Search results for "dissolved"

Study of the Stability of Citrate Capped AgNPs in Several Environmental Water Matrices by Asymmetrical Flow Field Flow Fractionation

2021

Asymmetrical flow field-flow fractionation (AF4) coupled to UV-Vis and dynamic light scattering (DLS) detectors in series, was tested for stability studies of dispersions of citrate-capped silver nanoparticles (AgNPs) in several water matrices. The main goal is to provide knowledge to understand their possible behavior in the environment for short times since mixturing (up to 180 min). Ultrapure (UPW), bottled (BW1, BW2), tap (TW), transitional (TrW) and sea water (SW) matrices were assayed. Observations were compatible with the aggregation of AgNPs, a change in the plasmon band and a size growth with time were done. Fractograms showed different evolution fingerprints in the function of the…

Application of 3D printed scavengers for improving the accuracy of single-particle inductively coupled plasma mass spectrometry analyses of silver na…

2023

The determination of silver nanoparticles (Ag NPs) with single-particle inductively coupled plasma mass spectrometry can be severely interfered with coexisting dissolved silver causing high background signals, which can lead to inaccurate quantification of NP size and particle concentration. In this paper, chemically active and reusable 3D printed scavengers are applied for highly efficient dissolved silver removal in Ag NP dispersions, allowing more accurate determination of particle concentration and size. Selective laser sintering was used for constructing the porous 3D scavengers constituting of polystyrene used as a supporting material and ion-exchange material SiliaBond Tosic acid (TA…

Labile nitrogen, carbon, and phosphorus pools and nitrogen mineralization and immobilization rates at low temperatures in seasonally snow-covered soi…

2006

Surface mineral horizons from four ecosystems sampled in the northwestern Italian Alps were incubated at −3 and +3°C to simulate subnivial and early thaw period temperatures for a seasonally snow-covered area. The soil profiles at these sites represent extreme examples of management, grazed meadow (site M) and extensive grazing beneath larch (site L) or naturally disturbed by avalanche and colonized by alder (site A) and the expected forest climax vegetation beneath fir (site F). Changes in labile pools of nitrogen (N) and phosphorus (P) were active at all sites at both temperatures during 14 days of laboratory incubation. Ammonium was the dominant inorganic form of total dissolved N (TDN),…

Assessing the quality of dissolved organic matter in forest soils using ultraviolet absorption spectrophotometry

2007

Abbreviations: DOC, dissolved organic carbon; SUVA, specifi c ultraviolet absorbance; UV, ultraviolet. Ultraviolet spectrophotometry was used to investigate the effects, 30 yr after planting, of tree species substitution on the aromatic C content and related properties of dissolved organic carbon (DOC). Precautions were taken to correct measurements for the absorbance of NO 3 and dissolved Fe. In litter leachates, a signifi cant reduction in the aromatic content of DOC was found in the Douglas-fi r [Pseudotsuga menziesii (Mirb.) Franco] plantation but not in the beech (Fagus sylvatica L.) plantation. The disturbance of short-term C dynamics thus revealed agreed well with fi eld observations…

Mercury concentration and speciation in volcanic aquifers: measurements in Italy and Guadeloupe (Lesser Antilles)

2008

Methane-oxidizing and photoautotrophic bacteria are major producers in a humic lake with large anoxic hypolimnion

2011

Heterotrophic processes are considered to prevail in lakes with high terrestrial loading and a high content of dissolved organic carbon. However, previous studies have shown abundant methanotrophic bacteria (MOB) and photoautotrophic green sulphur bacteria (GSB) in some boreal lakes. We used genetic and lipid biomarkers to follow the seasonal succession of the abundance and carbon biomass of the major bacterial groups in Lake Mekkojarvi, a small Finnish polyhumic lake with a large anoxic hypolimnion. Biomarkers were based on length heterogeneity analysis of 16S rRNA gene amplification by polymerase chain reaction (PCR) (LH-PCR) and on phospholipid fatty acid (PLFA) analysis. Representative …

Iron and pH regulating the photochemical mineralization of dissolved organic carbon

2017

Solar radiation mineralizes dissolved organic matter (DOM) to dissolved inorganic carbon through photochemical reactions (DIC photoproduction) that are influenced by iron (Fe) and pH. This study addressed as to what extent Fe contributes to the optical properties of the chromophoric DOM (CDOM) and DIC photoproduction at different pH values. We created the associations of Fe and DOM (Fe-DOM) that cover the range of loadings of Fe on DOM and pH values found in freshwaters. The introduced Fe enhanced the light absorption by CDOM independent of pH. Simulated solar irradiation decreased the light absorption by CDOM (i.e., caused photobleaching). Fe raised the rate of photobleaching and steepened…

Terrestrial carbohydrates support freshwater zooplankton during phytoplankton deficiency

2016

Article

The importance of phytoplankton production for carbon budgets in a semiarid floodplain wetland

2011

Phytoplankton production (PP) in wetlands is not measured as often as that of macrophytes. A three year-study during a period of sustained high flooding was undertaken in a central Spanish floodplain wetland (Las Tablas de Daimiel National Park) to determine net PP, its spatial heterogeneity and controlling factors, and compare it with primary production in macrophyte communities. This enabled us to estimate carbon budgets for each community. All PP variables showed high spatial and temporal variability among sites, resulting in low coherence even when flooding connected all sites. Net PP corresponded to 25- 36% of submerged plant production and 3-10% of helophyte production. Net PP was con…

Browning-induced changes in trophic functioning of planktonic food webs in temperate and boreal lakes: insights from fatty acids

2022

AbstractThe effects of lake browning on trophic functioning of planktonic food webs are not fully understood. We studied the effects of browning on the response patterns of polyunsaturated fatty acids and n−3/n−6 ratio in seston and compared them between boreal and temperate lakes. We also compared the regional differences and the effects of lake browning on the reliance of zooplankton on heterotrophic microbial pathways and the mass fractions of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in zooplankton. Lake browning was associated with increasing phytoplankton biomass and concentrations of EPA and DHA in both temperate and boreal lakes, but the seston n−3/n−6 ratio was low…