General Sample Collection Techniques Clause Samples

General Sample Collection Techniques. 6.1.1 Samples will be collected at quarter point transects unless the width of the river or stream makes doing so impractical or useless. A quarter point transect consists of collecting water at 3 points on a line perpendicular to the stream. The points are generally near the right and left bank and near the center of the river or stream. 6.1.2 Always collect the sample facing upstream to avoid collecting what is re-suspended by ▇▇▇▇▇▇. In slow moving waters movement upstream after each transect may be necessary to avoid the plume of re-suspended material. 6.1.3 Always were Nitrile gloves when sampling. The use of the Nitrile gloves protects the sample from contamination from the hands of the sampler. 6.1.4 Take care not to bias the sample at any one depth of water. Pesticides may be distributed throughout the water column and by taking a sample at one depth the sampler may miss what is present elsewhere. Particular care should be taken to avoid collecting a disproportionate quantity of water or suspended sediment at the surface of the river or stream. Some pesticides may partition to the surface layer or sorb to bedload constituents. Collecting water in a single region may bias the concentration in the sample. 6.1.5 When possible keep the lid on the sample containers between transect points. This will avoid contamination from atmosphere and rain. This is not always possible and should be assessed on a case by case basis. 6.1.6 When possible keep the sample containers out of the sun during sample collection. In addition, use amber bottles for those pesticides susceptible to photolysis. 6.1.7 Fill sample containers to the shoulder. If testing for highly volatile products, sample containers should be filled to the top of container (no headspace). In this instance, volatile products are compounds with a Henry’s Law constant greater than or equal to 10-3 atm*m3/mole. 6.1.8 Take care not to disturb the substrate with the transfer bottle or collect anything from the substrate.