土壤风化速率研究及其应用

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。     

Hydrogeochemical Conditions Affecting Acidification of Stream Water in Mountainous Watersheds

Acid deposition in eastern Asia will increase and freshwaters in Japan are likely to become acidified in future. In order to make long-term predictions about freshwater acidification, it is necessary to evaluate acid neutralization mechanisms in Japanese watersheds. Ikeda and Miyanaga (1999) earlier proposed a method of separating acid-neutralization capacity into chemical weathering and cation exchange. By this means, we were able to assess the effect of hydrogeochemical properties on chemical weathering and stream water chemistry for three watersheds in Japan. On the basis of this assessment, acid-neutralization stream water chemistry was predicted using the ILWAS (Integrated Lake-Watershed Acidification Study) model. The main factors determining acidification are the thickness of weatherd profile and chemical weathering rates. The principal results are: (1) for non-acidified watersheds in Japan, acid deposition is neutralized by chemical weathering of primary minerals; (2) freshwaters in Japanese watersheds will not acidify even if acid deposition increases to the extent found in an acidified watershed in the U.S.A.     

Aquatic Acidification Sensitivity for Regional Environment: a Multi-Indicator Evaluation Approach

With the aggravation of acid rain pollution and the enlarging of the acid rain regions in China, the sensitivity evaluation of natural waters to acidification on a regional scale become increasingly important. Acidification models based on a single indicator cannot give much information on aquatic acidification because of their simplicity; yet acidification models based on physical, chemical, hydrological and/or biological processes are not suitable for large scale regional research because of their exceptional complexity. In this paper, a multi-indicator comprehensive model for aquatic acidification sensitivity is proposed and applied. This model comprises some of the most important factors that are considered to influence water acidification, in particular: acid neutralization capacity, acidification capacity, acidification sensitive index, cation exchange capacity of soil, pH of soil, and weathering shuck types of soil-forming. It highlights the key stages of aquatic acidification by acid neutralization capacity, acidification capacity, and acidification sensitivity index. The model thereby estimates the acidification sensitivity of natural waters by using these indicators according to a weighting system. Equal-weight and non-equal-weight approaches are separately used to combine the six indicators into an overall sensitivity index of aquatic acidification. The result derived from an application to China on a national scale indicates the practicability of this approach. In China, the sensitive natural waters emerge in Southern China, which is already a heavy acid rain region, and in Northeastern China where the rainwater is beginning to become much acidic.     

Stoichiometry of base cations and silicon during weathering of a deep soil profile derived from granite

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.     

Bildung schlechtkristalliner bis amorpher Verwitterungsprodukte in stark bis extrem versauerten Waldböden

Formation of poorly crystallized weathering products in strongly to extremely acid forest soils Poorly crystallized weathering products, formed as a consequence of wide-spread extrem acidification and silicate weathering in forest soils, were examined using X-ray diffraction (XRD) and fluorescence (XRF), scanning electron microscopy (SEM, EDXRA) and chemical analyses. The investigations were carried out on five extremely acid forest soils (different Luvisols, a Gleyic Luvisol and a Luvic Podzol) derived from different parent materials (loess, sand loess, glacial sands/loam) in Northrhine Westfalia and Schleswig-Holstein. The results reveal an intense destruction of clay minerals and other silicates in the extremely acid topsoils leading to an accumulation of poorly crystallized to amorphous compounds. These weathering products occur predominantly as silicic coatings on the surface of soil aggregates or as small spherical precipitates on mineral surfaces. Besides Si they contain small amounts of Al and Fe.     

酸沉降影响下近20年来衡山土壤酸化研究

对不同时期采自衡山东坡垂直带谱上6个典型土壤剖面Ah层和AB层的样品分析,土壤酸化指标研究结果表明,近2 0年来,由于酸沉降的影响,由花岗岩风化物发育的各类土壤,都有不同程度的酸化,表现在pH值下降,交换性酸,尤其是交换性Al3 增加,交换性盐基总量减少,盐基饱和度下降,特别是土壤酸缓冲性能和土壤酸害容量降低。相比之下,山顶的常湿淋溶土和山麓的湿润富铁土酸化更明显,而山体中部的常湿富铁土酸化进程较慢,山体上部的常湿雏形土酸化进程更慢,表明土壤酸化除了与土壤酸沉降量有关外,还与土壤类型有关     

1984年以来广东水稻土pH变化趋势及影响因素

利用广东省1984年以来的长期定位监测数据,对全省20多年来的水稻土pH变化趋势进行了分析。结果表明:1984年以来,全省水稻土整体呈现明显的酸化趋势,期间水稻土pH下降了0.33单位,强酸和酸性土壤的分布频率呈明显的上升趋势,分别增加了3.2%和21.9%;珠三角地区的水稻土pH下降了0.54单位,明显高于其他区域。单施化肥使土壤pH降低,而长期坚持化肥结合有机肥施用可以提高土壤抵抗酸化的能力,提高水稻土pH。重化肥而轻有机肥是导致广东省水田土壤pH下降的主要原因,同时日益严重的酸雨也是加速土壤pH下降的重要因素。今后应重视施用有机肥,减缓水稻土的酸化进程。     

A Comparison of Soil Sensitivity to Acidification Based on Laboratory-Determined Short-Term Acid Buffering Capacity and the Skokloster Classification

The sensitivity of mineral soils to anthropogenically-induced acidification may be assessed using the Skokloster classification or by considering the short-term acid buffering capacity (STABC). The Skokloster classification is based on the assumption that the majority of acidification neutralization is due to base cation release from mineral weathering. It therefore considers the long-term neutralizing capacity of a soil on a scale of decades. The STABC of a soil is due largely to the adsorption and exchange of H+ ions by soil components, and acts on the scale of single years. The United Kingdom maps generated to identify soils that are sensitive to acidification use the Skokloster classification. A comparison of the laboratory-determined STABC of the different horizons from soil profiles with the Skokloster classes of soils shows that there is generally no correlation between the two. Maps showing soil sensitivity to acidification based on measured STABC and Skokloster classes are markedly different. The STABC measure has the potential for quantitatively assessing a soil's sensitivity to acidification, while the Skokloster approach is empirical. It may be possible to combine the two approaches to produce a dynamic method of assessing soil recovery from acidification.     

Atmospheric deposition effects on the chemistry of a stream in Northeastern Georgia

A modeling study of the Allt a Mharcaidh catchment in the Cairngorm region of Scotland has been undertaken to investigate long term trends in acidification and model sensitivity to soil physical and chemical characteristics. The MAGIC model (Model of Acidification of Groundwater In Catchments) is used to demonstrate that the sulphate adsorption ability of the soil and quality and quantity of rainfall inputs have significant effects on model output. Optimal weathering rates and predicted present day ion concentrations in streamwater compare well with measured and observed values. The analysis shows that the catchment has become progressively acidified since pre-industrial times but major changes in stream acidity have yet to occur.     

Natural and anthropogenic components of soil acidification

The following 8 theses are theoretically founded and experimentally quantified. 1. Rocks contain only bases and no acid precursors. Therefore, with the exception of sulfide containing rocks, soils cannot acidify as a result of atmospheric rock weathering. 2. A consumption of protons in rocks and soils results in a decrease of their acid neutralizing capacity (ANC) and can result in the buildup of a base neutralizing capacity (BNC). Strong soil acidification leads to the formation of stronger acids from weaker acids in the solid phase; this may be connected with a decrease in the BNC. 3. Weak acids (carbonic acid) lead in geological times to the depletion of bases without a larger accumulation of labile cation acids. Strong acids (HNO₃, organic acids, H₂SO₄) can lead within a few decades to soil acidification, i.e. to leaching of nutrient cations and the accumulation of labile cation acids. 4. The acid input caused by the natural emission of SO₂ and NO_x can be buffered by silicate weathering even in soils low in silicates. 5. The cause of soil impoverishment and soil acidification is a decoupling of the ion cycle in the ecosystem. 6. Acid deposition in forest ecosystems which persists over decades leads to soil acidification. 7. Formation and deposition of strong acids with conservative anions (SO₄, NO₃) shifts soil chemistry into the Al or Al/Fe buffer range up to great soil depth. In such soils eluvial conditions prevail throughout the solum and even in upper part of the C horizon: in connection with the decomposition of clay minerals, Al and eventually Fe are being eluviated. The present soil classification does not include this soil forming process. 8. In the long run, soil acidification by acid deposition results in the retraction of the root system of acid tolerant tree species from the mineral soil, and in water acidification.     

Mechanism of acid-neutralization in two Japanese watersheds

In Japan, acidification of terrestrial water has not yet been reported except lakes acidified by volcano or mine. However, acid deposition in Japan is as much as those in northern Europe and north-eastern U.S.A., and acidification of terrestrial water may occur in future. In order to predict long-term acidification, it is necessary to understand acid-neutralization mechanism in watershed. Therefore, two experimental watersheds study for geology, hydrology, and water chemistry were conducted. On the basis of these data, chemical change in percolation of precipitation through watersheds and acid-neutralization mechanism are analyzed. The principal results are: (1) Acid deposition is neutralized continuously in percolation of precipitation from ground-surface to aquifer, (2) Chemical weathering of primary minerals plays an important role in the acidneutralization in the watersheds, and should be quantified and taken into account in the long-term prediction of acidification.     

Determining weathering rates of soils in China

As an important parameter for critical load calculation and soil acidification simulation, weathering rates of soils in China were studied using different methods of calculation. The approaches used were the mass balance approach, the soil mineralogical classification, the total analysis correlation, the PROFILE model, the MAGIC model and a simulated leaching experiment. Since chemical weathering of secondary minerals usually plays a much more important role in neutralizing the long-term acidification of soils in China than that of parent material, soil mineralogy rather than parent rock/material type, which is regarded as the most suitable factor representing weathering rates in Europe, should be adopted as the basis for soil classification. The weathering rate assigned to each soil should also be corrected when the effect of temperature is considered. Due to the variation in experimental conditions, the weathering rates of soils from laboratory experiment may be difficult to compare with field determined rates, and should be adjusted by pH and percolation rate. The comparison of various methods in this study shows that the weathering rates of soils estimated by the PROFILE model coincide well with those from other independent methods such as the dynamic modeling by MAGIC and the modified leaching experiment. The weathering rates were very low (usually lower than 1.0 kEq·ha⁻¹·year⁻¹) for Allites (including Latosol, Lateritic Red Earth, Red Earth, Yellow Earth and Yellow-Brown Earth) in south China and Silalsols (consisting of Dark Brown Forest Soil, Black Soil and Podzolic Soil) in northeast China, and very high for Alpine Soils, Desert Soils and Pedocals in west China. The content of weatherable minerals in soil is the most important factor in determining the spatial distribution of weathering rate in China, while the difference in temperature may be the reason why the weathering rate of soil in northeast China was lower than that in southeast China.     

酸雨对土壤生态系统影响的研究进展

酸雨是人类当前面临的最严重的环境问题之-,并目益成为土壤学和生态学研究的热点.现有的大量研究表明,酸雨对土壤生态系统的功能特性,包括土壤的盐基离子以及重金属与微量元素的淋溶、土壤营养、土壤酸化、土壤微生物数量及其活性、土壤缓冲性能、土壤对酸雨的敏感性、土壤结构、土壤矿物风化等方面均会产生一定的影响.本文就酸雨对土壤生态系统特性的影响研究进展进行了综述,旨在为其他学者今后开展相关研究提供参考.     

Acidity of precipitation as influenced by the filtering of atmospheric sulphur and nitrogen compounds — its role in the element balance and effect on soil

Acidity of throughfall precipitation is increased by the filtering of S and N from the atmosphere by trees. An element balance for a beech forest is given. As a consequence of acidification the soil chemical conditions are changed in a way that plants rooting close to the soil surface are affected. Losses of nutrients may pose a problem in forest plant nutrition in the near future in Central European forests on light or medium textured acid soils.     

中国酸性土壤利用的科学问题与策略

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。     

Effects of Acid Deposition on Forest Soils in Northernmost Russia: Modelled and Field Data

In addition to strong natural stresses forest ecosystems in the Kola Subarctic, Russia, receive high loads of sulphur and heavy metals from the nickel smelter. To estimate soil response to acid deposition we compared the soil field data along a pollution gradient and simulated time effects. Multivariate technique was applied to investigate spatial distribution of soil field data. Time response of soils to acid deposition was evaluated with the SMART model. According to field observations there is no evidence for strong soil acidification effects close to the smelter. Concentrations of exchangeable Ca and base saturation increase, while acidity decrease in lower soil mineral horizons towards the pollution source. However, some features seem to reflect the early stages of the started acidification. Most soil profiles have low pH values. Despite increasing of exchangeable Ca and Mg towards the smelter in lower mineral horizons due to geological inheritance, they do not reveal the same trends in the upper ones. Concentration of exchangeable K in organic horizons decreases towards the smelter, thus confirming the starting acidification. As result, exchangeable base cations are depleted in the considerable part of shallow soil profiles. According to model simulation the present acid load does not effect considerably on forest soils in background areas, however, dramatic shift in soil chemistry near the smelter is expected within several decades. Due to low pool of exchangeable base cations and low weathering rate continued acid deposition can lead to increased soil acidification and nutrient imbalance.     

Estimation of soil weathering stage and acid neutralizing capacity in a toposequence Luvisol–Cambisol on loess under deciduous forest in Belgium

Soils derived from loess are extensive in Europe and are well suited for forestry. They are suspected to be poor acid buffers, however. We have estimated the weathering stage and acid neutralizing capacity of acid soils under forest in a toposequence on loess in the Belgian silt belt. The soils vary distinctly in morphology and physico‐chemical properties according to their topographic position. Dystric Cambisols have developed in colluvial deposits in the dry valley floors, whereas Dystric Luvisols have formed on the slopes in a rejuvenated material. The Cambisols are more acid and less saturated in bases than are Luvisols. They are strongly depleted of clay and contain less weatherable minerals. Easily weatherable minerals are concentrated mainly in the clay fraction of both soil types. Clay minerals of size < 2 μm therefore act as major sinks for protons in these soils. A simplified expression taking into account the total reserve in bases, total aluminium and iron occluded in silicates is used to estimate acid neutralizing capacity. Our estimates confirm that these acid loessic soils are indeed poor acid buffers. They show that the Dystric Cambisols depleted of clay are sensitive to potential acidification, whether natural or man‐made.     

Effects of Atmospheric Sea-Salt Deposition on Soils and Freshwaters in Northeast Scotland

The majority of Scottish upland soils are particularly sensitive to acid deposition because of their low weathering rates. The compositions of the exchangeable base cations of such soils in the United Kingdom are dominated by sea salt inputs rather than by mineral weathering inputs of base cations. Catchments with low mineral weathering rates are also those particularly susceptible to freshwater acidification. Therefore, catchments exhibiting a high sea salt effect should also exhibit the most acid waters under base flow and storm flow conditions. A field evaluation study based on 61 catchments in NE Scotland has shown that this is indeed the case. River water pH under both base flow and high flow conditions is correlated stronhly with the relative contribution of Na+ to the sum of Ca2+, Mg2+ and Na+. From these results, an attempt is being made to produce a quantitative signature of weathering for the soils within the catchment upstream of the sampling point. Representative soil samples from the LFH, AE, B and C horizons and on 4 different parent materials have been obtained from the surrounding catchments to validate the above results for associated soil solutions. Sampling took place on upland moorland podzols under Calluna vulgaris. Tension lysimeters were used to sample the soil solutions so that their chemistry could be compared with that of the relevant river water.     

Biotic community shifts explain the contrasting responses of microbial and root respiration to experimental soil acidification

Soil respiration is comprised primarily of root and microbial respiration, and accounts for nearly half of the total CO₂ efflux from terrestrial ecosystems. Soil acidification resulting from acid deposition significantly affects soil respiration. Yet, the mechanisms that underlie the effects of acidification on soil respiration and its two components remain unclear. We collected data on sources of soil CO₂ efflux (microbial and root respiration), above- and belowground biotic communities, and soil properties in a 4-year field experiment with seven levels of acid in a semi-arid Inner Mongolian grassland. Here, we show that soil acidification has contrasting effects on root and microbial respiration in a typical steppe grassland. Soil acidification increases root respiration mainly by an increase in root biomass and a shift to plant species with greater specific root respiration rates. The shift of plant community from perennial bunchgrasses to perennial rhizome grasses was in turn regulated by the decreases in soil base cations and N status. In contrast, soil acidification suppresses microbial respiration by reducing total microbial biomass and enzymatic activities, which appear to result from increases in soil H⁺ ions and decreases in soil base cations. Our results suggest that shifts in both plant and microbial communities dominate the responses of soil respiration and its components to soil acidification. These results also indicate that carbon cycling models concerned with future climate change should consider soil acidification as well as shifts in biotic communities.     

Chemische Eigenschaften von Waldböden im Nordwestdeutschen Pleistocän und deren Gruppierungen nach Pufferbereichen

Chemical properties of forest soils in the pleistocene of Northwest Germany and their classification based on soil buffering systems In order to characterize the chemical characteristics of forest soils of Hamburg, 800 soil samples and 400 root samples from 172 sites were used to obtain suitable soil chemical and ecochemical parameters. A strong and deep reaching soil acidification was observed on all sites with exception of those on till. The sulfate concentration in the equilibrium soil solution allows the conclusion that deposition of acid plays a significant role in this acidification. Classification of sites based on edaphic factors did not provide useful information on the chemical status of soils. However, grouping of soil horizons using pH measured in 0.01 M CaCl₂ lead to a stratification according to the soil buffering systems. Distinction between the exchanger and the aluminium buffer ranges was, however, not quite satisfactory.