Residents of Springfield, U.S.A. rely on the Shelbyville aquifer for drinking an

Question

Residents of Springfield, U.S.A. rely on the Shelbyville aquifer for drinking and irrigation water. Recently, residents have been concerned that the water has a foul odor (similar to that of rotten eggs) and that the crops are beginning to wilt. You are the experienced EHS who has been contacted by the Springfield, U.S.A. City Council to investigate these concerns. You immediately suspect that the groundwater has been contaminated but you must first compose an action plan (including justification) that identifies the following:

A. the tentative identification of the most likely pollutant causing the unpleasant odor and the crops to wilt,

B. the specific laboratory analysis you will conduct to qualify and quantify the tentatively identified pollutant causing the unpleasant odor and crops to wilt,

C. the potential source(s) of the pollutants causing the unpleasant odor and the crops to wilt, and

D. One remedial effort to reduce the introduction of the pollutant into the Shelbyville aquifer.

Explanation / Answer

A. the tentative identification of the most likely pollutant causing the unpleasant odor and the crops to wilt:

The offensive rotten egg odor is a pretty good indicator for the Hydrogen Sulphide Gas (H2S), which can be present in the groundwater. Excess sulphur in the soil can lead to lowering pH of the soil producing excessive salts and result in acidification, which in turns damages the vegetation.

B. the specific laboratory analysis you will conduct to qualify and quantify the tentatively identified pollutant causing the unpleasant odor and crops to wilt:

Hydrogen Sulphide Gas (H2S) is readily dissolved in, as well as escape water. So the samples collected should be readily stabilised for laboratory analysis.

If the source of contamination is sewage pollution, the "H2 S Strip Test" can confirm the presence of the contaminant while pointing to the occurrence of coliform bacteria.

However, the laboratory standard procedure to qualify and quantify the contaminant would be an Iodimetric Titration (0.1N I2 standard solution) followed by calculation of the Normality or Molarity of the H2S or % composition by using formulas

N1V1 = N2V2

M1V1 = M2V2

H2S % = [Titer(ml) X 0.1 N of I2 X eq wt of H2S X 100] / [wt of the sample grams taken X 1000]

C. the potential source(s) of the pollutants causing the unpleasant odor and the crops to wilt:

D. One remedial effort to reduce the introduction of the pollutant into the Shelbyville aquifer:

Remedial methods are usually tailor-made in accordance to the level of contamination, therefore:

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