(Table 19, page 199) Minor constituents of one of the San Clemente iron concretions and its metallic core

The chemical and mineralogical composition of pelagic sediments from the East Pacific Ocean has been determined with the aim of defining the ultimate sources and the mechanisms of formation of the solid phases. The distribution of elements between sea-water, the pore solution and the various solid components of the sediments permits interpretations of the variations in time and space of the gross chemical composition of pelagic clays. For example, manganese, present in sea-water in a divalent form, is apparently oxidized at the sediment-water interface to tetravalent species which subsequently become a part of the group of ferromanganese oxide minerals which are found in the marine environment. It is suggested the rate of manganese accumulation in sediments is some function of the length of time the sediment surface is in contact with sea-water. The contribution of chemical species from the different geospheres is considered. The quantitative importance of pelagic clays in the major sedimentary cycle is studied on the basis of the distribution of the weathered igneous rock products between continental and pelagic deposits and sea-water. These analyses of a wide variety of pelagic clays allow a reformulation of the geochemical balance and it is concluded that pelagic clays account for approximately 13 per cent of the total mass of sediments produced over geologic time.

Half-degree gridded nitrogen and phosphorus fertilizer use for global agriculture production during 1900-2013

In addition to enhance agricultural productivity, synthetic nitrogen (N) and phosphorous (P) fertilizer application in croplands dramatically altered global nutrient budget, water quality, greenhouse gas balance, and their feedbacks to the climate system. However, due to the lack of geospatial fertilizer input data, current Earth system/land surface modeling studies have to ignore or use over-simplified data (e.g., static, spatially uniform fertilizer use) to characterize agricultural N and P input over decadal or century-long period. We therefore develop a global time-series gridded data of annual synthetic N and P fertilizer use rate in croplands, matched with HYDE 3,2 historical land use maps, at a resolution of 0.5º latitude by longitude during 1900-2013. Our data indicate N and P fertilizer use rates increased by approximately 8 times and 3 times, respectively, since the year 1961, when IFA (International Fertilizer Industry Association) and FAO (Food and Agricultural Organization) survey of country-level fertilizer input were available. Considering cropland expansion, increase of total fertilizer consumption amount is even larger. Hotspots of agricultural N fertilizer use shifted from the U.S. and Western Europe in the 1960s to East Asia in the early 21st century. P fertilizer input show the similar pattern with additional hotspot in Brazil. We find a global increase of fertilizer N/P ratio by 0.8 g N/g P per decade (p< 0.05) during 1961-2013, which may have important global implication of human impacts on agroecosystem functions in the long run. Our data can serve as one of critical input drivers for regional and global assessment on agricultural productivity, crop yield, agriculture-derived greenhouse gas balance, global nutrient budget, land-to-aquatic nutrient loss, and ecosystem feedback to the climate system.