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| 2. |
- Martinez Cortizas, A., et al.
(författare)
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Reconstructing historical Pb and Hg pollution in NW Spain using multiple cores from the Chao de Lamoso bog (Xistral Mountains)
- 2012
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Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037 .- 1872-9533. ; 82, s. 68-78
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Tidskriftsartikel (refereegranskat)abstract
- We have applied a single-bog multi-core approach to reconstruct historical Pb and Hg accumulation in an ombrotrophic bog from NW Spain, Chao de Lamoso (Xistral Mountains). Mercury was determined using a LECO-ALTEC AMA-254 analyzer, Pb with an EMMA-XRF analyzer and stable lead isotopes (four cores) by Quadrupole ICP-MS. Maximum concentrations were 74-122 mu g g(-1) for Pb and 142-300 ng g(-1) for Hg. Higher variability was found for Hg than for Pb (2-3 times and 1.5 times, respectively). The slopes of the relationship between Hg and Pb cumulative inventories also suggested differences in relative accumulation of both elements. This substantial spatial variability indicates that, compared with Pb, a more extended sampling may be needed for an accurate estimation of Hg accumulation in mires. The isotopic records showed higher and almost constant Pb-206/Pb-207 ratios (average 1.174 +/- 0.004) in the lower sections and a continuous decrease to the surface (minimum 1.141). By using the change in the isotopic composition of Pb we estimated a chronology for the last similar to 200 years which enabled and approximation of the temporal trends in metal pollution. Based on the average isotopic composition of the studied cores and the application of a simple binary mixing model, six periods with increasing proportions of pollution Pb were identified: prior to similar to 1875 AD, with an average proportion lower than 16%; similar to 1875-1910 AD, increasing up to 24%; similar to 1910-1950 AD, up to 35%; similar to 1950-1970, up to 54%; similar to 1970-1980 AD, up to 74%; and after similar to 1980 AD, increasing up to 80%. The period with the highest rate of increase in recent (since similar to 1900 AD) pollution Pb (equivalent to 2% year(-1)) seems to have started at the maximum in Pb accumulation around the early 1970s. The Hg records showed a more simple evolution with four main phases: prior to similar to 1875 AD with enrichments around 1.5-fold the background, similar to 1875-1955 AD with increasing enrichments; from similar to 1955 AD to similar to 1980 AD with maximum values (up to 4.2-fold); and from similar to 1980 AD to present, with a steady decline to 2.4-fold. For the most recent period (after similar to 1980 AD), the combination of decreasing Pb and Hg concentrations and accumulation rates/enrichments, and low Pb-206/Pb-207 ratios, may point to a higher relative importance of local sources (i.e. coal burning in a nearby power plant) in atmospheric metal pollution in the area.
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- Naafs, B. D. A., et al.
(författare)
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Introducing global peat-specific temperature and pH calibrations based on brGDGT bacterial lipids
- 2017
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Ingår i: Geochimica et Cosmochimica Acta. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0016-7037 .- 1872-9533. ; 208, s. 285-301
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Tidskriftsartikel (refereegranskat)abstract
- Glycerol dialkyl glycerol tetraethers (GDGTs) are membrane-spanning lipids from Bacteria and Archaea that are ubiquitous in a range of natural archives and especially abundant in peat. Previous work demonstrated that the distribution of bacterial branched GDGTs (brGDGTs) in mineral soils is correlated to environmental factors such as mean annual air temperature (MAAT) and soil pH. However, the influence of these parameters on brGDGT distributions in peat is largely unknown. Here we investigate the distribution of brGDGTs in 470 samples from 96 peatlands around the world with a broad mean annual air temperature (-8 to 27 degrees C) and pH (3-8) range and present the first peat-specific brGDGT-based temperature and pH calibrations. Our results demonstrate that the degree of cyclisation of brGDGTs in peat is positively correlated with pH, pH = 2.49 x CBTpeat + 8.07 (n = 51, R-2 = 0.58, RMSE = 0.8) and the degree of methylation of brGDGTs is positively correlated with MAAT, MAAT(peat) (degrees C) = 52.18 x MBT'(5me) - 23.05 (n = 96, R-2 = 0.76, RMSE = 4.7 degrees C). These peat-specific calibrations are distinct from the available mineral soil calibrations. In light of the error in the temperature calibration (similar to 4.7 degrees C), we urge caution in any application to reconstruct late Holocene climate variability, where the climatic signals are relatively small, and the duration of excursions could be brief. Instead, these proxies are well-suited to reconstruct large amplitude, longer-term shifts in climate such as deglacial transitions. Indeed, when applied to a peat deposit spanning the late glacial period (similar to 15.2 kyr), we demonstrate that MAAT(peat) yields absolute temperatures and relative temperature changes that are consistent with those from other proxies. In addition, the application of MAAT(peat) to fossil peat (i.e. lignites) has the potential to reconstruct terrestrial climate during the Cenozoic. We conclude that there is clear potential to use brGDGTs in peats and lignites to reconstruct past terrestrial climate.
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| 4. |
- Serrano, O., et al.
(författare)
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Millennial scale impact on the marine biogeochemical cycle of mercury from early mining on the Iberian Peninsula
- 2013
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Ingår i: Global Biogeochemical Cycles. - : American Geophysical Union (AGU). - 0886-6236 .- 1944-9224. ; 27:1, s. 21-30
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Tidskriftsartikel (refereegranskat)abstract
- The high-resolution mercury record of a Posidonia oceanica mat in the northwest Mediterranean provides an unprecedented testimony of changes in environmental mercury (Hg) loading to the coastal marine environment over the past 4315 yr BP. The period reconstructed made it possible to establish tentative preanthropogenic background Hg levels for the area (6.8 +/- 1.5 ng g(-1) in bulk sediments). A small, but significant, anthropogenic Hg increase was identifiable by similar to 2500 yr BP, in agreement with the beginning of intense mining in Spain. Changes in the record suggest four major periods of anthropogenic Hg pollution inputs to the Mediterranean: first, during the Roman Empire (2100-1800 yr BP); second, in the Late Middle Ages (970-650 yr BP); third, in the modern historical era (530-380 yr BP); and fourth, in the industrial period (last 250 years), with Hg concentrations two-, four-, five-, and tenfold higher than background concentrations, respectively. Hg from anthropogenic sources has dominated during the last millennium (increase from similar to 12 to similar to 100 ng g(-1)), which can be related to the widespread historical exploitation of ore resources on the Iberian Peninsula. The chronology of Hg concentrations in the mat archive, together with other Hg pollution records from the Iberian Peninsula, suggests regional-scale Hg transport and deposition and shows earlier marine Hg pollution than elsewhere in Europe. Moreover, the mat also records a higher number of historic contamination phases, in comparison with other natural archives, probably due to the fact that the bioaccumulating capacity of P. oceanica magnify environmental changes in Hg concentrations. In this study, we demonstrate the uniqueness of P. oceanica meadows as a long-term archive recording trends in Hg abundance in the marine coastal environment, as well as its potential role in the Mediterranean as a long-term Hg sink.
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