Site‐specific probabilistic ecological risk assessment of a volatile chlorinated hydrocarbon‐contaminated tidal estuary

Abstract

Groundwater contaminated with volatile chlorinated hydrocarbons (VCHs) was identified as discharging to Penrhyn Estuary, an intertidal embayment of Botany Bay, New South Wales, Australia. A screening-level hazard assessment of surface water in Penrhyn Estuary identified an unacceptable hazard to marine organisms posed by VCHs. Given the limitations of hazard assessments, the present study conducted a higher-tier, quantitative probabilistic risk assessment using the joint probability curve (JPC) method that accounted for variability in exposure and toxicity profiles to quantify risk (delta). Risk was assessed for 24 scenarios, including four areas of the estuary based on three exposure scenarios (low tide, high tide, and both low and high tides) and two toxicity scenarios (chronic no-observed-effect concentrations [NOEC] and 50% effect concentrations [EC50]). Risk (delta) was greater at low tide than at high tide and varied throughout the tidal cycle. Spatial distributions of risk in the estuary were similar using both NOEC and EC50 data. The exposure scenario including data combined from both tides was considered the most accurate representation of the ecological risk in the estuary. When assessing risk using data across both tides, the greatest risk was identified in the Springvale tributary (delta=25%)-closest to the source area-followed by the inner estuary (delta=4%) and the Floodvale tributary (delta=2%), with the lowest risk in the outer estuary (delta=0.1%), farthest from the source area. Going from the screening level ecological risk assessment (ERA) to the probabilistic ERA changed the risk from unacceptable to acceptable in 50% of exposure scenarios in two of the four areas within the estuary. The probabilistic ERA provided a more realistic assessment of risk than the screening-level hazard assessment.

Development process and perspective on ecological risk assessment

“…Although there may only be one pressures of concern, at a regional scale the other stressor acting upon the assessment endpoints are to be considered [27]. The traditional risk characterization method might not be efficient when conducting a regional scale risk assessment [16,21,55]. At the regional scale, there are many sources, pressures, habitats and endpoints that must be considered and often times there are multiple sources for a single stressor [54,34,9].…”

Regional multi-compartment ecological risk assessment: Establishing cadmium pollution risk in the northern Bohai Rim, China

“…The JPC method of integrating the exposure and effects distributions in the common axis was used to determine the likelihood of adverse ecological effects (Hunt et al, 2010). The specific assessment end point was designed to ensure the protection of at least 95% of aquatic, terrestrial and benthic species (HC 5 ).…”

A tiered ecological risk assessment of three chlorophenols in Chinese surface waters

“…Probabilistic ecological risk assessments (PERAs), which qualify and quantify ecological risks through exposure and effect probability distributions, are regarded as an improvement on the HQ approach and, thus, recommended for later tiers in the ecological risk assessment (ERA) process (Solomon 1996). Because PERAs can better describe the likelihood of exceeding the effect thresholds and the risk of adverse effects (Solomon and Sibley 2002), this approach has been adopted by a number of researchers (Giesy et al 1999;Hall et al 2000;Zolezzi et al 2005;Brain et al 2006;Hunt et al 2010). To obtain more reliable results for decision-making processes on site-specific contamination, some researchers and scientific institutions have suggested the use of a tiered approach, ranging from simple deterministic methods to probabilistic methods, for risk characterization, (Solomon et al 2000;Zolezzi et al 2005;Wang et al 2009).…”