Directly Predicting Water Quality Criteria from Physicochemical Properties of Transition Metals.

Ying Wang,Yunsong Mu,John P Giesy,Peifang Wang,Fengchang Wu,Chenglian Feng,Eddy Y Zeng,Cheng Chen,Xiaoli Zhao,Wei Meng,Haiqing Liao

doi:10.1038/srep22515

Abstract

Transition metals are a group of elements widespread in aquatic environments that can be hazardous when concentrations exceeding threshold values. Due to insufficient data, criteria maximum concentrations (CMCs) of only seven transition metals for protecting aquatic life have been recommended by the USEPA. Hence, it is deemed necessary to develop empirical models for predicting the threshold values of water quality criteria (WQC) for other transition metals for which insufficient information on toxic potency is available. The present study established quantitative relationships between recommended CMCs and physicochemical parameters of seven transition metals, then used the developed relationships to predict CMCs for other transition metals. Seven of 26 physicochemical parameters examined were significantly correlated with the recommended CMCs. Based on this, five of the seven parameters were selected to construct a linear free energy model for predicting CMCs. The most relevant parameters were identified through principle component analysis, and the one with the best correlation with the recommended CMCs was a combination of covalent radius, ionic radius and electron density. Predicted values were largely consistent with their toxic potency values. The present study provides an alternative approach to develop screening threshold level for metals which have insufficient information to use traditional methods.

Highlights

Due to the lack of data on toxic potency of metals, water quality criteria (WQC) for more than 50 other transition metals have not yet been promulgated by regulatory jurisdictions
Twenty-six descriptors of physicochemical properties were considered in constructing models to predict criteria maximum concentrations (CMCs) by use of single-parameter linear regressions (Table 1)
The difference between the CMC for Hg predicted by integrated radius (IR) and the recommended value was within ± 0.20, whereas differences for all other metals were within an order of magnitude. These results suggest that the model based on IR is capable of reliably predicting CMCs for transition metals

Summary

Introduction

Due to the lack of data on toxic potency of metals, WQC for more than 50 other transition metals have not yet been promulgated by regulatory jurisdictions. After the most relevant parameters were selected, a model was established to predict CMCs of 49 other transition metals in the fourth, fifth, sixth and seventh periods of the Periodic Table of the elements, including the Lanthanide and Actinide Series.

Results

Conclusion