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Prolonged leaching of mineral forest soils with dilute HCl solutions: the solubility of Al and soil organic matter 总被引：5，自引：0，他引：5
Long-term acidification has been shown to result in a considerable decrease in the amount of organically bound soil Al and in a gradual decrease in the solubility of Al. We examined the solubility of soil organic matter (SOM) and Al in four acid mineral soils (one Arenosol Ah, two Podzol Bh, and one Podzol Bs) as they were leached sequentially using a solution containing 0.001 m HCl and 0.01 m KCl. The acid leaching resulted in relative decreases in Al that were 2–6 times greater than for organic C. The organic C and Al dissolved by the acid leaching originated mainly in the pyrophosphate-extractable fraction of the elements. Protonation seems to be a major mechanism in stabilizing the residual SOM, as indicated by small changes in effective cation exchange capacity with the degree of acid leaching. In the samples of Podzol Bh and Arenosol Ah soils the solubility of Al (defined as log10 {Al3+ } + 1.5pH) in equilibrium suspensions (0.01 m KCl) was closely related to the ratio of pyrophosphate-extractable Al to pyrophosphate-extractable organic C. The Podzol Bs sample probably contained a small amount of a surface-reactive Al(OH)3 phase, which rapidly became depleted by the acid leaching. 相似文献
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Sephadex G-25 was used with 0.01 m sodium acetate containing a concentration of 3×10?5m Cu(II) as eluent to establish the molecular-size distribution (MSD) and the Cu complexation of molecular-weight fractions of organic solutes. The appropriateness of this modified gel permeation method for complexometric measurements on soluble humic Substances was investigated employing various types of soil solutions. The presence of Cu in the eluent had an effect on the MSD obtained by elimination of electrostatic repulsion between gel and solutes. No evidence was found that the presence of Cu in the chromatographic system induced aggregation of the organic substances. The Cu-binding capacity of the samples as obtained with this gel permeation method was found to increase linearly over a wide sample concentration range varying from 40–2000 mg C dm?3. No interference was observed between the Cu-complexation by exclusion and inclusion peaks in the chromatograms. The analyses revealed that the fraction apparently low in molecular weight makes a large contribution to the complexation potential of forest soil solutions. 相似文献
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Organically-bound Al in acidic, base-poor sandy soils seems to be a major contributor to dissolved Al. This hypothesis has been tested under field conditions at two intensely acidified sites. The research was conducted at the agricultural trial fields at Lyczyn, Poland, which have been fertilized continuously for 30 yr with 130 kg ha?1 a?1 N (as NH4NO3 or urea). The effect of depletion of Al on its solubility was also studied. Field data confirmed that mobilized Al originates largely in the organically bound fraction of soil Al. Depletion of this fraction resulted in a considerable decrease in the mobility of Al such that, at pH = 3.0 and reaction times of a few weeks, small amounts of Al were mobilized. Apparently, the rate at which Al is dissolved from structural silicates, which are abundant in the soil investigated, is small. This suggests that at sites in Poland most exposed to acid deposition, where the rates of soil acidification and depletion of organically-bound Al are greatest, both the concentration of Al and the soil solution pH are expected to decline with time. 相似文献
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The nature of subsurface flow depends largely on hydraulic conductivity of the vadoze zone, permeability of the underlying bedrock, existence of soil layers differing in hydraulic properties and macropore content, soil depth, and slope angle.Quantification of flow pathways on forested hillslopes is essential to understand hydrological dynamics and solute transport patterns.Acrisols, with their argic Bt horizons, are challenging in this respect.To further elucidate flow pathways of water and short-term variability of soil moisture patterns in Acrisols, a field study was conducted on a forested hillslope in a sub-catchment of the Tie Shan Ping(TSP)watershed, 25 km northeast of Chongqing City, China.This catchment is covered by a mixed secondary forest dominated by Masson pine(Pinus massoniana).Soil saturated hydraulic conductivity(K sat) was significantly reduced at the interface between the AB and Bt horizons(2.6 × 10~(-5) vs.1.2 × 10~(-6) m s~(-1)), which led to that the flow volume generated in the Bt horizon was of little quantitative importance compared to that in the AB horizon.There was a marked decrease in porosity between the OA and AB horizons, with a further decrease deeper in the mineral subsoil.Especially, the content of soil pores 300 μm was higher in the AB horizon(14.3%)than in the Bt horizon(6.5%).This explained the difference in soil K sat values.This study showed that Bt horizon had limited water transport capability, forcing part of the infiltrated rainwater as interflow through the OA and AB horizons.Thus, the topsoil responded quickly to rainfall events, causing frequent cycles of saturation and aeration of soil pores. 相似文献
5.
森林养分循环模型应用 总被引：1，自引：0，他引：1
The nutrient cycling model NuCM is one of the most detailed models for simulating processes that influence nutrient cycling in forest ecosystems. A field study was conducted at Tieshanping, a Masson pine （Pinus massoniana Lamb.） forest site, in Chongqing, China, to monitor the impacts of acidic precipitation on nutrient cycling. NuCM simulations were compared with observed data from the study site. The model produced an approximate fit with the observed data. It simulated the mean annual soil solution concentrations in the two simulation years, whereas it sometimes failed to reproduce seasonal variation. Even though some of the parameters required by model running were measured in the field, some others were still highly uncertain and the uncertainties were analyzed. Some of the uncertain parameters necessary for model running should be measured and calibrated to produce a better fit between modeled results and field data. 相似文献
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A simple model of soil organic matter complexation to predict the solubility of aluminium in acid forest soils 总被引：1，自引：0，他引：1
L.G. WESSELINK N. VAN BREEMEN J. MULDER P.H. JANSSEN 《European Journal of Soil Science》1996,47(3):373-384
A simple equilibrium model for competitive binding of Al and protons to soil organic matter shows that Al activities in soil solutions of acid mineral soils are controlled by complexation reactions with soil organic matter. The model successfully explains the relation between pH and the activity of dissolved Al in several forest soils. Furthermore, we found evidence that pools of organically bound Al may be depleted fairly quickly. Kinetically controlled dissolution of inorganic soil Al compounds, which may be considerable, is the main cause for the re-supply of the organically bound Al in the soil. The previously reported decrease in Al solubility that accompanies measured decline in organically bound Al in three Dutch soils was found quantitatively consistent with the model for organically bound Al proposed here. 相似文献
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Anne C. RICHER-de-FORGES Dominique ARROUAYS Laura POGGIO Songchao CHEN Marine LACOSTE Budiman MINASNY Zamir LIBOHOVA Pierre ROUDIER Vera L. MULDER Herv&#; N&#;D&#;LEC Guillaume MARTELET Blandine LEMERCIER Philippe LAGACHERIE Hocine BOURENNANE 《土壤圈》2023,33(5):731-743
Digital maps of soil properties are now widely available. End-users now can access several digital soil mapping (DSM) products of soil properties, produced using different models, calibration/training data, and covariates at various spatial scales from global to local. Therefore, there is an urgent need to provide easy-to-understand tools to communicate map uncertainty and help end-users assess the reliability of DSM products for use at local scales. In this study, we used a large amount of hand-feel soil texture (HFST) data to assess the performance of various published DSM products on the prediction of soil particle size distribution in Central France. We tested four DSM products for soil texture prediction developed at various scales (global, continental, national, and regional) by comparing their predictions with approximately 3 200 HFST observations realized on a 1:50 000 soil survey conducted after release of these DSM products. We used both visual comparisons and quantitative indicators to match the DSM predictions and HFST observations. The comparison between the low-cost HFST observations and DSM predictions clearly showed the applicability of various DSM products, with the prediction accuracy increasing from global to regional predictions. This simple evaluation can determine which products can be used at the local scale and if more accurate DSM products are required. 相似文献
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