Unexpected behavior of Zn,Cd, Cu,and Pb in soils contaminated by ore processing after 70 years of burial

Environmental Chemistry Letters - Heavy metals in contaminated ore processing areas present a risk of contamination of waters and life. Therefore, the most mobile fractions of metals, which can be...     

Assessment of elemental composition and properties of copper smelter-affected dust and its nano- and micron size fractions

A comprehensive approach has been developed to the assessment of composition and properties of atmospherically deposited dust in the area affected by a copper smelter. The approach is based on the analysis of initial dust samples, dynamic leaching of water soluble fractions in a rotating coiled column (RCC) followed by the determination of recovered elements and characterization of size, morphology and elemental composition of nano-, submicron, and micron par ticles of dust separated using field-flow fractionation in a RCC. Three separated size fractions of dust (<0.2, 0.2–2, and >2 μm) were characterized by static light scattering and scanning electron microscopy, whereupon the fractions were analyzed by ICP-AES and ICP-MS (after digestion). It has been evaluated that toxic elements, which are characteristics for copper smelter emissions (As, Cu, Zn), are accumulated in fraction >2 μm. At the same time, up to 2.4, 3.1, 8.2, 6.7 g/kg of As, Cu, Zn, Pb, correspondently, were found in nanoparticles (<0.2 μm). It has been also shown that some trace elements (Sn, Sb, Ag, Bi, and Tl) are accumulated in fraction <0.2, and their content in this fraction may be one order of magnitude higher than that in the fraction >2 μm, or the bulk sample. It may be assumed that Sn, Sb, Ag, Bi, Tl compounds are adsorbed onto the finest dust particles as compared to As, Cu, Zn compounds, which are directly emitted from the copper smelter as microparticles.

     

Accelerated fractionation of heavy metals in contaminated soils and sediments using rotating coiled columns

A new approach to performing an accelerated sequential extraction of trace elements from solid samples has been proposed. It has been shown that rotating coiled columns (RCC) earlier used in counter-current chromatography can be successfully applied to the dynamic leaching of heavy metals from soils and sediments. A solid sample was retained in the rotating column as the stationary phase under the action of centrifugal forces while different eluents (aqueous solutions of complexing reagents, mineral salts and acids) were continuously pumped through. The procedure developed is time saving and requires only 4-5 h instead of the several days needed for traditional sequential extraction (TSE), complete automation being possible. Losses of solid sample are minimal. In most cases the recoveries of readily bioavailable and leachable forms of Pb, Zn, and Cd are higher, if a dynamic extraction in RCC is used. Since naturally occurring processes are always dynamic, continuous extraction in RCC may help to estimate the contents of leachable forms and their potential risk for the environment more correctly than batch TSE. The Kersten-Foerstner and McLaren-Crawford leaching schemes have been compared, the former has been found to be preferable.     

Continuous-flow fractionation of trace metals in environmental solids using rotating coiled columns. Some kinetic aspects and applicability of three-step BCR leaching schemes

The applicability of the three-step BCR leaching scheme to the continuous-flow fractionation of trace metals (TM) using rotating coiled columns (RCC) has been investigated taking soil and sediment reference samples (SRM-2710, CRM-601, BCR-701) as examples. A particulate sample was retained in the rotating column as the stationary phase under the action of centrifugal forces while different eluents, used according to the original and optimised BCR protocols, were continuously pumped through. The whole procedure required 3-4 h instead of at least 50 h needed for the traditional sequential extraction. It has been shown that in comparison with batch sequential extraction procedures (SEP), the recoveries of Cd, Zn, Cu, and Pb at the first stage (most mobile and potentially dangerous acid soluble forms) are somewhat higher, if a dynamic extraction in RCC is used. Nevertheless, the distribution patterns for TM in the first two leachable fractions (acid soluble and reducible forms) are similar in most cases. Since no heating is used in RCC, the recoveries of TM at the third stage (when hydrogen peroxide is applied to oxidize the organic matter) may be incomplete and matrix-dependent. The effect of eluent volume and flow rate on the recovery of TM in different forms has been investigated. It has been shown that the kinetics of heavy metal leaching vary significantly with samples. Hence, investigating the elution profiles can provide additional important information for risk assessment of TM mobilization.     

Dynamic studies on the mobility of trace elements in soil and sediment samples influenced by dumping of residues of the flood in the Mulde River region in 2002

In the analysis of soil samples, batch sequential extraction procedures are traditionally used for the fractionation of trace elements to access their mobility and potential risk for the contamination of groundwater. In the present work a continuous-flow technique has been used that enables not only the fast and efficient leaching of trace elements but as well as time-resolved studies on the mobilization of arsenic and selected heavy metals in different forms to be made. Rotating coiled columns (RCC) earlier used mainly in countercurrent chromatography have been successfully applied to the dynamic leaching of heavy metals from soils contaminated by flooding sludge's. The sample was retained in a PTFE rotating column as the stationary phase whereas aqueous solutions were continuously pumped through. The contents of elements were determined by on-line coupling of RCC and inductively coupled plasma atomic emission spectrometry (ICP-AES). This enables real-time data on the leaching process to be obtained. Dynamic and traditional batch procedures were compared. It has been shown that the aqueous elution under centrifugal forced conditions is much more effective for the mobilization of heavy metals. Hence, the dynamic leaching is characterized by a substantially more intensive interaction between solid and water and is besides substantially more time-saving than the conventional batch procedure. The RCC procedure was also employed for preliminary leaching studies with a simulated "acid rain". In comparison with the water leaching, the mobilization of heavy metals and arsenic from soil samples with employment of simulated acid rain as eluent was less effective.     

Effects of the <Emphasis Type="Italic">Astacus astacus</Emphasis> L. Population on Biomass of Macrophytes in a Fresh Water Body

In experiments performed in aquariums, the daily consumption of Chara vulgaris alga by crayfish (Astacus astacus L.) has been determined. These quantitative data have been used to make a prognosis of the effect of the A. astacus population on the biomass of macrophytes in Lake Berezovo (Pskov oblast). The density of the crayfish population and the biomass of higher aquatic vegetation in the lake have been determined in field studies. Extrapolation of the results of laboratory experiments to a natural water body has shown that crayfish are capable of controlling no less than 40% of submersed macrophytes in the area used by their population.__________Translated from Ekologiya, No. 4, 2005, pp. 300–305.Original Russian Text Copyright © 2005 by Kholodkevich, Shumilova, Fedotov, Zhuravlev.