The combined effect of geology, phosphate sources and runoff on phosphate export from drainage basins

Grobler, D. C.; Silberbauer, Michael

doi:10.1016/0043-1354(85)90365-3

Cited by 53 publications

(27 citation statements)

References 13 publications

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“…al., 1990;Dillon and Kirchner, 1975;Rekolainen, 1990;Correll et al, 1992;Nearing et al, 1993), but some studies have found no apparent effect of agricultural land use on N and P discharges (Owens et al, 1991;Thomas et al, 1992). Since P discharge is related to transport of suspended particles, the influence of agriculture on P discharge may be outweighed by differences in the geochemistry and erodibility of sediments among watersheds (Grobler and Silberbauer, 1985;Virrhi et al, 1991;Dillon and Kirchner, 1975; 0 20 40 60 80 Percentage Cropland Watershed discharges of P are often difficult to quantify because P is strongly associated with suspended particles which may be discharged primarily during short, unpredictable periods of high flow (Walling and Web, 1985;Kronvang, 1992). However, we were able to sample high flow episodes with our automated samplers.…”

Section: Water Dischargementioning

confidence: 99%

NONPOINT SOURCE DISCHARGES OF NUTRIENTS FROM PIEDMONT WATERSHEDS OF CHESAPEAKE BAY¹

Jordan

Correll

Weller

1997

J American Water Resour Assoc

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We measured annual discharges of water, sediments, and nutrients from 10 watersheds with differing proportions of agricultural lands in the Piedmont physiographic province of the Chesapeake Bay drainage. Flow-weighted mean concentrations of total N, nitrate, and dissolved silicate in watershed discharges were correlated with the proportion of cropland in the watershed. In contrast, concentrations of P species did not correlate with cropland.Organic P and C correlated with the concentration of suspended particles, which differed among watersheds. Thus, the ratio of N:P:Si in discharges differed greatly among watersheds, potentially affecting N, P or Si limitation of phytoplankton growth in the receiving waters. Simple regression models of N discharge versus the percentage of cropland suggest that croplands discharge 29-42 kg N ha-1 y r l and other lands discharge 1.2-5.8 kg N ha-1 yr-1. We estimated net anthropogenic input of N to croplands and other lands using county level data on agriculture and N deposition from the atmosphere. For most of the study watersheds, N discharge amounted to less than half of the net anthropogenic N.(KEY TERMS: nonpoint source pollution; nutrients; water quality; agriculture; watersheds; Chesapeake Bay.)

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Section: Water Dischargementioning

confidence: 99%

NONPOINT SOURCE DISCHARGES OF NUTRIENTS FROM PIEDMONT WATERSHEDS OF CHESAPEAKE BAY¹

Jordan

Correll

Weller

1997

J American Water Resour Assoc

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“…Atmospheric deposition is an additional source of N (Berner and Berner, 1996;Seitzinger and Kroeze, 1998;Tiessen, 1995). Natural inputs of N and P to groundwater are smaller and can involve downward leaching of N and P released from soil organic matter, in situ release from organic matter in the aquifer and, for P, release from Fe-oxides under anoxia (Carlyle and Hill, 2001) and weathering of mineral phases (Dillon and Kirchner, 1975;Grobler and Silberbauer, 1985).…”

Section: Nitrogen and Phosphorus In Groundwatermentioning

confidence: 99%

Nutrient inputs to the coastal ocean through submarine groundwater discharge: controls and potential impact

Slomp

Cappellen

2004

Journal of Hydrology

806

569

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Nutrient input through submarine groundwater discharge (SGD) rivals river inputs in certain regions and may play a significant role in nutrient cycling and primary productivity in the coastal ocean. In this paper, we review the key factors determining the fluxes of nitrogen (N) and phosphorus (P) associated with SGD and present a compilation of measured rates. We show that, in particular, the water residence time and the redox conditions in coastal aquifers and sediments determine fluxes and ratios of N and P in SGD. In many coastal groundwater systems, and especially in contaminated aquifers, N/P ratios exceed those in river water and are higher than the Redfield ratio. Thus, anthropogenically driven increases in SGD of nutrients have the potential to drive the N-limited coastal primary production to P-limitation. River input of N and P to the coastal ocean has doubled over the past 50 yr. Results of a dynamic biogeochemical model for the C, N and P cycles of the global proximal coastal ocean (which includes large bays, the open water part of estuaries, deltas, inland seas and salt marshes), suggest that this has led to a factor 2 increase in primary production and biomass and a decline in water column N/P ratios, i.e. the system has become more N-limiting. With the same model, we show that an increase of SGD-N fluxes to , 0.7-1.1 Tmol yr 21 (with a SGD N/P ratio of 100; equal to ,45 -70% of pre-human riverine N-inputs) is required to drive the coastal ocean to P-limitation within the next 50 yr. q

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“…In fact, the reduction of the soluble bioavailable P-form in the studied basins must clearly take into account their different physiographies (e.g. Grobler and Silberbauer, 1985). Soluble P pathways and dynamics, as well as P retention in soils, vary significantly between both catchments, although their agricultural practices and land-uses remain very similar.…”

Section: Study Sitesmentioning

confidence: 99%

Phosphorus Desorption Dynamics in Soil and the Link to a Dynamic Concept of Bioavailability

et al. 2004

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Soils under intensive livestock farming and heavily fertilized with animal manure may have elevated soil phosphorus (P) contents. We determined P desorption kinetics in batch experiments using soils from a pot experiment where grass was cropped on a P‐rich noncalcareous sandy soil without P addition, to lower the soil P content. A diffusion model was used to describe P desorption kinetics from a spherical aggregate. The model was calibrated with data from the batch experiments. Simulation results show that in the pot experiment, P desorption from the solid phase of the inner layers was initially far from equilibrium with the rest of the aggregate, but desorption came closer to equilibrium as the soil P content decreased further. A simple tool is presented, referred to as the dynamic bioavailability index (DBI), to determine whether kinetics of P desorption limits plant uptake. This tool is the dimensionless ratio of the modeled maximal diffusive flux from soil aggregates to solution and the plant uptake rate measured in the pot experiment. The DBI was initially much larger than one; the maximal possible P desorption rate exceeded the uptake rate, so uptake was not limited by desorption. The DBI stabilized at a value somewhat larger than one after a while, due to soil transport limitations. This decrease coincided with a large decrease of the P content in the grass to a value (far) below what is considered as optimal; the supply rate of P from soil to the root cannot meet the demand needed for optimal P uptake. The DBI could be seen as a promising onset to a new dynamic approach of bioavailability.

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The combined effect of geology, phosphate sources and runoff on phosphate export from drainage basins

Cited by 53 publications

References 13 publications

NONPOINT SOURCE DISCHARGES OF NUTRIENTS FROM PIEDMONT WATERSHEDS OF CHESAPEAKE BAY¹

NONPOINT SOURCE DISCHARGES OF NUTRIENTS FROM PIEDMONT WATERSHEDS OF CHESAPEAKE BAY¹

Nutrient inputs to the coastal ocean through submarine groundwater discharge: controls and potential impact

Phosphorus Desorption Dynamics in Soil and the Link to a Dynamic Concept of Bioavailability

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The combined effect of geology, phosphate sources and runoff on phosphate export from drainage basins

Cited by 53 publications

References 13 publications

NONPOINT SOURCE DISCHARGES OF NUTRIENTS FROM PIEDMONT WATERSHEDS OF CHESAPEAKE BAY1

NONPOINT SOURCE DISCHARGES OF NUTRIENTS FROM PIEDMONT WATERSHEDS OF CHESAPEAKE BAY1

Nutrient inputs to the coastal ocean through submarine groundwater discharge: controls and potential impact

Phosphorus Desorption Dynamics in Soil and the Link to a Dynamic Concept of Bioavailability

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Product

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NONPOINT SOURCE DISCHARGES OF NUTRIENTS FROM PIEDMONT WATERSHEDS OF CHESAPEAKE BAY¹

NONPOINT SOURCE DISCHARGES OF NUTRIENTS FROM PIEDMONT WATERSHEDS OF CHESAPEAKE BAY¹