Role of Natural Organic Matter in the Mobility of Aluminium Ions in Rivers in the Limousin Region (France) Gilles Guibaud, Cécile Gauthier, Josiane Ayele
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Role of natural organic matter in the mobility of aluminium ions in rivers in the Limousin region (France) Gilles Guibaud, Cécile Gauthier, Josiane Ayele To cite this version: Gilles Guibaud, Cécile Gauthier, Josiane Ayele. Role of natural organic matter in the mobility of aluminium ions in rivers in the Limousin region (France). Agronomie, EDP Sciences, 2000, 20 (5), pp.577-590. 10.1051/agro:2000152. hal-00886065 HAL Id: hal-00886065 https://hal.archives-ouvertes.fr/hal-00886065 Submitted on 1 Jan 2000 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. 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Agronomie 20 (2000) 577–590 577 © INRA, EDP Sciences 2000 Original article Role of natural organic matter in the mobility of aluminium ions in rivers in the Limousin region (France) Gilles GUIBAUD*, Cécile GAUTHIER, Josiane AYELE Laboratoire des Sciences de l'Eau et de l'Environnement, Faculté des Sciences, 123 avenue Albert Thomas, 87060 Limoges Cedex, France Agriculture and Environment (Received 1 September 1999; revised 9 May 2000; accepted 25 May 2000) Abstract – In order to investigate, in the Limousin (France), the role of organic matter in aluminium mobility in soil towards rivers and its chemistry in water, three different A1 horizons of an acidic brown-earth soil planted with three dif- ferent types of trees (chestnuts (Castanea sativa) over 100 years old, young Douglas fir (Pseudotsuga menzesii), and old Douglas fir) were selected, as well as five points on major rivers (Vienne, Vézère, Gartempe, Grande Creuse) in the area. The aluminium content of the rivers in the Limousin was evaluated. Characterisation of horizons, speciation of alumini- um, and laboratory experiments on aluminium release from soil columns pointed out the probable origin of aluminium in the rivers and the role of organic matter in its mobility. This study showed that many rivers exhibit aluminium con- centrations higher than 110 ppb, very low mineralization and an acid pH. The high concentration in aluminium may be due to the presence of coniferous forests on the river catchment. In an area preserved from human activity, the natural organic matter prevents aluminium precipitation despite the pH conditions (close to 5.5–6) which favour insoluble forms. On the contrary, when some physico-chemical conditions of the river change (increase in pH and supply of organic mat- ter due to slight human or agricultural pollution) the aluminium may be removed, probably by precipitation with the organic matter. aluminium / water quality / organic matter / forest Résumé – Rôle de la matière organique naturelle dans la mobilité de l’aluminium dans les cours d’eau en Limousin (France). Pour étudier le rôle de la matière organique, en Limousin (France), sur la mobilité de l'aluminium des sols vers les cours d’eau et sa chimie dans l’eau, les trois horizons A1 d'un sol brun acide planté de trois forêts dif- férentes (châtaigniers (Castanea sativa), jeunes Douglas (Pseudotsuga menzesii), Douglas centenaires) et cinq points sur quatre des principales rivières (Vienne, Vézère, Gartempe, Grande Creuse) de la région ont été sélectionnés. L'état de contamination par l'aluminium de plusieurs rivières de la région Limousin est étudié. L’origine probable de l’aluminium dans les cours d’eau et le rôle de la matière organique dans la mobilité de l'aluminium sont montrés et étudiés à partir de la caractérisation des sols, de la spéciation de l'aluminium, et d’expériences de laboratoire réalisées principalement en colonne de sols. Certaines rivières présentent une concentration en aluminium supérieure à 110 ppb, une très faible Communicated by Isabelle Lamy * Correspondence and reprints [email protected] 578 G. Guibaud et al. minéralisation et un pH acide. La forte concentration en aluminium est probablement due à la présence de nombreuses surfaces boisées en conifères sur le bassin versant. Dans les zones préservées des pollutions domestiques ou agricoles, la matière organique présente empêche la précipitation et la disparition de l'aluminium malgré des pH défavorables aux formes solubles. À l'opposé, quand les conditions physico-chimiques des eaux changent sous l'effet d'une pollution domestique ou agricole diffuse (apport de matière organique, augmentation du pH) l'aluminium peut disparaître, proba- blement par des phénomènes de coagulation floculation. aluminium / qualité des eaux / matière organique / forêt 1. Introduction aluminium. Thomas et al. [27] have shown the influence of soil, geology and relief on stream acid- ity in the Vosges. They have shown that at base Soil organic matter which results from the bio- flow, stream water acidity depends primarily on the logical and chemical decomposition of litter plays a bedrock and the soil content of weatherable miner- major role in the mobility of the aluminium ion in als that neutralize acidity. As a consequence, much soil and toward rivers [11]. Aluminium in the soil is damage may be caused to aquatic life. The present in different forms: adsorbed onto particles, Limousin presents some characteristics similar to complexed with organic matter or anions, precipi- the Vosges: “poor” soil on a granite platform, acid tated as nodules, integrated into the crystalline streams with low mineralization and a high density structure of clays [11]. Some complexing sites on of resinous trees which is increasing every year natural organic matter have been evidenced, notably (18 km2?y-1 for Limousin [9]). In the Limousin, for soil fulvic acids: sites analogous to that of sali- Douglas culture leads to soil modifications such as cylic acid (very widespread) and phenolic sites acidification, increase in organic matter concentra- (widespread but rarer) [12]. In soil, the complex tion and aluminium mobility [13, 14]. Douglas fir formed between aluminium and fulvic acids are cultures lead to less acidification than other species chemically stable [19]. In stream water, aluminium of conifer such as Norway spruce [3]. bound to organic matter may stay in solution even Up to now, in the Limousin, no studies have been if the pH conditions should lead to its precipitation carried out on the aluminium content of streams and [28], but it is the physico-chemical conditions of the behaviour of this element in water. The aim of rivers that control the forms and the concentration this study is to investigate the state of contamina- of aluminium in water. For example, in a very acid tion by aluminium of some Limousin rivers, the river highly polluted by aluminium, soluble alu- behaviour and fate of aluminium in water are also minium precipitates when the pH becomes less examined, in order to show the role of organic mat- acidic (pH > 5.5–6). As a consequence, preci- ter in its mobility from soil towards streams and in pitates of amorphous aluminium can be found in its behaviour in stream water. river sediment [20]. The high concentrations of aluminium in soil or in stream water due to coniferous cultivation on 2. Materials and methods poor soil and/or acid rain [10, 30] may lead to toxic effects on trees [4] or on aquatic life [18]. 2.1. Aluminium in the rivers In France several studies have shown in the Vosges and/or Ardennes [8, 21, 23, 24] the impact of acid rain and intensive forestry on soil and 2.1.1. Characteristics of the river sections studied stream acidification. Several streams in the Vosges Table I gives some characteristics of the river show very acidic pHs and a high concentration of waters which were chosen for this study. Mobility of aluminium in river water 579 Table I. Location and characteristics of the studied rivers. River Vienne Vienne Vézère Grande Creuse Gartempe Location Peyrelevade Royère Bugeat Clairavaux Maisonnisses Altitude (m) 805 260 702 665 562 Geology Granite at 2 Granites Granite with Anatexites with Granite with micas biotites or with cordierite biotites 2 micas Granites Vegetation Forest End of woody Forest Forest Moor area – Moor Forest Moor Peat bog Grassland Peat bog km from spring 4 89 24 4.5 4 Size of 22 1150 75 12 35 catchment (km2) Annual average 1.8 25.2 4.5 1.2 0.18 flow m3?s–1 Quality * 1 A 2/1B 1A 1A/1B 1A/1B Very Good Passable-Good Very Good Good Good * According to French Water Agency criterions. Agriculture and Environment These streams cross the same kind of area: gran- sampled in September 1993, 20 km to the south of ite platform and highly wooded area with a high Limoges (Lambert II coordinates: 365, 5078), on density of conifers. Their water qualities are very the Briance river catchment. They were taken from good or good according to French Water Agency the same geological platform (gneiss) and area but criteria. planted with different species: Chestnut (Castanea Two points on the Vienne river, Royère and sativa) (over 100 years old), young Douglas fir Peyrelevade (higher up than Royère and about (Pseudotsuga menzesii) (about 15 years old) and old Douglas fir (100 years). The A horizons were 85 km away), were chosen in order to examine the 1 effects of the changes of the physico-chemical para- chosen because they might contaminate the subsur- meters of the river on the chemistry of aluminium in face water and to a lesser extent the run-off water water. (in so far as the soil litter is shallow) which supplies water to the stream.