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Introduction to environmental analysis - Reeve R.

Reeve R. Introduction to environmental analysis - Wiley publishing , 2002. - 312 p.
ISBN 0-471-49295-7
Download (direct link): introductiontoenvironmental2002.pdf
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Had I restricted my question simply to metals, you might also have included the problem of different metal species in the sample. Unless you had converted the metal species completely to a single form, you would risk the loss of metal at each stage of the analysis according to the chemical behaviour of the particular species.
Response 4.6
The pretreatment in (i) ensures that all of the metal species in the sample will have been decomposed and so the total metal concentration will be determined.
Procedure (ii) will measure the free metal ions and loosely bound complexes. This measurement is known as the ASV-labile metal content.
Procedure (iii) will destroy easily oxidizable organic material. Subtraction of the results, (iii) — (ii), will measure the amount of metal found in the complexes. The latter is known as the organically bound labile metal content.
Free metal ions will be held by the resin in procedure (iv), as will the metal from loosely bound complexes. Thus procedure (iv) will then determine the amount of metal bound in highly stable complexes.
Procedure (v) will extract organic soluble complexes, and hence subtraction of the results, (i) — (v), will measure the organic-soluble content.
262
Introduction to Environmental Analysis
Chapter 5
Response 5.1
The deposition would be expected to be greatest at the side of the road and would decrease with distance. A site should be selected where samples could be taken close to the road, ideally where there is no intervening pavement. The site should be distant from any other potential sources of lead. Both sides of the road should be sampled to compensate for the effects of wind. Sampling (taking duplicate samples) should be more frequent close to the road, perhaps with sampling distances from the road in the ratio 1:2:4:8:, etc. Since the source of the lead is from the atmosphere, surface samples should be taken. Samples taken below the soil surface could give an indication of penetration into the soil. Control samples as similar as possible to the monitoring samples should be taken some distance from the roadway.
Response 5.2
The use of a number of solvents will increase the number of extracted components. This would then require either more comprehensive clean-up procedures prior to chromatographic analysis, and/or a higher degree of resolution in the chromatographic separation. You may also have to consider problems associated with additional solvent peaks in the chromatographic analysis and the trace impurities introduced with each solvent.
Response 5.3
Potassium and calcium can be analysed by flame photometry (see Section 3.4.2) and magnesium and the trace metals by atomic absorption spectrometry or other atomic spectrometric techniques (see Section 4.3.3). Orthophosphate is best determined by visible spectrometry after conversion to a blue-coloured phosphomolybdenum complex (see Section 3.4.1).
Response 5.4
The order of sensitivity is as follows:
1. — (b) Atmospheric exposure of residents for long periods, with the possibilities
of uptake of contaminants from crops and ingestion of metals in soil by children.
2. - (a) The public would spend a more restricted amount of time here, though
there would be still be the possibility of direct exposure to contaminants in soil and atmosphere
3. - (d) More limited exposure to the public; much of the site may be surface-
covered in subsequent development.
Responses to Self-Assessment Questions
263
4. - (c) The hard surface of the car park would form a barrier to soil contaminants. The time spent by any one individual in such an area will be limited.
Volatile components are a problem in all areas, with methane a particular problem when it can build up within buildings ((a) and (c)). Toxic metals are a problem where there may be direct intake by, for instance, playing children or where crops are grown for possible human consumption ((a) and (b)). If you are considering heavily polluted industrial sites, you should also consider any aggressive properties from dumped waste (e.g. caustic properties and excessive amounts of leachable ion such as chloride) which may have an adverse affect on buildings as well as the public.
Response 5.5
You could be dealing with samples with concentrations of the analyte from percentage concentrations down to ^g l-1 and these could be taken from highly contaminated locations. There are problems of contamination at the sampling site, during storage and transportation (including cross-contamination of samples if inappropriate bottles or bottle tops are used) and within the equipment (carryover of the analyte between samples).
The overall composition of waste samples can vary widely and quite often the total composition is unknown. Matrix effects may vary widely and unpredictably from sample to sample. Great care is necessary to confirm that these analytical problems have been overcome.
Response 5.6
Water will be the easiest to sample (unless you have access to local fisheries) and will need less pretreatment to remove potential interferences. The concentrations determined will be lower than in the other samples, and often are little above the lower limits of routine detection. (You may recall the typical concentrations given for DDT in Figure 2.5 and the metal enrichment factors shown in Table 2.1.)
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