Deciphering the Role of Water Column Redoxclines on Methyl mercury Cycling Using Speciation Modeling and Observations From the Baltic Sea

A.L. Soerensen; A.T. Schartup; A. Skrobonja; S. Bouchet; D. Amouroux; V. Liem-Nguyen; E. Björn
2018 | Global Biogeochem Cycles | 32

Oxygen-depleted areas are spreading in coastal and offshore waters worldwide, but the implication for production and bioaccumulation of neurotoxic methylmercury (MeHg) is uncertain. We combined observations from six cruises in the Baltic Sea with speciation modeling and incubation experiments to gain insights into mercury (Hg) dynamics in oxygen depleted systems. We then developed a conceptual model describing the main drivers of Hg speciation, fluxes, and transformations in water columns with steep redox gradients. MeHg concentrations were 2–6 and 30–55 times higher in hypoxic and anoxic than in normoxic water, respectively, while only 1–3 and 1–2 times higher for total Hg (THg). We systematically detected divalent inorganic Hg (HgII) methylation in anoxic water but rarely in other waters. In anoxic water, high concentrations of dissolved sulfide cause formation of dissolved species of HgII: HgS2H-(aq) and Hg (SH)20(aq) . This prolongs the lifetime and increases the reservoir of HgII readily available for
methylation, driving the high MeHg concentrations in anoxic zones. In the hypoxic zone and at the hypoxic-anoxic interface, Hg concentrations, partitioning, and speciation are all highly dynamic due to processes linked to the iron and sulfur cycles. This causes a large variability in bioavailability of Hg, and thereby MeHg concentrations, in these zones. We find that zooplankton in the summertime are exposed to 2–6 times higher MeHg concentrations in hypoxic than in normoxic water. The current spread of hypoxic zones in coastal systems worldwide could thus cause an increase in the MeHg exposure of food webs.

Reviews and syntheses: Carbon use efficiency from organisms to ecosystems – definitions, theories, and empirical evidence

Manzoni, S.; Capek, P., Porada, P.; Thurner, M.; Winterdahl, M.; Beer, C.; Brüchert, V.; Frouz, J.; Hermann, A.M.; Lindahl, B.D.; Lyon, S.W.; Santruckova, H.; Vico, G.; Way, D.
2018 | Biogeosciences | 15 (5929-5949)

The cycling of carbon (C) between the Earth surface and the atmosphere is controlled by biological and abiotic processes that regulate C storage in biogeochemical compartments and release to the atmosphere. This partitioning is quantified using various forms of C-use efficiency (CUE) – the ratio of C remaining in a system to C entering that system. Biological CUE is the fraction of C taken up allocated to biosynthesis. In soils and sediments, C storage depends also on abiotic processes, so the term C-storage efficiency (CSE) can be used. Here we first review and reconcile CUE and CSE definitions proposed for autotrophic and heterotrophic organisms and communities, food webs, whole ecosystems and watersheds, and soils and sediments using a common mathematical framework. Second, we identify general CUE patterns; for example, the actual CUE increases with improving growth conditions, and apparent CUE decreases with increasing turnover. We then synthesize >5000CUE estimates showing that CUE decreases with increasing biological and ecological organization – from unicellular to multicellular organisms and from individuals to ecosystems. We conclude that CUE is an emergent property of coupled biological–abiotic systems, and it should be regarded as a flexible and scale-dependent index of the capacity of a given system to effectively retain C.

Longitudinal trends of per- and polyfluoroalkyl substances in children’s serum

Koponen, K.; Winkens, K.; Airaksinen, R.; Berger, U.; Vestergren, R.; Cousins, I.T.; Karvonen, A.; Pekkanen, J.; Kiviranta, H.
2018 | Environ Int | 121 (591-599)

A plant-microbe interaction framework explaining nutrient effects on primary production

Čapek P.; Manzoni S.; Kaštovská E.; Wild B.; Diáková K.; Bárta J.; Schnecker J.; Biasi C.; Martikainen P.J.; Alves R.J.E.; Guggenberger G.; Gentsch N.; Hugelius G.; Palmtag J.; Mikutta R.; Shibistova O.; Urich T.; Schleper C.; Richter A.; Šantrůčková H.
2018 | Nat. Ecol. Evol | 2 (1588-1596)

Evaluating the current situation of PFAS in Lake Mälaren, Stockholm – distribution of PFAS in water column, surface sediment and sediment cores

Filipovic, M.; Kärrman, A.; Benskin, J.; Cousins, I.T.; Edvinsson, J.; Karlsson, E.; Neuschütz, C.; Holmström, S.; Holmström, K.; Temnerud, J.; Iverfelt, U.
2018 | SU

Nordrocs 2018: 7th joint Nordic meeting on remediation of contaminated sites | September 4, 2018 | Helsingör, Denmark

Resistance of soil protein depolymerization rates to eight years of elevated CO2, warming, and summer drought in a temperate heathland

Wild B.; Ambus P.; Reinsch S.; Richter A.
2018 | Biogeochemistry | 140 (255-267)

Zürich Statement on Future Actions on Per-and Polyfluoroalkyl Substances (PFASs)

Ritscher, A.; Wang, Z.; Scheringer, M.; Boucher, J.M.; Ahrens, L.; Berger, U.; Bintein, S.; Bopp, S.K.; Borg, D.; Buser, A.M.; Cousins, I.T.; DeWitt, J.; Fletcher, T.; Green, C.; Herzke, D.; Higgins, C.; Huang, J.; Hung, H.; Knepper, T.; Lau, C.S.; Leinala, E.; Lindstrom, A.B.; Liu, J.; Miller, M.; Ohno, K.; Perkola, N.; Shi, Y.; Haug, L.S., Trier, X.; Valsecchi, S.; van der Jagt, K.; Vierke, L.
2018 | Environ. Health Perspect. | 126 (8) (084502-1-084502-5)

Temperature response of permafrost soil carbon is attenuated by mineral protection

Gentsch N.; Wild B.; Mikutta R.; Čapek P.; Diáková K.; Schrumpf M.; Turner S.; Minnich C.; Schaarschmidt F.; Shibistova O.; Schnecker J.; Urich T.; Gittel A.; Šantrůčková H.; Bárta J.; Lashchinskiy N.; Fuß R.; Richter A.; Guggenberger G.
2018 | Glob. Change Biol. | 24 (3401-3415)

Sulfluramid use in Brazilian agriculture: A source of per- and polyfluoroalkyl substances (PFASs) to the environment

Rodrigo A Nascimento; Deborah BO Nunoo; Ekhine Bizkarguenaga; Lara Schultes; Itsaso Zabaleta; Jonathan P. Benskin; Saulo Spanó; Juliana Leonel
2018 | Environ. Pollut. | In Press

Uncertainty quantification of extratropical forest biomass in CMIP5 models over the Northern Hemisphere

Yang, C.-E.; Mao, J.; Hoffman, F.M.; Ricciuto, D.M.; Fu, J.S.; Jones, C.D.; Thurner, M.
2018 | Sci Rep | 8 (10962)

Simplified representations of processes influencing forest biomass in Earth system models (ESMs) contribute to large uncertainty in projections. We evaluate forest biomass from eight ESMs outputs archived in the Coupled Model Intercomparison Project Phase 5 (CMIP5) using the biomass data synthesized from radar remote sensing and ground-based observations across northern extratropical latitudes. ESMs exhibit large biases in the forest distribution, forest fraction, and mass of carbon pools that contribute to uncertainty in forest total biomass (biases range from −20 Pg C to 135 Pg C). Forest total biomass is primarily positively correlated with precipitation variations, with surface temperature becoming equally important at higher latitudes, in both simulations and observations. Relatively small differences in forest biomass between the pre-industrial period and the contemporary period indicate uncertainties in forest biomass were introduced in the pre-industrial model equilibration (spin-up), suggesting parametric or structural model differences are a larger source of uncertainty than differences in transient responses. Our findings emphasize the importance of improved (1) models of carbon allocation to biomass compartments, (2) distribution of vegetation types in models, and (3) reproduction of pre-industrial vegetation conditions, in order to reduce the uncertainty in forest biomass simulated by ESMs.

Perfluoroalkyl acids and their precursors in floor dust of children’s bedrooms – Implications for indoor exposure

Winkens, K.; Giovanoulis, G.; Koponen, J.; Vestergren, R.; Berger, U.; Karvonen, A.M.; Pekkanen, J.; Kiviranta, H.; Cousins, I.T.
2018 | Environ Int | 119 (493-502)

Polychlorinated biphenyls (PCBs) as sentinels for the elucidation of Arctic environmental change processes: a comprehensive review combined with ArcRisk project results

Carlsson, P.; Breivik, K.; Brorström-Lundén, E.; Cousins, I.T.; Christensen, J.; Grimalt, J.O.; Halsall, C.; Kallenborn, R.; Abass, K.; Lammel, G.; Munthe, J.; MacLeod, M.; Øyvind, J-O.; Pawlak, J.; Rautio, A.; Reiersen, L-O., Schlabach, M.; Stemmler, I.; Wilson, S.; Wöhrnschimmel, H.
2018 | Environ Sci Pollut Res | 25 (23) (22499-22528)

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