氧化亚铁硫杆菌对酸化铅锌尾矿中Zn、As淋溶释放的影响

以青海某铅锌尾矿为研究对象进行酸预处理加速模拟静态淋溶实验,重点研究了氧化亚铁硫杆菌（At.f菌）接种量变化对尾矿中重金属Zn、As迁移释放的影响。结果表明,随时间延长,接种量变化均可导致淋溶体系pH值下降、电导率上升,氧化还原电位先上升后下降。At.f菌可明显促进Zn、As的释放,不同接种量对重金属的迁移释放作用不同;At.f菌存在下,Zn的释放能力大于As,Zn优先于As溶出,Zn、As浓度均表现为快速释放和缓慢释放并趋于平稳两个阶段,Evolich模型和Guass模型可分别描述Zn、As的释放过程。通过对细菌淋溶前后残渣SEM-EDS及XRD图谱分析发现,淋溶后尾矿颗粒结构疏松,表面腐蚀明显,生成了CaSO4、钙磷石等不溶物,使Zn、As后期释放减慢。     

利用制糖副产物土壤化赤泥的效果

赤泥因具有碱性高、孔隙率低、团聚性差和养分缺乏等问题,同时因其生产性状差,堆场植被复垦难以实现;而且在堆存过程中,重金属元素具有潜在的长期浸出性,存在污染环境的风险。利用富含多种有机成分且蓬松度好的制糖副产物酒精废醪液、蔗渣对赤泥进行改性,可实现土壤化及植被复垦。结果表明,添加制糖副产物对赤泥理化性质及所含重金属迁移性具有显著影响,蔗渣能使孔隙度得到改善,酒精废醪液与赤泥比值（mL:g）＞3时,赤泥的pH可降至8以下,配合添加酒精废醪液和蔗渣可使赤泥的有机质含量从（19.8±1.2）g·kg-1增加到200 g·kg-1左右,经土柱模拟实验发现添加剂可使赤泥所含重金属的生物有效性增强。     

‘Sea of blood’: the intended and unintended effects of criminalising humanitarian volunteers assisting migrants in distress at sea

This paper investigates the impact of the recent criminalisation of humanitarian actors engaged in the search for and rescue of migrants in distress in the Mediterranean Sea, focusing on the impact on the motivation and engagement of humanitarian volunteers in Greece. It argues that criminalisation is aimed at reducing search and rescue (SAR) activities and thus removing perceived ‘pull factors’ for migrants. The paper locates this phenomenon within the broader trend of policing and punishing those who assist migrants in order to deter them and prevent others from engaging in such endeavours. It finds that efforts to criminalise can have the unintended effects of encouraging and mobilising volunteers, as well as generating public attention and support for migrants. However, the negative consequences of criminalisation are far-reaching, including contributing to a high mortality rate among those crossing the Mediterranean without SAR capabilities and the heightened risk of violence against migrants and those who help them.     

Ranging of songs with the song type on use of different cues in Carolina wrens: effects of familiarity

Male territorial song birds are usually spaced far apart and most often hear conspecific song after it has been degraded by propagation through the environment. Their ability to use the degradation of songs to assess the distance of a singing rival without approaching (called ranging) presumably increases the efficiency of defending a territory. In order to assess degradation in a song the receiver needs to compare the characteristics of the received song to its characteristics at the source or at different distances. Earlier experiments on ranging in species with song repertoires have suggested that prior familiarity with the particular song type is necessary for ranging. Here I show that male Carolina wrens (Thryothorus ludovicianus) can use either temporal or spectral characteristics for ranging song types which they were unlikely to have heard previously. Playbacks consisting of only one song prevented subjects' close-range experience with the loudspeaker, and flights beyond the loudspeaker provided direct evidence for over-assessment of distance when songs were degraded. Because ranging of songs was not affected by the degree of familiarity with the song type, this experiment provides no evidence that song repertoires hinder ranging in Carolina wrens, as suggested by Morton's ranging hypothesis. Instead, at least approximate ranging of songs is evidently possible by assessment of degradation in general features of a species' songs. Received: 9 August 1996 / Accepted after revision: 15 February 1997     

Simulation of 137Cs Migration over the Soil–Plant System of Peat Soils Contaminated after the Chernobyl Accident

A mathematical model was constructed to simulate the processes of ¹³⁷Cs migration in peat soils and its uptake by vegetation. Model parameters were assessed and the pattern of ¹³⁷Cs distribution over soil profile was predicted in case of peat soils, which are typical of the Russian regions contaminated after the Chernobyl accident. The ecological half-life of ¹³⁷Cs in the plant-root soil zone was calculated, and a long-term prognosis of the radionuclide uptake by plants was made.     

Estimating the complexity of bird song by using capture-recapture approaches from community ecology

Repertoire size, the number of unique song or syllable types in the repertoire, is a widely used measure of song complexity in birds, but it is difficult to calculate this exactly in species with large repertoires. A new method of repertoire size estimation applies species richness estimation procedures from community ecology, but such capture-recapture approaches have not been much tested. Here, we establish standardized sampling schemes and estimation procedures using capture-recapture models for syllable repertoires from 18 bird species, and suggest how these may be used to tackle problems of repertoire estimation. Different models, with different assumptions regarding the heterogeneity of the use of syllable types, performed best for different species with different song organizations. For most species, models assuming heterogeneous probability of occurrence of syllables (so-called detection probability) were selected due to the presence of both rare and frequent syllables. Capture-recapture estimates of syllable repertoire size from our small sample did not differ significantly from previous estimates using larger samples of count data. However, the enumeration of syllables in 15 songs yielded significantly lower estimates than previous reports. Hence, heterogeneity in detection probability of syllables should be addressed when estimating repertoire size. This is neglected using simple enumeration procedures, but is taken into account when repertoire size is estimated by appropriate capture-recapture models adjusted for species-specific song organization characteristics. We suggest that such approaches, in combination with standardized sampling, should be applied in species with potentially large repertoire size. On the other hand, in species with small repertoire size and homogenous syllable usage, enumerations may be satisfactory. Although researchers often use repertoire size as a measure of song complexity, listeners to songs are unlikely to count entire repertoires and they may rely on other cues, such as syllable detection probability.Communicated by A. Cockburn     

RIPARIAN FOREST EFFECT ON LATERAL STREAM CHANNEL MIGRATION IN THE GLACIAL TILL PLAINS1

ABSTRACT: Dendrochronology analyses of point bar complexes were used to quantify the effects of riparian forests on local lateral migration of bends in seven streams in the glacial till plains of north central Missouri. Stream bends were paired with similar bank height, midchannel radius of curvature, soil composition, and watershed size. In each pair, one concave bank was forested and one was unforested. Stream bends with unforested concave banks had an average local migration rate three times greater than stream bends that had forested concave banks.     

Colloid migration in symmetrical non-uniform fractures: particle tracking in three dimensions

A three-dimensional model for the migration of colloids in a saturated fracture is presented, which considers the motion of colloids as a result of advection and diffusion, as well as colloid-surface interactions at the fracture walls. This model is successfully incorporated into a three-dimensional particle tracking algorithm that tracks particles within a continuum and allows consideration of the migration of colloids in symmetrical, three-dimensional, non-uniform fractures. The framework is general enough to incorporate non-local interactions that provide colloid motion relative to the fluid. The algorithm is verified against classical Taylor dispersion, and its generalization to a sorbing phase, in a uniform fracture and shows excellent agreement with theory. A simple, non-uniform fracture that has an analytically tractable velocity field is also considered, and both quantitative and qualitative comparisons are made with the uniform fracture case. The modelling of more complex fracture geometries is also discussed and a particular case is implemented within the particle tracking framework.     

Soil contamination at abandoned sawmill areas

Contamination of soil by technical chlorophenol formulation at wood preserving sites was studied. The examined soils contained 50 to 1000 mg of polychlorinated phenols (CPs), 1 to 50 mg of polychlorinated phenoxyphenols (“pre-dioxins”, PCPPs) and 0.1 to 5 mg of polychlorinated dibenzofurans (PCDFs) per kg of dry soil. CPs were found to be mobile, leaching deep into the soil, while PCPPs and PCDFs accumulated in the top soil. All three classes of contaminants were stable in soil.     

Intercomparison of reactive transport models applied to UO2 oxidative dissolution and uranium migration

Oxidative dissolution of uranium dioxide (UO₂) and the subsequent migration of uranium in a subsurface environment and an underground waste disposal have been simulated with reactive transport models. In these systems, hydrogeological and chemical processes are closely entangled and their interdependency has been analyzed in detail, notably with respect to redox reactions, kinetics of mineralogical evolution and hydrodynamic migration of species of interest.Different codes, where among CASTEM, CHEMTRAP and HYTEC, have been used as an intercomparison and verification exercise. Although the agreement between codes is satisfactory, it is shown that the discretization method of the transport equation (i.e. finite elements (FE) versus mixed-hybrid FE and finite differences) and the sequential coupling scheme may lead to systematic discrepancies.