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Nutrient discharge into rivers and estuaries and the factors that control it need to be further understood to decrease the risk of harmful algae blooms on these ecosystems. Preliminary seasonal physicochemical parameters at six stations along the Negro River Estuary (Argentina) were studied during 2019 (Austral summer, winter, and spring) with high- and low-frequency data. Three of the stations were mainly estuarine-influenced and three were marine-influenced ones. The concentration of phosphate (P), river discharge, meteorological conditions, seasonality, and physicochemical variables were analyzed. Total phosphorus (TP) showed seasonal variations and was higher than previously reported for the upper watershed in all stations in the warmer months, except for the marine control one. Orthophosphate values were also high compared to previous watershed data and changed independently of TP fluctuations. Changing turbidity, water temperature, pH, and conductivity did not appear to have an essential role in phosphorus variations. An unexplained high TP spike in the late spring sample shows the need for further research in the area, while the seawater mixing with P-rich river water could be acting as a dilution agent at the mouth of the river. [ABSTRACT FROM AUTHOR]

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Soil erosion is an open topic, not only because soil fertility is lost, but also because nutrients are spilled into water bodies, thereby causing pollution. Research carried out in this field has amply described this process, but the interaction between these factors is complex and experimental research is needed to understand the production of loads of nutrients for different land uses. This paper describes a long-term monitoring case study using high-resolution rainfall data and runoff samples, carried out in the Lake Vico basin (Central Italy) to determine the phosphorus (P) export during erosive rainfall events. State of the art GIS-based basin characterization and advanced rainfall-runoff models are employed in order to describe the relationship between nutrient export and rainfall or runoff time distribution. Results show that the phosphorus export is strongly related to such time distributions, and less to the cumulative amount of rainfall or runoff. [ABSTRACT FROM AUTHOR]

The article reports on the results of the research conducted to assess the impact of wildfire on the phosphorus content and stream exports of coarse matter on two burnt forested headwater catchments at East Kiewa valley in Victoria. Researchers collected stream water samples to measure the discharge and turbidity and found that the amount of coarse matter exported during spring or winter declined significantly. Moreover, export rates during autumn or summer remained constant.

From each of 46 watersheds in glaciated northwestern Pennsylvania we estimated phosphorus export (kg P/ha/yr) from weekly or twice-weekly measured stream phosphorus concentrations and measured stream discharges, and determined land covers using GIS. Simple and step-down multiple regression analyses yielded models that explained 24% of the variation in P export using land cover within whole watersheds, and 64% of the variation using land cover within 200 m riparian buffers. We used these models to predict P loading to seven lakes and found that predicted lake [P] was consistent with measured lake [P]. To estimate pre-settlement lake [P] we reapplied the P export models with the assumption that human-impacted land covers were originally forests. Predicted (hindcast) pre-settlement lake [P] indicated that six of the seven lakes were edaphically mesotrophic (10 < [P] < 20 μg/l). Lake remediation targets set on the assumption that area lakes were historically oligotrophic ([P] < 10 μg/l) will be unattainable. [ABSTRACT FROM AUTHOR]

Phosphorus (P) is a limiting nutrient in many freshwater ecosystems and increases in its availability can lead to eutrophication. Effective management of P in freshwaters requires quantitative estimates of P supply from all significant sources. A simple GIS-based model, capable of predicting total diffuse source phosphorus export from catchments using readily available data, has been developed. The model is based on the idea of export coefficients but includes the effects of topography (slope and cumulative area), soil type (using the UK Hydrology of Soil Types (HOST) classification) and climate (hydrologically effective rainfall) as well as land use. Uncertainty in key model parameters is accounted for using Monte Carlo simulation which involves random sampling from probability density functions in a large number of iterations. This reduces the need for subjective optimisation of export coefficients. The model has been applied to the Greens Burn catchment, Scotland and predicts P exports within the confidence limits of the measured values. [ABSTRACT FROM AUTHOR]