干旱区生态环境知识资源中心(Arid): A geographic expression of the sepiolite-palygorskite continuum in soils of northwest South Africa

Arid

DOI	10.1016/j.geoderma.2020.114615
	A geographic expression of the sepiolite-palygorskite continuum in soils of northwest South Africa
	Francis, Michele Louise; Majodina, Thando Olwethu; Clarke, Catherine E.
通讯作者	Francis, ML
来源期刊	GEODERMA
ISSN	0016-7061
EISSN	1872-6259
出版年	2020
卷号	379
英文摘要	Some coastal soils in Namaqualand have significant amounts of sepiolite. Palygorskite is relatively low in coastal soils but it is abundant at some inland sites up to 600 km from the coast. This distribution is explained by examining relationships of major ionic species in saturated paste extracts. Our study found two categories of geographically and chemically distinct palygorskite-containing soils: 1) high Mg, palygorskite soils 130 km inland with similar Mg levels to coastal sepiolitic soils, and 2) low Mg, palygorskite soils 600 km inland. The geographic progression from high-Mg sepiolite-containing soils at the coast, through high-Mg palygorskite soils to low-Mg palygorskite soils farthest from the coast parallels the chemical variation in the sepiolite-palygorskite continuum from sepiolite, the most magnesic endmember at the coast, to palygorskite the least magnesic end-member farthest inland. MgSO40 and MgCl+ ion complexes do not appear to depress Mg2+ activity to an extent that is able to distinguish sepiolite-containing from palygorskite-containing soils. Calcite in the profile is strongly associated with occurrence of fibrous clay minerals, and dolomite is absent. Compositions of soil saturated paste extracts conform to their respective mineral stability fields, contrasting with previous work in the area. The previous interpretation, therefore, that fibrous minerals may currently be in a state of alteration requires revision. Evaporation of soil pore waters in the marine-influenced region results in increased Mg and Ca and decreased pH, even with precipitation of sepiolite and calcite. These chemical changes with evaporation are important for understanding the evolution of soil solutions and precipitating minerals in arid coastal environments and the chemistry of waterbodies associated with them.
英文关键词	Fibrous clays Arid soil Clay mineralogy Soil solution Ionic species Evaporation
类型	Article
语种	英语
收录类别	SCI-E
WOS记录号	WOS:000580657200011
WOS关键词	THERMODYNAMIC PROPERTIES ; LACUSTRINE DEPOSITS ; CLIMATE VARIABILITY ; WEST-COAST ; NAMAQUALAND ; EVOLUTION ; MINERALS ; CAPE ; HEUWELTJIE ; SOLUBILITY
WOS类目	Soil Science
WOS研究方向	Agriculture
资源类型	期刊论文
条目标识符	http://119.78.100.177/qdio/handle/2XILL650/326987
作者单位	[Francis, Michele Louise; Clarke, Catherine E.] Stellenbosch Univ, Dept Soil Sci, Private Bag X1, ZA-7602 Stellenbosch, South Africa; [Majodina, Thando Olwethu] Stellenbosch Univ, Dept Earth Sci, Stellenbosch, South Africa
推荐引用方式 GB/T 7714	Francis, Michele Louise,Majodina, Thando Olwethu,Clarke, Catherine E.. A geographic expression of the sepiolite-palygorskite continuum in soils of northwest South Africa[J],2020,379.
APA	Francis, Michele Louise,Majodina, Thando Olwethu,&Clarke, Catherine E..(2020).A geographic expression of the sepiolite-palygorskite continuum in soils of northwest South Africa.GEODERMA,379.
MLA	Francis, Michele Louise,et al."A geographic expression of the sepiolite-palygorskite continuum in soils of northwest South Africa".GEODERMA 379(2020).