Stormwater metal loading to a well-mixed/stratified estuary (Sydney Estuary, Australia) and management implications

Abstract

Stormwater modelling indicated an average annual discharge from Sydney estuary catchment of 215,300 mL and loadings of 0.8, 0.5, 1.7, 3.2, 1.1, 3.6 and 17.7 tonnes for As, Cd, Cr, Cu, Ni, Pb and Zn, respectively. Priority for remediation should be given to creeks with high-metal loads in the upper and central estuary, as well as discharging to the western shores of Middle Harbour. Managerial strategies need to target dissolved and particulate metal phases to ensure effective remediation. The proportion of metals discharged under low- (<5 mm rainfall/day), medium- (>5 to <50 mm/day) and high-flow conditions (>50 mm/day) was approximately 10%, 60% and 30% of total loading, respectively. Under high-flow conditions the estuary becomes stratified and most metals are exported to the sea, whereas metals discharged during low-flow may be remediated by infiltration. Effective remediation will depend on the extent to which 'first-flush' metals associated with medium-flow conditions can be remediated.

Emerging contaminants (pharmaceuticals, personal care products, a food additive and pesticides) in waters of Sydney estuary, Australia

“…The waterway is geometrically complex and bathymetry is irregular (1-46 m deep, mean water depth of 13 m). During dry weather conditions fresh water discharge is low (<0.1 m 3 /s) (Birch and Rochford, 2010) and salinity is homogeneous throughout the estuary (Hatje et al, 2001). Both low fresh-water discharge and tidal turbulence contribute to well-mixed estuarine conditions with salinity ranging from 27 at the headwaters to 35 at the mouth in the absence of precipitation (Lee et al, 2011.…”

Potential effects of storm-water run-off on assemblages of mobile invertebrates

“…Individual organisms may be able to cope with the disturbance through complex physiological adaptations, which may have long-term ecological costs in terms of survival or reproduction (Underwood 1989). This would be likely in Sydney Harbour and in other densely populated estuaries or coastal areas that have high and widespread levels of contamination (Birch & Rochford 2010). In these areas, the choice of appropriate control locations may be difficult and the presence of contaminants and other anthropogenic disturbances may result in constant stress on organisms.…”

“…Decreased water quality appears to be one of the main factors contributing to the degradation and loss of important biotic near-shore habitats, such as kelp beds and coral reefs (Benedetti-Cecchi et al 2001, Bellwood et al 2004. Over the past few decades, coastal run-off has steeply increased, becoming a primary cause of degradation of water quality (Gorgula & Connell 2004, Birch & Rochford 2010. In urbanised areas, storm-water run-off may contain a variety of contaminants, such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), metals, pesticides, bacteria, sewage from sewer overflows, oil and grease (Aryal et al 2010).…”

Contaminated soil and sediments in a highly developed catchment-estuary system (Sydney estuary, Australia): an innovative stormwater remediation strategy

“…Although poor, past industrial practice has resulted in large accumulations of legacy chemicals in estuarine sediments Taylor 1999, 2000;NSW EPA 2001), the greatest contemporary source of metals to Sydney estuary is stormwater (Birch and Taylor 1999;Barry et al 2000). Surficial sediment metal concentrations increase substantially towards the mouths of large stormwater canals entering the harbour and stormwater contains high concentrations of particulate and dissolved phase metals (Barry et al 2000;Birch and Rochford 2010). Highly contaminated estuarine sediments adjacent to mouths of stormwater canals and elevated concentrations of metals in bed-load materials supports a significant and contemporary catchment-derived supply of metals to the estuary .…”

“…Knowledge of these deposits has prompted investigations of the adjacent catchment to identify contaminant sources and quantify loading (Birch and Rochford 2010). The current work concerns detailed studies of a small sub-catchment (Iron Cove, 14 km 2 ) and adjacent embayment (1.56 km 2 ) located on the southern shores of central Sydney Harbour (Fig.…”