Estimation of global river transport of sediments and associated particulate C, N, and P

Abstract

[1] This paper presents a multiple linear regression model developed for describing global river export of sediments (suspended solids, TSS) to coastal seas, and approaches for estimating organic carbon, nitrogen, and phosphorous transported as particulate matter (POC, PN, and PP) associated with sediments. The model, with river-basin spatial scale and a 1-year temporal scale, is based on five factors with a significant influence on TSS yields (the extent of marginal grassland and wetland rice, Fournier precipitation, Fournier slope, and lithology), and accounts for sediment trapping in reservoirs. The model generates predictions within a factor of 4 for 80% of the 124 rivers in the data set. It is a robust model which was cross-validated by using training and validation sets of data, and validated against independent data. In addition, Monte Carlo simulations were used to deal with uncertainties in the model coefficients for the five model factors. The global river export of TSS calculated thus is 19 Pg yr À1 with a 95% confidence interval of 11-27 Pg yr À1 when accounting for sediment trapping in regulated rivers. Associated POC, PN, and PP export is 197 Tg yr À1 (as C), 30 Tg yr À1 (N), and 9 Tg yr À1 (P), respectively. The global sediment trapping included in these estimates is 13%. Most particulate nutrients are transported by rivers to the Pacific ($37% of global particulate nutrient export), Atlantic (28-29%), and Indian ($20%) oceans, and the major source regions are Asia ($50% of global particulate nutrient export), South America ($20%), and Africa (12%).

Anthropogenic perturbation of the carbon fluxes from land to ocean

“…Thus our estimate is close to values based on compilation of field data 47,58 and the results of the Global Nutrient Export from Watersheds model of carbon and water flows 59 , although higher values have also been suggested 8 . A flux of particulate and dissolved organic C, each equivalent to about 0.2 Pg C yr -1 , and a flux of dissolved inorganic C of about 0.4 Pg C yr -1 is the conventional partitioning among the different C pools 47,58,60,61 .…”

Air–sea exchanges of CO<sub>2</sub> in the world's coastal seas

“…Coastal waters receive large inputs of terrestrial material, such as suspended sediments and nutrients in solution or in particulate matter, in organic or inorganic forms and through river and groundwater discharge, as well as by exchange with the atmosphere, the sediments and the open ocean. They therefore tend to show greater temporal and spatial variability than open oceans, and are more affected by human activities (Cameron and Pritchard, 1963;Alongi, 1998;Chen and Tsunogai, 1998;Rabouille et al, 2001;Chen, 2002Chen, , 2003Chen, , 2004Slomp and Van Cappellen, 2004;Beusen et al, 2005;Chavez et al, 2007;Doney et al, 2007;Radach and Patsch, 2007;Peng et al, 2008;Seitzinger et al, 2010;Dürr et al, 2011;Jiang et al, 2013). However, unlike the open oceans, in which millions of observations have been made and the air-sea exchanges of CO 2 have been valued using various developed models (such as by Khatiwala et al, 2013;Schuster et al, 2013;Wanninkhof et al, 2013), coastal waters have been relatively poorly examined.…”

Past and future trends in nutrient export by 19 rivers to the coastal waters of Indonesia

“…The Global NEWS model was developed to analyze nutrient export by rivers as a function of human activities on land, hydrology, and river basin characteristics Mayorga et al 2010). It includes dissolved inorganic N (DIN; Dumont et al 2005); dissolved inorganic P (DIP; Harrison et al 2005a); dissolved organic forms of N, P, and C (DON, DOP, and DOC; Harrison et al 2005b); and particulate N, P, and C (PN, PP, and POC; Beusen et al 2005). Future scenarios up to the year 2050 were implemented in Global NEWS based on the Millennium Ecosystem Assessment (MEA) scenarios (Alcamo et al 2005;Carpenter et al 2005).…”