J. Machín

Spatial distribution of heavy metals and arsenic in soils of Aragón (northeast Spain): controlling factors and environmental implications

Abstract Legal regulation of heavy metal contents is an important issue in many European countries, where laws still do not exist establishing the heavy metal levels permitted in soils. As a first step to determine the reference levels of heavy metals, it is necessary to know their contents in soils under natural conditions. To achieve this goal in the Autonomous Community of Aragon, a total of 133 sites have been sampled. A balanced allotment of the sampling sites, according to soil spatial distribution in the region, has been carried out by selecting 9 soil types that represent 97.5% of its surface area. Fifteen elements (Cr, Cu, Ba, As, Sb, Hg, Sn, Mn, Fe, Al, Zn, Ni, Co, Cd and Pb) have been analysed by (ICP–AES) after a partial acid extraction. The content of analysed elements has been correlated to some soil parameters such as organic matter, pH, and granulometric fractions. Results of the statistical analyses have shown a large variety and complexity in some of these relationships. The main factors for variation in the heavy metal contents are both the soil type and the lithology. Gypsisols and Calcisols developed on sedimentary rocks have the lowest contents while Leptosols overlying metamorphic and igneous rocks have the highest contents. The spatial distribution of heavy metal contents shows a large variability with the highest contents in the mountain ranges (Iberian and Pyrenees) and the lowest in the plains of the central Ebro valley.

Sediment sources and siltation in mountain reservoirs : a case study from the Central Spanish Pyrenees

Abstract Based on a 137 Cs -derived chronology, we reconstruct the depositional history of the Barasona reservoir in the Esera–Isabena Basin, Central Pyrenees (Spain). Most of the sediments were delivered to the Barasona reservoir during flood events. Comparative mineralogical studies of the Esera and Isabena river channels and the Barasona reservoir sediments help to identify sediment sources and areas of high sediment yield risk, and to establish erosion and sediment transport processes in the watershed. Changes in the mineralogical composition of the sediments can be used to discriminate the relative contribution of the Esera and Isabena rivers during flood periods. Three main periods in the siltation history of the Barasona reservoir were distinguished: (1) From dam construction (1932) to the early 1950s, the reservoir was flushed every year using the lower gates, and average sediment accumulation was very low (1.5 cm/yr). (2) During the 1950s and 1960s, the sedimentation rate increased and reached the highest values: 15 cm/yr, 24.6 cm/yr and 18.2 cm/yr in the Esera river mouth, the northern and the southern areas of the reservoir, respectively. Both changes in the exploitation regime (no annual flushes) and climate variability (increased flood frequency and river inflow) caused this increase in sediment delivery and accumulation. (3) The third period was initiated by the enlargement of the dam in 1972. The new sedimentary dynamics in the reservoir caused a general decrease in the sedimentation rate (11.6 cm/yr in the southern areas; 10 cm/yr in the Esera mouth) that was especially noticeable in the northern areas, where the accumulation rate was reduced to 3.7 cm/yr. An increase in channel erosion processes during this period contributed to the transport of sediments to the inner areas of the reservoir.

Lateglacial and Late Holocene environmental and vegetational change in Salada Mediana, central Ebro Basin, Spain

The Salada Mediana lacustrine sequence, central Ebro Basin, Spain (41330@10AN, 0344@W, 350 m a.s.l.) provides an example of the potential and limitations of saline lake records as palaeoclimate proxies in the semi-arid Mediterranean region. Sedimentary facies analyses, chemical stratigraphy, stable isotopes (d18O and d13C) of authigenic carbonates, d13C values of bulk organic matter and pollen analyses from sediment cores provide paleohydrological and vegetation change reconstructions for the Lateglacial and Late Holocene in the central Ebro basin. A preliminary chronology is based on 210Pb and 14C AMS dates. The lacustrine sequence is composed of three sedimentary Sections. The Lower Section was deposited in a permanent saline to brackish lake. This stage represents the most humid period in the record and it was accompanied by the expansion of temperate trees (particularly Corylus). The Middle Section was deposited in an ephemeral playa-lake complex. Frequent subaerial exposure conditions favour the colonisation of the playa lake #oor by Chenopodiaceae during a low water table period. This interval re#ects the most arid conditions in the Salada Mediana record, including the current environment. A secondary temperate tree expansion occurred after the maximum aridity period. Aquatic plants and cyanobacterial mats spread in the lake during periods of raised water tables.This paleohydrological and vegetational evolution attests to large changes in e!ective moisture during the Lateglacial in the semi-arid northeastern Spain. The abundance of Corylus during the Lateglacial indicates that refugia for temperate trees were located along the Ebro valley during the Last Glacial Maximum. The Holocene sediments in the Salada Mediana records have been eroded, and the Upper Section represents deposition during the last few centuries. ( 2000 Elsevier Science Ltd and INQUA. All rights reserved.

Use of biosolids to restore the natural vegetation cover on degraded soils in the badlands of Zaragoza (NE Spain)

Abstract In the semiarid central Ebro valley, the soils of the badlands surrounding Zaragoza city exhibit severe degradation features. Nevertheless, poor land management practices and limiting climatic and edaphic factors make the natural regeneration of the soil difficult. The use of sewage sludge as amendment for land rehabilitation is increasingly being considered as a technical solution to reverse this environmental degradation and to restore the original vegetation cover. This paper describes the changes produced on the natural vegetation cover after application of digested sewage sludge (biosolids) to three soil types. Experiments were conducted on plots with two different slope levels by applying different rates of biosolids. When increasing rates of biosolids were applied, the biomass yield increased proportionally, although differences among the different soil types and the level of the slope were observed. To avoid undesirable side-effects, mainly referred to soil pollution (salinity and toxic levels of metals), each case has to be individually studied. Therefore, prior to application both characterisation of biosolids and determination of the most suitable application rates to be used are required.

Prognosis and correction of iron chlorosis in peach trees: Influence on fruit quality

Abstract A floral analysis for iron (Fe) content allowed for the prognosis of the incidence of the Fe chlorosis on peach (Prunus persica L. Batsch) trees (c.v. ‘Babygold 7’ grafted on seedlings) with high reliability. From a total of 35 peach trees analyzed, six of them had floral Fe dry matter concentrations less than 133 ppm and these six trees later developed severe Fe chlorosis in their leaves. The early detection and correction of Fe deficiency permitted us to measure the influence of Fe chlorosis on fruit quality as Fe correction resulted in a doubling of frait size and avoidance of the delay of frait ripeness that occurred on the Fe‐deficient trees.

Responses of a saline lake ecosystem in a semiarid region to irrigation and climate variability- The history of Salada Chiprana, central Ebro basin, Spain

Abstract To adequately manage the fragile and changing environments of semiarid regions it is essential to disentangle human from climate or other environmental impacts over longer timescales than human memory. We investigated sediment cores from Salada Chiprana, a saline lake in the central Ebro basin in Spain, using pollen, charcoal, sedimentological, geochemical and radiometric dating techniques. The sequence indicates a rapid evolution from an ephemeral playa lake during the Late Holocene to a permanent saline lake a few centuries ago. The limnological evolution correlates with changes in agricultural practices and provides evidence of the strong impact of irrigation on the lakes hydrological balance from the XVth century. The work demonstrates that the Salada Chiprana, the only permanent, relatively deep, hypersaline lake in Spain has been created by a long history of human interaction with the landscape.

Spatial analysis of gypsiferous soils in the Zaragoza province (Spain), using GIS as an aid to conservation

Within the Ebro valley, the Zaragoza province contains the largest area of gypsiferous soils in Spain. Previous mapping of the gypsum outcrops has been the starting point for this study of the soils developed on them. In this paper, gypsiferous soils are differentiated according to geological age, lithological facies and other depositional features. The most abundant gypsiferous soils correspond to Tertiary outcrops, where a typical catena includes Leptosols on the crest of the hillslopes, Regosols on the talus and Gypsisols on the valley bottom. Gypsiferous soils, developed on the Triassic Keuper facies and Quaternary materials, occupy a relatively small area. The gypsiferous soils have been mapped at a scale of 1:200 000. A CAD software package has been used for digitizing the soil units. A digital elevation model of the Zaragoza province has been created from the digitized topography. The geographical information system, IDRISI, has been used to integrate all the spatial information generated and to produce maps of the soil types classified according to slope and precipitation. In the Zaragoza province, the gypsiferous soils (Lithic and Eutric Leptosols, Petric, Calcic and Haplic Gypsisols, Gypsic Regosols, Gypsic Solonchaks) occupy a total area of 229 619 ha (13% of the area of the province). 25% of the gypsiferous soils occur within the semiarid area (annual rainfall<400 mm) indicating that climate is the main limiting factor for soil conservation, because of the fragility of gypsiferous soils, special care must be taken with land use operations on the 18 137 ha with slopes above 10°. The knowledge of the distribution of gypsiferous soils in relation to topographic and climatic factors provides an important basis for soil conservation and management.

Soil properties and physiographic factors controlling the natural vegetation re-growth in a disturbed catchment of the Central Spanish Pyrenees

Large changes in land use have occurred in the Central Spanish Pyrenees during the twentieth century. This mountain area supported an intense human use since the Middle Ages, that greatly transformed the natural landscape. The land uses changed dramatically during the first half of the twentieth century, due to major socioeconomic forces which lead to depopulation and land abandonment. Since then, a process of natural vegetation recovery has taken place. The anthropogenic impact during centuries deteriorated the soil quality, threatening the sustainability of agroecosystems and the natural vegetation re-growth. In this study, a soil survey was performed to identify the soil types and the physico-chemical properties of the soil that are relevant for maintaining the soil function for the recovery of vegetation after land abandonment. The study was conducted in the Arnás River catchment, which is representative of the region. The highest cation exchange capacity (CEC), nutrients, water retention, water availability and infiltration rates, as well as the lowest pH and carbonates, occurred in Lithic Hapludolls and Calcic Haploxerolls at the shady aspect, under a forest cover. Lithic Ustochrepts and Lithic Xerorthents on the sunny aspect, which were covered by shrubs, were of lesser quality than were the deeper and better-developed soils on the shady aspect. This is seen as an evidence of different patterns of soil degradation, which conditioned the re-growth of natural vegetation after land abandonment. The results provide insights into the main soil factors that have affected the re-establishment of natural vegetation in recent years. Recommendations are given for designing effective strategies for soil conservation after land abandonment in similar mountain environments.

Prognosis of iron chlorosis in apple trees by floral analysis

Abstract In populations of apple trees (Malus pumila Mill) affected by iron (Fe) chlorosis, the floral analyses permit to establish relationships between the Fe concentration in flowers and the chlorophyll content in leaves at 60 and 120 days after full bloom. The relationships between both parameters were highly significant with correlation coefficients of 0.603*** and 0.872***, respectively. As from previous research with peach trees, these high correlations permitted us to predict at a very early stage, the appearance of the Fe deficiency and its intensity. In our experimental conditions, the first visual symptoms of the Fe chlorosis appear in apple leaves with floral Fe concentrations below 310 ppm in dry matter.

Reconstructing the history of sediment accumulation in the Yesa reservoir: an approach for management of mountain reservoirs

Abstract Navas, A., B. Valero-Garcés, L. Gaspar and J. Machín. 2008. Reconstructing the history of sediment accumulation in the Yesa reservoir: an approach for management of mountain reservoirs. Lake Reserv. Manage. 25:15–27. The Aragón River was impounded at the foothills of the Pyrenean Internal Depression in 1959; since then sediments accumulations have decreased the reservoir storage capacity. In this work, we interpreted the history of the sediment accumulation in the Yesa reservoir based on the detailed study of two sediment cores collected at the more stable area in the reservoir. The identification of main sedimentological facies together with the analysis of the grain size distribution of the materials accumulated at the bottom of the reservoir was used for interpretations of the sedimentary dynamics. These data were compared with records of known flood events to derive a tentative chronology of the infilling process by assigning main changes observed in the facies types and sediment components to specific years. In addition to grain size data of sediments accumulated in the river channels, suspended sediments from representative sites of the Aragón Basin to the Yesa reservoir were collected during high and low waters and analysed. Grain size data and sediment composition (organic matter, carbonates) were used to assess the characteristics and the pattern of the sediment transport through the Aragón River network and the role played by lithology and land use. The results provide information on the sediment transport. This approach can be used to assess the siltation processes in Mediterranean mountain reservoirs to improve the management of water bodies by preventing their infilling.