铬稳定同位素地球化学

doi:10.13745/j.esf.sf.2020.3.5

摘要/Abstract

摘要：

随着多接收质谱仪分析技术的进步,铬稳定同位素体系在最近二十几年的环境科学和地球化学中得到了越来越广泛的应用。铬元素属于氧化还原敏感元素,在氧化还原反应过程中伴随着较大的同位素分馏。因此,铬同位素在指示现代或古代环境的氧化还原状态方面有着重要的应用。同时,铬也是中度相容和轻度亲铁元素,使得铬稳定同位素体系也可用来制约高温地质过程(如核幔分异、地幔熔融和岩浆分异结晶等)以及地外行星的演化。本综述首先介绍铬稳定同位素体系,随后讲述分析方法、铬同位素分馏原理以及铬同位素在高温、低温地球化学中的应用。

关键词: 铬同位素, 氧化还原指标, 古环境, 地外行星演化

Abstract:

With the advancement of multicollector mass spectrometry, the stable chromium isotopic system has been widely applied to solving environmental and geochemical problems. Chromium is a redox-sensitive element, and transformations between different oxidation states are accompanied by large isotopic fractionations. Therefore, chromium isotopes play important roles in investigating the redox conditions of modern and paleo-environments. Moreover, chromium is a moderately compatible and slightly siderophile element, and large isotope fractionation exists between different minerals. Thus, chromium isotopes can also be potentially applied to study mantle partial melting, magma differential crystallization, and planetary evolution. In this review, we covered the following topics: (1) an overview of chromium stable isotopic systematics; (2) analytical methods; (3) isotopic fractionation mechanisms; and (4) applications of stable chromium isotopes in high- and low-temperature geochemistry.

Key words: chromium isotope, redox proxy, paleo-environment, planetary evolution

中图分类号:

P597.2

王相力, 卫炜. 铬稳定同位素地球化学[J]. 地学前缘, 2020, 27(3): 78-103.

WANG Xiangli, WEI Wei. Stable chromium isotope geochemistry[J]. Earth Science Frontiers, 2020, 27(3): 78-103.

图/表 12

图1 溶液相中Cr(Ⅲ)和Cr(Ⅵ)的Eh-pH相图

Fig.1 Eh-pH diagram for different Cr (Ⅲ) and Cr (Ⅵ) species in aquatic system

表1 铬同位素及干扰元素的同位素丰度

Table 1 Abundances of stable Cr isotopes and their isobaric interferences

元素	具不同质量数的铬与干扰元素同位素及其丰度
元素	49	50	51	52	53	54	55	56
Ti	⁴⁹Ti 5.41%	⁵⁰Ti 5.18%
V		⁵⁰V 0.25%	⁵¹V 99.75%
Cr		⁵⁰Cr 4.35%		⁵²Cr 83.79%	⁵³Cr 9.50%	⁵⁴Cr 2.36%
Fe						⁵⁴Fe 5.85%		⁵⁶Fe 91.75%

表2 非生物作用Cr(Ⅵ)还原过程中的铬同位素分馏

Table 2 Summary of Cr isotope fractionations during abiotic Cr (Ⅵ) reduction

参考文献	初始浓度	实验简介	分馏类型	分馏ε/‰
Ellis等^[24]	0.19 mmol/L	磁铁矿	瑞利分馏	-3.4
		入海口沉积物
		池塘沉积物
Zink等^[39]	8.65 mmol/L	0.9 μmol H₂O₂,pH≈0.7	瑞利分馏	-4.2
		13.2 μmol H₂O₂,pH≪1	平衡分馏	-3.5
		13.2 μmol H₂O₂,中性	瑞利分馏	-5.0
Berna等^[36]	1.92 mmol/L	绿色沉积物	瑞利分馏	-3.1
Berna等^[36]	1.92 mmol/L	绿色沉积物	瑞利分馏	-2.4
Døssing等^[34]	0.41 mmol/L	1.15 mmol/L Fe(Ⅱ),pH=7(批次实验)	瑞利分馏	-3.1
Døssing等^[34]	3.85 mmol/L	0.03 mmol/(L·min) Fe(Ⅱ),pH=6.8和8.1(添加实验)	瑞利分馏	-1.5
参考文献	初始浓度	实验简介	分馏类型	分馏ε/‰
Basu和Johnson^[37]	19 μmol/L	针铁矿[345 μmol/L Fe(Ⅱ)]	瑞利分馏	-3.9
	18 μmol/L	FeS [75 μmol/L Fe(Ⅱ)]		-2.1
	11.15 μmol/L	铜绿 [100 μmol/L Fe(Ⅱ)]		-2.7
	18.98 μmol/L	菱铁矿 [84.2 μmol/L Fe(Ⅱ)]		-2.7
	23 μmol/L	ISRM沉积物 [2 400 μmol/L Fe(Ⅱ)]		-3.2
Jamieson-Hanes等^[40]	0.38 mmol/L	7.5 g有机碳(批次实验)	瑞利分馏	-3.5
Jamieson-Hanes等^[40]	0.38 mmol/L	有机碳(流通实验)	平衡分馏	-2.1
Kitchen等^[35]	20~22 μmol/L	5~25 μmol/L溶解Fe(Ⅱ),pH=4.5~5.3	瑞利分馏	-4.2
	20.5 μmol/L	1.9 mmol/L Ellliot富里酸,pH=5.0	瑞利分馏	-3.1
		1.9 mmol/L Waskish腐殖酸,pH=4.5和5.0
		针铁矿和γ-Al₂O₃催化下,200 μmol/L 扁桃酸,pH=4.0
Jamieson-Hanes等^[41]	1.0 mmol/L	厌氧环境下,颗粒状零价Fe(流通实验)	两阶段	早期:-0.2
Jamieson-Hanes等^[41]	1.0 mmol/L	厌氧环境下,颗粒状零价Fe(流通实验)	两阶段	晚期:-1.5

表3 生物作用Cr(Ⅵ)还原过程中的铬同位素分馏

Table 3 Summary of Cr isotope fractionations during biotic Cr (Ⅵ) reduction

参考文献	初始浓度	实验简介	分馏类型	分馏ε/‰
Sikora等^[42]	5.1~9.5 μmol/L	3.3~100 μmol/L乳酸盐(Shewanella oneidensis stain MR-1)	瑞利分馏	-4.5~-4.1
	5.1~9.5 μmol/L	6.8~60 μmol/L 甲酸盐(Shewanella oneidensis stain MR-1)		-4.5~-4.0
	9.5 μmol/L	10.2 mmol/L乳酸盐(Shewanella oneidensis stain MR-1)		-1.8
Han等^[44]	50 μmol/L	需氧环境下,20 μmol/L乳酸盐(Pseudomonas stutzeri stain RCH2)	瑞利分馏	-2.0
Han等^[44]	50 μmol/L	反硝化环境下,20 μmol/L乳酸盐(Pseudomonas stutzeri stain RCH2)	瑞利分馏	-0.4
Basu等^[45]	5 μmol/L	300 μmol/L醋酸盐(Geobacter sulfurreducens)	瑞利分馏	-3.03
		300 μmol/L乳酸盐(Shewanella sp. strain NR)		-2.17
		300 μmol/L醋酸盐(Pseudomonas stutzeri DCP-Ps1)		-3.14
	10 μmol/L	100 μmol/L丙酮酸盐(Desulfovibrio vulgaris)		-3.01
Xu等^[46]	19.2 mmol/L	无葡萄糖(Bacillus sp. QH-1),37 ℃	瑞利分馏	-3.74
		0.1 mmol/L葡萄糖(Bacillus sp. QH-1),37 ℃		-1.94
		1 mmol/L葡萄糖(Bacillus sp. QH-1),37 ℃		-2.02
		2.5 mmol/L葡萄糖(Bacillus sp. QH-1),37 ℃		-1.99
		10 mmol/L葡萄糖(Bacillus sp. QH-1),37 ℃		-1.92
		2.5 mmol/L葡萄糖(Bacillus sp. QH-1),4 ℃		-7.62
		2.5 mmol/L葡萄糖(Bacillus sp. QH-1),15 ℃		-4.59
		2.5 mmol/L葡萄糖(Bacillus sp. QH-1),25 ℃		-3.09
Lu等^[47]	0.2 mmol/L	细菌作用下沉积物产生的CH₄	瑞利分馏	-2.62
Zhang等^[48]	0.4 nmol/L	需氧环境下,葡萄糖(Pseudomonas)	瑞利分馏	-3.12
		需氧环境下,柠檬酸盐(Pseudomonas)		-4.32
		需氧环境下,醋酸盐(Pseudomonas)		-3.21
		需氧环境下,丙酸盐(Pseudomonas)		-3.90
		厌氧环境下,葡萄糖(Pseudomonas)		-4.93
		厌氧环境下,柠檬酸盐(Pseudomonas)		-4.63
		厌氧环境下,醋酸盐(Pseudomonas)		-3.37
		厌氧环境下,丙酸盐(Pseudomonas)		-1.58
		需氧环境下,琥珀酸盐(Shewanella)		-3.43
		厌氧环境下,琥珀酸盐(Shewanella)		-2.47
		需氧环境下,不同浓度的葡萄糖(Pseudomonas)		-3.19
		需氧环境下,Pseudomonas,pH=4		-3.08
		需氧环境下,Pseudomonas,pH=6		-3.14
		需氧环境下,Pseudomonas,pH=8		-3.13
Chen等^[43]	100 μmol/L	Shewanella oneidensis stain MR-1, pH=6.0~8.5, T=18~34 ℃	早期	-2.37~-3.04
Chen等^[43]	100 μmol/L	Shewanella oneidensis stain MR-1, pH=6.0~8.5, T=18~34 ℃	晚期	-0.98~-1.11
Zhang等^[49]	0.4 nmol/L	Pseudomonas fluorescens LB 300,无Fe	瑞利分馏	-2.56
		Pseudomonas fluorescens LB 300,溶解态Fe(Ⅲ)		-3.00
		Pseudomonas fluorescens LB 300,针铁矿		-2.96
		Pseudomonas fluorescens LB 300,赤铁矿		-4.26
		Pseudomonas fluorescens LB 300,溶解态Fe(Ⅱ)		-3.39
		Pseudomonas fluorescens LB 300,针铁矿和Fe(Ⅱ)		-3.24
		Pseudomonas fluorescens LB 300,赤铁矿和Fe(Ⅱ)		-3.29
		Shewanella oneidensis MR-1,无Fe		-2.47
		Shewanella oneidensis MR-1,溶解态Fe(Ⅲ)		-2.34
		Shewanella oneidensis MR-1,针铁矿		-2.13
		Shewanella oneidensis MR-1,赤铁矿		-2.27

表3 生物作用Cr(Ⅵ)还原过程中的铬同位素分馏

Table 3 Summary of Cr isotope fractionations during biotic Cr (Ⅵ) reduction

参考文献	初始浓度	实验简介	分馏类型	分馏ε/‰
Sikora等^[42]	5.1~9.5 μmol/L	3.3~100 μmol/L乳酸盐(Shewanella oneidensis stain MR-1)	瑞利分馏	-4.5~-4.1
	5.1~9.5 μmol/L	6.8~60 μmol/L 甲酸盐(Shewanella oneidensis stain MR-1)		-4.5~-4.0
	9.5 μmol/L	10.2 mmol/L乳酸盐(Shewanella oneidensis stain MR-1)		-1.8
Han等^[44]	50 μmol/L	需氧环境下,20 μmol/L乳酸盐(Pseudomonas stutzeri stain RCH2)	瑞利分馏	-2.0
Han等^[44]	50 μmol/L	反硝化环境下,20 μmol/L乳酸盐(Pseudomonas stutzeri stain RCH2)	瑞利分馏	-0.4
Basu等^[45]	5 μmol/L	300 μmol/L醋酸盐(Geobacter sulfurreducens)	瑞利分馏	-3.03
		300 μmol/L乳酸盐(Shewanella sp. strain NR)		-2.17
		300 μmol/L醋酸盐(Pseudomonas stutzeri DCP-Ps1)		-3.14
	10 μmol/L	100 μmol/L丙酮酸盐(Desulfovibrio vulgaris)		-3.01
Xu等^[46]	19.2 mmol/L	无葡萄糖(Bacillus sp. QH-1),37 ℃	瑞利分馏	-3.74
		0.1 mmol/L葡萄糖(Bacillus sp. QH-1),37 ℃		-1.94
		1 mmol/L葡萄糖(Bacillus sp. QH-1),37 ℃		-2.02
		2.5 mmol/L葡萄糖(Bacillus sp. QH-1),37 ℃		-1.99
		10 mmol/L葡萄糖(Bacillus sp. QH-1),37 ℃		-1.92
		2.5 mmol/L葡萄糖(Bacillus sp. QH-1),4 ℃		-7.62
		2.5 mmol/L葡萄糖(Bacillus sp. QH-1),15 ℃		-4.59
		2.5 mmol/L葡萄糖(Bacillus sp. QH-1),25 ℃		-3.09
Lu等^[47]	0.2 mmol/L	细菌作用下沉积物产生的CH₄	瑞利分馏	-2.62
Zhang等^[48]	0.4 nmol/L	需氧环境下,葡萄糖(Pseudomonas)	瑞利分馏	-3.12
		需氧环境下,柠檬酸盐(Pseudomonas)		-4.32
		需氧环境下,醋酸盐(Pseudomonas)		-3.21
		需氧环境下,丙酸盐(Pseudomonas)		-3.90
		厌氧环境下,葡萄糖(Pseudomonas)		-4.93
		厌氧环境下,柠檬酸盐(Pseudomonas)		-4.63
		厌氧环境下,醋酸盐(Pseudomonas)		-3.37
		厌氧环境下,丙酸盐(Pseudomonas)		-1.58
		需氧环境下,琥珀酸盐(Shewanella)		-3.43
		厌氧环境下,琥珀酸盐(Shewanella)		-2.47
		需氧环境下,不同浓度的葡萄糖(Pseudomonas)		-3.19
		需氧环境下,Pseudomonas,pH=4		-3.08
		需氧环境下,Pseudomonas,pH=6		-3.14
		需氧环境下,Pseudomonas,pH=8		-3.13
Chen等^[43]	100 μmol/L	Shewanella oneidensis stain MR-1, pH=6.0~8.5, T=18~34 ℃	早期	-2.37~-3.04
Chen等^[43]	100 μmol/L	Shewanella oneidensis stain MR-1, pH=6.0~8.5, T=18~34 ℃	晚期	-0.98~-1.11
Zhang等^[49]	0.4 nmol/L	Pseudomonas fluorescens LB 300,无Fe	瑞利分馏	-2.56
		Pseudomonas fluorescens LB 300,溶解态Fe(Ⅲ)		-3.00
		Pseudomonas fluorescens LB 300,针铁矿		-2.96
		Pseudomonas fluorescens LB 300,赤铁矿		-4.26
		Pseudomonas fluorescens LB 300,溶解态Fe(Ⅱ)		-3.39
		Pseudomonas fluorescens LB 300,针铁矿和Fe(Ⅱ)		-3.24
		Pseudomonas fluorescens LB 300,赤铁矿和Fe(Ⅱ)		-3.29
		Shewanella oneidensis MR-1,无Fe		-2.47
		Shewanella oneidensis MR-1,溶解态Fe(Ⅲ)		-2.34
		Shewanella oneidensis MR-1,针铁矿		-2.13
		Shewanella oneidensis MR-1,赤铁矿		-2.27

表4 Cr(Ⅲ)氧化过程中的铬同位素分馏

Table 4 Summary of Cr isotope fractionations during Cr (Ⅲ) oxidation

参考文献	实验简介	δ⁵³Cr/‰	ε
Bain和Bullen^[51]	水钠锰矿 (δ-MnO₂)	-2.5~0.7
Ellis等^[52]	软锰矿 (β-MnO₂)	1.1
Wang等^[53]	水钠锰矿 (δ-MnO₂),pH≈4.5		-0.5~0.0
Zink等^[39]	0.5~150 μmol H₂O₂, pH=10.5		0.2

表5 Cr(Ⅲ)与Cr(Ⅵ)之间的同位素平衡分馏

Table 5 Summary of equilibrium Cr isotope fractionation between Cr (Ⅲ) and Cr (Ⅵ)

参考文献	实验简介	Δ/‰
Schauble等^[57]	理论计算	6.0~7.0
Zink等^[39]	溶解Cr(Ⅲ)和Cr(Ⅵ)同位素交换(总浓度为50 μg/mL,浓度比分别为1/2和2/1),pH=5.5或7,反应时间超过数周
Wang等^[58]	0.2 mol/L Cr(Ⅲ)和0.2 mol/L Cr(Ⅵ)同位素交换,pH=1.2, 60 ℃	5.2
	0.2 mol/L Cr(Ⅲ)和0.2 mol/L Cr(Ⅵ)同位素交换,pH=1.2, 40 ℃	5.5
	0.2 mol/L Cr(Ⅲ)和0.2 mol/L Cr(Ⅵ)同位素交换,pH=1.2, 25 ℃	5.8

表6 非氧化还原反应的铬同位素分馏

Table 6 Summary of the redox-independent Cr isotope fractionations

参考文献	实验简介	分馏Δ/‰
Ellis等^[59]	γ-Al₂O₃吸附溶解的Cr(Ⅵ),pH=4(6~12 h)	-0.04
	γ-Al₂O₃吸附溶解的Cr(Ⅵ),pH=6(6~12 h)	0.00
	α-goethite吸附溶解的Cr(Ⅵ),pH=4(6~12 h)	0.02
	α-goethite吸附溶解的Cr(Ⅵ),pH=6(24 h)	-0.04
Rodler等^[61]	8、30和 70 μg/mL溶解态Cr(Ⅵ)与方解石快速共沉淀	0.06~0.18
Rodler等^[61]	520、1 560、3 120、5 200和10 400 μg/mL溶解态Cr(Ⅵ)与方解石缓慢共沉淀	0.29±0.08
Saad等^[62]	固态Cr(Ⅲ)溶解于各类铁载体、有机酸以及两者的混合物	-0.19~1.23
Babechuk等^[63]	CrC $l 2 +$ -CrCl²⁺	Cr³⁺-CrCl²⁺
	200 μg Cr(Ⅲ)溶解于6 mol/L HCl(161 d)	0.02	-0.73
	200 μg Cr(Ⅲ)溶解于0.1 mol/L和1 mol/L HCl(38 d)	1.04、1.81	-1.88、-1.59
	200 μg Cr(Ⅲ)溶解于0.01 mol/L HCl(38 d)	-0.19	-0.49
	102.5 mg CrCl₃·6H₂O溶解于10.5 mL的0.01 mol/L HCl	-0.38	-0.51
Kraemer等^[64]	DFOB和柠檬酸淋滤硅酸盐岩	-0.13~0.53
Kraemer等^[64]	DFOB和柠檬酸淋滤氧化物岩石	-0.13~2.19
Frank等^[60]	高岭土吸附河水中的Cr(Ⅵ)(0.1~10 mg/L)	-0.24
Frank等^[60]	高岭土吸附海水中Cr(Ⅵ)(0.1~10 mg/L)	无吸附

表6 非氧化还原反应的铬同位素分馏

Table 6 Summary of the redox-independent Cr isotope fractionations

参考文献	实验简介	分馏Δ/‰
Ellis等^[59]	γ-Al₂O₃吸附溶解的Cr(Ⅵ),pH=4(6~12 h)	-0.04
	γ-Al₂O₃吸附溶解的Cr(Ⅵ),pH=6(6~12 h)	0.00
	α-goethite吸附溶解的Cr(Ⅵ),pH=4(6~12 h)	0.02
	α-goethite吸附溶解的Cr(Ⅵ),pH=6(24 h)	-0.04
Rodler等^[61]	8、30和 70 μg/mL溶解态Cr(Ⅵ)与方解石快速共沉淀	0.06~0.18
Rodler等^[61]	520、1 560、3 120、5 200和10 400 μg/mL溶解态Cr(Ⅵ)与方解石缓慢共沉淀	0.29±0.08
Saad等^[62]	固态Cr(Ⅲ)溶解于各类铁载体、有机酸以及两者的混合物	-0.19~1.23
Babechuk等^[63]	CrC $l 2 +$ -CrCl²⁺	Cr³⁺-CrCl²⁺
	200 μg Cr(Ⅲ)溶解于6 mol/L HCl(161 d)	0.02	-0.73
	200 μg Cr(Ⅲ)溶解于0.1 mol/L和1 mol/L HCl(38 d)	1.04、1.81	-1.88、-1.59
	200 μg Cr(Ⅲ)溶解于0.01 mol/L HCl(38 d)	-0.19	-0.49
	102.5 mg CrCl₃·6H₂O溶解于10.5 mL的0.01 mol/L HCl	-0.38	-0.51
Kraemer等^[64]	DFOB和柠檬酸淋滤硅酸盐岩	-0.13~0.53
Kraemer等^[64]	DFOB和柠檬酸淋滤氧化物岩石	-0.13~2.19
Frank等^[60]	高岭土吸附河水中的Cr(Ⅵ)(0.1~10 mg/L)	-0.24
Frank等^[60]	高岭土吸附海水中Cr(Ⅵ)(0.1~10 mg/L)	无吸附

图2 现代风化剖面[112,113,114,115,116,117,118]、河水[112,114-116]、入海口[119]、海水[22-23,30,114,121-122,124-125,128,130,132,147]和各类型大洋沉积物[19,23,120,125-133]δ53Cr数据统计

Fig.2 A compilation of δ53Cr values of modern weathering profiles[112,113,114,115,116,117,118], river waters[112,114-116], estuarine waters[119], seawater[22-23,30,114,121-122,124-125,128,130,132,147],and various marine sediments[19,23,120,125-133]

图3 目前已报道的海水ln[Cr]与δ53Cr值相关性图解[22-23,30,114,121-122,124-125,128,130,132,147]

Fig.3 Cross-plot of seawater ln[Cr] versus δ53Cr data published so far[22-23,30,114,121-122,124-125,128,130,132,147]

图4 现代全球铬同位素质量平衡模型

Fig.4 A schematic illustration of the modern global Cr isotope mass balance model

图5 在瑞利分馏模型中,地下水Cr(Ⅵ)的还原程度与δ53Cr值的关系

Fig.5 Extent of Cr (Ⅵ) reduction in groundwater versus the δ53Cr values in a Rayleigh fractionation model during Cr (Ⅵ) reduction

图6 (A)地质历史上大气氧含量演化;(B)目前已报道的古土壤[83,84,85,86,87]和沉积岩[10,23,61,84,88-111]δ53Cr数据统计

Fig.6 (A) The evolution of atmospheric oxygen content through Earth history.(B) A compilation of δ53Cr in paleosols[83,84,85,86,87] and sedimentary rocks[10,23,61,84,88-111].

参考文献 223

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