Water Sampling

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Thoughts behind water collection methods

The sampling program should consider the following:

* choice of sampling method informed by what further analysis type(s) is (are) required
* for the method, take into consideration the detection limits and the precision required
* what the hypothesis is that is being tested, what statistical methods will be used to analyse the data
* sampling location and timing is based on a knowledge of the distribution of the pollutant
* the form of the pollutant in the sampling environment, both physical and chemical
* make sure that protection of the personnel from the pollutant is considered


Sample Collection for Microbiological Analysis


Method

  • All samples sent for microbiological analyses must always be collected in sterile containers (e.g. autoclave).
  • Always leave an air space of at least 2.5 cm between the surface of the liquid and the container lid (removal of surface film).
  • The necessary aseptic conditions must be respected when a sample is collected (e.g. use a rubber gloves and mask, avoid inserting fingers or other objects in the mouth or on the lid of the container and minimize exposure of the container to air at the time of sampling). This is also intended to avoid E.coli contamination to the sampling personnel.
  • Carefully close all containers tightly after sampling.
  • Make a detailed record of all samples as soon as possible after sampling.

Sample preservation

* Refrigerate samples 1- 4°C before analysis.
Optional
* for halogen neutralization - add 0.5 mL of a 10% sodium thiosulfate solution per 1 L of sample.
* for chelation of trace elements - add 0.3 mL of a 15% EDTA solution per 100 mL of sample.

Suggested sample holding times

* 6h - surface water and ground water
* 30h - treated drinking-water sources

Main reference:



Sample Collection for Heavy Metal Analysis


from EPA Victoria

Method

  • Filter samples in the field - this distinguishes the dissolved vs the suspended/adsorbed fractions
  • Acidify samples with HCl or HNO3
  • Carefully close all containers tightly after sampling.
  • Make a detailed record of all samples as soon as possible after sampling.
  • Have a negative control

Preservation

* Filter samples in the field (to remove organic and inorganic contaminants associated with particulate matter, or if you need the data separately - dissolved and on suspended matter)
* Acidify samples (preservation of trace metals, prevention of precipitation, microbial growth, and attachment to sample container walls)
* Refrigerate samples 1- 4°C before analysis.

Holding time

* as soon as possible
* For Arsenic, when stored at 1- 4°C, recommended for no more than 2 weeks (Trang et al.)

Our current field sampling protocol for sampling.

Still Need Researching

Can we use one protocol for all of the heavy metals?
We now have mercury, cadmium/zinc reporters.
Acidification with HCl may be better than the current nitric acid, to provide the chloride for mercury, for example for better bioavailability. These issues need to be better researched and tested.
HCl also may be easier to purchase outside of scientific suppliers - see the HCl list from US Department of Health and Human Services.



Sample Collection for Alkane Analysis


Alkanes float - their densities are lower than water. To obtain a surface water sample that gives a representative "concentration" of alkanes may be difficult.

Still Need Researching



Surface vs Deep Water Sampling

Surface Water Sampling

Deep Water Sampling

References

  • Trang, P. T. K., Berg, M., Viet, P. H., Van Mui, N., & van der Meer, J. R. (2005). Bacterial bioassay for rapid and accurate analysis of arsenic in highly variable groundwater samples. Environmental Science & Technology, 39(19), 7625–7630. doi:10.1021/es050992e
  • Handbook of Water Analysis, Third Edition edited by Leo M.L. Nollet, Leen S. P. De Gelder CRC Press 2013 p.389- ISBN 9781439889640