Spatial and temporal variation in particle size and particulate organic matter content in suspended particulate matter from peatland‐dominated catchments in Finland

Abstract

Abstract:Properties of suspended particulate matter play a vital role in transport processes, but information from boreal lowland river systems with high organic loads is limited. This study analysed data from 2 years of sampling at 30 locations in Finland (204 samples in total) using suspended particulate matter samplers to determine effective and absolute particle size and organic fractions. Mean d 50 value was 22 and 49 μm for absolute and effective particle size, respectively. The organic fraction content ranged from 2.1% to 36% (mean 9.6%), highlighting the importance of particle organic matter for suspended particulate matter flux in the region. The results indicated that the suspended particulate matter particle size distribution and load in the study region is dominated by composite particles. There were considerable spatial and temporal variations in transport of organic fractions, effective particle size and degree of aggregation (range 1.5-93%). Headwaters and, in particular, late summer and spring flood conditions with flow peaks produced the largest composite particles, whereas agriculture-dominated sites produced smaller but more tightly compacted particles. Organic plant fibres appeared to play a vital role in floc formation in peat-covered catchments, whereas in agriculture-dominated catchments, land use-derived aggregates dominated the composition. This study provides empirical evidence of the importance of effective particle size measurement in understanding the dynamics of suspended particulate matters in boreal lowland river systems.

Dynamics of fluvial hydro-sedimentological, nutrient, particulate organic matter and effective particle size responses during the U.K. extreme wet winter of 2019–2020

“…At low to medium Q, organic matter rich sediments (e.g., eroded peat soil) might make up a higher proportion of the sediment. The values of % POM observed in this study are within the range reported in existing literature globally ( Madej, 2015 ; Marttila and Klove, 2015 ; Bright et al, 2020 ). However, significantly lower concentrations (0.7–3 mg L −1 ) of POM were exported during the low to medium Q compared to the highest Q (19.5 mg L −1 POM at 20 m 3 s −1 Q).…”

The Flocculation State of Mud in the Lowermost Freshwater Reaches of the Mississippi River: Spatial Distribution of Sizes, Seasonal Changes, and Their Impact on Vertical Concentration Profiles

“…Microscope imaging of sediment captured from freshwater rivers at low (Le et al., 2020), mid (Droppo & Ongley, 1994; Fox et al., 2013), and high latitudes (Droppo et al., 1998) all suggest that material in suspension, and on the bed, are indeed flocculated even in the absence of typical oceanic or estuarine levels of salinity. Various sizing and settling estimates of mud within freshwater suspensions also point to mud existing in some state of aggregation (Bungartz et al., 2006; Marttila & Kløve, 2015; Phillips & Walling, 1999; Woodward & Walling, 2007). Furthermore, recent analyses of vertical concentration profiles from several rivers have shown that mud can indeed be vertically stratified and that flocculation could provide an explanation for the observed behavior (Izquierdo‐Ayala et al., 2021; Lamb et al., 2020; Nghiem et al., 2022).…”

The Physiographic Environment Classification: Decoding Water Quality Landscapes through Hydrochemical Conceptualization

“…All other things being equal, we expect coarsely textured rock/sediment to yield less ne-sediment than ne-textured rock/sediment and weakly-weathered rock/sediment to yield less ne sediment than strongly-weathered rock/sediment (e.g., Whipple and Tucker 1999). Regolith formed in organic sediment is expected to yield more particulate organic matter than regolith formed in inorganic sediments (e.g., Marttila and Kløve 2015).…”