Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5743704 | Ecological Engineering | 2017 | 18 Pages |
â¢The first study focusing the temporal aspect of river P legacy under subtropical environment from Southern Brazil.â¢Hedley P fractionation is a useful tool to investigate the sediment P lability.â¢No-tillage increases the sediment labile organic P pools whereas conventional tillage showed higher moderately and non-labile P pool.â¢Seasonal variation reveals high sediment P during winter months, especially under CT tobacco cultivation.â¢Bioavailable P is mainly associated to Fedcb, Alox and Aldcb contents.
Measuring lability of anthropogenically enriched sediment-bound phosphorus (P) to water is a useful tool in ecological monitoring and planning mitigation to tackle diffuse P sources to surface waters. In current study, the sediment-associated total P, P fractions, and P lability accounting for river P legacy was determined. We monitored six representative headwater sub-catchments differing in land-use and management i.e., forest, recently turned low agriculture under conventional-tillage (CT), low agriculture under CT dominated with Ilex paraguariensis plantations, intense agriculture under CT, intense agriculture under no-tillage (NT), and highly anthropic urban receiving untreated sewage; and five sites on the main river in Guaporé river from October 2012 to October 2014. Total P and individual P fractions in 63-μm particle size were determined following the Hedley fractionation and the mean TP concentration lied between 752 mg kgâ1 in forest to as high as 1738 mg kgâ1 in highly anthropic sediments. The individual P fraction when pooled for different P lability indicated 10, 35, and 55% of TP as labile, moderately labile and non-labile P, respectively. With a land use shift from forest to highly anthropic urban, an increase in labile P (172%), moderately labile P (705%) and non-labile P (874%) was observed. The consistent higher values of non-labile (Pi + PoHID-0.5) and residual P in urban, high agriculture and main river sediment indicates the high P affinity due to the presence of high Fe/Al oxides. Temporal analysis revealed that regardless of P lability, a higher concentration was found in winter months (July to November) particularly under CT sub-catchment showing high sediment production and increased transport of added P during tobacco cultivation period. The results provided a baseline to revisit the current fertilization and soil management practices to minimize the river P legacy for sustainable ecological management.
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