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chromium complex (Skelly and Dieball, 1970). The nature of this

new phase is not well understood.

Ion

Jessen and Johnson (1963) discuss physical adsorption and ion exchange relations between chrome lignosulfonate and clay components of drilling muds. Their work indicates a strong tendency towards adsorption of all chrome species present in the muds tested. exchange occurred predominately in the high-sodium bentonite clay types. Both transfer mechanisms effect the removal of chrome components from the water column with subsequent deposition as clay sediment. Once on the sea floor, chrome lignosulfonate is fairly resistant to biodegradation, however, certain benthic invertebrates are known to concentrate trace amounts of various heavy metals over extended time. The possible role of drilling mud chromium additives in this phenomenon should not be ignored. Recent industry tendencies towards maximum recovery of chemical additives will minimize any potential hazard to life species while relevant experimental data

accumulates.

In general the effects of pipeline burial and drilling mud and cutting discharges are:

a) dredging near shore areas where land pollution has occurred for many years, numerous pollutants will be resuspended in the water column. These may include organic matter which

b)

will increase BOD and decrease dissolved oxygen, toxic

heavy metals and pesticides which may exert toxic effects

before gradually being reincorporated into the sediments.

dredging in areas of hard bottoms, where biotic communities
have evolved to take advantage of such conditions and are
adapted for attachment to a hard substrate (sponges, soft
and hard corals, seaweeds, sessile molluscs), will eliminate
suitable sites for attachment in the path of the operation.
These effects will be neither permanent or last until the
substrate can become compacted again, a process involving
at least several years.

c) both pipeline burial and mud/cutting discharges will pro-
duce a smothering effect on the burrowing and attached
benthos where the material gradually settles as a layer
of significant thickness.

d)

e)

increased turbidity will occur at all marine sites where
pipeline burial and mud/cutting discharges takes place.
The fine particles causing the turbidity can clog the
respiratory organs and filter-feeding mechanisms of
many marine animals.

pipeline burial in coastal wetlands and uplands will dis-
place many species of wildlife during operations due to
noise pollution and the physical presence of construction

machinery. This disruption will terminate as soon as

construction is completed. The effects of pipeline burial

in wetlands can have a substantial impact of one to several years duration through devegetation and disruption of

substrate.

OTHER IMPACTS

Still significant, but probably less environmentally damaging impacts result from the discharge of produced formation waters into the sea and onshore habitat removal by pipeline terminals and ancillary

facilities.

[blocks in formation]

Impacts that may be anticipated to have an effect on

plankton will result from accidental spills of oil, discharge of drilling fluids, and formation waters, and burial of pipelines.

After an oil spill has occurred from a platform, that which has not evaporated, been carried ashore, or cleaned up will float at the surface for a time and eventually be dispersed as minute droplets in the water. In addition, certain components of crude oil are slightly soluble in seawater. In the two latter phases the oil has the opportunity to damage marine plankton and enter the marine food chain.

Hufford (1971) notes laboratory studies which indicate that oil can affect phytoplankton at the cellular level after several days exposure. He cites laboratory experiments in which oil products in seawater inhibit cellular division and cause death in phytoplankton. Apparently, cellular membranes were damaged by the penetration of hydrocarbons and this led to the extrusion of the cellular contents. The MIT Offshore

Oil Task Group (1973) had concluded after an extensive literature survey that phytoplankton sensitivities vary over a wide range, that a few species are apparently sensitive to concentrations of soluble aromatic derivatives of crude oil as low as 1 ppm. However, most species are unharmed by concentrations of 100 ppm or higher. In relation to oil in formation water discharges, the MIT Group noted

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