Physicochemical contamination

A mass of evidence seems to confirm that the mixing rate of radiocarbon in the atmosphere is rapid, and that with respect to its radiocarbon content the atmosphere can be considered as a homogeneous entirety. The contamination of samples with matter from an extraneous source can nevertheless invalidate this assumption. Two types of contamination can be differentiated physicochemical contamination and mechanical intrusion. There are two forms of physicochemical contamination. One is due to the dilution of the concentration of radiocarbon in the atmosphere by very old carbon, practically depleted of radiocarbon, released by the combustion of fossil fuel, such as coal and oil. The other is by the contamination with radiocarbon produced by nuclear bomb tests during the 1950s and later in the twentieth century. The uncertainties introduced by these forms of contamination complicate the interpretation of data obtained by the radiocarbon dating method and restrict its accuracy and the effective time range of dating. 

Skin. The skin may become contaminated accidentally or, in some cases, materials may be deHberately appHed. Skin is a principal route of exposure in the industrial environment. Local effects that are produced include acute or chronic inflammation, allergic reactions, and neoplasia. The skin may also act as a significant route for the absorption of systemicaHy toxic materials. Eactors influencing the amount of material absorbed include the site of contamination, integrity of the skin, temperature, formulation of the material, and physicochemical characteristics, including charge, molecular weight, and hydrophilic and lipophilic characteristics. Determinants of percutaneous absorption and toxicity have been reviewed (32—35,42,43,46—49). 

Deposition commonly reflects a combination of physicochemical processes and localized effects. It may occur through fouling as a result of contamination by process materials, perhaps plus scaling from the supersaturation of dissolved salts, and coupled with some active under-deposit corrosion. As a consequence, deposits forming within a boiler are almost never single mineral scales but typically consist of a variable mix of scale and corrosion debris, chemical treatment residuals, process contaminants, and the like. 

Many medicines contain a wide variety of ingredients, often in quite complex physicochemical states, included to create formulations which are efficacious, stable and sufficiently elegant to be acceptable to patients. Should microbial contaminants survive manufacture, or enter during storage or use they are likely to meet conditions which are often conducive to survival and even replication of an appreciable assortment of non-fastidious bacteria, ftingi and yeasts, and microbial spoilage may ensue unless steps are taken to control it. Microbial spoilage may include ... 

The main parameters that affect the cost-effectiveness of soil washing include the physicochemical parameters of the soil (grain size distribution, cation exchange capacity, percentage of silt, clay, or organic matter), and the type and concentration of contaminants. 

For the studies summarized in Table I and discussed in the following sections of the text, physicochemical properties (including partition coefficients) were collected from a variety of reference documents or estimated according to available equations (Table III). Acceptable daily doses were calculated from toxicological data (Table III). When more than one equation was available, judgment was used to determine which to apply. Table III excludes those contaminants footnoted in Table I. A default value of 1.0 was adopted for K for the first nine compounds of Table III (4). For PBBs, the value of log KQC was calculated from the solubility in creek water (7.96 x 10-4 pM), according to the equation (1,3)1... 

The model is composed by different equations which in all cases can be used in unsubscribed format in a basic language program. An important point to highlight is that Qwasi takes into account both steady and unsteady state solutions for the equations for systems involving contamination of lakes (or rivers). The equations considered by Qwasi involve more than 15 physicochemical processes (such as partitioning, sediment transport, deposition, etc.) to estimate the fate of the studied system. These processes and the main involved variables and parameters are summarized in Fig. 2. 

Chemical remediation refers to the application of various minerals or chemicals to adsorb, bind, precipitate or co-precipitate trace elements and heavy metals in soils and waters thereby reducing their bioavailability, toxicity, and mobility. In situ immobilization refers to the treatment of contaminants in place without having to excavate the soils or waste, often resulting in substantial cost savings. However, in situ immobilization or extraction by these physicochemical techniques can be expensive and are often only appropriate for small areas where rapid and complete decontamination is required. 

There are a variety of analytical methodologies developed for the analysis of emerging contaminants selected for this chapter. In almost all cases, the instrumental analysis is based on the use of GC or LC coupled to MS or MS-MS. The selection of one or another technique depends primarily on the physicochemical properties of the compounds. We summarize the more recently developed methodologies for each of the families (Table 1). 

Treatment of dye-contaminated wastewater discharged from the textile and other dye-stuff industries is necessary to prevent contamination of soil and surface and ground water. Currently, there are several physicochemical and biological methods... 

Abstract Analysis of adequate physicochemical mechanisms of chemical contamination... 

Keywords Contamination, physicochemical mechanisms, copper smelter, Karabash ecosystem. 

S., Vatter, S., Chahbane, N., Lenoir, D., Schramm, K.W. and Scherer, G. (2005) Biological activity and physicochemical parameters of marine halogenated natural products 2,3,3, 4,4, 5,5 -heptachloro-l -methyl-1,2 -bipyrrole and 2,4,6-tribromoanisole. Archives of Environmental Contamination and Toxicology, 48, 1-9. 

---