The Role of Traditional and Novel Toxicity Test Methods in Assessing Stormwater and Sediment Contamination

Abstract

Abstract:Traditional effluent and ambient water column toxicity tests have been used widely for evaluating the contamination of stormwaters and sediments. These assays consist of a routine bioassay exposure design of 1 to 9 days using freshwater and marine/estuarine species known to be sensitive to a wide range of toxicants. While effluent toxicity may be indicative of sediment or stormwater toxicity in the receiving system, the exposure is different, and therefore toxicity cannot be readily predicted. Traditional, standardized, whole effluent toxicity (WET) test methods have been used effectively and also misused in evaluations of whole sediments, pore (interstitial) water, elutriates (extracts), and stormwaters. Results show these methods to be very sensitive to sediment and stormwater toxicity. These traditional toxicity tests are predictive of instream sediment or stormwater effects where significant contamination exists or where exposure concentrations are similar. Modifications of these standardized test methods to include sediments or pore waters have been shown to be as sensitive as short-term, whole sediment toxicity tests using benthic species. However, the added complexity of sediments and stormwaters (e.g., partitioning, high Kow compound bioavailability, suspended solids, sporadic exposures, multiple exposure pathways) dictates that traditional toxicity test applications be integrated into a more comprehensive assessment of ecologically significant stressors. The limitations of the WET testing approach and optimized sample collection and exposure alternatives are frequently ignored when implemented. Exposure to sporadic pulses of contaminants (such as in stormwaters) often produce greater toxicity than exposure to constant concentrations. Lethality from short-term pulse exposures may not occur for weeks after the high flow event due to uptake dynamics. Pore water and elutriate exposures remove sediment ingestion routes of exposure and alter natural sorption/desorption dynamics. Traditional toxicity tests may not produce reliable conclusions when used to detect the adverse effects of: fluctuating stressor exposures, nutrients, suspended solids, temperature, UV light, flow, mutagenicity, carcinogenicity, teratogenicity, endocrine disruption, or other important subcellular responses. This reality and the fact that ecologically significant levels of high K ow compounds may not produce short-term responses in exposures dictates that additional and novel assessment tools be utilized in order to protect aquatic ecosystems. This inablilty to predict effects is largely a result of the complex biological response patterns that result from various combinations of stressor magnitudes, duration, and frequency between exposures and also the interactions of stressor mixtures, such as syngergistic effects of certain pesticides, metals, and temperature. In watersheds receiving multiple sources of stressors, accurate assessments should define spatial-temporal profiles of exposure and effects using a range * Correspon...

Assessing contaminated sediments in the context of multiple stressors

“…In addition, increasing evidence suggests important physical, biological, and chemical linkages aside from the traditional upstream-downstream and benthic-pelagic couplings that act through a range of interfaces including terrestrial-aquatic, surface-subsurface, lake-stream, river-floodplain, and marine-freshwater [26]. Human activities may interfere with these linkages causing changes to hydrological processes that affect the balance between groundwater and surface water, the permanence of water bodies, nutrient cycling, acidification, and runoff [173][174][175][176]. Modifications to these processes may result in cascading effects from multiple stressors [177,178].…”

“…It may be that in heavily human-dominated watersheds, one stressor dominates the system, such as habitat or flow, or many stressors are tightly linked, such as impervious area, flow flashiness, and contaminated runoff [186,187]. For example, note the widely reported relationship between degraded aquatic communities in watersheds where impervious areas are greater than 8 to 20% of the landscape [174,175,[188][189][190][191][192]. These areas are subject to multiple dominant stressors of habitat degradation, flashy flows, and elevated temperature, sunlight, solids, metals, and synthetic organics.…”

Size dependent elemental composition of road-associated particles

“…In a review of stormwater and sediment toxicity, urban stormwater toxicity was significantly attributed to metals through Toxicity Identification Evaluations (TIE) (Kayhanian et al, 2008;Burton et al, 2000). Multi-lane divided highway stormwater was considered severely toxic in 20% of evaluated cases, compared to only 1% of urban stormwater (Marsalek et al, 1999).…”

Avoidance of contaminated sediments by an amphipod (Melita plumulosa), A harpacticoid copepod (Nitocra spinipes), and a snail (Phallomedusa solida)

“…Static toxicity tests rarely reflect the dynamic and heterogeneous natural environment [6] and, therefore, do not always adequately mimic an organism's exposure to contaminants, meaning that these methods may lack ecological significance [1,16]. Despite this, many researchers and regulatory guidelines Environmental Toxicology and Chemistry, Vol.…”