Effects of copper in Daphnia are modulated by nanosized titanium dioxide and natural organic matter: what is the impact of aging duration?

During its aquatic life cycle, nanosized titanium dioxide (nTiO(2)) may interact with natural organic matter (NOM) ultimately altering the ecotoxicity of co-occurring chemical stressors such as heavy metals (e.g. copper (Cu)). In this context, the following hypotheses were tested: (1) aging of nTiO(2) along with Cu reduces Cu toxicity, (2) nTiO(2) agglomerates have a lower potential to reduce Cu toxicity and (3) aging of nTiO(2) in presence of NOM reduces Cu toxicity further. A multifactorial test design crossing three nTiO(2) levels (0.0, 0.6 and 3.0 mg/L) with two levels of NOM (0 versus 8 mg total organic carbon (TOC)/L) and seven nominal Cu concentrations (ranging from 0 to 1536 mu g/L) aged in ASTM medium for 0, 1, 3 and 6 days was realised, while two aging scenarios were applied (type 1: nTiO(2) jointly aged with Cu; type 2: Cu added after nTiO(2) aging). Subsequently, Cu toxicity was assessed using the immobility of Daphnia magna after 48 h of exposure as response variable. The experiments revealed that neither aging duration nor the extent of agglomeration (type 1 vs. type 2 aging) has a substantial impact on Cu induced toxicity. Moreover, it was confirmed that the presence of NOM substantially reduced Cu induced toxicity, independent of the aging scenario and duration. More importantly, the data suggest the ingestion of Cu loaded nTiO(2) as additional exposure pathway contributing to Cu toxicity. In conclusion, it seems unlikely that nTiO(2) concentrations currently detected in or predicted for aquatic ecosystems, which are at least one order of magnitude below the concentration tested here, influence Cu toxicity meaningfully

Stabilisation of precipitates of pedogenic dissolved organic matter by multivalent cations

Purpose Precipitation of dissolved organic matter (DOM) by multivalent cations is important for biogeochemical cycling of organic carbon. We investigated to which extent cation bridges are involved in DOM precipitation and how cross-links by cations and water molecule bridges (WaMB) stabilise the matrix of precipitated DOM. Materials and methods DOM was precipitated from the aqueous extract of a forest floor layer adding solutions of Ca(NO3)2, Al(NO3)3 and Pb(NO3)2 with different initial metal cation/C (Me/C) ratios. Precipitates were investigated by differential scanning calorimetry before and after ageing to detect cation bridges, WaMB and restructuring of supramolecular structure. Results and discussion Twenty-five to sixty-seven per cent of the dissolved organic carbon was precipitated. The precipitation efficiency of cations increased in the order Ca  3 is explained by additional formation of small AlOOH particles. Thermal analysis indicated WaMB and their disruption at T* of 53–65 °C. Like cation content, T* increased with increasing Me/C ratio and in the order Ca < Pb < Al for low Me/C. This supports the general assumption that cross-linking ability increases in the order Ca < Pb < Al. The low T* for high initial Me/C suggests less stable and less cross-linked precipitates than for low Me/C ratios. Conclusions Our results suggest a very similar thermal behaviour of OM bound in precipitates compared with soil organic matter and confirms the relevance of WaMB in stabilisation of the supramolecular structure of cation-DOM precipitates. Thus, stabilisation of the supramolecular structure of the DOM precipitates is subjected to dynamics in soils

Stabilisation of precipitates of pedogenic dissolved organic matter by multivalent cations

Purpose Precipitation of dissolved organic matter (DOM) by multivalent cations is important for biogeochemical cycling of organic carbon. We investigated to which extent cation bridges are involved in DOM precipitation and how cross-links by cations and water molecule bridges (WaMB) stabilise the matrix of precipitated DOM. Materials and methods DOM was precipitated from the aqueous extract of a forest floor layer adding solutions of Ca(NO3)2, Al(NO3)3 and Pb(NO3)2 with different initial metal cation/C (Me/C) ratios. Precipitates were investigated by differential scanning calorimetry before and after ageing to detect cation bridges, WaMB and restructuring of supramolecular structure. Results and discussion Twenty-five to sixty-seven per cent of the dissolved organic carbon was precipitated. The precipitation efficiency of cations increased in the order Ca  3 is explained by additional formation of small AlOOH particles. Thermal analysis indicated WaMB and their disruption at T* of 53–65 °C. Like cation content, T* increased with increasing Me/C ratio and in the order Ca < Pb < Al for low Me/C. This supports the general assumption that cross-linking ability increases in the order Ca < Pb < Al. The low T* for high initial Me/C suggests less stable and less cross-linked precipitates than for low Me/C ratios. Conclusions Our results suggest a very similar thermal behaviour of OM bound in precipitates compared with soil organic matter and confirms the relevance of WaMB in stabilisation of the supramolecular structure of cation-DOM precipitates. Thus, stabilisation of the supramolecular structure of the DOM precipitates is subjected to dynamics in soils

Bioconversion of Plant Raw Materials in Value-Added Products by Lentinu

info:eu-repo/semantics/publishe

Mercury Pollution In Snow Cover Around Thermal Power Plants In Cities (Omsk, Kemerovo, Tomsk Regions, Russia)

International audienceAlthough snow cover is studied as an efficient scavenger for atmospheric mercury (Hg), up to now little is known about Hg behaviour in urban snow cover impacted by thermal power plants (TPPs) during the winter heating season. This study is focused on quantification of Hg in the particulate phase in snow cover and estimation of atmospheric particulate Hg (HgP) depositional fluxes around urban TPPs in cities of Omsk, Kemerovo, Yurga, Tomsk (the south part of Western Siberia, Russia) to provide new insight into Hg occurrence in urban snow. The results demonstrate that the mean Hg content in the particulate phase of snow varied from 0.139 to 0.205mg kg-1, possibly depending on thermal power of TPPs and fuel type used. The estimated mean atmospheric HgP depositional fluxes ranged from 6.6 to 73.1 mg km-2 d-1. Around thermal power plants atmospheric HgP depositional flux was controlled by particulate load. Higher Hg contents in the particulate phase of snow and higher atmospheric HgP depositional fluxes observed in relation to the background values, as well as high enrichment factors determined for Hg in the particulate phase of snow relative to the mean Hg content in the Earth’s crust showed that the snow pollution with Hg is of anthropogenic origin. The coexistence of Hg and S observed for the particulate phase of snow indicated the possible presence of mercury sulfide in this phase. The parameters like Hg content in the particulate phase of snow and HgP atmospheric flux can be used as markers for the identification of coal combustion emission sources

Nanoparticles in the environment: where do we come from, where do we go to?

Abstract Nanoparticles serve various industrial and domestic purposes which is reflected in their steadily increasing production volume. This economic success comes along with their presence in the environment and the risk of potentially adverse effects in natural systems. Over the last decade, substantial progress regarding the understanding of sources, fate, and effects of nanoparticles has been made. Predictions of environmental concentrations based on modelling approaches could recently be confirmed by measured concentrations in the field. Nonetheless, analytical techniques are, as covered elsewhere, still under development to more efficiently and reliably characterize and quantify nanoparticles, as well as to detect them in complex environmental matrixes. Simultaneously, the effects of nanoparticles on aquatic and terrestrial systems have received increasing attention. While the debate on the relevance of nanoparticle-released metal ions for their toxicity is still ongoing, it is a re-occurring phenomenon that inert nanoparticles are able to interact with biota through physical pathways such as biological surface coating. This among others interferes with the growth and behaviour of exposed organisms. Moreover, co-occurring contaminants interact with nanoparticles. There is multiple evidence suggesting nanoparticles as a sink for organic and inorganic co-contaminants. On the other hand, in the presence of nanoparticles, repeatedly an elevated effect on the test species induced by the co-contaminants has been reported. In this paper, we highlight recent achievements in the field of nano-ecotoxicology in both aquatic and terrestrial systems but also refer to substantial gaps that require further attention in the future

Implications of Pony Lake Fulvic Acid for the Aggregation and Dissolution of Oppositely Charged Surface-Coated Silver Nanoparticles and Their Ecotoxicological Effects on <i>Daphnia magna</i>

Citrate (Cit) and polyethylenimine (BPEI)-coated silver nanoparticles (AgNPs) were used to understand how the type of capping agents and surface charge affect their colloidal stability, dissolution, and ecotoxicity in the absence/presence of Pony Lake Fulvic Acid (PLFA). In the presence of PLFA, Cit-AgNPs were stabilized, while BPEI-AgNPs were aggregated. The aggregation of BPEI-AgNPs decreased with the time, and their stabilizing effect increased at high PLFA concentration. The dissolution also differed between both AgNPs and was influenced by the PLFA concentration. Generally, BPEI-AgNPs showed a lower amount of dissolved Ag than Cit-AgNPs. The dissolved Ag concentration decreased for both AgNPs at low PLFA concentration (5 mg/L). In contrast, the extent of nanoparticle dissolution increased at high PLFA concentration (30 mg/L) but only for BPEI-AgNPs. In the absence of PLFA, the ecotoxicity of Cit-AgNPs to <i>Daphnia magna</i> was higher than that of BPEI-AgNPs. However, the ecotoxicity of AgNPs in the presence of PLFA was up to 70% lower than in their absence. We demonstrated that the differences in colloidal stability, dissolution, and ecotoxicity may be attributed to the different capping agents, surface charge, and concentration of natural organic matter (NOM) as well as to the formation of dissolved Ag complexes with NOM