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Importance of the structure and micropores of sedimentary organic matter in the sorption of phenanthrene and nonylphenol
2020
Xu, Decheng | Hu, Shujie | Xiong, Yongqiang | Yang, Yu | Ran, Yong
The demineralized fraction (DM), lipid-free fraction (LF), nonhydrolyzable organic carbon fraction (NHC), and black carbon (BC) were isolated from five marine surface sediments, and they were characterized by elemental analysis as well as CO₂ and N₂ adsorption techniques, respectively. The NHC fractions were characterized using advanced solid-state ¹³C nuclear magnetic resonance (NMR) and x-ray photoelectron spectroscopy (XPS). Then, the sorption isotherms of phenanthrene (Phen) and nonylphenol (NP) on all of the samples were investigated by a batch technique. The CO₂ micropore volumes were corrected for the outer specific surface areas (SSAs) by using the N₂-SSA. Significant correlations between the micropore-filling volumes of Phen and NP and the micropore volumes suggested that the micropore-filling mechanism dominated the Phen and NP sorption. Meanwhile, the (O + N)/C atomic ratios were negatively and significantly correlated with the sorption capacities of Phen and NP, indicating that the sedimentary organic matter (SOM) polarity also played a significant role in the sorption process. In addition, a strong linear correlation was demonstrated between the aromatic C and the sorption capacity of Phen for the NHC fractions. This study demonstrates the importance of the micropores, polarity, and aromaticity on the sorption processes of Phen and NP in the sediments.
Afficher plus [+] Moins [-]Long-term effects of Cu(OH)2 nanopesticide exposure on soil microbial communities
2021
Peixoto, Sara | Henriques, Isabel | Loureiro, Susana
Copper-based (nano)pesticides in agroecosystems may result in unintended consequences on non-target soil microbial communities, due to their antimicrobial broad spectrum. We studied the impact of a commercial Cu(OH)₂-nanopesticide, over 90 days, at single and season agricultural application doses, in the presence and absence of an edaphic organism (the isopod Porcellionides pruinosus), on microbial communities’ function, structure and abundance. Results were compared to the effects of Cu(OH)₂-ionic. The nanopesticide application resulted in significant changes on both bacterial and fungal communities’ structure, particularly at the season application. The exposed bacterial community presented a significantly lower richness, and higher diversity and evenness while the exposed fungal community presented lower diversity and richness. At the functional level, a significant increase on microbial ability of carbon utilization and a significant decrease on the β−glucosidase activity was observed for communities exposed to the nanopesticide. Regarding Cu forms, less pronounced effects were observed in soils spiked with Cu(OH)₂-ionic, which might result from lower Cu concentration in porewater. The presence of P. pruinosus did not induce significant changes in diversity indexes (fungal community) and community-level physiological profiling, suggesting an attenuation of the nanopesticide effect. This study revealed that Cu(OH)₂-nanopesticide, at doses applied in agriculture, impact the soil microbial community, possibly affecting its ecological role. On the other hand, invertebrates may attenuate this effect, highlighting the importance of jointly including different interacting communities in the risk assessment of nanopesticides in soils.
Afficher plus [+] Moins [-]Chronic effects of six micro/nano-Cu2O crystals with different structures and shapes on Daphnia magna
2015
Wang, Huihui | Fan, Wenhong | Xue, Feng | Wang, Xiaolong | Li, Xiaomin | Guo, Lin
Six micro/nano-Cu2O crystals evolved from cubes to corner-truncated cubes, vertex-truncated octahedrons and ultimately to octahedrons were synthesized in this work, and the chronic toxicity of these crystal suspensions (10 μg L−1) for Daphnia magna was investigated over a 30-day period. Our results indicated that the octahedrons had the most evident toxic effect, but the cubes were minimally toxic. The mortality rate of the octahedral treatment was as high as 86.7%, whereas that of the cubic treatment was only 6.7%. Significant inhibitions in growth and reproduction were observed under octahedral exposure, with reduced impacts from vertex-truncated octahedrons, corner-truncated cubes, and cubic crystals. The chronic effects of different micro/nano-Cu2O crystals were related to their solubility in the gut of the organisms. The solubility of micro/nano-Cu2O crystals was influenced by surface atomic arrangement and diverse surface activity. Thus, the structure and intestinal solubility of nanocrystals should be evaluated for long-term toxicity.
Afficher plus [+] Moins [-]Rubus plicatus Weihe & Nees: resilience to pollution caused by stone quarries
2024
This study aimed to analyze the effect of pollution caused by stone quarries on the morpho-anatomy, biochemistry, and physiology of a medicinal wild bramble Rubus plicatus Weihe & Nees. Samples were collected from two natural protected areas: Iron Gates Natural Park and Jiu Gorge National Park, both located in the southwestern part of Romania, and two unpolluted areas from these parks as background sites. We carried out the following analyses on the collected leaves of this taxon: morphology, micromorphology, anatomy, assimilating pigments, heavy metals (Pb, Ni, Cr, Fe), dry mass, bioactive compounds (total phenols and flavonoids), and antioxidant capacity. The results showed more stomata, higher amounts of assimilating pigments, higher amounts of heavy metals (especially lead), less dry mass, less phenols, and more flavonoids in Rubus plicatus leaves from polluted areas compared to areas without sources of pollution. The increased number of stomata and the amounts of assimilator pigments revealed the mechanisms developed by this species in order to survive in polluted conditions.
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