Arsenic enrichment in unconfined sections of the southern Gulf Coast aquifer system, Texas
Authors：J.B. Gates a,b,*, J.P. Nicot a, B.R. Scanlon a, R.C. Reedy a
Department: a Bureau of Economic Geology, Jackson School of Geosciences, University of Texas at Austin, University Station, Box XAustin, Texas 78713-8924, United States
b Department of Earth at Atmospheric Sciences, University of Nebraska-Lincoln, 214 Bessey Hall, P.O. Box 880340, Lincoln, NE 68588-0340, United States
Journal：Applied Geochemistry
Volumes：26
Issue：4
Date：April 2011
Page number：421-431
Abstract：Groundwater arsenic concentrations exceeding the federal drinking water standard are common in the southern Gulf Coast aquifer system in Texas, including in aerobic, unconfined groundwater which provides much of the municipal and domestic water supplies for the region. The objective of this study was to determine geochemical factors affecting the occurrence and distribution of groundwater As in unconfined portions of the southern Gulf Coast aquifer system through a comparative transect study of groundwater across three major hydrostratigraphic units (the Catahoula Formation, Jasper aquifer and Evangeline aquifer) and analysis of regional water quality data. Results show that As concentrations decrease with increasing distance from the Catahoula Formation, which is consistent with Miocene volcanic ash as the main source of As to groundwater in the region. Arsenic concentrations correlate with V, SiO2 and K, all of which were released during weathering of volcanic sediments and their degradation products. In all three units, carbonate weathering and active recharge in the unconfined zones result in circum-neutral pH and oxidizing groundwater, which are typically amenable to As immobilization by adsorption of arsenate onto mineral oxides and clays. However, As concentrations exceed 10 µg/L in approximately 30% of wells. Silica that was co-released with As may compete for sorption sites and reduce the capacity for arsenate adsorption.

《应用地球化学》刊登“墨西哥湾南部德克萨斯州浅层含水层砷的富集”
作者: J.B. Gates, J.P. Nicot, B.R. Scanlon, R.C. Reedy
刊物：应用地球化学
时间：2011年4月
卷号：26
期号：4
页码：421-431
摘要：
墨西哥湾南部德克萨斯州地下水中砷的浓度超过联邦饮用水标准是常见的，其中包括许多为市政、生活用水提供水源的有氧、浅层地下水。本研究的目的是通过对比性研究三大含水岩层系统的横断面（卡塔胡拉形成，碧玉含水层和伊万杰琳含水层）和区域水质数据分析，确定影响砷在墨西哥湾沿岸南部地区浅层含水层系统中发生与分布的地球化学因素。结果表明：随着距离卡塔胡拉形成距离的增加，砷浓度不断降低。这与在该地区第三纪中新世火山灰作为地下水中砷的主要来源相符合。砷的浓度与钒、二氧化硅和钾的含量相关，这些都是火山岩沉积物在风化、降解过程中所释放的产物。三个系统的横断面中，碳酸盐不断风化、浅水区充分补给导致地下水不断被氧化并且pH值在中性周围波动，条件非常适合吸附砷的矿物氧化物和粘土对砷的固定。然而，井水中砷的浓度超过10 µg/L的比率大约为30%。可能是因为与砷一起释放的硅土与砷发生竞争吸附，降低了砷的吸附能力。
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