太湖地区水耕人为土中漂白层的成因探讨

采集太湖地区4个具有漂白层的水耕人为土剖面(E-A1、E-A2、E-A3、E-A4)及1个发育于相同母质上的一般水耕人为土剖面作为参照(Ref),描述了土壤剖面的形态特征,分析了土壤颗粒组成、黏粒矿物组成、铁氧化物以及大量和微量元素等,并探讨了漂白层成因。5个剖面土壤颗粒组成以粉粒为主,在60%~75%之间,且剖面中各层次变异系数较小,小于10%;大量元素和微量元素在剖面各层次间变异系数也小于10%,指示漂白层与上覆和下伏土层发育在相似物质来源的土壤母质上;而E-A1剖面漂白层中较高的粉粒含量(75.04%)、较大的中细粉粒和中细粉粒/粗粉粒比值的变异系数(38.05%、61.85%)表明该剖面母质具有不均一性。说明E-A2、E-A3、E-A4、Ref剖面土壤性质的变化主要是由于成土作用形成的,而E-A1剖面土壤的性质变化除受成土作用影响外,还受沉积环境的影响。E-A2、E-A3、E-A4剖面的漂白层中蒙脱石和蛭石、粉粒和粗粉粒、SiO2、CaO、Zr等含量高于上下土层,而水云母和绿泥石、游离铁、Al2O3、Rb、Li、Ba、稀土元素(Rare earth element,REE)等则相反;同时,参照剖面亦有与E-A2、E-A3、E-A4剖面类似的特点,只是漂白作用出现在耕作层,不能定义为漂白层;而E-A1剖面的部分性质则显示出空间上的不一致性,其粉粒含量并非漂白层最高,而是随剖面土层深度向下越来越大。这些变异表明,太湖地区水耕人为土漂白层的形成,可以由黄土性泻湖相沉积物经过水耕过程中水分的周期性淹水和排干,通过机械淋洗和活性铁的淋溶而形成(剖面E-A2、E-A3、E-A4),也可以是母质沉积的过程中受湖水水面升降,导致机械淋溶,然后水耕过程叠加活性铁的淋溶而形成(剖面E-A1)。     

不同水稻种植模式对氮磷流失特征的影响

过量施用化肥造成的氮、磷流失已成为农业面源污染的主要污染源。为探究不同种植模式对氮、磷流失的影响,采用大田试验,研究比较了常规种植、绿色蛙稻和有机蛙稻3种水稻种植模式下稻田生态系统的田面水氮、磷浓度特征规律,以及径流、渗漏的氮、磷流失特征和产量差异。结果表明,3种水稻种植模式中,田面水总氮(TN)平均浓度为:常规种植绿色蛙稻有机蛙稻,分别为18.87 mg-L-1、8.98 mg-L-1和8.20 mg-L-1。与常规种植模式相比,绿色蛙稻模式和有机蛙稻模式在整个水稻季中的TN总流失负荷分别减少15.27%和25.76%。径流流失负荷为:绿色蛙稻常规种植有机蛙稻,氮的主要形态为铵态氮(NH4+-N);渗漏流失负荷为:常规种植绿色蛙稻有机蛙稻,氮的形态以硝态氮(NO3--N)为主。田面水总磷(TP)平均浓度为:有机蛙稻绿色蛙稻常规种植,分别为0.82 mg-L-1、0.64 mg-L-1和0.37mg-L-1。总磷(TP)总流失负荷为:有机蛙稻绿色蛙稻常规种植,总流失负荷占施磷量的比例为:绿色蛙稻常规种植有机蛙稻,并且以溶解性磷(DP)为主。3种模式下水稻产量为:常规种植有机蛙稻绿色蛙稻,与常规种植模式相比,绿色蛙稻模式和有机蛙稻模式分别减产19.33%和8.51%。研究结果表明,有机蛙稻和绿色蛙稻模式能够有效地控制水稻田中氮、磷流失,但会造成水稻减产。由于有机蛙稻模式要求种、养条件更高,因此有机蛙稻模式下的产品往往品质最好,经济效益最高。     

疏浚底泥土地投放中活性磷的下移规律

通过原状土柱淋洗试验研究了运河 (杭州段 )疏浚底泥土地投放后磷在土层中的分布规律。结果表明 ,在连续淋洗的条件下 ,疏浚底泥的土地投放并未显著提高淋洗液中活性磷的浓度 ;但在干湿交替的淋洗条件下疏浚底泥中活性磷的下移作用却相当明显。疏浚底泥土地投放后显著提高了表层1 5cm厚的土层中Olsen P含量 ,而 1 5cm以下土层中的Olsen P的增加并不明显 ,原因可能与疏浚底泥中有机酸的释放及土壤pH的剖面变化特征有关。干湿交替等环境因子的变化对底泥活性磷的下移程度产生更大的影响 ,且底泥用量越大 ,其潜在的影响可能越持久。     

Biodegradation of leaf litter in the warm humid tropics of Kerala, India

Ex situ biodegradation of Mangifera indica L, Artocarpus heterophyllus.Lamk. and Anacardium occidentale L. leaf litter were examined in the warm humid tropics of southern Kerala adopting the standard litter bag technique. The time taken for the decay varied with the species and it followed the order Mangifera >Artocarpus>Anacardium. Weight loss accorded a linear decline and was better correlated with soil moisture than temperature. The half-life values were 3.2, 3.4 and 4.0 months for Anacardium, Artocarpus and Mangifera, respectively. Soil faunal and floral activities were monitored during the decay and the earthworms, fungi and bacteria proved the chief degraders of the intact litter. Actinomycetes were active during the final stages. The variations in decay rates of the three species are attributed to the differences in the litter quality and activity of the decomposer organisms in soil. NPK dynamics revealed temporary phases of immobilization for nitrogen and phosphorus before final release, while potassium recorded a continuous release. Decomposition apparently improved the available NPK status of soil, potassium being liable to leaching was soon lost from the surface soil.     

砂质土壤磷素的组成特点与释放规律研究

砂质土壤磷素主要以可提取态形式积累,有很高的释放潜力。该类土壤磷素的释放受土壤pH、土水作用时间和土壤溶液化学组成等的影响。土壤酸化、土壤溶液中Na+浓度的提高及土壤与水的作用时间增加可促进土壤磷素的释放。用淋洗方法和平衡提取等2种方法对土壤磷素的释放评价表明,淋洗方法测得的P量较小,可代表土壤短期内P释放强度;而平衡提取法提取的P数量较大,可代表土壤P长期释放的容量。     

粉煤灰草坪基质的渗滤特性及其环境效应

利用人工模拟降雨装置,结合ICP-MX质谱分析测试技术,深入探讨不同降雨强度、降雨时段和覆盖条件下,粉煤灰草坪基质渗滤特性及其环境效应。研究结果表明:在相同雨强和时段条件下,有草坪覆盖的基质其渗滤液离子浓度和离子流失总量均低于裸露基质。在覆盖状况和时间段相同条件下,降雨强度对覆盖处理中的渗流离子浓度影响不很显著,但在裸露处理中则表现较为明显,雨强为90 mm h-1时大部分离子,尤其是草坪覆盖处理中的离子流失量达最大值。时段对渗漏特性也有一定的影响,总的来说草坪覆盖处理中离子浓度随时段的增加有降低趋势(A l除外);裸露处理中除K、Ca外,其余元素随时段增加浓度呈现增大趋势。此外,所有渗滤液均达到了国家规定的三类水质,部分甚至达到二类水质,不会对人类饮用水造成污染。     

灌溉水质对土壤水盐动态的影响

本文研究了灌溉水质对土壤水盐动态和牧草生长的影响。灌溉水含盐量分别为１００、１５００和３０００ｍｇ／Ｌ，设有６个试验处理。在高含盐水灌溉期间，盐分在土壤剖面中累积，低含盐水灌溉和冬季降雨期间部分土壤盐分被淋洗。由于盐分累积与淋洗反复进行，以及弱透水层的存在，可溶盐在６０－９０ｃｍ土层明显增加，土壤溶液钠吸附比（ＳＡＲ）随灌溉水含盐量增加而增高，牧草茎叶中的盐分亦随之而变化。当灌溉水含盐量达到１５０     

Carbohydrate and amino acid composition of dissolved organic matter leached from soil

Low molecular weight organic substances (LMWOS) in soil and soil solution include mainly amino acids, carboxylic acids, and carbohydrates. Due to their high bioavailability they play a crucial role in the cycles of C and nutrients in soils. The variety of soil processes that involve LMWOS requires identifying their composition to elucidate reactions and transformations. In most studies, LMWOS are extracted under artificial conditions, e.g. batch experiments, which may overestimate the actual concentrations. This study measures the composition of carbohydrates and amino acids in solution of a Haplic Luvisol leached in a column experiment. A combined system for simultaneous leaching and blowout of CO₂ was used to estimate LMWOS decomposition. ¹⁴C-labeled glucose was added as a highly sensitive tracer to control the efficiency of the LMWOS extraction by leaching and to estimate LMWOS decomposition during leaching. High performance liquid chromatography (HPLC), optimized for soil extracts, was used to analyze LMWOS composition. For HPLC optimization, different preparations of leached solutions (filtration vs. centrifugation, and drying vs. no-drying) were compared. For sugar determination, drying had no influence on the solution concentrations. In contrast, amino acid concentrations significantly decreased by drying LMWOS eluted substances. Combining the HPLC identification of eluted substances with ¹⁴C tracer application revealed that about 5% of the glucose could be leached unchanged within 786 min (13.1 h), whereas about 84% remained in the soil, 9% were decomposed to CO₂, and 2% were transformed to other LMWOS and recovered in the soil solution. The total amino acid concentration (TAC) in soil solution was about 8.2 μmol l⁻¹, dominated by alanine (14.4% of TAC), glycine (13.4%), glutamic acid (9.9%), serine (9.4%), and leucine (9.3%). The total carbohydrate concentration was about 2.4 μM, dominated by glucose (29.9%), glucuronic acid (26.8%), and galacturonic acid (17.3%). Ratios of hexoses to pentoses, amino sugars glucosamine to galactosamine, and neutral sugars to uronic acids were determined. All three parameters pointed to the dominant influence of plants as the source of LMWOS in the leached soil solution. Within the small contribution of microorganisms, bacteria dominated over fungi. These used biomarker ratios as well as LMWOS concentrations differed widely from the ones obtained with conventional batch extraction. More research is necessary to evaluate the application of these biomarkers to soil solutions.     

Modelling nitrate and bromide leaching from sewage sludge

A deterministic model for assessing the risk of groundwater contamination by nitrate from land-based sludge disposal was evaluated. A controlled large-lysimeter experiment was set up to monitor movement of nitrate through soil. Four large lysimeters of 900 mm length were packed with Manawatu fine sandy loam (a Dystric Fluventric Eutrochrept), on top of which 200 mm of municipal sewage sludge was applied. One of the lysimeters was planted with pasture (Lolium perenne and Festuca arundacea), one with a willow tree (Salix sp. ‘Tongoio’), another with a poplar tree (Populus sp. ‘Kawa’), and one was left bare. Bromide was used as a conservative tracer. Movement of bromide and nitrate was analysed in the effluent from the base of the lysimeters.The processes of water and nutrient transport were modelled using a mechanistic scheme based on Richards’ equation for water transport and the convection–dispersion equation (CDE) for nutrient transport. These equations were both linked to a sink term for plant uptake. The model simulated well the transport of water and movement of bromide in the four different lysimeters. The agreement between measured and simulated nitrate leaching was also reasonable considering the simplified model. Uptake of nitrogen by trees reduced the quantity of nitrogen available for leaching. The model could aid development of sustainable management of land-based sewage sludge disposal in terms of nitrate leaching. The next step will be to further develop the model for heavy metal movement, as heavy metals are common co-contaminants of sewage sludge.     

吉林省中部不同亚类、不同母质黑土中硼、钼的分异变化规律

本文通过野外调查采样分析研究了吉林中部不同亚类黑土中硼、钼的含量及垂直分布规律,分析了成土母质、成土过程、成土环境对各微量元素含量及分布的影响。结果表明:红土母质中全钼及有效钼含量均高于黄土母质,而黄土母质中全硼含量较高。全硼在草甸黑土中表现出很强的生物富集特征,其余各剖面表现出较明显的淋溶特征;有效硼表现出生物累积并且从上到下逐渐减小,与有机质之间呈显著正相关。全钼在草甸黑土、德惠典型黑土中有淋溶作用较弱的特点,在长春地区典型黑土中为表层富集,淋溶作用较强的特点;有效钼与全钼变化规律一致,白浆化黑土中有效钼的表层富集和淋溶程度最强。