The Effects of Road Transport on Freshwater and Marine Ecosystems

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mobilised and taken up into grass leaves. Dongarra et al. (2003) examined the distribution <strong>of</strong> Pt and Pd
in pine needles (as a biomonitor <strong>of</strong> metal distribution) in urban Palermo. Platinum and Pd concentrations
were closely correlated and higher in the centre <strong>of</strong> the City compared to outside Palermo. <strong>The</strong> PGE
concentrations included elements present on the needle surface as well as within the needle.
In New Zealand and Australia, the uptake <strong>of</strong> elements such as Pb, Cu, Cd and Zn emitted by motor
vehicles by roadside plants (sweet corn, bracken, trees and pasture grasses) has been reported in a
number <strong>of</strong> early studies such as Ward et al. (1974, 1975 and 1977) and by David & Williams (1975).
Jensen et al. (2002) examined PGEs in feathers <strong>of</strong> sparrowhawks and falcons in Sweden and prey
species. <strong>The</strong> analysis <strong>of</strong> feathers from 1917 to 1999 revealed a clear trend with significantly higher
concentrations in falcon feathers after 1986. Higher Pd concentrations were identified compared to Pt
and Rh. PGEs present in feathers are predominantly external being present in nanometre size particles.
Internationally there have been a considerable number <strong>of</strong> studies that have shown uptake <strong>of</strong> road-derived
contaminants such as Pb by mammals. As with plant studies noted above, many <strong>of</strong> these studies were
undertaken in the 1970s when issues associated with the presence <strong>of</strong> Pb in petrol were becoming
apparent (e.g., Jeffries & French 1972, Welch & Dick 1975, Getz et al. 1977). Ward & Savage (1994)
reported the uptake <strong>of</strong> Pb and Cd by animals grazing near the M25 motorway in London.
<strong>The</strong>re appears to be little information on the uptake <strong>of</strong> contaminants by aquatic plants associated with
wetlands, ponds and waterways below road stormwater discharges. A study by Sriyaraj & Shutes (2001)
reported on the concentrations <strong>of</strong> metals in Typha latifolia and Glyceria maxima growing in a pond
receiving run<strong>of</strong>f from the M25 outer London motorway. As found elsewhere the concentrations <strong>of</strong> metals
decreased from the root to the leaf. <strong>The</strong> study showed uptake <strong>of</strong> metals such as Pb and Zn into roots
and rhizomes but the significance <strong>of</strong> the uptake in relation to plant health wasn’t discussed, and no
control data was, presented by the authors.
In New Zealand, aquatic plants such as water-cress (Lepidium sativum) are collected for food. Uptake <strong>of</strong>
contaminants such as arsenic from water has been demonstrated in the Waikato River (Robinson et al.
2003). Water-cress will grow in drainage channels and streams receiving road run<strong>of</strong>f and urban
stormwater. Uptake <strong>of</strong> trace elements such as Cu, Pb and Zn from water and from sediment (pore water)
may occur. Uptake <strong>of</strong> elements such as Cu and Zn are not likely to be <strong>of</strong> public health concern (as both
elements are nutritionally important). Uptake <strong>of</strong> elements such as Pb and Cd, which have limits set to
restrict intake through consumption is <strong>of</strong> greater concern. Although, Pb concentrations have declined
since the introduction <strong>of</strong> lead free petrol into New Zealand, there is still a substantial reservoir <strong>of</strong> lead
within the road and urban environment. Most <strong>of</strong> the Pb originated from motor vehicles.
Available information indicates that elevated concentrations <strong>of</strong> dissolved or particulate metals in
stormwater or stream water have the potential to result in bioaccumulation in freshwater biota.
Information shows that concentrations <strong>of</strong> Cu, Pb and Zn have been reported in a range <strong>of</strong> species but not
consistently between species and feeding groups. Although accumulation has been identified, there is no
information as to the potential for any adverse effects arising from that uptake. It has been demonstrated
that the response to elements such as Cu and Zn differs to that <strong>of</strong> Pb. Uptake <strong>of</strong> the PGEs has also been
demonstrated to occur in freshwater organisms.
<strong>The</strong>re is little data for bioaccumulation <strong>of</strong> trace elements such as Mo and Sb emitted by motor vehicles.
Significant bioaccumulation is however unlikely. For some elements such as Sb and Pd for which there
appears to be no nutritional requirement, uptake in a variety <strong>of</strong> organisms has been demonstrated. <strong>The</strong>
effects <strong>of</strong> bioaccumulation are however unknown at a cellular and whole organism level.
<strong>The</strong>re is little information that indicates that any freshwater species (e.g., eel, watercress) exposed to
those elements derived from road run<strong>of</strong>f would bioaccumulate those elements to the point that would
result in their unsuitability for human consumption.
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