不同添加剂对土壤中乙草胺吸附/解吸的影响

采用批处理恒温振荡法,利用气相色谱-质谱联用仪研究了人工添加不同吸附物质对土壤中乙草胺的吸附/解吸作用.结果表明,人工添加不同吸附物质对土壤中乙草胺的吸附强度和吸附容量不同,不同的添加剂对土壤中乙草胺的吸附懈吸作用均呈现明显的非线性关系,可用Freundlich模型描述.并且随着土壤中添加剂量的增大,吸附强度增大、吸附容量增大、所得吸附等温线的非线性也逐步增大;另外,添加剂对乙草胺的解吸迟滞作用也随添加剂含量的增高而更加明显.但是不同添加剂对土壤中乙草胺的吸附能力有明显差异,其中煤粉的吸附能力最大,其次是壳聚糖,沸石最小.     

Metribuzin mobility in soil columns as affected by urea fertiliser

Application of urea fertilisers to soils influences the soil solution characteristics and thus may affect the sorption of soil-applied herbicides. The present investigation reports the influence of urea co-application on sorption and leaching of metribuzin, a triazine herbicide. Urea application at 60 and 120 kg N ha(-1) increased metribuzin sorption in soils over that in untreated natural soil. The Kf (Freundlich adsorption coefficient) values of metribuzin for natural, 60 and 120 kg N ha(-1) treatments were 0.43, 0.46 and 0.84 microg(1 - 1/n) g(-1) ml1/n respectively. Downward mobility of metribuzin was studied in packed soil columns (300 mm length x 59 mm i.d.) at two irrigation intensities, 720 m3 ha(-1) (72 mm) and 3600 m3 ha(-1) (360 mm). After 720 m3 ha(-1) irrigation, metribuzin did not leach out of any column and was not detected in the leachate. Urea amendment slowed the leaching of metribuzin by 20 and 40% in 60 and 120 kg N ha(-1) urea-treated columns respectively. Also, following urea application, greater amounts of metribuzin were retained in the application zone. Upon increasing the irrigation intensity fivefold, urea application did not have any effect on metribuzin mobility, and its breakthrough from both natural and urea-amended columns occurred after 126 mm irrigation. However, there was a marked difference in the maximum concentration of metribuzin in the breakthrough curves obtained from natural and urea-amended columns. The study indicated that co-application of metribuzin and urea fertiliser is a safe practice as far as leaching of herbicide is concerned.     

土壤组分对广东省酸性水稻土磷吸附参数的影响

Soil components affecting phosphate sorption parameters were studied using acid paddy soils derived from basalt, granite, sand-shale and the Pearl River Delta sediments, respectively, in Guangdong Province.For each soil, seven 2.50 g subsamples were equilibrated with 50 mL 0.02 mol L-1 (pH=7.0) of KCl containing 0, 5, 10, 15, 25, 50 and 100 ng P kg-1, respectively, in order to derive P sorption parameters (P sorption maximum, P sorption intensity factor and maximum buffer capacity) by Langmuir isotherm equation. It was shown that the main soil components influencing phosphate sorption maximum (Xm) included soil clay, pH,amorphous iron oxide (Feo) and amorphous aluminum oxide (Alo), with their effects in the order of Alo ＞Feo ＞ pH ＞ clay. Among these components, pH had a negative effect, and the others had a positive effect.Organic matter (OM) was the only soil component influencing P sorption intensity factor (K). The main components influencing maximum phosphate buffer capacity (MBC) consisted of soil clay, OM, pH, Feo and Alo, with their effects in the order of Alo ＞ OM ＞ pH ＞ Feo ＞ clay. Path analysis indicated that among the components with positive effects on maximum phosphate buffer capacity (MBC), the effect was in the order of Alo ＞ Feo ＞ Clay, while among the components with negative effects, OM ＞ pH. OM played an important role in mobilizing phosphate in acid paddy soils mainly through decreasing the sorption intensity of phosphate by soil particles.     

Bending creep behavior of hot-pressed wood under cyclic moisture change conditions

This study examined the bending creep behavior of hot-pressed wood during cyclic moisture changes. Sugi (Cryptomerica japonica D. Don) specimens were pressed in the radial direction under six combinations of nominal compressive strain (33% and 50%) and press temperatures (140°C, 170°C, 200°C). Creep tests were conducted at 20°C with three cyclic relative humidity changes between 65% and 95% under 25% of short-breaking stress. The effect of moisture content (MC) change on elastic compliance and mechanosorptive (MS) compliance was investigated. The relation between MS compliance and thickness swelling was studied. The results indicated that total compliance increased over the history of cyclic moisture changes; and its behavior was closely related to the changes in MC and thickness swelling. The total compliance increased during adsorption and decreased during desorption. Elastic compliance increased linearly with MC and was dependent on press temperature and compression. With increasing MC change, MS compliance increased during adsorption and decreased during desorption. The first adsorption led to greater MS compliance than did the subsequent adsorption with the same amount of MC change. In general, the elastic parameterK _E and the MS parameterK _Mincreased with compression and decreased as the press temperature increased. The MS parameterK _M was apparently greater than the elastic parameterK _E. The MS parameterK _M increased with swelling coefficient K_SW of the hot-pressed specimen during adsorption and decreased with an increasing shrinkage coefficientK _SH during desorption.     

DOMs耦合生物质炭对土霉素的吸附行为研究

以650 ℃下制备甘蔗渣生物质炭（BC650）为研究对象,在模拟自然条件下,在BC650上负载环境中常见的溶解性有机质（DOMs）即小分子没食子酸（GA）和大分子黄腐酸（HA）,并对其性质进行表征;再以典型抗生素土霉素为目标污染物,探究外源DOMs耦合生物质炭对抗生素的吸附性能的影响。结果表明,DOMs的负载提高了生物质炭的比表面积,生物质炭的表面化学性质发生改变;预载DOMs后,生物质炭对土霉素的吸附能力明显降低,且GA负载的抑制作用较HA更为显著,就平衡吸附量而言,HA处理后其下降了10%,而GA的处理使其降低了30%,DOMs的预载对生物质炭吸附抗生素的影响可能是由DOMs处理改变了生物质炭的表面化学性质而致;DOMs负载前后生物质炭对土霉素表现出非线性吸附,氢键作用为主要吸附机制。所得结果可为生物质炭在抗生素污染控制中的实际应用提供重要的理论依据。     

硬脂酸-胱氨酸-大豆分离蛋白复合膜的机械特性和吸湿性研究

以硬脂酸作为增塑剂,胱氨酸作为交联剂制备具有一定力学性能和良好抗湿性能的大豆分离蛋白复合膜。将膜放在25℃,相对湿度为50%的干燥器中平衡两天,用质构仪测定膜的抗拉强度(TS),延伸率(E(%))。在水分活度a_w为0.10～0.90的范围内研究了复合膜在25℃的吸湿特性。吸湿速率和吸湿等温线数据分别拟合到Peleg's 方程和GAB(Guggenheim-Anderson-de Boer)模型。结果表明：大豆蛋白复合膜的TS、延伸率E(%)以及吸湿速率随着硬脂酸和胱氨酸的添加比率显著地变化。硬脂酸和胱氨酸的最佳添加比率为40∶60(w/w)(每升蛋白质溶液中加入10 g混合添加剂),此时,大豆蛋白膜的强度比原来提高2倍,并且有最佳的吸湿速率。吸湿数据和GAB 模型有很高的拟合度,拟合系数最高达0.99。     

水稻土磷环境敏感临界值的研究

采用室内测试方法研究了3组质地(粘土、重壤土和轻壤土)水稻土水溶性磷(0.01mol·L-1CaCl2-P)与土壤测试磷(Olsen-P和Bray1-P)及土壤磷饱和度的关系。结果表明,水稻土因淹水耕作,其磷释放潜力明显高于旱地土壤,水溶性磷随土壤测试磷的增加而增加。土壤测试磷及磷的饱和度与土壤水溶性磷的关系存在转折点,当土壤磷超过转折点时,土壤水溶性磷和磷的释放潜力明显增加。在好气条件下,供试水稻土磷环境敏感临界值(转折点)在Olsen-P50～75mg·kg-1、Bray1-P90～140mg·kg-1和磷饱和度21%～23%之间;在厌气条件下,供试水稻土磷环境敏感临界值(转折点)在Olsen-P35～45mg·kg-1、Bray1-P75～115mg·kg-1和磷饱和度16%～18%之间,超过临界值土壤磷素可对环境产生非常明显的负影响,不应再施用磷肥和粪肥。     

天然土壤对菲吸附行为的动态变化

选择8种有机质含量各异的土壤,考察其对菲吸附行为的动态变化特征,并利用Freundlich模型描述1、48和720h条件下菲的相分配关系。结果表明,在不同接触时间条件下,Freundlich吸附系数KF与土壤有机质含量呈显著的线性关系,8种土样吸附行为的非线性指数n随时间逐渐减小,经土壤有机碳含量校正的单点Koc*值也随时间上升。这些结果指示土壤有机质是有机污染物土壤吸附的主要汇,土壤有机质吸附位点的位能表现为非均匀分布,颗粒内部有机质吸附位点的容量更大。此外,利用差减方式得到吸附过程后段的相分配关系的非线性明显强于吸附过程前段,说明慢吸附阶段中结构致密的土壤有机质组分的影响更趋强烈疏水性有机污染物在致密有机质组份中的扩散过程很可能是慢反应发生的主要原因。     

Behaviour of bentazon as influenced by water and tillage management in rice‐growing conditions

Bentazon is a widely used herbicide in rice agroecosystems that has commonly been found in water resources. To assess how tillage and water regimes affect sorption/desorption, dissipation and leaching of bentazon in Mediterranean rice‐growing conditions, field experiments were carried out using tillage and flooding (TF), tillage and sprinkler irrigation (TS), no‐tillage and sprinkler irrigation (NTS) and long‐term no‐tillage and sprinkler irrigation (NTS7). After 3 years, the K_d values in TS were 2.3, 1.6 and 1.7 times lower than the values in NTS7, NTS and TF respectively. Greater sorption of bentazon was related to higher contents in total organic carbon and, although to a lesser extent, in humic acids and dissolved organic carbon. The persistence of bentazon was significantly greater under anaerobic (half‐life DT₅₀ = 94.1–135 days) than under aerobic (DT₅₀ = 42.4–91.3 days) incubation conditions for all management regimes. Leaching losses of bentazon were reduced from 78 and 74% in TS and TF to 61 and 62% in NTS7 and NTS respectively. The mid‐ and long‐term implementation of sprinkler irrigation in combination with no‐tillage could be considered a management system that is effective at reducing water contamination by bentazon in Mediterranean rice‐growing agroecosystems. © 2017 Society of Chemical Industry     

土壤吸附作用对土壤水分有效性的影响

围绕土壤结皮生物是否可以对夜间土壤吸附水输入产生响应展开研究。假定-1.5 MPa作为土壤水分有效性的临界值,通过观测降水后清晨和午后0~3 cm土壤含水量,分析土壤水分的有效性和空间异质性;并利用连续记录气象数据,建立表层土壤含水量与水汽压饱和差数量关系。结果表明:土壤吸附作用提高了土壤水分对土壤结皮生物的有效性,并延长了土壤结皮生物对降水脉冲的响应时段。在古尔班通古特沙漠东南部的不同部位,凝结吸附作用对沙面水分条件影响很大(特别是干旱季节),水分条件由好到坏依次为:沙垄西坡面、沙垄垄顶、沙垄东坡面和垄间低地。