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

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(-1) with a 95% confidence interval of 11 - 27 Pg yr(-1) when accounting for sediment trapping in regulated rivers. Associated POC, PN, and PP export is 197 Tg yr (-1) (as C), 30 Tg yr(-1) (N), and 9 Tg yr(-1) ( P), respectively. The global sediment trapping included in these estimates is 13%. Most particulate nutrients are transported by rivers to the Pacific ( similar to 37% of global particulate nutrient export), Atlantic ( 28 - 29%), and Indian ( similar to 20%) oceans, and the major source regions are Asia ( similar to 50% of global particulate nutrient export), South America ( similar to 20%), and Africa (12%).