A Priori Typology-Based Prediction of Benthic Macroinvertebrate Fauna for Ecological Classification of Rivers

We evaluated a simple bioassessment method based on a priori river typology to predict benthic macroinvertebrate fauna in riffle sites of rivers in the absence of human influence. Our approach predicted taxon lists specific to four river types differing in catchment area with a method analogous to the site-specific RIVPACS-type models. The reference sites grouped in accordance with their type in NMS ordination, indicating that the typology efficiently accounted for natural variation in macroinvertebrate assemblages. Compared with a null model, typology greatly increased the precision of prediction and sensitivity to detect human impairment and strengthened the correlation of the ratio of observed-to-expected number of predicted taxa (O/E) with the measured stressor variables. The performance of the typology-based approach was equal to that of a RIVPACS-type predictive model that we developed. Exclusion of rarest taxa with low occurrence probabilities improved the performance of both approaches by all criteria. With an increasing inclusion threshold of occurrence probability, especially the predictive model sensitivity first increased but then decreased. Many common taxa with intermediate type-specific occurrence probabilities were consistently missing from impacted sites, a result suggesting that these taxa may be especially important in detecting human disturbances. We conclude that if a typology-based approach such as that suggested by the European Union’s Water Framework Directive is required, the O/E ratio of type-specific taxa can be a useful metric for assessment of the status of riffle macroinvertebrate communities. Successful application of the approach, however, requires biologically meaningful river types with a sufficient pool of reference sites for each type.     

Fractionation of rare earth and other trace elements in crabs, Ucides cordatus, from a subtropical mangrove affected by fertilizer industry

Fractionation of rare earth elements (REE) and other trace metal concentrations (Th, U, Cd, Cr, Cu, Ni, Pb, and Zn) between mangrove sediments and claw muscles and shells of male crabs (Ucides cordatus) from a subtropical estuary highly impacted by fertilizer industry activities was investigated. This is the first record of REE distribution in these organisms, and the results showed higher accumulations of these metals, U and Th in shells, probably related to the replacement of Ca during molting. Contents of Cd, Cr and Ni were similar in both tissues, but Cu, Zn and Pb were mostly accumulated in the claw muscle with concentrations above those considered safe for human consumption according to the Brazilian legislation. REE fractionation was different in the analyzed tissues being softer in the shells. The results provided evidences that the water absorbed during molting controls the chemistry of REE in shells. In contrast, the chemistry of REE in the claw muscle, in which was observed preferential absorption of light REE, is controlled by diet. REE fractionation obtained for the claw muscles was closely correlated to the observed in the contaminated substrate and in materials related to the production of phosphate fertilizers (contamination source), which supports their transference to this Ucides cordatus tissue without fractionation by the ingestion of sediments. Our results showed the potential use of crab tissues for monitoring REE and trace element sources in mangrove areas, with claw muscle exhibiting the contaminant source fingerprint.     

Effects of organic ligands on fractionation of rare earth elements (REEs) in hydroponic plants: an application to the determination of binding capacities by humic acid for modeling

Previous studies have revealed the fractionation processes of rare earth elements (REEs) in hydroponic plants, with a heavy REE (HREE, the elements from Gd to Lu) enrichment in leaves. In this study, effects on the HREE enrichment in soybean leaves with additions of carboxylic acids (acetate, malate, citrate, NTA, EDTA and DTPA) and two soil humic acids (HAs) were investigated. REE speciation in carboxylic acid and HA solutions was simulated using Visual MINTEQ and Model V, respectively. The results showed that the effects caused by carboxylic acids were strongly dependent on the differences between their binding strengths for light REEs (LREEs, the elements from La to Eu) and those for HREEs. A good correlation existed between these effects and the changes of free REE ions in solutions. This relationship was also observed for the HA treatments, provided that the intrinsic equilibrium constants of REEs for cation–proton exchange with HA (i.e., pK_MHA) in Model V were estimated using a free-energy relationship with the stability constants for REE complexation with lactic acid. It is suggested that this set of pK_MHA values is more suitable for use in Model V for the simulation of REE complexation with HA.     

Rare earth elements in China: Policies and narratives of reinventing an industry

After top producer China decided in 2010 to tighten its export quotas for rare earth elements (REE), major customers feared being cut off from the valuable metals. The trade dispute intensified when the EU, the USA, and Japan brought the case before the WTO. The export controls raise questions about China’s intentions and strategies. This article argues that China’s export policy should not be viewed in isolation. The export controls are embedded in a greater transformation of the strategic REE industry. Beijing promotes a broad set of policies, including industry reorganization, resource conservation, and environmental protection. Next, the article examines three narratives that may be constitutive of the Chinese policy. Findings indicate that the geopolitical narrative, which sees natural resources as instruments of power politics, can be only partly attributed to China’s REE policies. The major driving motives are domestic concerns for resource conservation and environmental protection, as well as the development of competitive downstream industries.     

Respective influence of habitat conditions and management regimes on prealpine calcareous grasslands

The calcareous grasslands of the south-western French Alps have been poorly studied, although they provide suitable habitat for rare plant species and communities. The separate and combined effects on calcareous grassland communities of habitat conditions (lithology, soil moisture) and management regimes (grazing intensity, cutting regime) were studied using constrained ordination techniques (canonical correspondence analysis with variance partitioning). Among the explanatory variables considered, the most important factor determining floristic composition was lithology, which explained 11.9% of floristic variability, followed by grazing intensity (6.0%). Additive effects of management and lithology explained 23.9% of floristic variability. Species niche amplitude was measured by conditional variances of samples along main ordination axes, in order to define adequate conservation management for the rarest short-lived species with narrow niche breadth on both habitat and management gradients.     

环保型二次锌电极的研究

为了保护环境 ,减小污染 ,节约金属资源 ,十分有必要研究和开发环保型二次锌电极。本文提出了在表面覆盖稀土氢氧化物膜的二次锌电极的新思想 ,首先利用恒电位电解的方法在电极表面成功地覆盖一层均匀致密的稀土氢氧化物膜 ,再用恒电位电解、循环伏安、模拟充放电等实验方法 ,全面考察了稀土氢氧化物膜对锌电极可充性的影响。实验结果表明 :在锌电极表面成膜后 ,可以显著地抑制充电过程中的枝晶生长 ,又在电解液中加入枝晶抑制剂 ( CTMB) ,最后达到了令人满意的效果 ;同时 ,成膜还能有效地缓解锌电极在充放电过程中的容量损失。在整个实验过程中 ,完全去掉了传统的锌电极添加剂——有毒的汞 ,从而为研究和开发实用的环保型二次锌电极提供了一条新的途径     

稀土氨氮废水处理技术研究进展

本文旨在研究到目前为止前人对稀土氨氮废水处理技术的进展情况,尽管稀土氨氮废水的处理方法颇多,然而不是处理成本太高就是对水质的要求太苛刻,用于实践不太乐观;我们采用混合处理稀土氨氮废水的方法将减少处理成本,增强处理效果,如：化学沉淀＋吹脱,吹脱＋吸附等;另外,处理稀土氨氮废水要注意回收氨氮副产品,以抵消处理成本,达到清洁生产的目的。     

湖南古丈奥陶纪红石林地层特征与石灰岩沉积环境分析

湘西古丈红石林国家地质公园出露着奥陶系牯牛潭组红色石灰岩地层,含角石化石,被认为是海相红层.野外观察地层红色深浅与其层理/层次变化关系判断为近于同期形成,属原生色.水生化石存在红层中,前者反映水下缺氧条件,而红层指示着氧化环境,两种指示尖锐对立,意味着可能至少一方存在认识偏差.采样分析结果表明,赤铁矿和针铁矿是其中可以...     

Treatment of exhaust fluorescent lamps to recover yttrium: experimental and process analyses

The paper deals with recovery of yttrium from fluorescent powder coming from dismantling of spent fluorescent tubes. Metals are leached by using different acids (nitric, hydrochloric and sulphuric) and ammonia in different leaching tests. These tests show that ammonia is not suitable to recover yttrium, whereas HNO(3) produces toxic vapours. A full factorial design is carried out with HCl and H(2)SO(4) to evaluate the influence of operating factors. HCl and H(2)SO(4) leaching systems give similar results in terms of yttrium extraction yield, but the last one allows to reduce calcium extraction with subsequent advantage during recovery of yttrium compounds in the downstream. The greatest extraction of yttrium is obtained by 20% w/v S/L ratio, 4N H(2)SO(4) concentration and 90°C. Yttrium and calcium yields are nearly 85% and 5%, respectively. The analysis of variance shows that acid concentration alone and interaction between acid and pulp density have a significant positive effect on yttrium solubilization for both HCl and H(2)SO(4) medium. Two models are empirically developed to estimate yttrium and calcium concentration during leaching. Precipitation tests demonstrate that at least the stoichiometric amount of oxalic acid is necessary to recover yttrium efficiently and a pure yttrium oxalate n-hydrate can be produced (99% grade). The process is economically feasible if other components of the fluorescent lamps (glass, ferrous and non-ferrous scraps) are recovered after the equipment dismantling and valorized, besides the cost that is usually paid to recycling companies for collection, treatment or final disposal of such fluorescent powders.     

Rare event risk analysis – application to iceberg collision

To design an engineering system, testing in extreme conditions is at least recommended if not required. There are ambiguities about how to define an extreme state and how to consider it in the design of a system or its operation. The probability estimation of such an event is challenging due to data scarcity, especially in many engineering domains, e.g. offshore development. In this study, available techniques for analyzing the probability of extreme events are examined for their suitability in engineering applications, and a framework is proposed for rare event risk analysis. The framework is comprised of three phases. In the first phase, the outlier based extreme value theory is implemented to estimate the rare event probability. The maximum likelihood criterion is used to estimate the extreme distribution parameters. In the second phase, the rare event is considered as a heavy tail event, and the tail index is estimated through the Hill and the SmooHill estimator. In the third phase, The uncertainty analysis is conducted, and the risk is computed. The proposed methodology is tested for extreme iceberg risk assessment on large offshore structures in the Flemish Pass basin. For this specific case, the estimated design extreme iceberg speed was 4.31 km/h, with an occurrence probability of 3.61E-06.