If samples are not properly chilled and sealed, which water quality indicators may be significantly affected?

When water samples are not properly chilled and sealed, several chemical and biological processes can alter the composition of the samples, leading to changes in various water quality indicators. BOD (Biochemical Oxygen Demand) and COD (Chemical Oxygen Demand) are particularly sensitive to temperature and time, as these parameters measure the amount of organic matter present and the oxygen required to decompose it. If the samples are not kept cold, microbial processes can continue to alter the levels of organic matter, resulting in inaccurate BOD and COD readings.

Dissolved sulfide is also affected due to its association with microbial activity, which can lead to production and consumption shifts that can change its concentration in improperly stored samples. Therefore, without the necessary chilling and sealing, these indicators—BOD, COD, and dissolved sulfide—can exhibit significant variability that does not accurately represent the actual conditions of the water source, thus highlighting the importance of proper sample handling in water quality assessments.