Calculation of critical loads for cadmium, lead and mercury Commissioned by the Dutch Ministries of Agriculture, Nature and Food Quality and of Housing, Spatial Planning and Environment 2 Alterra-report 1104 Calculation of critical loads for cadmium, lead and mercury Background document to a Mapping Manual on Critical Loads of cadmium, lead and mercury W. de Vries G. Schütze S. Lofts E. Tipping M. Meili P. F.A.M. Römkens J.E. Groenenberg Alterra-report 1104 Alterra, Wageningen, 2005 ABSTRACT Vries, W. de, G. Schütze, S. Lofts, E. Tipping, M. Meili, P.F.A.M. Römkens and J.E. Groenenberg, 2005. Calculation of critical loads for cadmium, lead and mercury. Background document to a Mapping Manual on Critical Loads of cadmium, lead and mercury. Wageningen, Alterra, Alterra-report 1104. 143 blz.; 1 fig; 13 tables.; 53 refs This report on heavy metals provides up-to-date methodologies to derive critical loads for the heavy metals cadmium (Cd), lead (Pb) and mercury (Hg) for both terrestrial and aquatic ecosystems. It presents background information to a Manual on Critical Loads for those metals. Focus is given to the methodologies and critical limits that have to be used to derive critical loads can be derived for Cd, Pb and Hg in view of : (i) ecotoxicological effects for either terrestrial or aquatic ecosystems.and (ii) human health effects for either terrestrial or aquatic ecosystems. For Hg, a separate approach is described to estimate critical levels in precipitation in view of human health effects due to the consumption of fish. The limitations and uncertainties of the approach are discussed including: (i) the uncertainties and particularities of the steady-state models used and (ii) the reliability of the approaches that are applied to derive critical limits for critical total dissolved metal concentrations in soil solution and surface water. Keywords: heavy metals, critical loads, critical levels, leaching, critical limits, transfer functions, terrestrial ecosystems, aquatic ecosystems, lead, cadmium, mercury ISSN 1566-7197 This report can be ordered by paying € 21,- to bank account number 36 70 54 612 by name of Alterra Wageningen, IBAN number NL 83 RABO 036 70 54 612, Swift number RABO2u nl. Please refer to Alterra-report 1104. This amount is including tax (where applicable) and handling costs. © 2005 Alterra P.O. Box 47; 6700 AA Wageningen; The Netherlands Phone: + 31 317 474700; fax: +31 317 419000; e-mail: [email protected] No part of this publication may be reproduced or published in any form or by any means, or stored in a database or retrieval system without the written permission of Alterra. Alterra assumes no liability for any losses resulting from the use of the research results or recommendations in this report. 4 Alterra-report 1104 [Alterra-report 1104/januari 2005] Contents Preface 7 Summary 9 1 Introduction 13 1.1 Background of the report 13 1.2 Aim and contents of the report 14 2 General methodological aspects of mapping critical loads of heavy metals 15 2.1 Calculation of different types of critical loads in dependence on the receptors and regarded metals 15 2.2 Differences between the guidance document and the manual 19 3 Terrestrial ecosystems 21 3.1 Simple steady-state mass balance model and related input data 21 3.1.1 Steady-state mass balance model 21 3.1.2 Heavy metal removal from the topsoil by net growth and harvest of plants 23 3.1.3 Critical leaching of heavy metals from the topsoil 25 3.2 Critical dissolved concentrations of Cd, Pb and Hg in terrestrial ecosystems28 3.2.1 Critical dissolved metal concentrations in view of critical metal contents in plants 28 3.2.2 Critical limits of Cd, Pb and Hg aiming at ground water protection 30 3.2.3 Critical dissolved concentrations of Cd and Pb related to ecotoxicological effects 30 3.2.4 Critical limits of Hg related to ecotoxicological effects in soils 36 4 Aquatic ecosystems 39 4.1 Critical Loads of lead and cadmium 39 4.1.1 Simple steady-state mass balance model and related input data 39 4.1.2 Critical total cadmium and lead concentrations in aquatic ecosystems 41 4.2 Critical levels of mercury in precipitation 45 4.2.1 Derivation of critical levels of mercury in precipitation referring to a standard fish 45 4.2.2 Derivation of critical levels of mercury in precipitation referring to other organisms 47 5 Evaluation 49 5.1 Derivation of critical Cd and Pb contents for soil 49 5.2 Limitations in the present approach and possible refinements 51 Literature 55 Appendices 1 Critical loads of heavy metals - definitions and symbols 63 2 Derivation of critical limits for soil from quality criteria for crops 67 3 Derivation of metal contents in soil from food quality criteria for animal products or acceptable daily intakes by animals 75 4 Considerations about an appropriate effects-based limit for the concentration of Cd in wheat from the viewpoint of human health effects 87 5 Derivation of critical loads for lead and mercury from food quality criteria 91 6 Heavy metal release by weathering in the mineral topsoil 93 7 Transfer functions for conversion of metal concentrations in different soil phases 99 8 Calculation of critical free Cd and Pb concentrations in soil drainage water related to ecotoxicological effects 111 9 Calculation of critical total Cd and Pb concentrations in soil drainage water related to ecotoxicological effects 115 10 Calculation of a critical steady state pH, assessment of actual pH values and relationships between various pH estimates 123 11 Assessment of DOC concentrations 129 12 Calculation of critical total Cd and Pb concentrations in surface water related to ecotoxicological effects 133 13 Transfer functions of Hg in aquatic ecosystems 137 6 Alterra-report 1104 Preface The development of methodologies to calculate critical loads for heavy metals has a long history and started about ten years ago. The first initiative was taken by the Ministry of Environment in the Netherlands, who approached the main author of this report to develop effects based calculation approaches for the calculation of critical loads of heavy metals in terrestrial and aquatic ecosystems. The idea was that, in analogy to critical loads for nitrogen and acidity, this approach would be valid for use in the context of the Convention on Long Range Transboundary Air Pollution (CLRTAP). In the mid of the 1990’s, preliminary methods were presented at various meetings of the Coordinatation Centre of Effects of the ICP Modelling and Mapping, being part of the CLRTAP. This led in 1998 to two “Manuals” for calculation of critical loads of heavy metals in terrestrial ecosystems and aquatic ecosystems, headed by the main author of this document. These methods have been applied in national studies and discussed at international workshops in 1997 in Bad Harzburg and in 1999 in Schwerin. An “Expert Panel on Heavy Metals” was set up, focusing on the derivation of critical limits for heavy metals and on transfer functions for metals from soil solid phase to soil solution and vice versa. These methods were intensively discussed at various meetings in Bratislava (2000), Berlin (2002), Strausberg (2003) and Potsdam (2004). The final agreement achieved at the last meeting led to a chapter (5.5) on Critical Loads of cadmium, lead and mercury in the ICP’s Manual for Modelling and Mapping Critical Loads & Levels (UBA 2004). This report presents background information to that “manual” chapter. Major parts of the background information are included in the annexes of this report. The report was written by an interdisciplinary team of researchers in the “Expert Panel on Heavy Metals” under the co-ordination of Alterra. Institutes involved were: - Alterra Green World Research, Droevendaalse steeg 3, P.O. Box 47, NL-6700 AA Wageningen, The Netherlands: Dr. Wim de Vries, Dr. Paul Römkens and Ir. Bert Jan Groenenberg. - Federal Environmental Agency Berlin, P.O. Box 330022, D-14191 Berlin, Germany / ÖKO-DATA Strausberg. Ir. Gudrun Schütze - Centre for Ecology and Hydrology (CEH), Lancaster Environment Centre, Library Avenue Bailrigg, Lancaster LA1 4AP, United Kingdom: Dr. Stephen Lofts and Prof. Dr. Edward Tipping. - Stockholm University, Institute of applied Environmental research (ITM), SE- 10691 Stockholm, Sweden. Dr. Markus Meili. The overall co-ordination and editing of this report was carried out by Wim de Vries in close cooperation with Gudrun Schütze. For colleagues who like to know more specific details on several aspects, reference is made to the following co-authors: - Stephen Lofts: Critical dissolved free Cd and Pb concentrations related to ecotoxicological effects: Part of Section 3.2.3 and Annex 8 Alterra-report 1104 7 - Edward Tipping: Calculation of critical total Cd and Pb concentrations in soil solution and surface water with the chemical speciation model WHAM: Part of Section 3.2.3, Annex 9 and 12. - Markus Meili: Hg critical limits, critical loads (soils) and critical levels in precipitation (surface waters): Section 3.2.4, 4.2 and Annex 13. This report has been written with the support of many other colleagues and we thus thankfully acknowledge the following Ministries, Institutes and Scientists: - The Dutch Ministries of Housing, Spatial Planning and Environment (VROM) and of Agriculture, Nature and Food quality (LNV), the German Ministry of the Environment, Nature Conservation and Nuclear Safety and the UK Department of the Environment, Food and Rural Affairs for financial support. - Dr. Ludwig de Temmerman of the “Centrum voor onderzoek in diergeneeskunde en agrochemie C.O.D.A” in Belgium for information on the relation between atmospheric deposition and plant metal contents. - The “Expert Panel on Critical loads of Heavy Metals” consisting of Prof. Michael Ashmore, Dr.