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The error in stream sediment phosphorus fractionation and sorption properties effected by drying pretreatments.
- Source :
- Journal of Soils & Sediments: Protection, Risk Assessment, & Remediation; Mar2019, Vol. 19 Issue 3, p1587-1597, 11p
- Publication Year :
- 2019
-
Abstract
- Purpose: Stream sediment can control phosphorus (P) in the water column at baseflow. Two common laboratory analyses of sediment P are the equilibrium phosphate concentration at net zero sorption (EPC<subscript>0</subscript>) and P fractionation. Good sample handling ensures representative results, but oftentimes, studies rely on air-dried or freeze-dried samples, which alters sediment biogeochemistry. How and to what extent this influences EPC<subscript>0</subscript> and P fractionation remains unclear. We therefore examine pretreatment effects on sediment EPC<subscript>0</subscript> and P fractionation.Materials and methods: We collected fine sediments (< 2 mm) from streams in the Tukituki River and Reporoa Basins in New Zealand (n = 31 sediments). Subsamples were then either kept fresh, frozen then lyophilized (freeze-dried), or dried at 40 °C for 2 weeks (air-dried). Measurements of EPC<subscript>0</subscript> and P fractionation were made in triplicate. The sequential P fractionation scheme determined five different P pools: NH<subscript>4</subscript>Cl (labile P), NaOH reactive P (RP; metal oxide-bound P) and unreactive P (URP; organic P), HCl (Ca-mineral P), and residual P. Along with statistical comparisons between fresh results and the two pre-treatments, we explored correlations between pre-treatment effects and sediment physicochemical characteristics.Results and discussion: The sediments had generally low EPC<subscript>0</subscript> (majority < 0.020 mg P L<superscript>−1</superscript>), and uncertainty in EPC<subscript>0</subscript> increased with concentration magnitude. While there were sediment-specific changes in EPC<subscript>0</subscript> with pre-treatment, there was no consistent bias caused by pre-treatment. However, the differences between the fresh and air-dried sediment EPC<subscript>0</subscript> were larger and more variable than between fresh and freeze-dried sediment. For P fractionation, the Tukituki sediments were enriched in HCl-P, while Reporoa sediments had more NaOH-RP and NaOH-URP. Despite large sediment-specific changes, the overall effects of freeze- and air-drying sediment were increased NH<subscript>4</subscript>Cl-P (estimated average effect, θ̂ = + 0.63 and + 3.7 mg P kg<superscript>−1</superscript>), no significant changes for NaOH-RP, contrasting changes in NaOH-URP (− 3.4 and + 3.3 mg P kg<superscript>−1</superscript>), and decreased HCl-P (− 40 and − 33 mg P kg<superscript>−1</superscript>).Conclusions: We found that drying sediment significantly influenced EPC<subscript>0</subscript> and P fractions (especially the NH<subscript>4</subscript>Cl-P fraction). Air-drying was particularly error-prone and should be avoided. The use of freeze-drying to preserve samples for later analyses and improve ease of handling may be used with appropriate consideration of the research objectives and the error introduced by freeze-drying. However, we recommend using fresh sediments for analyses whenever possible, as they best represent natural conditions. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 14390108
- Volume :
- 19
- Issue :
- 3
- Database :
- Complementary Index
- Journal :
- Journal of Soils & Sediments: Protection, Risk Assessment, & Remediation
- Publication Type :
- Academic Journal
- Accession number :
- 134940604
- Full Text :
- https://doi.org/10.1007/s11368-018-2180-3