Lake sediment phosphorus release management—Decision support and risk assessment framework

The release of phosphorus (P) from the sediments of eutrophic lakes is often associated with the proliferation of nuisance algal blooms, especially cyanobacteria. The successful implementation of management actions aimed at reducing such algal blooms requires an integrated approach, including both external and internal nutrient loads. The internal load of P can be a significant source of P for primary production, with greatest inputs occurring when lakes stratify and the hypolimnetic waters become anoxic. We reviewed the nature and characteristics of New Zealand lakes in relation to factors which affect the application of technologies to manage internal P loads within individual lakes. New Zealand's windy maritime climate causes lakes to mix more deeply than lakes in continental areas, which are characterised by relatively hot, calm summers. We assessed a range of management options which may be used to control internal P loads, and considered these in a de cision‐support framework aimed at identifying the key factors which may limit successful application. Methods to reduce P release from sediments include: physical approaches—such as artificial destratification, hypolimnetic aeration, enhanced lake flushing, and dredging/discing; and geochemical approaches—such as the application of alum and iron as flocculation agents, and other products as “capping” materials. The capping materials may be either a passive physical barrier (e.g., sand, gravel, clay) or an active barrier. The active barrier systems are generally pervious chemical or geochemical materials capable of binding contaminants by adsorption or precipitation processes. A decision‐support and risk assessment framework is provided to assist managers in the development of appropriate strategies for reducing or controlling internal P loads, and thus cyanobacteria blooms. A review of the sediment characteristics of lakes in the Taupo volcanic zone showed marked variability in sediment P content, and elevated geothermal arsenic concentrations in some lake sediments, which may affect the efficacy of chemical capping agents, indicating that site‐specific consideration of capping agent dose is required.     

Potassium alum and aluminum sulfate micro-inclusions in polar ice from Dome Fuji,East Antarctica

Water-soluble trace constituents affect the physicochemical properties of polar ice. Their structural distribution provides important insights into the formation history of ice and inclusions. We report the first finding of KAl(SO₄)₂·12H₂O (potassium alum) and Al₂(SO₄)₃·nH₂O (aluminum sulfate) micro-inclusions in the Dome Fuji ice core, East Antartica, using a micro-Raman technique. Eutectic temperatures of these water-soluble species determined using thermal analysis were −0.4 °C for potassium alum and −8.0 °C for aluminum sulfate. Although the formation process of the aluminum-bearing sulfates remains unclear, the occurrence of these salts largely depends on ice depth.     

含铬明矾局部压缩率的研究

本文运用晶体场理论计算了几种含铬明矾的自旋-晶格耦合系数G_(44)在此基础上,求得了它们的零场劈裂对键角的变化率。根据单轴压力下的EPR谱数据,获得了在这几种明矾中的(T~(3+)·6H_2O)~(3+)基团的局部压缩率,这些值都明显地小于明矾晶体的压缩率。在本文中,我们讨论了产生这种现象的原因并论证了这些局部值的合理性。由此可以看出,压力下的EPR谱是研究含顺磁离子矿物的局部结构和局部压缩率的有效手段。     

Duration of soil cadmium and lead pollution from shale-based alum production

The scope of this study is to assess the present impact from an historical emission source, in order to provide information on the duration of this metal pollution problem.The present distribution of cadmium and lead, emitted from a Swedish alumworks between 1726–1840, was studied in soils, sediments and ground water. The soil data imply that cadmium has disappeared from the surface soils during the 150 to 250 years that have passed since the emissions ceased. Lead concentrations of the soil are elevated only within 200 m from the site of the works. Further away, the lead concentrations are almost at background level. A possible explanation for this pattern, is that lead dispersed in large particles has not yet fully disintegrated and leached down the soil profile, in contrast to the smaller particles deposited further away.The metal concentrations in the ground water wells are slightly higher than the Swedish average but probably governed by the pH of the water, rather than the occurrence of large amounts of metals. Elevated lead concentrations were found in a few sediment samples in the river mouth downstream from the works. These elevated concentrations coincided with the abundant occurrence of small particles of used shale, indicating their origin.Cadmium is not found, at present, in the soil around the alumworks in concentrations substantially above background levels. Consequently, it is likely that the cadmium deposited in the area, has leached through the upper layers of the soil profile on its way to the sea sediments. Likewise, the lead concentrations in the soil beyond 200 m from the alumworks are not above background levels which indicate that losses through leaching have occurred at a rate of 0.5 to 1.5% yr⁻¹.Finally, comparisons with other long-term perspective studies give an opportunity to discuss the rate for the disappearance of an environmental problem.     

青海玛温根矿区氧化铅银矿工艺矿物学特性及分析研究

结合光学显微镜鉴定、扫描电镜、X射线能谱探针、筛析等技术手段,系统研究了青海省玛温根矿区产出的有代表性的氧化铅矿石的工艺矿物学特征。结果表明:矿石主要有价元素是Pb(2. 76%)和Ag(204. 4×10-6);矿石中铅的赋存状态较复杂,主要赋存于铅铁矾等难溶铅中,其次赋存于氧化铅、硫酸铅中,矿石中的铅矿物主要是铅矾、白铅矿、砷铅铁矾,少量方铅矿、砷铅矿等;银的赋存状态亦较为复杂,独立银矿物为硫铜银矿,含量甚微,部分银呈类质同像赋存于其他的金属硫化物中。通过偏光显微镜和扫描电镜分析发现,主要的铅矿物如铅矾、白铅矿等相互交代连生现象明显,且嵌布粒度细小,这与筛析检测结果相一致,同时矿石中As含量较高,达到了5. 43%,含砷矿物主要为毒砂、臭葱石,经X射线能谱分析,部分铅矿物与砷元素关系密切,并形成了砷铅铁矾、砷铅矿等复杂砷铅矿物。所以预测在选矿过程中,砷会随铅矿物同步富集,银的独立银矿物主要是硫铜银矿,且嵌布粒度微细,大部分银矿物以微细粒包裹态赋存于石英、褐铁矿等硅酸盐或氧化物中。根据以上研究成果,可判定该氧化铅银矿属于极难选矿石,建议采用浮选-化学选矿工艺综合回收铅、银金属的技术路线。     

矾花图像的处理及应用研究

利用数码相机定时采集沉淀池中的矾花图像，通过串口通信传输、存储到计算机；计算机对矾花图像进行数字图像处理；将处理结果应用到添加控制系统中，从而达到适量添加明矾的目的。