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- Villa Solis, Ana
(författare)
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Risk assessment of erosion and losses of particulate phosphorus : a series of studies at laboratory, field and catchment scales
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Phosphorus (P) losses from agricultural land are considered a major contributor to eutrophication in many aquatic ecosystems. Areas more vulnerable to losses of P need to be identified in order to effectively apply mitigation measures aimed at reducing total loads of P. This thesis focuses on the identification of soils and fields vulnerable to losses of particulate P (PP) due to erosion. Two simple soil dispersion tests to estimate the initial risk of soil and P mobilization (DESPRAL and SST) were tested and compared in the laboratory. The outcome was combined with data relative to source (soil P content) and transport (unit stream power length-slope topographic factor calculated from a high resolution digital elevation model) risks to establish probable causes of P losses at field scale and to target critical source areas at catchment scale. DESPRAL showed higher precision and shorter execution time than SST, in addition to its already proven validation and reproducibility. Also, compared with other methods, the test returned a wider range of values for each textural class, allowing the differentiation of soils within these classes. This is especially important for finetextured soils, which are the most sensitive to the mobilization of particles. The study of long-term P and sediment losses from five fields confirmed the relevance of adequately identifying the source and transport conditions within fields when assigning appropriate countermeasures. Finally, the assessment of long-term losses from two contrasting catchments highlighted how transport and mobilization risks have a greater effect on P losses due to erosion than P accumulation in soil. When ranking the fields within both catchments according to this prioritization of factors, a greater number of high-risk fields were found in the catchment with more pronounced transport pathways. The outcome of this thesis is the proposal of methodology whereby easily obtainable data can be used in risk assessments to identify fields and catchments vulnerable to PP losses. The knowledge gained provides a good starting point to improve these assessments by incorporating means for prioritizing different mitigation measures currently not performed in Sweden.
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| 2. |
- Villa Solis, Ana, et al.
(författare)
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Soil dispersion tests combined with topographical information can describe field-scale sediment and phosphorus losses
- 2014
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Ingår i: Soil Use and Management. - : Wiley. - 0266-0032 .- 1475-2743. ; 30, s. 342-350
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Tidskriftsartikel (refereegranskat)abstract
- Methods for estimating sediment and phosphorus (P) transfer from agricultural land to surface waters are needed to mitigate their adverse impact on water quality. This study quantified sediment and P losses from five agricultural fields and evaluated the patterns observed based on the intrinsic risk of sediment and P mobilization from the soil, together with field topographical and hydrological data. The mobilization risk was estimated using the environmental soil dispersion test DESPRAL. High-resolution LiDAR elevation data and crop management data were used to describe transport and delivery of the material mobilized. Annual flow-weighted suspended solids (SS) concentration in drainage water ranged from 48 to 374 mg/L, total P (TP) from 0.12 to 0.39 mg/L and unreactive P (UP) from 0.08 to 0.33 mg/L. The mobilization risk, measured as turbidity in the aliquot recovered from the dispersion test, varied from 781 to 2310 nephelometric turbidity units (NTU). The method proved to be efficient in describing and differentiating sediment and P mobilization potential between fields. The topographical data also showed large differences between fields, with the length-slope (LS) parameter varying from 0.037 to 0.999. Based on assessments of source (mobilization risk) and transport factors (LS, crop management data), it was possible to characterize fields as favoured or limited in terms of source and transport and to explain the long-term SS and P losses observed at field scale.
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