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Based on photoionisation mass spectrometry two types of experiments were carried out. (i) In a fast flow reactor coupled to a low pressure flame as a particle source, rate coefficients for the coagulation of primary nanoparticles were measured through variation of the reactor residence time. The results are kc (350 K) = 3.5 ⋅ 10-10 cm³/s and kc (573 K) = 1.1 ⋅ 10-9 cm³/s, i.e. very high rate coefficients. It was also shown that coagulated nanoparticles can have masses beyond 50 ku, corresponding to equivalent diameters between 4 to 5 nm. These particles are easily fragmented during photoionisation. (ii) Using a second and mobile photoionisation mass spectrometer equipped with a fast flow inlet system, measurements were carried out behind three different vehicle engines, a two-stroke scooter engine, a four-stroke motorbike engine and a DI (direct injection) gasoline research engine. In all cases ion signals around 1000 u were found that are clearly dependent on engine conditions. In the case of the DI engine, they correlate with the smoke number. These signals cannot be explained by PAHs due to their low volatility at the respective masses. Major contributions of soot or droplet fragmentation were ruled out through additional experiments using a heated inlet line and a filter. Consequently, these signals are interpreted as fragments of coagulated nanoparticles. [ABSTRACT FROM AUTHOR]

The changes in atmospheric pCO 2 provide evidence for the release of large amounts of ancient carbon during the last deglaciation. However, the sources and mechanisms that contributed to this process remain unresolved. Here, we present evidence for substantial ancient terrestrial carbon remobilization in the Canadian Arctic following the Laurentide Ice Sheet retreat. Glacial-retreat-induced physical erosion of bedrock has mobilized petrogenic carbon, as revealed by sedimentary records of radiocarbon dates and thermal maturity of organic carbon from the Canadian Beaufort Sea. Additionally, coastal erosion during the meltwater pulses 1a and 1b has remobilized pre-aged carbon from permafrost. Assuming extensive petrogenic organic carbon oxidation during the glacial retreat, a model-based assessment suggests that the combined processes have contributed 12 ppm to the deglacial CO 2 rise. Our findings suggest potentially positive climate feedback of ice-sheet retreat by accelerating terrestrial organic carbon remobilization and subsequent oxidation during the glacial-interglacial transition., (© 2022. The Author(s).)

Persistent cold temperatures, a paucity of nutrients, freeze-thaw cycles, and the strongly seasonal light regime make Antarctica one of Earth's least hospitable surface environments for complex life. Cyanobacteria, however, are well-adapted to such conditions and are often the dominant primary producers in Antarctic inland water environments. In particular, the network of meltwater ponds on the 'dirty ice' of the McMurdo Ice Shelf is an ecosystem with extensive cyanobacteria-dominated microbial mat accumulations. This study investigated intact polar lipids (IPLs), heterocyte glycolipids (HGs), and bacteriohopanepolyols (BHPs) in combination with 16S and 18S rRNA gene diversity in microbial mats of twelve ponds in this unique polar ecosystem. To constrain the effects of nutrient availability, temperature and freeze-thaw cycles on the lipid membrane composition, lipids were compared to stromatolite-forming cyanobacterial mats from ice-covered lakes in the McMurdo Dry Valleys as well as from (sub)tropical regions and hot springs. The 16S rRNA gene compositions of the McMurdo Ice Shelf mats confirm the dominance of Cyanobacteria and Proteobacteria while the 18S rRNA gene composition indicates the presence of Ochrophyta, Chlorophyta, Ciliophora, and other microfauna. IPL analyses revealed a predominantly bacterial community in the meltwater ponds, with archaeal lipids being barely detectable. IPLs are dominated by glycolipids and phospholipids, followed by aminolipids. The high abundance of sugar-bound lipids accords with a predominance of cyanobacterial primary producers. The phosphate-limited samples from the (sub)tropical, hot spring, and Lake Vanda sites revealed a higher abundance of aminolipids compared to those of the nitrogen-limited meltwater ponds, affirming the direct affects that N and P availability have on IPL compositions. The high abundance of polyunsaturated IPLs in the Antarctic microbial mats suggests that these lipids provide an important mechanism to maintain membrane fluidity in cold environments. High abundances of HG keto-ols and HG keto-diols, produced by heterocytous cyanobacteria, further support these findings and reveal a unique distribution compared to those from warmer climates., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Evans, Kalambokidis, Jungblut, Millar, Bauersachs, Grotheer, Mackey, Hawes and Summons.)

A resonance enhanced multiphoton ionization (REMPI) mass spectrometer consisting of a tunable laser unit (Nd:YAG pump laser and OPO) and a reflectron mass spectrometer have been upgraded to cope with the difficult conditions such as vibrations, temperature fluctuations and dust, prevailing in an incinerator. On-line measurements of the raw gas have been carried out at the municipal waste incinerator in Stuttgart. Although this test series could not be completed the results are encouraging. They show that wavelength resolution can provide valuable information beyond the one obtainable by fixed frequency REMPI. Examples discussed include separation of interferants to the aniline signal and identification of phenantrene.