No abstract

No abstract

No abstract

No abstract

Many studies have shown that the quality of biodiversity influences the well-being of citizens. Nevertheless, the drivers that shape biodiversity in urbanized zones are poorly understood. Although tree bases present reduced surface areas, they occur in great numbers in a deliberate spatial arrangement and may play an important ecological role in urban environments by offering limited favorable spaces for the development of spontaneous flora. The purpose of this study was to identify the factors that influence the composition of plant communities harbored by tree bases in an urban district. We analyzed floristic inventory data collected in 2014 about plants growing at the bases of the 1474 trees on the 26 streets of the Bercy district in Paris (France). Our results indicated that the plant communities growing in the urban tree bases varied according to different factors. The abundance and distribution of these species were dependent on their biological traits (seed longevity in the soil bank) as well as the tree base characteristics (tree trunk diameter, equipment type around the tree bases, soil compaction, animal excrement, solar radiation, and urban tree species), the street orientation according to the air flow following the Seine River, and the geographic structure of the district (the influence of the presence of green spaces). The results of this study showed that the tree bases could be considered favorable stepping-stone habitats for certain species between more important green spaces such as parks and gardens. Thus, these areas actively participate in the enhancement of urban biodiversity.

No abstract

La rivière «Kadicha»au nord du Liban est soumise à des pressions urbaines, agricoles et industrielles. Enl’absence de station d’épuration, Les eaux usées sont rejetées directement dans le cours de la rivière. Afin d’évaluer la qualité des eaux de surface de la rivière Kadicha, 12 sites d’échantillonnage, ont été sélectionnésau niveau desquels des prélèvementsponctuels des eaux de surfaceont été effectués sur 2 saisons (humide et sèche). Les paramètres physico-chimiques ont étédéterminés: pH, température, conductivité électrique, TDS (solides totaux dissous) et les MES (matières en suspension). Des analyses bactériologiques en coliformes thermotolérants(CTT) et en streptocoques fécaux (SF) ont été effectuéespar les méthodes classiques de filtration sur membrane.Le suivi des paramètres physico-chimiques indique une variation spatiale influencée par les activités anthropiques exercées. En se basant sur le système d’évaluation dela qualité des eaux littorales(SEQ-Eau), il ressort que les eauxdes 2 bras étudiés de la rivière ontune très bonne qualitéchimique. Cependant, les résultats de l’analyse bactériologique indiquentl’existence d’une contamination fécalequi dépasse les normes pour une utilisation d’eau à des fins récréatives et pour l’irrigation avec des risques sanitaires pour la santé humainesurtout au niveau de la plaine côtièrede la rivière. La comparaison des teneurs en microorganismes dela présente étude avec une étude précédente réalisée en 2006 sur la rivière Kadicha, indique une augmentation en ces teneurs. Ceci pourrait être liéà l’augmentation des activités anthropiques et démographiquesdurant la dernière décade.

Total dissolved trace and major metals and their partitioning in porewater sediment have been investigated at two sites in the Seine River estuary (France). For this purpose, solid phase extraction (SPE) has been employed using specific chelating resins for the separation and preconcentration of organic and inorganic forms of studied metals under controlled (N2) inert atmosphere. In fact, the study is focused on the development of a method for sample collection and handling under inert atmosphere in order to avoid some potential artefacts of the extracted porewater, to preserve the samples from possible chemical oxidation changes and to determine metals partitioning between organic and inorganic forms. For this point, a separation and preconcentration method using two columns in series (chelamine and C18 columns) was used. The trace and major metals fixed on the two resins for all determinations were stripped by nitric acid (2 M) and analyzed by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) and Zeeman Graphite Furnace Atomic Absorption Spectroscopy (ZGF-AAS). The relationship between the distribution of metals and physico-chemical parameters such as pH and Eh (redox potential) as a function of depth was discussed. Some tendency in the distributions and seasonal variability of these traces and major metals are improved. The concentrations for all studied metals decreased as a function of depth where iron and manganese were found at mg L(-1) levels and other metals were found at [micro sign]g L(-1) levels, as well as there were significant fractions of all metals (except of manganese) which were complexed by organic matter. The comparison of data for the major elements (Fe and Mn), obtained by direct determination (without preconcentration) and preconcentration, show a very good recovery.