Substantial contamination

Similar to most Hg sampling methods, sampling sediments and soils require care in avoiding contamination artifacts due to improper sample handling. However, because Hg concentratiorrs are much higher in soUd matrices than in water, if corrrmonly accepted trace-metal protocols are used, substantial contamination artifacts should be exceedingly rare. Also, because sediment Hg concentration profiles... 

The extensive use of phthalates as plasticizers in various materials (furniture, plastics, electronics equipment, textiles, etc.) has led to the widespread and substantial contamination of the indoor environment, e.g., air and dust [3, 96, 97]. Indoor environment and dietary intake are of special concern for the increasing... 

The Rio Pilcomayo is a major river that originates in Bolivia and forms part of the boundary between Paraguay and Argentina. The water and sediments in the river are substantially contaminated with arsenic from the Potosi mines in Bolivia (Hudson-Edwards et al., 2001), 245. The arsenic content of Rio Pilcomayo actually increases from 65 pg L-1 at 10.2km downstream from the mines to 100 pg L-1 at about 151 km downstream (Hudson-Edwards et al., 2001), 240, 244. The arsenic increase may be due to a decrease in pH (from 10.3 to 8.42), increased oxidation of the river sediment, and increased activity of sulfide-oxidizing bacteria (Hudson-Edwards et al., 2001), 244-245. 

Zhu et al. (2004) reported the concentrations of 10 PAHs in four bodies of water in Hangzhou, China (July and November 1999 2002). The maximum levels of PAHs in the water bodies (34.4-67.7 pgl-1) were found in July, while significantly lower PAH concentrations (4.7-15.3 pgl-1) were measured in November. The measured PAH concentrations in sediments and soils, runoff water, and air particles were 224-4222 ngg-1, 8.3 pgl-1 and 2.3 pgm-3, respectively. Clearly, such substantial contamination may lead to acute toxic effects on aquatic organisms. However, the erosion of soil material does not contribute significantly to the contamination of sediments. The atmospheric PAH deposition to water bodies in the city area of Hangzhou was estimated to be 530tons/a, while the contribution of surface runoff water was... 

The data for the c = 0.001 M samples were less reproducible than those for c = 0.01 M. Of the eight micrographs obtained, two did not give clearly defined lamellar regions at all, and two of the others showed substantial contamination by ice crystals. For each individual micrograph, the -values obtained by the five different analyses were closely grouped (in the example case, all the investigators... 

There are essentially three classes of chlorinated hydrocarbon insecticides, as shown in Table III. With the present methodology, occasional traces of some of these compounds have been found in unexpected places. As a result, the agricultural application of this group of compounds has been cited as being responsible for substantial contamination of our environment. 

Widespread substantial contamination of the environment has arisen primarily from the massive use of the persistent chlorinated hydrocarbon pesticides. The extent and significance of this contamination is only partly known. Our limited knowledge is most apparent in two areas. First, there is no organized environmental monitoring and human surveillance system to provide comprehensive and representative data about the locations, amounts, and trends of this contamination second, we are technically unprepared to predict the significant long term effects of this contamination on animal and human life. 

In conclusion, it may be stated that solid-solution formation represents an exceptionally troublesome situation in analysis in that substantial contamination may be present even at equilibrium. Aging can help to reach homogeneous equilibrium, but whether the purity of the precipitate is better or worse after aging depends on the direction from which equilibrium is approached. 

Traditionally, human LDLs have been defined as those lipoproteins isolated in the density interval between 1.063 g/ml > LDL > 1.019 g/ml. This density interval may be too broad, however, because a substantial contamination with apolipoproteins other than apoB may be present on those lipoproteins at the two extremes of this density range the contaminating apolipoproteins are principally apoE (present on IDEs and HDLs at the low- and high-density extremes of this density interval, respectively) and apo(a) [present on Lp(a) at the high-density extreme]. This contamination was almost absent in the more tightly defined LDL fraction lying between 1.024 and 1.050 g/ml (Chapman et al., 1988). However, it is possible that loosely associated apolipoproteins are normally bound to LDLs in plasma and are subsequently lost during the multiple flotation steps involved in lipoprotein isolation (Mahley and Holcombe, 1977). 

At this stage the pyrrole and aqueous solution are substantially contaminated with black polymeric material. 

The First Study. Forest-applicator exposure to MSMA and cacofirst studied by Tarrant and Allard (9). They collected individual urine samples on Monday mornings ari7 Friday afternoons for 9 consecutive weeks from five applicators (each using a different combination of application method and chemical) and one control. Workers were supplied with clean clothes daily, including two pair of cotton gloves (to be changed at noon, or earlier if one pair became substantially contaminated with herbicide). Complete data were obtained for weeks 2, 3, 4, 7, and 8 (except for the injection hatchet-cacodylic acid combination, which was not included in the analysis). 

A modified (see above) 1-L three-necked flask equipped with addition funnel and Teflon-coated stirrer bar is charged with 10.07 g (20.0 mmol) of Fe3(CO)i2> capped with a rubber septum, and flushed with nitrogen before adding THF (125 mL). The flask is placed in a Dry Ice-acetone bath, and the solution of sodium naphthalene is transferred through a cannula into the 200-mL addition funnel. This solution is added slowly over a period of 1 h to the chilled, well-stirred solution of Fe3(CO)i2 in THF. This order of addition is essential reversal of the indicated order leads to substantial contamination of the product by unidentified side products. The resulting mixture is stirred for an additional 2h before it is permitted to warm to ambient temperature. The flask is then transferred to the dry box, and the contents are concentrated under vacuum to dryness. The remaining dark red-brown solid is rinsed with three 200-mL portions of pentane and dried under vacuum once again. The isolated yield of Na2[Fe3(CO)u] is 10.2g [98%f based on Fe3(CO)j2]. Approximate elapsed time for total synthesis is 4h. 

There is a long history of human exposure to lead, although the relative importance of the different pathways of lead intake may have altered over recent decades. Widespread use was made of lead during the time of the Roman Empire such uses included the lining of aqueducts and the fabrication of water pipes and cooking utensils, [1]. It is likely that both food and drink will have been substantially contaminated with lead and adverse health effects may have resulted. 

It is worth to notice, that this cahbiation curve is obtained for SNARF-1 dextran/ urease capsule in pure water without substantial contamination of aity salt, which could bulFer the systems and spoil truly picture for urea detection. We carried out experiments to build a similar calibration curve in the presence of the 0.001 M TRIS-maleate buffer (were used solutions with the pH 6.5 and 7.5) but it resulted in overwhelming effect of pH buffering. Buffering the solution eliminates the pH change caused in a course of enzymatic reactions. Thus, it sets a hmit for detection of urea concentration using SNARF-l-dextran/urease capsules. However the calibration in conditions of particular experimental system is reasonable at salt free solution assumption. Summarizing, one can state the presented in Fig. 20.7 calibration curve as suitable for estimation of urea concentrations in-situ in water solutions. 

Most plant species appear to have a limited capacity to absorb fluorine, even from contaminated soils [237] and the fluorine content of uncontaminated plant material is normally low enough to make the development of fluorosis in livestock unlikely. A number of Australian grasses analysed by Harvey [238], some of which had been grown in areas irrigated by water substantially contaminated with fluoride, were found to contain fluorine levels restricted to the range 1 to... 

The results indicate substantial contamination of the treated soil with respect to every element determined with the exception of boron. This is understandable in view of the fact that this particular sludge did not contain a high level of boron and any contamination with boron would, in any case, tend to be removed by leaching with rainwater. 

In general, the results of these experiments suggest that, while application of municipal compost at rates up to 100 tonnes/ha can lead to substantial contamination of the soil with boron, copper and zinc and to significant effects on the uptake of these elements by a number of vegetable crops, a phytotoxic... 

To summarise our consideration of the consequences of the substantial contamination of soils which has already occurred, particularly in urban and industrial areas, we can conclude that a general enhancement of the levels of potentially toxic trace elements in plants grown in urban areas could lead to deleterious effects both on the plants and on the health of animals or humans eating them. The enhancement of trace-element levels in soils resulting from contamination can also have effects on biochemical processes occurring in the soil, and Tyler and co-workers [359] have reported increased nitrate accumulation in soil in which the cadmium and lead levels had been experimentally enhanced. 

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