氟啶胺对土壤中蔗糖酶活性及呼吸作用的影响

使用农药控制作物害虫和疾病可提高农业生产力, 然而农药的使用对土壤造成的污染已成为巨大且日益严重的问题。重复、广泛使用的农药进入土壤影响土壤生物、生物代谢及其生物活性, 已成为农业生态环境重要的研究内容。为了更好地了解氟啶胺对土壤微生物活性和土壤质量等潜在环境危险, 采用实验室模拟的方法研究了氟啶胺农药残留动态, 以及氟啶胺对土壤呼吸强度、蔗糖酶活性及其动力学和热力学特征参数的影响。结果表明: 高剂量(100 mg·kg^-1)氟啶胺在土壤的降解速率常数最大, 氟啶胺在土壤中的半衰期范围为0.38~0.59 d。高剂量(50 mg·kg^-1、100 mg·kg^-1 和1 000 mg·kg^-1)氟啶胺对土壤蔗糖酶表现出不同程度的抑制作用; 低剂量(1 mg·kg^-1、5 mg·kg^-1)处理表现为抑制-激活-抑制作用, 且波动范围较大; 10 mg·kg^-1 氟啶胺对土壤蔗糖酶前期表现为抑制、后期表现为激活作用, 波动范围较大。不同浓度氟啶胺胁迫下蔗糖酶促反应的Michaelis 常数(K_m)和最大反应速率(V_max)发生改变, 但变化不大。土壤中氟啶胺浓度为1 mg·kg^-1 时蔗糖酶所需的活化能(E_a)比CK 高, 其他浓度都低于CK; 5 mg·kg^-1、10 mg·kg^-1、50 mg·kg^-1、100 mg·kg^-1 和1 000 mg·kg^-1 所需的活化焓变(ΔH)随氟啶胺的浓度降低而变小; 在相同温度下蔗糖酶的活化熵变(ΔS)表现为: 1 mg·kg^-1G)变化差异较小; 320~330 K (开氏温度)时最大速度常数(Q₁₀)最大, 而290~300 K 时Q₁₀ 较小。低剂量氟啶胺对土壤微生物呼吸作用的影响表现为随时间变化呈现抑制-激活趋势, 高低剂量表现为抑制作用。土壤微生物的呼吸活性因氟啶胺的加入而产生波动。本研究结果有助于进一步分析研究受农药污染土壤的质量和酶活之间的相关性。     

饲粮精粗比对瘤胃内纤维消化动力学参数的影响

用三头瘘管牛、三种精料水平的饲粮(其精料比分别为:5％、40％和75％),按3×3拉丁方设计,测定了放置在瘤胃内的尼龙袋中的氨化麦秸粉在8—96小时间的中性洗涤纤维的残留率。按照 Waldo 及 Mertens 的纤维消化动力学模型配合回归曲线,以检验饲粮的不同精粗比对瘤胃内纤维消化动力学参数的影响。同时用铬媒染纤维法测定了瘤胃食糜的流通速度常数(Kp)。结果表明:①瘤胃内饲料纤维的消化动力学参数受饲粮精料比的影响,消化停滞期 L 有随精料比的增加而延长的趋势。消化速度常数(Kd)和可消化度(PED)在低、中(5％、40％)精料比水平间差异不显著,而高(75％)精料水平与低中精料水平比,Kd 和 PED 有显著的减少。在限量饲喂的情况下,各精料水平间,Kp 的差异不显著,但高精料水平的 Kp有降低的趋势。②在为体重1.7％的进食水平下,饲料纤维在瘤胃内的有效消化度(EED),有随精料水平增加而降低的趋势。③使用尼龙袋法,不同时间点的纤维残留率(Rt)对 EED 的线性回归,以 R_(48)对 EED 的相关最好(r=0.82)。     

ER流体的动力学特性研究

基于粘性阻尼和回滞阻尼组成的阻尼模型，对电流变（ER）流体的动力学特性进行了研究。应用迭代摄动法讨论了含有ER流体振动系统的非线性频谱，给出了带有ER流体阻尼器梁结构的计算结果。并应用Newmark数值积分方法分析了带有ER流体阻尼器梁结构的多自由度振动系统在不同电场强度和激励频率作用下的位移响应情况。结果表明，系统的刚度和响应的变化可以通过外加电场强度来控制，随着电场强度的增加，响应幅值减小且结构刚度变大。     

几种磷矿粉中磷和钙溶出动力学特性

采用间歇实验方法,研究4种磷矿粉在1M NH4OAc(pH4.8)酸性溶液中磷和钙溶出动力学规律,结果表明:磷矿粉中磷的溶出分为2个阶段,0～30min为快反应过程,30min后为慢反应过程,它能较好地符合Elvoich方程,磷的溶出速率(b)与枸溶性磷含量有较好的相关性,主要受磷矿粉中SiO2和碳酸钙含量的影响,枸溶性磷含量愈高,磷的溶出速率愈大,溶出磷的浓度也愈高。磷矿粉中钙的溶出也符合Elvoich方程,且与游离的碳酸钙含量有关,与其他磷矿粉不同,在PR1中钙的溶出浓度较高,很可能来自于碳酸钙的溶解。因而,磷矿粉不仅可以提供磷素营养,还提供植物生长所需的钙素营养。     

Synchrotron SAXS study on the micro-phase separation kinetics of segmented block copolymer

The phase transition behavior and isothermal micro-phase separation kinetics of polyester-based thermoplastic elastomer were studied using the synchrotron X-ray scattering (SAXS) method. The structural changes occurring during heating period were investigated by determining the changes of the one-dimensional correlation function, interfacial thickness and Porod constant. Based on the abrupt increases of the domain spacing and interfacial thickness, a major structural change occurring well below the melting transition temperature is suggested. Those changes are explained in terms of melting of the thermodynamically unstable hard domains or/and the interdiffusion of the hard and soft segments in the interfacial regions. SAXS profile changes during the micro-phase separation process were also clearly observed at various temperatures and the separation rate was found to be sensitively affected by the temperature. The peak position of maximum scattering intensity stayed constant during the entire course of the phase separation process. The scattering data during the isothermal phase separation process was interpreted with the Cahn-Hilliard diffusion equation. The experimental data obtained during the early stage of the phase separation seems to satisfy the Cahn-Hilliard spinodal mechanism. The transition temperature obtained from the extrapolation of the diffusion coefficient to zero value turned out to be about 147±2°C, which is close to the order-disorder transition temperature obtained from the Porod analysis. The transition temperature was also estimated from the invariant growth rate. By extrapolating the invariant growth rate to zero, a transition temperature of about 145±2°C was obtained.     

Comparison of Arsenic and Phosphate Uptake and Distribution in Arsenic Hyperaccumulating and Nonhyperaccumulating Fern

Abstract

Uptake of arsenic (As) and its distribution in Chinese Brake fern (Pteris vittata L.), an As hyperaccumulator, and Boston fern (Nephrolepis exaltata L.), a nonhyperaccumulator, in the presence of phosphorus (P), were characterized by employing a hydroponic experiment with a complete three-factorial design. Two levels of As (100 and 1000 µM) and four levels of P (0, 100, 500, and 1000 µM) were used in this study. Arsenic uptake rates on the basis of root fresh weight for the two ferns were similar at low As concentration (100 µM). At high As concentration (1000 µM), however, As uptake rates (373–987 nmol g^?1 f wt h^?1) of P. vittata were significantly greater than those of N. exaltata (164–459 nmol g^?1 f wt h^?1). In both ferns, addition of P reduced their As uptake rate as well as accumulation. Pteris vittata had a greater As TF (Translocation factor = concentration ratio of fronds to roots) than N. exaltata. On the contrary, N. exaltata displayed a greater P TF than P. vittata. As a result, high P/As ratio was observed in the roots of P. vittata, whereas high P/As ratio was observed in the fronds of N. exaltata. The study illustrated that As hyperaccumulation by P. vittata may be facilitated by its high As influx rate and its high molar P/As ratio in the roots resulting from both high As TF and low P TF.     

设施土壤中三唑酮降解动力学研究

经25℃下培养1个月,采用GC/MS定量监测设施土壤和无菌土壤中三唑酮和降解产物三唑醇的含量变化。结果表明设施土壤中三唑酮的降解符合热力学方程,半衰期为15.2 d,无菌土壤处理后三唑酮的半衰期为39.4 d。土壤中降解产物三唑醇有立体选择体,在设施土壤中三唑醇的对映体选择值(EF)为4,无菌土壤中三唑醇的EF值为2。三唑醇的降解符合一元三次方程,设施土壤中三唑醇在第7 d达到最高点后含量逐步降低,无菌处理土壤中三唑醇含量最高点出现在第14 d。     

交联淀粉微球对对硝基苯酚的吸附行为及机理研究

以可溶性淀粉为原料,N,N′-亚甲基双丙烯酰胺为交联剂,采用反相悬浮聚合得到了一种交联淀粉微球（CSM）,研究了CSM对对硝基苯酚（p-NP）的静态吸附行为,测定了吸附等温线,分析了吸附热力学性质和动力学特征,并用红外光谱仪和X射-线衍射仪对CSM吸附p-NP前后对照分析,探讨吸附机理。结果表明,在研究范围内,CSM对p-NP的吸附等温线同时符合Langmuir等温方程和Freundli-ch等温方程;在不同温度下,CSM吸附p-NP的吸附焓变（ΔH）、熵变（ΔS）、吉布斯函变（ΔG）均为负值,吸附过程自发、放热,且为焓推动作用。     

杨树落叶对Cd（2＋）的吸附等温线和动力学研究

[目的]研究杨树落叶作为一种价廉、高效的重金属吸附剂的可行性。[方法]用杨树落叶吸附模拟废水中的Cd2＋,研究不同环境条件如重金属离子初始浓度、生物吸附剂的量、溶液温度和溶液pH对吸附效果的影响。[结果]Cd2＋的初始浓度从50 mg/L增大到500mg/L时,落叶对Cd2＋的最大吸附量从20.0 mg/g增长到201.2 mg/g。当溶液的pH从3增大到11时,落叶对Cd2＋的吸附量逐渐从30.9 mg/g增大到40.5 mg/g。分别用Langmuir和Freundlich 2种吸附等温线模型对Cd2＋的吸附过程进行拟合;用一级动力学模型、二级动力学模型和内扩散模型对Cd2＋的吸附过程进行动力学研究。结果显示,Langmuir吸附等温线模型和二级动力学模型适合描述树叶对Cd2＋的吸附过程。[结论]落叶对Cd2＋具有一定的吸附能力,是较为理想的重金属离子吸附剂。     

红壤和黄土对铊的吸附行为研究

利用一次平衡法,研究红壤和黄土对Tl＋吸附的热力学和动力学过程。结果表明,在试验所采用的Tl＋浓度范围内,红壤和黄土对Tl＋的吸附量均随着加入浓度的增加而增加,但是黄土对Tl＋的吸附能力明显高于红壤。2种土壤对Tl＋的吸附等温线用Langmuir方程拟合效果最好。红壤吸附Tl＋很快,20min左右基本达到平衡。而随着初始浓度的提高,黄土对Tl＋的吸附达到吸附平衡所需的时间增长,在最大浓度（15mg/L）时约120min达到吸附平衡。2种土壤对Tl＋吸附动力学过程用双常数方程拟合效果最好。