Environmental Engineering Reference
In-Depth Information
5.2.1.2 Ocean/Waterway-based Sources
Plastic wastes are also generated from the anthropogenic activities at sea such as
commercial ishing vessels, recreational boats and cruise ships, cargo vessels and
passenger ships, research vessels, and so on (
Table 5.1
). Bait containers/packaging,
bleach/cleaner bottles, buoys/loats, crab/lobster/ish traps, crates, ishing line, ishing
lures/light sticks, ishing nets, light bulbs/tubes, oil/lubricant bottles, pallets, plastic
sheeting/tarps, rope, strapping bands for packaging/cargo, are all ocean-based sources
of plastics in the seas [8, 10].
5.2.2 Qualitative and Quantitative Estimates of Plastics in the Marine
Environment - Global Scenario
Increase in use of plastics and synthetics over the past 30−40 years, has changed the
nature of solid wastes ending up in the coastal and marine environment. A number
of studies have been carried out in different countries to estimate the quantity
of plastic on beaches, the sea loor, in the water column, and on the sea surface.
The results show that plastic debris is ubiquitous in the world's oceans and shorelines.
Higher quantities are found in the tropics and in the mid-latitudes compared to areas
towards the poles. Thompson and co-workers [11] while investigating the quantity
of microscopic plastic in plankton samples on routes between Scotland - Shetland
Islands and Scotland to Iceland during the 1960s found that there was a signiicant
increase in the abundance of microscopic plastic over the past 40 years. One of the
studies in the sub-Antarctic islands showed that these islands are increasingly being
affected by plastic debris - especially ishing lines [12]. Large quantities are often
found in shipping lanes, around ishing areas and in oceanic convergence zones.
Plastic debris is the predominant form of litter in almost all the studies of shore debris
around the world (
Figure 5.1
). A study of beaches in Orange County, California
reported an exceptionally high proportion of plastic (99%) in the shore debris.
Plastic pellets were the most abundant form of litter and hard plastics and foamed
plastics were also present [13]. Small quantities of plastic debris were reported to be
present in the Southern Ocean south of New Zealand, near the Antarctic Peninsula
and north and north-west of the Ross Sea [14, 15]. In a study of the sealoor using
trawl nets in the North-Western Mediterranean around the coasts of Spain, France
and Italy in 1993−1994, 77% of the debris recorded was plastics, of which 92.8%
were plastic bags [16].
