C02_01

Radiocarbon measurements on soot particles preserved in sediments illustrate past fossil fuel usage history in China

Dusek U¹,  Tang Y², N. Waters C⁴, Schneider T⁵, Yao P¹, Han Y^2,3

¹Centre for Isotope Reserach, University Of Groningen, Groningen, Netherlands, ²Institute of Earth Environment and Center for Excellence in Quaternary Science and Global Change, Chinese Academy of Sciences, Xi'an, China, ³Jiaotong University, Xi'an, China, ⁴University of Leicester, Leicester, United Kingdom, ⁵Columia University, New York, USA

Fossil fuel (FF) combustion accounts for a large, but uncertain, amount of elemental carbon (EC) in the atmosphere, where EC plays an important role in climate warming and adversely affects human health. However, historical estimates of FF contributions to air pollution are limited by uncertainties in fuel usage and emission factors. Here, we developed a novel radiocarbon method specifically applied to sedimentary soot, defined as the most refractory part of EC. The method was based on a two-step thermal protocol for isolating EC from atmospheric aerosol samples. Then, we constrained FF-soot emissions from southeastern China over the past 110 years using a sediment core from a maar lake. For this lake, exogenic material such as soot, originates almost entirely from atmospheric deposition.

The reconstructed soot accumulations reflect the integrated effects of increased fossil fuel use caused by economic development and reductions in emissions due to pollution controls. A sharp increase in FF-soot started at 1950 as southeastern China industrialized and developed economically, but both the percentage and the fluxes of FF-soot fraction decreased over the past decade, confirming the efficiency of pollution controls on the reduction of soot emissions. We compare FF-soot history to changes in CO₂ emissions, industrial and economic activities, and pollution controls and show that FF-soot fluxes are more readily controlled than atmospheric CO₂. Our independent FF-soot record provides insights into the effects of economic development and controls on air pollution and the environmental impacts from the changes in soot emissions.

C02_02

Using radiocarbon in tree rings to track nuclear power plant emissions and fossil fuel contributions in Ontario, Canada

Martin D¹,  Pisaric M², Crann C³, Vogel F⁴

¹Department of Biological Sciences, Brock University, St. Catharines, Canada, ²Department of Geography and Tourism Studies, Brock University, St. Catharines, Canada, ³AEL-AMS Laboratory, University of Ottawa, Ottawa, Canada, ⁴Climate and Research Division, Environment and Climate Change Canada, Toronto, Canada

The atmospheric radiocarbon (¹⁴C) signature can help inform atmospheric carbon inventories for environmental monitoring and observing anthropogenic atmospheric carbon-source impacts as it is influenced by global-scale inputs (e.g., natural ¹⁴C production, the industrial revolution, nuclear weapons testing) and local inputs (e.g., nuclear power plants, urban centres). In this study, we measure Δ¹⁴C in tree rings to look at the history of anthropogenic carbon dioxide (CO₂) contributions from local emission sources in Southern Ontario that either contribute ¹⁴C (e.g., nuclear power) or ¹², ¹³C (e.g., burning of fossil fuels). Ontario’s energy portfolio includes 50% nuclear power produced using Canadian Deuterium (CANDU) reactors and includes the world’s largest nuclear power station: Bruce Nuclear Generating Station (BNGS). Results from tree ring Δ¹⁴C near Bruce show an enrichment in ¹⁴C compared to background and a correlation with emissions data from Bruce Nuclear. Since the BNGS is 200 km upwind of the Greater Toronto Area (population > 6.3 million), it is important to consider the magnitude of the ¹⁴C signature across space and time when studying the Δ¹⁴C signature in the urban area of the Greater Toronto Area (GTA).  Depleted Δ¹⁴C signatures (relative to clean air measurements at Jungfraujoch, CH, and Egbert, ON) in tree ring and atmospheric Δ¹⁴C measurements in the GTA largely reflect urban sprawl over the past 30 years, but also tell the story of COVID-19 lockdowns in March 2020 when there was less population mobility and subsequent declines in ¹⁴C-depleted atmospheric CO₂ concentrations due to less fossil fuel consumption.

C02_03

Radiocarbon Inventories of Switzerland: Spatial Radiocarbon Signatures of Carbon exported by Swiss Rivers

Rhyner T¹,  Haghipour N¹, Bröder L¹, Eglinton T¹

¹ETH, Zurich, Switzerland

In the Anthropocene, there is the need to investigate changes in the nature of carbon within the biosphere, hydrosphere, atmosphere, geosphere and the connection between them. The RICH-project (Radiocarbon Inventories of Switzerland), is a world premiere in constructing a first national-scale census of carbon across aquatic, terrestrial, and atmospheric reservoirs. Within the global carbon cycle, inland waters play a crucial role, where rivers act as principal connectors between different carbon reservoirs. However, there is still limited understanding of the drivers that control carbon mobilization and mineralization in rivers. This project will establish radiocarbon inventories of dissolved and particulate carbon phases across major river systems of Switzerland. In many cases, the inputs of C to a reservoir can derive from multiple sources, where radiocarbon has been used in combination with ¹³C to disentangle a C mixture into its source components of modern, pre-aged, or fossil carbon. This can be used to estimate the relative contributions of individual sources with different ¹⁴C-signatures to a given system. Combining emergent ecosystem properties across the five ecoregions of Switzerland, there will be the notion of a radiocarbon compilation to develop an integrated perspective on carbon cycling on a national scale. A field sampling campaign in 2021 revealed spatial variability in radiocarbon content, where riverine Δ¹⁴C ranged from -477 ‰ to 58 ‰. These data form the foundation for future in-depth investigations using ¹⁴C measurements on compound-specific biomarkers to constrain the temporal dynamics and transport pathways of biospheric carbon.

C02_P01

Carbon Isotope Changes Through the Recent Past: F¹⁴C and δ¹³C values in single barley grain from 1852 to 2020

Dunbar E¹,  Scott M², Tripney B¹, Addis H³

¹SUERC, University of Glasgow, Glasgow, UK, ²University of Glasgow, Glasgow, UK, ³Rothamsted Research, Hertfordshire, UK

Annual records are gaining increasing prominence, whether in the form of tree rings (with their growing importance in IntCal) and other reservoirs, or from the more recent past, such as grain with a single known year of growth.  Such annual F¹⁴C and δ¹³C data from the past 60 years has proven a useful tool in the study of both environmental processes and in forensic science, generating “bomb F¹⁴C curves”.

Presented here are F¹⁴C and ancillary δ¹³C values on barley grain (Hordeum vulgare L. spring barley) covering the period 1852 to 2021, collected from the sample archive of the Long-Term Experiments (LTEs) Hoosfield Spring Barley at Rothamsted Research (Hertfordshire, UK) – the oldest agricultural research station in the world, founded in 1843.

The barley grain data is presented alongside data from barley mash samples which have formed a part of several intercomparison studies undertaken in the past 30 years.  Together, these data add value to the post bomb F¹⁴C curves. Furthermore, it is now evident that recent F¹⁴C values for grain are approaching the nominal activity of an 1890 wood (F¹⁴C value of 1), raising the questions: When will the F¹⁴C value decrease below 1? Will this cause difficulties in establishing whether a sample derives from the pre- or post-nuclear era?

C02_P02

Radiocarbon Concentration Measurements in Tree Leaves near SOCOCIM (Rufisque, Senegal), A Cement Factory

NDEYE M¹

¹Laboratoire Carbone 14, Dakar, Senegal

Radiocarbon content in biogenic samples is widely used to study the variation of atmospheric CO₂ due to anthropogenic activities. A total of 20 samples of several types of tree leaves, were analyzed for this study. Sampling was carried out at the end of the rainy season in 2017 from the surrounding of the SOCOCIM cement factory in Rufisque town. Rufisque is located on the peninsula of Cape Verde, 25 km east of Dakar, where it is the «south gate» of the agglomeration. Reference samples of five different species were collected during the same period (2017) from a clean zone. The ¹⁴C method was used for the determination of Δ¹⁴C values. The data show that the ¹⁴C concentration in the studied sites was significantly lower than the clean area, due to the release of anthropogenic CO₂. To estimate the Suess effect, the fossil fuel fraction was determined based on equations of mass balance for CO₂ concentration, stable isotopic composition of carbon, and ¹⁴C concentration. The results show that selected locations are affected differently according to their distance from the factory and the wind direction.

Keywords :  Radiocarbon Concentration, Fossil Fuel Fraction, Tree Leaves, Cement  Factory

C02_P03

Influence of the human activity on the source of soil inorganic carbon in grassland from Tibet and Inner Mongolia

Ping D^1,2,  Yiwei C^1,2, Sanyuan Z^1,3, Chengde S^1,2, Ning W^1,2

¹State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China, ²CAS Center for Excellence in Deep Earth Science, Guangzhou, China, ³State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China

Soil Inorganic carbon (SIC) in two Alpine Meadow soil profiles from Tibet (Nam Co, 30°46´12″ N, 90°57´13″ E, amsl. 4737 m & Dangxiong, 30°22´40″ N, 90°55´45″ E, amsl. 4294 m) and two grassland soil profiles from Inner Mongolia (DXC, 43°00'25″ N，117°29´43″ E, amsl. 1352 m & GYC, 43°34'32″ N, 116°40'16″ E, amsl. 1225 m) were investigated. ¹⁴C ages of soil organic carbon (SOC) and SIC in Tibet show a significant positive correlation (Nam Co, R2=0.95 & Dangxiong, R2=0.94) between each other, suggesting a stable contribution of SOC to the SIC since 4.0 – 5.0 ka. Shrink of Nam Co lake at 3.0 – 2.0 ka and weakening of summer monsoon precipitation likely played little influence on the source of SIC in Tibet since  mid-Holocene. For comparison, ¹⁴C ages of SOC and SIC in Inner Mongolia indicate an obviously positive correlation (DXC, R2=0.97 & GYC, R2=0.91) from 4.0 – 5.0 ka to 2.0 ka, and almost a stable ¹⁴C age of SIC after 2.0 ka, reflecting a different source of soil IC after 2.0 ka in Inner Mongolia grassland. Variation of monsoon precipitation from 4.2 to 2.1 ka seems did not change the correlation obviously during that time in Inner Mongolia. Intensive human activities, such as farming and grazing since 2.0 ka in Inner Mongolia, likely led to the deterioration of the grassland and then the deflation of deeper soil layers, which finally changed the source of SIC in the shallow layers.