Throughout the developing world, river sand and gravel is widely exploited as aggregate for construction. Sediment is often mined directly from the river channel and makes an important contribution to the national demand for aggregates. However, instream mining, if not carefully controlled, can cause significant damage to the river and its associated biota, and to the adjacent land, as well as creating conflict with other users of the river. The economic and environmental geology of river sand and gravel mining in developing countries is poorly known and there is little knowledge available to inform existing regulatory strategies. Research work on selected river systems in Jamaica and Costa Rica has generated a considerable amount of new information on resources and sediment budgets, on market and supply options, on the physical, biological and social impacts of extraction, and on best-practice legislative and mineral planning issues. A methodology has been developed for effective control of instream sand and gravel mining operations including a Code of Practice, which regulators can use for examining and reconciling the conflicting claims of sand and gravel extraction and the environment.
On a mesuré le rayonnement solaire global et le bilan du rayonnement pour des surfaces très variées à Poste-de-la-Baleine, au Québec, du 30 mai au 1er juin 1970, pendant des périodes cycloniques et anticycloniques alternantes. À l'exception d'une surface d'eau libre dans le sud-est de la Baie de James et près des îles Belcher, la glace recouvrait la Baie d'Hudson. Les flux provenant de l'ouest et du sud-ouest s'accompagnaient de temps frais, humide et nuageux. On a trouvé une bonne corrélation linéaire entre le bilan du rayonnement et le rayonnement global, pour toutes les surfaces et pour les temps nuageux, depuis le brouillard jusqu'aux cirrus. Les résultats indiquent que, malgré la réduction du rayonnement solaire par les nuages, environ 72% de l'énergie était disponible en surface pour les processus biologiques et physiques. Il faut noter l'importance du flux de chaleur sensible et l'advection de l'air froid provenant de la Baie.Total insolation and net radiation were measured for a wide variety of surfaces at Poste-de-la-Baleine, Québec, from May 30 to June 1, 1970, during alternating cyclonic and anticyclonic situations. With the exception of open water in southeastem James Bay and in the vicinity of the Belcher Islands, the ice cover was complete over Hudson Bayand westerly and southwesterly flow were associated with cool, wet, cloudy weather. For cloudy conditions, including fog and cirrus, and damp surfaces, a close linear relationship was found to exist between net radiation and total insolation for all surfaces. The results indicated that although the insolation was much reduced by cloud cover, about 72% of the energy was available at the surface for physical and biological processes. The importance of the sensible heat flux is noted, and of the cold advection from the Bay
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.