Economies of scale in global iron-making

In this paper, we investigate the presence of economies of scale in the global iron-making industry for integrated steel plants, iron making being the first stage in the steel-making process. Iron making depends on basic commodities, such as iron ore, coke and various forms of energy, required in the operation of the blast furnace, which can be classified as essential inputs and used in fixed proportions to produce iron. A generalized Leontief cost function is estimated using panel data for 69 integrated plants, such a specification being appropriate for technologies with essential inputs that are used in fixed proportions in production. A significant scale effect is observed due to the existence of fixed costs and a linear dependence of the cost function on production. Under a simple linear cost function, a rough estimate of the breakeven scale of plant, where costs equal revenue, is 4.5 Mt per year. Competitiveness, as measured by the ratio of plant average cost per tonne to best practice cost per tonne, can be shown to be positively related to the scale of production as well as the cost of essential inputs. Therefore, low-cost producers are also often producers with low raw material costs and production levels below the estimated breakeven scale of operation. Labor costs, although significant, are comparatively less important as a driver towards low costs.     

Biomonitoring of heavy metals by pollen in urban environment

Abstract Industrial development and consumption of petroleum products leads to increase air pollution levels especially in urban and industrial areas. Heavy metal components associated with air pollutants have far reaching effects with respect to economic and ecological importance of pollens. The pollens are male reproductive organs of the plant and travel through air from flower to flower for pollination purpose. During this period they are exposed to air pollutants. Present investigation thus pertains to study of effect of air pollutants on pollens especially biosorption and bioaccumulation of heavy metals. The pollens of three commonly occurring plants namely Cassia siamea, Cyperus rotundus, Kigelia pinnata have been studied from the NH-6 of Nagpur city, India. The pollens exposed to polluted air showed the presence of higher concentrations of Ca, Al and Fe as compared to unexposed pollens. Higher concentration of these metals was observed in Cyperus rotundus followed by Cassia siamea and Kigelia pinnata. These results indicate that pollens act as good indicator of air pollution giving results in short time of exposure of 5–10 h. Apart from this, it is also reported that some of these metals play crucial role in the metabolic activity in pollens for example Calcium is necessary for growth of pollen tube and other metabolic activities in pollens. The presence of these metals in pollens may also enhance the allergenicity of the pollens. Similarly accumulation of heavy metals may also deteriorate the quality of pollen for their economical use. The viability of pollen is also affected by these pollutants in sensitive species leading to impairment of their fertility.     

城市污泥中重金属有效态分布特征研究

以沈阳市北部污水处理厂剩余活性污泥为研究对象,对污泥中重金属Cd,Pb,Cu,Zn的含量及其形态分布特性进行分析。结果表明:污泥中4种重金属的含量基本符合国家相关控制标准(GB 18918-2002和CJ248-2007)。采用8种提取剂(0.05 mol/L EDTA,0.01 mol/L CaCl2,0.01 mol/LCa2(NO3)2,0.1 mol/L NaNO3,1 mol/L NH4OAC,0.43 mol/LHAC,0.05mol/L NaHCO3和0.05 mol/L Tris-HCl)分别对污泥中重金属的螯合态,中性交换态,酸溶态,碱溶态和蛋白质结合态进行分离分析。结果表明:4种重金属螯合态存在的比例较大,分别占各重金属总量的5.9%~27.2%,其次为酸溶态和中性交换态,而以碱溶态和蛋白质结合态形式存在的比例较少,除Cd外均低于1%。污泥中Cd和Pb具有较高的活性,而Cu,Zn在碱性污泥中主要以稳定态存在。     

漓江沉积柱重金属垂向分布特征及污染评价

对桂林漓江3个采样点沉积柱状沉积物中主要重金属元素(Cd、Cr、Cu、Zn、Pb、As和Ni)的垂向分布进行了测定。结果表明:7种重金属元素具有相似的垂向变化特征;横向上表现为靠近市区的含量高远离,市区的含量低。地积累指数评价结果显示,远离市区的沉积柱7种金属污染程度较轻,仅有Cd和Ni属于无～中污染程度。临近市区的沉积柱形成污染的元素为Cd、Cu、Zn、Pb和As,主要集中在底层和次表层。     

天然藻类吸附重金属的研究

传统的重金属废水处理技术存在耗能高、运行成本高及存在二次污染的问题等诸多劣势;而天然海藻由于其来源广、产量大,在处理重金属废水方面存在较多的优点。介绍了藻类处理重金属离子的研究背景、现状,阐述了藻类处理重金属的优点、机理,重点介绍了海藻处理废水过程中的各种影响因素,并对海藻处理废水的应用前景进行了展望。     

Do earthworms impact metal mobility and availability in soil? - A review

The importance of earthworms to ecosystem functioning has led to many studies on the impacts of metals on earthworms. Far less attention has been paid to the impact that earthworms have on soil metals both in terms of metal mobility and availability. In this review we consider which earthworms have been used in such studies, which soil components have been investigated, which types of soil have been used and what measures of mobility and availability applied. We proceed to review proposed reasons for effects: changes in microbial populations, pH, dissolved organic carbon and metal speciation. The balance of evidence suggests that earthworms increase metal mobility and availability but more studies are required to determine the precise mechanism for this.     

Heavy metal distribution and speciation in the Northern Adriatic Sea

In the present study the concentrations of cobalt, copper, iron, manganese, zinc were analysed and the speciation of copper and zinc performed, with a summer and winter sampling, for two areas in the Northern Adriatic Sea and crossing at the farthest zones of the Po river-sea water interface. Results show that when salinity increases the concentrations of all investigated metals (with the exception of cobalt) present some degree of biogeochemical cycling. Copper is the element whose dissolved phase has the highest importance in metal transport across the salinity gradient. Results of speciation analysis demonstrate that the presence of excess amounts (5-8 fold) of unbound ligands confers a buffering capacity for potential inputs of dissolved metals into the Northern Adriatic Sea. The speciation of both copper and zinc in the dissolved phase was dominated by organic complexation.     

Heavy metals contents of roadside mosses in the northern and south-eastern regions of Nigeria

Levels of lead, zinc, cadmium, copper and nickel were determined in roadside moss samples within towns in the northern and south-eastern regions of Nigeria. Average lead level in the south-east (59 ppm) was higher than the average for the northern region (44 ppm). Average levels of zinc, cadmium, copper and nickel did not differ significantly between the two regions, with overall averages for the entire study area being 50.9, 1.2, 11.3 and 5.6 ppm for these metals. Lead levels were poorly correlated with those of the other metals, indicating that automobile emissions may not be the main source for these metals in the moss. In comparison with a previous study of the south-west region, the results indicate a generally slightly higher level of metal pollution in the south-west region than in both the northern and south-eastern regions.     

Metal accumulation and performance of nestlings of passerine bird species at an urban brownfield site

The use of passerine species as bioindicators of metal bioaccumulation is often underutilized when examining the wildlife habitat value of polluted sites. In this study we tested feathers of nestlings of two common bird species (house wren and American robin) for accumulation of Pb, Zn, As, Cr, Cu, Fe in comparison of a polluted, urban brownfield with a rural, unpolluted site. House wren nestlings at the study site accumulated significantly greater concentrations of all target metals except Zn. At the polluted site we found significant species differences of metal concentrations in feathers, with house wrens accumulating greater concentrations of Pb, Fe, and Zn but slightly lesser accumulations of Cr and Cu than American robins. Although house wren nestlings demonstrated significant accumulation of metals, these concentrations showed little effect on size metrics or fledge rates during the breeding season compared to nestlings from the control site.     

Habitat type-based bioaccumulation and risk assessment of metal and As contamination in earthworms, beetles and woodlice

The present study investigated the contribution of environmental factors to the accumulation of As, Cd, Cu, Pb and Zn in earthworms, beetles and woodlice, and framed within an exposure assessment of the European hedgehog. Soil and invertebrate samples were collected in three distinct habitat types. Results showed habitat-specific differences in soil and invertebrate metal concentrations and bioaccumulation factors when normalized to soil metal concentration. Further multiple regression analysis showed residual variability (habitat differences) in bioaccumulation that could not be fully explained by differences in soil metal contamination, pH or organic carbon (OC). Therefore, the study demonstrated that in bioaccumulation studies involving terrestrial invertebrates or in risk assessment of metals, it is not sufficient to differentiate habitat types on general soil characteristics such as pH and/or OC alone. Furthermore, simple generic soil risk assessments for Cd and Cu showed that risk characterization was more accurate when performed in a habitat-specific way.