The Main Features of Phosphorus Transport in World Rivers

Data on the geochemistry of phosphorus in the continental runoff of dissolved and solid substances were systematized and generalized, with a separate consideration of the processes of runoff transformation in river mouth areas. It has been established that atmospheric deposition, which many authors consider to be an important source of phosphorus in river runoff and not associated with mobilization processes in catchments, actually contains phosphorus from soil-plant recycling. This is confirmed by the fact that the input of phosphorus from the atmosphere into catchments exceeds its removal via water runoff. An analysis of the mass ratio of phosphorus in the adsorbed form and in the form of its own minerals was carried out. It was shown that the maximum mass of adsorbed phosphorus is limited by the solubility of its most stable minerals. The minimum concentrations of dissolved mineral and total phosphorus were observed in the rivers of the Arctic and subarctic belts; the maximum concentrations were confined to the most densely populated temperate zone and the zone of dry tropics and subtropics. In the waters of the primary hydrographic network, the phosphorus concentration exhibited direct relationships with the population density in the catchments and the mineralization of the river water and was closely correlated with the nitrogen content. This strongly suggests that economic activity is one of the main factors in the formation of river phosphorus runoff. The generalization of the authors’ and the literature’s data on the behavior of phosphorus at the river–sea mixing zone made it possible to draw a conclusion about the nonconservative distribution of phosphorus, in most cases associated with biological production and destruction processes. The conservative behavior of phosphorus was observed only in heavily polluted river mouths with abnormally high concentrations of this element.

Sources and cycling of dissolved black carbon (DBC) in rivers and ocean revealed by carbon isotopes

<p><strong>Abstract</strong></p><p>Dissolve black carbon (DBC) has been recently recognized as an important fraction of dissolved organic carbon (DOC) in both rivers and ocean. It is estimated that about 10% of the riverine DOC transported by the world rivers could be DBC. The sources and fate of DBC in both rivers and ocean, however, is not well known. In this study, we present radiocarbon (<sup>14</sup>C) and stable carbon isotope (<sup>13</sup>C) measurements of DBC in several large rivers in China, and in coastal and open ocean waters. DBC was concentrated using solid phase extraction (SPE) method and quantified by chemothermal oxidation (CTO) method.</p><p>Concentrations of DBC varied in rivers depending on the drainage basin of the river and accounted for 3.7-7.6% of the riverine DOC pool. DBC was slightly lower, accounted for 2.9-5.9% of DOC in coastal and open oceans. Carbon isotope results indicate that DBC δ<sup>13</sup>C values were all slightly enriched (by 2-3‰) than the values of DOC in both rivers and ocean. The DBC Δ<sup>14</sup>C values varied largely in rivers and the values were significantly higher than DOC Δ<sup>14</sup>C values in rivers but similar to DOC Δ<sup>14</sup>C values in the ocean. Using a two-end member isotope mass balance model, we calculated that the most DBC (80%) with relatively young <sup>14</sup>C ages in the rivers was derived from biomass burning. Laboratory incubation studies also found that DBC released from recent charcoal was able to be utilized by bacteria, supporting the speculation that river transported DOC could be decomposed during estuaries mixing. Our study suggests that DBC is cycled in the same time scales with the DOC pool in the ocean and no extremely older DBC was identified as reported in other studies previously.</p>

REE–Th systematics of the suspended particulate matter and bottom sediments from the mouth zones of the world rivers of different categories/classes and some large Russian Arctic rivers

The distribution of the rare-earth elements (REE) and Th in the suspended particulate matter (SPM) of some large Russian Arctic rivers and in the bottom sediments from the mouth zones of the world rivers of large categories/classes is compared. It is concluded that the fine (pelite and silt-pelite) material of the Russian Arctic rivers belongs mainly to classes 1 + 2 (large rivers and rivers draining areas made up mainly of sedimentary rocks) and 4 (SPM of rivers draining volcanic areas) of the world rivers. The SPM similar in terms of REE and Th distribution to the bottom sediments of the mouth zones of category/class 3 (rivers draining mainly metamorphic/magmatic terranes) are not typical of the Russian Arctic rivers, except for the SPM of the Lena River similar in terms of (La/Yb)N and Eu/Eu* ratio.

Mass balances of major solutes, nutrients and particulate matter as water moves through the floodplains of the Pantanal (Paraguay River, Brazil)

ABSTRACT In the upper Paraguay River basin, which includes the Pantanal, one of the largest wetlands in the world, rivers connection the surrounding upland plateaus with lowland floodplains. Agriculture, erosion, urban effluent, and hydropower in the uplands can alter the transport of materials by rivers to the Pantanal. Information about material transport, particularly nutrients, is still insufficient to evaluate changes. In this study we estimated rates of dissolved and suspended material transport from the upland watersheds into the Pantanal, and through the Paraguay River, and calculated mass balances of these flows to reveal net losses and gains inside the Pantanal. We sampled fifteen tributaries and the Paraguay River for seven years. The annual water balance in the basin was almost complete, with a deficit of only 11%. Predicted:Observed ratios close to one indicated a near balance between inputs and outputs for dissolved solutes and nutrients, however sedimentation losses of suspended solids and particulate carbon were significant. In spite of a high degree of river-floodplain contact, no significant changes on solutes concentrations were observed between inputs and outputs, enough to alter the transport of solutes though the Pantanal, indicating equilibrium in biogeochemical process on floodplain.

World Rivers

The dataset presents 687 rivers associated to 405 Major River Basins. Data was collected within the framework of the BGR-UNESCO "World-wide Hydrogeological Mapping and Assessment Programme" (WHYMAP): www.whymap.org Surface water Transboundary