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The Effects of Road Transport on Freshwater and Marine Ecosystems

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75<br />

Benzathiazoles in stormwater <strong>and</strong> receiving envir<strong>on</strong>ments<br />

Although benzathiazole was not identified as a COPC by Kennedy & Gadd (2000), it is worth<br />

examining what we know about this group <str<strong>on</strong>g>of</str<strong>on</strong>g> soluble organic compounds <strong>and</strong> their toxicity. Reddy &<br />

Quinn (1997) identified Benzothiazole (BT), 2-hydroxybenzothiazole (HOBT) <strong>and</strong> 2-(4-<br />

morpholino)benzothiazole (24MoBT) in tyres (also identified in New Zeal<strong>and</strong> tyres by Gadd & Kennedy<br />

2000). Reddy & Quinn (1997) identified that following five leaches <str<strong>on</strong>g>of</str<strong>on</strong>g> tyre crumb particles with<br />

dei<strong>on</strong>ised water that 50% <str<strong>on</strong>g>of</str<strong>on</strong>g> the Benzothiazole (BT) compounds was removed. Dissolved BT <strong>and</strong><br />

other benzothiazolamines have been detected in urban run<str<strong>on</strong>g>of</str<strong>on</strong>g>f by Reddy & Quinn (1997) <strong>and</strong> Kumata<br />

et al. (2002) (Table 6.6).<br />

Table 6.6 - Summary <str<strong>on</strong>g>of</str<strong>on</strong>g> mean dissolved c<strong>on</strong>centrati<strong>on</strong>s <str<strong>on</strong>g>of</str<strong>on</strong>g> Benzathiazoles in urban<br />

run<str<strong>on</strong>g>of</str<strong>on</strong>g>f (c<strong>on</strong>centrati<strong>on</strong>s ug/m 3 ).<br />

BT 378 –819 (Pawtuxet River, Reddy & Quinn 1997)<br />

HOBT 721 – 5,640 (Pawtuxet River, Reddy & Quinn 1997)<br />

24MoBt<br />

15-383 (Reddy & Quinn 1997 <strong>and</strong> Kumata et al. (2002) Chuo highway Japan)<br />

<str<strong>on</strong>g>The</str<strong>on</strong>g> benzathiozoles are str<strong>on</strong>gly water soluble <strong>and</strong> as such they tend to be transported or washed out<br />

<str<strong>on</strong>g>of</str<strong>on</strong>g> the atmosphere in dissolved form. BT is capable <str<strong>on</strong>g>of</str<strong>on</strong>g> being volatilised <strong>and</strong> both BT <strong>and</strong> HOBT can be<br />

microbially degraded. With limited biological uptake <str<strong>on</strong>g>of</str<strong>on</strong>g> this group, the combined envir<strong>on</strong>mental<br />

processes should see a shift in the c<strong>on</strong>centrati<strong>on</strong>s <str<strong>on</strong>g>of</str<strong>on</strong>g> all three compounds over time. BT <strong>and</strong> HOBT<br />

should decrease <strong>and</strong> 24MoBT increase over time. In estuarine envir<strong>on</strong>ments <strong>and</strong> coastal<br />

envir<strong>on</strong>ments there should be a net export <str<strong>on</strong>g>of</str<strong>on</strong>g> these compounds out <str<strong>on</strong>g>of</str<strong>on</strong>g> the system in tidal waters. <str<strong>on</strong>g>The</str<strong>on</strong>g><br />

microbial fate <strong>and</strong> photolysis <str<strong>on</strong>g>of</str<strong>on</strong>g> benzathiozoles have recently been evaluated by Kirouani-Harani<br />

(2003).<br />

Evans et al. (2000) examined the effects <str<strong>on</strong>g>of</str<strong>on</strong>g> benzathiazole <str<strong>on</strong>g>of</str<strong>on</strong>g> sheepshead minnows (Cyprinod<strong>on</strong><br />

variagatus). <str<strong>on</strong>g>The</str<strong>on</strong>g>y reported that benzothiazole was lethal <strong>and</strong> growth inhibitory to sheepshead minnow<br />

larvae. Lethality occurred after 5 days exposure at 60 g/m 3 <strong>and</strong> significant decrease in growth at<br />

c<strong>on</strong>centrati<strong>on</strong>s down to the lowest test c<strong>on</strong>centrati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> 3.75 g/m 3 . Upper c<strong>on</strong>centrati<strong>on</strong> in Table 6.6.<br />

<str<strong>on</strong>g>of</str<strong>on</strong>g> 5.6 mg/m 3 are 1,000 times lower than the lower c<strong>on</strong>centrati<strong>on</strong> used by Evans et al. (2000) in their<br />

toxicity assessment. <str<strong>on</strong>g>The</str<strong>on</strong>g> data indicates that benzothiazoles are not an acute toxicity risk in receiving<br />

envir<strong>on</strong>ments.<br />

Based up<strong>on</strong> this simple requirement, copper, lead <strong>and</strong> zinc c<strong>on</strong>centrati<strong>on</strong>s would <strong>on</strong>ly require a small<br />

amount <str<strong>on</strong>g>of</str<strong>on</strong>g> diluti<strong>on</strong> to ensure that the potentially chr<strong>on</strong>ic effects that could arise from the discharge are<br />

avoided. Sec<strong>on</strong>dly, there are however, a number <str<strong>on</strong>g>of</str<strong>on</strong>g> factors that need to be c<strong>on</strong>sidered when<br />

assessing the potential for toxicity. <str<strong>on</strong>g>The</str<strong>on</strong>g>se are:<br />

a. In many urban streams, stormwater flow may comprise most <str<strong>on</strong>g>of</str<strong>on</strong>g> the stream flow.<br />

b. Stormwater metals data is typically reported as total metal. <str<strong>on</strong>g>The</str<strong>on</strong>g> USEPA guidelines should now be<br />

interpreted as dissolved metal c<strong>on</strong>centrati<strong>on</strong>s <strong>and</strong> ANZECC (2000) guidelines for metals are most<br />

appropriately compared to dissolved metal c<strong>on</strong>centrati<strong>on</strong>s.<br />

c. <str<strong>on</strong>g>The</str<strong>on</strong>g> comparis<strong>on</strong> does not take into account the form or the species <str<strong>on</strong>g>of</str<strong>on</strong>g> metal <strong>and</strong> therefore the<br />

potential toxicity.<br />

e. <str<strong>on</strong>g>The</str<strong>on</strong>g>re are issues associated with the appropriateness <str<strong>on</strong>g>of</str<strong>on</strong>g> toxicity tests (see below).<br />

<str<strong>on</strong>g>The</str<strong>on</strong>g>se issues have recently been reviewed by Timperley (1999). Timperley c<strong>on</strong>cluded that dissolved<br />

c<strong>on</strong>centrati<strong>on</strong>s were potentially a poor indicator <str<strong>on</strong>g>of</str<strong>on</strong>g> aquatic toxicity. This occurs as not all dissolved<br />

c<strong>on</strong>stituents are bio-available. <str<strong>on</strong>g>The</str<strong>on</strong>g> proporti<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> metal in bioavailable form (to exert toxic effect) is<br />

dependent up<strong>on</strong> the pH as the toxicity <str<strong>on</strong>g>of</str<strong>on</strong>g> the free i<strong>on</strong> is still dependent up<strong>on</strong> complexing by major i<strong>on</strong>s<br />

Kingett Mitchell Ltd<br />

Resource & Envir<strong>on</strong>mental C<strong>on</strong>sultants

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