Application of the buffer theory for evaluating attenuation and natural remediation of ionic pollutants in aquatic ecosystems

Igor Povar,Oxana Spinu

doi:10.1186/s13717-015-0043-z

Abstract

The main focus in this review is showing how to use the developed buffer theory for assessing and predicting the long-term phenomena of attenuation and natural remediation of ionic pollutants in contaminated aquatic ecosystems, as well as for analyzing the way by which metals move and transform within the environment, the distribution of metals in ecosystems, their deposition and cycling in the terrestrial environment. The buffer theory is based on the rigorous thermodynamic analysis of complex chemical equilibria under environmental conditions in aquatic ecosystems, as natural waters and soils. It has been established that both homogeneous and heterogeneous systems manifest a buffer action towards all their components. The buffer properties in relation to the solid phase components are amplified with an increase of solubility due to protolytic or complex formation equilibria in saturated solutions. It has been established that the buffer capacities of components are mutually proportional, whereas for heterogeneous systems these relationships depend on the stoichiometric composition of solid phases. The use of the developed buffer approach may yield extended knowledge and a deeper understanding of the processes that control the concentrations of components. A number of the important conclusions concerning the investigated buffer systems have been made. The obtained results are indented to provide researchers with a tool needed to help them to set reliable limits of ion (metal) levels in the environment.

Highlights

Risk assessment of heavy metals in ecosystems The basic requirements of the Ecological Risk Assessment (ERA) for metals are as follows: the chemical species of the metal in the environment, environmental conditions affecting those species as well as the presence of receptors of potential concerns (Chapman et al 2003; Williams 2005; Povar 2011).To understand the control of metal solution concentrations in ecosystems, one needs to understand the removal processes for involving compounds and phases (Povar 1996a, b, c; Povar and Spinu 2013a, b, c; Spinu and Povar 2013c)
4) Presence of ligands that form stable complexes with ions of the solid phase promotes the amplification of the buffer actions of the heterogeneous systems
5) Presented approach can be used for research of the buffer action in the case of formation of one or several other solid phases in natural waters

Summary

Introduction

Risk assessment of heavy metals in ecosystems The basic requirements of the Ecological Risk Assessment (ERA) for metals are as follows: the chemical species of the metal in the environment, environmental conditions affecting those species as well as the presence of receptors of potential concerns (Chapman et al 2003; Williams 2005; Povar 2011). In a number of published works, the methods for solving the problems of shift from chemical-analytical, descriptive characteristics of the systems to the quantitative study of their chemical equilibria by thermodynamic and computer modeling have been described These processes include the heterogeneous interaction of minerals and soil solution, homogeneous reactions of hydrolysis and complex formation, as well as the acid-base, redox, buffers, and other important soil properties. Most pertinent to the research proposed here is our own result (Fishtik and Povar 2006; Povar 1995, a, Povar 1996b, c, 2000a, b; Povar and Luca 2003, Povar and Spînu 2014e) Those studies dealt with developing metal-ligand buffer capacity theory both for homogeneous and heterogeneous multicomponent systems. The mass balance (MB) conditions in this system are formulated by the following equations: C0M

ΔCM þ

Aq i

Conclusions