Abstract:Risk assessment of leaching of pesticides at field scale level is of importance to protection of the groundwater environment. In this study, a total of 100 soil samples were taken from a field plot (27 m×27 m), which was located in the suburbs of Beijing. Some physico-chemical properties were analyzed of all the samples. By means of soil pedotransfer function, van Genuchten type's hydraulic parameters were generated from measured values of soil particle size fraction and soil bulk density using ROSETTA code. Dispersivities of atrazine were indirectly obtained from water retention curves, and adsorption coefficients of atrazine in different samples were estimated based on measured soil organic carbon content. And then, according to the column-model-based assumption, and with the aid of HYDRUS-1D software, the infiltration-redistribution process simplified from the actual background was simulated for evaluating the maximum risk of atrazine leaching through the unsaturated soil. The results show that, under the condition of a rainfall lasting 3 days with precipitation being 90 mm and intensity 30 mm d^-1 and 20 days of redistribution afterwards, if the effect of evapotranspiration on soil water movement and atrazine transport was negligible, the maximum cumulative amount of atrazine leaching down through the tillage layer (20 cm) was 17.87% and 75.41% of the applied dose, respectively, at the end of the infiltration and of the infiltration-redistribution processes, and spatial variation of the distribution of leaching flux of atrazine in the sampled area was quite different. The predicted vulnerable zone of atrazine leaching can not only provide quantitative basis for rationalizing use of the pesticide for the sake of environment protection, but also supply important information for preventing shallow groundwater from atrazine contamination.

Abstract:A Holocene loess-palaeosol sequence at the Laoguantai site in the eastern part of the Guanzhong Basin was studied for identifying changes in surface hydrology during the last 11 500 years. The profile was dated with the prehistorical remains and optically stimulated luminescence techniques. Results of the studies in the field and the laboratory provide new insights into soil development and pattern of climatic changes in this area. The soil S₀ was a soil complex composed of the lower soil S₀² and the upper S₀¹. Two rainwash beds were identified in the profile, whose presence in the aeolian loess in the southern Loess Plateau means that the climate was wet enough to cause active surface runoff during their deposition. They are regarded as the records of surface hydrological events during the rainy and wet phases. The first humid period identified at 9 000~8 500 a BP in the eastern Guanzhong basin suggested that the rainfall change was evidently not in phase with the temperature change in the early Holocene. The increasing in rainfall took place later than that in the temperature. The second rainwash bed, identified at 4 000~3 600 a BP, was another rainy and wet period. The strength of the soil erosion and deposition was intensified by the human activities in the stage.

Abstract:Remotely sensed images and historical aerial photographs at seven different periods are used to study urban expansion in Yixing city, in the Taihu Lake region, East China in the last 50 years. The results show that the urban area of Yixing expanded by more than 8 times, and the annual expanding rate was only 3% before 1984, and 21% from 1984~2000. Within each period more than 90% of the expanded area is cropland. The expansion was characterized differently from period to period. Before 1984 the urban area expanded separately along the old city boundary, after that the city began to expand along main roads and highways, and then filled in the empty blocks between the roads. The urban development is also confined by river systems, which is a representative characteristics of urban expansion in the Taihu Lake region in China.

Abstract:The technique of Precision Agriculture (PA) has widely been extended at present. Soil sampling by grids is a very important way for nutrient management in PA. The methods of computer-based interpolation was used for analysis of soil nutrients and performanced at five randomly selected soil sampling points. Results were compared between interpolation and actual measurement by grids difference in scales. The interpolation errors of total nitrogen, plant available nitrogen, and plant available phosphorus increased with the size of sampling grids. But those of potassium and other micronutrients showed a reserve trend. The distribution of soil sampling points had a direct effect on interpolation results.

Abstract:Soils of greenbelts alongside in road system (urban trunk roads, belt highways and suburban roads) as well as of the Nanjing Botanical Garden cited as a clean zone were surveyed and assessed for heavy metals. The results show that the contents of most heavy metals in the soils of on the roadside are higher than in the soil of the clean zone. The highest concentrations of Mo, Zn, As, Cd, Cr, Cu, Fe and Mn are found in the soils alongside the belt highways, that of Pb in the soils along side the urban trunk roads and that of Al in the soils alongside the suburban roads. This phenomenon could be further confirmed with the Shannon Weaner Index, indicating a declining order of belt highways (0.293) > urban trunk roads (0.261) > suburban roads (0.238) > "clean zone" (0.236). This result reflects significant variation of soils accumulating heavy metals;The princi pal component plot reveals that the belt highways are areas high in heavy metals;the urban trunk roads areas high in Pb, the sub urban roads areas in Al and Fe, and the clean zone Botanical Garden an area low in heavy metals.

Abstract:Based on the analytic data of soil samples collected from 257 soil layers of 66 soil profiles under 7 soil types in Tibet, characterist ics of the acidity of the acid soils were explored. Acid soils, accounting for one fifth of the total land area of Tibet, are mainly distributed in the southeast of Tibet, under the vegetation of mountain humid forests and alpine shrubby meadows. Soil pH is determined mainly by exchangeable acid in potential acid, especially, exchangeable Al³⁺, which is in dominancy, while non exchangeable acid has less impact on that. The proportion of exchangeable Al³⁺ increases with the in crease in exchangeable acid, but decreases with the increase in OM. However, the relative proportion of exchangeable H⁺ shows a reverse trend Non exchangeable acid comes mainly from OM (through disassociation of H and Al from humic acidic functional groups). Soil pH is in near linear negative correlation with the saturation of exchangeable acid and in non linear one with the saturation of nonexchangeable acid, but in nonlinear positive correlation with base saturation, which is mainly restrained by the dominant exchangeable base Ca²⁺.

Abstract:The indicators are analyzed for the samples taken from 6 typical soil profiles, including Ah and AB horizons on the eastern vertical spectrum of soil in Mt. Hengshan. The results show:1) In the past 20 years, these soils developed on weathering materials of granite have experienced different levels of acidification, which is recognized by such indicators as increase in exchangeable acid, especially exchangeable Al³⁺ as well as decrease in pH, total of exchangeable base, base saturation percentage, and especially soil acid-buffer ability and soil acid-damage capacity. 2) By contrast, acidification is more evident for the perudic luvisol at the top of the mountain and the udic ferrisol at the foot of the mountain while the process of acidification is slow for the perrudic ferrisol on the slopes of the mountain and slower for the perudic cambisol at the upper part of the mountain, suggesting that soil acidification is related not only to the amount of acid precipitation to soil but also type of the soil.

Abstract:Adsorptions of Cu²⁺ and Zn²⁺ by three typical variable charge soils and four typical constant charge soils di-f ferent in pH and in accompanying ion, Na⁺, Zn²⁺ or Cu²⁺ were determined, respectively. The results showed that adsorption of Cu²⁺ and Zn²⁺ by the soils could be described by the Langmiur equation C/(X_m) = 1/Kb+C/b both in the single ion and coexisting ions systems. The adsorption of Cu²⁺ or Zn²⁺ increased with pH and reached a plateau value when the pH value was 5. The affinity in adsorption of Cu²⁺ was greater than that of Zn²⁺. The mechanism of adsorption Cu²⁺ and Zn²⁺ was closely related to chemical composition and surface properties of the soils. The relative contribution of specific adsorption to the adsorption of Cu²⁺ and Zn²⁺ by the variable charge soils was greater than that by the constant charge soils.

Abstract:Rhizosphere is a place where matters exchange and energy transfers concentratedly between soil and plants. In the rhizosphere, there are abundant organic ligands, of which the influence on copper adsorption by soils with permanent and variable charges have not yet been fully understood. Four soils (Yellow cinnamon soil, yellow brown soil, red soil and latosol), which were sampled from Hubei, Hunan and Hainan provinces, representing soils with permanent and variable charges, were used for invest igating effects of organic acids on copper adsorption. The batch adsorption technique was employed in the experi ments. The purpose of the study was to compare differences in copper adsorption between two types of soils with permanent and variable charges in the presence of organic acids so as to provide knowledge of copper uptake by plants. Results indicate that the adsorption of tartrate on the soils was dependent on the soil properties and tartrate concentration. In terms of maximum adsorption, the four soils were in a decreasing order of yellow cinnamon soil> yellow brown soil> red soil> latosol. The adsorption of organic ligands might result in increase in surface negat ive charges of soils, and the magnitude of the increase of the variable charge soils was greater than that of the permanent charge soils. The presence of organic acids increased the copper adsorption at lower concentrations, but decreased at higher ones. A peak appeared at a specific point of organic acid concentration. The point moved up higher with the intensification of variable charge properties of the soils. Moreover, secondary adsorption of copper after organic acids were adsorbed increased more remarkably in variable charge soil than in permanent charge soils. These results demonstrate that heavy metals might have different forms and fates in rhizospheres of the two soils different in charge properties due to difference in surface chemical behavior.

Abstract:A study of Cd²⁺ adsorption of soil samples gathered from the tillage layer(TLLS) and clay layer of Lou soil (CLLS) modified with cetyltrimethylammonium bromide(CTMAB) at various rates and cetyltrimethylammonium bromide + sodium dodecylsulphonate (CTMAB+SDS) mixture was carried out. The results show that in terms of amount of Cd²⁺ adsorbed, a decreasing order of GCK> 50GCB> 120GCS> 100GCB on TLLS and NCK> 50NCB> 100NCB> 120NCS on CLLS, respectively, indicated that the adsorption capacity increased with the rise in temperature;and that a decreasing trend of Cd²⁺ adsorption was quite obvious on modified soils, but not to the extent that the modified soils completely lost their Cd²⁺ adsorption capacities. The Langmuir equation can be used to describe the Cd²⁺ adsorption isotherm. The study of thermodynamic parameters showed that Cd²⁺ adsorption on modified soils was spontaneously controlled by entropy increment, but the capacity property of the soil must be considered simultaneously in discussing the relationship between the adsorption spontaneity and maximal adsorption capacity of Cd²⁺. The analysis of mechanism revealed that modification of the soils was uneven, and that the competition in Cd²⁺ adsorption between the mechanism of cation exchanging adsorption and the mechanism of hydrophobic bonding resulted in the residual adsorption of Cd²⁺ on modified soils. The effect of temperature on Cd²⁺ adsorption was significantly higher in TLLS than in CLLS, indicating that chemical adsorption on TLLS is stronger than that on CLLS.

Abstract:In order to assess effects of chemical properties of soil salinity on electrical conductivity of 1:5 soil water extract (EC_1:5), the relations between EC_1:5 and chemical properties of soil salinity were studied through Path Coefficient analysis. The results obtained show that total soluble salt concentration (SSC), Cl^-, and sodium adsorption ratio (SAR) were the most primary factors to EC_1:5 of coastal sal-taffected soils, while pH, content of CO₃^2- or HCO₃^-, soluble sodium percentage (SSP) and sodium dianion ratio(SDR) affected EC_1:5 very faintly. Though direct path coefficients between content of SO₄^2-、Ca²⁺、Mg²⁺、K⁺ or Na⁺ and EC_1:5 were not high, they were enlarged by influence of other chemical factors, making the summation of indirect path coefficients between EC_1:5 and these factors relat ively higher. Verification showed that the multifactor regression function between EC_1:5 and most of the primary factors had sound reliability and very good accuracy, while errors in deducing electrical conductivities based on the function would somewhat be greater when soil salinity was excessively high.

Abstract:Field experiments were conducted to investigate ammonia volatilization from urea applied to green cabbage (Xiao Qing Cai) in 2002 and Chinese cabbage in 2003 in the suburbs of Nanjing. Ammonia volatilization was measured with the enclosure method. Results obtained were as follows:ammonia volatilization was low (< 0.4%) after urea applied to the green cabbage due to the low pH value of the soil. In the Chinese cabbage field, of which the soil pH was 7.7, ammonia volat ilization from the treatments of controlled release urea (N 180 kg hm^-2), low rate N (300 kg hm^-2) and high rate N (600 kg hm^-2) as urea was 0.97%, 12.1% and 17.1%, respectively, of the total N applied. The results show that soil pH is an important factor affecting ammonia volatilization, reducing N application rate can reduce ammonia loss, and the use of controlled release urea is an effective way to reduce ammonia loss. Results of the experiment on timing of N application to Chinese cabbage show that rainfall following application of urea greatly affects ammonia volatilization because rain water reduces N concentration in the surface soil. The heavier and the closer the rain following the application, the less ammonia lost through volatilization.

Abstract:Nitrate is becoming more and more important for N nutrition of rice plants since rice is now cultivated in intermittent irrigation or even in aerobic soil condition. Moreover, the rhizosphere of rice roots is actually in partial oxidized status due to the released oxygen by rice roots. Solution culture experiments were carried out to study the effect of NO₃^- on the NH₄⁺ uptake kinetics of rice roots and the glutamine synthetase activity (GSA) in leaves of four typical rice genotypes (Conventional Indica, Conventional Japonica, Hybrid Indica, Hybrid Japonica) at the seedling stage (28 day old). The results obtained were as follows. Partial replacement of NH₄⁺ by NO₃^- could improve the growth and N uptake of rice. The rate of NH₄⁺ uptake by dif ferent genotypes was in following order:Hybrid Indica > Conventional Indica> Hybrid Japonica > Conventional Japonica. The presence of NO₃^- could increase the NH₄⁺ uptake of rice. This increase was mainly attributed to a significantly increased V_max (31.5% on average of the four genotypes) in the treatment with NO₃^- while the K_m values for NH₄⁺ (the increased percentage being 4.26% on average of the four genotypes) were not significantly affected by the addition of NO₃^-. NO₃^- could also increase the GSA in the leaves of rice, and thus, the assimilation of NH₄⁺ were improved.

Abstract:Ecological effects of germanium addition to soil on microorganisms and their critical value were emphatically discussed in this paper. A pot experiment was carried out with results demonstrating that low Ge concentration had stimulating ef fect on soil bacteria, fungi, actinomycetes, but when the content of Ge in the soil increased, the stimulating effect began to al ternate with inhabiting one. In the pot experiment, the luminescence of photobacterium phosphoreum spp. T3 showed a strongly negative relationship to the concentration of Ge. If "100%" and "80%" of the luminescence of Strain T3 is deemed as critical values for two grades, the critical concentrations of Ge in soil were est imated to be 50.2 mg kg^-1 and 5.8 mg kg^-1, respectively.

Abstract:Rice straw transformation takes place in soil but effects of rice straws on relations between soils and bacterial communities of the soils are still poorly understood. PCR and denaturing gradient gelelectrophoresis (DGGE) were used to monitor development of bacterial communities in paddy soil and red soil, into which rice straw or rice straw plus biological agent was applied during incubating period, respectively. The total bacterial DNA from the two studied soils was extracted directly on D0, D5, D25, D45 and D70. The DNA from paddy soil was purified twice, but the DNA from red soil was done only once. The regions V3 of the 16S rDNA of bacteria from the two soils were amplified. DGGE profiles of the PCR productions were compared by similarity analysis. The results show simple DGGE profiles for controls of the two soils without rice straw. Rice straw was incubated in paddy soil and red soil for 70 days. DGGE profiles revealed that the composition of the bacterial community in soil with rice straw was more complex than CK during the incubating period. Meanwhile, the results show that peaks of the bacterial communities appeared at different times in the paddy soil and red soil, treated with rice straw during incubation times.

Abstract:More and more evidence showed that rice plant could grow better if provided in part with nitrate (NO₃^-). Changes of the membrane potential of epidermal cells in root tips of four rice (Oryza Sativa L.) cultivars, i. e., Nongken 57 (Japonica), Siyou 917 (Hybrid Japonica), Yangdao 6 (Indica), Shanyou 63 (Hybrid Indica) were monitored using microelectrodes in different concentrations of NO₃^- (0.1 mmol L^-1, 1 mmol L^-1 and 10 mmol L^-1, respectively). The results were as follows. The absorption of NO₃^- by the roots made the membrane potential depolarized, and then repolarized. The magnitude of depolarization increased with the increasing of NO₃^- concentrations and the average depolarization were 7 mV, 11 mV and 21 mV under the concentrations of 0.1 mmol L^-1 NO₃^-, 1 mmol L^-1 NO₃^- and 10 mmol L^-1 NO₃^-, respectively. Repolariztion appeared 20 minutes after the treatment of 0. 1 mmol L^-1 NO₃^- while it did only after the NO₃^- was withdraw in the treatment of 1 mmol L^-1 NO₃^- and 10 mmol L^-1 NO₃^-. Among the four rice cultivars tested, Yangdao 6 was most sensitive to NO₃^- with its higher level of depolarization and less time to reach the maximum of membrane potential, while Nongken 57 was less sensitive to NO₃^- with its lower level of depolarization and more time to reach the maximum of membrane potential. Siyou 917 and Shanyou 63 exhibited the similar manner on the two aspects. This suggested that Yangdao 6 has the strongest capability to take up NO₃^- while Nongken 57 has the poorest absorption of NO₃^-. Besides, hyperpolarization followed by depolarization was found in parts of rice roots during the absorption of NO₃^-. The results obtained in this experiment implied that response of electropotentials of cell membranes to NO₃^- could be a feasible way to the study of nitrate nutrition in rice plants.

Abstract:Different P-solubilizing microbes can live in media containing different phosphorous sources. The author compared four strains, namely P17, Y3, F4, and P10, in phosphorus-dissolving mechanism and phosphorus-solubilizing ability. Results show that bacteria, fungus, and yeast play important roles in phosphorus-solubilization. Such artificial phosphates as aluminum phosphate, iron phosphate, calcium phosphates can be dissolved by yeast and mildew easily. Strain Phosphobacteria P17 (Bacillus megaterium) could dissolve phosphorus from phosphate rock powder from Huangmailing of Hubei Province easily;while yeast Y3 could improve solubility of calcium phosphate the most significantly among the four strains examined. They demonstrated different predominance in solubilizing phosphorus. The results also show that different strains of P-dissolving microbes can accelerate solubilization of phosphorus to a varying extent, which reveals that different chemical bonds have different effects on solubilization of phsphates and phosphate rock powder varied in solubility. Acids, acid phosphatase, and alkaline phosphatase have synergic effects on phosphate dissolution. Phosphatase could utilize substrates containing such organic phosphates as calcium phosphate, and Strain phospobacteria P10 produced the highest phosphatase activity among the four strains. Activities of acid phosphatase and alkaline phosphatase vary with P-solubilizing microbes. When growing in medium containing NH₄H₂PO₄, and KH₂PO₄ as phosphorus sources, activities of acid phosphatase and alkaline phosphatase with Strain phosphobacteria P17, Strain phosphobacteria P10, Strain yeast Y3, and mildew F4 were low. Activities of acid phosphatase and alkaline phosphatase were high in medium containing such hard-to-dissolve phosphates as calcium phosphate, aluminium phosphate, iron phosphate. The results show that in conditions short of phosphorus, acid, acid phosphatase and alkaline phosphatase help phosphorus-solubilizing microorganisms dissolve phosphorus more easily.

Abstract:In this research, calcareous purple soil deficient in Fe was used for potexperiment. Three strains of Bradyrhizobium Spr3-5, Spr3-7, Spr4-5 and gusA-and celB-labeled strains gusA 3-5, gusA 3-7, gusA 4-5, celB 3-5, celB3-7, celB 4-5 were selected inoculate T ianFu 9 peanut. Root nodule formed by gene marker strains would have color reaction with the test reagent. This characteristic can be used to detect effect of Fe fertilization and its application rate on effectiveness and competitiveness of the peanut Bradyrhizobium symbiosis. Results show that in calcareous purple soil deficient in available Fe, spraying of FeSO₄·7H₂O solution, inoculation of Bradyrhizobium or combination of the two could all promote symbiotic nitrogen fixtion and competitive ability of peanut Bradyrhizobium in nodulation, but the effect was the best with the combination, followed by inoculation and then Fe application. The effect of spraying 0.2% FeSO₄·7H₂O solution was much better than that of spraying 0.3% FeSO₄·7H₂O solution. Plant total nitrogen content and total chlorophyll content, which are both important indices of sym biotic nitrogen fixation, showed extremely significant correlations with peanut yields, with correlation coefficient being 0.763 and 0.795, respectively. Results of the test with either gusA or celB labeled strains were almost the same. The nodulation rate of the three labeled Bradyrhizobium strains, Spr3-7, Spr4-5 and Spr3-5 was averaged to be 79.46%, 75.62% and 74.41%, respectively. Interms of effectiveness and competitiveness, Strain Spr4-5 took the lead and was followed by Spr3-7 and Sp3-5 in the end.

Abstract:Effect of kieselguhr on enantioselectivity of enzymatic hydrolysis of chiral dichlorprop methylester (2,4-DP) has been specifically studied by chiralgas chromatography. The results show that the adsorption of lipase on kieselguhr greatly enhanced enantioselectivity of hydrolysis of 2,4-DP with ER increasing from 1.58 to 5.31. It triggered changes in conformation of the enzyme, thus affecting the microenvironment of active sites, which may be the major reason of enhanced enantioselectivity of enzymatic reaction. Due to adsorption on kieselguhr, lipase became harder to combine with R-2,4-DP and the reaction rate of hydrolysis decreased. On the other hand, it was easier for S-2,4-DP to get close to the active sites of lipase, so the rate in 2 creased. In addition, adsorption of the pesticide on kieselguhr decreased "free pesticides", which also enhanced the enantiose-lectivity of hydrolysis of 2,4-DP.

Abstract:Much improvement has been made to the method of ninhydrin colorimetry for determination of soil protease activity. The major improvement were:introducing Ca²⁺ as protease activator, and lead acetate and sodium oxalate-acetic acid as precipitator, and using antihemorrhagic vitamin coupled with potassiumiodate to improve sensitivity and stability of the ninhydrin colorimetry in quantifying the amino acid. The buffer systems of incubation and measurement were also adjusted for better performance of the ninhydrin colorimetry. Comparison between the modified method and the widely used method of Folinphenol colorimetry was made in determination of protease activity using three different soils (Fluvo-aquic soil, yellow-brown earth and red soil) and found that the modified method is much better than the Folinphenol colorimetry for neutral and alkaline soils.

Abstract:This paper attempts to review research work conducted on Hong Kong soils, including soil classification, soil fertility, and soil environmental protection. It is hoped to provide some insights into rational use of the soil resource, ecological and environmental protection, and sustainable development of modern societ ies for other areas of China, which are also undergoing rapid economic development. In order to rationalize exploitation of the land resource in Hong Kong, it is important to conduct systematic research covering soil genesis, soil taxonomy, soil characteristics, soil spatial distribution and variable pattern, and to establish soil information (including soil database and soil atlas) and service system. Furthermore it is also essential to acquire a sound knowledge of the geochemical background of harmful and beneficial trace elements in Hong Kong soil. This should include environmental biogeochemistry of persistent organic pollutants (POPs) for assessment of their potential risks to the ecology and human health. Based on these studies, a long-term workstation for Hong Kong soils can be established for assessing and forecasting the soil environmental quality in Hong Kong. In addition, it is necessary to form a risk assessment system and a remediation technology system for contaminated soil in Hong Kong.

Abstract:阿特拉津[2-chloro-4-(ethylamino)-6-(isopropylamino)-1,3,5-trazine],又名莠去津,是一种广泛使用的三嗪除草剂,其作用方式是破坏植物体中叶绿体光系统Ⅱ(PSⅡ),主要用于玉米、高粱和甘蔗田杂草的防除.该除草剂在世界范围内使用已经40多年,但由于其溶解性较好,迁移率较高,残留期长,在世界上许多地区引起土壤和地下水的污染,从而引起许多国家政府和科学家的重视.随着我国农业的发展和阿特拉津在我国的推广使用,阿特拉津所带来的环境问题也日趋严重,已经造成了许多重大损失和环境污染^[1～5].

Abstract:土壤结构特征决定了土壤的主要物理性能,并影响着土壤生态系统内的许多功能,土壤结构的三维结构透视及其定量分析是认识土壤结构和研究土壤结构与功能关系的前提.自20世纪30年代,奥地利学者库比纳开始使用生物显微镜、偏光显微镜和双目实体显微镜,研究土壤生物、土壤中的结晶形成物、土壤的结构和孔隙,显微观测与探测技术的每一次进步都被应用到土壤微结构的研究,产生了土壤学的一支独立学科—土壤微形态学^[1～7].但是,原状土壤样品的镜下观测需要复杂的前处理,观察的现像多数为二维图像,并且需要很多定性的描述和解译才能相互交流和理解,从而限制了土壤微形态学的应用和发展.

Abstract:植物体内有机酸含量分析是近几年来研究的热点,尤其是在逆境生理方面.果实中有机酸种类与含量也是衡量果实品质的重要指标.目前测定有机酸的方法通常包括气相色谱法、高效液相色谱法和离子色谱法,其中气相色谱法(GC)测定有机酸时,常因酸的沸点较高、不易气化而需要先对其衍生再进行测定,方法比较繁琐;离子色谱法(HPIC)是近来应用较多的测定植物体内有机酸的方法^[1,2],可以同时测定溶液中的有机酸根离子和无机阴离子,如NO₃^-、Cl^-、PO₄^3-等,并且样品前处理简单^[3～5],但大量无机阴离子的存在通常增加了低含量有机酸的检测难度;与之相比较,高效液相色谱法(HPLC)测定有机酸的方法比GC法简单^[6,7],但也存在pH、流动相的选择等方面的问题, 尤其是在测定十几种以上的有机酸时更为明显.

Abstract:自相似和分形是许多自然事物和现象的客观特征之一^[1].土壤是一种具有自相似结构的多孔介质,因此可以利用分形几何学来研究土壤的性状特征.研究者可以通过分形维(分维)来描述、刻画土壤颗粒的粒径及孔隙分布状况,由此可进一步研究土壤的其他物理化学性状及其对周边生态环境的指示意义^[2～6].

Abstract:国外长期定位试验已有150a历史,积累了许多资料并解决了许多理论和实际问题.国外的资料可供借鉴,但与我国情况还有较大区别.为此建立我国长期定位试验点,研究我国自然条件下长期施肥对土壤肥力、作物产量和生态环境影响尤其重要.由于种种原因,我国保存下来的长期试验点很少.本文研究的长期试验地已有15a长期施肥历史,在我国像这样长时间布置完整的长期试验不多.为此,本文采集我国潮土农田生态系统中养分平衡长期试验中不同施肥处理小区土壤,着重研究长期不同施肥处理条件下氮素养分内循环中的矿化作用和硝化作用过程及其影响因素.

Abstract:在控制外源输入的情况下,底泥内源营养盐的释放与水体富营养化之间的关系已引起了人们的浓厚兴趣^[1,2].为了解沉淀物释放的机理,研究者们开展了一系列的野外调查和实验室模拟试验工作^[3～6].从掌握的文献看,模拟试验大多数是底泥释磷^[7～9]及其相关性研究^[10,11],而对底泥释氮,尤其是河流底泥释氮特征的模拟试验研究较少^[12].淮南地处淮河下游,据环保部门提供的资料显示,近10年来,淮河(淮南段)水体一直受NH3N含量超标和富营养化的困扰.

Abstract:土壤微生物和酶是土壤生物化学特性的重要组成部分,在营养物质转化、有机质分解、污染物降解及修复等方面起着重要的作用,是评价土壤质量的重要指标之一,成为近年来土壤学界研究的热点^[1～5].覆盖栽培能改变土壤的温度、湿度等环境物理因素^[6～10],必然导致土壤化学性质和作物生物学性状的变化.在土壤微生物和酶研究方面,塑料地膜覆盖栽培已有很多报道^[11,12],而液体地膜(也称多功能可降解液体地膜)是一种新开发出的高分子有机化合物,兑水喷施后,可在土壤表层形成一层很薄的固化膜,关于液体地膜覆盖对土壤微生物和酶的影响尚少见报道.