Development of Multiple Linear Regression Models for Predicting Chronic Iron Toxicity to Aquatic Organisms

摘要

We developed multiple linear regression (MLR) models for predicting iron (Fe) toxicity to aquatic organisms for use inderiving site‐specific water quality guidelines (WQGs). The effects of dissolved organic carbon (DOC), hardness, and pH on Fetoxicity to three representative taxa (Ceriodaphnia dubia, Pimephales promelas, and Raphidocelis subcapitata) were evaluated.Both DOC and pH were identified as toxicity‐modifying factors (TMFs) for P. promelas and R. subcapitata, whereas only DOCwas a TMF for C. dubia. TheMLR models based on effective concentration 10 and 20 values were developed and performedreasonably well, with adjusted R~2 of 0.68–0.89 across all species and statistical endpoints. Differences among species in the MLRmodels precluded development of a pooled model. Instead, the species‐specific models were assumed to be representative ofinvertebrates, fish, and algae and were applied accordingly to normalize toxicity data. The species sensitivity distribution (SSD)included standard laboratory toxicity data and effects data from mesocosm experiments on aquatic insects, with aquatic insectsbeing the predominant taxa in the lowest quartile of the SSD. Using the European Union approach for deriving WQGs,application ofMLR models to this SSD resulted inWQGs ranging from 114 to 765 μg l~(?1) Fe across the TMF conditions evaluated(DOC: 0.5–10mg l~(?1); pH: 6.0–8.4), with slightly higher WQGs (199–910 μg l~(?1)) derived using the US Environmental ProtectionAgency (USEPA) methodology. An important uncertainty in these derivations is the applicability of the C. dubia MLR model (nopH parameter) to aquatic insects, and understanding the pH sensitivity of aquatic insects to Fe toxicity is a research priority. AnExcel‐based tool for calculating FeWQGs using both European Union and USEPA approaches across a range of TMF conditionsis provided.