Model Soil System Research Articles

Simultaneous Imaging of Temperature and Oxygen by Utilizing Thermally Activated Delayed Fluorescence and Phosphorescence of a Single Indicator.

Chemical gradients are essential in biological systems, affecting processes like microbial activity in soils and nutrient cycling. Traditional tools, such as microsensors, offer high-resolution data but are limited to one-dimensional measurements. Planar optodes allow for two-dimensional (2D) and three-dimensional (3D) chemical imaging but are often sensitive to temperature changes. This study presents an advanced dual-emission optical sensor that simultaneously measures temperature and oxygen using a modified platinum(II) meso-tetrakis(3,5-ditert-butylphenyl)-tetra(2-tert-butyl-1,4-naphthoquinono)porphyrin. The ratio between thermally activated delayed fluorescence and phosphorescence was optimized by modifying platinum(II) naphthoquinonoporphyrin with tert-butyl groups which simultaneously improved solubility in apolar solvents and polymer matrix (polystyrene). This dual-function sensor enables two-parameter chemical imaging with a consumer-grade RGB camera or a hyperspectral camera. We demonstrated 2D visualization of temperature and oxygen distribution in a model soil system. The RGB camera provided rapid and cost-effective imaging, while the hyperspectral camera offered more detailed spectral information despite some limitations. Our findings revealed the formation of a stable temperature gradient and oxygen depletion, driven by water content and temperature-sensitive microbial activity. This dual O2/T sensor, with further potential improvements, shows considerable promise for advanced multiparameter sensing in complex biological and environmental studies, providing deeper insights into dynamic microenvironments.

Mid-Infrared Variable Selection for Soil Organic Matter Fractions Based on Soil Model Systems and Permutation Importance Algorithm.

In this research, an attempt was made to classify soil samples according to the different fractions of soil organic matter (SOM) using model systems in which the ratio of the fractions of SOM is chemically mimicked. A mixture of starch and nicotinamide was used for the labile organic matter model, while a standard of humic acid was used for the stabile organic matter. Changing the threshold value in the selected ranges after a permutation importance algorithm is conducted using train models and test data set, a list of selected important wavelengths and their importance scores were obtained. Three regions for the classification of soil fractions within the estimated probability density function are most prominent: 800-1200 cm-1, 0.48-0.55; 1800-2000 cm-1, 0.52-0.62; and 2500-3200 cm-1, 0.48-0.62, where the first component represents the spectral range while the second component covers the range of the importance score. Obtained wavelength ranges indicate the importance of the aliphatic stretching and bending vibration region, as well as the total soil reflectance (mineral content) for the characterization of organic matter fractions. A comparative evaluation with literature data found that the obtained wavelengths have a potential for application in methods of proximal and remote detection/calibration of existing and development of new sensors for Advanced Spaceborne Thermal Emission and Reflection Radiometer satellites, specifically in the shortwave infrared and thermal infrared ranges.

Grain-size dependence of water retention in a model aggregated soil

We experimentally examined the amount of water retention in a model soil composed of aggregated glass beads. The model soil was characterized by two size parameters: size of aggregates D and size of monomer particles (composing aggregates) d. In the experiment, water was sprinkled on the model-soil system that has an open top surface and drainable sieve bottom. When the sprinkled water amount exceeded a threshold (retainable limit), draining flux balanced with the sprinkled flux. The weight variations of retained and drained water were measured to confirm this balanced (steady) state and quantify the retained water. We defined the weight of the retained water in this steady state as W0 and examined the relationship among W0,d and D. As a result, it was revealed that W0 increases as d decreases simply due to the capillary effects. Regarding D dependence, it turned out that W0 becomes the maximum around D≃500μm. The value of D maximizing water retention is determined by the void formation due to the aggregated structure, capillary effect, and gravity.

Development of a Hydrodynamic Model for Regulating Water Drainage of Reservoir and Water Resources Management, Lamtakong Watershed of Thailand

The goal of this research was to develop a hydrodynamic model (HDD-M) for water resource management in the Lamtakong Watershed (LTKW), as well as to simulate three scenarios: 1) Current land use conditions in 2021, 2) Forecasting predicted land-use changes in 2024, and 3) Water drainage regulation of the Lamtakong Reservoir (LTKR) for water resource management in 2024. The Soil and Water Assessment Tool (SWAT) model and Geographic Information System (GIS) program were used to estimate and simulate the amount of Surface Runoff (S), Sediment Yield (SED), Carbonaceous Biochemical Oxygen Demand concentration (CBOD), and Nitrate concentration (NO3) based on a comparison of simulated and observed data. In scenario 1, the S, SED, CBOD, and NO3 were calculated to be 238.44 million cubic meters (MCM), 840,613.68 tons per year, 2.38 mg/L, and 7.36 mg/L, respectively. In the second scenario, the S decreased to 14.75 MCM, whereas SED, CBOD, and NO3 increased to 56,757.48 tons, 0.56 mg/L, and 0.79 mg/L, respectively, when compared to scenario 1, (Scenario 2). Scenario 3 demonstrated that during the dry season of November to June, the standards of surface water were CBOD and NO3, and that increasing LTKR drainage can help prevent the deterioration of water yields. As a result, the HDD-M, which includes the reservoir's controlling water drainage, may need to be considered to satisfy water resource management goals.

Groundwater recharge estimation and potential recharge mapping in the Afram Plains of Ghana using SWAT and remote sensing techniques

The Afram Plains watershed is one of the major watersheds located at the lower part of the Volta Basin in Ghana with high groundwater usage. Dependency on groundwater is a fast-growing concern in the plains due to the unreliable supply of surface water. This has put the groundwater resources under intense pressure and has necessitated the need for sustainable management of the groundwater resources. This study aimed to estimate the recharge, spatial distribution, and potential recharge zones of groundwater at different scales in the Afram Plains area using the Soil and Water Assessment Tool (SWAT) model and Geography Information System (GIS) approach. The SWAT model was set up (1983–2016), calibrated (1983–1990) and validated (1991–1997) using digital elevation model, soil, land use, climate datasets, and discharge data. The GIS approach was used to produce thematic maps for eight contributing factors; rainfall, elevation, land cover land use, lineaments, drainage, geology, soil and slope for mapping the recharge zones. The results showed that about 1.65% (19.3 mm) of the SWAT simulated mean annual rainfall (1176.9 mm) is converted into groundwater recharge in the watershed. The potential recharge zones categorized as very poor, poor, moderate and high zones have area coverages of 0.58% (20.8 km2), 22.4% (798 km2), 60.9% (2169 km2), and 16.2% (576 km2), respectively. The potential recharge zones after validation over boreholes and wells data indicated that the Afram Plains area is dominated by the moderate potential zone.

Application of meteorological element combination-driven SWAT model based on meteorological datasets in alpine basin

Abstract Thus far, reanalysis-based meteorological products have drawn little attention to the influence of meteorological elements of products on hydrological modeling. This study aims to evaluate the hydrological application potential of the precipitation, temperature, and solar radiation of the China Meteorological Assimilation Driving Datasets for the Soil and Water Assessment Tool (SWAT) model (CMADS) and Climate Forecast System Reanalysis (CFSR) in an alpine basin. The precipitation, temperature, and solar radiation of the gauge-observed meteorological dataset (GD), CFSR, and CMADS were cross-combined, and 20 scenarios were constructed to drive the SWAT model. From the comprehensive comparisons of all scenarios, we drew the following conclusions: (1) among the three meteorological elements, precipitation has the greatest impact on the simulation results, and using GD precipitation from sparse stations yielded better performance than CMADS and CFSR; (2) although the SWAT modeling driven by CMADS and CFSR performed poorly, with CMADS underestimation and CFSR overestimation, the temperature and solar radiation of CMADS and CFSR can be an alternative data source for streamflow simulation; (3) models using GD precipitation, CFSR temperature, and CFSR solar radiation as input yielded the best performance in streamflow simulation, suggesting that these data sources can be applied to this data-scarce alpine region.

Biological control of Listeria monocytogenes in soil model systems by Enterococcus mundtii strains expressing mundticin KS production

The agricultural practices applied in pre-harvest greatly influence the presence and the levels of microorganisms in fresh produce. Among these, Listeria monocytogenes represents one of the most lethal foodborne pathogens associated with vegetables. The main hypothesis of this work is that bacteriocin producer Enterococcus mundtii strains can be effective against L. monocytogenes in soil. To this purpose, bacteriocin production by E. mundtii WFE3, WFE20 and WFE31, three strains showing a strong bacteriocin activity in terms of inhibitory power and inhibition spectra, was evaluated in sterile extracts from agricultural soil and peat moss, in organic nutrient solution (ONS) and mineral nutrient solution (MNS). ONS supernatants from E. mundtii WFE3 showed the highest inhibition of the strain L. monocytogenes ATCC 19114. Thus, this strain [104 colony forming units (CFU) g−1 dw] was co-inoculated with E. mundtii WFE3 (106 CFU g−1 dw) in the sterile extracts and solutions. A general increase of E. mundtii cell densities and the contemporary decrease of the levels of L. monocytogenes were observed, particularly in ONS. This solution was used to amend autoclaved soil to test in vivo the competition among bacteriocin producer and sensitive strain. L. monocytogenes decreased of almost 1.5 log CFU when E. mundtii was added to soil. The test was also carried out with basil plants showing that the anti-Listeria effect of E. mundtii is exerted during the very first days from inoculation. After 2 days, the levels of NO3−-N in soil increased for all trials, while the concentrations of ammonium and α-amino N decreased. The lowest concentrations of NH4+-N were found in presence of L. monocytogenes. At harvest, the plants were analysed for the presence of E. mundtii and L. monocytogenes, but none of the two bacterial species deliberately added to soil was transferred to plants. Although a biocontrol based on bacteriocin application in soil has to be properly set, this study provides useful insight for the future development of chemical-free agricultural strategies.

STABILITY OF PHYTOCENOSES IN OIL-PRODUCING REGIONS

The only real way to deal with the consequences of oil and oil products spills is a complex of works, including mechanical or physico-chemical removal of spilled oil products with subsequent purification of the remaining oil in the soil by biological methods using phytoremediation with oil-oxidizing plants. One of the stages of the study of hydrocarbon-oxidizing plants before their introduction into the environment for remediation of contaminated sites is the study of the process of degradation of pollutants in model soil systems. Model experiments on cleaning and restoration of soils after their contamination with oil and oil products by plant biomass were studied. Oil samples from the Tengiz field were taken. During the experiments, the indicator of the total amount of biomass, as well as the oil content in the soil, was controlled. To correctly assess the participation of plant raw materials in the destruction of oil, experiments were carried out using non-sterile soils. Among other plant cultures, the most degrading activity was shown by plant cultures of the genus Fabaceae, which led to an increase in growth in the soil environment by an average of 7 sm in 20 days. This is observed for plants with oil concentrations of 3, 6 and 9 g. The results of physical and chemical analyses of phytoremediation products of crude oil, petroleum products and individual aromatic hydrocarbons can be important in microbiological and chemical studies with geobotanical indicators that allow analyzing the mechanism of action of biomass in the process of phytoremediation in the disposal of oil waste that pollutes the environment. The available data on the effect of petroleum hydrocarbons on plants are very contradictory. The species diversity of plants capable of growing on oil-contaminated soils has not been sufficiently studied. Knowledge of the degree of resistance of plants to hydrocarbon pollution is necessary to address issues related, on the one hand, to the possibility of their cultivation on contaminated soil, and on the other - to use for the restoration of disturbed soil fertility. In connection with the above, it is of great scientific and practical interest to study the effect of various doses of oil on changes in vegetation cover, soil properties and assessment of their phytotoxicity, which together determines the relevance of the stated topic.

An accurate analysis of lightning overvoltages in mixed overhead-cable lines

An accurate investigation of lightning overvoltages on a typical mixed overhead-cable line is performed. The recently developed extended transmission line (TL) approach, frequency-dependent (FD) soil model and FD grounding system modeling method are also reviewed. The wave propagation characteristics of an overhead and a cable in frequency domain are studied using classical and extended TL approaches. Moreover, transient simulations using Numerical Laplace Transform (NLT) are carried out with different FD soil parameters and FD grounding behavior, and the influences of FD characteristics on the transient cable sheath voltages are made clear.

Modelling rainfall runoff for identification of suitable water harvesting sites in Dawe River watershed, Wabe Shebelle River basin, Ethiopia

Scarcity of freshwater is one of the major issues which hinders nourishment in large portion of the countries like Ethio-pia. The communities in the Dawe River watershed are facing acute water shortage where water harvesting is vital means of survival. The purpose of this study was to identify optimal water harvesting areas by considering socioeconomic and biophysical factors. This was performed through the integration of soil and water assessment tool (SWAT) model, remote sensing (RS) and Geographic Information System (GIS) technique based on multi-criteria evaluation (MCE). The parame-ters used for the selection of optimal sites for rainwater harvesting were surface runoff, soil texture, land use land cover, slope gradient and stakeholders’ priority. Rainfall data was acquired from the neighbouring weather stations while infor-mation about the soil was attained from laboratory analysis using pipette method. Runoff depth was estimated using SWAT model. The statistical performance of the model in estimating the runoff was revealed with coefficient of determination (R2) of 0.81 and Nash–Sutcliffe Efficiency (NSE) of 0.76 for monthly calibration and R2 of 0.79 and NSE of 0.72 for monthly validation periods. The result implied that there's adequate runoff water to be conserved. Combination of hydrological model with GIS and RS was found to be a vital tool in estimating rainfall runoff and mapping suitable water harvest home sites.

The relationship between properties of plant-based biochars and sorption of Cd(II), Pb(II) and Zn(II) in soil model systems

Plant based biochars are proposed as soil amendments to immobilize potentially toxic trace elements (PTEs), such as Cd(II), Pb(II) and Zn(II) and aid in soil restoration. However, the sorption capacity of biochar for these elements can vary widely depending on biochar nature and metal properties. Currently, there is no clear methodology to pre-screen biochars for their suitability as adsorbents for these elements. Therefore, to facilitate biochar selection for application in soil restoration, this study explored the relationships between the physico-chemical properties of five plant-based biochars and their capacity to immobilize Cd(II), Pb(II) and Zn(II). Batch experiments using synthetic soil pore water were used to assess the sorption of these elements. The sorption isotherms described by the Hill model indicated that PTE sorption capacity followed the order Pb(II) > Cd(II) >Zn(II) regardless of biochar type in mono-element systems. Preferential sorption of Pb(II) limited the immobilization of Cd(II) and Zn(II) in multi-element systems. ATR-FTIR and SEM-EDX spectroscopy studies indicated that Cd(II) and Pb(II) sorption was mediated by complexation with carboxylic groups, cation–π interactions and precipitation with phosphates and silicates, while Zn(II) sorption occurred mainly by complexation with phenolic groups and precipitation with phosphates. A high correlation (>0.8) between Electrical Conductivity, Cation Exchange Capacity, pH and sorption capacity was identified for all metals tested, highlighting the electrostatic nature of the sorption mechanisms involved. Biochars derived from herbaceous feedstock were better candidates for remediation of soil polluted with Cd(II), Pb(II) and Zn(II), rather than wood-derived biochar. Overall, this study provides evidence of the direct relationship between specific properties of plant-based biochars (pH and EC) and their suitability as adsorbents for some PTEs in soil systems.

Investigate the Applicability of CMADS and CFSR Reanalysis in Northeast China

Reanalysis datasets can provide alternative and complementary meteorological data sources for hydrological studies or other scientific studies in regions with few gauge stations. This study evaluated the accuracy of two reanalysis datasets, the China Meteorological Assimilation Driving Datasets for the Soil and Water Assessment Tool (SWAT) model (CMADS) and Climate Forecast System Reanalysis (CFSR), against gauge observations (OBS) by using interpolation software and statistical indicators in Northeast China (NEC), as well as their annual average spatial and monthly average distributions. The reliability and applicability of the two reanalysis datasets were assessed as inputs in a hydrological model (SWAT) for runoff simulation in the Hunhe River Basin. Statistical results reveal that CMADS performed better than CFSR for precipitation and temperature in NEC with the indicators closer to optimal values (the ratio of standard deviations of precipitation and maximum/minimum temperature from CMADS were 0.92, 1.01, and 0.995, respectively, while that from CFSR were 0.79, 1.07, and 0.897, respectively). Hydrological modelling results showed that CMADS + SWAT and OBS + SWAT performed far better than CFSR + SWAT on runoff simulations. The Nash‒Sutcliffe efficiency (NSE) of CMADS + SWAT and OBS + SWAT ranged from 0.54 to 0.95, while that of CFSR + SWAT ranged from −0.07 to 0.85, exhibiting poor performance. The CMADS reanalysis dataset is more accurate than CFSR in NEC and is a suitable input for hydrological simulations.

Mechanism of nutrition activity of a microgranule fertilizer fortified with proteins

BackgroundA microgranule fertilizer was designed for localized fertilization of soil with controlled release of nutrients. The microgranule matrix was fortified with proteins, which were obtained from food industry byproducts or waste, i.e., whey protein from milk serum, soy protein from soy isolate and egg white protein from chicken egg white powder. The mechanism of the protein decomposition and migration of micro and macromolecule compounds through two different model soil systems was investigated. The potential of the protein fortified fertilizer for localized fertilization of the potted maize seeds was evaluated.ResultsThe study revealed that proteins slowly diffused through soil with simultaneous degradation, which was accompanied with release of ammonia ions. The highest concentration of proteins and degradation products was found in a close vicinity of the microgranule. The microgranules were used as a local fertilizer for maize seeds in the pot experiments. The experiments confirmed statistically significant improvement in root density of maize plant compared to control group.ConclusionsByproducts or waste of food industry, such as the milk serum and soy can be used as a source of proteins that degrade in soil without a pretreatment. The degradation is accompanied with formation of ammonium ions, which can be utilized by plants as a nitrogen source. The fertilizer microgranule should be placed in a close vicinity to the plant seed, since the maximum of the protein concentration and ammonia ions is reached at a very close distance from the microgranule.

Substrate quality and concentration control decomposition and microbial strategies in a model soil system

Soil carbon models typically scale decomposition linearly with soil carbon (C) concentration, but this linear relationship has not been experimentally verified. Here we investigated the underlying biogeochemical mechanisms controlling the relationships between soil C concentration and decomposition rates. We incubated a soil/sand mixture with increasing amounts of finely ground plant residue in the laboratory at constant temperature and moisture for 63 days. The plant residues were rye (Secale cereale, C/N ratio of 23) and wheat straw (Triticum spp., C/N ratio of 109) at seven soil C concentrations ranging from 0.38 to 2.99%. We measured soil respiration, dissolved organic carbon (DOC) concentrations, microbial biomass, and potential enzyme activities over the course of the incubation. Rye, which had higher N and DOC contents, lost 6 to 8 times more C as CO2 compared to wheat residue. Under rye and wheat amendment, absolute C losses as CO2 (calculated per g dry soil) increased linearly with C concentration while relative C losses as CO2 (expressed as percent of initial C) increased with C concentration following a quadratic function. In low C concentration treatments (0.38–0.79% OC), DOC decreased gradually from day 3 to day 63, microbial C increased towards the end in the rye treatment or decreased only slightly with straw amendment, and microbes invested in general enzymes such as proteases and oxidative enzymes. At increasing C levels, enzyme activity shifted to degrading cellulose after 15 days and degrading microbial necromass (e.g. chitin) after 63 days. At the highest C concentrations (2.99% OC), microbial biomass peaked early in the incubation and remained high in the rye treatment and decreased only slightly in the wheat treatment. While wheat lost C as CO2 constantly at all C concentrations, respiration dynamics in the rye treatment strongly depended on C concentration. Our results indicate that litter quality and C concentration regulate enzyme activities, DOC concentrations, and microbial respiration. The potential for non-linear relationships between soil C concentration and decomposition may need to be considered in soil C models and soil C sequestration management approaches.

Molecular sequestration mechanisms of heavy metals by iron oxides in soils using synchrotronbased techniques: A review

Iron oxides, widely distributed in soils, have large specific surface areas and strong affinity to heavy metals, and thus play a significant role in the transformation of heavy metals in soils. To understand the environmental behaviors of heavy metals and assess their bioavailability in contaminated soils, it is important to investigate the sequestration mechanisms of heavy metals by iron oxides. The traditional methods, including adsorption modeling and chemical extraction fractionation, have obvious limitations and provide little information on the sequestration mechanisms of heavy metal by iron oxides at the molecular level. The application of synchrotron-based techniques in environmental soil science has greatly enhanced the molecular-level understanding of the immobilization mechanisms of heavy metals by iron oxides under various environmental conditions. Here, we reviewed the development of synchrotron-based techniques and summarized the molecular sequestration mechanisms of heavy metals by iron oxides in model and real soil systems under various environmental factors. The future development of synchrotron-based techniques and their applications were prospected.

Prediction of sedimentation in reservoirs by combining catchment based model and stream based model with limited data

Estimation of sedimentation in reservoirs helps in the management and design of the reservoir׳s useful capacity. This research was done on the Awash River basin at the Koka Dam Reservoir in Ethiopia. The method applied was the loose integration of the Soil and Water Assessment Tool (SWAT) model and Hydrologic Engineering Center-River Analysis System (HEC-RAS) model for the estimation of the sediment load reaching the reservoir. The SWAT model was used for the estimation of erosion at the catchment level, and the HEC-RAS model was applied to estimate the sediment transport in the river channel. The implemented method allows sedimentation in the floodplains and bed shear stress to be considered in the sediment modeling, which cannot be considered in the SWAT model. In addition, the river cross sectional properties and the hydrodynamic processes in the rivers were considered in the modeling process. The data used in this study are a combination of i) observed data collected by government agencies, ii) data available online in data repositories, and iii) data extracted from remote sensing in the Shuttle Radar Topographic Mission (SRTM) Digital Elevation Model (DEM). The calibration and validation of the SWAT model was done by using Sequential Uncertainty Fitting (SUIF-2) calibration and validation tools. The HEC-RAS model was calibrated by adjusting the roughness factor. The output from the integrated approaches gives better estimates of flow and sediment near the inlet to the reservoir, with coefficients of determination of 0.85 and 0.67, respectively, and Nash Sutcliffe coefficients of model fit efficiency of 0.90 and 0.62, respectively, for daily simulations.

Microbiological Oxidation of High Viscosity Bitumen in Soil

This paper presents the results of an investigation of microbiological oxidation in the model soil system of high viscosity bitumen from the Bayan-Erkhet deposit (Mongolia) with a high content of heteroelements. It is shown that bitumen, being a mixture of high molecular weight components, has no inhibitory effect on the indigenous soil microflora. Its active growth in the presence of oil products starts without adaptation and lasts for a good part of experiment resulting in 15‒30 fold excess of microorganisms over its reference number. The enzymatic activity of the contaminated soil increases by a factor of 1.5‒2.0, which indicates an assimilation of various hydrocarbon compounds. The weight analysis revealed that the biodegradation of oil products after 180 days of the experiment was 50% of the initial contamination at initial waste oil concentration 50 g/kg (5%). The analysis by IR spectroscopy revealed an accumulation of oxygen-containing compounds which are intermediate products of bio-oxidation of bitumen components. The method of chromatography-mass spectrometry (GC-MS) revealed the ability of aboriginal soil microflora to mineralize virtually all hydrocarbons contained in the bitumen under study. Their biodegradation ranges from 18 to 97%. It was shown by the GC-MS method that high-molecular heteroatomic components of bitumen (resins and asphaltenes) also undergo a microbial degradation, since their molecular structure changed after the destruction. Thus, the number of structural units in a hypothetical molecule and that of heteroatoms increased due to the high content of oxygen-containing structures. In addition, the ratio of hydrocarbons (oils), resins, and asphaltenes contained in the sample is also changed.

Effects of organic matter coatings on the mobility of goethite colloids in model sand and undisturbed soil

SummaryThe mobility of goethite (OMCG) colloids coated with organic matter was studied in goethite‐coated quartz sand and in undisturbed subsoil rich in natural coatings of iron oxide. Classic Derjaguin–Landau–Verwey–Overbeek (DLVO) interactions and DLVO extended by Lewis acid–base parameters (XDLVO) were estimated between colloids and goethite‐coated sand from zeta potentials and sessile drop contact angles. The OMCG colloids were retained completely in goethite‐coated sand, whereas preconditioning of the solid matrix with dissolved organic matter (DOM) enabled subsequent colloid transport. Zeta potential values showed that goethite‐coated sand was modified strongly by DOM preconditioning. The DLVO and XDLVO interactions were estimated for the pairs of OMCG colloids and for (i) quartz, (ii) goethite and (iii) organic matter‐coated goethite. Both DLVO approaches were able to predict general trends of colloid breakthrough. An exception was the XDLVO interaction for combination (iii), which showed short‐distance (<1.3 nm) repulsive interactions that were inconsistent with breakthrough behaviour. Analogous to OMCG colloid transport in the sand, DOM preconditioning was also the prerequisite for OMCG colloid transport in undisturbed subsoil. Total colloid breakthrough in the soil was less than in the sand, probably because of straining in pore throats and retention at air–water interfaces. We concluded that the DLVO and XDLVO approaches were in general capable of predicting trends of OMCG colloid mobility in goethite‐coated sand. We concluded further that the basic principles of OMCG colloid transport were transferrable from the simplified model system to the more complex natural system despite considerable differences in surface properties, pore structure and water content.Highlights How will organic matter (OM) coatings on the solid matrix affect mobility of iron oxide colloids? Effect of OM on mobility was assessed in simple model soil systems and in undisturbed soil. OM coatings modify properties of the solid matrix surface and are a prerequisite for colloid transport. Balances between OM transport, coating formation and decomposition control colloid mobility.

Soil geochemical factors regulate Cd accumulation by metal hyperaccumulating Noccaea caerulescens (J. Presl & C. Presl) F.K. Mey in field-contaminated soils

Cadmium contamination in soil is a substantial global problem, and of significant concern due to high food-chain transfer. Cadmium hyperaccumulators are of particular interest because of their ability to tolerate and take up significant amounts of heavy metal pollution from soils. One particular plant, Noccaea caerulescens (formerly, Thlaspi caerulescens), has been extensively studied in terms of its capacity to accumulate heavy metals (specifically Zn and Cd), though these studies have primarily utilized hydroponic and metal-spiked model soil systems. We studied Cd and nutrient uptake by two N. caerulescens ecotypes, Prayon (Zn-only hyperaccumulator) and Ganges (Zn- and Cd-hyperaccumulator) in four long-term field-contaminated soils. Our data suggest that individual soil properties such as total soil Cd, Zn:Cd molar ratio, or soil pH do not accurately predict Cd uptake by hyperaccumulating plants. Additionally, total Cd uptake by the hyperaccumulating Ganges ecotype was substantially less than its physiological capacity, which is likely due to Cd-containing solid phases (primarily iron oxides) and pH that play an important role in regulating and limiting Cd solubility. Increased P accumulation in the Ganges leaves, and greater plant Fe accumulation from Cd-containing soils suggests that rhizosphere alterations via proton, and potentially organic acid, secretion may also play a role in nutrient and Cd acquisition by the plant roots. The current study highlights the role that soil geochemical factors play in influencing Cd uptake by hyperaccumulating plants. While these plants may have high physiological potential to accumulate metals from contaminated soils, individual soil geochemical factors and the plant-soil interactions in that soil will dictate the actual amount of phytoextractable metal. This underlines the need for site-specific understanding of metal-containing solid phases and geochemical properties of soils before undertaking phytoextraction efforts.

Bioremediation of soil contaminated by dichlorodiphenyltrichloroethane with the use of aerobic strain Rhodococcus wratislaviensis Ch628

The concentration of dichlorodiphenyltrichloroethane (DDT) was determined in a sandy soil of specially Protected Natural Area Osinskaya Lesnaya Dacha (Perm region) 45 years after the last application of the insecticide in this area. The concentration of DDT in the soil exceeded the maximum permissible concentration by 250 times and reached 25.05 mg/kg of soil. Under the conditions of model experiment, efficient decontamination of the soil was recorded in the system with the introduced strain Rhodococcus wratislaviensis Ch628; the DDT concentration decreased by 99.7% and equaled 0.07 mg/kg. The process of DDT degradation proceeded slower in the model soil system with autochthonous microbial complex. In this case, 58.2% DDT degraded in 70 days, and the final concentration was 10.47 mg/kg. The soil lost its toxicity for animal and plant test objects by the end of the experiment only in the model system containing the R. wratislaviensis Ch628 strain.