Fernandez-cornudet, Christelle (2006) Devenir du Zn, Pb et Cd issus de retombées atmosphériques dans les sols, à différentes échelles d'étude. -Influence de l'usage des sols sur la distribution et la mobilité des métaux-. PhD thesis Environnement et gastronomie, Unité de sciences du sol de Versailles, INAPG 2006INAP0012.

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Abstract

The impacts of land-use on the fate of airborne metal pollutants in soils are still relatively unknown. Such impacts were examined in this work by a detailed study on the behaviour of 3 major metal pollutants (Zn, Pb, Cd) displaying a different mobility in soils. This work was performed both for surface horizons of a small region affected by industrial airborne metal fallout, and for a paired study site including two agricultural soils under long-term distinct different land use. The first soil was under permanent pasture (PP), the second under conventional arable land (CA). Both soils were located at comparable distance form the former emission source and developed under comparable pedogenetic conditions. The aim of this work was to i) quantify the proportions of endogenous and exogenous metals in soils, their distribution patterns in the soil horizons and in pedological compartments (microfabrics, aggregates, constituents) and ii) to identify the main mechanisms of metal migration and incorporation in soils. For this, detailed analyses of total concentrations of org. C, Fe, Zn, Pb, La and Cd were carried out, as well as macro- and micromorphological study, kinetic EDTA extractions, and Pb-isotopic composition studies. Ranking of soil parameters, characteristic for land use, influencing distributions and mobility of metals in soils was also aimed.
Our results revealed that 40 years after cessation of metallurgical activity, the actual distribution patterns of total metal contents in surface horizons did not corroborate the distribution pattern generally predicted by simple logarithmic modelling of atmospheric deposition as a function of the distance to the emission source and dominating wind directions. The Zn, Pb, and Cd contents in the upper 30 cm of soils under different land use differed notably according to soil pH, redox potential, soil texture or biological activity. For instance, in surface horizons of acid forest soils, a loss of about 80% of deposited Zn was found, whereas about 60% of Zn was shown to have migrated out of surface A horizon, ascribed to earthworm bioturbation in permanent grassland soils, compared to "only" 40% for Ap horizons of arable land. The ratio Zn/Pb and Cd/Pb were revealed as useful indicators to distinguish typical 'metal-fate vs land use' areas.
At the scale of the soil profile and soil horizons, a century of distinct different agricultural practices led to clear different phenoforms. In particular, different biological activity observed for the PP and CA soils modified biochemical cycling of metals, leading to different incorporation and mobility of metal pollutants. The two soils displayed clear different distribution patterns of exogenous metal stocks, with a marked accumulation in the Ap horizon of the CA soil (53% of Zn, 92% of Pb and Cd) whereas exogenous metals were more deeply incorporated in grassland soils (only 40% of Zn , 73% of Cd and 82% of Pb stocks at a depth <26 cm). Metal incorporation is significant until 80-cm depth in the PP soil. At the scale of soil fractions, in the PP soil, three types of soil fractions were shown to contribute to metal dynamics due to the high biological activity (aggregates of 50-100 μm and 2-20μm, and the <2-μm fraction). In the CA soil, only the 2-20μm and <2μm fractions were found predominantly implicated in metal retention and extractability.
The analysis of Pb-isotopic composition performed both on soil samples and EDTA extracts, was a powerful tool for providing detailed insight on the origin and the incorporation dynamics of anthropogenic lead in soils. It gave evidence for incorporation of anthropogenic Pb until 1-m depth in the PP soil and to about 60 cm in the CA soil. This isotopic approach was found perfectly complementary to current chemical analytical approaches used for studying metal fate in soils, by validating data on estimations of exogenous metal contents. It highlighted the necessity for careful considering pedological parameters in order to guarantee representativity of metal polluted soil samples in studies and to authorize a more pertinent assessment of environmental risks based only on total metal concentrations.

Table of content

Sommaire
LISTE DES FIGURES - i
LISTE DES TABLEAUX - V
INTRODUCTION - 1
CHAPITRE 1:
SYNTHÈSE BIBLIOGRAPHIQUE - 7
1. Le sol - 7
2. La contamination en éléments traces métalliques des sols - 9
2.1. Origine des ETM dans le sol - 9
2.2. Contamination et pollution des sols - 11
2.3. Distributions dans l'espace des polluants - 11
2.4. Distribution verticale des ETM à l'échelle du solum - 12
2.5. Distribution des ETM à l'échelle des constituants et leurs microstructures - 13
Les phyllosilicates - 13
Les oxy-hydroxydes de fer et manganèse - 13
Les carbonates et les phosphates - 13
Les matières organiques - 13
3. Principaux métaux étudiés - 16
3.1. Le Plomb - 16
3.2. Le Zinc - 17
3.3. Le cadmium - 18
CHAPITRE 2:
DÉMARCHES, OUTILS ET TECHNIQUES & SITE D'ÉTUDE - 21
1. Démarches - 21
1.1. Évaluation du devenir des ETM dans les sols par l'étude de la distribution de leurs teneurs totales en métaux à différentes échelles - 21
Distribution des éléments traces métalliques à l'échelle de la zone agricole - 21
Distribution des éléments traces métalliques à l'échelle des solums - 22
Distribution des éléments traces métalliques à l'échelle des fractions granulométriques des horizons - 22
Approche de la mobilité par des extractions chimiques - 23
1.2. Choix des polluants métalliques - 23
1.3. Choix des deux solums étudiés - 23
2. outils et techniques - 25
2.1. Distribution des polluants à l'échelle du périmètre agricole - 25
Le choix de la distribution des points de prélèvement dans l'ensemble de la zone agricole - 25
Mode de prélèvement et données acquises - 25
Traitement spatial de la pollution en métaux - 26
2.2. Distribution verticale des polluants et fonctionnement des sols à l'échelle du solum - 27
Évaluation de la distribution verticale du Zn et du Pb - 27
Caractérisation du fonctionnement du sol - 28
2.3. Approche de la spéciation des métaux dans les compartiments fonctionnels du sol - 28 i
Détermination des compartiments fonctionnels - 28
Détermination de la nature des compartiments fonctionnels dégagés et détermination du vecteur de transport des ETM dans les différents systèmes - 29
2.4. Différentes approches de la mobilité et évaluation des proportions endogènes et exogènes des ETM - 30
Utilisation du rapport Zn/Pb pour une vision dynamique de la mobilité des ETM à l'échelle d'un périmètre agricole - 30
Quantification des parts endogènes et exogènes des ETM et dynamique d'incorporation au sein d'un solum par l'approche typologique - 30
Cinétique d'extraction à l'EDTA: approche de la mobilité des polluants à l'échelle des horizons de sols - 31
Vérification de l'ensemble des conclusions par le biais de l'outil isotopique appliqué au plomb - 31
3. Description du site de Mortagne du Nord - 32
3.1. Localisation du site - 32
3.2. Historique de site - 33
3.3. Présentation des unités du périmètre d'étude - 34
3.4. Voies de communication - 35
3.5. Contexte pédologique - 36
CHAPITRE 3:
CONCENTRATIONS AND RATIOS OF ZN AND PB FOR ASSESSING THE FATE OF AIRBORNE METAL POLLUTION IN SOILS AS RELATED TO THEIR LAND MANAGEMENT - 39
1. Introduction - 39
2. Materials and Methods - 41
2.1. Historic - 41
2.2. Soils - 42
2.3. Sampling strategy - 43
2.4. Chemical analyses - 44
2.5. Geostatistical mapping procedure - 44
Multi-Gaussian Kriging (MGK) - 44
Factorial discriminant analysis (FDA) - 45
3. Results - 46
3.1. Mapping of Zn and Pb concentrations by MGK - 46
3.2. Spatial distribution maps of Zn and Pb concentrations in topsoils - 47
Zn concentration map - 49
Pb concentration map - 49
Zn/Pb concentration map - 49
Relating metal fate and land use by FDA - 50
4. Discussion - 51
4.1. Spatial distribution patterns of Zn and Pb concentrations in top soils - 51
4.2. Fate of Zn and Pb pollutants in relation to land use - 52
Well-drained forest soils - 52
Well-drained soils under arable land - 52
Moderately-and poorly drained soils under agriculture, poplar stand or humid forest - 53
5. Conclusion - 54
6. Références bibliographiques - 56
ii
CHAPITRE 4:
FATE OF AIRBORNE METAL POLLUTION IN SOILS AS RELATED TO AGRICULTURAL MANAGEMENT. 1. ZN & PB DISTRIBUTIONS IN SOIL PROFILES - 63
1. Summary - 63
2. Introduction - 63
3. Materials and methods - 65
3.1. Site conditions and selection of soils - 65
3.2. Soil sampling and analyses - 68
4. Results and Discussion - 69
4.1. Major morphological and chemical soil characteristics - 69
Macromorphology and physicochemical data - 69
Micromorphology - 72
4.2. Distribution of metal elements in soils - 74
Profiles of Zn and Pb concentrations - 74
Assessing incorporation of Zn and Pb with soil depth - 76
Metal stocks - 77
4.3. Mechanisms of metal mobility and quantification of metal pollution - 78
Premise and estimation of local geochemical background values - 78
Zn - Fe and Pb - Fe relationships in CA and PP - 79
Distribution of metal pollutants with depth - 81
5. Conclusions - 83
6. References - 85
CHAPITRE 5:
FATE OF AIRBORNE METAL POLLUTION IN SOILS AS RELATED TO AGRICULTURAL MANAGEMENT. 2. DISTRIBUTION AND MOBILITY OF ZN & PB IN SIZE FRACTIONS - 89
1. Summary - 89
2. Introduction - 89
3. Materials and methods - 92
3.1. Site - 92
3.2. Major soil characteristics - 93
3.3. Soil sampling and main physico-chemical analysis - 96
3.4. Physical fractionation - 96
3.5. Kinetic extraction of Zn and Pb with EDTA - 97
4. Results and discussion - 98
4.1. Distributions of Zn and Pb concentrations in horizons of PP and CA - 98
4.2. Physical fractionation and distribution of Zn and Pb - 100
Particle size fractionation - 100
Total Zn and Pb concentrations and stocks in size fractions - 101
4.3. EDTA extractability of Zn and Pb - 105
4.4. Soil aggregation and metal mobility - 108
5. Conclusions - 111
6. References - 113
iii
CHAPITRE 6:
LEAD MOBILITY IN SOILS UNDER PERMANENT GRASSLAND AND ARABLE LAND ESTIMATED BY LEAD ISOTOPIC COMPOSITIONS - 117
1. Introduction - 117
2. Material and method - 119
2.1. Study site - 119
Soil selection - 119
Soil characteristics - 119
2.2. Soil Sampling - 121
2.3. Analysis - 121
Total element concentration - 121
EDTA extractions - 121
Isotopic measurements - 122
3. Results - 122
3.1. Physico-chemical data in the PP and CA soils - 122
3.2. Geochemical element and isotopic profiles - 123
4. Discussion - 126
4.1. Data preparation and anthropogenic pool calculation - 126
4.2. Origin of the anthropogenic lead pool - 128
4.3. Migration and origin of lead related to land use - 129
5. Conclusion - 133
6. References - 134
CHAPITRE 7:
DEVENIR DU CADMIUM ISSU DE RETOMBÉES ATMOSPHÉRIQUES DANS LES SOLS - 139
1. Introduction - 139
2. Distribution de Cd à l'échelle du périmètre agricole - 140
3. Distribution du Cadmium à l'échelle du solum - 143
3.1. Distribution du Cd dans les sols - 143
3.2. Quantification de l'incorporation d'une pollution - 145
Distribution - 145
Quantification de Cd exogène - 147
4. Distribution du cadmium à l'échelle des compartiments fonctionnels du sol - 148
4.1. Localisation et distribution du Cd - 149
4.2. Approche du risque - 151
5. Influence du mode d'occupation sur la distribution du Cd - 151
5.1. Distribution du Cd à l'échelle du périmètre agricole - 151
5.2. Distribution à l'échelle du solum de sol - 152
5.3. Distribution du Cd à l'échelle des agrégats de sol - 153
6. Conclusion - 154
CHAPITRE 8:
CONCLUSIONS - 155
PERSPECTIVES - 162
RÉFÉRENCES BIBLIOGRAPHIQUES - 163

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