season. Notably, the spatial distribution of the CH4 plume demonstrates a southwestward shift in the AIRS retrievals, in contrast to the model simulations, which predict a broader enhancement, including a significant increase to the east. A cross-comparison with in-situ measurements, including AirCore measurements over the Tibetan Plateau and airline sampling across the ASM anticyclone (ASMA), favors the enhancement represented by model simulation. Remarkable CH4 enhancement over the west Pacific is also evidenced by in-situ data and simulation as a dynamical extension of the ASMA. Our findings underscore the necessity for cautious interpretation of satellite-derived CH4 distributions, and highlight the critical role of in-situ data in anchoring the assimilation of CH4.

Spatio-temporal evaluation of the impact of anthropogenic stressors on physico-chemical characteristics and water quality of the River Ganga using GIS-based approach in the middle Gangetic Plains at Patna, Bihar, India.

The present study aimed to assess the impact of anthropogenic stressors on the physico-chemical characteristics and water quality of the River Ganga employing a GIS-based approach in the middle Gangetic Plain at Patna, India. After the survey, sand mining, bridge construction, and disposal of untreated domestic and sewage wastes were selected as major anthropogenic stressors. A total of 48 samples were collected in pre-monsoon and post-monsoon seasons of 2022 and were analyzed for 16 physico-chemical parameters, namely water temperature (WT), pH, electrical conductivity (EC), total dissolved solids (TDS), turbidity, dissolved oxygen (DO), biological oxygen demand (BOD), total hardness (TH), Ca2+, Mg2+, Na+, K+, Cl- and SO42- ions, following standard protocols. The WQI was calculated using the Weighted Arithmetic Water Quality Index (WAQWI) method and spatial maps were created using ArcGIS software. The result revealed significant seasonal variation in several physico- chemical parameters except for Ca2+, K+ and TA (p > 0.05). ANOVA revealed significant variation for BOD and COD at Ghagha and Triveni, whereas for nitrate at Gai Ghat reference and impact sites, respectively. The Water Quality Index (WQI) revealed a deterioration in water quality by 60% in post-monsoon season. HCA revealed that the WQI was mostly governed by TDS, TH, TA, and EC.

Index Based Irrigation Suitability of Ramsar Sites (Rara and Ghodaghodi) in Western Nepal

The present study highlights the water quality of two important Ramsar sites of western Nepal (Ghodaghodi and Rara lakes) in terms of irrigation use. Based on land use patterns and location accessibility, 13 sites in Ghodaghodi and 18 in Rara were considered and the samplings were performed in the pre-monsoon and post-monsoon seasons. Different physicochemical parameters such as pH, electrical conductivity (EC), total dissolved solids (TDS), total hardness (TH), major cations, and anion (Na+, K+, Ca2+, Mg2+, and HCO3-) were measured. The calculated indices were permeability index percentage (PI), sodium percentage (%Na), sodium adsorption ratio (SAR), magnesium hazard ratio (MAR), residual sodium carbonate (RSC), and Kelly’s index (KI). Major ions were analyzed using ion chromatography including field and procedural blanks to maintain quality standards, whereas on-site parameters were measured by using standard multi-meter probes. The studied irrigation water quality parameters (pH, EC, TDS, TH) and indices (PI, MAR, RSC, KI, SAR, and %Na) fall within the permissible limit in both lakes, indicating the suitability of such water for irrigation purposes. In addition, based on the SAR vs. EC plot, all the results from both lakes fall in the S1 category, signifying low sodium hazard. Concerning EC, most of the samples demonstrate the C1 category and few are in the C2 category (in Ghodaghodi) whereas the C1 category predominates for Rara. According to IWQI, all water samples in both lakes fall in the class I category, which supports the results of other indices indicating the suitability of water for irrigation purposes.

Evaluation of Coastal Sediments for Heavy Metal Contamination, Bhavnagar Coast, Gulf of Khambhat, Gujarat, India

ABSTRACT This research examined heavy metals distribution and potential environmental impact in seven locations along the Bhavnagar coast in Gujarat, India. The study used several analyses, including hierarchical cluster analysis (HCA), principal component analysis (PCA), and correlation analysis to investigate the harmful heavy metals present in the area. To evaluate the possible risk of Cd, Pb, Cr, Zn, Co, Cu, Ni, Mn, and Fe to the marine environment, pollution indices such as contamination factors (Cf), enrichment factor (Ef), geo-accumulation index (Igeo), ecological risk factor (Er), ecological risk index (RI) and sediment quality guidelines (SQGs) applied. Based on the results, the mean concentration of heavy metals was ranked in the following order (mg/kg): Fe (561.4) > Mn (58.9) > Cr (42) > Zn (12.5) > Pb (8.2) > Ni (7) > Cu (5.2) > Co (2.7) > Cd (.3). Compared to the pre-monsoon and post-monsoon seasons, the results showed a diluting impact on heavy metal concentrations during the monsoon season. The spatial distribution of the heavy metals indicated that the geogenic source and anthropogenic source were the primary contributors to pollution in the studied region. Principal component analysis suggests that Cd, Pb, Co and Cr may have come from shipbreaking activities, municipal discharge and industrial operations. Cf, Igeo, and Ef demonstrated no pollution to moderate pollution, with a maximum contribution of Cd, and the coastal sediment poses a minimal ecological risk for all heavy metals investigated. Shipbreaking, urban runoff, salt-marine, and agricultural runoff release toxic metals into the coastal environment. In conclusion, the information obtained from this geochemical characterization could be valuable to policymakers and stakeholders in developing effective management measures for the Bhavnagar coastal region, Gulf of Khambhat, Gujarat, India.

Radiative effect of atmospheric Brown clouds over the Indo-Gangetic plain

Atmospheric brown clouds (ABCs) are widespread hazy accumulation of particles and gases dominant with absorbing nature impacting the air quality, hydrology and climate. The Indo-Gangetic plain (IGP) being an ABCs hotspots is prone to extreme pollution episodes due to anthropogenic activities. However, there is a scarcity of studies that specifically compare episodes of absorbing aerosols (ABCs) and comparatively non-absorbing aerosols (non-ABCs) along with their respective radiative impacts over the IGP. Here, we have used ground-based remote-sensors’ retrieved datasets from AErosol RObotic NETwork (AERONET) to study spatio-temporal variation of ABCs’ frequency and associated radiative properties across the IGP region during 2001–2019. The shortwave aerosol radiative effect (ARE) during ABC and non-ABC episodes is estimated using Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model. Our results show significant spatial variability in the frequency of ABC episodes across the IGP stations with ∼17 ± 5%, ∼19 ± 11% and ∼18 ± 13% average occurrence during winter, pre-monsoon and post-monsoon seasons, respectively. ARE estimations show enhanced surface dimming (ARESRF) and atmospheric warming (AREATM) during ABC episodes as compared to non-ABC episodes. A general increasing trend for ARE is observed as we move from west to east across the IGP due to the meteorological and geographical variations in the region. Our results show day-time averaged ARESRF varying between −142.46 ± 25.13 and −56.66 ± 6.88 W/m2 while AREATM ranging from 58.07 ± 2.58 to 132.69 ± 7.43 W/m2 for ABC episodes. Though ABC episodes show lower aerosol loading as compared to non-ABC episodes in our study, we found higher atmospheric heating during ABC episodes mainly due to distinct chemical composition (lower single scattering albedo) of absorbing aerosols. The upper bound of the difference between atmospheric heating rate during ABC and non-ABC episodes is found to be 0.48 ± 0.27 K/day.

Exploring thermal comfort in rural houses of Chhattisgarh state, India: A comprehensive survey and adaptive model analysis

Thermal comfort studies in India are very much at an emerging stage. According to Indian codes, in the summer, the comfortable temperature range for residential buildings is 23–26 °C. The recommended Indian residential comfort range does not consider the impact of India’s enormous cultural and geographical heterogeneity. Additionally, there seems to be very little effort to conduct a thermal comfort field survey in India’s rural regions. In recent years, houses in rural India have been converted from kutcha (mud houses) to pucca (concrete houses). This work is aimed at proposing an adaptive thermal comfort model for the premonsoon season in the rural area of Raipur, Chhattisgarh, India. The model was achieved using a field study survey conducted in 80 rural area houses in the months of June and July. Regression analysis, the Griffiths method, and the Fanger method have been adopted to analyze thermal comfort. Based on the regression analysis, the comfort band (voting −1 to +1) is established in the range of 28.39 °C to 32.31 °C, with 30.30 °C as the neutral temperature. The study has been carried out to assess the influence of gender, age, controls, and fan usage on thermal comfort perception in rural households.

Hydrogeochemical characterization and non-carcinogenic health risk assessment of fluoride and nitrate-affected groundwater in northern parts of Tumkur district, Karnataka, India

Groundwater contamination from geogenic and anthropogenic sources is a significant concern for the public health across the globe. In India, fluoride and nitrate contamination are the most prevalent contaminants in the groundwater. This study evaluated groundwater quality in four over-exploited sub-districts of Tumkur district in Karnataka by collecting 143 samples from post and pre-monsoon seasons and using different hydrogeochemical, statistical and bivariate graphical approaches. Comparison with Drinking Water Standard guidelines revealed elevated levels of fluoride, nitrate, and total dissolved solids (TDS), rendering the groundwater unsuitable for drinking. According to Chadha’s diagram, the predominant groundwater type is Na-Cl, and Gibbs diagram suggested the influence of rock dissolution and weathering. Bivariate plots indicated that hydrogeochemical characteristics were primarily influenced by silicate weathering of minerals, cation ion exchange processes, and anthropogenic factors. A non-carcinogenic health risk assessment was conducted using two different hazard index (HI) approaches from United States Environmental Protection Agency (USEPA) and Agency for Toxic Substances and Disease Registry (ATSDR). It was found that health risk associated with fluoride is more significant than the health risk from nitrate, with children being the most affected, followed by adolescents and adults. A holistic approach to assess cumulative health risks from fluoride and nitrate contamination in groundwater, as demonstrated in this study, promotes the synergistic advancement of SDG 3: Good health and well-being and SDG 6: Clean water and sanitation.