In boreal landscapes, large quantities of dissolved organic carbon (DOC) accumulated in soils are flushed into rivers and streams during snowmelt. These inputs supply energy to aquatic microbes, affect pH, and can promote the transportation of metals to streams and rivers. However, during the spring flood, changes in stream DOC are influenced by the structure of the catchment (e.g., forest vs. wetland cover), where different solutes are stored in soils, and snowmelt hydrology. While these mechanisms have been studied extensively in ‘pristine’ boreal landscapes, the influence of agricultural and urban land use on DOC flushing during snowmelt is poorly understood in this region. To understand these influences, I measured DOC, along with pH, conductivity, and discharge, during snowmelt at three boreal streams draining agricultural and urban lands. I analyzed chemical patterns using discharge-concentration curves that reveal whether solutes are stable (chemostatic) or change (chemodynamic) during floods. Similar to observations made in forested catchments elsewhere, DOC was chemodynamic at all sites, increasing with discharge; however, two sites did show dilution at the very highest flows. pH declined with discharge at one site, but did not change at the other two. Electrical conductivity declined (was diluted) with increasing discharge for all sites, coinciding with previous studies. These results indicate that the majority of these chemical patterns in boreal streams influenced by agriculture and urban land use are chemodynamic, either increasing or decreasing in concentration with discharge during snowmelt. However more studies are needed to further clarify if patterns human-modified catchments are consistent with models based on boreal forested catchments.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:umu-163172 |
| Date | January 2019 |
| Creators | Söderlund, Erik |
| Publisher | Umeå universitet, Institutionen för ekologi, miljö och geovetenskap |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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