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Estimates of the sources and wet deposition fluxes of inorganic nutrients (PO3- 4, NO- 3, NO- 2, NH+ 4) have been made using a long-term wet atmospheric deposition measurement at three sites along the Mediterranean coast of Israel. The nutrient composition in rainwater indicated a dominant anthropogenic source for NO- 3 and NH+ 4 and a continental, natural, and anthropogenic, rock/soil source for P03- 4. The calculated longterm dissolved inorganic N (IN) and inorganic P (IP) fluxes were 0.28 and 0.009 g m-2 yr-1 to the coastal zone and estimated as 0.24 and 0.008 g m-2 yr-1 to the Southeast (SE) Mediterranean, with a possible increasing pattern of the annual dissolved IN fluxes. Concentration of total and seawater...
Silica, nitrate, total and dissolved phosphorus, and conductivity were measured during spring and summer in Lake Powell, Utah-Arizona. Phytoplankton productivity was also de- termined. Conductivity is used as a tracer for delineating the advective influence of inflows from the Colorado and San Juan Rivers on nutrient delivery and distribution in the reservoir. High spring runoff (1,000-2,000 m3 s-') enters the lake essentially as an overflow and dom- inates the nutrient cycle in the epilimnion. The interaction of advective nutrient delivery and high turbidity controls the distribution of phytoplankton productivity and nutrient depletion. Published in Limnology and Oceanography, volume 25, issue 2, on pages 219 -...
This study assesses the role of the atmospheric dry fallout as a source of new nitrogen and phosphorus to the surface Levantine seawater. Leaching experiments of inorganic nitrogen () and phosphorus (LIPO4), using SE Mediterranean surface seawater, were performed on 41 aerosol (hereafter dust) samples collected on Whatman 41 filters between April 1996 and January 1999 at Tel Shikmona, Israel and on four desert-event dust powder samples. A geometric mean of 2.8 and 3.2 mmol NO3 - and NH4 + per gram of dust was leached by seawater from normal (background) dry deposition captured by the filters. Significantly lower amounts of IN with lower NH4 +:NO3 - ratios were leached from both the filters and the dust powder sampled...
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Compound-specific nitrogen, carbon, and hydrogen isotope records from sediments of Sky Pond, an alpine lake in Rocky Mountain National Park (Colorado, United States of America), were used to evaluate factors contributing to changes in diatom assemblages and bulk organic nitrogen isotope records identified in lake sediments across Colorado, Wyoming, and southern Montana. Nitrogen isotopic records of purified algal chlorins indicate a substantial shift in nitrogen cycling in the region over the past ~60 yr. Temporal changes in the growth characteristics of algae, captured in carbon isotope records in and around Sky Pond, as well as a -60? excursion in the hydrogen isotope composition of algal-derived palmitic acid,...
The buffering of riverine dissolved silica and phosphate by sorption reactions between the aqueous phase and suspended sediment is examined with the turbid Colorado River system as a model. Concentrations are found to lie in a range predicted from laboratory sorption experiments with natural sediments and waters. Phosphate is probably highly buffered by suspended sediment during river flow while silica is not. Silica appreciably affects phosphate sorption reactions but not vice versa. Increased temperature results in higher silica but lower phosphate concentrations as a result of sorption. The buffering action of suspended sediments is largely complete within a few hours and is approximately proportional to the...


    map background search result map search result map Compound-specific stable isotopes of organic compounds from lake sediments track recent environmental changes in an alpine ecosystem, Rocky Mountain National Park, Colorado Compound-specific stable isotopes of organic compounds from lake sediments track recent environmental changes in an alpine ecosystem, Rocky Mountain National Park, Colorado