scholarly journals Particles under stress: ultrasonication causes size and recovery rate artifacts with soil-derived POM but not with microplastics

2021 ◽  
Vol 18 (1) ◽  
pp. 159-167
Author(s):  
Frederick Büks ◽  
Gilles Kayser ◽  
Antonia Zieger ◽  
Friederike Lang ◽  
Martin Kaupenjohann
Keyword(s):  
Particle Size ◽  
Organic Matter ◽  
Particulate Organic Matter ◽  
Recovery Rate ◽  
Soil Aggregates ◽  
Terrestrial Ecosystems ◽  
Physiochemical Properties ◽  
The Face ◽  
Average Factor ◽  
Physical Stabilization

Abstract. The breakdown of soil aggregates and the extraction of particulate organic matter (POM) by ultrasonication and density fractionation is a method widely used in soil organic matter (SOM) analyses. It has recently also been used for the extraction of microplastic from soil samples. However, the investigation of POM physiochemical properties and ecological functions might be biased if particles are comminuted during the treatment. In this work, different types of POM, which are representative of different terrestrial ecosystems and anthropogenic influences, were tested for their structural stability in the face of ultrasonication in the range of 0 to 500 J mL−1. The occluded particulate organic matter (oPOM) of an agricultural and forest soil as well as pyrochar showed a significant reduction of particle size at ≥50 J mL−1 by an average factor of 1.37±0.16 and a concurrent reduction of recovery rates by an average of 21.7±10.7 % when being extracted. Our results imply that increasing ultrasonication causes increasing retention of POM within the sedimenting phase, leading to a misinterpretation of certain POM fractions as more strongly bound oPOM or part of the mineral-associated organic matter (MOM). This could, for example, lead to a false estimation of physical stabilization. In contrast, neither fresh nor weathered polyethylene (PE), polyethylene terephthalate (PET) and polybutylene adipate terephthalate (PBAT) microplastics showed a reduction of particle size or the recovery rate after application of ultrasound. We conclude that ultrasonication applied to soils has no impact on microplastic size distribution and thus provides a valuable tool for the assessment of microplastics in soils and soil aggregates.

scholarly journals Particles under stress: Ultrasonication causes size and recovery rate artifacts with soil derived POM, but not with microplastics

2020 ◽  
Author(s):  
Frederick Büks ◽  
Gilles Kayser ◽  
Antonia Zieger ◽  
Friederike Lang ◽  
Martin Kaupenjohann
Keyword(s):  
Particle Size ◽  
Organic Matter ◽  
Particulate Organic Matter ◽  
Recovery Rate ◽  
Soil Aggregates ◽  
Terrestrial Ecosystems ◽  
Physiochemical Properties ◽  
Average Factor ◽  
Carry Over ◽  
Physical Stabilization

Abstract. The breakdown of soil aggregates and the extraction of particulate organic matter (POM) by ultrasonication and density fractionation is a method widely used in soil organic matter (SOM) analyses. It has recently also been used for the extraction of microplastic from soil samples. However, the investigation of some POM physiochemical properties and ecological functions might be biased, if particles are comminuted during the treatment. In this work, different types of POM, which are representative for different terrestrial ecosystems and anthropogenic influences, were tested for their structural stability in face of ultrasonication in a range of 0 to 500 J ml−1. The occluded particulate organic matter (oPOM) of an agricultural and forest soil as well as pyrochar showed a significant reduction of particle size at ≥ 50 J ml−1 by an average factor of 1.37 ± 0.16 and a concurrent reduction of recovery rates by an average of 21.7 ± 10.7 % when being extracted. Our results imply that ultrasonication causes an imitated carry-over of POM to more strongly bound fractions or to the mineral-associated organic matter (MOM) due to enhanced attraction to the mineral phase, which could e.g. lead to a false estimation of physical stabilization. In contrast, neither fresh nor weathered polyethylene (PE), polyethylene terephthalate (PET) and polybutylene adipate terephthalate (PBAT) microplastics showed a reduction of particle size or the recovery rate after application of ultrasound. We conclude that ultrasonication applied to soils has no impact on microplastic size distribution and thus provides a valuable tool for the assessment of microplastics in soils and soil aggregates.

scholarly journals Particulate organic matter composition and organic carbon flux in Arctic valley glaciers: examples from the Bayelva River and adjacent Kongsfjorden

2015 ◽  
Vol 12 (18) ◽  
pp. 15655-15685
Author(s):  
Z.-Y. Zhu ◽  
Y. Wu ◽  
S.-M. Liu ◽  
F. Wenger ◽  
J. Hu ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Particulate Organic Matter ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Concentration Data ◽  
Particulate Nitrogen ◽  
Organic Carbon Flux ◽  
Doc Concentration ◽  
The Face

Abstract. In the face of ongoing global warming and glacier retreat, the composition and flux of organic matter in glacier–fjord systems are key variables for updating the carbon cycle and budget, whereas the role of Arctic valley glaciers seems unimportant when compared with the huge Greenland Ice Sheet. Our field observations of the glacier-fed Bayelva River, Svalbard, and the adjacent Kongsfjorden allowed us to determine the compositions of particulate organic matter from glacier to fjord and also to estimate the flux of organic carbon, both for the river and for Svalbard in general. Particulate organic carbon (POC) and dissolved organic carbon (DOC) in the Bayelva River averaged 56 and 73 μM, respectively, in August 2012. Amino acids (AAs) and phytoplankton pigments accounted for ~ 10 % of the particulate organic matter (POM) in the Bayelva River, while AAs represented > 90 % of particulate nitrogen in fjord surface water, suggesting the strong in situ assimilation of organic matter. Bacteria accounts for 13 and 19 % of the POC in the Bayelva River and the Kongsfjorden, respectively, while values for particulate nitrogen (PN) are much higher (i.e., 36 % in Kongsfjorden). The total discharge from the Bayelva River in 2012 was 29 × 106 m3. Furthermore, we calculated the annual POC, DOC, and PN fluxes for the river as 20 ± 1.6, 25 ± 5.6, and 4.7 ± 0.75 t, respectively. Using the POC content and DOC concentration data, we then estimated the annual POC and DOC fluxes for Svalbard glaciers. Although the estimated POC (0.056 ± 0.02 × 106 t yr−1) and DOC (0.02 ± 0.01 × 106 t yr−1) fluxes of Svalbard glaciers are small compared with those of the Greenland Ice Sheet, the area-weighted POC flux of Svalbard glaciers is twice that of the Greenland Ice Sheet, while the flux of DOC can be 4 to 7 times higher. Therefore, we propose that valley glaciers are efficient high-latitude sources of organic carbon.

scholarly journals Two different microbial communities did not cause differences in occlusion of particulate organic matter in a sandy agricultural soil

2016 ◽  
Author(s):  
Frederick Büks ◽  
Philip Rebensburg ◽  
Peter Lentzsch ◽  
Martin Kaupenjohann
Keyword(s):  
Organic Matter ◽  
Microbial Communities ◽  
Particulate Organic Matter ◽  
Agricultural Soil ◽  
Agricultural Soils ◽  
Soil Aggregates ◽  
Soil Extract ◽  
Microbial Life ◽  
Physico Chemical ◽  
Airborne Microbes

Abstract. Apart from physico-chemical interactions between soil components, microbial life is assumed to be an important factor of soil structure forming processes. Bacterial exudates, the entanglement by fungal hypae and bacterial pseudomycelia as well as fungal glomalin are supposed to provide the occlusion of particulate organic matter (POM) through aggregation of soil particles. This work investigates the resilience of POM occlusion in face of different microbial communities under controlled environmental conditions. We hypothesized that the formation of different communities would cause different grades of POM occlusion. For this purpose samples of a sterile sandy agricultural soil were incubated for 76 days in bioreactors. Particles of pyrochar from pine wood were added as POM analogue. One variant was inoculated with a native soil extract, whereas the control was infected by airborne microbes. A second control soil remained non-incubated. During the incubation, soil samples were taken for taxon-specific qPCR to determine the abundance of Eubacteria, Fungi, Archaea, Acidobacteria, Actinobacteria, α-Proteobacteria and β-Proteobacteria. After the incubation soil aggregates (100–2000 μm) were collected by sieving and disaggregated using ultrasound to subject the released POM to an analysis of organic carbon (OC). Our results show, that the eubacterial DNA of both incubated variants reached a similar concentration after 51 days. However, the structural composition of the two communities was completely different. The soil-born variant was dominated by Acidobacteria, Actinobacteria and an additional fungal population, whereas the air-born variant mainly contained β-Proteobacteria. Both variants showed a strong occlusion of POM into aggregates during the incubation. Yet, despite the different population structure, there were only marginal differences in the release of POM along with the successive destruction of soil aggregates by ultrasonication. This leads to the tentative assumption that POM occlusion in agricultural soils could be resilient in face of changing microbial communities.

Characteristics of Sediment and Organic Carbon Export from Pristine Boreal Forest Watersheds

1982 ◽  
Vol 39 (12) ◽  
pp. 1699-1718 ◽  
Author(s):  
Robert J. Naiman
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Boreal Forest ◽  
Particulate Organic Matter ◽  
Terrestrial Ecosystems ◽  
Dry Weight ◽  
Carbon Export ◽  
Watershed Area ◽  
First Choice ◽  
Spring Freshet

Estimates of the amount of material moving annually from terrestrial ecosystems to the ocean are largely based on an incomplete understanding of events occurring throughout the hydrologic year, and only a vague comprehension of in-stream processes controlling that export. Discharge, suspended sediment, particulate organic matter (POM; > 0.5 μm), dissolved organic carbon (DOC; <0.5 μm diameter), and the percentage of organic matter were measured from 1979 to 1981 in five pristine Quebec streams: First Choice Creek (1st order; watershed area: 0.25 km2), Beaver Creek (2nd order; 1.83 km2), Muskrat River (5th order; 204 km2), Matamek River (6th order; 673 km2), and the Moisie River (9th order; 19 871 km2). All streams, with the exception of First Choice Creek, have a strong spring freshet when 43–55% of the annual discharge occurs. By describing sediment and organic carbon export throughout the annual hydrologic cycle, 1 showed that during the 2-mo spring freshet 71–92% of the annual sediment load is exported but only 59–65% of the annual POM load, and only 47–51% of the annual DOC load. Sediment yield is relatively constant between watersheds (1.5–7.6 g∙m−2∙yr−1), as is POM export (1.0–6.7 g ash-free dry-weight [AFDW]∙m−2∙yr−1); however, export DOC varies from 3.1 g C∙m−2∙yr−1 in First Choice Creek to 48.4 g C∙m−2∙yr−1 in Beaver Creek. There appears to be rapid loading of carbon between 1st- and 2nd-order streams in boreal forests, followed by biological and physical processing as watershed area increases. Thus, for the Moisie River watershed, export of total organic carbon (TOC) is reduced to only 4.7 g C∙m−2∙yr−1. Export of coarse particulate organic matter (> 1 mm) is negligible (normally < 0.1 mg∙L−1), as is oxidation of the suspended load (< 0.5%∙d−1). Effects of summer storms, natural diel variations, and depth of sample from the water column are shown to have a minimal influence on concentrations. Rating curves (kg∙d−1 vs. discharge) are developed to estimate the annual yield of sediment, POM, and DOC, and to evaluate long-term variations. From the results I suggest that in-stream processing and retention devices exert considerable control over the quantity and nature of suspended organic material. Physical processes such as the discharge regime and stream power are relatively less important in determining organic concentrations, but more important in determining sediment concentrations.Key words: seston, carbon, sediment, boreal forest, watershed, river, stream, export

scholarly journals Enzymatic biofilm digestion in soil aggregates facilitates the release of particulate organic matter by sonication

SOIL ◽  
2016 ◽  
Vol 2 (4) ◽  
pp. 499-509 ◽  
Author(s):  
Frederick Büks ◽  
Martin Kaupenjohann
Keyword(s):  
Organic Matter ◽  
Soil Quality ◽  
Particulate Organic Matter ◽  
Extracellular Polymeric Substances ◽  
Soil Aggregates ◽  
Aggregate Stability ◽  
Enzyme Treatment ◽  
Rooting Depth ◽  
Experimental Proof ◽  
Biofilm Detachment

Abstract. The stability of soil aggregates against shearing and compressive forces as well as water-caused dispersion is an integral marker of soil quality. High stability results in less compaction and erosion and has been linked to enhanced water retention, dynamic water transport and aeration regimes, increased rooting depth, and protection of soil organic matter (SOM) against microbial degradation. In turn, particulate organic matter is supposed to support soil aggregate stabilization. For decades the importance of biofilm extracellular polymeric substances (EPSs) regarding particulate organic matter (POM) occlusion and aggregate stability has been canonical because of its distribution, geometric structure and ability to link primary particles. However, experimental proof is still missing. This lack is mainly due to methodological reasons. Thus, the objective of this work is to develop a method of enzymatic biofilm detachment for studying the effects of EPSs on POM occlusion. The method combines an enzymatic pre-treatment with different activities of α-glucosidase, β-galactosidase, DNAse and lipase with a subsequent sequential ultrasonic treatment for disaggregation and density fractionation of soils. POM releases of treated samples were compared to an enzyme-free control. To test the efficacy of biofilm detachment the ratio of bacterial DNA from suspended cells and the remaining biofilm after enzymatic treatment were measured by quantitative real-time PCR. Although the enzyme treatment was not sufficient for total biofilm removal, our results indicate that EPSs may attach POM within soil aggregates. The tendency to additional POM release with increased application of enzymes was attributed to a slight loss in aggregate stability. This suggests that an effect of agricultural practices on soil microbial populations could influence POM occlusion/aggregate stability and thereby carbon cycle/soil quality.

scholarly journals On the treatment of particulate organic matter sinking in large-scale models of marine biogeochemical cycles

2008 ◽  
Vol 5 (1) ◽  
pp. 55-72 ◽  
Author(s):  
I. Kriest ◽  
A. Oschlies
Keyword(s):  
Particle Size ◽  
Organic Matter ◽  
Water Column ◽  
Size Distribution ◽  
Power Law ◽  
Particulate Organic Matter ◽  
Large Scale ◽  
Regional Patterns ◽  
Size Dependent ◽  
Biogeochemical Models

Abstract. Various functions have been suggested and applied to represent the sedimentation and remineralisation of particulate organic matter (POM) in numerical ocean models. Here we investigate some representations commonly used in large-scale biogeochemical models: a constant sinking speed, a sinking speed increasing with depth, a spectrum of particles with different size and different size-dependent sinking velocities, and a model that assumes a power law particle size distribution everywhere in the water column. The analysis is carried out for an idealised one-dimensional water column, under stationary boundary conditions for surface POM. It focuses on the intrinsic assumptions of the respective sedimentation function and their effect on POM mass, mass flux, and remineralisation profiles. A constant and uniform sinking speed does not appear appropriate for simulations exceeding a few decades, as the sedimentation profile is not consistent with observed profiles. A spectrum of size classes, together with size-dependent sinking and constant remineralisation, causes the sinking speed of total POM to increase with depth. This increase is not strictly linear with depth. Its particular form will further depend on the size distribution of the POM ensemble at the surface. Assuming a power law particle size spectrum at the surface, this model results in unimodal size distributions in the ocean interior. For the size-dependent sinking model, we present an analytic integral over depth and size that can explain regional variations of remineralisation length scales in response to regional patterns in trophodynamic state.

scholarly journals Organic carbon flux and particulate organic matter composition in Arctic valley glaciers: examples from the Bayelva River and adjacent Kongsfjorden

2016 ◽  
Vol 13 (4) ◽  
pp. 975-987 ◽  
Author(s):  
Zhuo-Yi Zhu ◽  
Ying Wu ◽  
Su-Mei Liu ◽  
Fred Wenger ◽  
Jun Hu ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Particulate Organic Matter ◽  
Greenland Ice Sheet ◽  
Concentration Data ◽  
Particulate Nitrogen ◽  
Organic Carbon Flux ◽  
Doc Concentration ◽  
The Face ◽  
Arctic Glacier

Abstract. In the face of ongoing global warming and glacier retreat, the composition and flux of organic matter in glacier–fjord systems are key variables for updating the carbon cycle and budget, whereas the role of Arctic valley glaciers seems unimportant when compared with the huge Greenland Ice Sheet. Our field observations of the glacier-fed Bayelva River, Svalbard, and the adjacent Kongsfjorden allowed us to determine the compositions of particulate organic matter from glacier to fjord and also to estimate the flux of organic carbon, both for the river and for Svalbard in general. Particulate organic carbon (POC) and dissolved organic carbon (DOC) in the Bayelva River averaged 56 and 73 µM, respectively, in August, 2012. Amino acids (AAs) and phytoplankton carbon accounted for  ∼ 10 % of the bulk POC in the Bayelva River, while AAs represented > 90 % of particulate nitrogen (PN) in fjord surface water, suggesting the strong in situ assimilation of organic matter. Bacteria accounted for 13 and 19 % of the POC in the Bayelva River and the Kongsfjorden, respectively, while values for PN were much higher (i.e., 36 % in Kongsfjorden). The total discharge from the Bayelva River in 2012 was 29  ×  106 m3. Furthermore, we calculated the annual POC, DOC, and PN fluxes for the river as 20 ± 1.6 tons, 25 ± 5.6 tons, and 4.7 ± 0.75 tons, respectively. Using the POC content and DOC concentration data, we then estimated the annual POC and DOC fluxes for Svalbard glaciers. Although the estimated POC (0.056 ± 0.02  ×  106 tons year−1) and DOC (0.02 ± 0.01  ×  106 tons year−1) fluxes of Svalbard glaciers are small in amount, its discharge-weighted flux of DOC was over twice higher than other pan-Arctic glacier systems, suggesting its important role as a terrestrial DOC source.

scholarly journals On the treatment of particulate organic matter sinking in large-scale models of marine biogeochemical cycles

2007 ◽  
Vol 4 (4) ◽  
pp. 3005-3040
Author(s):  
I. Kriest ◽  
A. Oschlies
Keyword(s):  
Particle Size ◽  
Organic Matter ◽  
Water Column ◽  
Size Distribution ◽  
Power Law ◽  
Particulate Organic Matter ◽  
Large Scale ◽  
Regional Patterns ◽  
Size Dependent ◽  
Biogeochemical Models

Abstract. Various functions have been suggested and applied to represent the sedimentation and remineralisation of particulate organic matter (POM) in numerical ocean models. Here we investigate some representations commonly used in large-scale biogeochemical models: a constant sinking speed, a sinking speed increasing with depth, a spectrum of particles with different size and different size-dependent sinking velocities, and a model that assumes a power-law particle size distribution everywhere in the water column. The analysis is carried out for an idealised one-dimensional water column, under stationary boundary conditions for surface POM. It focuses on the intrinsic assumptions of the respective sedimentation function and their effect on POM mass, mass flux, and remineralisation profiles. A constant and uniform sinking speed does not appear appropriate for simulations exceeding a few decades, as the sedimentation profile is not consistent with observed profiles. A spectrum of size classes, together with size-dependent sinking and constant remineralisation, causes the sinking speed of total POM to increase with depth. This increase is not strictly linear with depth. Its particular form will further depend on the size distribution of the POM ensemble at the surface. Assuming a power-law particle size spectrum at the surface, this model results in unimodal size distributions in the ocean interior. For the size-dependent sinking model, we present an analytic integral over depth and size that can explain regional variations of remineralisation length scales in response to regional patterns in trophodynamic state.

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