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Human activities have considerably increased the availability of reactive nitrogen. Now, many streams carry large nitrate loads to inland and coastal waters. Nevertheless, mass balance studies have shown that a significant portion of the terrestrial N load does not reach coastal systems, suggesting the existence of important N removal processes. Denitrification has been suggested as an important sink of N in inland waters, which is true in temperate regions of the Northern Hemisphere where most streams contain high nitrate concentrations. However, the global distribution of reactive nitrogen is far from uniform. Recent studies have shown that nitrogen loss from pristine watersheds occurs mainly via dissolved organic compounds, and that the amount of inorganic nitrogen is only a fraction of the total dissolved nitrogen. Herein we present chemistry data from streams within the upper Rio Chagres watershed, a pristine, densely forested watershed in the humid tropics of central Panama. Contrary to that observed in temperate watersheds of the Northern Hemisphere, DIN concentrations in the Rio Chagres and tributaries were low (mostly 10 uM.

In order to demonstrate the possibility of identifying the material within the objects on the sea floor we have performed tests with the 14 MeV sealed tube neutron generator incorporated inside a small submarine, SURVEYOR, submerged in the test basin filled with sea water. The materials inside the investigated objects were identified by measuring the gamma ray spectra and by using the window on the measured alpha- gamma time spectrum. In addition, we describe our field test facility and measurements done at this location in the framework of the EU FP7 project UNCOSS. The existence of a data base of potentially explosive devices on the floor of coastal sea, especially ports and waterways, is of paramount importance. However, the sea floor is littered by number of different objects and the water is not very transparent on such locations. This makes the identification of objects extremely difficult even on known locations. We discuss how to position the SURVEYOR when the object investigated for the presence of explosive has been identified by other sensors (camera, sonar, magnetometer, etc.).