Determination of the major geochemical processes of groundwater along the Cretaceous-Tertiary boundary of Trichinopoly,Tamilnadu,India

The hydrogeochemical variations in groundwater are mainly influenced by lithology,residence time of water in the aquifer matrix,and anthropogenic activities.This study was focused on the geochemical variations of groundwater in different lithological units(Archaean,Cretaceous,Tertiary,and Quaternary)by understanding the major factors governing the geochemical variations in each lithology.The 71 groundwater samples were collected from these rock types,namely,Archaean(14),Cretaceous(37),Tertiary(11),Quaternary(9).The collected samples were measured for major ions and they were used for preparation of standard geochemical plots and ionic ratios.Factor analysis and factor score were used to identify the major factors controlling the hydrochemistry and their spatial distribution in the study area.In addition,geochemical model,WATEQ 4 F was used to determine the saturation condition of carbonate and sulphate minerals in the groundwater.Na–Cl and mixed Ca–Na–HCO3 were the dominant hydrochemical facies irrespective of lithological units.The overall interpretation of geochemical data revealed that leaching of secondary salts,weathering and ion exchange reaction along the groundwater flow path through various lithological units,and anthropogenic influence from domestic sewages and agricultural activities constitute the major geochemical processes in the study area.Hence,this study brings out the multiple hydrogeochemical process in the complex geological terrain along the Cretaceous-Tertiary boundary.

Modeling the Hydrogeochemical Processes and Source of Ions in the Groundwater of Aquifers within Kasra-Nukhaib Region (West Iraq)

Hydrogeological investigation of groundwater has been performed within Kasra- Nukhaib district (west Iraq). The physicochemical analyses of the groundwater samples collected from Um Erdhuma-Tayarat aquifer are used in determination of hydrogeochemical processes, hydrochemical facies, hydrochemical ratio, and saturation indices supported by phreeqc software. The monitoring network of groundwater quality consists of twelve physiochemical variables in twenty four water wells were determined, aiming to examine the hydrogeo-chemical phenomena which are benefit in groundwater development and support the plans of future uses (exploitation) and groundwater management. A hydrogeological model was prepared to examine qualitative evaluation of aquifers media related to geochemical processes. Spatial hydrochemical bi-models were achieved for quantitative interpretation. Various graphical plots such as Piper, Durov, and Gibbs diagrams are used in proving different geochemical processes. The results are correlated with standards classifications to deduce the hydrogeo-chemical phenomena. The results showed that the groundwater of Um Erdhuma-Tayarat aquifer has a property of Carbonate weathering represents the major hydrogeochemical processes. In addition, ion exchange and reverse ion exchange were two possible processes of water-rock interaction (e.g. dolomitization processes) within the hydrogeologic system. Also, the evaporation process and mixing action of recharge vadose waters, and ancient trapped fossil waters have a moderate effect on the evolution of groundwater quality. An increased salt content is observed in groundwater at different static water levels indicating mixing with various sources. The mechanism controlling groundwater chemistry is originally related to geogenic process. In addition, anthropogenic activities have not significantly altered the geochemical nature of groundwater in the aquifers system.

Development and application of geochemical data processing system based on fractal theory

GC-GIS system is a geochemical data processing system based on fractal theory. The system realized quantity statistics function by calling Surfer and MapInfo software, and it is compiled with Visual Basic language. This system is designed to integrate the functions both quantity statistics of Surfer and spatial data management of MapInfo. A new algorithm of fractal is added up to GC-GIS. Taking example for Weichang region of Hebei to test the system, the processing results show that the model can match the real distribution of mine well.

Plume interaction and mantle heterogeneity:A geochemical perspective

Mantle plumes originating from the Core-Mantle Boundary(CMB)or the Mantle Transition Zone(MTZ)play an important role in material transfer through Earth’s interior.The hotspot-related plumes originate through different mechanisms and have diverse processes of material transfer.Both the Morganian plumes and large low shear wave velocity provinces(LLSVPs)are derived from the D"layer in the CMB,whereas the Andersonian plumes originate from the upper mantle.All plumes have a plume head at the Moho,although the LLSVPs have an additional plume head at the MTZ.We compare the geochemical characteristics of various plumes in an attempt to evaluate the material exchange between the plumes and mantle layers.The D"layer,the LLSVPs and the Morganian plumes are consisted of subducted slab and post-perovskite from the lower mantle.Bridgmanite would crystallize during the upwelling process of the LLSVPs and the Morganian plumes in the lower mantle,and the residual is a basalt-trachyte suite.Unlike the Morganian plumes,the crystallization in the LLSVPs is insufficient that material accumulates beneath the MTZ to form a plume head.Typically,the secondary plumes above the plume head occur at the edge of the LLSVPs because it is easier for bridgmanite crystal separating from the plume head at the edge,and the residual material with low density upwells to form the secondary plumes.Meanwhile,Na and K are enriched during the long-term crystallization process,and then the basalt-phonolite suite appears in the LLSVPs.The geochemical characteristics of Andersonian plumes suggest that the basalt-rhyolite suite is the major component in the upper mantle.Meanwhile the basalt-rhyolite suite also appears in the LLSVPs and the Morganian plumes because of the assimilation and contamination in the plume head beneath the Mono.

Assessment of the Greenhouse Gas Footprint and Environmental Impact of CO_(2)and O_(2)in situ Uranium Leaching

Under the new development philosophy of carbon peaking and carbon neutrality,CO_(2)and O_(2)in situ leaching(ISL)has been identified as a promising technique for uranium mining in China,not only because it solves carbon dioxide utilization and sequestration,but it also alleviates the environmental burden.However,significant challenges exist in assessment of CO_(2)footprint and water-rock interactions,due to complex geochemical processes.Herein this study conducts a three-dimensional,multicomponent reactive transport model(RTM)of a field-scale CO_(2)and O_(2)ISL process at a typical sandstone-hosted uranium deposit in Songliao Basin,China.Numerical simulations are performed to provide new insight into quantitative interpretation of the greenhouse gas(CO_(2))footprint and environmental impact(SO_(4)^(2–))of the CO_(2)and O_(2)ISL,considering the potential chemical reaction network for uranium recovery at the field scale.RTM results demonstrate that the fate of the CO_(2)could be summarized as injected CO_(2)dissolution,dissolved CO_(2)mineralization and storage of CO_(2)as a gas phase during the CO_(2)and O_(2)ISL process.Furthermore,compared to acid ISL,CO_(2)and O_(2)ISL has a potentially smaller environmental footprint,with 20%of SO_(4)^(2–)concentration in the aquifer.The findings improve our fundamental understanding of carbon utilization in a long-term CO_(2)and O_(2)ISL system and provide important environmental implications when considering complex geochemical processes.

Water Analysis for Heavy Metals Content in Selected Boreholes in Port Harcourt Metropolis （A Case Study during 2010-2011）

Underground water （Borehole） has been the main alternative source of drinking water for most communities in my country. Previous studies have revealed high levels of contamination. The origin of which can be attributed to geochemical processes, combustion of fossil fuels, mining and anthropogenic activities. Most borehole water and well water in local communities of Nigeria are not safe for drinking due to heavy industrial and environmental pollution. This study was undertaken to assess the quality in some selected boreholes in the Port Harcourt metropolis for a period of two years. Borehole water samples were randomly collected from thirteen boreholes in a local community in plastic bottles （100 mL） in the months of September for the years of study （2010 ＆ 2011）. Four out of the seven heavy metals analyzed were found to be present in the first year of study. These were Fe, Cu, Mn and Zn. In the second year of study, Pb, Cr, Fe and Co were not detected in all of the samples except Cu and Fe which were present in only two samples. Mn and Zn were found to be present in all of the samples for both years of study.

Fractionation characteristics of rare earth elements(REEs) linked with secondary Fe, Mn, and Al minerals in soils

Soil secondary minerals are important scavengers of rare earth elements(REEs) in soils and thus affect geochemical behavior and occurrence of REEs. The fractionation of REEs is a common geochemical phenomenon in soils but has received little attention, especially fractionation induced by secondary minerals. In this study, REEs(La to Lu and Y) associated with soil-abundant secondary minerals Fe-, Al-, and Mn-oxides in 196 soil samples were investigated to explore the fractionation and anomalies of REEs related to the minerals. The results show right-inclined chondrite-normalized REE patterns for La–Lu in soils subjected to total soil digestion and partial soil extraction. Light REEs(LREEs) enrichment features were negatively correlated with a Eu anomaly and positively correlated with a Ce anomaly. The fractionation between LREEs and heavy REEs(HREEs) was attributed to the high adsorption affinity of LREEs to secondary minerals and the preferred activation/leaching of HREEs.The substantial fractions of REEs in soils extracted byoxalate and Dithionite-Citrate-Bicarbonate buffer solutions were labile(10 %–30 %), which were similar to the mass fraction of Fe(10 %–20 %). Furthermore, Eu was found to be more mobile than the other REEs in the soils, whereas Ce was less mobile. These results add to our understanding of the distribution and geochemical behavior of REEs in soils, and also help to deduce the conditions of soil formation from REE fractionation.