Heavy metal retention by soil mineral phases during a potential soil contamination by sewage sludge

The immobilization conditions of heavy metals （Ni, Cu, Zn, Pb） potentially released from sewage sludge to soils were examined. Competitive adsorption experiments, sequential extraction and analytical electron microscopic studies were performed on soils with different compositional characteristics to gain information about the interaction and association of metals with soil minerals. The results showed that Cu and Pb can be characterized by a preferred adsorption in contrast to Zn and Ni independent of initial metal concentrations, ratios, and soil composition. Precipitation is the dominating retardation process in the sample containing carbonates, but it is also characteristic of metals with inhibited adsorption in samples free of carbonate. Both Cu and Pb show high affinity towards organic matter. Differences in metal affinities towards different clay minerals show the immobilization of Cu rather by specific adsorption and that of Pb rather by ion exchange. According to the sequential extraction studies the role of ion exchange is the most important process for the retardation of Zn, and in the sample containing montmorillonite. The specific adsorption is significant mostly for Cu and Pb, and primarily in samples rich in organic matter and containing vermiculite. The co-precipitation of metals with Fe-Mn oxides is significant primarily for Cu, but in some cases Pb and Zn can be also found in this fraction. In general, the strength of immobilization for the studied metals is as follows： Cu〉Pb〉Zn〉Ni. Significantly higher metal adsorption was found by the phases in the sample containing carbonates, as well as in samples characterized by the close association of clay minerals and iron oxides. Smectite and vermiculite are the most important adsorbents in soils for all of the metals. Additionally, iron-oxides immboilize significant amounts of Cu and Zn, too.     

Characterizing Fracture Spatial Patterns by Using Semivariograms

Semivariogram is applied to fracture data obtained from detailed scanline surveys of nine field sites in western New York, USA in order to investigate the spatial patterns of natural fractures. The length of the scanline is up to 36 m. How both fracture spacing and fracture length vary with distance is determined through semivariogram calculations. In this study, the authors developed a FORTRAN program to resample the fracture data from the scanline survey. By calculating experimental semivariogram, the authors found five different types of spatial patterns that can be described by linear, spherical, reversed spherical, polynomial I (for a<0) and polynomial II (for a>0) models, of which the last three are newly proposed in this study. The well-structured semivariograms of fracture spacing and length indicate that both the location of the fractures and the length distribution within their structure domains are not random. The results of this study also suggest that semivariograms can provide useful infor     

Subsurface Airflow Induced by Natural Forcings

Subsurface airflow can be induced by natural processes,such as atmospheric or barometric pressure changes, water table fluctuations,topographic effects,and rainfall infiltration．Barometric pressure fluctuations are the most common cause of subsurface airflow,which can be significant under favourable geological conditions．This process has been studied most extensively because of its application to passive soil vapor extraction．Soil airflow induced by water table fluctuations can be significant,particularly where the fluctuations are of high frequency,for example,in tidal-influenced coastal areas．Top-ographic effects can lead to strong subsoil airflow in areas with great elevation differences．Rainfall infiltration usually produces only weak airflow.Air flow induced by these natural processes has important environmental and engineering implications．Among the different processes,airflow induced by tidal fluctuations has been studied the least,although it has exciting applications to coastal engineering projects and environmental remediation．     

Electroplating wastewater treatment technology by river sands

Electroplating waste water containing Cr(Ⅵ) was treated by using river sand as adsorbent and reductant. The effects of pH value, interaction time and Cr(Ⅵ) content on the remove of Cr(Ⅵ) in waste water were investigated. Two methods were practiced in t…     

Fate of aluminium released by sacrificial anodes – Contamination of marine sediments by environmentally available compounds

To protect their steel structures from corrosion by cathodic protection, many harbours use aluminium sacrificial anodes, which induces aluminium release and potential contamination of the surrounding waters and sediments. To study the impact on Al mobility, a natural marine sediment was artificially contaminated with aluminium from different sources: sulphate or chloride salts, or sacrificial anodes. To estimate Al mobility in sediments, single (HCl) and sequential (F6) extractions were performed; they highlighted that aluminium is poorly mobile in natural sediment (HCl-leachable: 2% and F6-leachable: 9%). Contamination by aluminium salts inhibits HCl-leachability (≤ 2%), whereas the Al F6-leachability is intensified up to 18%, suggesting that the additional aluminium is scavenged in a mobile fraction that HCl is not able to solubilise. In case of aluminium anode contamination, sediments present surging Al HCl-leachable (15%) and F6-leachable (32%) fractions, which are related to aluminium mineralogical speciation. Indeed, contrary to the Al naturally present or introduced by salts, Al released by anodes is partly bound to the acid-soluble fraction, probably because of the integration of the released Al into the calcareous deposit produced at the anodes surfaces that finally comes away and gets mixed up with the sediment. The presence of aluminium in the acid-soluble fraction of sediments could have an important environmental impact as this fraction is easily available. Indeed, Al scavenged in the acid-soluble fraction of sediments participates in enhancing Al lability near the sacrificial anodes and may affect the surrounding ecosystems.     

Transport of Metals by Hydrocarbons in MVT Deposits

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Soil Permeability Controlled by Particle–Fluid Interaction

In this paper, Atterberg limits and hydraulic conductivity tests are performed in sand samples mixed with different amounts of silt, zeolite and bentonite. The testing liquids consist of kerosene, two paraffin oils with different viscosities, distilled water and 1, 10 and 1,000 mol/m3 calcium chloride solutions. Experimental results show that soils completely lost their plasticity when are in contact with light non-aqueous phase liquids, and that the liquid limit depends on the dynamic viscosity of the fluid surrounding the particles. Also, tested soils show different hydraulic conductivity with water before and after Ca²⁺ ions are introduced in the permeating fluid, in agreement with the change in the formation Gibbs free energy and diffuse double layer theory. Finally, the influence of viscosity ratio, specific surface of particles, soil fabric and PFI on hydraulic conductivity is discussed and related to the effective particle diameter and soil void ratio.     

Experimental Study of Confining Pressure Initiated by Tectonic Force

An experimental study of the confining pressure, i.e. additional hydrostatic pressure initiated by the tectonic force is presented. The experimental progress is that the σ1 is gradually increasing from 0 in a limiting movement (ε1=0) in the σ1 direction and the speed rate of the accelerating load is 0.4 MPa*s-1 in the lateral and level directions. When σ2=σ3<200 MPa, Δσl is nearly lacking, Δσl is increasing at a high speed only when the horizontal force reaches 250-380 MPa, and Δσl almost ceases to increase at the level force of 380 MPa. It is calculated that the tectonic force can produce the confining pressure which is gradually increasing with σ2=σ3 before it reaches 380 MPa in an experiment. It is supposed that the horizontal force is almost all transformed into the confining pressure with the increase of the creep deformation of rocks.     

Evans blue removal from wastewater by rarasaponin–bentonite

The feasibility of natural bentonite and rarasaponin–bentonite for Evans blue removal from aqueous solution was studied. Rarasaponin is a natural surfactant obtained from Sapindus rarak DC was used as modifying agent for natural bentonite modification. Adsorption experiments were conducted in a batch system at various temperatures. Several temperature-dependent isotherm models (Langmuir, Freundlich, Sips and Toth) were used to represent equilibrium data. It was found that Toth model represents the adsorption equilibrium data better than other models. Kinetic data were best represented by the pseudo-first order model. The controlling mechanism of the adsorption of Evans blue onto natural bentonite and rarasaponin–bentonite was physical adsorption.     

Rare Earth Element Transport and Deposition by Hydrothermal Fluids

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Accumulation of cadmium by bivalves in the Pacific Northwest

Bivalves （mussels, scallops, oysters）, from the Pacific Northwest coast of British Columbia, Canada, contain high levels of cadmium, in some cases exceeding 7 μg/g wet weight of tissue. We have for the past 5 years, attempted to determine the source of this cadmium to these filter-feeding invertebrates, with our objective being that we would then be able to advise where bivalves could be cultured for human consumption such that cadmium accumulation by the bivalve was minimized. Our studies have indicated that there are distinct regional and temporal variations in bivalve cadmium residues. Some patterns in cadmium accumulation did occur, e.g. for bivalves located on the most outer westcoast of British Columbia, cadmium residues demonstrated some seasonal dependence. In general, however, variations could not be readily ascribed to food sources （oceanic versus terrestrial）, or to abiotic factors such as salinity and turbidity. Cadmium residues in oysters were negatively correlated with temperature supportive of a seasonal influence on measured cadmium concentrations.     

Desorption of zinc by kaolin from Suzhou, China

Heavy metals in soils may adversely affect environmental quality. This paper studied the influence of copper concentration, pH, temperature, and the ratio of solid to solution on the desorption of Zn in kaolin from Suzhou, China in a background solution of 0.01M CaC12 by batch extraction experiments. At 0, 5, 50, 100 mg/L Cu concentrations, for each 0.5, increase in pH between about 1.80 and 3.04 percent desorption decreasing by 3.80%, 13.87%, 9.97%, and 7.65%, respectively. The pH 50 （ pH at 50% Zn desorption） was found to follow the sequence of Cu （5mg/L, pH 50=2.60）.