Support Vector Machine and Nonlinear Regression Methods for Estimating Saturated Hydraulic Conductivity

Pedotransfer functions (PTFs) are widely used for hydrological calculations based on the known basic properties of soils and sediments. The choice of predictors and the mathematical calculus are of particular importance for the accuracy of calculations. The aim of this study is to compare PTFs with the use of the nonlinear regression (NLR) and support vector machine (SVM) methods, as well as to choose predictor properties for estimating saturated hydraulic conductivity (K_s). K_s was determined in direct laboratory experiments on monoliths of agrosoddy-podzolic soil (Umbric Albeluvisol Abruptic, WRB, 2006) and calculated using PTFs based on the NLR and SVM methods. Six classes of predictor properties were tested for the calculated prognosis: K_s-1 (predictors: the sand, silt, and clay contents); K_s-2 (sand, silt, clay, and soil density); K_s-3 (sand, silt, clay, soil organic matter); K_s-4 (sand, silt, clay, soil density, organic matter); K_s-5 (clay, soil density, organic matter); and K_s-6 (sand, clay, soil density, organic matter). The efficiency of PTFs was determined by comparison with experimental values using the root mean square error (RMSE) and determination coefficient (R²). The results showed that the RMSE for SVM is smaller than the RMSE for NLR in predicting K_s for all classes of PTFs. The SVM method has advantages over the NLR method in terms of simplicity and range of application for predicting K_s using PTFs.     

Controlling effects of surface crusts on water infiltration in an arid desert area of Northwest China

Purpose

Surface crusts are important features in arid desert areas and are critical to hydrological processes and ecosystem development. This paper aims to understand the effects of crusts on water movement in the soil and the factors that affect this and to provide the soil parameters for estimation of saturated hydraulic conductivity (K _s) in ecohydrological models.

Materials and methods

The study area was located in the middle and lower reaches of the Heihe River Basin, an arid desert area in Northwest China. There were three crust types in this region: physical soil crusts (PSCs, formed by water drop and erosion), biological soil crusts (BSCs, formed by microorganisms, moss, algae, lichen, and soil materials), and salt soil crusts (SSCs, formed by soluble salts). The infiltration rates of different soil and crust types and scalped soils were determined in situ in the field conditions using a disc infiltrometer with three repetitions. Crusts and soils were collected, and their properties were determined in the laboratory.

Results and discussion

The K _s of crust were significantly lower than that of scalped soils with a decrease of 13–70 %. The K _s of crusts were related to the type of crust and the properties of soil beneath the crusts. In this region, the soil textures are similar throughout, due to ubiquitous loess sedimentation, so textural differences had no significant effect on K _s. Soil organic matter (SOM) played a weak negative role on K _s because most crusts had higher SOM than the underlying soil. However, both crust thickness and electrical conductivity (EC, an index of salt concentration) showed significantly negative exponential relationship with K _s. Therefore, the SSC with high EC and thick crust have the lowest K _s among all crust types. Because soil development is related to salt accumulation, structure, and crust formation, the K _s follows the order of Solonchaks < Cambisols < Regosols, from lowest to highest.

Conclusions

Crusts have different characteristics compared with original soils and are the limiting layer of water infiltration in these arid soils. Therefore, the characteristics of crust must be considered in ecohydrological models. The main apparent controlling parameters of water infiltration rate in this area are crust thickness and EC.

     

Quantitative indices of the distribution of substances in the soil-plant system

New methodological approaches and an algorithm for the quantitative assessment of accumulating a substance by a plant (C _p ) with due regard for its concentration in the soil (C _n ) are proposed. The first approach is the approximation of concentration curves by the functions C _p = f(C _n ) and their parameters. The second one is the standardization of the coefficients of biological sorption (K _b ) of a substance upon its stable concentration in the soil using the function K _b = f(C _n ). As compared to the variation-statistical values of the mean and extreme concentrations, or the coefficients K _b , the proposed parameters are characterized by a higher accuracy and sensitivity. They may be successfully used for quantitative studies of the mechanism and the intensity of the absorption of substances by plants, for the prediction of the accumulation of substances in the trophic chain, and the assessment of soil self-purification (detoxification) and comparative ratings.     

Pedotransfer Functions for the Estimation of Saturated Hydraulic Conductivity for Some Indian Sandy Soils

Determination of the saturated hydraulic conductivity (k_s) is needed in many studies and applications related to irrigation, drainage, water movement and solute transport in the soil. Although many advances are made for direct measurements of k_s, they are usually time consuming and costly. Some attempts have been made to indirectly predict the saturated hydraulic conductivity from the more easily or readily available basic soil properties. The objective of this study was to develop and validate Pedotransfer Functions (PTFs) for estimation of saturated hydraulic conductivity using multiple non-linear regression technique. One hundred and one soil samples were collected from agricultural and forest soils at different depths, at different locations in the Pavanje River basin that lies in the southern coastal region of Karnataka, India. Saturated hydraulic conductivity was measured, by variable falling head method through Permeameter in the laboratory. Prediction accuracies were evaluated using coefficient of determination, root mean square error, mean error, geometric mean error ratio and geometric standard deviation of the error ratio between measured and predicted values. The results show that, the PTFs for the estimation of saturated hydraulic conductivity could be used appropriately for the soils with loamy sand and sandy loam textures falling in this area of the coastal region of southern India.     

Spatial variation of soil respiration in a coastal protection forest in southeastern China

Purpose

Forest soil respiration is an important component of global carbon budgets, but its spatial variation is inadequately understood. This research aimed to measure soil respiration (R _s), soil water content (M _s-5), soil temperature (T), and carbon dioxide (M _co2) in a coastal protection forest (CPF), which is one kind of man-made forests designed for coastal protection primarily along the coast in China, to determine the relationships among them, and to analyze their spatial distributions in a small scale.

Materials and methods

We measured R _s, M _s-5, T, and M _co2 of 100 plots in an approximately flat grid (totally 4 hm²) by LI-8100A in a Casuarina equisetifolia L. forest on a state-owned forest farm of 326 hm² in SE China. Traditional statistics and geo-statistics including semivariance, Moran’s I index, and fractal dimension were used to analyze data.

Results and discussion

Key findings were that (1) the spatial mean of R _s, M _s-5, T, and M _co2 were 1.194 μmol m^?2 s^?1, 11.387 mmol mol^?1, 14.153 °C, and 407.716 ppm, respectively, in the forest; (2) the relationship between soil respiration and the other three factors was weak, while M _s-5, T, and M _co2 have strong relationships with each other; and (3) the four factors, especially soil respiration, had strong autocorrelation within given limits and showed great heterogeneity with 95 % confidence intervals around the means in the study area, all of which can provide important value for the study of carbon cycling and for the sustainable management of coastal protection forests.

Conclusions

According to geo-statistical analysis and field investigations, soil respiration in the coastal forest is less than in some broad-leaf forests but higher than in some conifers. Strong heterogeneity and autocorrelation are clear; however, its relation with other three factors is weak. CPF is a considerable potential forest for carbon conservation if it is well managed.

     

Inverse Estimation of the Hydrodispersive Properties of Unsaturated Soil Using Complex-Variable-Differentiation Method under Field Experiments Conditions

Because soil hydraulic properties are indispensable for determining soil water retention and soil solute movement, their input for simulation models is essential. Many of these parameters cannot be estimated directly at the scale of interest, but can only be derived through inverse modeling. During this process, the parameters are generally adjusted using least-squares approach with Levenberg–Marquardt (LM) algorithms in which numerically simulated models are fitted to measured data. In this study we used a new inverse method to estimate the unsaturated soil hydro-dispersive properties from in-situ experiments. The method employs complex-variable-differentiation method (CVDM) to accurately predict of the hydraulic properties of the van Genuchten–Mualem models (θ_r, θ_s, α, k_s, n). To the knowledge of the authors, it is first study use CVDM in soil physics. The optimization procedure was performed by using a continuous data set of daily in situ soil water content and bromide concentration measurements. Estimated parameters during the inversion showed high correlation (R² = 0.88, RMSE = 0.013 and the model efficiency CE = 0.77) by using the CVDM-methods with the actual field measurements, compared with the traditional LM-algorithm (R² = 0.81, RMSE = 0.021 and CE = 0.626). The results show that the new inverse analysis in the present work has the high accuracy, validity, uniqueness, and higher inversion efficiency. Meanwhile, the convergence and stability of the modified LM-algorithm are improved. Overall, it was concluded that the CVDM is promising method to estimate hydro-dispersive parameters in soil physics.     

Earthworm burrowing activity of two non-Lumbricidae earthworm species incubated in soils with contrasting organic carbon content (Vertisol vs. Ultisol)

The aim of this study was to investigate the burrowing activity of two earthworm species: the endogeic Drawida sinica and one undescribed Amynthas species incubated in Vertisol and Ultisol presenting different soil organic C content. Because of their contrasting feeding behaviours, we hypothesised that soil type would have a bigger influence on the burrowing activity of the endogeic than the anecic species. Repacked soil columns inoculated with earthworms for 30 days were scanned using X-ray tomography and the compiled images used to characterise the burrow systems. After scanning, the saturated hydraulic conductivity (K _sat) was also measured. The Amynthas species burrows were less numerous (30 vs. 180), more vertically oriented (57 vs. 37°), more connected from the surface to the bottom of the columns (73 vs. 5 cm³) and had a higher global connectivity index (83 vs. 28%) than those of D. sinica. The K _sat was threefold faster in columns incubated with Amynthas and was linked to the volume of percolating burrows (R ² = 0.81). The soil type did not influence Amynthas burrow characteristics. In contrast, there were 30% more D. sinica burrows in the Vertisol than in the Ultisol while other burrow characteristics were not affected. This result suggests that these burrows were more refilled with casts leading to shorter and discontinuous burrows. The K _sat was negatively related to the number of burrows (R ² = 0.44) but was not statistically different between the Vertisol and the Ultisol, suggesting a constant impact of this species on the K _sat. We found that a decrease in the amount of soil organic C by 50% had only a small influence on earthworm burrowing activity and no effect on the K _sat.     

Contribution of Soil Components on the Sorption of Chlorpyrifos

It is generally assumed that the sorption of a nonionic pesticide on soil depends mainly on the content of soil organic matter (SOM); however, there are other factors that can contribute to this process. The possible causes of variation in the carbon-normalized partition coefficient (K _OC) for chlorpyrifos (CPF) for a diverse set of ten soils have been investigated. On the one hand, the analysis of the chemical composition of the SOM was analyzed, and on the other hand, the likely interactions between the organic matter and the mineral phase were assessed. Sorption experiments of CPF were performed on whole soil, on soils treated with 2% hydrofluoric acid (HF), and onto calcined soil at 550 °C. Organic matter chemistry of soil was determined by ¹³C CP/MAS NMR spectroscopy; K _OC values were positively correlated with aryl C relative proportion and negatively correlated with alkyl C and O-aryl C proportions and prediction equation of K _OC was found (R ²?=?0.82, p?<?0.001). To evaluate possible organo-mineral interactions, a mathematical model was proposed which calculates the concentration of CPF at equilibrium (C _cal) considering adsorption coefficients for the organic (K _DHF) and inorganic (K _D550 °C) soil constituents, separately. The comparison between C _cal and the equilibrium concentration obtained from experimental data (C _exp) onto whole soil allowed us to confirm that interactions between the OM and clay affect the adsorption of CPF in whole soil. Such findings should be taken into account in the development of predictive models for the evaluation of the fate and transport of this pesticide in soil.     

Possibilities of using the Landau–Deryagin law to evaluate soil degradation as a result of its contamination with chlorides

The contamination of heavy loamy chernozem by iron, sodium, magnesium, calcium, and hydrogen chlorides (2% of soil mass) decreases soil moisture content (W, percent of soil mass) in the interval of the soil moisture pressure (Р) from 0.0 to–0.6 atm, which indicate soil degradation. In a range of P from–0.2 to–0.6 atm, there is a close correlation between the logarithm of Р module (log|P|) and W and, therefore, a regression relationship log|P _W | = |P ₀|–kW, where |P ₀| and k are empirically determined parameters. This relationship is similar to the Landau–Deryagin law. The parameters |P ₀| and k are also in a close correlation, which is described by the regression equation |P ₀| = 29.3k–0.557. At chernozem contamination by chlorides, the |P ₀| and k parameters become smaller, and so they may be used for the evaluation of degradation of chloride-contaminated soils.     

Reaeration Coefficient Estimate: New Parameter for Predictive Equations

The reaeration coefficient (K _a) is an essential parameter to predict the dissolved-oxygen concentration in different aquatic ecosystems. The techniques applied to K _a estimates require considerable efforts, since measuring this coefficient is a laborious and expensive task. Thus, the use of predictive equations wherein K _a is found through hydraulic flow parameters is common. However, the available prediction equations lead to estimates often different from each other. A new predictive equation is addressed in the present study. The insertion of a dimensionless number resulting from the relation between the RMS (Root Mean Square) of the free-surface vertical velocity and the surface flow velocity is the great innovation of the study. The reaeration experiments and the surface vertical velocity mapping were performed in a circular hydraulic channel. The flow velocity varied from 0.25 to 0.64 m s^?1, and depth varied from 0.09 to 0.15 m. The new equation led to more accurate results than the equations based on traditional hydraulic parameters such as the Reynolds and Froude numbers, mainly when it comes to K _a values higher than 40 day^?1. The sensitivity analysis has shown that the new dimensionless number is the most sensitive parameter of the herein proposed predictive equation and that the influence from the Reynolds and Froude numbers on K _a weakens as turbulence gets more intense.     

Enhanced dissipation of DEHP in soil and simultaneously reduced bioaccumulation of DEHP in vegetable using bioaugmentation with exogenous bacteria

The widely used plastic film containing di(2-ethylhexyl) phthalate (DEHP) in agriculture has caused serious soil pollution and poses risks to human health through the food chain. An effective DEHP degradation bacteria, Microbacterium sp. J-1, was newly isolated from landfill soil. Response surface methodology was successfully employed for optimization resulting in 96% degradation of DEHP (200 mg L^?1) within 5 days. This strain degraded DEHP by hydrolysis of the ester bond and hydroxylation of the aromatic ring to form 2-ethyl hexanol, mono-(2-ethylhexyl) phthalate, phthalate acid, and protocatechuic acid, and subsequently transformed these compounds with a maximum specific degradation rate (q _max), half-saturation constant (K _s ), and inhibition constant (K _i ) of 1.46 day^?1, 180.2 mg L^?1, and 332.8 mg L^?1, respectively. Bioaugmentation of DEHP-contaminated soils with the strain J-1 greatly enhanced the DEHP dissipation rate (~88%). Moreover, this strain could efficiently colonize the rhizosphere soil of inoculated vegetables and further enhanced DEHP degradation (~97%), leading to a significant decrease (>70%) in DEHP accumulation in shoots and roots of the inoculated vegetables compared to uninoculated vegetables. The results highlighted the roles of the inoculated exogenous bacteria in simultaneously bioremediating contaminated soils and reducing bioaccumulation of DEHP in the edible part of the vegetable for food safety.     

Partitioning characteristics of PAHs between sediment and water in a shallow lake

Goal, Scope and Background

Distribution of hydrophobic organic contaminants in abiotic compartments is essential for describing their transfer and fate in aquatic ecosystems. Taihu Lake is the third largest freshwater lake in China. Water quality of Taihu Lake has deteriorated greatly during the last decades and has threatened the water supply. The aim of the present study was to investigate the partitioning of polycyclic aromatic hydrocarbons (PAHs) among overlying water, suspended particulate matter (SPM), sediments, and pore water in Meiliang Bay, Taihu Lake and to provide useful information for the ecological engineering in this area.

Materials and Methods

Overlying water and surface sediment were sampled from six sites in Meiliang Bay, Taihu Lake, China. Within 72 h of sampling, sediments were centrifuged to obtain the pore water. Overlying water samples were filtered to separate dissolved and SPM samples. After extraction, samples were purified following a clean-up procedure. PAH fraction was obtained by elution with a mixture of hexane: DCM (7:3, V/V) and analyzed by GC/MS.

Results

PAHs concentrations in overlying water varied from 37.5 ng/L to 183.5 ng/L. Concentrations of PAHs in pore water were higher than those in overlying water. The total concentrations of 16 priority PAHs in sediments ranged from 2091.8 ng/g-dw to 4094.4 ng/g-dw. PAHs concentrations on SPM were decreased with suspended solid concentrations (SSC). Total PAHs concentrations on SPM varied in the range of 3369.6 ng/g-dw to 7531.1 ng/g-dw. The partition coefficients between sediment and overlying water (log K _oc) for PAHs with log K _ow<5 were positively correlated with their octanol-water partition coefficients (log K _ow) (n=39, r=0.79, p<0.0001). Partition coefficients between sediment and pore water (log K _oc′) for all PAHs were also significantly correlated with their log K _ow values (n=48, r=0.82, p<0.0001).

Discussion

In general, PAHs derived from combustion sources tend to bind strongly to soot particles in natural sediment. Consequentially, K _oc values observed in the natural environment could be orders of magnitude higher than those predicted by linear correlation relationships under laboratory conditions. In the present study, the ratio of log K _oc values to log K _ow values falls consistently above 1, indicating that the sediment soot carbon in the bay was more attractive for PAHs than n-octanol. The log K _oc′ was also higher than that predicted under laboratory conditions, suggesting that the measured pore water PAH concentrations were lower than those predicted. That is to say, not all the sediment PAHs can be available to partition rapidly into sediment pore waters. A variation in soot content is a possible reason. Furthermore, concentrations of PAHs on SPM were higher than those in sediments. The compositions of PAHs on SPM and in sediments were similar, indicating the importance of re-suspension process of sediments in the partitioning process of the shallow lake.

Conclusions

The results indicated the equilibrium partitioning model could be used to predict PAHs distribution in various phases of a shallow lake in the stagnation period, but re-suspension processes should be considered to modify the relationship between log K _ocs and log K _ows.

Recommendations and Perspectives

Concentration, particle size and composition of resuspended particles could affect the relationship between log K _ocs and log K _ows. Further work should be done under field conditions, especially where a steady thermodynamic equilibrium state could be assumed.

     

Differential influence of four invasive plant species on soil physicochemical properties in a pot experiment

Purpose

This study compared the effects of four invasive plants, namely Impatiens glandulifera, Reynoutria japonica, Rudbeckia laciniata, and Solidago gigantea, as well as two native species—Artemisia vulgaris, Phalaris arundinacea, and their mixture on soil physicochemical properties in a pot experiment.

Materials and methods

Plants were planted in pots in two loamy sand soils. The soils were collected from fallows located outside (fallow soil) and within river valley (valley soil) under native plant communities. Aboveground plant biomass, cover, and soil physicochemical properties such as nutrient concentrations, pH, and water holding capacity (WHC) were measured after two growing seasons. Discriminant analysis (DA) was used to identify soil variables responsible for the discrimination between plant treatments. Identified variables were further compared between treatments using one-way ANOVA followed by Tukey’s HSD test.

Results and discussion

Plant biomass, cover, and soil parameters depended on species and soil type. DA effectively separated soils under different plant species. DA on fallow soil data separated R. laciniata from all other treatments, especially I. glandulifera, native species and bare soil, along axis 1 (related mainly to exchangeable K, N-NH₄, total P, N-NO_3, and WHC). Large differences were found between R. laciniata and S. gigantea as indicated by axis 2 (S-SO₄, exchangeable Mg, total P, exchangeable Ca, and total Mg). DA on valley soil data separated R. japonica from all other treatments, particularly S. gigantea, R. laciniata, and native mixture, along axis 1 (N-NO₃, total N, S-SO₄, total P, pH). Along axis 2 (N-NO₃, N-NH₄, Olsen P, exchangeable K, WHC), large differences were observed between I. glandulifera and all other invaders.

Conclusions

Plant influence on soil differed both among invasive species and between invasive and native species. Impatiens glandulifera had a relatively weak effect and its soil was similar to both native and bare soils. Multidirectional effects of different invaders resulted in a considerable divergence in soil characteristics. Invasion-driven changes in the soil environment may trigger feedbacks that stabilize or accelerate invasion and hinder re-colonization by native vegetation, which has implications for the restoration of invaded habitats.

     

Survival of <Emphasis Type="Italic">Escherichia coli</Emphasis> O157:H7 in various soil particles: importance of the attached bacterial phenotype

The risk of enteropathogens to food and water is highly dependent on their survival in soil environments. Here, the effects of soil type, particle size, the presence of natural organic matter (NOM) or Fe/Al (hydro)oxides on pathogenic Escherichia coli O157:H7 survival in sterilized soil particles were assessed through survival, attachment, metabolic activity, and qRT-PCR analyses. The abundance of inoculated E. coli O157:H7 in Brown soil (Alfisol) particles increased 0.6–1.4 log₁₀ CFU/g within 3 days (except for NOM-stripped clay), while that in Red soil (Ultisol) particles decreased rapidly in 8 days post-inoculation. Additionally, survival of bacteria was significantly enhanced when Fe/Al (hydro)oxides had been removed from Red soil particles. For the two soils, E. coli O157:H7 survived the longest in NOM-present clays and the bacterial adenosine 5′-triphosphate (ATP) levels were 0.7–2.0 times greater in clays than in sands and silts on day 8. Moreover, clays were more effective than silts and sands in binding cells and changing the expressions of acetate pathway-associated genes (pta and ackA). For silts and sands, E. coli O157:H7 decayed more rapidly in the presence of NOM and similar trends of bacterial ATP levels were observed between NOM-stripped and NOM-present soil particles, indicating that the primary role of NOM was not as a nutrient supply. These findings indicate that soil particles function mainly through attachment to change the metabolic pathway of E. coli O157:H7 and ultimately impact the survival of bacterial pathogens in soils.     

Estimation of the cover and management factor based on stratified coverage and remote sensing indices: a case study in the Loess Plateau of China

Purpose

We attempt to describe the cover and management (C) factor more comprehensively through the use of a simple and efficient method.

Materials and methods

We measure the coverage of each vegetation layer and C factor for 152 sampled plots in the Ansai watershed. We propose four stratified coverage indices (green coverage (V _G), total coverage (V _T), probability coverage (V _P), weight coverage (V _W)), derive green and yellow vegetation indices from Landsat 8 OLI images to reflect green and residue cover, and construct and validate C factor estimation models from stratified coverage and remote sensing indices, respectively.

Results and discussion

(1) V _T and V _P present C factor estimation advantages for grassland and shrub land. V _W can better illustrate the C factor due to the relatively complete spatial structuring of woodland and orchard land. For cropland, four stratified coverage indices present the same estimation capacities for the C factor. Except for cropland and grassland, the estimation capabilities of V _G are relatively low because the residue layer is ignored. (2) The C factor is more sensitive to yellow vegetation indices, which indicates that senescent fractional cover and litter are important and cannot be ignored. The linear and non-linear models can explain 56.6 and 61.8% of C factor variation, respectively, and the linear model is more accurate than the non-linear model. (3) Compared to traditional indices (projective coverage and single remote sensing indices), stratified coverage indices and a combination of several remote sensing indices can estimate the C factor more effectively.

Conclusions

At the field scale, the C value estimation model can be selected according to the land-use type. At the watershed and regional scales, a linear model is recommended for C factor estimation.

     

Effect of Cadmium Stress on Growth and Electrical Impedance Spectroscopy Parameters of <Emphasis Type="Italic">Cotinus coggygria</Emphasis> Roots

The use of plants for ecological remediation is an important method of controlling heavy metals in polluted land. Cotinus coggygria is a landscape plant that is used extensively in landscaping and afforestation. In this study, the cadmium tolerance level of C. coggygria was evaluated using electrical impedance spectroscopy (EIS) to lay a theoretical foundation for broad applications of this species in Cd-polluted areas and provide theoretical support to broaden the application range of the EIS technique. Two-year-old potted seedlings of C. coggygria were placed in a greenhouse to analyse the changes in the growth, water content and EIS parameters of the roots following treatment with different Cd concentrations (50, 100, 200, 500, 1000 and 1500 mg kg^?1), and soil without added Cd was used as the control. The roots grew well following Cd treatments of 50 and 100 mg kg^?1. The Cd contents increased with the increase in Cd concentration in the soil. However, the lowest root Cd content was found at 4 months of treatment. The extracellular resistance r_e and the intracellular resistance r_i increased first overall and then decreased with the increasing Cd concentration, and both parameters increased with a longer treatment duration. The water content had a significant negative correlation with the Cd content (P?<?0.01) and the r_e (P?<?0.05). C. coggygria could tolerate a soil Cd concentration of 100 mg kg^?1. There was a turning point in the growth, water content and EIS parameters of the C. coggygria roots when the soil Cd concentration reached 200 mg kg^?1. The root water content and r_e could reflect the level of Cd tolerance in C. coggygria.     

Effect of the physicochemical parameters of soils on the biological availability of natural and radioactive zinc

The relationship between the main physicochemical properties of soils and the accumulation of natural Zn and ⁶⁵Zn radionuclide has been studied, and the capacity of soils to limit the mobility of the element in the soil–plant system has been assessed. The contribution of each of the selected soil state parameters to the accumulation of zinc by barley has been determined, and the soil state parameters have been ranked. It has been found that the largest contributions to the variation of the resulting parameter (⁶⁵Zn accumulation coefficient, K_a) are made by mobile Fe (25%), free carbonates (21%), and acid-soluble Zn (18%). The largest contributions to the Zn_acK_a are made by free carbonates (13%) and mobile Fe (8%). The contributions of physical clay and organic carbon in soils and qualitative composition of humic substances are almost similar (4% for each). No differences in the inactivating capacity of different soils (soddy-podzolic soils, gray forest soils, and chernozems) for ⁶⁵Zn are observed. This is related to the fact that the transfer of ⁶⁵Zn to plants is statistically significantly controlled by the contents of free carbonates, mobile iron, and potentially plantavailable forms of stable natural Zn (carrier of ⁶⁵Zn) rather than the quantitative and qualitative composition of organic matter and the degree of dispersion of mineral particles. The analysis of the Zn_acK_a/⁶⁵Zn K_a ratios has shown that the share of plant-available Zn in the acid-soluble form of the metal (1 M HCl) is 0.61 on the average for the studied soils, and its share in the total Zn content in the soils is only 0.14.     

Catalase and Phosphatase Activities During Hydrocarbon Removal from Oil-Contaminated Soil Amended with Agro-Industrial By-products and Macronutrients

Microbiological activities are essential in the bioremediation of polluted soils. The enzymatic activities of microorganisms are usually used as a biological indicator of soil health. The aim of this work was to observe the catalase, acid phosphatase (AcP), and alkaline phosphatase (AlP) activities in soil that was amended with agro-industrial by-products and macronutrients during the process of total petroleum hydrocarbon (TPH) removal. To this end, microcosm tests were performed with soil and agro-industrial by-products ratios of 100:2:2, for soil:sugarcane bagasse pith:filter cake mud (SSF); 100:2, for both soil:sugarcane bagasse pith (SS); and for soil filter cake mud (SF). The macronutrients—carbon, nitrogen, and phosphorus—in the experimental treatments were adjusted to 100:10:1 with a solution of NH₄NO₃ and K₂HPO₄. The best TPH removal (51.4%) was obtained with SSF at 15 days. In addition, a significant correlation was observed between TPH removal and AlP as well as AcP (r = 0.74, p < 0.0001; r = 0.70, p < 0.0107, respectively). Fungi growth was also correlated with both AlP (r = 0.97, p < 0.0001) and AcP (r = 0.95, p < 0.0001) activities. Besides, bacterial and fungi growth showed a correlation with TPH (r = 0.86, p < 0.001; r = 0.77, p < 0.0034, respectively). It could be said that the agro-industrial by-products and macronutrients contributed to pollutant removal from the oil-polluted soil at relatively short amount of time. In addition, the enzymatic activities were increased after the treatment; in this study, the high sensitivity enzyme was AlP, and it could be used as an indirect indicator of oil pollutant removal.     

Abundance of transcripts of functional gene reflects the inverse relationship between CH<Subscript>4</Subscript> and N<Subscript>2</Subscript>O emissions during mid-season drainage in acidic paddy soil

Agricultural management significantly affects methane (CH₄) and nitrous oxide (N₂O) emissions from paddy fields. However, little is known about the underlying microbiological mechanism. Field experiment was conducted to investigate the effect of the water regime and straw incorporation on CH₄ and N₂O emissions and soil properties. Quantitative PCR was applied to measure the abundance of soil methanogens, methane-oxidising bacteria, nitrifiers, and denitrifiers according to DNA and mRNA expression levels of microbial genes, including mcrA, pmoA, amoA, and nirK/nirS/nosZ. Field trials showed that the CH₄ and N₂O flux rates were negatively correlated with each other, and N₂O emissions were far lower than CH₄ emissions. Drainage and straw incorporation affected functional gene abundance through altered soil environment. The present (DNA-level) gene abundances of amoA, nosZ, and mcrA were higher with straw incorporation than those without straw incorporation, and they were positively correlated with high concentrations of soil exchangeable NH₄⁺ and dissolved organic carbon. The active (mRNA-level) gene abundance of mcrA was lower in the drainage treatment than in continuous flooding, which was negatively correlated with soil redox potential (Eh). The CH₄ flux rate was significantly and positively correlated with active mcrA abundance but negatively correlated with Eh. The N₂O flux rate was significantly and positively correlated with present and active nirS abundance and positively correlated with soil Eh. Thus, we demonstrated that active gene abundance, such as of mcrA for CH₄ and nirS for N₂O, reflects the contradictory relationship between CH₄ and N₂O emissions regulated by soil Eh in acidic paddy soils.     

Estimation of natural outcrossing rate and genetic diversity in Lima bean (<Emphasis Type="Italic">Phaseolus lunatus</Emphasis> L. var. <Emphasis Type="Italic">lunatus</Emphasis>) from Brazil using SSR markers: implications for conservation and breeding

Lima bean (Phaseolus lunatus L.) is an important food source in Brazil, especially in the northeast region, where its production and consumption are high. The goals of the present study were to estimate natural outcrossing rates and genetic diversity levels of Lima bean from Brazil, using ten microsatellite loci to obtain information for their conservation and breeding. Fourteen accessions were selected from an experiment in field with open-pollinated and with the presence of pollinating insects. Twelve seeds of each of the 14 selected accessions were grown in screenhouse for tissue harvest and DNA extraction. The multilocus model was used to determine the reproductive system. The outcrossing rate was 38.1 % (t_m = 0.381; t_s = 0.078), and the results indicated a mixed mating system with a predominance of selfing (1 ? t_m = 61.9 %). The biparental inbreeding rate was high (t _m  ? t _s  = 0.303) and the multilocus correlated paternity was quite high (r _p(m) = 0.889), indicating that the progeny was mostly composed of full sibs. The average effective number of pollen donors per maternal plant (N _ep ) was low (1.12), and the fixation index for maternal genotypes (F _m ) was 0.945, indicating that most genitors resulted from inbreeding. The studied families presented considerable genetic variability: A = 6.10;  %P = 30; H _e  = 0.60 and H _o  = 0.077. Total diversity was high (H _T = 0.596), and a portion was distributed within families (H _S = 0.058). In addition, diversity was higher between families (D _ST = 0.538), and genetic differentiation was high (G _ST = 0.902). The results presented here can be used in the implementation of Lima bean conservation and breeding programs in Brazil.