Contribution of technic materials to the mobile fraction of metals in urban soils in Marrakech (Morocco)   总被引：5，自引：2，他引：3  

Hicham El Khalil  Christophe Schwartz  Ouafae Elhamiani  Jochen Kubiniok  Jean Louis Morel  Ali Boularbah 《Journal of Soils and Sediments》2008,8(1):17-22

Background, Aim and Scope  In urban areas, soils are often dramatically altered by anthropogenic activity and these modifications distinguish these soils (Anthrosols, Technosols) from those in natural systems. In urban environments, they receive considerable pollution from industry, traffic and refuse. Since contaminated soil particles can be easily inhaled or ingested, there is a potential transfer of toxic pollutants to humans. Risk assessment is essentially based on the determination of the total or mobile contents of pollutants in soils using chemical extractions. This approach could be improved by taking into consideration the bioavailable fractions of these toxic elements as measured by biotests. The coarse soil fraction usually neglected in analyses can nevertheless have an effect on the concentration of metals in the soil solution. This coarse fraction is made up of the natural materials and of technic materials constituting anthropogenic soils (plastic, paper, fabric, wood, bones, metallic elements and building materials). These materials have variable capacities to release or adsorb trace elements. Samples representative of different technic fraction components of Marrakech urban soils permit one to quantify their contribution to the enrichment of the soluble metal concentrations. Works are carried out to achieve partial extractions of metals from the three fractions (less than 2 mm, coarse natural and coarse technic) of selected urban soils in order to determine their contribution to the metal contamination of soils. Materials and Methods  Selected soils were collected from 9 sites according to a gradient of increasing anthropogenic influence from suburban to urban zones. Soils were air-dried, homogenized, and sieved (2 mm). The coarse fraction was sorted to separate the different technic materials and natural materials. Water extractions were run, on the natural, coarse fraction, on the complete technic fraction of the 9 soils and on average samples made of technic materials sorted out of 58 topsoils sampled from different sites in the city of Marrakech. Results  Results show that the percentage of the technic fraction increases while approaching the historic city center. It represented about 14% in the most anthropogenically disturbed soils. Along this gradient, soils changed progressively from Anthrosols to Technosols according to the WRB classification of urban and industrial soils. Analyses of metal contents showed that the fine fraction (<2 mm) mainly contributed to the metallic contamination of the water soluble fraction. The natural coarse fraction had the highest contribution to the copper release and was responsible for the release of all water-extractable copper in some soils. Concerning the technic fraction, it has a significant contribution essentially in the most anthropogenically disturbed soils as characterized by an elevated percentage of anthropogenic elements. The water extractable metal contents of average samples of these anthropogenic elements shows that elevated metal concentrations were released by bones, wood, plastic and fabric/paper. Discussion  This study concerns soils in urban areas, which are strongly impacted by human activities. Part of the soils can be classified as Anthrosols, profoundly impacted through the addition of organic materials from household wastes, irrigation, or cultivation. Other soils strongly impacted by human activities are Technosols dominated or strongly influenced by man-made materials. Technosols appear mostly in urban and industrial areas and are more likely to be contaminated than Anthrosols. The composition and heterogeneity of urban soils lead to modifications of the mobility and availability of pollutants depending on successive land-uses and on the composition of technic materials. The fine fraction offers a high transferring surface capacity, leading to a high mobilization of metals. The technic fraction contributes significantly to the metal release in the Technosols. This property can be explained by a reversible adsorption of metals on the organic matter. Conclusions  Results confirm that anthropogenic activity causes a wide spatial diversity of soil quality in the urban and suburban area. It introduces large amounts of technic materials in soils that could have an impact on the metal availability. It therefore acts on the metal bioavailability in the urban Technosols. Recommendations and Perspectives  These results show that it is necessary, in addition to the characterization of the fine particles, to take into account the contribution of the coarse fraction of the Technosols in the evaluation of risks of transfer of metals to the food chain.  相似文献   

Aluminium chemistry in two contrasted acid forest soils and headwater streams impacted by acid deposition,Vosges mountains,N.E. France   总被引：1，自引：0，他引：1  

Maitat  Ouafae  Boudot  Jean-Pierre  Merlet  Denis  Rouiller  James 《Water, air, and soil pollution》2000,117(1-4):217-243

Al chemistry was studied in two acidic watersheds, one with a podzol, the other with an acid brown soil, in the Vosges mountains (N.E. France), by analysing both leaching and centrifugation soil solutions and spring waters over 3 yr. In the podzol, Al was mobilized in the eluvial horizons under the predominant influence of organic acidity, then leached down the profile as organic and F-bound Al. Strong undersaturation with respect to proto-imogolite and imogolite showed that the proto-imogolite theory of podzolization could not apply. Al was transferred from the soil to spring water mostly as Al³⁺ and Al-F. Al³⁺, as well as additional minor species (AlOH²⁺, AlSO₄ ⁺), originated from the redissolution of the top of the spodic horizons under the influence of both soil solution acidity and the occurrence of mobile anions derived from atmospheric deposition. Conversely, in the acid brown soil, Al mobilization was regulated by nitrate and occurred mainly as Al³⁺. Most of Al was retained in the deep soil and only traces of monomeric Al reached spring water. In the podzol eluvial horizons, soil solutions were undersaturated with respect to all relevant mineral phases and their chemical composition agree with the concept of a mobilization of Al from the solid soil organic Al and a control of Al³⁺ activity by complexation reaction with the solid and soluble soil organic matter and F. In the acid brown soil, soil solutions were found to be in equilibrium with natural alunite, and the formation of this mineral, if confirmed, would account for the occurrence of 'open' vermiculites instead of the expected hydroxy-Al interlayered vermiculites. Al solubility control in surface water of both watersheds remains unclear. The Al-F species in both watersheds and the likely control of Al solubility by alunite in the acid brown soil emphasize the influence of acid deposition on Al chemistry in acid watersheds.  相似文献   

Sources of resistance to Mayetiola Destructor in breadwheat and durum wheat in Morocco     

Lynn W. Gallagher  Abderrahim Benyassine  Ouafae Benlhabib  Mohamed Obanni 《Euphytica》1987,36(2):591-602

Summary Grain yield reductions of both breadwheat (Triticum aestivum L.) and durum wheat (Triticum turgidum L. var. durum) caused by attacks of Hessian fly (Mayetiola destructor Say) are second perhaps only to those caused by inadequate soil moisture in Morocco. To identify effective sources of resistance, 817 entries of common wheat and durum wheat reported to be resistant to Hessian fly were evaluated under natural infestations in Morocco. A large number of genes conferring virulence are present in populations of Moroccan Mayetiola. The genes H₁, H₂, H₃, h₄, H₆, H₇, H₈, H₉, H₁₀, H₁₁, H₁₄, H₁₅, and H₁₆ as well as the Marquillo, Kawvale and PI 94587 resistance sources are not useful for cereal improvement in North Africa. Luso, which has the gene H₁₂, also appeared susceptible in limited testing. Genotypes having the genes H₅ and H₁₃ were identified as significantly reducing larval survial in natural populations of Mayetiola. Of 11 resistant breadwheats identified with unknown genes, seven were from Portugal and three were from the Soviet Union. Although none of the durums tested had high levels of reistance, the two most promising durums were from Portugal. It is proposed that initially H₅ be deployed in durum wheats and H₁₃ be used in common wheat improvement. Leaf pubescence appears of little use in reducing the larval survival of Mayetiola.  相似文献   

Distribution of major elements and trace metals as indicators of technosolisation of urban and suburban soils   总被引：2，自引：2，他引：0  

Hicham El Khalil  Christophe Schwartz  Ouafae El Hamiani  Jochen Kubiniok  Jean Louis Morel  Ali Boularbah 《Journal of Soils and Sediments》2013,13(3):519-530

Purpose

Can geochemical characteristics indicate the human impact on soil formation (technosolisation) for urban and suburban soils? This question is assessed for the city of Marrakech located in one of the main agricultural areas of Morocco and characterized by a very rapid rate of expansion. The aim of this work is to assess geochemical properties of surface horizons of urban and suburban soils and to compare them with land use types.

Materials and methods

Fifty-eight surface soil samples were collected in different sectors of the city with different land use histories. As land use can be defined as the human use of land, these sampling sites were selected according to the current human activity (e.g., residential districts, agriculture, market-gardening, traditional, or industrial activities) and according to the superposition of the land use over time. All samples were air-dried, disaggregated, homogenized, and then sieved through a 2-mm mesh. Major elements and trace metals were measured in the soil using X-ray fluorescence spectroscopy. For technical limits, Cd was measured using atomic adsorption spectrometry.

Results and discussion

Urban and suburban soils of Marrakech present generally similar geochemical compositions for many elements. Siliceous (SiO₂) compounds related to the parent material are dominant in these soils. However, the significant concentrations of P₂O₅ and CaO, measured in some of the urban soils studied, can be attributed to anthropogenic inputs of phosphorus (P) and technic materials, mainly building materials composed of cement and gypsum (plaster). Soils collected from agricultural areas irrigated with urban wastewater and soils developed on rubbish dumps are the most contaminated by metals (e.g., Cu, Zn, and Pb). Therefore, the distribution of major and trace elements in soils underlines the considerable impact of urban land uses.

Conclusions

Human activities determine the type of land use, impact the urban environment, and cause a wide spatial diversity of soil quality. The urban and suburban soils of Marrakech contain similar major element distributions except for strongly anthropised soils (soils developed on rubbish dumps and agricultural soils irrigated with urban wastewater). Unlike major elements, trace elements present systematically significantly higher concentrations in urban soils than those measured in control soils. In these conditions, the highest concentrations exceed international clean-up standards and are correlated with land use type. Phosphorus, Ca, and several heavy metals are proposed as indicators of human impacts on soil characteristics in urban and suburban environments.  相似文献   

Effects of Deficit Irrigation and Fertilization on Quinoa (Chenopodium quinoa Willd.) Water Status and Yield Productions     

Fghire  Rachid  Anaya  Fatima  Issa Ali  Oudou  Lamnai  Kamal  Foughali  Boubaker  Faghire  Mustapha  Benlhabib  Ouafae  Wahbi  Said 《Gesunde Pflanzen》2022,74(1):97-110

Worldwide population is in permanent growth, leading to an over-presser on the food resources. This demand leads to an over-exploitation of land and water resources. Recently, the quinoa plant has attracted attention as alternative crop with high nutritive value and high tolerance to the marginal conditions. In this study, a field experiment was conducted during two successive seasons to investigate the effect of deficit irrigation on the agronomic performance. Four treatments of deficit irrigation (100%, 50%, 33% ETc and rainfed) were applied to one variety in the first season and to four genotypes (two varieties and two lines). The results were evaluated by measuring biomass and seed quinoa yield, water-use efficiency, harvest index, seed size and 1000 seeds weight. Results show that the implementation of deficit irrigation is an appropriate strategy to reduce the use of agricultural water and maintain relatively high yields. On the other hand, the results of the economic quality reflected by the size and weight of seed yield, indicates that quinoa can be considered a well-adapted to the conditions of water scarcity culture. According to agronomic parameters, L143 line followed by the line L11 showed a high potential of adaptation under the different treatments of stress, while the “Puno” variety presented the best performance under the favorable conditions of irrigation (100% ETc).

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