Effect of alginate on the aggregation kinetics of copper oxide nanoparticles (CuO NPs): bridging interaction and hetero-aggregation induced by Ca<Superscript>2+</Superscript>

The stability of CuO nanoparticles (NPs) is expected to play a key role in the environmental risk assessment of nanotoxicity in aquatic systems. In this study, the effect of alginate (model polysaccharides) on the stability of CuO NPs in various environmentally relevant ionic strength conditions was investigated by using time-resolved dynamic light scattering. Significant aggregation of CuO NPs was observed in the presence of both monovalent and divalent cations. The critical coagulation concentrations (CCC) were 54.5 and 2.9 mM for NaNO₃ and Ca(NO₃)₂, respectively. The presence of alginate slowed nano-CuO aggregation rates over the entire NaNO₃ concentration range due to the combined electrostatic and steric effect. High concentrations of Ca²⁺ (>6 mM) resulted in stronger adsorption of alginate onto CuO NPs; however, enhanced aggregation of CuO NPs occurred simultaneously under the same conditions. Spectroscopic analysis revealed that the bridging interaction of alginate with Ca²⁺ might be an important mechanism for the enhanced aggregation. Furthermore, significant coagulation of the alginate molecules was observed in solutions of high Ca²⁺ concentrations, indicating a hetero-aggregation mechanism between the alginate-covered CuO NPs and the unabsorbed alginate. These results suggested a different aggregation mechanism of NPs might co-exist in aqueous systems enriched with natural organic matter, which should be taken into consideration in future studies.

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Graphical abstract Hetero-aggregation mechanism of CuO nanoparticles and alginate under high concentration of Ca²⁺

     

Rapid metal extractability tests from polluted mining soils by ultrasound probe sonication and microwave-assisted extraction systems

Ultrasonic probe sonication (UPS) and microwave-assisted extraction (MAE) were used for rapid single extraction of Cd, Cr, Cu, Ni, Pb, and Zn from soils polluted by former mining activities (Mónica Mine, Bustarviejo, NW Madrid, Spain), using 0.01 mol L^?1 calcium chloride (CaCl₂), 0.43 mol L^?1 acetic acid (CH₃COOH), and 0.05 mol L^?1 ethylenediaminetetraacetic acid (EDTA) at pH 7 as extracting agents. The optimum extraction conditions by UPS consisted of an extraction time of 2 min for both CaCl₂ and EDTA extractions and 15 min for CH₃COOH extraction, at 30% ultrasound (US) amplitude, whereas in the case of MAE, they consisted of 5 min at 50 °C for both CaCl₂ and EDTA extractions and 15 min at 120 °C for CH₃COOH extraction. Extractable concentrations were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). The proposed methods were compared with a reduced version of the corresponding single extraction procedures proposed by the Standards, Measurements and Testing Programme (SM&T). The results obtained showed a great variability on extraction percentages, depending on the metal, the total concentration level and the soil sample, reaching high values in some areas. However, the correlation analysis showed that total concentration is the most relevant factor for element extractability in these soil samples. From the results obtained, the application of the accelerated extraction procedures, such as MAE and UPS, could be considered a useful approach to evaluate rapidly the extractability of the metals studied.     

Are seed and dispersal characteristics of plants capable of predicting colonization of post-mining sites?

Seed characteristics play an important role in the colonization and subsequent persistence of species during succession in disturbed sites and thus may contribute to being able to predict restoration success. In the present study, we investigated how various seed characteristics participated in 11 spontaneous successional series running in different mining sites (spoil heaps, extracted sand and sand-gravel pits, extracted peatlands, and stone quarries) in the Czech Republic, Central Europe. Using 1864 samples from 1- to 100-years-old successional stages, we tested whether species optimum along the succession gradient could be predicted using 10 basic species traits connected with diaspores and dispersal. Seed longevity, diaspore mass, endozoochory, and autochory appeared to be the best predictors. The results indicate that seed characteristics can predict to a certain degree spontaneous vegetation succession, i.e., passive restoration, in the mining sites. A screening of species available in the given landscape (regional and local species pools) may help to identify those species which would potentially colonize the disturbed sites. Extensive databases of species traits, nowadays available for the Central European flora, enable such screening.     

An Integrated Assessment by Models for Energy Systems Analysis and Life-Cycle Assessment with a Case Study of Advanced Fossil-Fired Power Plants in China

We developed an integrated assessment (IA) using models for energy systems analysis and life-cycle assessment (LCA). Based on this assessment framework, we developed cost-benefit analysis (CBA) case studies for a hypothetical project designed to introduce advanced fossil-fired power generation technologies in China. Our MARKAL model for Japan confirmed that radical reductions (i.e., 80 % by 2050) of carbon dioxide (CO₂) could be attained from energy systems alone and that credit for emission allowances was required. We evaluated life-cycle costs and emissions of carbon dioxide, sulfur oxide, and nitrogen oxide gases for the energy technologies using an LCA model. Further, we applied a power generation planning model for six Chinese grids to provide a power mix structure, potentially producing credit by installing fossil-fired power generation technology and by using baseline grid emission factors with an average cost of electricity. Finally, by using dynamic emission reductions and additional costs from the two models, we conducted case studies of CBA for a hypothetical project to install the technologies in China. This was accomplished by evaluating emission reductions in monetary terms and by applying a life-cycle impact assessment model. A unique feature of our IA is its dynamic (time-varying) assessment of costs and benefits.     

赤水河流域土地利用结构对氮素输出的影响

以赤水河流域为研究对象,根据Landsat8 OLI卫星影像获取流域土地利用现状,利用ArcGIS的水文、空间分析模块提取22个子流域,分析子流域不同形态氮(TN、NO_3~--N、NH_4~+-N)的输出特征及其与土地利用结构之间的关系。结果表明:赤水河各子流域TN、NO_3~--N、NH_4~+-N浓度范围分别为1. 27～4. 13、1. 14～3. 97、0. 01～0. 35 mg/L。TN和NO_3~--N与流域内耕地、灌草的相关系数分别为0. 663 (p 0. 01)、0. 538 (p 0. 05)和0. 631(p0. 01)、0. 530(p0. 05),TN、NO_3~--N、NH_4~+-N与流域内耕地、灌草浓度表现为显著正相关,流域内耕地、灌草对TN、NO_3~--N输出均表现为显著的"氮源"作用。NH_4~+-N的相关系数为-0. 558(p 0. 01),耕地对NH_4~+-N输出起显著"氮汇"作用。TN、 NO_3~--N与林地的相关系数为-0. 673 (p 0. 01)、-0. 652(p0. 01),林地对TN、NO_3~--N输出起到了显著的"氮汇"作用。NH_4~+-N与林地的相关系数为0. 435(p0. 05),林地对NH_4~+-N的输出起"氮源"作用。各子流域的分析结果表明,流域受土地利用结构带来的面源污染影响显著。     

Exploring socio-cultural values of ecosystem service categories in the Central Alps: the influence of socio-demographic factors and landscape type

The socio-cultural assessment of ecosystem services has been proposed as a promising tool for eliciting people’s preferences towards ecosystem services. Despite an increasing integration of the socio-cultural perspective in ecosystem service research, little knowledge exists about linkages between landscape and the socio-cultural values people assign to ecosystem services. This paper combines a socio-cultural valuation approach with the use of landscape pictures to analyse and compare people’s perceived importance of the provisioning, regulating, and cultural ecosystem service categories across three landscape types (i.e. larch meadows, spruce forests, and hay meadow). A survey with 470 tourists visiting the region of South Tyrol (Italy) was conducted to link people’s perceived importance to their socio-demographic background and to the landscape types explored. The results show that regulating ecosystem services are preferred over provisioning and cultural services, whereby environmental awareness is found to be more influential than formal education levels regarding the perceived importance of regulating services. The results further demonstrate that cultural background is an important driver in determining people’s perceived importance of cultural services. The underlying landscape types, however, exert an even stronger influence on people’s socio-cultural valuation of ecosystem service categories. This finding suggests that the focus of most ecosystem services assessments on the study area as a whole risks mistakenly attributing differences in people’s socio-cultural values to socio-demographic characteristics only. A better knowledge of the spatial integration of socio-cultural values, however, could help with anticipating the consequences of changes in the landscape and provide better guidance for future landscape planning.     

Enrichment of trace elements in the clay size fraction of mining soils

Reactive waste dumps with sulfide minerals promote acid mine drainage (AMD), which results in water and soil contamination by metals and metalloids. In these systems, contamination is regulated by many factors, such as mineralogical composition of soil and the presence of sorption sites on specific mineral phases. So, the present study dedicates itself to understanding the distribution of trace elements in different size fractions (<2-mm and <2-μm fractions) of mining soils and to evaluate the relationship between chemical and mineralogical composition. Cerdeirinha and Penedono, located in Portugal, were the waste dumps under study. The results revealed that the two waste dumps have high degree of contamination by metals and arsenic and that these elements are concentrated in the clay size fraction. Hence, the higher degree of contamination by toxic elements, especially arsenic in Penedono as well as the role of clay minerals, jarosite, and goethite in retaining trace elements has management implications. Such information must be carefully thought in the rehabilitation projects to be planned for both waste dumps.     

Institutional challenges of adopting ecosystem-based adaptation to climate change

In view of past environmental degradation and anticipated climate change impacts, we assessed the potential for ecosystem-based adaptation in the Murray-Darling Basin, Australia. In a workshop with staff from three Catchment Management Authorities (CMAs) who had jurisdiction over three sub-basins, as well as technical experts, nine adaptation options were identified that ranged from environmental flows, restoring river channel habitat, reoperating infrastructure and controlling invasive species. A Catchment Adaptation Framework was developed and used to assess and compare these adaptation options with each of the CMAs, drawing on interviews with their key stakeholders, to identify the risks, benefits and costs. We found that ecosystem-based adaptation can augment catchment management programs and requires investment in a suite of different but complementary measures to lower risk. Our research found institutional challenges in implementing this approach, including the complexities of multi-agency management, constricting legal requirements, narrow funding arrangements, under-developed institutional capacity, difficulties of implementing catchment-scale programs on private property and the need to adhere to community expectations. These institutional issues are ubiquitous internationally and point to the wider issues of providing sufficient management capacity to support adaptation. The Catchment Adaptation Framework presented here enables river basin managers to systematically assess the adaptation options to better inform their decision-making.