The diffusive boundary layer （DBL） is the zone for matter exchange between surface water and aquatic sediments. To elucidate the influence of DBL on salt release from saline sediments to freshwater, two experiments ...The diffusive boundary layer （DBL） is the zone for matter exchange between surface water and aquatic sediments. To elucidate the influence of DBL on salt release from saline sediments to freshwater, two experiments with or without wind blowing were conducted. According to the experiments, a 3.5 cm DBL is formed above the smoothed sediments at a steady wind field and this thickness is greater than other studies. The observed flux of salt through the DBL is 6% larger than the calculated value from Fick＇ s first law. The results indicate that molecular diffusion is the dominant mechanism for salt transport through the DBL. The presence of DBL suppresses the hydrodynamic enhancement for matter exchange between sediments and overlying water. Therefore, salts in the sediments of a polder reservoir may influence the water quality chronically.展开更多
为研究层状土壤对水盐运移以及植被生长的影响,进一步了解植物水分的有效利用情况,以植物生长条件下的室内层状(上层为壤土,下层为河砂)一维土柱水盐运移试验为基础,利用课题组开发的层状土壤水盐运移模型(Layered soil water solute tr...为研究层状土壤对水盐运移以及植被生长的影响,进一步了解植物水分的有效利用情况,以植物生长条件下的室内层状(上层为壤土,下层为河砂)一维土柱水盐运移试验为基础,利用课题组开发的层状土壤水盐运移模型(Layered soil water solute transport and crop growth model,LAWSTAC)进行了相应的模拟和分析。研究结果表明:①LAWSTAC模型可以较好的模拟入渗过程中均质壤土的水盐运移,模型相关参数可以直接用于层状土土柱的模型中。②LAWSTAC模型可以较好地模拟入渗条件下上细下粗型层状土的水盐运移情况,但是对于蒸发过程来说,由于下层河砂参数选取的误差、亦或由于目前水盐运移理论在有优先流存在的层状土中适用性不好,导致蒸发过程模拟效果不佳。③粗质土覆盖细质土能有效减小蒸发量及蒸腾量,上层粗质土对水分运动和盐分运移均有抑制作用。上粗下细型层状结构土壤的蒸发失水主要来自上层粗质土,而上细下粗型层状结构土壤的蒸发失水主要来自下层粗质土,且其累积蒸发量远大于上粗下细型层状土。因此,LAWSTAC模型可为研究自然界中土壤质地差异较大的农田的盐碱化防治以及灌溉水的高效利用提供数据支持。展开更多
为探索不同材料隔盐层对滨海盐碱地水盐运动的影响,在白蜡林地树穴底部布设炉渣和沙子作为隔盐层,比较研究不同深度土壤水分和总盐分的季节性变化规律。结果表明:土壤表层和不同深度处土壤含水量及含盐量变化规律不同,表层主要受降雨和...为探索不同材料隔盐层对滨海盐碱地水盐运动的影响,在白蜡林地树穴底部布设炉渣和沙子作为隔盐层,比较研究不同深度土壤水分和总盐分的季节性变化规律。结果表明:土壤表层和不同深度处土壤含水量及含盐量变化规律不同,表层主要受降雨和蒸发影响,底层则同时还受地下水位变化的影响;1个雨季中,土壤表层强降雨的淋洗作用极为明显,表层不同隔盐层的差异性不太明显,但离表层30 cm处各隔盐层隔盐和抑制返盐的效果非常明显,设置炉渣隔盐层处理的电导率从5月份的591 m s/m下降到了10月份的493 m s/m,沙子隔盐层处理的电导率从558 m s/m下降到501 m s/m;离表层60 cm处炉渣隔盐层从810 m s/m下降到582 m s/m,沙子隔盐层从607 m s/m下降到560 m s/m。从减小电导率的幅度上来看,炉渣的隔盐效果好于沙子。展开更多
基金The National Science Foundation of China under contract No.40572142the Doctoral Foundation of the Ministry of Education of China under contract No.20040423016.
文摘The diffusive boundary layer （DBL） is the zone for matter exchange between surface water and aquatic sediments. To elucidate the influence of DBL on salt release from saline sediments to freshwater, two experiments with or without wind blowing were conducted. According to the experiments, a 3.5 cm DBL is formed above the smoothed sediments at a steady wind field and this thickness is greater than other studies. The observed flux of salt through the DBL is 6% larger than the calculated value from Fick＇ s first law. The results indicate that molecular diffusion is the dominant mechanism for salt transport through the DBL. The presence of DBL suppresses the hydrodynamic enhancement for matter exchange between sediments and overlying water. Therefore, salts in the sediments of a polder reservoir may influence the water quality chronically.
文摘为研究层状土壤对水盐运移以及植被生长的影响,进一步了解植物水分的有效利用情况,以植物生长条件下的室内层状(上层为壤土,下层为河砂)一维土柱水盐运移试验为基础,利用课题组开发的层状土壤水盐运移模型(Layered soil water solute transport and crop growth model,LAWSTAC)进行了相应的模拟和分析。研究结果表明:①LAWSTAC模型可以较好的模拟入渗过程中均质壤土的水盐运移,模型相关参数可以直接用于层状土土柱的模型中。②LAWSTAC模型可以较好地模拟入渗条件下上细下粗型层状土的水盐运移情况,但是对于蒸发过程来说,由于下层河砂参数选取的误差、亦或由于目前水盐运移理论在有优先流存在的层状土中适用性不好,导致蒸发过程模拟效果不佳。③粗质土覆盖细质土能有效减小蒸发量及蒸腾量,上层粗质土对水分运动和盐分运移均有抑制作用。上粗下细型层状结构土壤的蒸发失水主要来自上层粗质土,而上细下粗型层状结构土壤的蒸发失水主要来自下层粗质土,且其累积蒸发量远大于上粗下细型层状土。因此,LAWSTAC模型可为研究自然界中土壤质地差异较大的农田的盐碱化防治以及灌溉水的高效利用提供数据支持。
文摘为探索不同材料隔盐层对滨海盐碱地水盐运动的影响,在白蜡林地树穴底部布设炉渣和沙子作为隔盐层,比较研究不同深度土壤水分和总盐分的季节性变化规律。结果表明:土壤表层和不同深度处土壤含水量及含盐量变化规律不同,表层主要受降雨和蒸发影响,底层则同时还受地下水位变化的影响;1个雨季中,土壤表层强降雨的淋洗作用极为明显,表层不同隔盐层的差异性不太明显,但离表层30 cm处各隔盐层隔盐和抑制返盐的效果非常明显,设置炉渣隔盐层处理的电导率从5月份的591 m s/m下降到了10月份的493 m s/m,沙子隔盐层处理的电导率从558 m s/m下降到501 m s/m;离表层60 cm处炉渣隔盐层从810 m s/m下降到582 m s/m,沙子隔盐层从607 m s/m下降到560 m s/m。从减小电导率的幅度上来看,炉渣的隔盐效果好于沙子。
