Organic proxies in speleothems: analytical method and first data from cave KNI-51

Speleothems are important archives for paleo environments thanks to their high temporal resolution and potential for precise and accurate dating. Organic biomarkers in speleothems are not widely explored because of low concentrations and high sample amount required to obtain detectable levels. The potential for paleoenvironmental reconstruction from organic molecules in speleothems is high, but low contamination and high sensitivity analytical tools are required to obtain well resolved and reliable records. We developed a method for the analysis of fire-derived polycyclic aromatic hydrocarbons (PAHs) and nalkanes in speleothems and applied it to aragonite stalagmites from cave KNI-51 in the central Australian tropics. These stalagmites have already been precisely dated by U/Th methods, and have detailed oxygen isotopic time series that provide a detailed record of past Australian monsoon rainfall variability [1]. The characteristics of the cave make it suitable for this research, thanks to the considerably high growth rates of the stalagmites (1-2 mm yr-1), that allow analysis at an annual resolution. In addition, cave KNI-51 is shallow, contained within highly permeable rillenkarren limestone, and overlain by extremely thin, carbon-poor soils. Thus, the sequestration, biodegradation, or mobilization of PAHs and n-alkanes in soils and bedrock are minimized, allowing them to be easily transported from the surface to the stalagmite. In order to check for the risk of contamination of the aragonite layers during flooding episodes, we also analyzed sediments from above and inside the cave. Results show that flood sediments do not bias our analyses of carbonate material. With respect to the few existing methods for PAH analysis in speleothems [2, 3], some substantial modifications were made to the pre-analytical phase, all of which were aimed at increasing the analytical signal: our analytical protocol allows detection of analytes in stalagmites at the ng to sub-ng level by guaranteeing the lowest contamination. Samples are drilled from pre-cleaned stalagmite slabs, dissolved in HCl at low temperature, solvent-extracted and volume reduced in a class 10,000 organic cleanroom. 19 different 2- to 6-ring PAH compounds and 26 n-alkanes (C10-C35) were analyzed and quantified by GC-MS. Preliminary results suggest increased fire activity in the mid-15thcentury, marked in particular by the presence of fluoranthene, pyrene, benzo(e)pyrene and indeno(1,2,3-c,d)pyrene. Only high molecular weight n-alkanes in the range C23-C32 had significant concentrations in most samples, showing no marked odd-even predominance, likely indicating the presence of another source beside plant residues in soil

Millennial-Scale Climate and Human Drivers of Environmental Change and Fire Activity in a Dry, Mixed-Conifer Forest of Northwestern Montana

Warm summer temperatures and longer fire seasons are promoting larger, and in some cases, more fires that are severe in low- and mid-elevation, dry mixed-conifer forests of the Northern Rocky Mountains (NRM). Long-term historical fire conditions and human influence on past fire activity are not well understood for these topographically and biophysically heterogeneous forests. We developed reconstructions of millennial-scale fire activity, vegetation change, and human presence at Black Lake, a small closed-basin lake on the Flathead Indian Reservation in the Mission Valley, Northwestern Montana, United States. Fossil pollen, charcoal, and biomarkers associated with human presence were used to evaluate the interaction between climate variability, fire activity, vegetation change and human activity for the past 7000 years. Comparisons among multiple proxies suggest climate variability acted as the primary control on fire activity and vegetation change from the early Holocene until the late Holocene when records suggest fire activity and climate variability decoupled. Specific biomarkers (5β-stanols including coprostanol and epi-coprostanol) associated with human presence indicate humans were present within the Black Lake watershed for thousands of years, although the inferred intensity of human presence is highly variable. A strong relationship between climate variability and fire activity during the early and mid-Holocene weakens during the last few thousand years, suggesting possible increased influence of humans in mediating fire activity in recent millennia, and/or a shift in the interaction between the distribution and abundance of woody fuel and fire severity. Human-set fires during the cooler and wetter late Holocene may have been aimed at maintaining important cultural resources associated with the heterogeneous mosaic of mixed conifer forests within the Black Lake watershed. The paleoenvironmental reconstruction at Black Lake corroborates archeological records that show humans were present within the Black Lake watershed for over 7000 years. Further research is needed to evaluate the evidence for this continuous presence and the possible role that people played in shaping fire regimes and vegetation within low- to mid-elevation mixed-conifer ecosystems of the NRM

Multi-biomarker analysis of sediments for paleoclimate research

Lacustrine sedimentary cores provide continuous records of large-scale and local environmental modifications, intelligible thanks to specific organic markers that accumulated in these archives during past millennia. In order to improve our knowledge on ecosystem changes due to biomass burning events and human presence during the Holocene, an effective analytical method to detect organic compounds contained in sediment samples is needed. We used Accelerated Solvent Extraction (ASE) technique followed by analysis with gas and liquid chromatographers coupled with mass spectrometers (GC-MS, IC-MS). The extraction of the molecules of interest from the sediments is made with a mixture of DCM:MeOH 9:1 v/v and it is followed by a 3 steps purification with silica gel columns. The first fraction is eluted with HEX:DCM 9:1 v/v and contains n-alkanes, indicators of vegetation, and polycyclic aromatic hydrocarbons (PAHs) as combustion proxies. Then, a second fraction is eluted with DCM and derivatized with the silylation process, in order to get the faecal sterols and stanols (FeSts), indicators of past human and grazing animals presence. These two fractions are analysed with the GC-MS technique. The third and last fraction is eluted with MeOH and contains the monosaccharide anhydrides (MAs), specific indicators of vegetation burning processes, which are analysed with IC-MS. Internal standards labelled C13 are used for the quantification and procedural blanks are extracted every batch of 12 samples. The method may undergo variations, on the basis of the complex sediment matrices which not always lend itself to the same kind of treatment. However, the technique was applied in different lakes from different continents and the obtained results, compared with historical and climate literature data, seem to demonstrate the potentiality of the method as a resourceful instrument to reconstruct past burning events and human-ecosystem interactions

Late Holocene records of fire and human presence in New Zealand

New Zealand, and the South Island in particular, can be considered an excellent test site for the study of the early impact of humans on the environment for two main reasons: the Polynesian settlement occurred only about 700-800 y BP and resulted in abrupt and huge landscape modifications. Burning forest for land clearance impacted dramatically on an ecosystem that was not adapted to fire, changing the composition of the vegetation as documented by sedimentary charcoal and pollen records. Although charcoal data give incontrovertible evidence of some unprecedented fire events right after the arrival of the Maori, its significance as a tracer for local and anthropogenic fire events has been questioned, stressing the need for new markers to confirm and complete the information about human presence and its effective impact. In the present work, faecal sterols and polycyclic aromatic hydrocarbons (PAHs) were individuated as suitable molecular markers and analyzed by GC-MS in a sediment core from Lake Kirkpatrick, located in the Lake Wakatipu catchment at 570 m a.s.l. in the South Island of New Zealand. Coprostanol accounts for about 60% of total sterol content in human faeces, being much less relevant in animal dejections. Together with its degradation product epi-coprostanol, it is well conserved in sedimentary archives and can be highly useful in paleoenvironmental reconstructions of human settlements. PAHs are produced in relevant amounts by combustion in conditions of oxygen depletion, and diagnostic ratios (DR) between specific molecules can be used for inferring fuel and sources. The charcoal record for Lake Kirkpatrick shows major fire episodes around AD 1350, confirmed by corresponding high levels of PAHs ascribable to biomass burning (as further evidenced by DR) at c. AD 1350. Moreover, the same trend is observed also in the fluxes of coprostanol and epi-coprostanol, whose sum results in two peaks at c. AD 1346 and 1351. This finding confirms not only the massive presence of humans in the area and the large use of fire at the time, but also complements and refines the reconstructions enabled by charcoal analysis

Organic Biomarkers of Fire in Tropical Australian Stalagmites of the Last Millennium

Fire plays a critical role in the ecology of the dry tropics of Western Australia, with ignition generated by human activities and lightning strikes. Attempts to understand temporal changes in rates of biomass burning are hampered by a sparsity of records that are continuous, provide clear evidence of fire at high temporal resolution, and span multiple centuries. Aragonite stalagmites from cave KNI-51, central Australian tropics, have been previously analyzed, with U/Th ratios providing a precise chronology and oxygen isotopic ratios providing a record of past Australian monsoon rainfall variability. We demonstrate that these stalagmites also contain polycyclic aromatic hydrocarbons (PAHs), organic molecules produced by combustion, including biomass burning, and characterized by high persistence in the environment. As such, these stalagmites may serve as a novel proxy for paleofire activity. Cave KNI-51 is shallow, contained within highly permeable rillenkarren limestone, and overlain by extremely thin, carbon-poor soils. PAH sequestration, biodegradation, or mobilization in thick soils and massive bedrock – issues that would complicate transmission of PAHs from the surface to the stalagmite - are minimized. Analysis of stalagmite mud layers, which are common in these samples and are derived from cave flooding events, reveal extremely low PAH concentrations and thus pose minimal or no risk of contamination of the aragonite carbonate. In addition, stalagmite growth rates are high (1-2 mm yr-1), and thus the stalagmites appear capable of recording fire events at ~annual scales. The analytical protocol we have developed for PAHs allows detection in stalagmites at the pg level by guaranteeing the lowest contamination. Samples are drilled from pre-cleaned stalagmite slabs and solvent-extracted in the organic cleanroom after acid digestion at cold temperature. A total of 19 different 2- to 6-ring PAH compounds are analyzed and quantified by GC-MS. Analysis of stalagmite layers deposited over the past millennium are underway, with preliminary data suggesting increased fire activity in the mid-15th century, marked in particular by the presence of fluoranthene, pyrene, benzo(e)pyrene and indeno(1,2,3-c,d)pyrene in the range 2-12 ng g-1

Multiphase Hydrogenation of -Glucosamine Hydrochloride, N-Acetyl- -Glucosamine, -Glucose, and -Maltose over Ru/C with Integrated Catalyst Recovery

A multiphase (MP) system composed of two immiscible liquids, water and isooctane, and commercial 5% Ru/C as a catalyst, both with and without an additional organic liquid (OL: tetrahydrofuran (THF), 2-methyl-THF, methyl isobutyl carbinol, and cyclopentyl methyl ether) was designed and investigated for the chemoselective catalytic hydrogenation of four model examples of biobased sugars and amino/amido-sugars. At 110 degrees C and 40 bar of H-2, D-glucosamine hydrochloride and N-acetyl-D-glucosamine were converted selectively into their corresponding hydrogenated derivatives, 2-amino-D-sorbitol and 2-acetamide-D-sorbitol, respectively, isolated in >99% yields. Both the reagents and the products were converted and formed in the aqueous phase, respectively, while, by tuning the relative proportions of water, isooctane, and the third added liquid (particularly THF), the catalyst (Ru/C) was perfectly segregated in the organic layer, where it could be recycled and reused up to nine times without any loss of activity and selectivity, in a semicontinuous mode. Under such conditions, the reaction was implemented on a gram scale with a productivity up to 0.89 mmol 2-amino-D-sorbitol/(g(cat) h). The same hydrogenation efficiency and reagent/product/catalyst separation were achieved during the MP reactions of D-glucose and D-maltose. In this case, however, results were independent of the MP composition: at 120 degrees C and 20-40 bar of H-2, using either H2O/isooctane or H2O/isooctane/OL systems, a quantitative conversion of D-glucose and D-maltose was reached with a selectivity up to 78 and >99% toward sorbitol and maltitol, respectively. Ru/C was perfectly separated out of the aqueous phase in both MP mixtures, with a negligible metal leaching, below 0.01 wt %. The multiphase approach for all the tested substrates proved not only to be an original and robust protocol to improve the product isolation and catalyst recycling, but also effective in preventing metal contamination in the synthesis of final derivatives

Fire and human record at Lake Victoria, East Africa, during the Early Iron Age: Did humans or climate cause massive ecosystem changes?

Organic molecular markers determined in a sediment core (V95-1A-1P) from Lake Victoria (East Africa) were used to reconstruct the history of human impact and regional fire activity during the Early Iron Age (~2400 to ~1100 yr BP). Fire history was reconstructed using levoglucosan and polycyclic aromatic hydrocarbons (PAHs) as markers for biomass burning that demonstrate two distinct fire periods peaking at 1450–1700 and 1850–2050 cal. yr BP. A partial correlation between levoglucosan and PAHs is interpreted as different transport behaviors and burn temperatures affecting the proxies. A fecal sterol index (CoP-Index) indicates the presence of humans near the lakeshore, where the CoP-Index lags a few centuries behind the fire peaks. The CoP-Index peaks between 1850 and1950 cal. yr BP and between 1400 and 1500 cal. yr BP. Retene, a PAH that indicates softwood combustion, differs from other PAHs and levoglucosan by abruptly increasing at ~1650 cal. yr BP and remaining high until 1200 cal. yr BP. This increase may potentially signal human activity in that the development of metallurgy and/or ceramic production requires highly efficient fuels. However, this increase in retene occurs at the same time as severe drought events centered at ~1500 and ~2000 yr BP where the droughts and associated woodland to grassland transition may have resulted in more intense fires. The grassland expansion could have created favorable conditions for human activities and triggered settlement growth that in turn may have created a positive feedback for further landscape opening

Polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in Antarctic ice-free areas: Influence of local sources on lakes and soils

Antarctica is usually considered a pristine ecosystem; nevertheless it is influenced by Persistent Organic Pollutants (POPs),mainly driven by long-range atmospheric transport (LRAT). However, localized sources such as human and wildlife activities can also contribute to pollution, constituting contaminated points at a local scale. Antarctic ice-free areas, where rare lakes are located, are influenced by such sources. In this work we determine polychlorinated biphenyls (PCBs, including the non-Aroclor CB-11) and polybrominated diphenyl ethers (PBDEs) in water and sediment samples of 6 lakes in Northern Victoria Land and in soils near the Italian research station Mario Zucchelli. Determinations were performed through gas chromatography (GC) coupled both to low-resolution and highresolution mass spectrometry (LRMS, HRMS). POP concentrations in lakes resulted low and rather similar across the sites despite their distance: ΣPCBs range between 46 and 143 pg L−1 in water and 10 and 634 pg g−1 in sediments, while ΣPBDEs range between 60 and 151 pg L−1 in water and 193 and 1682 pg g−1 in sediments. Lakes exhibited limited amplification phenomena in water during the melting season. PBDEs in the soils near the base yielded more concerning results, reaching a concentration of 33 ng g−1

Characterization of metals in air and soil near a steel making plant in the North part of Italy

Purpose – The purpose of this paper is to define suitable tracers that are particularly significant in assessing the impact on the surrounding environment caused by a steel making plant. Design/methodology/approach – The authors focussed on the detection and quantification of inorganic pollutants such as heavy metals in the soil and in the air in the surrounding area of the steel making plant. The presented data, concerning a plant in the North part of Italy, come from an approach that took into account the advantages of different devices and sampling criteria: apart from conventional devices, two kinds of deposimeters have been used (for characterizing either total or wet/dry depositions). Their locations have been chosen taking into account the distance from the plant. Findings – The paper demonstrates that the presence of diffused emissions plays an important (negative) role still today; thus a modern plant should reduce this kind of emission in order to be accepted from the population living in the surroundings. In the analyzed case study, the benefits of adopting the best available technologies can be seen from the temporal variability of the incidence of the plant. Originality/value – The value of the paper is in the support that it can give to decision makers that must manage a steel making plant in an area.Purpose – The purpose of this paper is to define suitable tracers that are particularly significant in assessing the impact on the surrounding environment caused by a steel making plant. Design/methodology/approach – The authors focussed on the detection and quantification of inorganic pollutants such as heavy metals in the soil and in the air in the surrounding area of the steel making plant. The presented data, concerning a plant in the North part of Italy, come from an approach that took into account the advantages of different devices and sampling criteria: apart from conventional devices, two kinds of deposimeters have been used (for characterizing either total or wet/dry depositions). Their locations have been chosen taking into account the distance from the plant. Findings – The paper demonstrates that the presence of diffused emissions plays an important (negative) role still today; thus a modern plant should reduce this kind of emission in order to be accepted from the population living in the surroundings. In the analyzed case study, the benefits of adopting the best available technologies can be seen from the temporal variability of the incidence of the plant. Originality/value – The value of the paper is in the support that it can give to decision makers that must manage a steel making plant in an area

Gas-particle distributions, sources and health effects of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and polychlorinated naphthalenes (PCNs) in Venice aerosols

Air samples were collected in Venice during summer 2009 and 2012 to measure gas and particulate concentrations of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and polychlorinated naphthalenes (PCNs). PCB-11, considered a marker for non-Aroclor contamination of the environment,was found for the first time in the Venetian lagoon and in Europe. An investigation on sources has been conducted, evidencing traffic as the major source of PAHs, whereas PCBs have a similar composition to Aroclor 1248 and 1254; in 2009 a release of PCN-42 has been hypothesized. Toxicological evaluation by TCA and TEQ methods, conducted for the first time in Venice air samples, identified BaP, PCB-126 and PCB-169 as the most important contributors to the total carcinogenic activity of PAHs and the total dioxin-like activity of PCBs and PCNs