Levels Of Copper Contamination Research Articles

Chemical stress induced by copper: examination of a biofilm system

Biofilm systems have been widely used in wastewater treatment plants. However, little information is available on the impact of toxic chemicals on the performance of fixed film systems. This study was aimed at evaluating the impact of copper on a biofilm system by examining a variety of parameters, including reactor pH, DO, substrate concentrations, secretion of extracellular polymeric substances (EPS), and copper removal and accumulation. The microbial communities in the biofilms were also examined using automated ribosomal intergenic spacer analysis (ARISA). Four rotating drum biofilm reactors were used to produce biofilms. One reactor was used to produce biofilms under copper free conditions; while the others were used to produce biofilms grown under three different copper contamination levels, namely 100 ppb, 200 ppb, and 500 ppb, for a prolonged period. The following results were obtained: (1) biofilm reactor performance was not significantly impacted as demonstrated by the pH, DO, substrate removal, and total solids in the effluent; (2) however, copper contamination inhibited EPS production in the biofilms; (3) copper removal efficiencies of 25-31% were obtained for the three copper contamination levels studied; (4) fixed films functionalized as a reservoir to accumulate more copper over time; and (5) copper contamination selected for specific species that were able to tolerate this stress and that may contribute to its remediation.

Evaluation of Cinygmula (Ephemeroptera: Heptageniidae) Drift Behavior as an Indicator of Aqueous Copper Contamination

We designed an in situ assay for investigating macroinvertebrate drift behavior in response to a point source of environmental pollution. As a model, we used Cinygmula nymphs to assess both the presence and level of copper contamination in a stream that was polluted with effluent from an abandoned copper mine. The study showed that Cinygmula exhibited increased tendency to drift with increased exposure to aqueous copper. Cinygmula drift behavior exhibited graded responses to increasing concentrations of aqueous copper up to and including 78 ppb. The results indicated that a simple yet sensitive in situ bioassay could be used to detect environmentally important levels of copper contamination in Haggarty Creek.

Land inputs, behaviour and contamination levels of copper in a ria estuary (NW Spain).

Copper concentrations were measured in the sediments and dissolved phase of the water column in the Lérez Estuary (Pontevedra Ria, Galicia), NW Spain, and in the freshwater-sewage inputs to the estuary. Dissolved copper fluxes in the estuary were quantified. Results show that the freshwater end-member in the Lérez Estuary has minimal copper contamination ([Cu](Dissolved)=7+/-4 nM, Sediment Enrichment Factor=1) and the source of dissolved copper inputs is localized in the saline end-member ([Cu](Dissolved)=20-55 nM, Sediment Enrichment Factor=6-7). A non-conservative behaviour of dissolved copper showing a net addition during estuarine mixing was observed. The budgetary calculations and the copper sediment distribution suggest that the major copper input to the estuary-ria system is located at the Marín-Placeres transect, playing an important role in the net addition of copper within the estuarine mixing. The importance of upwelling in the renewal of the Galician coastal waters and dilution of continental inputs is discussed.

Detection of low-level copper contamination in p-type silicon by means ofmicrowave photoconductive decay measurements

In order to achieve a better understanding of the behaviour of copperin p-type silicon, studies of the recombination of copper were carriedout by the microwave photoconductive decay measurement method (μPCD) using high-intensity bias light. It was observed that in the presence of smalloxygen precipitates, high-intensity light could be used to activate precipitation ofinterstitial copper. It is suggested that high-intensity light changes the charge state ofinterstitial copper from positive to neutral, which enhances the precipitation.The precipitation follows Ham’s kinetics and results in an increase in therecombination rate, which is detectable even with very low copper concentrations.This phenomenon can be used to detect low levels of copper contamination by theμPCD method. In addition, it was observed that out-diffusion as well as in-diffusionof interstitial copper could be affected by an external corona charge. Thus, it issuggested that copper atoms do not form stable bonds at the Si–SiO2 interfaceafter out-diffusion from bulk silicon.

Copper in Silicon: Quantitative Analysis of Internal and Proximity Gettering

The behavior of copper in the presence of a proximity gettering mechanism and a standard internal gettering mechanism in silicon was studied. He implantation-induced cavities in the near surface region were used as a proximity gettering mechanism and oxygen precipitates in the bulk of the material provided internal gettering sites. Moderate levels of copper contamination were introduced by ion implantation such that the copper was not supersaturated during the anneals, thus providing realistic copper contamination/gettering conditions. Copper concentrations at cavities and internal gettering sites were quantitatively measured after the annealings. In this manner, the gettering effectiveness of cavities was measured when in direct competition with internal gettering sites. The cavities were found to be the dominant gettering mechanism with only a small amount of copper gettered at the internal gettering sites. These results reveal the benefits of a segregation-type gettering mechanism for typical contamination conditions.

Influência da Mineração no Incremento e na Disponibilidade Geoquímica de Cobre em Sedimentos Fluviais - O Caso das Minas do Camaquã, RS, Brasil.

This work presents an analysis of copper contamination levels and copper availability in stream sediments of the João Dias Creek in the Minas do Camaquã region, caused by mineral exploitation. Fluvial sediments are predominantly sandy with less than 1% fine fraction (< 63µm), which leads to negligible amounts of environment available metals. The mean copper content in the CH3COONH4 (1M) exchangeable fraction of stream sediments showed an average availability around 7% in the region affected by mining operations. In background area this ratio is less than 2% and up to 13% in the sample point situaded downstream the sludge dam. The mean copper content in the HNO3 (0,1N) extractable fraction of stream sediments showed an average availability around 55% in the region affected by mining operations. In background area this availability is around 10% and reached 90% in the sludge dam. The pollution levels stablished by USEPA for sediments, the contamination factor (CF) and the geoaccumulation index (Igeo) determined in the fine fraction indicated a high copper contamination in the drainage segments affected by mining effluents.

Production and Diagnostic Measurements of Kilovolt High-Density Deuterium, Helium, and Neon Plasmas

This paper reports successful production and diagnostic measurements of kilovolt high-density plasmas of deuterium, deuterium-helium mixtures, helium, and neon. Particular attention was given to obtaining a systematic understanding of the electron and ion heating and cooling processes, as well as the attendant equilibration processes. These plasmas typically psosessed 1<Te<10 keV, 2×1019 <ne<1020 cm−3, 2×1018 <ni<1020 cm−3, copper contamination levels of nCu∼5×1017 cm−3, energy densities ∼105 J/cm3, and effective lifetimes ∼0.5 μsec. Diagnostic measurements were made with absolute time-resolved x-ray and neutron detectors, magnetic and electric probes, and high-speed visible photography. The plasmas were generated in a coaxial discharge tube, with the ions being heated primarily through collapse of the quasicylindrical current sheet, in a manner reminiscent of the linear pinch effect. The electrons rapidly achieved kilovolt temperatures via collisions with the energetic ions; radiation cooling of the electrons was observed, late in time, particularly for those plasmas consisting of high-Z ions.

The Effect of Heat Treatment on the Pro-Oxidant Activity of Copper in Milk

Summary Copper added to milk before heat treatment at 121° C. for 15min. or 104° C. for 20min. causes lower rate of disappearance of ascorbic acid on subsequent incubation than is caused by copper added after heating. The reverse effect occurs in samples heated at 85° C. for 20min. Approximately straight line relationships are obtained when the amounts of reduced ascorbic acid destroyed above the control value in milk samples to which the copper is added after heating are divided by the amounts destroyed above the control value in similar samples to which the copper is added before heating, and these values plotted against the amount of copper added. Extrapolation of the lines to zero addition of copper affords a quantitative estimate of the effect of slight copper contamination occurring before heat treatment, as compared to the same level of copper contamination occurring after heat treatment. Casein-copper and lactalbumin-copper mixtures heated at 121° C. for 15min., when added to ascorbic acid solutions, cause a lower rate of loss of reduced ascorbic acid than do the unheated mixtures. If copper is added to previously heated protein solutions, an effect on reduced ascorbic acid oxidation intermediate between heated and unheated samples occurs. These data furnish evidence that high-temperature heat treatment of milk reduces the pro-oxidant effects of milk copper and allows an interpretation of the mechanisms to be advanced. Extrapolation to zero of the straight lines obtained on plotting the percent ascorbic acid destroyed against the copper added to milk samples subsequently heated at 121° C. for 15min. yields values for copper approximately twice as great as were obtained by chemical analysis.