Impact of Soil Properties on Critical Concentrations of Cadmium, Lead, Copper, Zinc, and Mercury in Soil and Soil Solution in View of Ecotoxicological Effects

Abstract

Use of critical metal loads in assessing the risk of metal inputsConcern about the input of metals to terrestrial ecosystems is related to: (i) the ecotoxicological impact on soil organisms and plants (e.g. Bringmark et al. 1998;Palmborg et al. 1998) and also on aquatic organisms due to runoff to surface water and (ii) the uptake via food chains into animal tissues and products, which may result in health effects on animals and humans (e.g. Clark 1989). Effects on soil organisms, including micro-organisms/macrofungi and soil fauna, such as nematodes and earthworms, are reduced species diversity, abundance and biomass and changes in microbe mediated processes (e.g. Bengtsson and Tranvik 1989;Giller et al. 1998;Vig et al. 2003). Effects on vascular plants are reduced development and growth of roots and shoots (toxicity symptoms), elevated concentrations of starch and total sugar, decreased nutrient contents in foliar tissues (physiological symptoms) and decreased enzymatic activity (biochemical symptoms) (e.g. Prasad 1995;Das et al. 1997). A review of these phytotoxic effects is given by Balsberg-Påhlsson (1989). Effects on aquatic organisms, including algae, crustacea and fish, include effects on gill function (e.g. Sola et al. 1995), nervous systems (e.g. Baatrup 1991), and growth and reproduction rates (e.g. Mance 1987). Environmental quality standards or critical limits (often also denoted as predicted No effect Concentrations or PNECs) for metals in soils and surface waters related to those effects serve as a guide in the environmental risk assessment process for those substances. 3Next to effects on soil organisms, metals may be transferred in food chains to cause effects on animals and humans (secondary poisoning). This may affect (i) humans by reducing food quality of crops and animal products and (ii) animal health through the accumulation in organs of cattle, birds and mammals (secondary poisoning). Heavy metal accumulation in food chains is specifically considered important with respect to cadmium (Cd) and mercury (Hg), and to a lesser extent for lead (Pb), for all of which no biological functions are known (e.g. Clark 1989). The only exception known is that Cd appears to be essential under Zn-limiting conditions for one marine diatom (Lee et al. 1995).One risk assessment approach, used successfully in international negotiations on the reduction of atmospheric deposition of pollutants, is to determine the maximum load of constant atmospheric pollution that causes no or tolerable damage ("long-term acceptable load" or "critical load"). A major advantage of this method is that it can be used to optimise the protection of the environment for a given international investment in pollution control by minimising the difference between present loads and critical loads on a regional scale. A major difficulty is the quantification of the relationship between atmospheric emission, deposition and environmental effects.The method to calculate critical loads of metals is based on the balance of all relevant metal flu...

Lability, solubility and speciation of Cd, Pb and Zn in alluvial soils of the River Trent catchment UK

“…. 7 Free ion concentrations, log (M 2+ ) in soil pore waters centrifuged from Trent catchment soils in relation to critical limits published by de Vries et al (2007). Pore water speciation is plotted against the pore water pH whilst model prediction is plotted against soil pH.…”

Modelling the effects of copper on soil organisms and processes using the free ion approach: Towards a multi-species toxicity model

“…Thakali and co-workers 71 (Thakali et al, 2006a, b) have developed BLMs to predict the effects of copper on 72 plants, invertebrates and microbial processes, based on testing using a set of European 73 soils of contrasting soil chemistries Oorts et al, 2006;Criel et 74 al., 2008). 75 An alternative approach to considering bioavailability effects has been taken by Lofts 76 and co-workers (Lofts et al, 2004;De Vries et al, 2007). Termed the free ion 77 approach, this method considers the toxic effect to depend upon the free metal ion in 78 soil solution, and also on the amounts of other solution cations that 'protect' the 79 organism against metal toxicity.…”

“…The variables considered are thus the same as would 80 be considered by the BLM, but the expression describing the loading of the biotic 81 ligand with toxic metal is replaced with an empirical function, and the 'biotic ligand' is 82 not explicitly considered. The free ion approach was used to derive functions giving 83 critical limits (risk threshold concentrations) for copper and other metals in soils 84 directly from existing literature (Lofts et al, 2004;De Vries et al, 2007). Because of 85 the limited nature of the available data, a number of key assumptions were made in 86 the derivation of the critical limit functions.…”

Assessment of cadmium, zinc and lead contamination in leaf and root of four various species

“…Concentrations of Zn found in contaminated soils frequently exceed the limits required to be as a nutrient and may cause phytotoxicity. Zn concentrations in the range of 150-300 mg/kg have been measured in polluted soils (Devries et al 2002;Warne et al 2008). High levels of Zn in soil inhibit many metabolic functions of plants, resulting in retarded growth and cell senescence.…”