Determination of predevelopment denudation rates of an agricultural watershed (Cayaguás River, Puerto Rico) using in-situ-produced Be in river-borne quartz

Accurate estimates of watershed denudation absent anthropogenic effects are required to develop strategies for mitigating accelerated physical erosion resulting from human activities, to model global geochemical cycles, and to examine interactions among climate, weathering, and uplift. We present a simple approach to estimate predevelopment denudation rates using in-situ-produced cosmogenic ¹⁰Be in fluvial sediments. Denudation processes in an agricultural watershed (Cayaguás River Basin, Puerto Rico) and a matched undisturbed watershed (Icacos River Basin) were compared using ¹⁰Be concentrations in quartz for various size fractions of bed material. The coarse fractions in both watersheds bear the imprint of long subsurface residence times. Fine material from old shallow soils contributes little, however, to the present-day sediment output of the Cayaguás. This confirms the recent and presumably anthropogenic origin of the modern high denudation rate in the Cayaguás Basin and suggests that pre-agricultural erosional conditions were comparable to those of the present-day Icacos.     

International liability for weather modification

Can a State be held liable to another State or to citizens of another State for damage caused by (a) the State's own weather modification activities; (b) weather modification activities conducted by a nongovernmental party within its borders, or (c) weather modification activities conducted by persons within its control but outside its borders? What measures can be taken by a State to minimize its liability for weather modification activities? This article tries to answer these questions. It focuses on liability under international law, and emphasizes issues related to cloud-seeding to affect precipitation and to hurricane modification.     

Vital and mortal staining of algae in the presence of chlorine-produced oxidants

Evans blue and neutral red were tested as mortal and vital stains respectively for eight estuarine algal species which had been exposed to chlorine-produced oxidants in a continuous-flow system. The effect of CPO on staining with Evans blue was negligible. High concentrations of CPO affected staining with neutral red in several instances; this is probably due to CPO-induced mortality of test organisms during the exposure or staining period. Neutral red leached fromSkeletonema costatum andOlisthodiscus luteus before the end of the staining period. Staining ofDunaliella tertiolecta with neutral red proceeded more slowly. Evens blue, which was incorporated quickly and remained in the cells, is recommended for live-dead determinations for all species examined exceptNitzschia closterium, for which neutral red should be used. Neither stain was effective onMychonastes ruminatus (Simpson and Van Valkenburg 1978).     

Matching classical boundary-layer solutions toward a geostrophic drag coefficient relation

The relationship between geostrophic, Ekman-layer, and surface-layer flow is explored. Formalized limit solutions for each layer are developed; together they form a continuous solution for the semi-infinite flow over a surface. These classical solutions are re-derived and related, to prepare for a two-layer composite boundarylayer solution with patching criteria. The patching process yields a resistance law which indicates a correspondence between the stress and the geostrophic flow deviation involving a similarity relation with two arbitrary parameters.