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| 1 | Arsenic contamination of groundwater:A global synopsis with focus on the Indian Peninsula显示文摘More than 2.5 billion people on the globe rely on groundwater for drinking and providing high-quality drinking water has become one of the major challenges of human society.Although groundwater is considered as safe,high concentrations of heavy metals like arsenic(As)can pose potential human health concerns and hazards.In this paper,we present an overview of the current scenario of arsenic contamination of groundwater in various countries across the globe with an emphasis on the Indian Peninsula.With several newly affected regions reported during the last decade,a significant increase has been observed in the global scenario of arsenic contamination.It is estimated that nearly 108 countries are affected by arsenic contamination in groundwater with concentration beyond maximum permissible limit of 10 ppb recommended by the World Health Organization.The highest among these are from Asia(32)and Europe(31),followed by regions like Africa(20),North America(11),South America(9)and Australia(4).More than 230 million people worldwide,which include 180 million from Asia,are at risk of arsenic poisoning.Southeast Asian countries,Bangladesh,India,Pakistan,China,Nepal,Vietnam,Burma,Thailand and Cambodia,are the most affected.In India,20 states and 4 Union Territories have so far been affected by arsenic contamination in groundwater.An attempt to evaluate the correlation between arsenic poisoning and aquifer type shows that the groundwater extracted from unconsolidated sedimentary aquifers,particularly those which are located within the younger orogenic belts of the world,are the worst affected.More than 90%of arsenic pollution is inferred to be geogenic.We infer that alluvial sediments are the major source for arsenic contamination in groundwater and we postulate a strong relation with plate tectonic processes,mountain building,erosion and sedimentation.Prolonged consumption of arsenic-contaminated groundwater results in severe health issues like skin,lung,kidney and bladder cancer;coronary heart disease;bronchiectasis;hyperkeratosis and arsenicosis.Since the major source of arsenic in groundwater is of geogenic origin,the extend of pollution is complexly linked with aquifer geometry and aquifer properties of a region.Therefore,remedial measures are to be designed based on the source mineral,climatological and hydrogeological scenario of the affected region.The corrective measures available include removing arsenic from groundwater using filters,exploring deeper or alternative aquifers,treatment of the aquifer itself,dilution method by artificial recharge to groundwater,conjunctive use,and installation of nano-filter,among other procedures.The vast majority of people affected by arsenic contamination in the Asian countries are the poor who live in rural areas and are not aware of the arsenic poisoning and treatment protocols.Therefore,creating awareness and providing proper medical care to these people remain as a great challenge.Very few policy actions have been taken at international level over the past decade to reduce arsenic contamination in drinking water,with the goal of preventing toxic impacts on human health.We recommend that that United Nations Environment Programme(UNEP)and WHO should take stock of the global arsenic poisoning situation and launch a global drive to create awareness among people/medical professionals/health workers/administrators on this global concern. | E.Shaji M.Santosh K.V.Sarath Pranav Prakash V.Deepchand B.V.Divya | 2021 | Geoscience Frontiers2021，12，3： | 14 |
| 2 | Fluoride contamination in groundwater resources of Alleppey,southern India显示文摘Alleppey is one of the thickly populated coastal towns of the Kerala state in southern India.Groundwater is the main source of drinking water for the 240,991 people living in this region.The groundwater is being extracted from a multi-layer aquifer system of unconsolidated to semi-consolidated sedimentary formations,which range in age from Recent to Tertiary.The public water distribution system uses dug and tube wells.Though there were reports on fluoride contamination,this study reports for the first time excess fluoride and excess salinity in the drinking water of the region.The quality parameters,like Electrical Conductivity(EC) ranges from 266 to 3900 μs/cm,the fluoride content ranges from 0.68 to2.88 mg/L,and the chloride ranges between the 5.7 to 1253 mg/L.The main water types are Na-HC03,NaCO_3 and Na-Cl.The aqueous concentrations of F^- and CO_3^(2-) show positive correlation whereas F^- and Ca^(2+) show negative correlation.The source of fluoride in the groundwater could be from dissolution of fluorapatite,which is a common mineral in the Tertiary sediments of the area.Long residence time,sediment-groundwater interaction and facies changes(Ca-HCO_3 to Na-HCO_3) during groundwater flow regime are the major factors responsible for the high fluoride content in the groundwater of the area.High strontium content and high EC in some of the wells indicate saline water intrusion that could be due to the excess pumping from the deeper aquifers of the area.The water quality index computation has revealed that 62%of groundwater belongs to poor quality and is not suitable for domestic purposes as per BIS and WHO standards.Since the groundwater is the only source of drinking water in the area,proper treatment strategies and regulating the groundwater extraction are required as the quality deterioration poses serious threat to human health. | Dhanya Raj E.Shaji | 2017 | Geoscience Frontiers2017，8，1： | 6 |
| 3 | Phase equilibrium modeling of incipient charnockite formation in NCKFMASHTO and MnNCKFMASHTO systems:A case study from Rajapalaiyam,Madurai Block,southern India显示文摘早期的 charnockites 在 mesoscopic 规模上代表 granulite 形成并且在在深外壳中理解液体过程收到了可观的注意。这里,我们在马杜赖·布洛克,在 Rajapalaiyam 从一个早期的 charnockite 地区报导新 petrological 数据南部的印度,并且基于矿物质阶段平衡建模和 pseudosection 分析讨论 petrogenesis。Rajapalaiyam 是在从的南部的印度的一个关键地区诊断矿物质集合为超离频温度(UHT ) 变态被报导了。对岩石是的 UHT 近似在我们在这报导的 Opx 免费的 Grt-Bt 片麻岩(Kfs +Pl +Qtz +Bt +Grt +Ilm + 山) 以内发生的 charnockite (Kfs +Qtz +Pl +Bt +Opx +Grt + Ilm ) 的补丁和透镜学习。矿物质平衡在 NCKFMASHTO 系统在 charnockitic 集合上当模特儿的申请产出 820 杯 ? 的一个磅范围 ?? 瑮湥楳敶瀠牡浡瑥牥 ?? 嘊湥慤丠癯 ? 汐瑵湯※ ? 牁 ? 慵傖悑 ??? 鎬?? 抑貮吗?? | Takahiro Endo Toshiaki Tsunogae M.Santosh E.Shaji | 2012 | Geoscience Frontiers2012，3，6： | 4 |
| 4 | Detrital zircon geochronology of quartzites from the southern Madurai Block,India:Implications for Gondwana reconstruction显示文摘Detrital zircons are important proxies for crustal provenance and have been widely used in tracing source characteristics and continental reconstructions.Southern Peninsular India constituted the central segment of the late Neoproterozoic supercontinent Gondwana and is composed of crustal blocks ranging in age from Mesoarchean to late Neoproterozoic-Cambrian.Here we investigate detrital zircon grains from a suite of quartzites accreted along the southern part of the Madura) Block.Our LA-ICPMS U-Pb dating reveals multiple populations of magmatic zircons,among which the oldest group ranges in age from Mesoarchean to Paleoproterozoic(ca.2980-1670 Ma,with peaks at 2900-2800 Ma,2700-2600 Ma,2500-2300 Ma,2100-2000 Ma).Zircons in two samples show magmatic zircons with dominantly Neoproterozoic(950-550 Ma) ages.The metamorphic zircons from the quartzites define ages in the range of 580-500 Ma,correlating with the timing of metamorphism reported from the adjacent Trivandrum Block as well as from other adjacent crustal fragments within the Gondwana assembly.The zircon trace element data are mostly characterized by LREE depletion and HREE enrichment,positive Ce,Sm anomalies and negative Eu,Pr,Nd anomalies.The Mesoarchean to Neoproterozoic age range and the contrasting petrogenetic features as indicated from zircon chemistry suggest that the detritus were sourced from multiple provenances involving a range of lithologies of varying ages.Since the exposed basement of the southern Madurai Block is largely composed of Neoproterozoic orthogneisses,the data presented in our study indicate derivation of the detritus from distal source regions implying an open ocean environment.Samples carrying exclusive Neoproterozoic detrital zircon population in the absence of older zircons suggest proximal sources in the southern Madurai Block.Our results suggest that a branch of the Mozambique ocean might have separated the southern Madurai Block to the north and the Nagercoil Block to the south,with the metasediments of the khondalite belt in Trivandrum Block marking the zone of ocean closure,part of which were accreted onto the southern Madurai Block during the collisional amalgamation of the Gondwana supercontinent in latest Neoproterozoic-Cambrian. | Shan-Shan Li M.Santosh G.Indu E.Shaji T.Tsunogae | 2017 | Geoscience Frontiers2017，8，4： | 3 |
| 5 | Machine-learning based landslide susceptibility modelling with emphasis on uncertainty analysis显示文摘Landslide susceptibility maps are vital tools used by decision-makers to adopt mitigation strategies for future calamities.In this context,research on landslide susceptibility modelling has become a topic of relevance and is in constant evolution.Though various machine-learning techniques(MLTs)have been identified for landslide susceptibility modelling,the uncertainty inherent in the models is rarely considered.The present study attempts to quantify the uncertainty associated with landslide prediction models by developing a new methodological framework based on the ensembles of the eight MLTs.This methodology has been tested at the highlands of the southern Western Ghats region(Kerala,India),where landslides have frequently been occurring.Fourteen landslide conditioning factors have been identified as part of this study,and their association was correlated with 671 historic landslides in the study area.The study used four ensemble models such as the mean of probabilities,the median of probabilities,the weighted mean of probabilities,and the committee average.The weighted mean of probability was proved to be the best model based on the average of 800 standalone MLTs,viz.,receiver operating characteristics,true skill statistics,and area under curve with corresponding validation scores.Thereafter,an uncertainty analysis was carried out on the coefficient of variation.A confident map was generated to represent the distinct zonation of landslide susceptibility areas with definite uncertainty scales.Nearly 74%of the past landslides fall in the higher susceptibility-low uncertainty category.It is also inferred that such micro-level zonation based on MLTs may improve the efficiency of landslide susceptibility maps and may help in accurately identifying landslide-prone areas in the future.The confident maps thus generated can be used as a ready reference to the planners for the formulation of landslide adaptation strategies at micro-scales. | A.L.Achu C.D.Aju Mariano Di Napoli Pranav Prakash Girish Gopinath E.Shaji Vinod Chandra | 2023 | Geoscience Frontiers2023，14，6： | 0 |
| 6 | Extensional collapse of the Gondwana orogen: Evidence from Cambrian mafic magmatism in the Trivandrum Block, southern India显示文摘The assembly of Late Neoproterozoice Cambrian supercontinent Gondwana involved prolonged subduction and accretion generating arc magmatic and accretionary complexes, culminating in collision and formation of high grade metamorphic orogens. Here we report evidence for mafic magmatism associated with post-collisional extension from a suite of gabbroic rocks in the Trivandrum Block of southern Indian Gondwana fragment. Our petrological and geochemical data on these gabbroic suite show that they are analogous to high Fe tholeiitic basalts with evolution of the parental melts dominantly controlled by fractional crystallization. They display enrichment of LILE and LREE and depletion of HFSE with negative anomalies at Zre Hf and Ti corresponding to subduction zone magmatic regime. The tectonic affinity of the gabbros coupled with their geochemical features endorse a heterogeneous mantle source with collective melt contributions from sub-slab asthenospheric mantle upwelling through slab break-off and arc-related metasomatized mantle wedge, with magma emplacement in subduction to post-collisional intraplate settings. The high Nb contents and positive Nbe Ta anomalies of the rocks are attributed to inflow of asthenospheric melts containing ancient recycled subducted slab components and/or fusion of subducted slab materials owing to upwelling of hot asthenosphere. Zircon grains from the gabbros show magmatic crystallization texture with low U and Pb content. The LA-ICPMS analyses show ^(206) Pb/^(238) U mean ages in the range of 507-494 Ma suggesting Cambrian mafic magmatism. The post-collisional mafic magmatism identified in our study provides new insights into mantle dynamics during the waning stage of the birth of a supercontinent. | Qiong-Yan Yang Sohini Ganguly E.Shaji Yunpeng Dong V.Nanda-Kumar | 2019 | Geoscience Frontiers2019，10，1： | 0 |
| 7 | Fluoride contamination in groundwater:A global review of the status,processes,challenges,and remedial measures显示文摘Groundwater pollution by fluoride is one of the prime concerns of the world population due to its toxicity,which results in adverse health impacts.In this paper,we review the current scenario of the fluoride contamination of groundwater in various countries across the globe and its impact on human health.During the last decade,several newly affected regions have been reported all over the world,with more than 100 countries affected by fluoride contamination in groundwater(concentration exceeding the acceptable limit of 1.5 mg/L defined by the World Health Organization).Fluoride poisoning is mainly due to the unsupervised ingestion of products for dental and oral hygiene and over-fluoridated drinking water.It is estimated that more than 200 million people from different countries are affected by fluoriderelated groundwater issues and health problems.The highest among these are from the countries in Africa(38),Asia(28),and Europe(24),followed by countries like South America(5),North America(3),and Australia(2).The source of fluoride in drinking water is primarily geogenic,together with forage,grasses and grains,tea,and anthropogenic sources.These countries affected were correlated with climatic zones and geological factors to gain insights into geospatial relations.Our analyses show that most of the fluoride pollution-prone zones are located in high-grade metamorphic terranes with granitoid or alkaline intrusions,geothermal hot springs,and volcanic regions with arid or semi-arid climatic conditions.This study also finds that children across the globe are more vulnerable than adults to fluoride contamination.The review finds that,although there are efficient fluoride removal techniques,including filters with next-generation nanomaterials,to date,there has not been a single technique developed that can claim to be a practically robust solution for fluoride removal from drinking water.Therefore,we suggest developing next-generation filters that can retain essential minerals in water and remove only harmful ones and selecting purification technologies according to need,climate,geology,and geographic location.The findings from our review would help policymakers take effective and sustainable measures for safe water supply in the affected areas.Within the framework of the Sustainable Development Goals(SDGs),particularly SDG 3(Good Health and Well-being)and SDG 6(Clean Water and Sanitation),this study emphasizes the critical role of fluoride as a key indicator.It underscores the imperative of addressing elevated fluoride levels in drinking water,particularly in African and Asian countries,to achieve the overarching objective of universal and equitable access to safe,affordable,and uncontaminated drinking water for global society by the targeted year of 2030. | E.Shaji K.V.Sarath M.Santosh P.K.Krishnaprasad B.K.Arya Manisha S.Babu | 2024 | Geoscience Frontiers2024，15，2： | 0 |
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