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Tripura has a good grasp of edible cultivated bananas which are yet to be treated on scientific grounds. Amongst them, one is locally named as ‘Gopi Kola’ which has been domesticated by the farmers due to its good vigor and yield. However, the technical identity of the Musa variety Gopi is indistinct. The present investigation addresses the identification and documentation of Musa variety Gopi in the perspectives of morphology and cytology. Systematic morphological screening and cytological analysis produced relevant results in decoding its taxonomical position. The taxonomical scorecard method reveals a score of 61 according to which the genome based grouping is ABB for the variety. Analysis of morphological traits showing concurrence with both the ancestral species also signifies its hybrid nature. Chief distinguishing features of the cultivated variety Gopi include shiny pseudostem with light blotches, light waxy nature of male bud, thick finger peel and sweet fleshy pulp with occasional presence of few soft seeds mostly at the upper portion of the finger. Cytological results implying 2n = 3x = 33 chromosome count also adds to the triploidy of the cultivar. Karyotype is symmetrical belonging to Stebbins 2A category and is characterized by prevalence of median and submedian chromosomes with three secondary constricted chromosomes. On account of revelations in the present study, the identity of Musa cultivar Gopi is designated as Musa × paradisiaca L. ‘Gopi’.

Arsenic (As) contamination of groundwater in parts of South and Southeast Asia is a public health disaster. Millions of people living in these regions could be chronically exposed to drinking water with As concentrations above the World Health Organization’s provisional guideline of 10 µg/L. Recent field investigations have shown that the distribution of groundwater As in many shallow aquifers in India and Bangladesh is evolving rapidly due to massive irrigation pumping. This study compares a decade-old dataset of As concentration measurements in groundwater with a dataset of recent measurements using geospatial machine learning techniques. We observed that the probability of As concentrations >10 µg/L was much greater in the regions between two major rivers than in the regions close to the Ganges River on the eastern border of the study area, where As concentrations >10 µg/L had been measured prior to 2005. The greater likelihood that As is present away from the river channel and is found instead in the interfluvial regions could be attributed to the transport and flushing of aquifer As due to intense groundwater pumping for agriculture. We estimated that about 2.8 million people could be chronically exposed to As concentrations >10 μg/L. This high population-level exposure to elevated As concentrations could be reduced through targeted well-testing campaigns, promoting well-switching, provisions for safe water access, and developing plans for raising public awareness. Policymakers could use the ternary hazard map to target high-risk localities for priority house connections of piped water supply schemes to help reduce human suffering.Key pointsA high-resolution predictive analysis was conducted using geospatial machine learning techniques to identify human suffering.A comparison of decadal arsenic measurements and a machine learning prediction suggests a shift in hotspot location.Groundwater in a region between two major rivers was found to be unsafe for agricultural and drinking purposes.Plain language summaryWe conducted a high-resolution predictive analysis using geospatial machine learning algorithms to identify the extent and hotspot location of arsenic (As) contamination in the Murshidabad district of West Bengal, India. The predictive analysis identified an area between two adjacent major rivers in which the probability of As concentrations >10 μg/L in groundwater is significantly greater than in other areas. There is a shift in As hotspot location from the regions near the river toward the regions between the two adjacent rivers, possibly due to intense groundwater pumping for agriculture. We estimated that about 1.6 million people could be at high-risk from drinking water contaminated by As concentrations >10 μg/L. Policymakers could use the hazard map and the analysis of treated piped drinking water networks to provide access to targeted safe water wells for affected households.

Arsenic (As) is a well-known human carcinogen and a significant chemical contaminant in groundwater. The spatial heterogeneity in the distribution of As in groundwater makes it difficult to predict the location of safe areas for tube well installations for consumption and agricultural use. Geospatial machine learning techniques have been used to predict the location of safe and unsafe areas of groundwater As contaminations. Here we used a similar machine learning approach to determine the risk and extent of As >10 μg/L in groundwater at a finer spatial resolution (250m × 250m) in two worst-hit districts of Assam, India, to advise policymakers for targeted campaigning for mitigation. Random Forest Model was employed in Python environments to predict probabilities of the occurrences of As at concentrations >10 µg/L using several intrinsic and extrinsic predictor variables. The selection of predictor variables was based on their inherent relationship with the occurrence of As in groundwater. The relationships between predictor variables and proportions of As occurrences >10 μg/L follow the well-documented processes leading to As release in groundwater. We identified extensive areas of potential As hotspots based on the probability of ≥0.7 for As >10 µg/L. These identified areas include areas that were not previously surveyed and extended beyond previously known As hotspots. Twenty-five percent of the land area (1,500 km2) was identified as a high-risk zone with an estimated population of 155,000 potentially consuming As through drinking water or food cooked with water containing As >10 μg/L. The ternary hazard map (i.e., high, moderate, and low risk for As >10 µg/L) could inform the policymakers to target the regions by establishing newer drinking water treatment plants and supplying safe drinking water.

Attempt was made towards optimizing an in vitro shoot multiplication of banana cultivar Gopi with subsequent assessment of genetic stability. Experiments on enhanced shoot multiplication were conducted in MS fortified with BAP, Kn and 2-iP (4 mg/l) for a period of 8 weeks. Administration of exogenous root inducing growth regulator was eliminated to reduce culture investment and economy. Treatment with BAP supplemented medium proved to be optimum for shoot multiplication whereas 2-iP produced satisfactory results for shoot elongation. Long term incubation in all the treatments had been favorable for developing efficient root system. Hardening of in vitro grown plantlets showed high rate of survival (95%) upon transfer to potted soil. Assessment of clonal fidelity through inter simple sequence repeats (ISSR) analysis revealed 100% uniformity.

Urban areas have very complex spatial structures. These spatial structures are primarily composed of a complex network of built environments, which evolve rapidly as the cities expand to meet the growing population’s demand and economic development. Therefore, studying the impact of spatial structures on urban heat patterns is extremely important for sustainable urban planning and growth. We investigated the relationship between surface temperature obtained by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER, at 90 m spatial resolution) and different urban components based on high-resolution QuickBird satellite imagery classification. We further investigated the relationships between ASTER-derived surface temperature and building footprint and land use information acquired by the New York City (NYC) Department of City Planning. The ASTER image reveals fine-scale urban heat patterns in the NYC metropolitan region. The impervious-medium and dark surfaces, along with bright covers, generate higher surface temperatures. Even with highly reflective urban surfaces, the presence of impervious materials leads to an increased surface temperature. At the same time, trees and shadows cast by buildings effectively reduce urban heat; on the contrary, grassland does not reduce or amplify urban heat. The data aggregated to the census tract reveals high-temperature hotspots in Queens, Brooklyn, and the Bronx region of NYC. These clusters are associated with industrial and manufacturing areas and multi-family walk-up buildings as dominant land use. The census tracts with more trees and higher building height variability showed cooling effects, consistent with shadows cast by high-rise buildings and trees. The results of this study can be valuable for urban heat island modeling on the impact of shadow generated by building heights variability and trees on small-scale surface temperature patterns since recent image reveals similar hotspot locations. This study further helps identify the risk areas to protect public health.

Forests are critical in regulating the world’s climate and they maintain overall Earth’s energy balance. The variability in forest canopy structure, topography and underneath vegetation background condition creates uncertainty in the estimation and modelling of Earth’s surface radiation particularly for boreal regions in high latitude. We studied seasonal variation in surface reflectance with respect to land cover classes, canopy structures, and topography in a boreal region of Alaska by fusing together Landsat 8 surface reflectance and LiDAR-derived canopy matrices. Our study shows that canopy structure and topography interplay and influence surface reflectance in a complex way particularly during the snow season. Topographic aspect and elevation control vegetation growth, type and structure. The southern slope is featured with more deciduous and taller trees having greater rugosity than the northern slope. Higher elevation is associated with taller trees for both vegetation types, particularly in the southern slope. In general, surface reflectance shows similar relationships with canopy cover, height and rugosity, mainly due to close relationships between these parameters. Surface reflectance decreases with canopy cover, tree height, and rugosity especially for evergreen forest. Deciduous forest shows larger variability of surface reflectance, particularly in March, mainly due to the mixing effect of snow and vegetation. The relationship between vegetation structure and surface reflectance is greatly impacted by topography. The negative relationship between elevation and surface reflectance may be due to taller and denser vegetation distribution in higher elevation. Surface reflectance in the southern slope is slightly larger than the northern slope for both deciduous and evergreen forest. The shadow effect from topography and tree crowns on surface reflectance play a different role for deciduous and evergreen forests. For deciduous forest, topographic shadow effect on surface reflectance is stronger than from tree shadowing in all seasons. For evergreen forest, shadow effects from topography and tree crowns on surface reflectance are both equally dominant, however tree shadow effect is more significant in March than in May and August. The generalized additive models (GAM) based on non-linear relationships between response (surface reflectance) and predictor (canopy structures and topography) variables confirms such observations. Our study not only provides accurate quantification of surface radiation budget but also helps in parametrization of climate change models.

The COVID-19 pandemic has affected daily lives of people around the world. People have already started to live wearing masks, keeping a safe distance from others and maintaining a high level of hygiene. This paper deals with an in-depth analysis of riskness associated with COVID-19 infections in Kolkata Municipal Corporation (KMC) at the sub-city (ward) level. Attempts have been made to identify the areas with high or low risk of infections using GIS-based geostatistical approach. Cosine Similarity Index has been used to rank different wards of KMC according to the degree of riskness. Four indices were computed to address intervention objectives and to determine 'Optimized Prevention Rank' of wards for future policy decisions. The highest risk areas were located in the eastern and western part of the city, to a great extent overlapped with wards containing larger share of population living in slums and/or below poverty level. While, highly infected areas lie in central Kolkata and in several wards at the eastern and northeastern periphery of the KMC. The 'Optimized Prevention Rank' have indicated that the lack of social awareness along with lack of social distancing and high susceptibility have contributed to the increasing number of containments of COVID-19 cases. The rankings of the wards would no doubt provide the policy makers a basis to control further spread of the disease or delay a second wave. Since effective antiviral drugs are far away, the application of our approach would save the lives of many people, especially the poor and underprivileged.

The Covid-19 pandemic has inherently affected daily lives of people around the world. We, the people, have already started to live in a new-normal way, such as wearing masks, keeping a safe distance from others and maintaining higher level of health & hygiene standards. However, because of this pandemic, the global economy has taken a major blow. Many people have lost their livelihood, and now facing challenges in getting better healthcare facilities and food for survival. Given the serious challenges to the problem, this paper analyzes demographic data to predict vulnerable areas in Kolkata metropolitan city that houses nearly one-third of its population in slums and one-fifth below poverty level, under compromised living conditions. The analysis revealed that the highest risk areas are located in the east and west of the city, the area to a great extent overlapped with wards containing larger share of population below poverty level and are also living in slums. The analysis of publicly accessible Covid-19 case records and containment zones data indicate the hardest hit areas lies in the central Kolkata and several wards along the eastern and northeastern border of the Kolkata Municipal Corporation. The data further revealed that the virus infections have extended to the south Kolkata with increasing number of ‘broad-based’ containment zones with heightened cases. The analysis of demographic characteristics of the hardest hit wards revealed that not a single variables are directly associated with the increase in the number of containments for a particular ward. The ranking of wards based on four intervention criterion have suggested that the ‘lack of social awareness’ along with ‘lack of social distancing’ have dominantly contributed to the increasing number of containments of Covid-19 cases in Kolkata. Determination of optimized ranking and Spearman’s rank correlation coefficient of the wards based on four intervention criterion provided a basis for the policy makers to assess ward-based interventions criterion to control further spread of the disease and/or prevent second wave of infections. Given that the effective antiviral drugs is far away from common publics reach, the application of our study approach would benefit saving lives of many vulnerable populations.

Plants take up silicon (Si) from the soil which impacts their growth and nutrient accumulation. It increases plant resistance to abiotic and biotic stresses such as drought, salinity, and heavy metal, diseases, and pest infestation. However, until recently, research of Si application on the crop is limited. This article reviews the recent progress of research on Si application on crop growth and yield, nutrient availability in soil and accumulation, and drought tolerance of crop plants. The review’s findings show that Si improves crop development and output under stressful environmental conditions. Silicon increases the availability and accumulation of both macronutrients (nitrogen, potassium, calcium, and sulphur) and micronutrients (iron and manganese). It improves drought resistance by increasing plant water usage efficiency and reducing water loss during transportation. Silicon application is a crucial aspect of crop productivity because of all of these favorable attributes. The gaps in current understandings are identified. Based on the outcome of the present research, future scopes of research on this field are proposed.

Well testing in the floodplain of the Brahmaputra River in Golaghat and Jorhat districts of Assam, India, shows that groundwater arsenic (As) concentrations increase with distance from the river. To establish the origin of this pattern, an additional 900 wells

Lakes are recognized as critical zones for carbon transformation and storage, and lacustrine sediments sequestrate considerable amounts of organic carbon (OC). Understanding sedimentation processes and OC burial patterns is crucial to clarifying lakes’ role in global carbon cycling. However, OC sedimentation may be quite spatially heterogeneous within an aquatic system, owing to the differences in OC production and sources, hydrodynamic conditions and underwater topography. The uncertainties in estimating OC sequestration in the world’s large lakes remain poorly constrained. This study takes the test case of two large lakes (50 and 249 km2) with different water depth and trophic status, using a multi-core paleolimnological technique, to identify the spatial variation in OC accumulation and its main influencing factors over the past century. Results of multi-core comparisons revealed similar temporal trends in major organic and nutrient parameters, suggesting coherent processes of whole-lake sedimentary environment changes for each lake. The OC preserved in sediments was primarily of autochthonous origin. However, OC standing stocks varied ∼3-fold spatially, and average OC accumulation rates ranged between 9.5–27.4 g m−2 yr−1 (post–1963 in oligo-mesotrophic deep-lake Lugu) and between 17.4–43.5 g m−2 yr−1 (post–1980 in eutrophic shallow-lake Erhai), respectively. These variations were primarily attributable to the spatial differences in aquatic primary production and terrestrial detritus supply relating to anthropogenic land-use change and phosphorus loading, rather than intra-lake sediment focusing-related transport and redistribution. The single central-core approach from Lugu Lake would overestimate whole-lake OC stock by 32% or underestimate the value by 48%, indicating spatial variability is an important source of uncertainty for OC stock quantification in similar large and/or morphometrically complex waterbodies. Therefore, spatial heterogeneity of OC accumulation in inland waters requires considerable research with well-placed multi-cores to provide a deeper understanding of carbon sequestration patterns and mechanisms.

Atmospheric pollution, one of the leading environmental problems in South and East Asia, and its impact on the terrestrial environmental quality remain poorly understood particularly in alpine areas where both historical and present-day mining and smelting operations might leave an imprint. Here, we reconstructed atmospheric trace metals pollution during the past century using core sediments from a large and deep alpine lake in Southwest China. The implication of in lake and/or in watershed sediment focusing in pollution quantification is discussed by analyzing 15 sediment cores. Factor analysis and enrichment factor indicated Cd, Pb and Sb as the typical pollutants. Distinct peaks of Pb and Sb pollution were observed around the 1920s, but little Pb pollution was detected in recent decades, different from other studies in similar regions. Cadmium pollution was observed until the mid-1980s synchronized with Sb. The distinctive variations in atmospheric trace metal pollution process in Southwest China highlight the regional and sub-regional sources of metal pollutants, which should be primarily attributed to non-ferrous metal smelting emissions. Both natural and anthropogenic metals showed wide concentration ranges though exhibited similar temporal trends in the 15 cores. Spatial variations of anthropogenic metals were influenced by the in-watershed pollutants remobilization, whereas, natural metals were regulated by the detrital materials in the sub-basin. In-lake sediment focusing had little influence on the spatial distributions of all metals, different from the traditional sediment focusing pattern observed in small lakes. Anthropogenic Cd accumulation in sediments ranged from 1.5 to 10.1 mg m − 2 in a specific core with an average of 6.5 mg m − 2 for the entire lake, highlighting that a reliable whole-lake pollutant budget requires an analysis of multiple cores. Our study suggests that the management of aquatic ecosystem health should take the remobilization of in-watershed stored pollutants into consideration especially under increasing human perturbation.

This study investigated the impact of soil type and rice cultivars on variations in the iron plaque formation and cadmium (Cd) accumulation by different portions of rice seedlings under the influence of Fe amendment. The experiments were performed in pots under glasshouse conditions using two typical paddy soils. Rice seedlings were exposed to three concentrations of Cd (0, 1 and 3 mg kg−1 soil) and Fe (0, 1.0 and 2.0 g kg−1 soil). The results revealed that shoot biomass decreased by 12.2–23.2% in Quest and 12.8–30.8% in Langi in the Cd1.0 and Cd3.0 treatments, while shoot biomass increased by 11.2–19.5% in Quest and 26–43.3% in Langi in Fe1.0 and Fe2.0 as compared to the Fe control. The Cd concentration in the roots and shoots of rice seedlings were in the order of Langi cultivar &gt, Quest cultivar, but the Fe concentration in rice tissues showed the reverse order. Fe plaque formations were promoted by Fe application, which was 7.8 and 10.4 times higher at 1 and 2 g kg−1 Fe applications compared to the control Fe treatment. The Quest cultivar exhibited 13% higher iron plaque formation capacity compared to the Langi cultivar in both soil types. These results indicate that enhanced iron plaque formation on the root surface was crucial to reduce the Cd concentration in rice plants, which could be an effective strategy to regulate grain Cd accumulation in rice plants.

Environment quality of suburban and urban lakes receives special attention due to their great impacted by human perturbations and important roles in ecosystem services. Herein, the spatio-temporal variations of 10 metal and metalloid elements in 13 sediment cores from a large suburban lake (Dianchi) were studied to explore the changes in sedimentary environment and pollution and their associations with human activities since the last century. Concentrations of each element were largely varied at spatial scales, but showed similar vertical trends among the profiles, suggesting comparable changes in sedimentary processes in each lake region. Cluster analysis showed two groups of elements: group I includes Al, Ti, Cu, Cr and Ni, and group II includes As, Cd, Hg, Pb and Zn. Temporally, concentrations of all elements were generally constant until the 1950s. Thereafter, group I elements along with the clay percentage started to decrease, indicating accelerated input of coarser soils due to strengthening human perturbation and changing land use. However, group II elements showed increasing values of concentrations, particularly the enrichment factors (EF = 1.0–10.8), which peaked between mid-1990s and 2000, indicating continued pollutants input with watershed economic development. With the implementation of environment management measures, pollution was initially restrained or reduced in recent decades as indicated by the stable EFs and sedimentary fluxes of Cd, Hg, Pb and Zn and decreasing values of As. Spatially, the stocks of anthropogenic As, Cd, Hg, Pb and Zn were higher in the northern while lower in the southern lake area. This spatial difference was mainly due to the large input of industrial and domestic wastewaters in the northern compared to the area in the southern that receives runoff from agricultural and forested land. Overall, the spatio-temporal patterns in accumulation of metal and metalloid elements in the lake reliably reflected the impacts of watershed human activities.

Inland waterbodies play an important role in the global carbon cycle, acting both as carbon sources with organic carbon (OC) mineralization and as sinks with OC burial in sediments. Under recent impacts of global warming, anthropogenic land-use change and nutrient supply, however, there is a limited knowledge regarding OC dynamics in sediments of large, deep lakes especially in subtropical alpine regions. Here, we studied the patterns of OC burial and the potential regulating factors using multiple sedimentary proxies and observational records in Lugu Lake (southwest China) over the past ~100 years. Comparisons of 15 sediment cores in different areas of the lake reveal similar temporal trends in OC content and other sediment parameters, indicating coherent patterns of whole-lake sedimentary environmental change dominated by watershed human perturbation. Based on C/N ratios and δ13Corg analyses, the sediment OC has primarily been autochthonous in source. OC accumulation rates (OCAR) increased during 1880–1980, from ~14 to 43 g C m−2 yr−1 in a central core (LGS), mainly resulting from elevated primary production under increased phosphorus input and soil erosion. Subsequently, OCAR decreased considerably to ~15 g C m−2 yr−1, although the phosphorus supply and lake primary productivity remained high. We infer the OCAR decline likely resulted from increased organic matter decomposition and OC mineralization in the water column because of climate warming and lake-water thermal stratification. This phenomenon might mask the positive contribution of primary production to OC burial. Our findings suggest that the commonly observed synergistically positive effects of warming and eutrophication on sediment OC burial may be impaired in deep lakes, which needs further investigations across ecological, climatic and land-use gradients.

Summary The present study examines the groundwater and surface water geochemistry of two different geomorphic domains within the Chakdaha block, West Bengal, in an attempt to decipher potential influences of groundwater abstraction on the hydrochemical evolution of the aquifer, the effect of different water inputs (monsoon rain, irrigation and downward percolation from surface water impoundments) to the groundwater system and concomitant As release. A low-land flood plain and a natural levee have been selected for this purpose. Although the stable isotopic signatures of oxygen (δ18O) and hydrogen (δ2H) are largely controlled by local precipitation, the isotopic composition falls sub-parallel to the Global Meteoric Water Line (GMWL). The Cl/Br molar ratio indicates vertical recharge into the wells within the flood plain area, especially during the post-monsoon season, while influences of both evaporation and vertical mixing are visible within the natural levee wells. Increase in mean DOC concentrations (from 1.33 to 6.29 mg/L), from pre- to post-monsoon season, indicates possible inflow of organic carbon to the aquifer during the monsoonal recharge. Concomitant increase in AsT, Fe(II) and HCO3− highlights a possible initial episode of reductive dissolution of As-rich Fe-oxyhydroxides. The subsequent sharp increase in the mean As(III) proportions (by 223%), particularly in the flood plain samples during the post-monsoon season, which is accompanied by a slight increase in mean AsT (7%) may refer to anaerobic microbial degradation of DOC coupled with the reduction of As(V) to As(III) without triggering additional As release from the aquifer sediments.

Urban environment continues to expand at an unprecedented rate to meet the demand of increasing population and economic development. The resulting changes to landscapes have increased stress to hydrological cycles, biogeochemical processes, and environmental sustainability of natural resources. This study evaluated spatio-temporal changes of land use and land cover (LULC) between 1990 and 2020 in Guwahati city, India. Time-series Landsat satellite images were analyzed using supervised classification schemes followed by quantification of LULC change over time. Five broad LULC classes were identified on the basis of spectral reflectance signature. Confusion matrix determined high classification accuracy with Kappa Coefficient >0.81 in all cases. The results showed that the urban built environment has doubled in area in 30 years (1990–2020). The urban environments have increased at the expense of vegetation, fallow land, and open areas and to some extent wetlands. Notably, the expansions of urban areas have taken place from city center to the south, to the south-east, and along the east-west National Highway 37 connecting other NE States of India. There is no clear indication of change in the amount of precipitation in response to urbanization. However, analysis of long-term groundwater level data suggests a steady decline in the depth to groundwater level. The declining trend is attributed to urbanization and population growth. The increase in impervious surface coverage due to urbanization have extensively reduced the areas of high potential groundwater recharge zones and thereby dropping the level of groundwater in the wells.

Estuarine sedimentary environments safeguard aquatic ecosystem health by attenuating and transforming catchment-derived contaminants. Currently these environments are under severe stress from trace element contamination due to urbanization. Sediments of Sydney estuary (Australia) are highly elevated in a range of metals due to a long period of intense urbanization and industrialization, which has had a considerable influence on coastal ecosystem health and functioning. A three-stage sequential procedure following Bureau Communautaire de Référence (Community Bureau of Reference-BCR) technique was applied to sediments collected from Sydney estuary to determine their quality, elemental partitioning and ecosystem risk in three human-impacted environmental settings (i.e., mangrove-dominated, stormwater-dominated and industrial-dominated sites) and a control site in this coastal ecosystem. In all three environmental settings, Pb and Zn concentrations exceeded Australian Interim Sediment Quality Guidelines-High (ISQG-High) values and were mostly associated with the reducible and acid soluble fractions, respectively. Copper and Cr also exceeded ISQG-High values (especially in the industrial-dominated site), however the majority of these metals were associated with the oxidizable fraction. Arsenic and Ni concentrations were mostly below ISQG-High values (except one of the stormwater-dominated sites) and were associated with the residual fraction. These results suggest that the most easily mobilized metal was Zn followed by Pb and these metals together presented a risk to estuarine ecosystems in the three selected environmental settings. However, these metals are not always the most abundant in tissue of mangroves, oysters or prawns suggesting other mechanisms are important in a complex uptake process.

Summary The transport of arsenic (As) in groundwater is known to be considerably controlled by the adsorption behavior of aquifer sediments and changes in subsurface redox conditions. Here we report wet chemical analyses of As(III) adsorption onto oxidized, low As containing Holocene aquifer sediments from West Bengal, India. Batch experiments in an open laboratory atmosphere show that the slow removal of As(III) from aqueous solution is a resulting effect of adsorption and oxidation which is not significantly influenced by the changes in pH (6.0–9.1). The isotherm data were fitted with Freundlich and Langmuir equations and maximum adsorption density (Γmax ≈ 0.40 mmol kg−1) obtained is lower than that for As(V) at pH 7.5 (0.95 mmol kg−1). The estimated distribution coefficient maxima (Kd max) values are within the ranges of Kd values previously reported in case of Holocene aquifer sediments of West Bengal, India and Bangladesh. The low adsorption capacity of oxidized Holocene aquifer sediments in this study compared to oxidized Pleistocene sediments of Bangladesh is attributed to coarser grain sizes and low abundance of Fe-oxyhydroxides and micas which act as a potential sink of As. This study has important implications for As(III) attenuation and transport in the shallow aquifers (especially around the zone of ‘maximum’ water table fluctuations, i.e., 10–20 m depth below ground surface) when oxygen-depleted (anoxic) Holocene aquifers get in contact with oxygen (e.g., by irrigation/groundwater drawdown) and also for predicting possible future risk associated with its transport from shallow aquifers to present day “low-As” containing deeper aquifers of West Bengal, India.

Mangrove forests act as a natural filter of land-derived wastewaters along industrialized tropical and sub-tropical coastlines and assist in maintaining a healthy living condition for marine ecosystems. Currently, these intertidal communities are under serious threat from heavy metal contamination induced by human activity associated with rapid urbanization and industrialization. Studies on the biotic responses of these plants to heavy metal contamination are of great significance in estuary management and maintaining coastal ecosystem health. The main objective of the present investigation was to assess the biotic response in Avicennia marina ecosystems to heavy metal contamination through the determination of metal concentrations in leaves, fine nutritive roots and underlying sediments collected in fifteen locations across Sydney Estuary (Australia). Metal concentrations (especially Cu, Pb and Zn) in the underlying sediments of A. marina were enriched to a level (based on Interim Sediment Quality Guidelines) at which adverse biological effects to flora could occasionally occur. Metals accumulated in fine nutritive roots greater than underlying sediments, however, only minor translocation of these metals to A. marina leaves was observed (mean translocation factors, TFs, for all elements

Mangrove sediment has long been recognized as being important in restricting the mobility of contaminants in estuarine environments. To investigate the role of rhizosphere processes in the accumulation of trace metals in mangrove fine nutritive roots, the mangrove sediments and associated fine nutritive roots are collected from five major embayments of Sydney estuary (Australia) for geochemical studies. In this estuary Avicennia marina sediments are accumulating large quantities of trace metals due to presence of abundant fine sediment (

Dissolved organic carbon (DOC) and Fe mineral phases are known to influence the mobility of arsenic (As) in groundwater. Arsenic can be associated with colloidal particles containing organic matter and Fe. Currently, no data is available on the dissolved phase/colloidal association of As in groundwater of alluvial aquifers in West Bengal, India. This study investigated the fractional distribution of As (and other metals/metalloids) among the particulate, colloidal and dissolved phases in groundwater to decipher controlling behavior of organic and inorganic colloids on As mobility. The result shows that 83-94% of As remained in the 'truly dissolved' phases (i.e.,0.05 μm size). Strong positive correlation between Fe and As (r(2) between 0.65 and 0.94) is mainly observed in the larger (i.e.,0.05 μm size) colloidal particles, which indicates the close association of As with larger Fe-rich inorganic colloids. In smaller (i.e.,0.05 μm size) colloidal particles strong positive correlation is observed between As and DOC (r(2)=0.85), which highlights the close association of As with smaller organic colloids. As(III) is mainly associated with larger inorganic colloids, whereas, As(V) is associated with smaller organic/organometallic colloids. Scanning Electron Microscopy and Energy Dispersive X-ray spectroscopy confirm the association of As with DOC and Fe mineral phases suggesting the formation of dissolved organo-Fe complexes and colloidal organo-Fe oxide phases. Attenuated total reflectance-Fourier transform infrared spectroscopy further confirms the formation of As-Fe-NOM organometallic colloids, however, a detailed study of these types of colloids in natural waters is necessary to underpin their controlling behavior.

A comparative hydrogeochemical study was carried out in West Bengal, India covering three physiographic regions, Debagram and Chakdaha located in the Bhagirathi-Hooghly alluvial plain and Baruipur in the delta front, to demonstrate the control of geogenic and anthropogenic influences on groundwater arsenic (As) mobilization. Groundwater samples (n = 90) from tube wells were analyzed for different physico-chemical parameters. The low redox potential (Eh = -185 to -86 mV) and dominant As(III) and Fe(II) concentrations are indicative of anoxic nature of the aquifer. The shallow (100 m) and deeper (100 m) aquifers of Bhagirathi-Hooghly alluvial plains as well as shallow aquifers of delta front are characterized by Ca(2+)HCO3(-) type water, whereas Na(+) and Cl(-) enrichment is found in the deeper aquifer of delta front. The equilibrium of groundwater with respect to carbonate minerals and their precipitation/dissolution seems to be controlling the overall groundwater chemistry. The low SO4(2-) and high DOC, PO4(3-) and HCO3(-) concentrations in groundwater signify ongoing microbial mediated redox processes favoring As mobilization in the aquifer. The As release is influenced by both geogenic (i.e. geomorphology) and anthropogenic (i.e. unsewered sanitation) processes. Multiple geochemical processes, e.g., Fe-oxyhydroxides reduction and carbonate dissolution, are responsible for high As occurrence in groundwaters.

Several million people around the world are currently exposed to excessive amounts of arsenic (As) and fluoride (F) in their drinking water. Although the individual toxic effects of As and F have been analyzed, there are few studies addressing their co-occurrences and water treatment options. Several studies conducted in arid and semi-arid regions of Latin America show that the co-occurrences of As and F in drinking water are linked to the volcaniclastic particles in the loess or alluvium, alkaline pH, and limited recharge. The As and F contamination results from water-rock interactions and may be accelerated by geothermal and mining activities, as well as by aquifer over-exploitation. These types of contamination are particularly pronounced in arid and semi-arid regions, where high As concentrations often show a direct relationship with high F concentrations. Enrichment of F is generally related to fluorite dissolution and it is also associated with high Cl, Br, and V concentrations. The methods of As and F removal, such as chemical precipitation followed by filtration and reverse osmosis, are currently being used at different scales and scenarios in Latin America. Although such technologies are available in Latin America, it is still urgent to develop technologies and methods capable of monitoring and removing both of these contaminants simultaneously from drinking water, with a particular focus towards small-scale rural operations.

The fouling of periphyton biofilm is a common problem associated with surface water treatment systems. In this study, sulfuric acid (H2SO4), sodium acetate (CH3COONa) and ethylenediamine tetra-acetic acid (EDTA) solutions were sequentially used to clean periphyton biofilms collected from a surface water treatment system. The results showed that the sequential addition of H2SO4 and CH3COONa solutions could accelerate the exfoliation of the fouled periphyton biofilm, while the addition of EDTA solution could regenerate the periphyton biofilm. However, the addition of H2SO4 and CH3COONa solution might negatively affect the bacterial community structure, while the addition of EDTA solution facilitated improvement of the community structure. The combined effect of cleaning and regeneration of periphyton biofilm has significantly improved the removal efficiencies of chemical oxygen demand (COD), total phosphorus (TP), total nitrogen (TN) and ammonia (NH4-N), by 19, 20, 23 and 22%, respectively. The removal processes of COD, TP, TN and NH4-N by the cleaned biofilm were fitted to power regression curves, while those by the control biofilm during the removal process were fitted to polynomial regression curves. These systemic results indicate that the sequential addition of H2SO4, CH3COONa and EDTA solution is able to clean fouled periphyton biofilm and to enhance the efficiency of surface water treatment systems.

Atmospheric lead (Pb) pollution during the last century in central Yunnan province, one of the largest non-ferrous metal production centers in China, was reconstructed using sediment cores collected from Fuxian and Qingshui Lakes. Lead concentrations and isotopic ratios ((207)Pb/(206)Pb and (208)Pb/(206)Pb) were measured in sediment cores from both lakes. The operationally defined chemical fractions of Pb in sediment core from Fuxian Lake were determined by the optimized BCR procedure. The chronology of the cores was reconstructed using (210)Pb and (137)Cs dating methods. Similar three-phase variations in isotopic ratios and enrichment factors of Pb were observed in the sediment cores from both lakes. Before the 1950s, the sediment data showed low (207)Pb/(206)Pb and (208)Pb/(206)Pb ratios and enrichment factors (EFs=~1), indicating that the sedimentary Pb was predominantly of lithogenic origin. However, these indices were increased gradually between the 1950s and the mid-1980s, implying an atmospheric Pb deposition. The EFs and isotopic ratios of Pb reached their peak during recent years, indicating aggravating atmospheric Pb pollution. The average anthropogenic Pb fluxes since the mid-1980s were estimated to be 0.032 and 0.053 g m(-2) year(-1) recorded in Fuxian and Qingshui cores, respectively. The anthropogenic Pb was primarily concentrated in the reducible fraction. Combining the results of Pb isotopic compositions and chemical speciations in the sediment cores and in potential sources, we deduced that recent aggravating atmospheric Pb pollution in central Yunnan province should primarily be attributed to regional emissions from non-ferrous metal production industries.

[1] Groundwater-dependent ecosystems (GDEs) in arid and semiarid environments play significant ecological roles, and, yet in many parts of the world, these ecosystems have been drained for agricultural use. In wetlands containing acid sulfate soils, the altered hydrology may trigger acidification and subsequent trace metal release. Quantifying shifts in hydrological regime and connectivity dynamics across wetlands is critical for understanding the resilience of these GDEs to anthropogenic impacts. Seasonal water balances for a wetland severely impacted by drainage and acidification were combined with laboratory geochemical data and field observations to develop a conceptual model describing hydrological connectivity across the wetland. The data indicated that, with the onset of the dry season, the superficial aquifer was lowered, exposing sulfides that oxidized to form sulfuric acid and dissolving metal salts. The following dry season enhanced capillary action causing upwelling of oxidized products to the surface where evaporative precipitation created acidity scalds. Subsequent winter rainfall and infiltration caused groundwater levels to rise, intersect with the ground surface, and form disconnected acidic pools. As the wet season progressed, connectivity was established between the pools, resulting in metal-rich acid discharge from the wetland. The degree of acid fluxes and metal release was controlled by the physicochemical characteristics of the soils, its exposure to the seasonally variable wetland hydrology, antecedent hydrological conditions, hydrological connectivity (both vertical and horizontal), and the resulting biogeochemical conditions.

The water quality and chemistry of the groundwater of the fluvial Bengal plains have been investigated. It has been found that shallow aquifers (< 50 m bgl) are contaminated in a few pockets, surrounded by areas with low arsenic (As)/As-free groundwater, while the deeper aquifer (> 100 m bgl) is generally free from As (< 10μg/L). It also reveals that multiple As mobilization processes are occurring simultaneously, rather than any single geochemical process. An attempt has been made to demonstrate the degree of As heterogeneity with groundwater quality, and this has been followed by a few local conditions. The study further suggests that the As distribution (spatio-vertical) helps to identify safe shallow aquifers, and several signatures (colour of the sediments/land use pattern/geomorphological features/local recharge events) are apparent that can be useful for formulating long-term mitigation options.

Delineation of safe aquifer(s) that can be targeted by cheap drilling technology for tubewell (TW) installation becomes highly imperative to ensure access to safe and sustainable drinking water sources for the arsenic (As) affected population in Bengal Basin. This study investigates the potentiality of brown sand aquifers (BSA) as a safe drinking water source by characterizing its hydrogeochemical contrast to grey sand aquifers (GSA) within shallow depth (70 m) over an area of 100 km(2) in Chakdaha Block of Nadia district, West Bengal, India. The results indicate that despite close similarity in major ion composition, the redox condition is markedly different in groundwater of the two studied aquifers. The redox condition in the BSA is delineated to be Mn oxy-hydroxide reducing, not sufficiently lowered for As mobilization into groundwater. In contrast, the enrichments of NH(4)(+), PO(4)(3-), Fe and As along with lower Eh in groundwater of GSA reflect reductive dissolution of Fe oxy-hydroxide coupled to microbially mediated oxidation of organic matter as the prevailing redox process causing As mobilization into groundwater of this aquifer type. In some portions of GSA the redox status even has reached to the stage of SO(4)(2-) reduction, which to some extent might sequester dissolved As from groundwater by co-precipitation with authigenic pyrite. Despite having low concentration of As in groundwater of the BSA the concentration of Mn often exceeds the drinking water guidelines, which warrants rigorous assessment of attendant health risk for Mn prior to considering mass scale exploitation of the BSA for possible sustainable drinking water supply.

Many regions of Latin America are widely reported for the occurrence of high arsenic (As) in groundwater and surface water due to a combination of geological processes and/or anthropogenic activities. In this paper, we review the available literature (both in English and Spanish languages) to delineate human As exposure pathways through the food chain. Numerous studies show that As accumulations in edible plants and crops are mainly associated with the presence of high As in soils and irrigation waters. However, factors such as As speciation, type and composition of soil, and plant species have a major control on the amount of As uptake. Areas of high As concentrations in surface water and groundwater show high As accumulations in plants, fish/shellfish, livestock meat, milk and cheese. Such elevated As concentrations in food may result in widespread health risks to local inhabitants, including health of indigenous populations and residents living close to mining industries. Some studies show that As can be transferred from the water to prepared meals, thereby magnifying the As content in the human diet. Arsenic speciation might also change during food preparation, especially during high temperature cooking, such as grilling and frying. Finally, the review of the available literature demonstrates the necessity of more rigorous studies in evaluating pathways of As exposure through the human food chain in Latin America.

Drinking of arsenic (As)-contaminated groundwater has adverse effects on health of millions of people worldwide. This study aimed to determine the degree of severity of As exposure from drinking water in peri-urban Moyna and Ardebok villages, West Bengal, India. Arsenic concentrations in hair, nail and urine samp les of the individuals were determined. Arsenical dermatosis, keratosis and melanosis were investigated through medical evaluation. We have evaluated the association between As exposure from drinking water, and keratosis and melanosis outcomes. The results showed that 82.7 % of the sampled tube wells contain As concentrations above 10 μg/L, while 57.7 % contain As concentrations above 50 μg/L. The hair, nail and urine As concentrations were positively correlated with As concentrations in drinking water. In our study population, we observed a strong association between As concentrations ranging 51-99 μg/L and keratosis and melanosis outcomes, although the probability decreases at higher concentration ranges perhaps due to switching away from the use of As-contaminated tube wells for drinking and cooking purposes. High As concentrations in hair, nail and urine were observed to be associated with the age of the study population. The level of As concentrations in hair, nail and urine samples of the study population indicated the degree of severity of As exposure in the study region.