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1.
The sensitivity of catchments to acidification is often assessed by calculation of weathering rates for comparison of the rates of release of base cations with the measured acidic inputs. Methods of calculation of weathering rates include (1) long-term rates from elemental depletion in soil profiles; (2) current rates from input-output budgets; (3) strontium isotope ratios to modify current rates for calcium; (4) modelling using PROFILE or MAGIC; (5) laboratory experimental methods. Not all these methods can be applied in any one situation and when more than one method can be used, there are often discrepancies in the resulting figures. Comparison of long-term and current rates with acidic inputs are often consistent with the known acidification status of some Scottish catchments, but in others it is often difficult to establish a relationship. In some catchments where acidification only occurs under high-flow conditions, for example, long-term rates (12–24 meq m?2a?1) are an order of magnitude lower than current rates (185–340 meq m?2a?1). In seven Scottish catchments on four rock types, weathering rates calculated by PROFILE are of the same order of magnitude as long-term rates calculated for the same soil profiles. Current rates, on the other hand, are always higher than the long-term rates, sometimes by a factor as high as 22, and although this could indicate that release of base cations from these soils has increased in recent times, possibly due to anthropogenic inputs, the comparisons may not be valid. 相似文献
2.
A.C. Edwards J. Creasey U. Skiba T. Peirson-Smith M.S. Cresser 《Soil Use and Management》1985,1(2):61-65
Abstract. The approximate time-scales for serious lowering of the base status of acidic upland soils in northeast Scotland have been based on assessments of geochemical weathering rates in two upland catchments. Periods of 1100 and 12000 years are obtained for soils evolved primarily from granite and quartz-biotite-norite respectively. Factors regulating the rate of removal of base cations in drainage water are discussed, to elucidate those which significantly influence long-term rates of soil acidification. The relationship between base cation leaching and river water acidity is briefly considered. 相似文献
3.
S. J. Langan M. E. Hodson D. C. Bain R. A. Skeffington M. J. Wilson 《Water, air, and soil pollution》1995,85(3):1075-1081
The release of base cations from chemical weathering is the fundamental process by which base cations lost through leaching or biological uptake are replenished. Soils with a high content of easily weatherable minerals will, in general, be readily able to neutralise incoming acidity and satisfy biological requirements through this supply of base cations from weathering. Conversely those soils with a low content of such minerals will be unable to buffer acid inputs or meet biological demands and will be vulnerable to acidification. It is evident therefore that an accurate estimate of the rate of chemical weathering is a prerequisite for any assessment of ecosystem sensitivity to acidification. The principal methods by which these calculations are made can be grouped into those based on element depletion in soil horizons calculated against a conservative element reference, catchment fluxes, laboratory studies and the use of mathematical models which utilise data from each of these sources. A review of the published data has been undertaken to determine if a systematic variation in weathering rates can be observed for a range of parent materials and/or methods used. Variations of 0.03–0.8 keq ha?1yr?1 for K+, 0.0–1.0 keq ha?1yr?1 for Na+, 0.01–1.39 keq ha?1yr?1 for Mg2+ and 0.0–5.8 keq ha?1yr?1 for Ca2+ were found. In general individual cation weathering rates determined from catchment fluxes, and also the model MAGIC, are dominated by Ca2+, with Mg2+ being the next most significant release rate. However it has not been possible to determine any other systematic variations due to the limited number of sites where weathering rate has been determined by more than one method. 相似文献
4.
The PROFILE model is used extensively in the European Critical Loads programme as an aid to international negotiations on SO2 emission abatement. PROFILE calculates the rates of cation release by mineral weathering and it then uses these data to calculate soil solution and runoff chemistry. No independent assessment of the underlying assumptions and data in the model has been published and this paper reports such an assessment. The rate equations, which are the key to the PROFILE model require rate coefficients and constants. These have been derived from the literature but more work is required to produce a consistent set of constants. Manipulation of these rates to take into account the exposed reactive surface area of the minerals is fraught with problems. Calculation of exposed mineral surface area from soil textural data results in under-estimates and the requirement to determine the surface area fraction of the different minerals in the soil to be known is extremely difficult if not impossible. Further uncertainty is introduced by adjustment of the rates to take into account temperature differences and by the use of a default mineralogy which is compositionally unrealistic. Despite its flaws PROFILE usually predicts similar weathering rates to other methods of calculation. It is argued that the unrealistic constraints imposed by the use of the surface area equation may be responsible for limiting calculated weathering rate to a fixed range which coincides with characteristically determined values for weathering rates. 相似文献
5.
The soils of the Golan basaltic plateau were surveyed and analyzed. Soils on uneroded plateaus range from montmorillonitic calcareous Reddish Brown Grumusols in the semi-arid areas through noncalcareous Brown Grumusols in the sub-humid areas to Brown and Red Mediterranean Soils with typical argillic horizons and dominance of kaolinitic clay in the humid parts of this region. Protogrumusols and basaltic Lithosols are found in eroded places. Volcanic cone soils in the humid Golan parts range from tuffic Regosols on the youngest cones and most eroded areas through tuffic Red Mediterrranean silty clay loam and silty loam on less eroded areas to tuffic Red Mediterranean clays on the older volcanic eruption sites and comparatively stable slopes.The weathering of the basalt is comparatively very slow, especially in the drier upland areas of the southern Golan. The weathering of the pyroclastic materials, on the other hand is fast, due to the great internal surface of this parent material.The various soils exhibit different leaching stages. A gradual disappearance of lime, decrease in pH values, increase in exchangeable H+ and a shift from montmorillonite clay dominance to kaolinite and similar clay types expresses the increase in the leaching degree from the dry areas to the moist ones.The textural profile of Golan soils depend on clay content and type. A soil sequence commencing with self-mulching Grumusols through various intermediate types to typical ABC Red and Brown Mediterranean Soils may be distinguished along climatic, time and drainage gradients. 相似文献
6.
Long-term changes in weathering rates in mineral soil horizons from the Alltcailleach Forest, north-east Scotland, were estimated from a 3-month leaching experiment conducted using archived soils sampled in 1949/50 and 1987. Data on changes in surface exchange chemistry, total element composition and mineralogy are also presented. The most sensitive Group 1 sites were characterized by a decrease in weathering rate and exchangeable Ca and Mg with time. Sodium increased in the total, exchangeable and the weatherable pools. The more base-rich Group 2 sites exhibited a slight increase in weathering rate between 1949/50 and 1987. The results have implications for the use of weathering rates in the modelling of long-term acidification of soils and water, and in the use of Na in weathering calculations as an element which is assumed not to accumulate in the soil-plant system. 相似文献
7.
土壤风化速率研究及其应用 总被引：4，自引：1，他引：3
土壤矿物风化是土壤、也是整个生态系统中无机矿质养分的最重要来源,不仅为植物长期提供养分和保持土壤的化学平衡稳定性,并缓冲土壤和地表水的酸化,还影响全球气候变化。风化速率在全球碳循环、酸临界负荷和土壤侵蚀等研究中都是非常重要的参数。土壤化学风化是一个不断进行的自然释放过程,气候是最主要的驱动力,而矿物本身的稳定性也影响了风化速率的快慢。由于人为影响下的大气酸沉降和农业活动已经非常普遍,目前的土壤风化速率也因此而改变。本文从风化速率的研究方法、风化速率的影响因素以及风化速率在全球变化中的应用3个方面介绍了近年来在风化速率方面的研究进展,并探讨了相关研究未来的发展趋势。 相似文献
8.
Tamon Fumoto Junko Shindo Noriko Oura Harald Sverdrup 《Water, air, and soil pollution》2001,130(1-4):1247-1252
Adaptation of the steady-state soil chemistry model PROFILE was studied, on the following two parts, to calculate the critical loads for East Asian soils: (1) Dissolution rate coefficients of volcanic glass were derived from published experimental data, and calculated field weathering rate was compared with the rate estimated based on Sr isotope analysis. When BET surface area of sand fraction was regarded as mineral surface area, the calculated rates fairly agreed with the estimate, suggesting that sand fraction surface area is a reasonable estimate of weatherable mineral surface area of volcanic soils. (2) In repeated leaching experiments, Al solubility of a number of Japanese soils was explained by a model which assumed complexation of Al to soil organic matters. Such an Al solubility model is more appropriate for predicting soil chemistry than apparent gibbsite dissolution equilibrium. 相似文献
9.
Evaluation of the stoichiometry of base cations (BCs, including K+, Na+, Ca2+, and Mg2+) and silicon (Si) (BCs:Si) during soil mineral weathering is essential to accurately quantify soil acidification rates. The aim of this study was to explore the differences and influencing factors of BCs:Si values of different soil genetic horizons in a deep soil profile derived from granite with different extents of mineral weathering. Soil type was typic acidi-udic Argosol. Soil samples were collected from Guangzhou, China, which is located in a subtropical region. To ensure that the BCs and Si originated from the mineral weathering process, soil exchangeable BCs were washed with an elution treatment. The BCs:Si values during weathering were obtained through a simulated acid rain leaching experiment using the batch method. Results showed that soil physical, chemical, and mineralogical properties varied from the surface horizon to saprolite in the soil profile. The BCs:Si values of soil genetic horizons during weathering were 0.3-3.7. The BCs:Si value was 1.7 in the surface horizon (A), 1.1-3.7 in the argillic horizon (Bt), and 0.3-0.4 in the cambic (Bw) and transition (BC) horizons, as well as in horizon C (saprolite). The general pattern of BCs:Si values in the different horizons was as follows: Bt > A > Bw, BC, and C. Although BCs:Si values were influenced by weathering intensity, they did not correlate with the chemical index of alteration (CIA). The release amounts of Si and BCs are the joined impact of soil mineral composition and physical and chemical properties. A comprehensive analysis showed that the BCs:Si values of the soil derived from granite in this study were a combined result of the following factors: soil clay, feldspar, kaolinite, organic matter, pH, and CIA. The main controlling factors of BCs:Si in soils of different parent material types require extensive research. The wide variance of BCs:Si values in the deep soil profile indicated that H+ consumed by soil mineral weathering was very dissimilar in the soils with different weathering intensities derived from the same parent material. Therefore, the estimation of the soil acidification rate based on H+ biogeochemistry should consider the specific BCs:Si value. 相似文献
10.
Changes in acidity of Udic Ferrosols, caused by growth of Choerospondias axillaris (Roxb.) Burtt et Hill, in comparison to wild grass, were investigated for Ph distribution in the soil profile, exchangeable acidity, and cation status in the soil leachate of a simulated leaching experiment. Soils were sampled in profiles at 5 cm intervals to a depth of 100 cm. In the 15--60 cm layer the soils with 10-year old C. axillaris had significantly lower Ph (P < 0.05), with the largest difference being 0.41; and in the 25--75 cm soil depths, especially in the 30--55 cm layer, the soils had a significantly higher exchangeable acidity, ranging 1.93 to 3.02 cmolc kg-1. There was also higher aluminum, potassium, and sodium contents in the soil leachate under C. axillaris than with wild grasses. This suggested that the growth of C. axillaris accelerated acidification of Udic Ferrosols and promoted soil clay mineral weathering. 相似文献
11.
12.
The PROFILE model is a steady state soil chemistry model which is used to calculate soil weathering rate. The model has also been used to calculate critical loads of acidity and N to forest soils, using the ratio of Ca+Mg+K to total inorganic aluminium in the soil solution as criterion, and to surface waters, using the ANC leached from the soil column as criterion. An uncertainty analysis of the PROFILE model was performed by Monte Carlo analysis, varying input parameter errors individually and simultaneously in ranges of ±10–100%, depending on parameter. The uncretainty in calculation of weathering rate, ANC leaching and ratio of Ca+Mg+K to inorganic Al in the soil solution was studied for three Nordic sites. Furthermore, the effect of uncertainty in estimates of critical load for forest soils was assessed. The analysis shows that the weathering rate can be calculated with high precision, provided that the errors of input parameter are within the range that has been reported in the literature. The model tend to be less sensitive to errors in input parameters for the range of conditions where forest damage is most likely to occur. Critical loads of acid deposition for one site calculated on the basis of the model varies within a largest range of ±40%. A study of one geographical grid included in the Swedish critical loads assessment shows that with the number of calculation points in the grid, the distribution of critical loads will stay stable independently of stochastic errors. 相似文献
13.
酸雨对黄土磷的淋溶效应 总被引：1，自引：0，他引：1
采用室内土柱模拟淋溶试验,分析了陕西省杨凌区3种土壤在5个酸雨梯度的侵蚀作用下,土壤磷的释放和迁移规律.结果表明,酸雨会使土壤受到一定程度的酸化,而土壤的酸化程度与酸雨的pH值、土壤的类型、土壤的pH值、阳离子交换量、有机质含量有关.土壤对酸雨的缓冲能力由大到小的顺序为:腐殖质层＞母质层＞黏化层.随着酸雨累积淋溶量的增加,土壤磷的释放总量呈增加趋势,但淋失率会下降.酸雨的pH值为5时土壤磷的累积淋失量最大,土壤磷的累积淋失量和淋失率顺序为:腐殖质层＞黏化层＞母质层.酸雨对腐殖质层的磷具有最强侵蚀效应.母质层和黏化层的酸化主要发生在土壤表层,而腐殖质层酸化主要发生在土壤底层,酸雨侵蚀后腐殖质层酸化最严重.长期的酸雨侵蚀会导致土壤磷流失,造成土壤养分贫瘠化. 相似文献
14.
Thirty two soil samples from China were analyzed for exchangeable K before and after drying. Most soil samples were higher in exchangeable K after air-drying and ovendrying (60°C) than when wet. Soil clay minerals, especially clay-size mica, affected K released in air-dry and oven-dry samples. According to composition of clay minerals of air-dried samples, five classes were recognized. Soil samples with high mica and montmorillonite have the highest exchangeable K. Samples that contained higher kaolinite than mica had lower exchangeable K. Samples with higher kaolinite than quartz and mica had still lower exchangeable K. Samples of sandy soils contained very low exchangeable K. When quartz was the main mineral, the samples that had kaolinite and gibbsite as the main clay minerals had very low exchangeable K. The degree of weathering (weathering mean) bore an inverse relationship to the amount of K released on drying in air or at 60°C. Udults and Udalfs (Red Earths) of southeastern China, because of their high K release on being dried, are inferred to have received fine mica from the Western Desert dust rainout, reported to Liu et al. (1981). 相似文献
15.
J. Fichter E. Dambrine M.-P. Turpault J. Ranger 《Water, air, and soil pollution》1998,104(1-2):125-148
In spruce and beech stands, mineral budgets for a rotation period were calculated from measured element fluxes. The release of base cations by mineral weathering was calculated with the steady state soil chemistry model PROFILE. The calcium release rate by weathering of the mineral fine earth was extremely low. For the period of one rotation, mineral weathering cannot provide enough Ca to compensate timber harvesting and leaching. Forest sustainability depends strongly on the amounts of Ca gained from deposition and lost by biomass removal. Magnesium was supplied by atmospheric deposition and mineral weathering. Calculated weathering rates were close to present soil losses. However, as the model assumes that all dissolution reactions are congruent, the computed release rate of Mg from illite might be too high. Main inputs of K to the soil solutions were primarily attributed to canopy leaching and litterfall in upper horizons and to mineral weathering in deeper horizons. The cation budget of the beech stand was much more equilibrated than that of the spruce stand. Given possible changes in silviculture and deposition chemistry, the sustainability of the present stands is rather improbable with respect to their mineral supply. 相似文献
16.
To calculate critical acid loads or to predict elementconcentrations in the soil solution, information on weatheringrates is essential. Several studies have taken place in theNetherlands to obtain weathering rates for non-calcareous sandysoils. Recently information on weathering rates in less vulnerable loess and clay soils have become available. However,up to now no system is available to estimate weathering rates ona regional scale by relating them to regionally available soilproperties.To obtain weathering rates of loess and clay soils on a regionalscale for the Netherlands, the applicability of a statisticalregression model and the process based PROFILE model have beenevaluated. Both models were calibrated on a set of laboratoryexperiments. To evaluate their predictive power, both methodswere validated on a number of sites for which field weatheringrates were available.Predictions with the statistical model, for the individual basecations, were generally within a factor 2 of the calculatedhistorical weathering rates, except for Ca, which wasoverestimated, by a factor 3 to 4. PROFILE stronglyoverestimated all weathering rates using both standard parameters and in particular after calibration on the laboratoryrates. However, PROFILE predicted weathering rates of the loesssoils quite good after calibration on historical weatheringrates, indicating that the downscaling procedure used in PROFILEto translate laboratory to field weathering rates is inadequatefor the considered soils.The statistical model was applied to predict weathering rates,for the Netherlands on a 1 × 1 km grid scale. Weathering rates at the present pH values in forested loess and clay soilsranged from 135 to 6000 molc ha-1 a-1 in loesssoils and from 100 to 1750 molc ha-1 a-1 in claysoils. 相似文献
17.
Simon J. Langan Harald U. Sverdrup Malcolm Coull 《Water, air, and soil pollution》1995,85(4):2497-2502
To investigate the weathering rates of different soil parent materials which occur in Scotland, a study has been undertaken in which detailed soil mineralogy has been used to calculate base cation release. To calculate base cation release, this data, and supplementary soil chemistry and physical attribute data, have provided the input to the PROFILE model. The model is a multi-layer, steady state, deterministic model in which the soil is represented by a series of mixed tank reactors, each of which has the mineralogical, physical and chemical attributes measured for individual soil horizons. The major parent materials from which Scottish soils have developed are glacial till, derived from acid to basic igneous rocks, schist and other metamorphic types, Lower Palaeozoic greywackes and shales, Old Red Sandstone sediments, Carboniferous sediments and Permo-Trias sediments. For each of the parent materials, three soil profiles were analysed and used with the PROFILE model. The base cation release rates, calculated for these parent materials in the top 50cm of the soil profile, varies between 0.2 and 3.2 keq/ha/yr, although, for a given parent material, the range was usually quite small. In general, these results compare very favourably with those suggested for the calculation of critical loads using an empirical approach proposed at Skokloster. In comparison with current rates of deposition, this suggests many of these soils are being acidified and that for many soil-plant combinations, the critical load may be exceeded. 相似文献
18.
Soil scientists have been encouraged to investigate soils for clay minerals by very fact that soil characteristics fundamentally depend upon the nature of their clay. It is generally recognized that clays of different species develop under different conditions such as drainage, temperature weathering age, and parent rocks. On Kyushu Island, heavy, reddish soils derived from olivine basalt cover a considerably large area of its northeastern part, and a numbar of small islands belonging to Kyushu. Koga * of this laboratory found a basaltic soil of clay consisting of hydrated halloysite, halloysite, hematite, and gibbsite at the eastern foot of Mt. Tara, by examining its clay separates by X-ray, thermal, chemical, and electron microscopical techniques. Kanno et al5 reported that in a basaltic soil at Oura, Saga prefecture, hydrated halloysite developed from plagioclase and ferro-magnesian minerals with gibbsite and hematite which was more abundant than in other Red and Yellow Soils. They also found some illite present in the soil derived from unknown minerals, and halloysite dehydrated in upper layers. 相似文献
19.
中国土壤酸化呈现出全国普遍发生的趋势,对作物产量、农产品品质和生物多样性造成不利影响。自20世纪50年代以来,我国在酸性土壤方面开展了大量工作,取得显著成效,但因我国酸性土壤分布详情不明、土壤酸化机制存在争议、耐逆作物品种缺乏、作物酸害阈值不清、改良产品及技术落地性差等问题,酸性土壤利用仍受到极大限制。针对上述问题,绘制了新的中国土壤酸碱度图,明确了我国酸性土壤的分布详情,讨论了土壤酸化机制特别是氮肥与土壤酸化之间的关系,论述了土壤酸化的危害,解析了植物和微生物对酸性土壤的响应和适应机制,提出了分区分级分类改良、酸度改良和肥力提高并重、有机无机肥配施、发展特色农业等酸性土壤改良和利用策略,建议进一步加强酸性土壤新型改良剂、作物酸害阈值、氮肥高效利用、中微量元素、耐逆作物育种和土壤酸化模型等方面研究,以期为酸性土壤可持续利用提供支撑。 相似文献
20.
Immobile element-based weathering estimation methods assume that Zr (or Ti) is an immobile element, and that weathering rates of other elements can be estimated according to the enrichment of Zr in weathered horizons relative to an unweathered parent material. This approach was used to estimate base cation weathering rates for 33 soil profiles on acid-sensitive terrain in north-eastern Alberta. Zirconium generally showed enrichment within the rooting zone, but the deepest (subsoil) samples were not always associated with the lowest Zr concentrations. Weathering rates estimated with the Zr depletion and Pedological Mass Balance (PMB) methods were generally low (ranges: 0-51 and 0-58 mmolc m− 2 yr− 1, respectively); however, low base cation oxide concentrations and heterogeneity within soil profiles complicated weathering rate calculations and net base cation gains were calculated for several (six) sites. Evaluation of the Zr depletion and PMB weathering estimates against those calculated with the process-oriented PROFILE model at a subset (n = 9) of the sites indicated the estimates were poorly related, with PROFILE rates typically being higher. The effects-based emissions management strategy for acid precursors in this region requires spatial coverage of soil properties (including weathering rates) across a large area, but the apparent limitations associated with the immobile element based methods in this region: identifying representative parent soils and deriving weathering rate estimates comparable to more robust methods are arguments against their candidacy for future use. 相似文献