Comparison of two modeling frameworks for unifying the toxicant-affected percentage of aquatic species, individuals, and time into a single metric.

To address time-variable exposure to toxicants, this work compares simple and complex approaches to unifying the affected percentage of aquatic species, individuals, and time into a single metric. The simple approach uses only information on the probability distribution of exposure concentrations, a species sensitivity distribution (SSD) of chronic values, and the distribution of tolerance within species. The complex approach involves time-series simulation with a kinetics-based toxicity model coupled with a population model for each species in the SSD.

Method Development for a Short-Term 7-Day Toxicity Test with Unionid Mussels.

The US Environmental Protection Agency's short-term freshwater effluent test methods include a fish (Pimephales promelas), a cladoceran (Ceriodaphnia dubia), and a green alga (Raphidocelis subcapitata). There is a recognized need for additional taxa to accompany the three standard species for effluent testing. An appropriate additional taxon is unionid mussels because mussels are widely distributed, live burrowed in sediment and filter particles from the water column for food, and exhibit high sensitivity to a variety of contaminants.

Applying adaptive management and lessons learned from national assessments to address logistical challenges in the National Wetland Condition Assessment.

The National Wetland Condition Assessment (NWCA) is one of a series of probability-based National Aquatic Resource Surveys (NARS) conducted by the U.S. Environmental Protection Agency (USEPA) to provide a comprehensive assessment of the condition of the Nation's waters.

Application of a Fixed Monitoring Benchmark Approach to Evaluate Attainment of Time-Variable Water Quality Criteria: Copper Biotic Ligand Model as a Case Study.

In 2007, the Biotic Ligand Model (BLM) became the basis for the US Environmental Protection Agency (USEPA) freshwater water quality criteria (WQC) for Cu. Applying the BLM typically results in time-variable WQC, which are not unique to the BLM; they result from any criteria approach that depends on water chemistry (e.g.

Development of bioassessment-based benchmarks for iron.

Current water-quality criteria for metals typically are derived from toxicity tests with the metal dissolved in clean laboratory water. Estimating the toxicity of iron from such tests, however, is extremely difficult because of the complex solubility and toxicity characteristics of the ferrous and ferric forms of the metal in freshwater. Consequently, a criterion for dissolved iron in freshwater derived from standard laboratory bioassays may not accurately describe the actual bioavailability and toxicity of this metal.

Integrating chemical and biological criteria.

We present a system to derive benchmarks for protection of aquatic organisms that, as chemical criteria, promotes regulation of contaminants and, as biological criteria, focuses on an endpoint that adequately represents species abundance. The proposed method utilizes quantile regression to quantify the decline in maximum number of organisms with increasing contaminant concentrations. This limiting function then is applied to project the contaminant concentration associated with a threshold number of organisms.

A simple comparison of mass spectral search results and implications for environmental screening analyses.

A simple assessment of the ability of environmental laboratories to perform automated library searching procedures on mass spectra of unknown pollutants was conducted. In this assessment, 10 laboratories analyzed a hexane solution containing eight organic chemicals using gas chromatography/mass spectrometry and searched their acquired mass spectral data against mass spectral reference libraries. The search results were used to evaluate the similarity of the lists of tentative identifications (TIDs) among the laboratories and to compare the observed searching success to the searching success reported in the literature using high-quality mass spectral data.