不同温度、pH、水动力条件下寒旱区水库底泥中不同形态氮的释放特征模拟

为探究寒旱区水库上覆水环境条件对底泥释氮的影响,以大河口水库底泥和上覆水为试验材料,通过改变上覆水温度、pH、水动力条件,模拟研究了底泥中不同形态氮的释放特征,探讨了不同环境条件与底泥氮释放浓度之间的相关性,并用线性函数、对数函数、双曲线函数、二次函数、三次函数进行拟合。结果表明:(1)温度的升高有利于底泥氨氮、总氮的释放,但硝态氮的释放浓度随温度的升高反而减小;随pH的升高,底泥的氨氮、硝态氮和总氮释放浓度均呈减小趋势;水动力扰动加强,底泥的氨氮、硝态氮和总氮释放浓度明显增加。(2)在0.05水平(双尾)下,pH与底泥氨氮释放浓度呈显著负相关,相关系数为-0.997,水动力条件与底泥总氮释放浓度呈显著正相关,相关系数为0.999。(3)曲线拟合结果显示,pH与底泥氨氮释放浓度的关系以对数函数拟合最优,水动力条件与底泥总氮释放浓度的关系以线性函数拟合最优。

两种绿肥腐解及其碳氮养分释放动态特征

为探究长武怀豆和黑麦草两种绿肥在黄土旱塬区农田土壤中的腐解状况,应用尼龙网袋法研究了在不同氮肥条件下两种绿肥翻埋后的腐解规律碳、氮养分释放特征及其对土壤耕层有机碳、全氮影响。试验设计施氮区长武怀豆(N1B)、施氮区黑麦草(N1R)、施氮区裸地(N1CK)、不施氮区长武怀豆(N0B)、不施氮区黑麦草(N0R)、不施氮区裸地(N0CK)共6个处理。结果表明:0—105天是长武怀豆、黑麦草腐解的快速上升时期,105—238天进入缓慢腐解阶段,238—281天为中低速增长时期,试验结束时(281天)N1B、N0B、N1R、N0R的累积腐解率分别达到83.84%、82.64%、81.91%和81.04%。绿肥碳、氮均在翻埋后快速释放,其中碳在33天累积释放率达70.04%—74.13%,而氮在前15天释放较快,累积释放率为49.50%—60.04%。在0—20 cm土层各处理间土壤有机碳含量无显著差异,但翻埋绿肥显著提高了土壤全氮含量:与裸地对照相比,翻压长武怀豆能使土壤0—20 cm土层氮含量提高40.57%—41.51%;而翻压黑麦草可提高18.87%—19.81%。农田施肥管理能在腐解前期加快绿肥腐解及氮释放速率,却不影响土壤氮累积。长武怀豆更适合作为该地区土壤培肥夏闲绿肥的选择。

溶解氧对滇池沉积物氮磷释放特征影响研究

研究了不同溶解氧条件下对滇池沉积物氮磷释放特征的影响。结果表明溶解氧浓度梯度是滇池沉积物释放氨氮和磷酸盐的主要动力之一,滇池草海由于沉积物-水之间污染浓度差异较小,氨氮和磷酸盐释放速率小于滇池外海区域;好氧状态会抑制氨氮和可溶性正磷酸盐的释放。

Nutrient Release Characteristics of Vinyl Chloride-Vinyl acetate Copolymers Coated SlowRelease Nitrogen Fertilizer and Its Effect on Soil Mineral Nitrogen

[Objective] The aim was to explore release characteristics of vinyl chlo- ride-vinyl acetate copolymer controlled-release N fertilizer and the effects on minerat nitrogen in soils. [Method] Vinyl chloride-vinyl acetate copolymer and hydroxyl-modi- fied VCNAc were taken as coating materials to prepare slow release fertilizer. Nutri- ent release characteristics of VC/VAc slow release fertilizer was evaluated by water immersion method and the effects of VC/VAc slow release fertilizer on mineral ni- trogen were researched by pot experiment. [Result] The release periods of VC-VAc controlled-release urea and hydroxyl-modified VC/VAc coated urea were 60 and 50 d, respectively. Furthermore, the content of ammonium nitrogen reached the peak on the 30th d and the content of nitrate nitrogen reached the peak on the 60th d in soils in treatments with VCNAc and hydroxyl-modified VC/VAc; the content of nitrate nitrogen rose again on the 120th d in the treatment with VC/VAc. In terms of wheat yield, different treatments showed insignificant differences and rice yield in the treatment with VCNAc was significantly higher than that in the treatment with hy- droxyl-modified VCNAc （P〈0.05）. [Conclusion] The release days of slow controlled- release fertilizer vary upon pot experiment method and water immersion method. Slow controlled-release fertilizer is not suitable for monoculture, due to long fertilizer efficiency, but multiple cropping would be optimal for its role to be fully exploited.