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Chad Van Furl John A. Colman Michael H. Bothner 《Water, air, and soil pollution》2010,213(1-4):275-286
Recent studies have shown that the lower basin of the Salado River is highly polluted with copper and chromium. In order to evaluate the effect of those metals on Notodiaptomus conifer, a representative calanoid copepod, we carried out two (acute and chronic) experimental assays. In the first one, the 24- and 48-h EC50 values were determined in nauplii and adults. Chronic assays were conducted to evaluate the time of development for nauplii, time of development for each copepodite stage, total development time, growth, number of ovigerous females, fecundity, and time required to produce the first egg sac. Additionally, the effect of those metals on the equiproportional model proposed for copepods was evaluated. Acute experiments reveled that juveniles were more sensible than adults. Although growth was not seriously affected by metal exposition, development time was delayed and reproductive variables were altered with the increase of metal concentrations. The deviation from the equiproportional model proposed for copepods proved to be a useful parameter to provide relevant information on toxicity of both metals along development time. In comparison with other zooplanktonic species, the highest sensitivity of N. conifer to copper and chromium makes it a suitable bioindicator in ecotoxicological tests. 相似文献
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Spreadsheet optimization using a range of nonlinear error functions was utilized for parameter estimation of the two-phase pressure–saturation models developed by van Genuchten, Brutsaert, Russo and Kosugi. The data was obtained from the UNSODA database (US Salinity Laboratory, Riverside, California). Results show that spreadsheet optimization is a practical platform for evaluations based on minimizing nonlinear error functions, consequently allowing for a broader mathematical approach to parameter estimation. An error function representing the sum of the squares of errors provided the best fit for a majority of the soils evaluated, although the fractional error function provided the best fit for silts and loams. Outcomes indicated that the van Genuchten parameters m and n may also be estimated individually as opposed to following the published relationship of m=1?1/n. 相似文献
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In this study, an artificial neural networks (ANN) model was developed to predict the removal of a polycyclic aromatic hydrocarbon (PAH), namely, naphthalene from marine oily wastewater by using UV irradiation. The removal rate was used as model output and simulated as a function of five independent input variables, including fluence rate, salinity, temperature, initial concentration and reaction time. The configuration of the ANN model was optimized as a three-layer feed-forward Levenberg–Marquardt backpropagation network with log-sigmoid and linear transfer functions at the hidden (12 hidden neurons) and output layers, respectively. By considering goodness-of-fit and cross validated predictability, the ANN model was trained to provide good overall agreement with experimental results with a slope of 0.97 and a correlation of determination (R 2) of 0.943. Sensitivity analysis revealed that fluence rate and temperature were the most influential variables, followed by reaction time, salinity and initial concentration. The findings of this study showed that neural network modeling could effectively predict the behavior of the photo-induced PAH degradation process. 相似文献
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Biodiversity in wetland habitats is strongly affected by drainage. In Sweden, rich fens (alkaline fens) have been particularly affected by drainage campaigns for forestry and conversion to agricultural land. Fragmentation of the landscape, invasion of tall vascular plants as well as Polytrichum and Sphagnum mosses and substrate degradation all lead to reduced plant diversity.We evaluated the recolonization potential of four characteristic rich fen bryophyte species that use to decrease rapidly after drainage (Scorpidium scorpioides, Scorpidium cossonii, Pseudocalliergon trifarium and Campylium stellatum) by performing transplantation studies with gametophyte fragments in recently hydrologically restored rich fens. In greenhouse and field experiments 1 cm fragments of all four species had a high survival rate and established well, especially after surface liming of the peat. A protective cover increased the colonization success and the growth potential of the added fragments. Even small alterations of the water level (5 cm) resulted in differences in biomass growth of the fragments of S. cossonii and C. stellatum. Our results show that it is possible to reintroduce bryophyte species lost after drainage using gametophyte fragments as propagules, and that these techniques seem feasible for a number of characteristic rich fen bryophytes. These findings will be of importance when methods for practical restoration of rich fens are developed. 相似文献
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Indolic compounds are N-heterocyclic aromatic chemicals and have been detected at contaminated sites. Biodegradation of 1-methylindole (1MI) and 3-methylindole (3MI) was investigated initially using enrichment cultures with mangrove sediment obtained from Mai Po Nature Reserve of Hong Kong and subsequently with a pure culture of Pseudomonas aeruginosa Gs confirmed with 16S rRNA gene. At 2.0 mM, 1MI and 3MI were degraded in 4 and 3 days, respectively, by the respective 1MI- and 3MI-degrading enrichment cultures. When substrate concentrations were increased to 3.0,mM and 3.5,mM, slower degradation of 1MI and 3MI was observed indicating inhibitory effects from the substrates, possibly due to toxicity. In addition, no colony of bacteria could be observed on the agar plates amended with 3.5,mM 1MI or 4.0,mM 3MI, indicating that 1MI was more toxic than 3MI. Pseudomonas aeruginosa Gs, isolated from the enrichment culture, effectively utilized both substrates as the sole source of carbon and energy. Complete degradation of 1MI and 3MI was achieved after more than 40 days and 24 days, respectively, at an initial concentration of 2,mM in the culture. Effects of initial substrate concentration, pH and salinity on degradation of 1MI and 3MI by P. aeruginosa Gs were also studied in batch culture. The optimum pH and salinity for degrading both substrates by P. aeruginosa Gs was 7.0 and 5?, respectively. Biodegradation kinetics of 1MI and 3MI by P. aeruginosa Gs could be described using a first-order kinetic model. Our results suggest that both 1MI and 3MI are biodegradable in the mangrove environment and that toxicity of 1MI could be a potential factor limiting the removal of the chemical in the environment by microorganisms. 相似文献
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In order to evaluate the long‐term impact of intercrop management on runoff and erosion in a continuous maize cropping system a new model was developed, based on the continuous plot‐scale runoff model of Laloy & Bielders (2008) . This model is called the Continuous Runoff and Erosion Hillslope model with DYnamic soil Surface properties (CREHDYS). This paper details the erosion and crop growth and decay model components and presents a thorough global variance‐based sensitivity analysis (GSA) with regard to the erosion prediction, followed by a Bayesian parameter identifiability assessment. As compared with the classical local univariate sensitivity analysis, a GSA is able to deal with the typical non‐linearity of process‐based hydrological and erosion models. The most influential parameters were the Manning's roughness coefficient followed by the saturated hydraulic conductivity of wheel track cells and the median particle size of the material. The soil aggregate stability and soil‐cohesion parameters were found to be almost non‐influential. Most of the results of the parameter identifiability procedure were in close agreement with the GSA. Indeed, the parameter uncertainty seemed to be proportional to the degree of influence, with Manning's coefficient being the most precisely identified, whereas soil and wheel track cohesion parameters showed the largest uncertainty. Exceptions were the soil aggregate stability and the Green‐Ampt soil matric potential. The uncertainty associated with the former was surprisingly low given its low level of influence whereas the uncertainty associated with the latter is partially explained by its negative correlation with the soil saturated hydraulic conductivities of overland flow and wheel track cells. 相似文献
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A more detailed mechanistic understanding of how low molecular weight (MW) carbon (C) substrates are mineralized within the rhizosphere by soil microbial communities is crucial to accurately model terrestrial C fluxes. Currently, most experiments regarding soil C dynamics are conducted ex-situ (laboratory) and can fail to account for key variables (e.g. temperature and soil water content) which vary in-situ. In addition, ex-situ experiments are often highly invasive, e.g. severing root and mycorrhizal networks, changing the input and concentrations of low MW exudates within soil. The aim of this study was to directly compare the mineralization rates of 31 common low MW C substrates under ex- and in-situ conditions. In addition, we also assessed the inter-annual field variability of substrate mineralization rates. We added trace concentrations of 31 individual 14C-labelled common low MW C substrates into the top soil of an agricultural grassland and monitored the mineralization rates by capturing 14CO2 evolved from the soil over 7 d. Our results showed that the contribution of low MW C components to soil respiration was highly reproducible between parallel studies performed either in-situ or ex-situ. We also found that differences in the mineralization of individual compounds were more variable inter-annually in the field than between the laboratory and the field. Our results suggest that laboratory-based C mineralization data can be used to reliably parameterize C models but that multiple experimental measurements should be made over time to reduce uncertainty in model parameter estimation. 相似文献
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Feng Zeng Kunyan Cui Jiamo Fu Guoying Sheng Huifang Yang 《Water, air, and soil pollution》2002,140(1-4):297-305
Di(2-ethylhexyl)phthalate (DEHP), one of high-molecular weightphthalate esters (PAEs), is used in the manufacturing of polyvinylchloride (PVC) resins, polyvinyl acetate, cellulosics,and polyurethanes, and contributes to environmental pollution. In this article, the characteristics of DEHP biodegradation by aneffective degradation bacterium, Pseudomonasfluorescens FS1 that isolated from the activated sludge at a petrochemicalfactory, was capable of using phthalate esters as the sole carbonand energy source, were investigated. Experimental results showedthat the biodegradation of DEHP by P. fluorescens FS1 could be described by the first-order reaction model, whichcould be expressed as: lnC = –0.0688t + A, and the half-life ofDEHP biodegradation was 10.07 d when the initial concentrations of DEHP were less than 50 mg L-1. The inhibition effects ofDEHP as a substrate had become predominant above the concentration of 50 mg L-1. The PAEs-degrading enzyme of P. fluorescens FS1, mainly located in the soluble part andthe particle of cytoplasm, was an intracellular enzyme. The metabolites of DEHP degradation by P. fluorescens FS1, which monoester, phthalic acid, benzonic acid, phenol, wereextracted using dichloromethane at different time intervals and identified by the GC-MS. The tentative pathway proposed for degradation of DEHP by P. fluorescens FS1 under aerobic condition is monoester in the beginning, further enzymatic degradation of the monoester produces phthalic acid, benzonic acid, phenol and finally CO2 and H2O. 相似文献
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Yu Jia Åsa Frostegård Gijs D. Breedveld Lars R. Bakken 《Soil biology & biochemistry》2007,39(7):1597-1608
Deep transport of degradable compounds through soils may occur if the metabolic activity in the soil profile is low; either by natural causes (low temperature during ice melt) or by toxic pollutants. De-icing chemicals (for roads and airports) represents a severe challenge to the soil's purifying capacity; rapid infiltration of contaminated water occurs in near-frozen soil, the contamination includes toxic compounds. Degradation experiments were conducted with toluene, and three compounds frequently used for de-icing; acetate, formate and glycol. The substrates were added to a subsoil (0.93 μmol substrate-carbon (C) g−1 soil, with ample amounts of nitrogen (N) and phosphorous (P)); and their mineralization was monitored in the presence of a toxic compound, benzotriazol (BTA) at various concentrations. BTA is commonly used as an additive in commercial de-icing fluids. A second and third dose of substrate was added after complete degradation of the previous one. The mineralization curves of the three consecutive doses were used to estimate kinetic parameters by fitting to a Monod-model. The model parameters estimated for each substance were the initial biomass C of the organisms growing on each substrate, Cb0, their maximum substrate uptake rates, Vmax, their apparent substrate affinity, KS, and growth yield, Y. The Cb0 values for pristine soil were 4.9, 20.5 and 10 nmol C g−1 soil for formate, glycol and acetate, respectively, and 1-2 orders of magnitude lower for toluene. The KS values were 1.1, 0.6, 2.5 and 0.13 mM for formate, glycol, acetate, and toluene, respectively. The high KS values probably reflect diffusion limitations. The estimated yields (Y) in the absence of BTA were 0.032, 0.53 and 0.42 g biomass-C g−1 substrate-C for growth on formate, glycol and acetate, respectively. BTA invariably reduced the growth yield for organisms growing on the different substrates, and the yield reduction increased with increasing BTA concentrations (more than 50% reduction at 400 mg BTA l−1). The degradation of the four substrates showed major differences in BTA-sensitivity, and there were strikingly weak signs (if any) of increasing BTA tolerance during growth in the presence of BTA (analyses of second and third dose experiments). The modelling of the consecutive substrate doses corroborated previous investigations of BTA effects on mineralization and community PLFA [Jia et al., 2006. Organic compounds that reach subsoil may threaten groundwater quality; effect of benzotriazole on degradation kinetics and microbial community composition. Soil Biology & Biochemistry 38, 2543-2556]. The results and the estimated Monod parameters are useful for predictive modelling of transport and degradation of pollutants as well as natural substances in sub-soils. 相似文献
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Yasutomo Hoshika Makoto Watanabe Naoki Inada Takayoshi Koike 《Water, air, and soil pollution》2012,223(7):3893-3901
We examined a performance of the multiplicative stomatal conductance model to estimate the stomatal ozone uptake for Fagus crenata. Parameterization of the model was carried out by in-situ measurements in a free-air ozone exposure experiment. The model performed fairly well under ambient conditions, with low ozone concentration. However, the model overestimated stomatal conductance under enhanced ozone condition due to ozone-induced stomatal closure. A revised model that included a parameter representing ozone-induced stomatal closure showed better estimation of ozone uptake. Neglecting ozone-induced stomatal closure induced a 20?% overestimation of the stomatal uptake of ozone. The ozone-induced stomatal closure was closely related to stomatal ozone uptake rather than accumulated concentrations of ozone exceeding 40?nmol mol?1. Our results suggest that ozone-induced stomatal closure should be implemented to stomatal conductance model for estimating ozone uptake for F. crenata. The implementation will contribute to adequate risk assessments of ozone impacts on F. crenata forests in Japan. 相似文献
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To date there have only been a few studies that measured mercury emissions from background substrate worldwide, and only a small amount of mercury flux data, from background substrate, exists for the Western United States. Because of this, the database of mercury emissions from background units < 0.1 mg kg-1 mercury) is incomplete. This study focused on the collection of in-situ mercury flux data from representative lithologic units in Nevada. Measured mercury fluxes from substrate with background mercury concentration throughout Nevada were low (mean 2.0 ± 4.1 ng m-2 hr-1), and ranged from –3.7 to 9.3 ng m-2 hr-1. The mean measured mercury flux is slightly higher than those measured from background substrate from various locations throughout the world. The mean mercury flux from in-situ mercury measurements from substrate located near altered geologic units across Nevada was 15.5 ± 24.2 ng m-2 hr-1. These mercury fluxes are higher than the values applied in published global models for naturally enriched geologic units. 相似文献
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Sabtanti Harimurti Binay K. Dutta Idzham Fauzi B. M. Ariff Sampa Chakrabarti Davide Vione 《Water, air, and soil pollution》2010,211(1-4):273-286
Alkanolamines in the wastewater from gas treating plants are not readily biodegradable. In this work, we have investigated the effectiveness of the Fenton’s reagent (H2O2-Fe2+) to treat monoethanolamine (MEA) as a model compound in simulated wastewater. Degradation studies were carried out in a jacketed glass reactor. The effects of concentrations of ferrous sulfate, hydrogen peroxide, and the pH of a solution on the rate of reaction were determined. A pH of 3 was found to be the optimum. The degradation reaction proceeds very fast at the beginning but slows down significantly at a longer time. A larger fractional degradation of the organics in solution was observed if the initial chemical oxygen demand (COD) of the feed solution was high. Gradual addition of H2O2 to the reaction mixture increased the COD removal by about 60% compared to one-time addition of the reagent at the beginning of the process. A rate equation for mineralization of the amine was developed on the basis of a simplified mechanistic model, and the lumped value of the rate constant for COD removal was determined. A partially degraded MEA solution as well as “pure” MEA was subjected to biological oxidation by activated sludge. The former substrate degraded much faster. The degradation rate and biomass generation data could be fitted by the Monod kinetic equations. 相似文献
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Maria Hojdov?? Tom??? Navr??til Jan Rohovec Karel ???k Ale? Van??k Vladislav Chrastny Radek Ba?e Miroslav Svoboda 《Water, air, and soil pollution》2011,214(1-4):73-82
The adsorption of lead onto date palm fibers (palm fibers) and leaf base of palm (petiole) has been examined in aqueous solution by considering the influence of various parameters such as contact time, solution pH, adsorbent dosage, particle sizes, ionic strength, and temperature. The adsorption of Pb(II) increased with an increase of contact time. The optimal range of pH for Pb(II) adsorption is 3.0?C4.5. The linear Langmuir and Freundlich models were applied to describe the equilibrium isotherms, and both models fitted well. The monolayer adsorption capacity of Pb(II) on palm fibers and petiole was found as 18.622 and 20.040 mg/g, respectively, at pH 4.5 and 25°C. Dubinin-Radushkevich (D-R) isotherm model was also applied to equilibrium data. The mean free energy of adsorption (2.397 and 4.082 kJ/mol) onto palm fibers and petiole, respectively, may be carried out via physisorption mechanism. Pseudo-first-order rate equation and pseudo-second-order rate equation were applied to study the adsorption kinetics. In comparison to first-order kinetic model, pseudo-second-order model described well the adsorption kinetics of Pb(II) onto palm fibers and petiole from aqueous solution. From the results of the thermodynamic analysis, Gibbs free energy ??G, enthalpy change ??H, and entropy ??S were determined. The positive value of ??H suggests that interaction of Pb(II) adsorbed by palm fibers is endothermic. In contrast, the negative value of ??H indicates that interaction of Pb(II) ions by petiole is exothermic. The negative value of ??G indicates that the adsorption of Pb(II) ions on both palm fibers and petiole is a spontaneous process. 相似文献
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Michael S. Hutcheson C. Mark Smith Gordon T. Wallace Jane Rose Barbara Eddy James Sullivan Oscar Pancorbo Carol Rowan West 《Water, air, and soil pollution》2008,191(1-4):15-31
We sampled and analyzed individually, edible dorsal muscle from largemouth bass (LMB), Micropterus salmoides (n?=?138) and yellow perch (YP), Perca flavescens (n?=?97) from 15 lakes to investigate potential local impacts of mercury emission point sources in northeastern Massachusetts (MA), USA. This area was identified in three separate modeling exercises as a mercury deposition hotspot. In 1995, 55% of mercury emissions to the environment from all MA sources came from three municipal solid waste combustors (trash incinerators) and one large regional medical waste incinerator in the study area. We determined the mercury accumulation history in sediments of a lake centrally located in the study area. Recent maximum mercury accumulation rates in the sediment of the lake of ~ 88 μg/m2/year were highly elevated on a watershed area adjusted basis compared to other lakes in the Northeast and Minnesota. Fish from the study area lakes had significantly (p?=?0.05) greater total mercury concentrations than fish from 24 more rural, non-source-impacted lakes in other regions of the state (LMB n?=?238, YP n?=?381) (LMB: 1.5–2.5 x; YP: 1.5 x). The integration of this extensive fish tissue data set, depositional modeling projections, historical record of mercury accumulation in sediments of a lake in the area, and knowledge of substantial mercury emissions to the atmosphere in the area support designation of this area as a mercury depositional and biological concentration hotspot in the late 1990s, and provides further evidence that major mercury point sources may be associated with significant local impacts on fisheries resources. 相似文献
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Andrew C. P. Heaton Clayton L. Rugh Nian-Jie Wang Richard B. Meagher 《Water, air, and soil pollution》2005,161(1-4):137-155
Plants expressing a modified bacterial mercury reductase, merA, are highly resistant to Hg(II) toxicity as a result of the enzymatically catalyzed electrochemical reduction of Hg(II) to the much less toxic and volatile Hg(0). merA expression may allow plants to manifest a suite of responses to mercury exposure, making them more capable than wild-type plants of interacting with and removing mercury from contaminated soil or water. We have engineered merA-expressing Nicotiana tabacum (tobacco) as a model plant for examining these responses. Mercury resistance was demonstrated by germinating and growing merA tobacco seeds on semi-solid medium spiked with a HgCl2 concentration acutely toxic to wild-type plants. On similar growth medium, merA plant roots penetrated a highly concentrated, localized Hg(II) zone of HgS (cinnibar) more readily than wild-type roots. In hydroponic medium spiked with HgCl2, merA plants maintained higher evapotranspiration activity than wild-type plants. The ability of merA Hg(II)-reductive activity to counter typical plant-catalyzed Hg(0) oxidation to Hg(II) was demonstrated by a lower net foliar absorption of atmospheric Hg(0) than wild-type plants. Mercury translocation through merA plants was examined through reciprocally grafted merA and wild-type tobacco grown on HgCl2-spiked hydroponic medium. Elevated mercury concentrations in wild-type shoots grafted to merA roots suggest the vertical movement of mercury within merA tissues or plants may be facilitated by dynamic balance between native Hg(0) oxidation and MerA-catalyzed Hg(II) reduction. These experiments demonstrate that merA-engineered tobacco plants display an array of tissue-level and whole-plant attributes which should allow for more efficient mercury extraction and processing compared to the wild-type. 相似文献
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In arid and semi-arid regions, pioneer organisms form complex communities that penetrate the upper millimetres of the bare substrate, creating biological soil crusts (BSC). These thin crusts play a vital role in whole ecosystem functioning because they enrich bare surfaces with organic matter, initiate biogeochemical cycling of elements, modify hydrological cycles, etc., thus enabling the ground to be colonized by vascular plants. Various hydrolase enzymes involved in the carbon (cellulase, β-glucosidase and invertase activities), nitrogen (casein-protease and BAA-protease activities) and phosphorus (alkaline phosphomonoesterase activity) cycles were studied at three levels (crust, middle and deep layers) of three types of BSCs from the Tabernas Desert (SE Spain), representing an ecological gradient ranging from crusts predominated by cyanobacteria to crusts predominated by lichens (Diploschistes diacapsis, Lepraria crassissima). All enzyme activities were higher in all layers of all BSCs than in the bare substrate. The enzymes that hydrolyze low molecular weight substrates were more active than those that hydrolyze high molecular weight substrates (cellulase, casein-protease), highlighting the pioneering characteristics of the BSCs. The hydrolytic capacity developed in parallel to that of ecological succession, and the BSCs in which enzyme activity was highest were those under L. crassissima. The enzyme activity per unit of total organic C was extremely high; the highest values occurred in the BSCs formed by cyanobacteria and the lowest in those formed by lichens, which indicates the fundamental role that the primary colonizers (cyanobacteria) play in enriching the geological substrate with enzymes that enable degradation of organic remains and the establishment of more developed BSCs. The results of the study combine information on different enzyme activities and provide a clear vision of how biogeochemical cycles are established in BSCs, thus confirming the usefulness of enzyme assays as key tools for examining the relationship between biodiversity and ecosystem function in biological soil crusts. 相似文献
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The saturated hydraulic conductivity (Ks) of the soil is one of the main soil physical properties. Indirect estimation of this parameter using pedo-transfer functions (PTFs) has received considerable attention. The Purpose of this study was to improve the estimation of Ks using fractal parameters of particle and micro-aggregate size distributions in smectitic soils. In this study 260 disturbed and undisturbed soil samples were collected from Guilan province, the north of Iran. The fractal model of Bird and Perrier was used to compute the fractal parameters of particle and micro-aggregate size distributions. The PTFs were developed by artificial neural networks (ANNs) ensemble to estimate Ks by using available soil data and fractal parameters. There were found significant correlations between Ks and fractal parameters of particles and microaggregates. Estimation of Ks was improved significantly by using fractal parameters of soil micro-aggregates as predictors. But using geometric mean and geometric standard deviation of particles diameter did not improve Ks estimations significantly. Using fractal parameters of particles and micro-aggregates simultaneously, had the most effect in the estimation of Ks. Generally, fractal parameters can be successfully used as input parameters to improve the estimation of Ks in the PTFs in smectitic soils. As a result, ANNs ensemble successfully correlated the fractal parameters of particles and micro-aggregates to Ks. 相似文献