Browsing by Subject "organic matter"

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  • Huurtomaa, Satu (Helsingin yliopisto, 2019)
    The Baltic Sea is a vulnerable marine environment and susceptible to pollution. The situation is especially severe in the Gulf of Finland due to a large catchment area compared to the size of the Gulf. The north eastern Gulf of Finland has been described as one of the most contaminated areas of the entire Baltic Sea, with extensive pollution load via river Kymi in the past. Still today, the currents bring contaminants from the eastern part of the Gulf – the Neva estuary and the Bay of Viborg. The concentrations of V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Mo, Cd, Sb, Hg, Pb, Bi and La were studied in the surface sediments and three GEMAX cores. The vertical distribution revealed the temporal change in the metal accumulation. The spike in the Cs concentration, indicating the Chernobyl disaster in 1986, enabled the estimation of the accumulation of studied elements over time. The horizontal distribution maps based on the concentrations in the surface sediments enabled the discovery of the sites with most intense metal accumulation. Correlation coefficients showed the effect of carbon and sediment grain size in the distribution of metals. The comparison of the metal concentrations to the natural background levels and the Canadian sediment quality guidelines (SQGs) enabled the estimation of the degree of contamination of the area. The metal concentrations have declined during the last decades in the north eastern Gulf of Finland, indicating lower contamination input towards present day. However, in the oxidized Ravijoki core, the decline was not that obvious, probably due to metal scavenging by Fe and Mn oxides and bioturbation. The regional metal distribution was strongly affected by the grain size and carbon – most metals showed high positive correlations with carbon and finer sediment fraction. Mn was an exception, showing negative correlations with both carbon and clay, probably due to the Mn reduction at sites with high organic matter accumulation. The regional distribution pattern suggested main Cd pollution arriving from the eastern part of the Gulf. The distribution of Hg, Mo, Cu and Zn also suggested a possible source in the east. High concentrations of Hg, Pb and Cu were discovered in the outlets of river Kymi. According to the Canadian SQGs, the sediments in the north-eastern Gulf of Finland were contaminated. The situation is especially severe in the case of Zn – the higher reference value PEL, above which adverse biological effects frequently occur, was exceeded even in the oxidized Ravijoki sediments. The highest concentrations of the elements with defined SQGs (Cd, Cr, Zn, Cu, Hg, Pb and As) exceeded the lower reference values in the surface sediments, indicating that all these metals could, at least locally, pose a severe threat to benthic species.
  • Nummi, Petri Johannes; Vehkaoja, Mia Christina; Pumpanen, Jukka; Ojala, Anne Kristiina (2018)
    With the recent population increase in beavers (Castor spp.), a considerable amount of new riparian habitat has been created in the Holarctic. We evaluated how beaver‐induced floods affect carbon (C) dynamics in the beaver ponds and in the water‐atmosphere and riparian zone interfaces. Beaver disturbance affects soil organic C storage by decreasing or increasing it, resulting in a redistribution of C. Upon flooding, the concentration of dissolved organic carbon (DOC) increases in the water. This C can be released into the atmosphere, it can settle down to the bottom sediments, it can be sequestered by vegetation, or it can be transported downstream. The carbon dioxide (CO2) emissions vary between 0.14 and 11.2 g CO2 m−2 day−1, averaging 4.9 CO2 g m−2 day−1. The methane (CH4) emissions vary too, from 27 mg m−2 day−1 to 919 mg m−2 day−1, averaging 222 mg CH4 m−2 day−1. Globally, C emission from beaver ponds in the form of CH4 and CO2 may be 3.33–4.62 Tg (teragram, 1012 g) year−1. The yearly short‐term sedimentation rates in beaver ponds vary between 0.4 and 47 cm year−1, and individual ponds contain 9–6355 m3 of sediment. The approximate global estimate for yearly C sedimentation is 3.8 Tg C; beaver ponds globally contain 380 Tg sedimented C. After being formed, beaver pond deposits can remain for millennia. Both C sequestration and CO2 and CH4 emissions in ponds of various ages should be taken into account when considering the net effect of beavers on the C dynamics. With present estimates, beaver ponds globally range from a sink (−0.47 Tg year−1) to a source (0.82 Tg year−1) of C. More research is needed with continuous flux measurements and from ponds of different ages. Likewise, there is a need for more studies in Eurasia to understand the effect of beaver on C biogeochemistry.
  • Kuha, Jonna; Järvinen, Marko; Salmi, Pauliina; Karjalainen, Juha (Springer Link, 2020)
    Hydrobiologia 847 21 (2020)
    Organic matter (OM) other than living phytoplankton is known to affect fluorometric in situ assessments of chlorophyll in lakes. For this reason, calibrating fluorometric measurements for OM error is important. In this study, chlorophyll (Chl) fluores cence was measured in situ in multiple Finnish lakes using two sondes equipped with Chl fluorometers (ex.470/em.650–700 nm). OM absorbance (A420) was measured from water samples, and one of the two sondes was also equipped with in situ fluorometer for OM (ex.350/em.430 nm). The sonde with Chl and OM fluorometers was also deployed continuously on an automated water quality monitoring station on Lake Konnevesi. For data from multiple lakes, inclusion of water colour estimates into the calibration model improved the predictability of Chl assessments markedly. When OM absorbance or in situ OM fluorescence was used in the calibration model, predictability between the in situ Chl and laboratory Chl a assessments was also enhanced. However, correction was not superior to the one done with the water colour estimate. Our results demonstrated that correction with water colour assessments or in situ measurements of OM fluorescence offers practical means to overcome the variation due to OM when assessing Chl in humic lakes in situ.
  • Neumann, Thomas; Koponen, Sampsa; Attila, Jenni; Brockmann, Carsten; Kallio, Kari; Kervinen, Mikko; Mazeran, Constant; Müller, Dagmar; Philipson, Petra; Thulin, Susanne; Väkevä, Sakari; Ylöstalo, Pasi (Copernicus, 2021)
    Geoscientific model development 14: 8, 5049-5062
    Colored dissolved organic matter (CDOM) in marine environments impacts primary production due to its absorption effect on the photosynthetically active radiation. In coastal seas, CDOM originates from terrestrial sources predominantly and causes spatial and temporal changing patterns of light absorption which should be considered in marine biogeochemical models. We propose a model approach in which Earth Observation (EO) products are used to define boundary conditions of CDOM concentrations in an ecosystem model of the Baltic Sea. CDOM concentrations in riverine water derived from EO products serve as forcing for the ecosystem model. For this reason, we introduced an explicit CDOM state variable in the model. We show that the light absorption by CDOM in the model can be improved considerably in comparison to approaches where CDOM is estimated from salinity. The model performance increases especially with respect to spatial CDOM patterns due to the consideration of single river properties. A prerequisite is high-quality CDOM data with sufficiently high spatial resolution which can be provided by the new generation of ESA satellite sensor systems (Sentinel 2 MSI and Sentinel 3 OLCI). Such data are essential, especially when local differences in riverine CDOM concentrations exist.
  • Harju, A. Vilhelmiina; Narhi, Ilkka; Mattsson, Marja; Kerminen, Kaisa; Kontro, Merja H. (2021)
    Views on the entry of organic pollutants into the organic matter (OM) decaying process are divergent, and in part poorly understood. To clarify these interactions, pesticide dissipation was monitored in organic and mineral soils not adapted to contaminants for 241 days; in groundwater sediment slurries adapted to pesticides for 399 days; and in their sterilized counterparts with and without peat (5%) or compost-peat-sand (CPS, 15%) mixture addition. The results showed that simazine, atrazine and terbuthylazine (not sediment slurries) were chemically dissipated in the organic soil, and peat or CPS-amended soils and sediment slurries, but not in the mineral soil or sediment slurries. Hexazinone was chemically dissipated best in the peat amended mineral soil and sediment slurries. In contrast, dichlobenil chemically dissipated in the mineral soil and sediment slurries. The dissipation product 2,6-dichlorobenzamide (BAM) concentrations were lowest in the mineral soil, while dissipation was generally poor regardless of plant-derived OM, only algal agar enhanced its chemical dissipation. Based on sterilized counterparts, only terbutryn appeared to be microbially degraded in the organic soil, i.e., chemical dissipation of pesticides would appear to be utmost important, and could be the first response in the natural cleansing capacity of the environment, during which microbial degradation evolves. Consistent with compound-specific dissipation in the mineral or organic environments, long-term concentrations of pentachloroaniline and hexachlorobenzene were lowest in the mineral-rich soils, while concentrations of dichlorodiphenyltrichloroethane (DTT) and metabolites were lowest in the organic soils of old market gardens. OM amendments changed pesticide dissipation in the mineral soil towards that observed in the organic soil; that is OM accelerated, slowed down or stopped dissipation.
  • Wologo, Ethan; Shakil, Sarah; Zolkos, Scott; Textor, Sadie; Ewing, Stephanie; Klassen, Jane; Spencer, Robert G. M.; Podgorski, David C.; Tank, Suzanne E. T.; Baker, Michelle A.; O'Donnell, Jonathan A.; Wickland, Kimberly P.; Foks, Sydney S. W.; Zarnetske, Jay P.; Lee-Cullin, Joseph; Liu, Futing; Yang, Yuanhe; Kortelainen, Pirkko; Kolehmainen, Jaana; Dean, Joshua F.; Vonk, Jorien E.; Holmes, Robert M.; Pinay, Gilles; Powell, Michaela M.; Howe, Jansen; Frei, Rebecca J.; Bratsman, Samuel P.; Abbott, Benjamin W. (American Geophysical Union, 2021)
    Global Biogeochemical Cycles 35 (1), e2020GB006719
    Permafrost degradation is delivering bioavailable dissolved organic matter (DOM) and inorganic nutrients to surface water networks. While these permafrost subsidies represent a small portion of total fluvial DOM and nutrient fluxes, they could influence food webs and net ecosystem carbon balance via priming or nutrient effects that destabilize background DOM. We investigated how addition of biolabile carbon (acetate) and inorganic nutrients (nitrogen and phosphorus) affected DOM decomposition with 28-day incubations. We incubated late-summer stream water from 23 locations nested in seven northern or high-altitude regions in Asia, Europe, and North America. DOM loss ranged from 3% to 52%, showing a variety of longitudinal patterns within stream networks. DOM optical properties varied widely, but DOM showed compositional similarity based on Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) analysis. Addition of acetate and nutrients decreased bulk DOM mineralization (i.e., negative priming), with more negative effects on biodegradable DOM but neutral or positive effects on stable DOM. Unexpectedly, acetate and nutrients triggered breakdown of colored DOM (CDOM), with median decreases of 1.6% in the control and 22% in the amended treatment. Additionally, the uptake of added acetate was strongly limited by nutrient availability across sites. These findings suggest that biolabile DOM and nutrients released from degrading permafrost may decrease background DOM mineralization but alter stoichiometry and light conditions in receiving waterbodies. We conclude that priming and nutrient effects are coupled in northern aquatic ecosystems and that quantifying two-way interactions between DOM properties and environmental conditions could resolve conflicting observations about the drivers of DOM in permafrost zone waterways.
  • Virta, Leena; Gammal, Johanna; Järnström, Marie; Bernard, Guillaume; Soininen, Janne; Norkko, Joanna; Norkko, Alf (2019)
    Abstract The current decrease in biodiversity affects all ecosystems, and the impacts of diversity on ecosystem functioning need to be resolved. So far, marine studies about diversity?ecosystem productivity-relationships have concentrated on small-scale, controlled experiments, with often limited relevance to natural ecosystems. Here, we provide a real-world study on the effects of microorganismal diversity (measured as the diversity of benthic diatom communities) on ecosystem productivity (using chlorophyll a concentration as a surrogate) in a heterogeneous marine coastal archipelago. We collected 78 sediment cores at 17 sites in the northern Baltic Sea and found exceptionally high diatom diversity (328 observed species). We used structural equation models and quantile regression to explore relationships between diatom diversity and productivity. Previous studies have found contradictory results in the relationship between microorganismal diversity and ecosystem productivity, but we showed a linear and positive basal relationship between diatom diversity and productivity, which indicates that diatom diversity most likely forms the lowest boundary for productivity. Thus, although productivity can be high even when diatom diversity is low, high diatom diversity supports high productivity. The trait composition was more effective than taxonomical composition in showing such a relationship, which could be due to niche complementarity. Our results also indicated that environmental heterogeneity leads to substantial patchiness in the diversity of benthic diatom communities, mainly induced by the variation in sediment organic matter content. Therefore, future changes in precipitation and river runoff and associated changes in the quality and quantity of organic matter in the sea, will also affect diatom communities and, hence, ecosystem productivity. Our study suggests that benthic microorganisms are vital for ecosystem productivity, and together with the substantial heterogeneity of coastal ecosystems, they should be considered when evaluating the potential productivity of coastal areas.