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  • 1.
    McGivney, Eric
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap.
    Cederholm, Linnea
    Barth, Andreas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för biokemi och biofysik.
    Hakkarainen, Minna
    Hamacher-Barth, Evelyne
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för biokemi och biofysik.
    Ogonowski, Martin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap.
    Gorokhova, Elena
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap.
    Rapid Physicochemical Changes in Microplastic Induced by Biofilm Formation2020Ingår i: Frontiers in Bioengineering and Biotechnology, E-ISSN 2296-4185, Vol. 8, artikel-id 205Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Risk assessment of microplastic (MP) pollution requires understanding biodegradation processes and related changes in polymer properties. In the environment, there are two-way interactions between the MP properties and biofilm communities: (i) microorganisms may prefer some surfaces, and (ii) MP surface properties change during the colonization and weathering. In a 2-week experiment, we studied these interactions using three model plastic beads (polyethylene [PE], polypropylene [PP], and polystyrene [PS]) exposed to ambient bacterioplankton assemblage from the Baltic Sea; the control beads were exposed to bacteria-free water. For each polymer, the physicochemical properties (compression, crystallinity, surface chemistry, hydrophobicity, and surface topography) were compared before and after exposure under controlled laboratory conditions. Furthermore, we characterized the bacterial communities on the MP surfaces using 16S rRNA gene sequencing and correlated community diversity to the physicochemical properties of the MP. Significant changes in PE crystallinity, PP stiffness, and PS maximum compression were observed as a result of exposure to bacteria. Moreover, there were significant correlations between bacterial diversity and some physicochemical characteristics (crystallinity, stiffness, and surface roughness). These changes coincided with variation in the relative abundance of unique OTUs, mostly related to the PE samples having significantly higher contribution of Sphingobium, Novosphingobium, and uncultured Planctomycetaceae compared to the other test materials, whereas PP and PS samples had significantly higher abundance of Sphingobacteriales and Alphaproteobacteria, indicating possible involvement of these taxa in the initial biodegradation steps. Our findings demonstrate measurable signs of MP weathering under short-term exposure to environmentally relevant microbial communities at conditions resembling those in the water column. A systematic approach for the characterization of the biodegrading capacity in different systems will improve the risk assessment of plastic litter in aquatic environments.

  • 2.
    McGivney, Eric
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap och analytisk kemi. Carnegie Mellon University, United States.
    Gao, Xiaoyu
    Liu, Yijing
    Lowry, Gregory V.
    Casman, Elizabeth
    Gregory, Kelvin B.
    VanBriesen, Jeanne M.
    Avellan, Astrid
    Biogenic Cyanide Production Promotes Dissolution of Gold Nanoparticles in Soil2019Ingår i: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 53, nr 3, s. 1287-1295Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Gold nanoparticles (Au NPs) are often used to study the physiochemical behavior and distribution of nanomaterials in natural systems because they are assumed to be inert under environmental conditions, even though Au can be oxidized and dissolved by a common environmental compound: cyanide. We used the cyanogenic soil bacterium, Chromobacterium violaceum, to demonstrate that quorum-sensing-regulated cyanide production could lead to a high rate of oxidative dissolution of Au NPs in soil. After 7 days of incubation in a pH 7.0 soil inoculated with C. violaceum, labile Au concentration increased from 0 to 15%. There was no observable dissolution when Au NPs were incubated in abiotic soil. In the same soil adjusted to pH 7.5, labile Au concentration increased up to 29% over the same time frame. Furthermore, we demonstrated that Au dissolution required quorum-sensing-regulated cyanide production in soil by inoculating the soil with different cell densities and using a quorum-sensing-deficient mutant of C. violaceum, CV026. Au NP dissolution experiments in liquid media coupled with mass spectrometry analysis confirmed that biogenic cyanide oxidized Au NPs to soluble Au(CN)(2)(-). These results demonstrate under which conditions biologically enhanced metal dissolution can contribute to the overall geochemical transformation kinetics of nanoparticle in soils, even though the materials may be inert in abiotic environments.

  • 3.
    McGivney, Eric
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap och analytisk kemi. KTH Royal Institute of Technology, Sweden.
    Gustafsson, Jon Petter
    Belyazid, Salim
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för naturgeografi.
    Zetterberg, Therese
    Löfgren, Stefan
    Assessing the impact of acid rain and forest harvest intensity with the HD-MINTEQ model - soil chemistry of three Swedish conifer sites from 1880 to 20802019Ingår i: soil, ISSN 2199-3971, Vol. 5, nr 1, s. 63-77Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Forest soils are susceptible to anthropogenic acidification. In the past, acid rain was a major contributor to soil acidification, but, now that atmospheric levels of S have dramatically declined, concern has shifted towards biomass-induced acidification, i.e. decreasing soil solution pH due to tree growth and harvesting events that permanently remove base cations (BCs) from forest stands. We use a novel dynamic model, HD-MINTEQ (Husby Dynamic MINTEQ), to investigate possible long-term impacts of two theoretical future harvesting scenarios in the year 2020, a conventional harvest (CH, which removes stems only), and a whole-tree harvest (WTH, which removes 100 % of the above-ground biomass except for stumps) on soil chemistry and weathering rates at three different Swedish forest sites (Aneboda, Gardsjon, and Kindla). Furthermore, acidification following the harvesting events is compared to the historical acidification that took place during the 20th century due to acid rain. Our results show that historical acidification due to acid rain had a larger impact on pore water chemistry and mineral weathering than tree growth and harvesting, at least if nitrification remained at a low level. However, compared to a no-harvest baseline, WTH and CH significantly impacted soil chemistry. Directly after a harvesting event (CH or WTH), the soil solution pH sharply increased for 5 to 10 years before slowly declining over the remainder of the simulation (until year 2080). WTH acidified soils slightly more than CH, but in certain soil horizons there was practically no difference by the year 2080. Even though the pH in the WTH and CH scenario decreased with time as compared to the no-harvest scenario (NH), they did not drop to the levels observed around the peak of historic acidification (1980-1990), indicating that the pH decrease due to tree growth and harvesting would be less impactful than that of historic atmospheric acidification. Weathering rates differed across locations and horizons in response to historic acidification. In general, the predicted changes in weathering rates were very small, which can be explained by the net effect of decreased pH and increased Al3+, which affected the weathering rate in opposite ways Similarly, weathering rates after the harvesting scenarios in 2020 remained largely unchanged according to the model.

  • 4. Rosenstock, Nicholas P.
    et al.
    Stendahl, Johan
    van der Heijden, Gregory Alexander
    Lundin, Lars
    Mcgivney, Eric
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för miljövetenskap och analytisk kemi.
    Bishop, Kevin
    Löfgren, Stefan
    Base cations in the soil bank: non-exchangeable pools may sustain centuries of net loss to forestry and leaching2019Ingår i: Soil, ISSN 2199-3971, Vol. 5, nr 2, s. 351-366Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Accurately quantifying soil base cation pool sizes is essential to interpreting the sustainability of forest harvests from element mass-balance studies. The soil-exchangeable pool is classically viewed as the bank of available base cations in the soil, withdrawn upon by plant uptake and leaching and refilled by litter decomposition, atmospheric deposition and mineral weathering. The operational definition of this soil bank as the exchangeable (salt-extractable) pools ignores the potential role of other soil nutrient pools, including microbial biomass, clay interlayer absorbed elements, and calcium oxalate. These pools can be large relative to exchangeable pools. Thus neglecting these other pools in studies examining the sustainability of biomass extractions, or need for nutrient return, limits our ability to gauge the threat or risk of unsustainable biomass removals. We examine a set of chemical extraction data from a mature Norway spruce forest in central Sweden and compare this dataset to ecosystem flux data gathered from the site in previous research. The 0.2 M HCl extraction released large pools of Ca, K, Mg, and Na, considerably larger than the exchangeable pools. Where net losses of base cations are predicted from biomass harvest, exchangeable pools may not be sufficient to support more than a single 65-year forest rotation, but acid-extractable pools are sufficient to support many rotations of net-ecosystem losses. We examine elemental ratios, soil clay and carbon contents, and pool depth trends to identify the likely origin of the HCl-extractable pool. No single candidate compound class emerges, as very strongly supported by the data, as being the major constituent of the HCl-extractable fraction. A combination of microbial biomass, fine grain, potentially shielded, easily weatherable minerals, and non-structural clay interlayer bound potassium may explain the size and distribution of the acid-extractable base cation pool. Sequential extraction techniques and isotope-exchange measurements should be further developed and, if possible, complemented with spectroscopic techniques to illuminate the identity of and flux rates through these important, and commonly overlooked, nutrient pools.

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