Chapter 2 Rainwater Analysis (Phân tích nước mưa) - Practical Environmental Analysis, 2nd Edition - M. Radojevic, V. Bashkin

Rainwater Analysis 53
organic acids (formic and acetic) and trace metals are also being determined.
Common techniques of acid rain analysis are summarised in Table 2.2.
Concentration ranges of the various ions in rainwater are given in Table 2.3.
Although rainwater analysis may appear to be fairly straightforward, it is
in fact quite problematic. Sources of error common with other types of environmental
samples are present and these are greatly exacerbated because of
the low concentrations of ions present in rainwater. Many rainwater samples,
especially at remote locations are almost as pure as laboratory-grade waters.
Therefore, great care must be taken when handling, storing, and analysing
rainwater samples in order to maintain sample integrity.
Sources of error in acid rain analysis include:
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contamination by biological materials (e.g. insects) during sampling;
evaporation from samples;
absorption/desorption of gases during sampling or in the laboratory;
chemical or biological reactions during sampling or storage;
interaction with bottle materials; and
inadvertent contamination during sample handling, treatment, or analysis.
Table 2.2 Common techniques of rainwater analysis
Analytical technique
Analyte
Conductivity meter
Conductivity
Ion chromatograph (IC) Cl 2
,NO 3 ,SO 4 ,NH 4 ,Na ,K ,Mg 2 ,Ca 2 ,
formate, acetate
Flame atomic absorption
Na ,K ,Mg 2 ,Ca 2
spectroscopy (FAAS)
Flame atomic emission
Na ,K ,Mg 2 ,Ca 2
spectroscopy (FAES)
Inductively coupled plasma (ICP) Na ,Mg 2 ,Ca 2 , trace metals
Graphite furnace atomic absorption Trace metals
spectroscopy (GFAAS)
Ion selective electrodes (ISE) H ,Cl ,NO 3 ,Na ,K ,NH 4 ,
some trace metals
Voltammetry
Trace metals
Table 2.3 Concentrations of major ions in rainwater
Ion Concentration (mg L 1 )
Chloride 0.02–60
Nitrate 0.1–20
Sulfate 0.1–30
Sodium 0.02–30
Potassium 0.02–2
Magnesium 0.005–2
Calcium 0.02–4
Ammonium 0.03–4