Controls on Catchment‐Scale Patterns of Phosphorus in Soil, Streambed Sediment, and Stream Water

Abstract

Many models of phosphorus (P) transfer at the catchment scale rely on input from generic databases including, amongst others, soil and land use maps. Spatially detailed geochemical data sets have the potential to improve the accuracy of the input parameters of catchment-scale nutrient transfer models. Furthermore, they enable the assessment of the utility of available, generic spatial data sets for the modeling and prediction of soil nutrient status and nutrient transfer at the catchment scale. This study aims to quantify the unique and joint contribution of soil and sediment properties, land cover, and point-source emissions to the spatial variation of P concentrations in soil, streambed sediments, and stream water at the scale of a medium-sized catchment. Soil parent material and soil chemical properties were identified as major factors controlling the catchment-scale spatial variation in soil total P and Olsen P concentrations. Soil type and land cover as derived from the generic spatial database explain 33.7% of the variation in soil total P concentrations and 17.4% of the variation in Olsen P concentrations. Streambed P concentrations are principally related to the major element concentrations in streambed sediment and P delivery from the hillslopes due to sediment erosion. During base flow conditions, the total phosphorus (<0.45 microm) concentrations in stream water are mainly controlled by the concentrations of P and the major elements in the streambed sediment.

Biogeochemical hotspots: Role of small water bodies in landscape nutrient processing

“…Physically speaking, phosphorus that is stored within the sediment zone may be washed out during extreme hydrological events such the spring snow melt [Gibson et al, 2001;van der Perk et al, 2007]. There are also biogeochemical factors that may lead to net phosphorus export.…”

Riverbed sediments buffer phosphorus concentrations downstream of sewage treatment works across the River Wensum catchment, UK

“…The sorption and storage of SRP by riverbed sediments downstream of STWs can therefore play a vital role in reducing eutrophication risk during the ecologically sensitive low-flow summer period (Jarvie et al 2006). However, because riverbed sediment chemistry is a major controlling factor on the chemistry of the overlying waterbody, deposition of P-rich fines can also act as a localised source of SRP if concentrations are greater than in the overlying waterbody or if sediments become entrained by biotic mixing and storm events van der Perk et al 2007). Increased P concentrations on the riverbed can also fuel excessive growth of macrophytes and benthic algae which are able to extract nutrients directly from the sediment rather than relying on dissolved SRP (Hilton et al 2006).…”

“…Ultimately, the ability of sediments to sorb P is determined by the chemical composition of the catchment bedrock and superficial geology which whether to produce the soils and sediments that determine the natural background P buffering capacity (Walling et al 2001;van der Perk et al 2007;Ballantine et al 2008). As such, it might be expected that EPC 0 values in the Wensum catchment would be higher in areas where fine glacial till is the dominant superficial deposit and values would be lower in areas covered with coarse sands and gravels.…”

Sediment response to catchment disturbances

“…In these basins, fertilizer use and accelerated soil erosion on agricultural land have resulted in elevated sediment inputs and phosphorus concentrations in stream and lake beds. Streambed sediments that contain excess phosphorus cause increased dissolved phosphorus concentrations in streams during baseflow conditions (e.g., McDowell et al 2001;van der Perk et al 2007). …”