Amount and type of derelict gear from the declining black pearl oyster aquaculture in Ahe atoll lagoon,French Polynesia     

Serge Andréfouët  Yoann Thomas  Cedrik Lo 《Marine pollution bulletin》2014

Pearl oyster aquaculture is a major activity in French Polynesia atoll lagoons. After the economic decline that characterized the last decade, concerns recently rose about discarded installations and materials that supported aquaculture practices and by facilities abandoned after they had to close their activities. In May 2013, a first inventory of the type and amount of pearl farms derelict gear (PFDG) was achieved on 47 sites in Ahe lagoon. Surveys were conducted within and outside the boundaries of aquaculture concessions. Twenty types of PFDG littered the lagoon floor and the water column. The most impacted areas were near abandoned grafting houses with up to nine types of PFDG. Forty-five percent of the sites were impacted, including outside concessions. While management authorities are fully aware of the problem, this first assessment is a wake-up call to stimulate the cleaning of lagoons, enhance awareness among farmers, and identify potential ecological consequences on lagoon ecosystems.  相似文献   

Physically Based Groundwater Vulnerability Assessment Using Sensitivity Analysis Methods     

Jean Beaujean  Jean‐Michel Lemieux  Alain Dassargues  René Therrien  Serge Brouyère 《Ground water》2014,52(6):864-874

A general physically based method is presented to assess the vulnerability of groundwater to external pressures by numerical simulation of groundwater flow. The concept of groundwater vulnerability assessment considered here is based on the calculation of sensitivity coefficients for a user‐defined groundwater state for which we propose several physically based indicators. Two sensitivity analysis methods are presented: the sensitivity equation method and the adjoint operator method. We show how careful selection of a method can significantly minimize the computational effort. An illustration of the general methodology is presented for the Herten aquifer analog (Germany). This application to a simple, yet insightful, case demonstrates the potential use of this general and physically based vulnerability assessment method to complex aquifers.  相似文献   

Local soil failure before general slope failure   总被引：1，自引：0，他引：1  

Gianfranco Urciuoli  Luciano Picarelli  Serge Leroueil 《Geotechnical and Geological Engineering》2007,25(1):103-122

Slopes are generally characterized by non-uniform stress field. Additional stresses induced by changes in boundary conditions can emphasize local differences in the stress level. As a consequence, every failure process is, at first, local, with formation of plastic zones, then general. This is the subject of this paper, which concerns clay slopes, whose failure generally implies formation of a shear zone. A special consideration is addressed to the simple and special case of infinite slope which is also featured by transition from local to general failure, even if stress conditions are uniform along the potential failure plane.  相似文献   

Internal architecture and mobility of tidal sand ridges in the East China Sea     

Zhenxia Liu  Serge Berné  Yoshiki Saito  Hua Yu  Alain Trentesaux  Katsuto Uehara  Ping Yin  J. Paul Liu  Chaoxing Li  Guanghai Hu  Xiangqin Wang 《Continental Shelf Research》2007

On the basis of bathymetric and seismic data and data from piston cores collected by the Chinese–French marine geology and geophysics investigation of 1996, we discuss the internal architecture and mobility of tidal sand ridges in the East China Sea (ECS). We characterized the sand ridges on the middle to outer shelf of the ECS as tide-dominated sand ridges with southwest dipping beds, indicating that the regional net sediment transport is toward the southwest. As the sand ridges gradually migrate toward the southwest, new sand ridges are continually replacing old ones, and several generations of sand ridges have developed in the study area.  相似文献   

Volume contents     

Christian Beck  Pieter Van Rensbergen  Marc De Batist  Fernand Berthier  Serge Lallier 《Journal of Paleolimnology》2001,25(4):551-553

Volume Contents

Volume contents  相似文献   

Role of suspended sediments on the distribution of PCB in the Seine Estuary (France)     

Alain Abarnou  Jacques Avoine  Jean Paul Dupont  Robert Lafite  Serge Simon 《Continental Shelf Research》1987,7(11-12)

PCB (polychlorinated biphenyls) contamination and its relationship to SPM (suspended particulate material) have been studied in the Seine Estuary, which is heavily polluted by these persistent and hydrophobic man-made chemicals. Two sampling cruises have been performed during different freshwater discharge conditions. PCB and SPM concentrations, as well as grain-size distributions in the particulate material have been determined. Water samples have been collected at fixed positions during a tidal cycle, and along transects within the estuary.PCB concentrations vary from 2 ng 1⁻¹ in the marine zone to 250 ng 1⁻¹ within the estuary, and reach 1.3 × 10³ ng 1⁻¹ in the turbidity maximum zone. During a tidal cycle, low PCB concentrations are observed at high water, and are in the same range in February as in July. High PCB contamination is observed at low water, but PCB concentrations are about five times higher in February. SPM and PCB variations are well correlated in both periods of observations. Higher PCB contamination during February is explained by higher SPM inputs, mainly due to particles of riverine origin. The transport of PCB within the estuary depends on the quantity and the grainsize composition of suspended material, which varies according to freshwater discharge and tidal amplitude.  相似文献   

Institutional dimensions of the developing REDD+ process in Cameroon     

Serge Ngendakumana  Peter A. Minang  Mireille Feudjio  Stijn Speelman  Patrick Van Damme  Zacharie Tchoundjeu 《Climate Policy》2014,14(6):769-787

The reducing emissions from deforestation and forest degradation (REDD+) initiative has emerged in recent years as a mechanism to simultaneously address climate change, biodiversity, and poverty reduction challenges at the margins of tropical forests. Congo Basin countries, including Cameroon, have embraced the opportunities that REDD+ provides, with great expectations. Yet, it needs to be investigated whether the enabling institutional environment, which is required for implementing REDD+, is present. Understanding is still limited on how to build adequate and strong institutional relations that could shape the reforms towards the establishment of efficient emissions reductions schemes. Furthermore, uncertainty remains on the operational mechanisms of REDD+, suggesting that, to catalyse effectiveness, there is a need to come up with a governance model nested in relevant policy frameworks. This study builds on a modified ‘4Is’ framework – Institutions, Interests, Ideas and Information – to analyse REDD+ and explore stakeholders' perceptions on the local forest governance potential. A structural implementation model to optimize the effectiveness of REDD+ is developed. Findings suggest that governments need to review existing policies to take into account participation, local people rights, and information access as a way to stimulate actors' willingness to contribute to emissions reductions and carbon stock increases under REDD+ regimes.  相似文献