This study investigates the seasonal dynamics and fluxes of dissolved organic carbon (DOC), dissolved silica (DSi) and dissolved nitrate in the Sharavati River catchment, Western Ghats, and their transfer to the estuary. DOC exhibited moderate seasonal and spatial variability, with maximum concentrations in pre- and post-monsoon (up to 5.66 mg/L) linked to leaching of forest litter and soil organic matter mobilization, while monsoon values were lowest due to dilution. DSi showed spatial control over its concentrations across different seasons. DSi concentrations were highest upstream (27 mg/L in pre-monsoon 2019) due to intense silicate weathering, but declined downstream under the influence of damming, biological uptake, and dilution. Nitrate concentrations exhibited strong seasonal as well as spatial control. Nitrate peaked during the enhanced monsoon by cyclonic events (up to 1.56 mg/L), reflecting runoff and agricultural inputs, whereas pre-monsoon levels were minimal due to reduced discharge and enhanced denitrification. The estimated annual fluxes to the estuary were 1,966 t yr⁻¹ for nitrate, 6,610 t yr⁻¹ for DOC, and 36,000 t yr⁻¹ for DSi. Relative to other west-flowing rivers of India, the Sharavati displayed lower nitrate and DOC fluxes (65 and 104 kg km⁻² yr⁻¹, respectively), consistent with its largely forested catchment, while its DSi flux (753 kg km⁻² yr⁻¹) was moderate, shaped by lithology and reservoir regulation. These findings underscore the role of monsoonal effects enhanced by cyclones and damming in controlling nutrient and carbon export. This study contributes to biogeochemical datasets assessing Arabian Sea ecosystem responses.

Microplastics, significant and emerging pollutants, are increasingly contaminating air, soil and water, posing a threat to the entire planet. The purpose of this study was to examine the distribution, composition, and abundance of microplastics in the freshwater body of the Hiren-2 reservoir in the state of Gujarat, India. The microplastic abundance per liter of water varied from 1.756 to 5.422. Among the water samples, those with microplastic sizes of 0.05–0.5 mm were the most dominant, followed by those with sizes of 0.05–1 mm, 1–2 mm, 2–3 mm and 3–5 mm. In terms of shape, fibers were the most dominant, followed by fragments, pellets, foams and films. The color distribution of the microplastics revealed black as the most prevalent color, followed by blue, red, green, white, yellow, orange, purple and gray. The average abundance of microplastics per kilogram of sediment ranged from 8.556 to 13.778. Among the sediment samples, those with microplastic sizes of 0.05–0.5 mm were the most dominant, followed by those with sizes of 0.5–1 mm, 1–2 mm, 2–3 mm and 3–5 mm. Fibers were the most prevalent fibers in the sediment, followed by fragments, pellets, foams and films. In the sediment, black emerged as the predominant color, followed by red, blue, green, yellow, orange, white, gray and purple. Polyethylene and polypropylene were identified as the predominant polymers in both the sediment and water samples. These findings underscore the significant presence of microplastics in the sediment and water of the reservoir, highlighting the urgency of addressing microplastic pollution in this freshwater ecosystem.

Formation of ferromanganese nodules (FMNs) is an important pedogenic process which is commonly observed in the Ganga alluvium. We have studied geochemistry of the host alluvium and FMNs from the eastern Uttar Pradesh, India. The FMNs were categorized in three sizes (>5.6mm, 5.6 to 2mm, and 2 to 0.5mm). The major and trace elements present in the sediments and FMNs of three size ranges were analysed using XRF and ICP-OES. The geochemical composition of the sediments and FMNs were compared with the geochemical values of the Upper Continental Crust (UCC). The enrichment factor (EF) of the analysed elements were calculated for both the host sediments and the FMNs. Additionally, the Chemical index of weathering (CIA) was calculated to quantify the extent of chemical weathering of the sediments and FMNs in the alluvium. The sediments and FMNs both showed moderate chemical weathering. We propose that the weathering of aluminosilicate stages may have given Fe, Mn, and related trace elements for the nodule formation. Prolonged dry spells and monsoonal wet seasons in the Ganga plain region may be key contributors to the weathering, mobilization, precipitation, and redistribution of the Fe and Mn phases in nodules. Certain elements, such as Pb and Cr, which are considered to be harmful to the environment got sequestered in FMNs. This helped immobilization of these contaminants. Whereas, elements like P, Co, Zn, and Cu were also got sequestered during the formation of FMNs. Therefore, it has also impacted soil nutrient availability.

Study region: Sharavati River, Karnataka, India. Study focus: A small mountainous river system, Sharavati, was selected to study the impact of river damming on the hydrological cycle. Sharavati river flow is regulated by two dams, Linganamakki and Gersoppa. Despite the Western Ghats' global significance in controlling local and regional climates, the effects of damming on its hydrological cycles have received limited attention. A stable water isotopic approach was employed in the study. New hydrological insights for the region: The line-conditioned excess (lc-excess) was primarily negative across all seasons. Notably, the pre-monsoon season exhibited comparatively higher evaporation with high negative lc-excess, while the postmonsoon lc-excess values approached zero, indicating minimal evaporation. The sampling points from the dams exhibited very high evaporation signals, the evaporative loss during the pre-monsoon season from the Linganamakki reservoir was estimated as 10 %, and from the Gersoppa dam was 6 %. Consequently, groundwater sampled near the dams, plotted along the local evaporation line indicating recharge from the evaporated reservoir water. Damming has affected the hydrological cycle of the heavily regulated Sharavati River, transforming the entire catchment into a connected, narrow lake-like structure, especially during the pre-monsoon season. Since the Western Ghat river systems are regulated by many large and small dams, it is pertinent to study the impact of damming on the hydrological cycles of the entire system.

A study was conducted for the first time to understand the geochemical processes controlling the chemistry of the Kali River in tropical southwestern India and to determine its chemical denudation and net carbon dioxide consumption. The samples were collected from the source to the mouth of the river (15 stations) during monsoon (July 2018), post-monsoon (December 2018), and pre-monsoon (May 2019) seasons. The catchment experiences intense chemical weathering on account of heavy rainfall accompanied by runoff during the summer monsoon. Seasonal variations in silicate weathering processes are significantly controlled by runoff, and their rates are proportional to the discharge. The annual chemical denudation rate (CDR) calculated exclusively from the upstream catchment that are dominated by silicate rocks estimated to be 48.2 tons/km(2)/yr with a silicate weathering rate (SWR) of 41.3 tons/km(2)/yr and carbonate weathering rate (CWR) of 6.9 tons/km(2)/yr. The CDR is two times higher than the global mean average rate. The mean CO2 consumption rate (CCR) for silicate weathering is 2.9 x 10(5) mol. km(-2) y(-1), which is three-fold higher than the global average. Silicate rock weathering intensity (Re) values indicate the formation of the gibbsite. The Re does not show variations from upstream to downstream, implying the rapid transport of weathered material from the river catchment area. Intense rain, runoff, and temperature are the dominant climatic factors that accelerate weathering in the study area. This underscores the significance of small mountainous coastal rivers as drivers of intense chemical weathering in humid tropical environments, which removes the atmospheric CO2. This study adds to the existing database on chemical weathering and associated fluxes in granitic catchments across the globe.

The present study aims to assess the extent of trace metal pollution in the sediments of Sita-Swarna estuary, west coast of India, and investigate their possible ecological risk on the aquatic environment. The sediment cores were analyzed for sand, silt, clay, organic carbon, and trace metals (Al, Fe, Mn, As, Cd, Co, Zn, Pb, Ni, Cr, and Cu) at 2-cm intervals. The study revealed that sediments have deposited in relatively violent to very violent hydrodynamic energy conditions. Factor analysis indicated that the metal distribution is mainly controlled by Fe-Mn oxyhydroxides and organic carbon. Further, the geochemical approach, pollution indices, and statistical evaluation revealed moderate pollution in the catchment. From an ecotoxicological perspective, the estimated risk index (RI) value was found to less than 150, indicating low risk for aquatic life. Thus, this baseline study would help to adopt strategies in pollution control and protect the fragile marine environment.

The Payaswini-Chandragiri river system comprises two small tropical rivers originating in the Western Ghats (Patti Ghats reserve forest) of Peninsular India and contributes to an annual discharge of 4.40 km3 of water into the Arabian sea. This work mainly focuses on the fluxes of total dissolved organic carbon (DOC) from these rivers into the Arabian Sea. Quantifying the amount of terrestrial carbon fluxes into the ocean is important in better understanding long-term climate change because a significant portion of atmospheric carbon dioxide is getting locked up in the ocean sediments. However, DOC fluxes from the tropical southwest flowing rivers of India are sparse, especially in the backdrop of increased human activities since the onset of the Anthropocene. This study is an attempt to fill this gap. The DOC fluxes were measured between April 2016 and Dec 2017 on a seasonal basis. The flux of DOC in the post-monsoon season was 1.3 and 1.2 times higher than the monsoon and the pre-monsoon seasons, respectively. This riverine system contributes ∼0.4% of the total DOC flux received by the Arabian sea.

Tropical, small mountainous rivers draining granite/granitic gneiss exhibit intense weathering rates and associated carbon dioxide sequestration, which has implications on the global CO2 budget. However, there is paucity of data from these catchments. This study aimed to understand silicate weathering rates (SWR) and CO2 sequestration rates (CCR) in a small tropical mountainous river, Sharavati in the southwestern India. Bicarbonates, Cl-, Na+, Ca2+ and silica, are predominant in the river, indicating their source from catchment rocks and atmosphere. Groundwater shows a similar abundance of major ions, indicating identical sources. Intense chemical weathering due to hot and humid climate, heavy monsoonal rains and associated river discharge are the main controlling factors of major ion chemistry in the Sharavati river. The presence of clay mineral kaolinite in the catchment corroborates with the above controlling factors. The calculated silicate weathering rate (SWR) is 27 t km(-2). y(-1) and associated carbon dioxide consumption rate (CCR) is 3.9 x 10(5) mol km(-2). y(-1). When compared to other small tropical river basins having similar climate and lithology, CCR of Sharavati is comparable to Jiuhua Mountain rivers, (South China) and twice that of Sorocaba River (Brazil). CCR is 3.9 times higher than the global average on account of the peculiarity of the terrain. It can be concluded from a comparative study of small tropical rivers, that rainfall and runoff are the main parameters controlling the weathering rates irrespective of catchment lithology.

Trace metals act as a limiting nutrient and prerequisite for primary productivity in marine environments. The distribution of metals in dissolved phase along the salinity gradients of Swarna, Sharavati and Kali estuaries in southwestern India, during post and pre-monsoon seasons, were studied. We have investigated the behaviour of trace metals in the estuarine environment and their extent of impact on human health and ecosystem. The study revealed, non-conservative behaviour of dissolved Mn, Fe, Ni, Cd and Co in the estuaries. Whereas Cu behaved non-conservatively in post-monsoon and conservatively in pre-monsoon seasons. Risk assessment studies revealed that higher chronic daily intake (CDI) in humans, through dermal pathway, in Swarna and Sharavati estuaries during post-monsoon, whereas it was during pre-monsoon season in the Kali estuary. Hazard Index values for the studied metals in adults and children are below risk thresholds, though children are more prone to health risk through the dermal pathway.

There is very little knowledge on microplastic pollution in the Western Ghats (WG), a heritage site in southwest India. To address this, we have studied the spatiotemporal variations of sedimentary microplastics (MPs) from the River Sharavathi, a pristine river in the Western Ghats (WG), southern India. The rich biodiversity in the region makes it relevant to analyse the distribution of this emerging pollutant that is causing harm to the biota and the ecosystem. We analysed the sedimentological and carbon content (organic and inorganic) of these sediments and explored their relationship with MPs. Finally, risk assessment indices such as the Pollution Load Index (PLI), the Polymer Hazard Index (PHI), and the Potential Ecological Risk Index (PERI) were calculated to detect the levels of plastic pollution. The concentration of MPs ranged from 2.5 to 57.5 pieces/kg and 0 to 15 pieces/kg during the pre-monsoon and post-monsoon seasons, respectively. The dip in the MPs’ abundance during the post-monsoon season was due to the extremely high rainfall in the river basin during July–August 2019, which would have entrained the sedimentary MPs and transported them to the coast/Arabian Sea. Smaller MPs (0.3–1 mm) were more abundant than the larger MPs (1–5 mm), mainly due to the breakdown of sedimentary plastics by physical processes. Fragments, films, foams, and fibres were the main categories of MPs, and the main polymers were polyethylene, polyethylene terephthalate, and polypropylene. No significant relationship was observed between the sedimentological properties and microplastics, which may be due to the different physical properties of sediments and microplastics. The PLI, PHI, and PERI indices suggest different contamination levels in the river basin. Based on the PLI scores, all the samples belong to the hazardous level I suggesting minor risk category, and the risk of microplastic pollution falls under the high to hazardous risk category based on the PHI values. The PERI value ranged from 160 to 440 and 40 to 2240 during the pre-monsoon and post-monsoon seasons, respectively. The risk assessment in a region known for its rich biodiversity is crucial, as the data can be used by the district administration to mitigate plastic pollution.

Spatio-temporal behaviour of dissolved organic carbon (DOC), inorganic carbon (DIC) and silica (DSi) along the salinity gradient of three south-west Indian monsoonal estuaries are presented. This study showed both conservative and non-conservative behaviour of DOC along the salinity gradient under varying physico-chemical conditions. The gross flux of DOC arriving at the estuary from the rivers was estimated as 0.9 x 109 g/yr for Sita-Swarna river, 4.2 x 109 g/yr for Sharavati river and 5.6 x 109 g/yr for Kali river. Similarly, the net fluxes of DOC estimated beyond the estuarine zone was 5.5 x 109 g/yr (Sita-Swarna), 8.0 x 109 g/yr (Sharavati) and 7.7 x 109 g/yr (Kali). This indicates that these estuaries are the sources of organic carbon to the ocean. The DIC linearly increased towards the higher salinity with net fluxes of 38 x 109 g/yr (Sita-Swarna), 75 x 109 g/yr (Sharavati) and 97 x 109 g/yr (Kali). The combined DIC flux of Sita-Swarna, Sharavati and Kali rivers is -8% of the total DIC fluxes received from the west flowing rivers of India, to the Arabian Sea. The DSi showed a biogenic removal of 80?85% in all the studied estuaries. From this study it is concluded that the west flowing river estuaries are net sources of DOC and DIC and net sink for DSi. Consideration of the role of west flowing rivers of peninsular India is important for the better understanding of the carbon dynamics in the river-estuary-ocean boundary.

BACKGROUND:The current recommendation in India to commence first dose of measles immunization is at 9 months of age. The effectiveness of measles vaccination is greatly impacted by the level of maternal measles antibody (MMA) during infancy. OBJECTIVES:To find the prevalence of MMA and to study the maternal and infant factors associated with persistence of MMA among the infants in a Indian rural community. METHODOLOGY:Dried blood spot sample was collected before vaccination among infants aged 9 months and above when they came for first dose of measles vaccine to assess measles-specific maternal IgG antibody titers by enzyme immunoassay. Maternal and child factors influencing persistence of MMA were collected by interviewing the mothers. Association between various factors affecting seropositivity was tested using univariate logistic regression analysis and strength of association is reported as risk ratio with 95% confidence interval. RESULTS:Based on the qualitative estimation among all the recruited children (250) in the study, 4 (1.6%) infants showed the presence of MMA whereas 25 (10%) of children had MMA on quantitative estimation. The effect of maternal factors, child nutrition, and sociodemographic factors on the presence of MMA was not found to be statistically significant. CONCLUSION:The prevalence of persistent MMA (IgG titer ≥200 mIU/ml) among the infants aged 9-12 months was 10%. The choice of vaccinating infants at the end of 9 months for the first dose of measles vaccine is justified as the remaining (90%) of infants were susceptible for measles infection at this age.

The present investigation was carried out on the Teesta river at three stations to study the seasonal change of phyStation-1co-chemical factors . The parameters studied were air and water temperature, turbidity, pH, total dissolved solid, total suspended solid, total solid, conductivity, dissolved oxygen, biological oxygen demand, free carbon dioxide, chloride, salinity, total alkalinity, hardness, nitrate, phosphate and Station-1licate. The seasonal variation of the different parameters i.e Pre monsoon, Monsoon, and Post Monsoon has been discussed.