scholarly journals Indirect Effects of Microplastic-Contaminated Soils on Adjacent Soil Layers: Vertical Changes in Soil Physical Structure and Water Flow

2021 ◽  
Vol 9 ◽  
Author(s):  
Shin Woong Kim ◽  
Yun Liang ◽  
Tingting Zhao ◽  
Matthias C. Rillig
Keyword(s):  
Water Flow ◽  
Contaminated Soils ◽  
Soil Column ◽  
Physical Structure ◽  
Control Soil ◽  
Soil Layers ◽  
Polyethylene Films ◽  
Vertical Changes ◽  
Adjacent Soil ◽  
Physical Changes

Previous microplastic research under laboratory conditions has focused on microplastics that are homogeneously mixed into test media, in order to maximize test reproducibility and uniform bio-accessibility. Here we specifically focused on testing the idea that microplastics in soil could affect adjacent soil layers not containing microplastic themselves. We included two different microplastics (low-density polyethylene films and polyacrylonitrile fibers) and carried out a soil column test consisting of three different vertical layers (0–3 cm, top, control soil; 3–6 cm, middle, microplastic-containing soil; 6–9 cm, bottom, control soil). Our study shows that microplastic-containing soil layers can act as an anthropogenic barrier in the soil column, interrupting the vertical water flow. These changes directly affected the water content of adjacent layers, and changes in the proportion of soil aggregate sizes occurred for each depth of the soil columns. We also observed that these physical changes trigger changes in soil respiration, but do not translate to effects on enzyme activities. These results imply that the soil environment in non-contaminated parts of the soil can be altered by microplastic contamination in adjacent layers, as might occur for example during ploughing on agricultural fields. More generally, our results highlight the need to further examine effects of microplastic in experiments that do not treat this kind of pollution as uniformly distributed.

Root exposure to apple replant disease soil triggers local defense response and rhizoplane microbiome dysbiosis

2021 ◽  
Author(s):  
Alicia Balbín-Suárez ◽  
Samuel Jacquiod ◽  
Annmarie-Deetja Rohr ◽  
Benye Liu ◽  
Henryk Flachowsky ◽  
...  
Keyword(s):  
Gene Expression ◽  
Plant Defense ◽  
Defense Response ◽  
Soil Column ◽  
Soil Layer ◽  
Soil Microbiome ◽  
Control Soil ◽  
Apple Rootstocks ◽  
Apple Replant Disease ◽  
Replant Disease

Abstract A soil column split-root experiment was designed to investigate the ability of apple replant disease (ARD) causing agents to spread in soil. ‘M26’ apple rootstocks grew into a top layer of Control soil, followed by a barrier-free split-soil layer (Control soil/ARD soil). We observed a severely reduced root growth, concomitant with enhanced gene expression of phytoalexin biosynthetic genes and phytoalexin content in roots from ARD soil, indicating a pronounced local plant defense response. Amplicon sequencing (bacteria, archaea, fungi) revealed local shifts in diversity and composition of microorganisms in the rhizoplane of roots from ARD soil. An enrichment of OTUs affiliated to potential ARD fungal pathogens (Ilyonectria and Nectria sp.) and bacteria frequently associated with ARD (Streptomyces, Variovorax) was noted. In conclusion, our integrated study supports the idea of ARD being local and not spreading into surrounding soil, as only the roots in ARD soil were affected in terms of growth, phytoalexin biosynthetic gene expression, phytoalexin production, and altered microbiome structure. This study further reinforces the microbiological nature of ARD, being likely triggered by a disturbed soil microbiome enriched with low mobility ARD-causing agents that induce a strong plant defense and rhizoplane microbiome dysbiosis, concurring with root damage.

scholarly journals Temperate UV-Accelerated Weathering Cycle Combined with HT-GPC Analysis and Drop Point Testing for Determining the Environmental Instability of Polyethylene Films

Polymers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 2373
Author(s):  
Celine Moreira ◽  
Richard Lloyd ◽  
Gavin Hill ◽  
Florence Huynh ◽  
Ana Trufasila ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Outdoor Exposure ◽  
Accelerated Weathering ◽  
Polyethylene Films ◽  
Parallel Testing ◽  
Mapping Analysis ◽  
Environmental Instability ◽  
Weight Analysis ◽  
Physical Changes ◽  
Ir Spectroscopic

Polyethylene films are one of the most frequently used packaging materials in our society, due to their combination of strength and flexibility. An unintended consequence of this high use has been the ever-increasing accumulation of polyethylene films in the natural environment. Previous attempts to understand their deterioration have either focused on their durability using polymer analysis; or they have focused on changes occurring during outdoor exposure. Herein, this study combines those strategies into one, by studying the chemical and physical changes in the polyethylene structure in a laboratory using molecular weight and IR spectroscopic mapping analysis, combined with temperate UV-accelerated weathering cycles. This approach has been correlated to real-world outdoor exposure timeframes by parallel testing of the sample polyethylene films in Florida and France. The formation of polyethylene microparticles or polyethylene waxes is elucidated through comparison of drop point testing and molecular weight analysis.

scholarly journals Measuring thermal conductivity of soils under laboratory conditions.

1969 ◽  
Vol 17 (1) ◽  
pp. 71-79
Author(s):  
A.I. Golovanov
Keyword(s):  
Thermal Conductivity ◽  
Flow Velocity ◽  
Soil Sample ◽  
Water Flow ◽  
Coarse Sand ◽  
Conductivity Measurements ◽  
Soil Layers ◽  
The Real ◽  
Real Flow

Experiments were made to determine the influence of size of soil sample, convection and water flow on the determination of thermal conductivity of soils using a thin needle (0.05 cm radius, 8.5 cm in length) as the heating element and copper cylinders for sample containers. For measurements during a period of 100 seconds the diameter of the sample must be at least 4 cm and to avoid any influence of convection measurements should not exceed 100 seconds. When heating elements are placed horizontally to measure simultaneously the thermal conductivity of different soil layers they should be placed at least 10 cm apart. Thermal conductivity measurements could be used to determine flow velocities of water in coarse sand samples provided that the real flow velocity was highev than 0.35 cm/ min. (Abstract retrieved from CAB Abstracts by CABI’s permission)

Roles of clay layers in rainfall-runoff processes in a serpentinite headwater catchment

2020 ◽  
Author(s):  
Takahiko Yoshino ◽  
Shin'ya Katsura
Keyword(s):  
Water Flow ◽  
Groundwater Level ◽  
Mineral Soil ◽  
High Water ◽  
Organic Soil ◽  
Rainfall Runoff ◽  
Soil Layers ◽  
Clay Layers ◽  
Headwater Catchment

<p>Rainfall-runoff processes in a headwater catchment have been typically explained by water flow in permeable soil layers (comprised of organic soil layers and mineral soil layers produced by weathering of bedrock) overlying less permeable layers (i.e., bedrock). In a catchment where mineral soils are characterized by clayey materials (e.g., mudstone, slate, and serpentine catchment), it is possible that mineral soil layers function substantially as less permeable layers because of a low permeability of clayey materials. However, roles of clay layers in rainfall-runoff processes in such a headwater catchment are not fully understood. In this study, we conducted detailed hydrological, hydrochemical, and thermal observations in a serpentinite headwater catchment (2.12 ha) in Hokkaido, Northern Japan, where mineral soil layers consisting of thick clay layers (thickness: approximately 1.5 m) produced by weathering of the serpentinite bedrock underlies organic soil layers (thickness: approximately 0.4 m). Saturated hydraulic conductivity (Ks) and water retention curve of these two layers were also measured in a laboratory. The observation results demonstrated that groundwater was formed perennially in the organic soil layers and clay layers. The groundwater level within the organic soil layers and specific discharge of the catchment showed rapid and flashy change in response to rainfall. In contrast, the groundwater level within the clay layers showed slow and small change. Temperature of the groundwater and stream water suggested that water from the depth of the organic soil layers contributed to streamflow. The electric conductivity (EC) of the groundwater in the clay layers was very high, ranging from 321 to 380 µS cmˉ¹. On the other hand, the EC of soil water (unsaturated water stored in the organic soil layers) was relatively low, ranging from 98 to 214 µS cmˉ¹. Hydrograph separation using EC showed that contribution of water emerging from the clay layers to the total streamflow ranged from 31 to 76% in low to high flow periods. Temporal variation in the total head, measured using tensiometers installed at four depths at the ridge of the catchment, indicated that in wet periods when the groundwater level in the organic soil layers was high, water flow from the organic soil layers to the clay layers occurred, whereas, in dry periods, water flow from the clay layers into the organic soil layers occurred. The laboratory measurements showed that the organic soil layers had high Ks (10ˉ² cm sˉ¹) and low water-holding capacity, whereas the clay layers had low Ks (10ˉ⁴ cm sˉ¹) and high water-holding capacity. It can be concluded from these results that clay layers play two roles: (1) forming perched groundwater table and lateral flow on the clay layers (the role of less permeable layers) and (2) supplying water into the organic soil layers in the dry periods (the role of water supplier).</p>

Tomographic Evaluation of Air and Water Flow Patterns in Soil Column

2000 ◽  
Vol 23 (4) ◽  
pp. 413 ◽  
Author(s):  
RC Chaney ◽  
KR Demars ◽  
RCK Wong ◽  
R Wibowo
Keyword(s):  
Water Flow ◽  
Soil Column ◽  
Flow Patterns

scholarly journals Biological Low-pH Mn(II) Oxidation in a Manganese Deposit Influenced by Metal-Rich Groundwater

2016 ◽  
Vol 82 (10) ◽  
pp. 3009-3021 ◽  
Author(s):  
Tsing Bohu ◽  
Denise M. Akob ◽  
Michael Abratis ◽  
Cassandre S. Lazar ◽  
Kirsten Küsel
Keyword(s):  
Biogeochemical Cycling ◽  
Mining Area ◽  
Low Ph ◽  
Acidic Ph ◽  
Soil Layers ◽  
Content Type ◽  
Mn Oxide ◽  
Geochemical Significance ◽  
Adjacent Soil ◽  
Abiotic Controls

ABSTRACTThe mechanisms, key organisms, and geochemical significance of biological low-pH Mn(II) oxidation are largely unexplored. Here, we investigated the structure of indigenous Mn(II)-oxidizing microbial communities in a secondary subsurface Mn oxide deposit influenced by acidic (pH 4.8) metal-rich groundwater in a former uranium mining area. Microbial diversity was highest in the Mn deposit compared to the adjacent soil layers and included the majority of known Mn(II)-oxidizing bacteria (MOB) and two genera of known Mn(II)-oxidizing fungi (MOF). Electron X-ray microanalysis showed that romanechite [(Ba,H2O)2(Mn4+,Mn3+)5O10] was conspicuously enriched in the deposit. Canonical correspondence analysis revealed that certain fungal, bacterial, and archaeal groups were firmly associated with the autochthonous Mn oxides. Eight MOB within theProteobacteria,Actinobacteria, andBacteroidetesand one MOF strain belonging toAscomycotawere isolated at pH 5.5 or 7.2 from the acidic Mn deposit. Soil-groundwater microcosms demonstrated 2.5-fold-faster Mn(II) depletion in the Mn deposit than adjacent soil layers. No depletion was observed in the abiotic controls, suggesting that biological contribution is the main driver for Mn(II) oxidation at low pH. The composition and species specificity of the native low-pH Mn(II) oxidizers were highly adapted toin situconditions, and these organisms may play a central role in the fundamental biogeochemical processes (e.g., metal natural attenuation) occurring in the acidic, oligotrophic, and metalliferous subsoil ecosystems.IMPORTANCEThis study provides multiple lines of evidence to show that microbes are the main drivers of Mn(II) oxidation even at acidic pH, offering new insights into Mn biogeochemical cycling. A distinct, highly adapted microbial community inhabits acidic, oligotrophic Mn deposits and mediates biological Mn oxidation. These data highlight the importance of biological processes for Mn biogeochemical cycling and show the potential for new bioremediation strategies aimed at enhancing biological Mn oxidation in low-pH environments for contaminant mitigation.

scholarly journals Leaching of microplastics by preferential flow in earthworm (Lumbricus terrestris) burrows

2019 ◽  
Vol 16 (1) ◽  
pp. 31 ◽  
Author(s):  
Miao Yu ◽  
Martine van der Ploeg ◽  
Esperanza Huerta Lwanga ◽  
Xiaomei Yang ◽  
Shaoliang Zhang ◽  
...  
Keyword(s):  
Preferential Flow ◽  
Soil Depth ◽  
Soil Column ◽  
Soil Surface ◽  
Lumbricus Terrestris ◽  
Soil Samples ◽  
Average Weight ◽  
Soil Layers ◽  
Groundwater Systems ◽  
Set Up

Environmental contextMicroplastics found in soil pose several potential environmental risks. This study shows that microplastics on the soil surface can be ingested by earthworms and transported to the lower soil layers. In this way, microplastics may enter the food chain and find their way into groundwater systems, especially in cases where the water table is shallow. AbstractIn the current study, we examine how the activities of earthworms (Lumbricus terrestris) affect microplastic (MP) distribution and concentration in soil, with a focus on low density polyethylene (LDPE). We also want to determine if MPs can be flushed out with water. We used a laboratory sandy soil column (polyvinyl chloride tube) experimental set-up and tested five different treatments: (1) treatment with just soil (control) to check if the saturated conductivity (Ksat) could be impacted by MP, (2) treatment with MP, (3) treatment with MP and litter, (4) treatment with earthworms and litter as a second control for treatment 5 and (5) treatment with MPs, earthworms and litter. Each treatment consisted of eight replicates. For the treatments with MP, the concentration of MP added at the start of the experiment was 7% by weight (3.97g, polyethylene, 50% 1mm–250µm, 30% 250µm–150µm and 20% <150µm) based on 52.78g of dry litter from Populus nigra. In the treatments using earthworms, two adult earthworms, with an initial average weight of (7.14±0.26) g, were placed in each column. Results showed that LDPE particles could be introduced into the soil by the earthworms. MP particles were detected in each soil sample and within different soil layers for the earthworm treatments. Earthworms showed a tendency to transport the smaller MP particles and that the amount of MPs in size class <250μm increased in soil samples with increasing soil depth in comparison to the other size classes. After leaching, MPs were only detected in the leachate from the treatments with the earthworms, and the MP had similar size distributions as the soil samples in the 40–50cm layer of the treatment with MP, earthworms and litter. The results of this study clearly show that biogenic activities can mobilise MP transport from the surface into the soil and even be leached into drainage. It is highly likely that biogenic activities constitute a potential pathway for MPs to be transported into soil and groundwater.

scholarly journals Assimilation of surface soil moisture into a multilayer soil model: design and evaluation at local scale

2014 ◽  
Vol 18 (2) ◽  
pp. 673-689 ◽  
Author(s):  
M. Parrens ◽  
J.-F. Mahfouf ◽  
A. L. Barbu ◽  
J.-C. Calvet
Keyword(s):  
Soil Moisture ◽  
Land Surface ◽  
Surface Soil ◽  
Soil Column ◽  
Cumulative Distribution ◽  
Surface Soil Moisture ◽  
Deep Soil ◽  
Background Error ◽  
Soil Layers ◽  
Diffusion Scheme

Abstract. Land surface models (LSM) have improved considerably in the last two decades. In this study, the Interactions between Surface, Biosphere, and Atmosphere (ISBA) LSM soil diffusion scheme is used (with 11 soil layers represented). A simplified extended Kalman filter (SEKF) allows ground observations of surface soil moisture (SSM) to be assimilated in the multilayer LSM in order to constrain deep soil moisture. In parallel, the same simulations are performed using the ISBA LSM with 2 soil layers (a thin surface layer and a bulk reservoir). Simulations are performed over a 3 yr period (2003–2005) for a bare soil field in southwestern France, at the SMOSREX (Surface Monitoring Of the Soil Reservoir Experiment) site. Analyzed soil moisture values correlate better with soil moisture observations when the ISBA LSM soil diffusion scheme is used. The Kalman gain is greater from the surface to 45 cm than below this limit. For dry periods, corrections introduced by the assimilation scheme mainly affect the first 15 cm of soil whereas weaker corrections impact the total soil column for wet periods. Such seasonal corrections cannot be described by the two-layer ISBA LSM. Sensitivity studies performed with the multilayer LSM show improved results when SSM (0–6 cm) is assimilated into the second layer (1–5 cm) than into the first layer (0–1 cm). The introduction of vertical correlations in the background error covariance matrix is also encouraging. Using a yearly cumulative distribution function (CDF)-matching scheme for bias correction instead of matching over the three years permits the seasonal variability of the soil moisture content to be better transcribed. An assimilation experiment has also been performed by forcing ISBA-DF (diffusion scheme) with a local forcing, setting precipitation to zero. This experiment shows the benefit of the SSM assimilation for correcting inaccurate atmospheric forcing.

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