干旱区生态环境知识资源中心(Arid): Volcanic glass leaching and the groundwater geochemistry on the semi-arid Atlantic island of Porto Santo

Arid

DOI	10.1016/j.apgeochem.2019.104470
	Volcanic glass leaching and the groundwater geochemistry on the semi-arid Atlantic island of Porto Santo
	Condesso de Melo, Maria Teresa 1; Shandilya, Raghwendra Narayan 1,5; Pereira Silva, Joao Baptista 2,3; Postma, Dieke 4
通讯作者	Postma, Dieke
来源期刊	APPLIED GEOCHEMISTRY
ISSN	0883-2927
出版年	2020
卷号	114
英文摘要	The groundwater chemistry of the semi-arid volcanic island of Porto Santo, part of the Madeira archipelago, Atlantic Ocean, was investigated. Generally, the groundwater was brackish, containing 2-10 mol % seawater. Groundwater with up to 20 mM alkalinity and a Na enrichment of up to 30 mM, as compared to the Na concentration predicted by the seawater Na/Cl ratio, was found in the main aquifer. Also notable are the high concentrations of F (up to 0.3 mM), B (up to 0.55 mM), As (up to 0.35 mu M), all in excess of WHO recommendations, as well as up to 6 mu M V. Geochemical modeling, using the PHREEQC code, was used to explore different scenarios that could explain the genesis of the observed bulk groundwater chemistry. First, a model for aquifer freshening with the displacement of resident seawater from the aquifer by infiltrating freshwater, was tested. This scenario leads to the development of NaHCO3 waters as observed in many coastal aquifers. However, the measured alkalinity concentration in the groundwater was far higher than the concentration predicted by the freshening model. In addition, the behavior of modelled pH and P(CO2)were at variance with their distributions in the field data. The second model explored the possible effect of volcanic glass leaching on the groundwater chemistry. Using insight derived from studies of volcanic glass surface alteration as well as experimental work on water-volcanic glass interactions, a geochemical model was developed in which the exchange of H+ for Na+ on the volcanic glass surface is the main mechanism but the exchange of other cations on the volcanic glass surface is also included. The uptake of H+ by the glass surface causes the dissociation of carbonic acid, generating bicarbonate. This model is consistent with the local geology and the field data. It requires, however, volcanic glass leaching to occur in the unsaturated zone where there is an unlimited supply of CO2. The exchange reaction of H+ for Na+ is confined to the surface layer of volcanic glass as otherwise the process becomes limited by slow solid state diffusion of H+ into the glass and Na+ out of the glass. Therefore, volcanic ash deposits, with their high volcanic glass surface areas and matrix flow, are the aquifers where this type of high NaHCO3 waters can be expected, rather than in basalts, which predominantly feature fracture flow. The trace components F, B, As and V are believed to originate from hyaloclastites, consisting of predominantly (90%) of trachy-rhyolite volcanic glass. Although stratigraphically older than the main calcarenite aquifer, topographically they are often located at higher altitudes, above the phreatic level and located along the main recharge flow path. In addition, the semiarid climate conditions provide a long groundwater residence time for the reactions as well as limited aquifer flushing.
英文关键词	Groundwater Geochemistry Volcanics Glass Weathering Arid Sodium Bicarbonate Fluoride Arsenic Boron Vanadium Model
类型	Article
语种	英语
国家	Portugal ; Denmark ; South Korea
收录类别	SCI-E
WOS记录号	WOS:000518403400018
WOS关键词	IN-SITU MINERALIZATION ; BORON ADSORPTION ; CANARY-ISLANDS ; CLAY-MINERALS ; SURFACE-CHEMISTRY ; DISSOLUTION RATES ; NATURAL GLASSES ; TRACE-ELEMENTS ; GRAN-CANARIA ; CARBFIX SITE
WOS类目	Geochemistry & Geophysics
WOS研究方向	Geochemistry & Geophysics
资源类型	期刊论文
条目标识符	http://119.78.100.177/qdio/handle/2XILL650/314049
作者单位	1.Univ Lisbon, Inst Super Tecn, CERIS, Av Rovisco Pais, P-1049001 Lisbon, Portugal; 2.Madeira Rochas, Ave Arriga 75,Apartamento 506, P-9000060 Funchal, Madeira, Portugal; 3.Univ Aveiro, Geosci Dept, GEOBIOTEC, Campus Santiago, P-3810193 Aveiro, Portugal; 4.GEUS, Dept Geochem, Oster Voldgade 10, DK-1350 Copenhagen, Denmark; 5.Korea Univ Sci & Technol UST, KIST Sch, Seoul, South Korea
推荐引用方式 GB/T 7714	Condesso de Melo, Maria Teresa,Shandilya, Raghwendra Narayan,Pereira Silva, Joao Baptista,et al. Volcanic glass leaching and the groundwater geochemistry on the semi-arid Atlantic island of Porto Santo[J],2020,114.
APA	Condesso de Melo, Maria Teresa,Shandilya, Raghwendra Narayan,Pereira Silva, Joao Baptista,&Postma, Dieke.(2020).Volcanic glass leaching and the groundwater geochemistry on the semi-arid Atlantic island of Porto Santo.APPLIED GEOCHEMISTRY,114.
MLA	Condesso de Melo, Maria Teresa,et al."Volcanic glass leaching and the groundwater geochemistry on the semi-arid Atlantic island of Porto Santo".APPLIED GEOCHEMISTRY 114(2020).