Phosphorus and the Chesapeake Bay: Lingering Issues and Emerging Concerns for Agriculture (original) (raw)
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Net anthropogenic phosphorus inputs: spatial and temporal variability in the Chesapeake Bay region
Biogeochemistry, 2008
We estimated net anthropogenic phosphorus inputs (NAPI) in the Chesapeake Bay region. NAPI is an index of phosphorus pollution potential. NAPI was estimated by quantifying all phosphorus inputs and outputs for each county. Inputs include fertilizer applications and non-food phosphorus uses, while trade of food and feed can be an input or an output. The average of 1987, 1992, 1997, and 2002 NAPI for individual counties ranged from 0.02 to 78.46 kg P ha−1 year−1. The overall area-weighted average NAPI for 266 counties in the region was 4.52 kg P ha−1 year−1, indicating a positive net phosphorus input that can accumulate in the landscape or can pollute the water. Large positive NAPI values were associated with agricultural and developed land cover. County area-weighted NAPI increased from 4.43 to 4.94 kg P ha−1 year−1 between 1987 and 1997 but decreased slightly to 4.86 kg P ha−1 year−1 by 2002. Human population density, livestock unit density, and percent row crop land combined to explain 83% of the variability in NAPI among counties. Around 10% of total NAPI entering the Chesapeake Bay watershed is discharged into Chesapeake Bay. The developed land component of NAPI had a strong direct correlation with measured phosphorus discharges from major rivers draining to the Bay (R 2 = 0.81), however, the correlation with the simple percentage of developed land was equally strong. Our results help identify the sources of P in the landscape and evaluate the utility of NAPI as a predictor of water quality.
Water, Air, and Soil Pollution, 2005
This paper compares phosphorus (P) concentrations in sediments from two watersheds, one with, and one without, intensive animal agriculture. The watersheds are in the coastal plain of the Chesapeake Bay and have similar physiographic characteristics. Agriculture in the Pocomoke River, MD, watershed supplied 2.7 percent of all broiler chickens produced in the USA in 1997. Poultry litter is an abundant, local source of manure for crops. Broiler chickens are not produced in the Popes Creek, VA, watershed and poultry manure is, therefore, not a major source of fertilizer. The largest concentrations of P in sediment samples are found in floodplain and main-stem bottom sediment in both watersheds. Concentrations of total P and P extracted with 1N HCl are significantly larger in main-stem bottom sediments from the Pocomoke River than in main-stem bottom sediments from Popes Creek. Larger concentrations of P are associated with what are potentially redox sensitive iron oxyhydroxides in sediment samples from the Pocomoke River watershed than are associated with what are potentially redox sensitive iron oxyhydroxides in sediment samples from the Popes Creek watershed. Data for P and iron (Fe) concentrations in sediments from the Popes Creek watershed provide a numerical framework (baseline) with which to compare P and Fe concentrations in sediment from the Pocomoke River watershed.
Phosphorus export across an urban to rural gradient in the Chesapeake Bay watershed
Journal of Geophysical Research: Biogeosciences, 2012
Watershed export of phosphorus (P) from anthropogenic sources has contributed to eutrophication in freshwater and coastal ecosystems. We explore impacts of watershed urbanization on the magnitude and export flow distribution of P along an urban-rural gradient in eight watersheds monitored as part of the Baltimore Ecosystem Study Long-Term Ecological Research site. Exports of soluble reactive phosphorus (SRP) and total P (TP) were lowest in small watersheds with forest and low-density residential land use (2.8-3.1 kg À1 km À2 yr À1). In contrast, SRP and TP exports increased with watershed impervious surface coverage and reached highest values in a small urban watershed (24.5-83.7 kg À1 km À2 yr À1). Along the Gwynns Falls, a larger watershed with mixed land use, the greatest proportion of SRP (68%) and TP (75%) was contributed from the lower watershed, where urban areas were the dominant land use. Load duration curve analysis showed that increasing urbanization in watersheds was associated with shifts in P export to high-flow conditions (>2 mm d À1). SRP concentrations during low-flow conditions at urban headwater sites were highest during summer and lowest during winter. This seasonal pattern was consistent with sediment incubation experiments showing that SRP release from sediments was temperature dependent. Our results suggest that shifts in streamflow and alterations in water temperatures owing to urbanization and climate can influence stream water P concentrations and P export from urban watersheds.
Water Quality Trends Following Anomalous Phosphorus Inputs to Grand Bay, Mississippi, USA
Gulf and Caribbean Research, 2018
IntroductIon Grand Bay National Estuarine Research Reserve (GB-NERR) is nitrogen-limited (Blackburn 2000, Amacker 2013, Baine 2017) and adjacent to a phosphate fertilizer production facility (Mississippi Phosphates Corporation, MPC, Figure 1). The MPC produced diammonium phosphate (DAP) fertilizer from the 1960s until late 2014. Calcium sulfate, or phosphogypsum, a byproduct of this process, was stored in large stacks as waste. Phosphogypsum is rich in phosphorus, highly acidic (pH ~2 .4), and contains several impurities such as radionuclides, heavy metals, fluoride, and sulfide (
The Distribution of Phosphorus in Popes Creek
2005
This paper compares phosphorus (P) concentrations in sediments from two watersheds, one with, and one without, intensive animal agriculture. The watersheds are in the coastal plain of the Chesapeake Bay and have similar physiographic characteristics. Agriculture in the Pocomoke River, MD, watershed supplied 2.7 percent of all broiler chickens produced in the USA in 1997. Poultry litter is an abundant, local source of manure for crops. Broiler chickens are not produced in the Popes Creek, VA, watershed and poultry manure is, therefore, not a major source of fertilizer. The largest concentrations of P in sediment samples are found in floodplain and main-stem bottom sediment in both watersheds. Concentrations of total P and P extracted with 1N HCl are significantly larger in main-stem bottom sediments from the Pocomoke River than in main-stem bottom sediments from Popes Creek. Larger concentrations of P are associated with what are potentially redox sensitive iron oxyhydroxides in sedi...
Potential availability of sedimentary phosphorus to sediment resuspension in Florida Bay
Global Biogeochemical Cycles, 2004
1] Several studies have suggested that phosphorus is a limiting nutrient for seagrass and phytoplankton growth in much of Florida Bay. In fact, soluble reactive phosphate concentrations in Florida Bay waters can be as low as a few nM. Sediments represent the largest phosphorus reservoir because Florida Bay sediments are dominated by carbonate, which has a strong capacity to retain phosphorus. The supply of phosphorus to the water column from sediment resuspension is potentially important in providing the nutrients required for phytoplankton production. Applying an improved sequential extraction technique to sediments collected from 40 geographically representative stations in Florida Bay, this study provides the first detailed spatial distribution of total sedimentary phosphorus (TSP) and its partitioning into five chemically distinguishable pools in the surface, fine-grained sediments of the bay. A strong gradient of decreasing TSP concentration was observed from the west (14.6 mmol g À1 ) to east (1.2 mmol g À1 ) across the central bay. The spatial pattern of TSP is consistent with distribution of both seagrass and phytoplankton that are limited by available phosphorus in Florida Bay. Among the five pools, the authigenic carbonate fluorapatite, biogenic apatite and CaCO 3 -bound phosphorus account for the largest fraction (45%) of TSP, of which inorganic phosphorus is the dominant form, and organic phosphorus accounts for about 30% in the western and north central regions and less than 10% in other areas of Florida Bay. The second largest pools are the refractory organic phosphorus (24% of TSP) and reductant-soluble inorganic phosphorus (19% of TSP). Readily exchangeable phosphorus accounts for 8% of TSP, of which organic phosphorus is 60%. Detrital apatite phosphorus of igneous or metamorphic origin represents the smallest fraction, only 5% of TSP. Spatial distribution of phosphorus and iron in sediments indicates that external sources of these two essential plant nutrients to Florida Bay are spatially separated with phosphorus introduced by west coast waters across the western margin of Florida Bay and iron from freshwater flow into the eastern region.