Assessment of Hg speciation changes in the sedimentary rock record from thermal desorption characteristics
Sedimentary mercury (Hg) has become a widely used proxy for paleo-volcanic activity. However, scavenging and drawdown of Hg by organic-matter (OM) and sulfides are important non-volcanic factors determining variability in such records. Most studies, therefore, normalize total Hg (HgT) to a Hg “host-...
| Main Authors: | , , , |
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| Format: | Journal article |
| Language: | English |
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American Geophysical Union
2024
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| _version_ | 1826313631328894976 |
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| author | Frieling, J Fendley, IM Nawaz, MA Mather, TA |
| author_facet | Frieling, J Fendley, IM Nawaz, MA Mather, TA |
| author_sort | Frieling, J |
| collection | OXFORD |
| description | Sedimentary mercury (Hg) has become a widely used proxy for paleo-volcanic activity. However, scavenging and drawdown of Hg by organic-matter (OM) and sulfides are important non-volcanic factors determining variability in such records. Most studies, therefore, normalize total Hg (HgT) to a Hg “host-phase” proxy (e.g., HgT/TOC for OM, HgT/TS for sulfides), with the dominant host-phase determined based on the strongest observed (linear) correlations. This approach suffers from various non-linearities in Hg-host-phase behavior and does not account for succession-level, let alone sample-level, Hg speciation changes. Thermal desorption characteristics or “profiles” (TDPs) for many Hg species during pyrolysis analysis are well-established with applications including distinguishing between OM-bound Hg and different Hg sulfides and oxides in (sub-)recent sediments. We explore the use of TDPs for geological sediment (rock) samples and illustrate the presence of multiple release phases (Hg species)—correlated to geochemical host-phase—in (almost) all the 65 analyzed Tithonian (146–145 Ma) silt and mudrock samples. By quantifying the Hg in each release phase for every sample, we find TOC concentration may determine ∼60% of the variability in the first (lower temperature) Hg TDP release phase: a stark difference with the total Hg released from these samples, where ∼20% of variation is explained by TOC variability. TDPs provide insight on sample-level Hg speciation and demonstrate that, while the common assumption of single-phase Hg speciation in sedimentary rocks is problematic, differences in Hg speciation can be detected, quantified, and accounted for using commonly applied techniques—opening potential for routine assessment. |
| first_indexed | 2024-04-23T08:26:30Z |
| format | Journal article |
| id | oxford-uuid:df0e4156-d7fd-42f9-88da-f298fca8e75e |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-09-25T04:16:10Z |
| publishDate | 2024 |
| publisher | American Geophysical Union |
| record_format | dspace |
| spelling | oxford-uuid:df0e4156-d7fd-42f9-88da-f298fca8e75e2024-07-20T14:46:10ZAssessment of Hg speciation changes in the sedimentary rock record from thermal desorption characteristicsJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:df0e4156-d7fd-42f9-88da-f298fca8e75eEnglishSymplectic ElementsAmerican Geophysical Union2024Frieling, JFendley, IMNawaz, MAMather, TASedimentary mercury (Hg) has become a widely used proxy for paleo-volcanic activity. However, scavenging and drawdown of Hg by organic-matter (OM) and sulfides are important non-volcanic factors determining variability in such records. Most studies, therefore, normalize total Hg (HgT) to a Hg “host-phase” proxy (e.g., HgT/TOC for OM, HgT/TS for sulfides), with the dominant host-phase determined based on the strongest observed (linear) correlations. This approach suffers from various non-linearities in Hg-host-phase behavior and does not account for succession-level, let alone sample-level, Hg speciation changes. Thermal desorption characteristics or “profiles” (TDPs) for many Hg species during pyrolysis analysis are well-established with applications including distinguishing between OM-bound Hg and different Hg sulfides and oxides in (sub-)recent sediments. We explore the use of TDPs for geological sediment (rock) samples and illustrate the presence of multiple release phases (Hg species)—correlated to geochemical host-phase—in (almost) all the 65 analyzed Tithonian (146–145 Ma) silt and mudrock samples. By quantifying the Hg in each release phase for every sample, we find TOC concentration may determine ∼60% of the variability in the first (lower temperature) Hg TDP release phase: a stark difference with the total Hg released from these samples, where ∼20% of variation is explained by TOC variability. TDPs provide insight on sample-level Hg speciation and demonstrate that, while the common assumption of single-phase Hg speciation in sedimentary rocks is problematic, differences in Hg speciation can be detected, quantified, and accounted for using commonly applied techniques—opening potential for routine assessment. |
| spellingShingle | Frieling, J Fendley, IM Nawaz, MA Mather, TA Assessment of Hg speciation changes in the sedimentary rock record from thermal desorption characteristics |
| title | Assessment of Hg speciation changes in the sedimentary rock record from thermal desorption characteristics |
| title_full | Assessment of Hg speciation changes in the sedimentary rock record from thermal desorption characteristics |
| title_fullStr | Assessment of Hg speciation changes in the sedimentary rock record from thermal desorption characteristics |
| title_full_unstemmed | Assessment of Hg speciation changes in the sedimentary rock record from thermal desorption characteristics |
| title_short | Assessment of Hg speciation changes in the sedimentary rock record from thermal desorption characteristics |
| title_sort | assessment of hg speciation changes in the sedimentary rock record from thermal desorption characteristics |
| work_keys_str_mv | AT frielingj assessmentofhgspeciationchangesinthesedimentaryrockrecordfromthermaldesorptioncharacteristics AT fendleyim assessmentofhgspeciationchangesinthesedimentaryrockrecordfromthermaldesorptioncharacteristics AT nawazma assessmentofhgspeciationchangesinthesedimentaryrockrecordfromthermaldesorptioncharacteristics AT matherta assessmentofhgspeciationchangesinthesedimentaryrockrecordfromthermaldesorptioncharacteristics |