玉米农田土壤呼吸作用动态与模拟研究

利用动态密闭气室法(Licor-6400-09)，对锦州玉米生长季(5～9月)农田土壤呼吸作用动态及其影响因子进行连续两年的野外动态观测，分析表明，在植株尺度上，玉米地土壤呼吸作用存在明显的空间异质性，较高的土壤呼吸速率通常出现在靠近玉米植株的地方。玉米地土壤呼吸作用的日变化为不对称的单峰型曲线，最小值和最大值分别出现在6:00～7:00和13:00左右。2005年玉米生长季土壤呼吸速率均值为3.16 µmol CO2 •m-2•s-1，最大值为4.77 µmol CO2 •m-2•s-1，出现在7月28日，最小值为1.31 µmol CO2 •m-2•s-1，出现在5月4日。 植物根系生物量的分布格局是影响土壤呼吸作用空间异质性的关键因素。土壤呼吸作用与根系生物量呈显著的线性关系，而土壤湿度、土壤有机质、全氮和碳氮比对土壤呼吸作用空间异质性的影响并不显著。在土壤呼吸作用日变化中，土壤呼吸速率(SR, µmol CO2 •m-2•s-1)与10 cm土壤温度(T, ℃)均呈显著的指数函数关系 。在季节尺度上，参数α和β是波动的，玉米净第一性生产力(NPP, g •m-2 •d-1)和生物量(B, g •m-2)分别为影响参数α和β季节性波动的主导因素。鉴于此，建立了方程 用以模拟土壤呼吸作用的季节变化。土壤温度、NPP和生物量共同影响着玉米生长季土壤呼吸作用的季节性变化，它们共同解释了土壤呼吸作用季节变化的93%。 小时尺度上，土环中的根系生物量是影响土壤呼吸速率空间变异的关键因子，土壤呼吸速率与根系生物量呈线性关系 ;日时间尺度上，土壤呼吸速率与根系生物量线性方程中的参数α和β是波动，土壤温度是影响α和β波动的主导因素，于是得到方程 。季节时间尺度上，土壤呼吸作用可表达为 ，土壤温度、土壤湿度和玉米NPP共同驱动着玉米生长季土壤呼吸作用的时间变化和空间变异，它们可以解释玉米生长季土壤呼吸作用时空变化的74%。 通过建立土壤呼吸作用与玉米根系生物量的回归方程，对根系呼吸作用占土壤呼吸作用的比例进行了间接估算。玉米生长季根系呼吸作用占土壤呼吸作用的比例在43.1～63.6%之间波动，均值为54.5%。假定玉米果实和秸杆中的碳在收获期间没有从农田中转移走，2005年整个生长季玉米生态系统的碳收支为–1127.0 gC•m-2，碳交换速率在 0.52～-18.05 g C•m-2 •d-1 之间波动。玉米生长初期，玉米生态系统表现为C的弱碳源;玉米播种后35天一直到收获，玉米生态系统表现为碳汇。

The study of high temperature annealing of a-SiC : H films

A series of amorphous silicon carbide films were prepared by plasma enhanced chemical vapor deposition technique on (100) silicon wafers by using methane, silane, and hydrogen as reactive resources. A very thin (around 15 A) gold film was evaporated on the half area of the aSiC:H films to investigate the metal induced crystallization effect. Then the a-SiC:H films were annealed at 1100 degrees C for 1 hour in the nitrogen atmosphere. Fourier transform infrared spectroscopy (FTIR), X-Ray diffraction (XRD), and scanning electron microscopy (SEM) were employed to analyze the microstructure, composition and surface morphology of the films. The influences of the high temperature annealing on the microstructure of a-SiC:H film and the metal induced metallization were investigated.

黄土旱塬冬小麦水分利用效率及相关生理特性研究

采用Li-6400便携式光合测定系统在模拟光照条件下,通过对冬小麦叶片生理指标及其相应环境因子的测定,研究了小麦的生理指标和叶片水分利用效率的动态变化规律及其对环境因子的响应。结果表明:净光合速率日变化呈不明显的双峰曲线,蒸腾速率日变化呈明显的倒"U"型曲线,且不同生育期两者峰值出现的时间不同。拔节期环境因子对生理指标的影响要比灌浆期明显的多。光合有效辐射和CO2浓度是对净光合速率和叶片蒸腾速率影响最强烈的环境因子。在小麦整个生长过程中,温湿度对气孔导度的影响在逐渐增大,对胞间CO2浓度的影响也比较明显。小麦叶片水分利用效率的日变化呈不明显的双峰曲线,其峰值出现的时间早于净光合速率和蒸腾速率峰值出现的时间。灌浆期日平均WUE比拔节期低30.5%。小麦净光合速率、蒸腾速率和气孔导度三者之间极显著相关,叶片温度与气孔导度显著负相关。

拜耳法赤泥放射性特征及应用途径研究

赤泥是氧化铝生产过程中的工业固体废弃物,具有强碱性和高放射性两个特点。目前赤泥的处置方法主要是建设赤泥堆场，供长期堆放，尚没有对其进行大规模利用的成熟技术。 随着铝工业的发展，亟需开发赤泥处置与资源化利用的新工艺技术。本论文运用环境地球化学的理论方法，采用化学分析、选矿分离、放射性测试等技术手段，对贵州铝厂拜耳法赤泥的放射性特征进行了矿物学研究，并利用铁钛着色机理生产赤泥墙体装修材料进行了应用试验研究，指明了赤泥规模化综合利用的途径。 通过研究，得到以下主要结论： 1）初步确定了赤泥放射性元素主要来源于铝土矿原矿，并赋存于原矿残留的锆石和独居石中。 2) 贵州铝厂拜耳法赤泥所含放射性偏高，倘若利用赤泥制作建筑主体材料，需要慎重考虑。 3）探讨了不同选矿方法对赤泥放射性强度的变化情况，重选、磁选、加磁粉磁选所得赤泥组分与赤泥原样放射性相比较，没有显著性差异。采用现有选矿技术，难以达到分离富集赤泥中含放射性组分。 4）利用拜耳法赤泥中富含Fe2O3和TiO2的着色机理，加入一定量的页岩可以制得金红-褐色系列颜色的彩色墙体装修材料。采用现有烧结砖厂一般生产工艺，利用拜耳法赤泥生产烧结制品，是规模化处理赤泥的一条可行途径。 本论文的研究结果指明了赤泥可行的利用途径是用于建材领域，为制定赤泥大规模资源化利用的技术路线提供了一定的理论基础。

Influence of methanol on retention of hydrophobic organic chemicals in soil leaching column chromatography

The influence of methanol in methanol-water mixed eluents on the capacity factor (P), an important parameter which could depict leaching potential of hydrophobic organic chemicals (HOCs) in soil leaching column chromatography (SLCC), was investigated. Two reference soils, GSE 17201 obtained from Bayer Landwirtschaftszentrum, Monheim, Germany and SP 14696 from LUFA, Spencer, Germany, were used as packing materials in soil columns, and isocratic elution with methanol-water mixtures at different volume fractions of methanol (phi) were tested. Shortterm exposure of the column (packed with the GSE 17201 soil) to the eluents increased solute retention by a certain (23% log-unit) degree evaluated through a correlation with the retention on the same soil column but unpreconditioned by methanol-containing eluents. Long-term exposure of soil columns to the eluents did not influence the solute retention. A log-linear equation, log k' = log k'(w) - Sphi, could well and generally describe the retention of HOCs in SLCC. For the compounds of homologous series, logk'(w), had good linear relationship with S, indicating the hydrophobic partition mechanism existing in the retention process. (C) 2002 Elsevier Science Ltd. All rights reserved.

Prediction of soil organic partition coefficients by a soil leaching column chromatographic method

The soil organic partition coefficient (K-oc) is one of the most important parameters to depict the transfer and fate of a chemical in the soil-water system. Predicting K-oc by using a chromatographic technique has been developing into a convenient and low-cost method. In this paper, a soil leaching column chromatograpy (SLCC) method employing the soil column packed with reference soil GSE 17201 (obtained from Bayer Landwirtschaftszentrum, Monheim, Germany) and methanol-water eluents was developed to predict the K-oc of hydrophobic organic chemicals (HOCs), over a log K-oc range of 4.8 orders of magnitude, from their capacity factors. The capacity factor with water as an eluent (k(w)') could be obtained by linearly extrapolating capacity factors in methanol-water eluents (k') with various volume fractions of methanol (phi). The important effects of solute activity coefficients in water on k(w)' and K-oc were illustrated. Hence, the correlation between log K-oc and log k(w)' (and log k') exists in the soil. The correlation coefficient (r) of the log K-oc vs. log k(w)' correlation for 58 apolar and polar compounds could reach 0.987, while the correlation coefficients of the log K-oc-log k' correlations were no less than 0.968, with phi ranging from 0 to 0.50. The smaller the phi, the higher the r. Therefore, it is recommended that the eluent of smaller phi, such as water, be used for accurately estimating K-oc. Correspondingly, the r value of the log K-oc-log k(w)' correlation on a reversed-phase Hypersil ODS (Thermo Hypersil, Kleinostheim, Germany) column was less than 0.940 for the same solutes. The SLCC method could provide a more reliable route to predict K-oc indirectly from a correlation with k(w)' than the reversed-phase liquid chromatographic (RPLC) one.