An assessment of sediment toxicants in Western Port and major tributaries
Sharp, Myers, Pettigrove July 2013 CAPIM Technical Report No 27
p34 Site UN28: Western Contour Drain Estuary Mouth Blind Bight
p 13 Pesticides
A number of studies have detected pesticides in several of the rivers and creeks that flow into Western Port. For instance, Melbourne Water sediment quality data from 2008 – 2009 indicated that pesticides were entering the bay via Watsons Creek, which flows into Yaringa Marine Park in the Lower North Arm, flagging this section of the bay as a crucial area for follow up monitoring. This study also detected pesticides in Cardinia Creek sediments including low concentrations of simazine and metabolites of DDT. Earlier reports detected various organochlorine pesticides (including metabolites of DDT, lindane, endosulfan and chlorpyrifos) in freshwaters including Watsons Creek, Warringine Creek and Lang Lang River among other waterways entering the bay (Hardwick, 1998, Coleman and Pettigrove, 2001). In 1997, the concentration of pesticides measured at 10 sites were all below the limits of detection including atrazine (50 μg/kg), organochlorines (<5 μg/kg) and organophosphates (<50 μg/kg) (Rees et al., 1998), with concentrations also below detection limits at four sites measured for 2,4-D (<50μg/kg). It should be noted that the limits of detection used by Rees et al (1998) weresignificantly higher than those used in the studies undertaken by Hardwick (1998) and Colemanand Pettigrove (2001) which may explain why there were no pesticides detected. Beyondpreliminary data of waterways, the full extent of pesticide contamination in Western Port has yet to be determined.
Of the 22 sites sampled for pesticides in sediments, eight sites had detections (Table 7; Figure15). A total of 17 pesticides were detected, with up to nine different pesticides occurring at Western Contour Drain (UN26) which included four herbicides (simazine, metolachlor, prometryn and linuron), four fungicides (oxadixyl, azoxystrobin, boscalid and cyprodinil) and the insecticide fenamiphos (Table 7). The highest concentrations detected for the triazine herbicide prometryn and fungicide boscalid (15 and 22 μg/kg respectively) occurred in the Western Contour Drain (UN26). Watsons Creek estuary had the second highest number of detections (8) being a source of four insecticides (two organochlorines (pp-DDE and pp-DDT; pirimicarb and fenamiphos), three triazine herbicides (metolachlor, prometryn, and linuron) and the fungicide boscalid at 8 μg/kg. At Yallock Cut and Deep Creek a total of four and five different pesticides were detected respectively. At Deep Creek the organochlorine derivatives, pp-DDE and pp-DDTwere above the ISQG-low suggesting a potential moderate impact to aquatic faunal assemblages. The other pesticides detected at both of these sites were below 2 μg/Kg, however no guidelines exist for any of the other pesticides detected. At Sawtells Creek three pesticides were detected. The organochlorine derivative pp-DDE was detected at a concentration of 0.73 μg/kg which was below the ISQG-low suggesting it is unlikely to be having a detrimental effect on aquatic fauna at this site. The synthetic pyrethroid insecticide bifenthrin was detected at 5 μg/Kg and the herbicide diuron at 28 μg/kg. There are no ISQG values for these pesticides. The
other three sites (Western Contour estuary, Lang Lang River and Bass River estuary) had only
one pesticide detected, concentrations ranging between trace and 1 μg/kg, with the exception of boscalid in Western Contour estuary at 6 μg/kg (Table 7). No pesticides were detected at any of the six sites in Western Port or in sediments from Warringine Creek (LN9), Cardinia Creek (UN17, UN32), Bunyip River (UN29), Deep Creek (UN30, UN31), Merricks Creek (WS2) and Sawtells Inlet (UN8).
The most commonly detected pesticides were the organochlorine derivatives pp-DDE and pp-DDT (four and three sites respectively), followed by the triazine herbicide simazine and thefungicides azoxystrobin and boscalid (three sites each). The herbicide diruon was only detected at one site, however was the highest concentration detected across all detections, 28 μg/kg, thiswas followed by the fungicide boscalid at 22 μg/Kg and triazine herbicide prometryn at 15 μg/kg (Table 7). It should be noted that there are currently no ISQG guidelines for any of the pesticides other than the organochlorines detected in this study.