In Situ Quantitative Raman Detection of Dissolved Carbon Dioxide and Sulfate in Deep‐Sea High‐Temperature Hydrothermal Vent Fluids

Li, Lianfu; Zhang, Xin; Luan, Zhaokun; Du, Zheng; Shen, Xi; Wang, Bing; Cao, Lei; Lian, Chao; Yan, Jun

doi:10.1029/2018gc007445

Cited by 33 publications

(56 citation statements)

References 64 publications

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“…Nowhere in the ocean, apart from the extreme conditions in hydrothermal vents (Li et al, ), do we find that the concentration of the simple nHB H 2 O molecule exceeds 20% of the total water forms. Over 80% exists as versions of the HB forms, dominantly as the (H 2 O) 5 pentamer.…”

Section: Discussionmentioning

confidence: 50%

How Much H₂O Is There in the Ocean? The Structure of Water in Sea Water

2019

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We report on laboratory and field Raman spectroscopy experiments on the structure of water in sea water and describe this as a function of temperature and pressure. The Raman spectrum of water/seawater is dominated by the water stretching mode band with a frequency shift in the range 2,800-3,800 cm À1 . Here the hydrogen bonded (HB) clusters of several water molecules and nonhydrogen bonded (nHB, singlet H 2 O) forms are revealed with an isoskedastic point, similar to the isosbestic point for pH sensitive dyes. This band can be deconvolved into five Gaussian peaks, each with a specific spectroscopic assignment. We find that within the temperature range of 0-40°C the vastly greater mass and volume of ocean water (78-85%) is in the HB forms, dominantly as (H 2 O) 5 . Without hydrogen bonding there would be no ocean, and nowhere in the bulk ocean does the simple H 2 O molecule exceed 20% of the total. The fraction of water molecules in the solvation shell around ions in seawater represents a third type of water, bound to an ion but not hydrogen bonded. Approximately 6% of the water molecules present at 35 salinity are in this form, and their concentration is not affected by temperature or pressure. The HB forms are a continuum of species in rapid exchange. The fraction of nHB is driven solely by temperature. We find no evidence that increased pressure changes the population of the free singlet nHB molecule; pressure drives the dominantly (H 2 O) 5 population toward a lower volume, nested, molecular state. Plain Language SummaryFor over 50 years ocean scientists have represented the important physical properties of sea water as a collection of bulk fluid coefficients that simply provided a statistical fit to the observed compressibility, sound speed, etc.-but with no underlying molecular basis. Sea water is 96.5% water, and for over 50 years chemists describing the molecular physics of pure water have evolved an understanding that water is composed of a temperature-driven balance between the hydrogen bonded and nonhydrogen bonded forms, but this knowledge has not been applied to the oceans-the largest body of water on Earth. Here we link these two fields by using laser Raman spectroscopy. We show that by far the greater volume of the ocean-some 78-85% is composed of the hydrogen bonded form (H 2 O) 5 . Without this water would not be liquid and we would literally have no ocean at all. With this knowledge we are better able to understand the processes occurring under climate-driven ocean warming.Here we briefly review this body of knowledge, and we report on both laboratory and field spectroscopic experiments to test how well the knowledge of hydrogen bonding in pure water can be translated into the medium of sea water. We describe the chemical structures that underlie the physical properties of sea water and assess their abundance in the ocean water column.In simplest terms, the structure of water is the result of the balance between the thermal forces pulling water clusters apart and the chemical forces holding thes...

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Section: Discussionmentioning

confidence: 50%

How Much H₂O Is There in the Ocean? The Structure of Water in Sea Water

2019

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“…The Raman insertion probe for the hydrothermal vent (RiP‐Hv) was inserted into the shimmering water to different depths (Li et al, 2018a; Zhang, Du, Zheng, et al, 2017). According to the characteristics of the Raman spectra (Figure 2c), the liquid trapped in the inverted lake can be divided into three layers (Figure 3b).…”

Section: Resultsmentioning

confidence: 99%

Hydrothermal Vapor‐Phase Fluids on the Seafloor: Evidence From In Situ Observations

Zhang

Luan

et al. 2020

Geophysical Research Letters

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Subseafloor phase separation is a common and significant process in hydrothermal systems and may result in a large of fluid composition differences. The temperatures of hydrothermal fluids are generally considered to be below the associated fluid boiling temperature due to mixing with ambient seawater and the phase separation process. However, we report here shimmering water with temperatures up to 383.3°C observed in a hot overturned lake at the Yokosuka site, Okinawa Trough, East China Sea, where in situ Raman spectra suggest the presence of a superheated vapor phase. Hydrothermal vents similar to the low-density hydrothermal system found at the Yokosuka site have also been observed in many other regions. Therefore, much more attention should be given to the impacts of low-density hydrothermal fluid emanations on marine environments and resource distributions.Plain Language Summary Hydrothermal systems characterized by the emanations of supercritical-and vapor-phase fluids associated with igneous activities have been observed on mid-ocean ridges. Here, we report a newly found hydrothermal system dominated by low-density vapor-phase fluids at the Yokosuka site, a hydrothermal field located in a backarc basin spreading center. Multiple methods, including in situ Raman spectroscopy measurements, thermocouple sensor measurements, and gas-tight sampling, were used to investigate this vapor-phase hydrothermal emanation. In situ observations suggest that the highest temperature (383.3°C) of the hydrothermal fluids at the Yokosuka site is above the two-phase boundary of seawater at a depth of 2,180 m (378.1°C) and in situ Raman spectra indicate the fluid of the hot overturned lake features a layered structure. Hydrothermal systems with low-density emanations are likely to be widespread throughout various tectonic settings since similar phenomena have been observed in other hydrothermal fields with conditions close to the phase separation boundary.

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“…The vastly greater fraction of water in the ocean, some 78–85%, is in the HB form. Under the extreme high‐temperature and high‐pressure conditions of hydrothermal vents, remarkable in situ Raman data show extraordinary enrichment of the nHB form (Li et al, ) that must drive enhanced water‐rock interactions.…”

Section: Ocean Warming and The Structure Of Water In Sea Watermentioning

confidence: 99%

The Molecular Basis for Understanding the Impacts of Ocean Warming

Brewer

2019

Reviews of Geophysics

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A grand challenge for ocean chemists in the years ahead lies in the need to tackle the chemical consequences of ocean warming with the same rigor and intensity that has been brought to bear on the physical chemistry of ocean acidification. For over 50 years ocean chemistry has been dominated by the study of pH‐dependent processes, but to address the biogeochemical impacts of ocean warming, we will need to rapidly advance the discipline of ocean chemical physics where temperature is the master variable and the basic unit is the Joule. Just as it would be impossible to understand the ocean CO2 system without awareness of the essential pH‐dependent CO2‐HCO3‐CO3 equilibria, so too is it impossible to describe ocean chemical physics without knowledge of the bimolecular structure of water. Water, and water in sea water, is composed of a complex of dominant hydrogen bonded forms, and the singlet molecular H2O species, in temperature‐controlled equilibrium and the ratio of these forms, can now be precisely determined. The physical properties of sea water are traditionally described by fitting an ad hoc collection of coefficients to experimental data. They are more accurately described as temperature and pressure perturbations of the underlying molecular equilibrium state. Ocean oxygen consumption rates are accurately described as an Arrhenius function, and not as an exponential function of depth as has been the tradition for over 50 years. We do not now have good correlation between ocean models and observed warming and oxygen declines, and full anoxia with the emergence of hydrogen sulfide over large regions of the ocean is possible. The parallel ocean invasions of heat and fossil fuel CO2 must be combined to estimate their full impact.

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In Situ Quantitative Raman Detection of Dissolved Carbon Dioxide and Sulfate in Deep‐Sea High‐Temperature Hydrothermal Vent Fluids

Cited by 33 publications

References 64 publications

How Much H₂O Is There in the Ocean? The Structure of Water in Sea Water

How Much H₂O Is There in the Ocean? The Structure of Water in Sea Water

Hydrothermal Vapor‐Phase Fluids on the Seafloor: Evidence From In Situ Observations

The Molecular Basis for Understanding the Impacts of Ocean Warming

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In Situ Quantitative Raman Detection of Dissolved Carbon Dioxide and Sulfate in Deep‐Sea High‐Temperature Hydrothermal Vent Fluids

Cited by 33 publications

References 64 publications

How Much H2O Is There in the Ocean? The Structure of Water in Sea Water

How Much H2O Is There in the Ocean? The Structure of Water in Sea Water

Hydrothermal Vapor‐Phase Fluids on the Seafloor: Evidence From In Situ Observations

The Molecular Basis for Understanding the Impacts of Ocean Warming

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Product

Resources

About

How Much H₂O Is There in the Ocean? The Structure of Water in Sea Water

How Much H₂O Is There in the Ocean? The Structure of Water in Sea Water