Environmental Engineering Reference
In-Depth Information
The great majority of this plastic litter is derived either from post-use
consumer plastics on land or from plastic fishing gear. With the world's
fishing fleet almost exclusively relying on plastic gear, the latter is a
significant contributor to marine plastics debris, and ghost fishing by
derelict gear is a growing worrisome concern (Matsuoka et al., 2005). Crab
pots are a particularly visible variety of derelict gear (Anderson and Alford,
2014). A survey of an area of 2 sq. mi in the Bering Sea (Stevens et al.,
areas of the Bering Sea, that would amount to 1.7 million derelict crabpots.
In Chesapeake Bay area, 32,000 lost traps (over four seasons) were recently
recovered and an estimated 900,000 marine animals were affected by their
presence in the coastal ocean bottom (Bilkovic et al., 2012, 2014; Galgani et
al., 2010).
Packaging plastics used in beach environments litter the coastal areas
worldwide. Beach cleanups generally find the same set of common plastics
used in packaging to be the major components of litter (Gregory, 1999;
McDermid and McMullen, 2004; Ng and Obbard, 2006; Topçu et al., 2013).
The size ranges of debris reported in such surveys are incomplete as they
exclusively focus on beaches and on visible items overlooking those items
smaller than a few millimeters in size. Enumerating plastics floating on
surface water is even more difficult. Some of these plastics (polyethylene
(PE), polypropylene (PP), and expanded polystyrene foam (EPS)) float in
seawater, and others (such as poly(vinyl chloride) (PVC), poly(ethylene
terephthalate) (PET), or poly(styrene (PS)) being relatively denser resins,
sink and reach mid-water column or the benthic sediment. But as already
resin prils; fillers and additives added to plastic materials used to make
products, can change its density. Each year a small fraction of the 280
MMT of plastic resins produced in the world invariably enter the oceans
as accidental spills, gear losses, or as postconsumer waste (Thompson et
al., 2005). This fraction is not reliably known, though recent estimates (EC,
2013) suggest 10-20 MMT [4.8-12.7 MMT is a recent second estimate]
of influx annually. Plastics as already discussed in
Chapter 6
biodegrade
extremely slowly, especially when they are in seawater or sediment. This
suggests that all plastics that entered the oceans since the beginning of the
plastics age (in 1950s) still very likely remain unmineralized, accumulated
intact in the marine sediment. Plastic debris has been observed in the
marine benthos (Barnes et al., 2010). The ecological impacts of plastics
