Radiocarbon Analysis of Elemental and Organic Carbon in Switzerland during Winter-Smog Episodes from 2008 to 2012 – Part I: Source Apportionment and Spatial Variability

While several studies have investigated winter-time air pollution with a wide range of concentration levels, hardly any results are available for longer time periods covering several winter-smog episodes at various locations; e.g., often only a few weeks from a single winter are investigated. Here, we present source apportionment results of winter-smog episodes from 16 air pollution monitoring stations across Switzerland from five consecutive winters. Radiocarbon (14C) analyses of the elemental (EC) and organic (OC) carbon fractions, as well as levoglucosan, major water-soluble ionic species and gas-phase pollutant measurements were used to characterize the different sources of PM10. The most important contributions to PM10 during winter-smog episodes in Switzerland were on average the secondary inorganic constituents (sum of nitrate, sulfate and ammonium = 41 ± 15%) followed by organic matter (OM) (34 ± 13%) and EC (5 ± 2%). The non-fossil fractions of OC (fNF,OC) ranged on average from 69 to 85 and 80 to 95% for stations north and south of the Alps, respectively, showing that traffic contributes on average only up to ~ 30% to OC. The non-fossil fraction of EC (fNF,EC), entirely attributable to primary wood burning, was on average 42 ± 13 and 49 ± 15% for north and south of the Alps, respectively. While a high correlation was observed between fossil EC and nitrogen oxides, both primarily emitted by traffic, these species did not significantly correlate with fossil OC (OCF), which seems to suggest that a considerable amount of OCF is secondary, from fossil precursors. Elevated fNF,EC and fNF,OC values and the high correlation of the latter with other wood burning markers, including levoglucosan and water soluble potassium (K+) indicate that residential wood burning is the major source of carbonaceous aerosols during winter-smog episodes in Switzerland. The inspection of the non-fossil OC and EC levels and the relation with levoglucosan and water-soluble K+ shows different ratios for stations north and south of the Alps (most likely because of differences in burning technologies) for these two regions in Switzerland.

Source apportionment of elemental carbon in Beijing, China: insights from radiocarbon and organic marker measurements

Elemental carbon (EC) or black carbon (BC) in the atmosphere has a strong influence on both climate and human health. In this study, radiocarbon (14C) based source apportionment is used to distinguish between fossil fuel and biomass burning sources of EC isolated from aerosol filter samples collected in Beijing from June 2010 to May 2011. The 14C results demonstrate that EC is consistently dominated by fossil-fuel combustion throughout the whole year with a mean contribution of 79% ± 6% (ranging from 70% to 91%), though EC has a higher mean and peak concentrations in the cold season. The seasonal molecular pattern of hopanes (i.e., a class of organic markers mainly emitted during the combustion of different fossil fuels) indicates that traffic-related emissions are the most important fossil source in the warm period and coal combustion emissions are significantly increased in the cold season. By combining 14C based source apportionment results and picene (i.e., an organic marker for coal emissions) concentrations, relative contributions from coal (mainly from residential bituminous coal) and vehicle to EC in the cold period were estimated as 25 ± 4% and 50 ± 7%, respectively, whereas the coal combustion contribution was negligible or very small in the warm period.

Source apportionment and dynamic changes of carbonaceous aerosols during the haze bloom-decay process in China based on radiocarbon and organic molecular tracers

Fine carbonaceous aerosols (CAs) is the key factor influencing the currently filthy air in megacities in China, yet few studies simultaneously focus on the origins of different CAs species using specific and powerful source tracers. Here, we present a detailed source apportionment for various CAs fractions, including organic carbon (OC), water-soluble OC (WSOC), water-insoluble OC (WIOC), elemental carbon (EC) and secondary OC (SOC) in the largest cities of North (Beijing, BJ) and South China (Guangzhou, GZ), using the measurements of radiocarbon and anhydrosugars. Results show that non-fossil fuel sources such as biomass burning and biogenic emission make a significant contribution to the total CAs in Chinese megacities: 56±4 in BJ and 46±5% in GZ, respectively. The relative contributions of primary fossil carbon from coal and liquid petroleum combustions, primary non-fossil carbon and secondary organic carbon (SOC) to total carbon are 19, 28 and 54% in BJ, and 40, 15 and 46% in GZ, respectively. Non-fossil fuel sources account for 52 in BJ and 71% in GZ of SOC, respectively. These results suggest that biomass burning has a greater influence on regional particulate air pollution in North China than in South China. We observed an unabridged haze bloom-decay process in South China, which illustrates that both primary and secondary matter from fossil sources played a key role in the blooming phase of the pollution episode, while haze phase is predominantly driven by fossil-derived secondary organic matter and nitrate.

(Table 1) Maceral composition and organic carbon chemistry of ODP Leg 104 samples

The Cenozoic sediments sampled in ODP Leg 104 on the Vøring Plateau show a distinct variability of the total organic carbon content (TOC) and the accumulation rates of TOC. Based on the geochemical and organic-petrographic characterization of the sedimentary organic matter (OM), the allochthonous and autochthonous proportion of the OM could be quantified. The results clearly demonstrate that high TOC percentages and TOC accumulation rates in Cenozoic sediment sections display a generally high input of allochthonous organic matter. Oxidized and partly well-rounded organic particles built up the main portion of OM within the Miocene, TOC-rich sediments. The most probable source of this oxidized OM are reworked sediments from the Scandinavian shelf. Changes in the input of these organic particles are to some degree correlative with sea-level changes. The Cenozoic accumulation of autochthonous OM is low and does not reveal a clear variation during the Miocene and early Pliocene. In spite of a high accumulation rate of biogenic opal during the Early Miocene, the accumulation rate of autochthonous TOC is low. The autochthonous particle assemblage is dominated by relatively inert OM, like dinoflagellate cysts. This points to an intensive biological and/or early diagenetic degradation of the marine OM under well oxidized bottom water conditions during the last 23 Myr. Nevertheless, a continuation of marine OM degradation during later stages of diagenesis cannot be excluded. A prominent dominance of allochthonous OM over autochthonous is documented with the beginning of the Pliocene. At 2.45 Ma the episodic occurrence of ice-rafted, thermally mature OM reflects the onset of the glacial erosion of Mesozoic, coal and black shale bearing sediments on the Scandinavian and Barents Sea shelves. The first occurrence of these, in view of the actual burial depth, thermally overmature OM particles is, therefore, a marker for the beginning of the strong Scandinavian glaciation and the advance of the glacial front toward the shelves.

Multi-sensor global compilation of mid-Holocene sea surface temperatures, based on Mg/Ca and alkenone palaeothermometry and reconstructions obtained using planktonic foraminifera and organic-walled dinoflagellate cyst

We present and examine a multi-sensor global compilation of mid-Holocene (MH) sea surface temperatures (SST), based on Mg/Ca and alkenone palaeothermometry and reconstructions obtained using planktonic foraminifera and organic-walled dinoflagellate cyst census counts. We assess the uncertainties originating from using different methodologies and evaluate the potential of MH SST reconstructions as a benchmark for climate-model simulations. The comparison between different analytical approaches (time frame, baseline climate) shows the choice of time window for the MH has a negligible effect on the reconstructed SST pattern, but the choice of baseline climate affects both the magnitude and spatial pattern of the reconstructed SSTs. Comparison of the SST reconstructions made using different sensors shows significant discrepancies at a regional scale, with uncertainties often exceeding the reconstructed SST anomaly. Apparent patterns in SST may largely be a reflection of the use of different sensors in different regions. Overall, the uncertainties associated with the SST reconstructions are generally larger than the MH anomalies. Thus, the SST data currently available cannot serve as a target for benchmarking model simulations.

Radiocarbon dating, sedimentation rate, granulometry and organic carbon content of ODP Leg 182 sites

This data report presents sedimentological (grain size) and geochemical (X-ray diffraction, total organic carbon, accelerator mass spectrometry radiocarbon, and percent carbonate) information obtained from the western transect (Sites 1132, 1130, and 1134) and the eastern transect (Sites 1129, 1131, and 1127) in the Great Australian Bight during Leg 182. The purpose is to quantify changing rates of sediment accumulation and changes in sediment type from the late Pleistocene and Holocene, in order to relate these changes to the well-known sea level curve that exists for this time frame. Ultimately, these data can be used to more effectively interpret lithologic variations deeper in the Pleistocene succession, which most likely represent orbitally forced sea level events.

Profiles of diatoms, pollen, XRD, XRF and organic composition of two sediment cores (PG2022 and PG2023) from Lake Kyutyunda in Yakutia, NE Siberia, Russia

Although the climate development over the Holocene in the Northern Hemisphere is well known, palaeolimnological climate reconstructions reveal spatiotemporal variability in northern Eurasia. Here we present a multi-proxy study from north-eastern Siberia combining sediment geochemistry, and diatom and pollen data from lake-sediment cores covering the last 38,000 cal. years. Our results show major changes in pyrite content and fragilarioid diatom species distributions, indicating prolonged seasonal lake-ice cover between ~13,500 and ~8,900 cal. years BP and possibly during the 8,200 cal. years BP cold event. A pollen-based climate reconstruction generated a mean July temperature of 17.8°C during the Holocene Thermal Maximum (HTM) between ~8,900 and ~4,500 cal. years BP. Naviculoid diatoms appear in the late Holocene indicating a shortening of the seasonal ice cover that continues today. Our results reveal a strong correlation between the applied terrestrial and aquatic indicators and natural seasonal climate dynamics in the Holocene. Planktonic diatoms show a strong response to changes in the lake ecosystem due to recent climate warming in the Anthropocene. We assess other palaeolimnological studies to infer the spatiotemporal pattern of the HTM and affirm that the timing of its onset, a difference of up to 3,000 years from north to south, can be well explained by climatic teleconnections. The westerlies brought cold air to this part of Siberia until the Laurentide ice-sheet vanished 7,000 years ago. The apparent delayed ending of the HTM in the central Siberian record can be ascribed to the exceedance of ecological thresholds trailing behind increases in winter temperatures and decreases in contrast in insolation between seasons during the mid to late Holocene as well as lacking differentiation between summer and winter trends in paleolimnological reconstructions.

Pliocene-Plistocene deposition of carbonate and organic carbon in ODP Hole 159-959C

During Ocean Drilling Program (ODP) Leg 159, four sites (Sites 959-962) were drilled along a depth transect on the Côte d'Ivoire/Ghana Transform Margin. In this study, the Pliocene-Pleistocene history of carbonate and organic carbon accumulation at Hole 959C is reconstructed for the eastern equatorial Atlantic off the Ivory Coast/Ghana based on bulk carbonate, sand fraction, organic carbon, and other organic geochemical records (d13Corg, marine organic matter percentages derived from organic petrology, hydrogen index, C/N). Pliocene-Pleistocene sedimentation off the Ivory Coast/Ghana was strongly affected by low mean sedimentation rates, which are attributed to persistently enhanced bottom-water velocities related to the steep topography of the transform margin. Sand fraction and bulk carbonate records reveal typical glacial/interglacial cycles, preserved, however, with low time resolution. Intermediate carbonate accumulation rates observed throughout the Pliocene-Pleistocene suggest intense winnowing and sediment redistribution superimposed by terrigenous dilution. 'Atlantic-type' sand and carbonate cycles, consistent with records from pelagic areas of the eastern equatorial Atlantic, are encountered at Hole 959C prior to about 0.9 Ma. Total organic carbon (TOC) records are frequently inversely correlated to carbonate contents, indicating mainly productivity-driven carbonate dissolution related to changes in paleoproductivity. During Stages 22-24, 20, 16, 12, 8, and 4, sand and carbonate records reveal a 'Pacific-type' pattern, showing elevated contents during glacials commonly in conjunction with enhanced TOC records. Formation of 'Pacific-type' patterns off the Ivory Coast/Ghana is attributed to drastically increased bottom-water intensities along the transform margin in accordance with results reported from the Walvis Ridge area. Short-term glacial/interglacial changes in paleoproductivity off the Ivory Coast/Ghana are to some extend recognizable during glacials prior to 1.7 Ma and interglacial Stages 21, 19, 13, 9, and 1. Enhanced coastal upwelling during interglacials is attributed to local paleoclimatic and oceanographic conditions off the Ivory Coast/Ghana. Quantitative estimates of marine organic carbon based on organic petrologic and d13Corg records reveal an offset in concentration ranging from 15% to 60%. Highest variabilities of both records are recorded since ~0.9 Ma. Discrepancies between the isotopic and microscopic records are attributed to an admixture of C4 plant debris approaching the eastern equatorial Atlantic via atmospheric dust. Terrestrial organic material likely originated from the grass-savannah-covered Sahel zone in central Africa. Estimated C4 plant concentrations and accumulation rates range from 10% to 37% and from almost zero to 0.006 g/cm**2/k.y., respectively. The strongest eolian supply to the northern Gulf of Guinea is indicated between 1.9 and 1.68 Ma and during glacial isotopic Stages 22-24, 20, 14, and 12. The presence of grass-type plant debris is further supported by organic petrologic studies, which reveal well-preserved cell tissues of vascular plants or tube-shaped, elongated terrestrial macerals showing different levels of oxidation.

Sand fraction, carbonate and organic carbon contents of ODP Hole 175-1085A

Site 1085 is located on the continental rise of southwest Africa at a water depth of 1713 m off the mouth of the Orange River in the Cape Basin. The site is part of the suite of locations drilled during Leg 175 on the Africa margin to reconstruct the onset and evolution of the elevated biological productivity associated with the Benguela Current upwelling system (Wefer, Berger, Richter, et al., 1998, doi:10.2973/odp.proc.ir.175.1998). Three sediment samples were collected per section from Cores 170-1085A-28H through 45X (251-419 mbsf) to provide a survey of the sediment record of paleoproductivity from the middle late Miocene to the early Pliocene (~8.7-4.7 Ma), which is a period that includes the postulated northward migration and intensification of the Benguela Current and the establishment of modern circulation off southwest Africa (Siesser, 1980; Diester-Haass et al., 1992; Berger et al., 1998). Core 170-1085A-30H (270-279 mbsf) had essentially no recovery; this coring gap was filled with samples from Cores 170-1085B-29H and 30H (261-280 mbsf). The results of measurements of multiple paleoproductivity proxies are summarized in this report. Included in these proxies are the radiolarian, foraminiferal, and echinoderm components of the sand-sized sediment fraction. Opal skeletons of radiolarians (no diatoms were found) relate to paleoproductivity and water mass chemistry (Summerhayes et al., 1995, doi:10.1016/0079-6611(95)00008-5; Lange and Berger, 1993, doi:10.2973/odp.proc.sr.130.011.1993; Nelson et al., 1995, doi:10.1029/95GB01070). The accumulation rates of benthic foraminifers are useful proxies for paleoproductivity (Herguera and Berger, 1991, doi:10.1130/0091-7613(1991)019<1173:PFBFAG>2.3.CO;2; Nees, 1997, doi:10.1016/S0031-0182(97)00012-6; Schmiedl and Mackensen, 1997, doi:10.1016/S0031-0182(96)00137-X) because these fauna subsist on organic matter exported from the photic zone. Echinoderms also depend mainly on food supply from the photic zone (Gooday and Turley, 1990), and their accumulation rates are an additional paleoproductivity proxy. Concentrations of calcium carbonate (CaCO3) and organic carbon in sediment samples are fundamental measures of paleoproductivity (e.g., Meyers, 1997, doi:10.1016/S0146-6380(97)00049-1). In addition, organic matter atomic carbon/nitrogen (C/N) ratios and delta13C values can be used to infer the origin of the organic matter contained within the sediments and to explore some of the factors affecting its preservation and accumulation (Meyers, 1994, doi:10.1016/0009-2541(94)90059-0).