Medusa-Aqua system: simultaneous measurement and evaluation of novel potential halogenated transient tracers HCFCs, HFCs and PFCs in the ocean

Abstract. This study evaluates the potential usefulness of the halogenated compounds HCFC-22, HCFC-141b, HCFC-142b, HFC-134a, HFC-125, HFC-23, PFC-14 and PFC-116 as the time-dependent oceanographic transient tracers in order to better constrain ocean ventilation processes. We collected seawater samples and improved on an established analytical technique, the Medusa-Aqua system, to simultaneous measure them, and estimate their stability in seawater following previous work on the atmospheric history and solubility. HCFC-22, HCFC-141b, HCFC-142b, HFC-134a and HFC-125 have been measured in profiles in the Mediterranean Sea for the first time. We estimated the historic surface saturation anomalies of transient tracers in the Mediterranean Sea by evaluating the historic record. Their stability in seawater was estimated by analysis of their ocean partial lifetimes, seawater surface saturations and concentrations compared to CFC-12 measurements by a well-established technique. Of the investigated compounds, HCFC-141b was found to be the most promising transient tracer in the ocean; it fulfills several essential requirements by virtue of well-documented atmospheric history, established seawater solubility, inertness in seawater and feasible measurements and indication of conservative behavior in seawater by having mean ages in agreement to be expected from both CFC-12 and SF6 observations. However, more information on degradation is needed to further identify its stability in seawater, and HCFC-141b has restrictions on production and consumption imposed by the Montreal Protocol leading to its decreasing atmospheric mole fractions since 2017. The most potential oceanic transient tracers were PFC-14 and PFC-116 due to their stability in seawater, the long and well-documented atmospheric concentrations histories and constructed seawater solubility functions, although the low solubility in seawater creates challenging measurement conditions (i.e. low concentration). Measurements of PFCs can be potentially improved by modifying the Medusa-Aqua analytical system. With the exception of providing the information on the novel potential alternative oceanic transient tracers, this study also provides a method on how to evaluate the feasibility for a compound to be a transient tracer in the ocean.

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Medusa–Aqua system: simultaneous measurement and evaluation of novel potential halogenated transient tracers HCFCs, HFCs, and PFCs in the ocean

Ocean Science ◽

10.5194/os-17-509-2021 ◽

2021 ◽

Vol 17 (2) ◽

pp. 509-525

Author(s):

Pingyang Li ◽

Toste Tanhua

Keyword(s):

Mediterranean Sea ◽

Input Function ◽

Analytical Technique ◽

Hfc 134A ◽

Surface Saturation ◽

The Mediterranean ◽

Seawater Samples ◽

Measurement And Evaluation ◽

The Baltic ◽

Hcfc 142B

Abstract. This study evaluates the potential usefulness of the halogenated compounds HCFC-22, HCFC-141b, HCFC-142b, HFC-134a, HFC-125, HFC-23, PFC-14, and PFC-116 as oceanographic transient tracers to better constrain ocean ventilation processes. We do this mainly in terms of four aspects of the characteristics of the potential tracers: input function (including atmospheric history and historical surface saturation), seawater solubility, feasibility of measurement, and stability in seawater; of these, atmospheric history and seawater solubility have been investigated in previous work. For the latter two aspects, we collected seawater samples and modified an established analytical technique for the Medusa–Aqua system to simultaneously measure these compounds. HCFC-22, HCFC-141b, HCFC-142b, HFC-134a, and HFC-125 have been measured in depth profiles in the Mediterranean Sea for the first time and for reproducibility in the Baltic Sea. We found that the historical surface saturation of halogenated transient tracers in the Mediterranean Sea is estimated to have been nearly constant at 94 % based on historical data. Of the investigated compounds, HCFC-142b, HCFC-141b, and HFC-134a are found to currently be the most promising transient tracers in the ocean. The compounds that have the greatest potential as future tracers are PFC-14 and PFC-116, mainly hampered by the low solubility in seawater that creates challenging analytical conditions, i.e., low concentrations. HCFC-22 is found to be likely unstable in warm seawater, which compromises the potential as an oceanic transient tracer, although it is possibly useful in colder water. For the compounds HFC-125 and HFC-23, we were not able to fully evaluate their potential as tracers due to inconclusive results, especially regarding their solubility and stability in seawater, but also with regard to potential analytical challenges. On the other hand, HFC-125, HFC-23, and HCFC-22 might not need to be considered because there are alternative tracers with similar input histories that are better suited as transient tracers.

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Investigation of Hg Content by a Rapid Analytical Technique in Mediterranean Pelagic Fishes

10.20944/preprints201807.0550.v1 ◽

2018 ◽

Author(s):

Giuseppa Di Bella ◽

Roberta Tardugno ◽

Nicola Cicero

Keyword(s):

Mediterranean Sea ◽

Mediterranean Area ◽

Pelagic Fish ◽

Analytical Technique ◽

Weekly Intake ◽

Tolerable Weekly Intake ◽

Direct Mercury Analyzer ◽

Mercury Analyzer ◽

Global Concern ◽

The Mediterranean

Mercury (Hg) fish and seafood contamination is a global concern and needs worldwide sea investigations in order to protect consumers. The aim of this study was to investigate the Hg concentration by means of a rapid and simple analytical technique with direct Mercury Analyzer (DMA-80) in pelagic fish species, Tetrapturus belone (spearfish), Thunnus thynnus (tuna) and Xiphias gladius (swordfish) caught in the Mediterranean Sea. Hg contents were evaluated also in Salmo salar (salmon) as pelagic fish not belonging to the Mediterranean area. The results obtained were variable ranging between 0,015-2,562 mg kg-1 for T. thynnus specie, 0,477-3,182 mg kg-1 for X. gladius, 0,434-1,730 mg kg-1 for T. belone and 0,004-0,019 mg kg-1 for S. salar, respectively. The total Hg tolerable weekly intake (TWI) and % tolerable weekly intake (TWI%) values according to the European Food Safety Authority (EFSA) were calculated. The results highlighted that the pelagic species caught in the Mediterranean Sea should be constantly monitored due to their high Hg contents as well as their TWI and TWI% with respect to S. salar samples.

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Changes in ventilation of the Mediterranean Sea during the past 25 year

Ocean Science ◽

10.5194/os-10-1-2014 ◽

2014 ◽

Vol 10 (1) ◽

pp. 1-16 ◽

Cited By ~ 37

Author(s):

A. Schneider ◽

T. Tanhua ◽

W. Roether ◽

R. Steinfeldt

Keyword(s):

Mediterranean Sea ◽

Deep Water ◽

Adriatic Sea ◽

Western Mediterranean ◽

Tyrrhenian Sea ◽

Deep Water Formation ◽

Technical Problems ◽

Water Formation ◽

The Mediterranean ◽

Transient Tracer

Abstract. Significant changes in the overturning circulation of the Mediterranean Sea has been observed during the last few decades, the most prominent phenomena being the Eastern Mediterranean Transient (EMT) in the early 1990s and the Western Mediterranean Transition (WMT) during the mid-2000s. During both of these events unusually large amounts of deep water were formed, and in the case of the EMT, the deep water formation area shifted from the Adriatic to the Aegean Sea. Here we synthesize a unique collection of transient tracer (CFC-12, SF6 and tritium) data from nine cruises conducted between 1987 and 2011 and use these data to determine temporal variability of Mediterranean ventilation. We also discuss biases and technical problems with transient tracer-based ages arising from their different input histories over time; particularly in the case of time-dependent ventilation. We observe a period of low ventilation in the deep eastern (Levantine) basin after it was ventilated by the EMT so that the age of the deep water is increasing with time. In the Ionian Sea, on the other hand, we see evidence of increased ventilation after year 2001, indicating the restarted deep water formation in the Adriatic Sea. This is also reflected in the increasing age of the Cretan Sea deep water and decreasing age of Adriatic Sea deep water since the end of the 1980s. In the western Mediterranean deep basin we see the massive input of recently ventilated waters during the WMT. This signal is not yet apparent in the Tyrrhenian Sea, where the ventilation seems to be fairly constant since the EMT. Also the western Alboran Sea does not show any temporal trends in ventilation.

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Investigation of Hg Content by a Rapid Analytical Technique in Mediterranean Pelagic Fishes

Separations ◽

10.3390/separations5040051 ◽

2018 ◽

Vol 5 (4) ◽

pp. 51 ◽

Cited By ~ 4

Author(s):

Giuseppa Di Bella ◽

Roberta Tardugno ◽

Nicola Cicero

Keyword(s):

Mediterranean Sea ◽

Mediterranean Area ◽

Pelagic Fish ◽

Analytical Technique ◽

Weekly Intake ◽

Tolerable Weekly Intake ◽

Direct Mercury Analyzer ◽

Mercury Analyzer ◽

Global Concern ◽

The Mediterranean

Mercury (Hg) fish and seafood contamination is a global concern and needs worldwide sea investigations in order to protect consumers. The aim of this study was to investigate the Hg concentration by means of a rapid and simple analytical technique with a direct Mercury Analyzer (DMA-80) in pelagic fish species, Tetrapturus belone (spearfish), Thunnus thynnus (tuna) and Xiphias gladius (swordfish) caught in the Mediterranean Sea. Hg contents were evaluated also in Salmo salar (salmon) as pelagic fish not belonging to the Mediterranean area. The results obtained were variable, ranging between 0.015–2.562 mg kg−1 for T. thynnus species, 0.477–3.182 mg kg−1 for X. gladius, 0.434–1.730 mg kg−1 for T. belone and 0.004–0.019 mg kg−1 for S. salar, respectively. The total Hg tolerable weekly intake (TWI) and tolerable weekly intake % (TWI%) values according to the European Food Safety Authority (EFSA) were calculated. The results highlighted that the pelagic species caught in the Mediterranean Sea should be constantly monitored due to their high Hg contents as well as their TWI and TWI% with respect to S. salar samples.

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Ventilation of the Mediterranean Sea constrained by multiple transient tracer measurements

Ocean Science Discussions ◽

10.5194/osd-10-1647-2013 ◽

2013 ◽

Vol 10 (5) ◽

pp. 1647-1705 ◽

Cited By ~ 3

Author(s):

T. Stöven ◽

T. Tanhua

Keyword(s):

Mediterranean Sea ◽

Deep Water ◽

Eastern Mediterranean ◽

Western Mediterranean ◽

Inverse Gaussian ◽

Ionian Sea ◽

Levantine Basin ◽

The Mean ◽

The Mediterranean ◽

Transient Tracer

Abstract. Ventilation is the prime pathway for ocean surface perturbations, such as temperature anomalies, to be relayed to the ocean interior. It is also the conduit for gas exchange between atmosphere and ocean and thus the mechanism whereby, for instance, the interior ocean is oxygenated and enriched in anthropogenic carbon. The ventilation of the Mediterranean Sea is fast in comparison to the world ocean and has large temporal variability, so that quantification of Mediterranean Sea ventilation rates is challenging and very relevant for Mediterranean oceanography and biogeochemistry. Here we present transient tracer data from a field-campaign in April 2011 that sampled a unique suite of transient tracers (SF6, CFC-12, tritium and 3He) in all major basins of the Mediterranean. We apply the Transit Time Distribution (TTD) model to the data which then constrain the mean age, the ratio of the advective/diffusive transport mechanism, and the presence, or not, of more than one significant (for ventilation) water mass. We find that the eastern part of the Eastern Mediterranean can be reasonable described with a one dimensional Inverse Gaussian (1IG) TTD, and thus constrained with two independent tracers. The ventilation of the Ionian Sea and the Western Mediterranean can only be constrained by a multidimensional TTD. We approximate the ventilation with a two-dimensional Inverse Gaussian (2IG) TTD for these areas and demonstrate one way of constraining a 2IG-TTD from the available transient tracer data. The deep water in the Ionian Sea has higher mean ages than the deep water of the Levantine Basin despite higher transient tracer concentrations. This is partly due to the deep water of Adriatic origin having more diffusive properties in the transport and formation, i.e. a high ratio of diffusion over advection, compared to the deep water of Aegean Sea origin that still dominates the deep Levantine Basin deep water after the Eastern Mediterranean Transient (EMT) in the early 1990s. We also show that the deep Western Mediterranean has approximately 40% contribution of recently ventilated deep water from the Western Mediterranean Transition (WMT) event of the mid-2000s. The deep water has higher transient tracer concentrations than the mid-depth water, but the mean age is similar.

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Recent Changes in Deep Ventilation of the Mediterranean Sea; Evidence From Long-Term Transient Tracer Observations

Frontiers in Marine Science ◽

10.3389/fmars.2020.00594 ◽

2020 ◽

Vol 7 ◽

Cited By ~ 1

Author(s):

Pingyang Li ◽

Toste Tanhua

Keyword(s):

Mediterranean Sea ◽

The Mediterranean ◽

Transient Tracer

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Changes in ventilation of the Mediterranean Sea during the past 25 yr

Ocean Science Discussions ◽

10.5194/osd-10-1405-2013 ◽

2013 ◽

Vol 10 (4) ◽

pp. 1405-1445 ◽

Cited By ~ 3

Author(s):

A. Schneider ◽

T. Tanhua ◽

W. Roether ◽

R. Steinfeldt

Keyword(s):

Mediterranean Sea ◽

Deep Water ◽

Adriatic Sea ◽

Western Mediterranean ◽

Tyrrhenian Sea ◽

Deep Water Formation ◽

Overturning Circulation ◽

Water Formation ◽

The Mediterranean ◽

Transient Tracer

Abstract. The Mediterranean Sea has a fast overturning circulation and the deep water masses are well ventilated in comparison to the deep waters of the world ocean. Significant changes in the overturning circulation has been observed during the last few decades, the most prominent phenomena being the Eastern Mediterranean Transient (EMT) in the early 1990s and the Western Mediterranean Transit (WMT) near the mid of the decade following. During both of these events unusually large amounts of deep water were formed, and in the case of the EMT, the deep water formation area shifted from the Adriatic to the Aegean Sea. This variability is important to understand and to monitor, because ventilation is the main process to propagate surface perturbations, such as uptake of anthropogenic CO2, into the ocean interior. Here we synthesize a unique collection of transient tracer (CFC-12, SF6 and tritium) data from nine cruises conducted between 1987 and 2011 and use these data to determine temporal variability of Mediterranean ventilation. We also discuss biases and technical problems with transient tracer-based ages arising from their different input histories over time; particularly in the case of time-dependent ventilation. We observe a period of stagnation in the deep eastern (Levantine) basin after it was ventilated by the EMT so that the age of the deep water is increasing with time. In the Ionian Sea, on the other hand, we see evidence of increased ventilation after year 2001, indicating the restarted deep water formation in the Adriatic Sea. This is also reflected in the increasing age of the Cretan Sea deep water and decreasing age of Adriatic Sea deep water since the end of the 1980s. In the western Mediterranean deep basin we see the massive input of recently ventilated waters during the WMT. This signal is not yet apparent in the Tyrrhenian Sea, where the ventilation seems to be fairly constant since the EMT. Also the western Alboran Sea does not show any temporal trends in ventilation.

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