干旱区生态环境知识资源中心(Arid): Using Carbon-14 of dissolved organic carbon to determine groundwater ages and travel times in aquifers with low organic carbon

Arid

DOI	10.1016/j.apgeochem.2020.104842
	Using Carbon-14 of dissolved organic carbon to determine groundwater ages and travel times in aquifers with low organic carbon
	Thomas, James M.; Hershey, Ronald L.; Fereday, Wyatt; Burr, George
通讯作者	Thomas, JM (corresponding author), Desert Res Inst, Reno, NV 89506 USA.
来源期刊	APPLIED GEOCHEMISTRY
ISSN	0883-2927
EISSN	1872-9134
出版年	2021
卷号	124
英文摘要	This study used dissolved organic carbon (DOC) carbon-14 (C-14) to determine groundwater ages that were then used to calculate groundwater travel times in southern Nevada aquifers that have low organic content. These travel times are compared with the more standard dissolved inorganic (DIC) C-14 method for determining groundwater ages and travel times. Groundwater travel times for aquifers in southern Nevada using DOC C-14 are thousands of years shorter than DIC C-14 travel times for groundwater flow outside of recharge areas along four of the five flow paths evaluated for this study. The DOC C-14 travel times range from 2,300 to 2,900 years (yrs) as compared to DIC C-14 travel times that range from 8,200 to 22,000 yrs (uncorrected ages) and 4,700 to 19,000 yrs (corrected ages). The DOC C-14 groundwater travel times in carbonate-rock and volcanic-rock aquifers of southern Nevada are similar to travel times determined from: (1) hydrogeologic data; (2) observations of rapid high-level tritium transport at the Nevada National Security Site; and (3) 550,000-yr delta O-18 and delta C-13 global climate records for calcite precipitated in Devils Hole, Nevada at the end of one of the flow paths. DOC C-14 travel time calculations need to account for fewer processes than DIC C-14 for aquifers that contain little organic matter and do not have redox reactions. DOC C-14 travel-times can be calculated directly from the DOC C-14 data in these aquifers without corrections if dissolution of organic carbon and sorption and matrix diffusion of DOC C-14 onto or into the aquifer matrix is minimal. Laboratory experiments showed that little organic carbon was being leached from aquifer rocks, sorption of organic carbon ranged from 4.3% sorbed in carbonate rocks to 0.5% sorbed in volcanic rocks, and matrix diffusion coefficients were slower in lower porosity carbonate rocks (1.7 x 10(-7) cm(2)/s) than in higher porosity volcanic rocks (2.9 x 10(-7) cm(2)/s). The lack of dissolution of organic carbon in study area aquifers is also supported by the decrease in DOC along flow paths and the DOC composition of groundwater changing little as groundwater flows from recharge areas into the adjacent valleys. In contrast, DIC C-14 groundwater travel-time calculations must be corrected for complex chemical reactions and physical processes, including mineral/gas dissolution, mineral/gas precipitation/exsolution, cation exchange, and carbon isotopic exchange that can significantly change the amount of DIC C-14 in groundwater along flow paths by processes other than radioactive decay. DIC C-14 can also be affected by sorption and matrix diffusion, but these processes may, or may not, be captured in geochemical modeling of precipitation/dissolution and carbon isotopic exchange reactions. Corrected DIC C-14 ages, therefore, represent maximum ages.
英文关键词	Carbon-14 Dissolved organic carbon Groundwater age Groundwater travel time Geochemical modeling Arid environments Southern Nevada
类型	Article
语种	英语
收录类别	SCI-E
WOS记录号	WOS:000612398700003
WOS关键词	DEVILS-HOLE ; ISOTOPIC COMPOSITION ; RADIOCARBON ; RECORD ; EVOLUTION ; THRUST ; BASIN ; WATER ; BELT
WOS类目	Geochemistry & Geophysics
WOS研究方向	Geochemistry & Geophysics
来源机构	Desert Research Institute
资源类型	期刊论文
条目标识符	http://119.78.100.177/qdio/handle/2XILL650/369080
作者单位	[Thomas, James M.; Hershey, Ronald L.] Desert Res Inst, Reno, NV 89506 USA; [Fereday, Wyatt] State Nevada, Carson City, NV USA; [Burr, George] Natl Taiwan Univ, Taipei, Taiwan
推荐引用方式 GB/T 7714	Thomas, James M.,Hershey, Ronald L.,Fereday, Wyatt,et al. Using Carbon-14 of dissolved organic carbon to determine groundwater ages and travel times in aquifers with low organic carbon[J]. Desert Research Institute,2021,124.
APA	Thomas, James M.,Hershey, Ronald L.,Fereday, Wyatt,&Burr, George.(2021).Using Carbon-14 of dissolved organic carbon to determine groundwater ages and travel times in aquifers with low organic carbon.APPLIED GEOCHEMISTRY,124.
MLA	Thomas, James M.,et al."Using Carbon-14 of dissolved organic carbon to determine groundwater ages and travel times in aquifers with low organic carbon".APPLIED GEOCHEMISTRY 124(2021).