Dynamics of herbicide transport and partitioning under event flow conditions in the lower Burdekin region, Australia

Assessing the additive risks of PSII herbicide exposure to the Great Barrier Reef

“…Previous studies have shown that the herbicides designed to inhibit electron transport at photosystem-II (PSII) in plants (e.g. atrazine, diuron, simazine) are highly mobile and can be transported in stream networks (Alegria et al, 2000;Clark et al, 1999;Davies et al, 1994;Davis et al, 2008;Green and Young, 2006;Lewis et al, 2009;Davis et al, 2012;Smith et al, 2012). During wet season river runoff events, concentrations of these herbicides exceed national water quality ecosystem protection guidelines and/or known organism effect levels offshore from the river mouths (e.g.…”

Spatial and Temporal Variability in Pesticide Exposure Downstream of a Heavily Irrigated Cropping Area: Application of Different Monitoring Techniques

“…Barratta Creek, located in the dry tropics of north-eastern Australia (Figure 1), and with a 73 large proportion of sugarcane cropping in the catchment, has been identified as a high risk 74 area compared to other GBR catchments as pesticide concentrations [15][16][17][18][19][20] [15][16][17][18][19][20][23][24] . While previous studies have examined the concentrations and 77 loads of pesticide residues at various sites along Barratta Creek, no systematic and 78 continuous monitoring approach to examine spatial and temporal variations within Barratta 79 Creek has been undertaken.…”

“…The three freshwater 100 sites (Upper Barratta Creek, West Barratta Creek, and East Barratta Creek) have been 101 subjected to previous monitoring efforts [16][17][18][19] but not at this level of sophistication. The end 102 of catchment estuarine site (Lower Barratta Creek) was within the Bowling Green Bay 103…”

“…Average 277 concentrations of atrazine and diuron measured using both the grab and Chemcatcher in at least one sample collected across the fresh (Table 4) or estuarine sites (Table 5) using 292 either grab or passive methods. Table 6 additional contaminants (including 17 pesticides and two breakdown products) that were not 325 previously reported in Barratta Creek or within the wider GBR catchment area 13,16,[18][19][20][44][45][46] 326 and as such has highlighted that a wide range of pesticide products are used upstream and 327 are largely sourced to cropping lands (particularly sugarcane). Our results also demonstrate 328 that, while both grab and passive sampling methods offer a few (grab) or many (PSD) 329 additional chemicals not detected by the other method, both methods effectively capture the 330 five priority herbicides which pose the most risk to the GBR.…”

“…This irrigation 421 paddock runoff (and associated pesticide losses) is transported through a network of drains 422 which ultimately discharge into Barratta Creek introducing flow into a normally ephemeral 423 system and explains why pesticide concentrations in Barratta Creek increase prior to the 424 onset of wet season rains [17][18][19] . Several studies have shown that the dominant mechanism 425 driving the amount of pesticide lost from croplands relates to surface runoff following 426 rainfall as well as the timing of pesticide application [52][53] .…”