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Hydrogeochemistry of Fe and Mn in small boreal streams: The role of seasonality, landscape type and scale 总被引：1，自引：0，他引：1
Louise Björkvald Ishi Buffam Hjalmar Laudon Carl-Magnus Mörth 《Geochimica et cosmochimica acta》2008,72(12):2789-2804
Stream water from a stream network of 15 small boreal catchments (0.03-67 km2) in northern Sweden was analyzed for unfiltered (total) and filtered (<0.4 μm) concentrations of iron (Fetot and Fe<0.4) and manganese (Mntot and Mn<0.4). The purpose was to investigate the temporal and spatial dynamics of Fe, Mn and dissolved organic carbon (DOC) as influenced by snow melt driven spring floods and landscape properties, in particular the proportion of wetland area. During spring flood, concentrations of Fetot, Fe<0.4, Mntot, Mn<0.4 and DOC increased in streams with forested catchments (<2% wetland area). In catchments with high coverage of wetlands (>30% wetland area) the opposite behavior was observed. The hydrogeochemistry of Fe was highly dependent on wetlands as shown by the strong positive correlation of the Fetot/Altot ratio with wetland coverage (r2 = 0.89, p < 0.001). Furthermore, PCA analysis showed that at base flow Fetot and Fe<0.4 were positively associated with wetlands and DOC, whereas they were not associated during peak flow at spring flood. The temporal variation of Fe was likely related to varying hydrological pathways. At peak discharge Fetot was associated with variables like silt coverage, which highlights the importance of particulates during high discharge events. For Mn there was no significant correlation with wetlands, instead, PCA analysis showed that during spring flood Mn was apparently more dependent on the supply of minerogenic particulates from silt deposits on the stream banks of some of the streams. The influence of minerogenic particulates on the concentration of, in particular, Mn was greatest in the larger, lower gradient streams, characterized by silt deposits in the near-stream zone. In the small forested streams underlain by till, DOC was of greater importance for the observed concentrations, as indicated by the positive correlation of both Fetot and Fe<0.4 with DOC (r2 = 0.77 and r2 = 0.76, p < 0.001) at the smallest headwater forest site. In conclusion, wetland area and DOC were important for Fe concentrations in this boreal stream network, whereas silt deposits strongly influenced Mn concentrations. This study highlights the importance of studying stream water chemistry from a landscape perspective in order to address future environmental issues concerning mobility of Fe, Mn and associated trace metals. 相似文献
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Noah R. Lottig Ishi Buffam Emily H. Stanley 《Aquatic Sciences - Research Across Boundaries》2013,75(4):619-630
Processes occurring at various scales interact to influence the export of organic carbon from watersheds to freshwater ecosystems and eventually the ocean. The goal of this study was to determine if and how differences in wetland extent and presence of lakes influenced dissolved organic carbon (DOC) concentrations and yields in streams. We monitored stream flow, DOC and dissolved inorganic carbon concentrations periodically for 2 years at four sites with forested watersheds, four sites with wetland watersheds, and four sites with wetland watersheds that also contained in-network lakes. As expected, the presence of wetlands resulted in higher DOC concentrations and yields, but the impact of lakes was less clear on the magnitude of DOC concentrations and yields. With respect to temporal dynamics, we found positive relationships between stream flow and DOC concentration (median r2 = 0.89) in streams without upstream lakes. The relationships for forested sites are among the strongest reported in the literature, and suggest a clear shift in hydrologic flowpath from intersecting mineral soils at low flow, to organic soils at high flow. In streams with upstream lakes, the relationship between flow and concentration was non-significant for three of four sites unless time lags with flow were applied to the concentration data, after which the relationship was similar to the non-lake streams (median r2 = 0.95). These findings suggest that lakes buffering temporal patterns in streams by hydrologically delaying pulses of carbon, but provide little support that in-line lakes have a net effect on carbon exports in this region. 相似文献
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Neil Cory Ishi Buffam Hjalmar Laudon Louise Bjrkvald Carl-Magnus Mrth Stephan Khler Kevin Bishop 《Applied Geochemistry》2009,24(9):1677-1685
The adverse impacts of the inorganic labile monomeric Al (Ali) fraction on aquatic organisms have meant that Al (Altot) determination and even speciation has become a routine part of environmental monitoring and assessment. However, if samples are not filtered prior to analysis then particulate Al (Altot(p)) could influence the determination of Altot, and therefore the determination of the more toxicologically important (Ali), both when it is measured analytically or modelled from Altot. This paper shows that the Al/DOC ratio in unfiltered samples can identify the Altot(p) fraction, and thus improve the speciation of Ali. These findings are based on data from a study in a 67 km2 catchment in northern Sweden during the snowmelt-driven spring flood of two consecutive years. Filtered and unfiltered samples were studied to determine the spatial and temporal patterns in Altot(p). The concentrations of Altot(p) were greatest in larger downstream sites where significant silt deposits are located. The sites with no silt in their drainage area showed a mean difference between filtered (Altot(f)) and unfiltered (Altot(uf)) samples of 6%, while sites with silt deposits had a mean difference of 65%. The difference between filtered and unfiltered samples was greatest at peak flow. Spikes in Altot(p) did not behave consistently during fractionation with a cation exchange column, resulting in increases in either measured Ali(f) or non-labile monomeric Al (Alo(f)). Altot(p) spikes were associated with sharp increases in the Al:DOC ratio. The baseflow Al:DOC ratio could be used to model filtered Altot from DOC with a Spearman rho of 0.75. 相似文献
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Aqua Incognita: the unknown headwaters 总被引：1，自引：1，他引：0
K. Bishop I. Buffam M. Erlandsson J. Fölster H. Laudon J. Seibert J. Temnerud 《水文研究》2008,22(8):1239-1242
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