grab samples

other organohalogens and another for petroleum oils and greases. Bottles may be reused only if they are
carefully cleaned and rinsed with suitable solvent (see below). With aluminum cans the same high degree
of cleanliness is required.
Size: SOO-m I ( 16-oz) I-pin t Mason jars or eq uivalen t. Caps should be fla t so that alumin urn foi I liner is
not torn when the lid is screwed on.
Preparation: Wash bottles with laboratory detergent; fill and rinse at least three times with deionizeddistilled
water; rinse twice with acetone; rinse twice with hexane. The interiors of bottles must not be
touched by fingers after preparation.
Aluminum foil: Rinse with hexane dispensed from squirt bottle. Do not touch with fingers the cleaned
surface that may be in contact with the sample; clean foil after sample has been placed in bottle just prior to
closing bottle.
2.3 Dispensing Samples into Containers
2.3.1 Grab Samples
When grab samples are used either as the source of surface sediment samples or because samples
cannot be obtained with a corer, allow the excess water to drain out of the grab before subsampling. Some
grabs allow access to the sample through the top of the sampler, while others require the release of the
sample on deck before subsampling can take place.
Grabs are normally made of metal, so care must be taken to obtain a subsample for trace metal
analysis which has not been in contact with the grab surface. It is recommended that grabs that can be
sampled from the top (e.g., Ekman grab) should be used to avoid undue disturbance or contamination. An
epoxy paint coating on the grab will help but not completely solve the problem. Since the mechanism and
supporting ca ble of the grab may have been greased for main tenance pu rposes (use as lit tie as possible), the
possibility of petroleum contamination exists as well.
Tfthe grab sample is relatively undisturbed and the former sediment-water interface is clearly defined,
dispense representative subsamples which include the interface into the sample bottles, avoiding sediment
which may have come in direct contact with grab.
If the grab sample appears to be disturbed, follow the sampling scheme illustrated in Figure 4. Scrape
aside the top layer of the sample and take a subsample for all chemical analyses except pesticides, other
organohalogens, petroleum oils and greases using a precleaned porcelain or glass scoop. Place in
precleaned SOO-ml ( 16-oz) plastic bottle. Cap. Do not acidify or otherwise attempt to preserve the sample.
Scrape away more of the surface layer from the sides, and place the subsample for pesticides and other
organohalogens in one precleaned SOO ml (16 oz) glass bottle and place the subsample for petroleum oils
and greases in the other. Avoid touching samples with fingers and make subsamples as representative as
possible by placing alternate scoops in the two bottles. Cap with foil lined cap (see Section 2.2.3). Lightly
stir the remaining sample, and fill a 2S0-ml (8-oz) precleaned plastic bottle for physical analysis. Label all
sample bottles (see Section 2.4).
2.3.2 Core Samples
See Section 2.1.2 for instructions on collecting and handling core samples in the field.
Deeply score the opposite sides of the core liner containing core lengthwise with a router or skill saw
and complete the cut with a hexane-cleaned utility knife or scalpel. Avoid contact between the sediment
and the oil-lubricated metal saw to prevent contamination. Split the sediment core by drawing a hexanecleaned
wire (piano wire is satisfactory) lengthwise through the core. Lay back the two halves of the core.
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