压砂地持续利用对土壤的影响

以宁夏中部干旱区压砂地为研究对象,分析压砂地持续利用对土壤质量的影响。结果表明,随着压砂地利用年限的增加土壤肥力呈逐年下降的趋势,持续压砂利用15 a后,土壤有机质、全氮、碱解氮质量分数分别比对照下降57.43%、46.56%、48.89%。压砂地土壤微生物量碳、氮随着压砂利用年限的延长整体呈下降趋势,土壤微生物生物量碳/氮值低于对照;持续压砂利用后,土壤微生物群落中细菌、真菌、放线菌的数量均显著降低,压砂改变了土壤微生物群落结构组成。Biolog ECO板的平均颜色变化率（AWCD）随培养时间的增加呈上升趋势。压砂初期土壤微生物的碳源利用能力和微生物的功能多样性显著增加,但持续利用后期与对照无明显差异。压砂地不同土层土壤微生物类群对土壤碳源基质利用类型和利用能力存在差异,0～20 cm土壤微生物群落对羧酸类化合物利用能力较强,20～40 cm土壤微生物群落以碳水化合物利用类群为主。持续压砂影响土壤微生物的结构与功能,限制土壤养分的有效供给,可能是压砂地难以持续利用的主要因素。     

Changes in bedload transport rate associated with episodic sediment supply in a Japanese headwater channel

We conducted field monitoring of bedload transport rate associated with experimental sediment release in a natural channel to clarify behavior of the supplied sediment on mixed size bed. Observation of bedload rate at two sites along the 30 m channel reach revealed that downstream migration of finer particles delay compared with coarser particles. Ratio of the bedload sediment that deposited during the migration was higher for finer sediments. These behaviors of the mixed size particles were clear during passage of the sediment wave without changes in water discharge. Flashing peak of discharge that caused artificially by opening of the dam gate did not destroy channel bed structure including steps and pools formed by coarser sediments, and only small amount of bedload was mobilized. Both reach scale channel features including steps, pools, and riffles as well as fine scale features (i.e., armour coat) likely increased critical shear stress of particles and decreased bedload rate during our experiment. Extreme sediment supply induced two types of sediment deposition; (1) filling the pools in reach sales and (2) the intrusion of fine particles into the coarser sediment that formed an armour layer. The all grain size fractions can deposit as type (1) when shear stress of stream water is not enough to entrain bedload particles, while deposition type (2) occurs when finer sediment pass over channel bed on which armour coat is well-developed. Deposition of finer sediment into coarser sediment that forms armour coat is affected by grain size distribution of bed surface sediment. Thus, impact of the sediment supply on downstream channel depends on both bedforms and grain size distribution of bed surface sediment over which the supplied sediment pass.     

砾间接触氧化技术在入湖河流治理中的应用现状

通过介绍砾间接触氧化技术在实际工程设施建设中的应用及影响净化效益的主要因子,为砾间接触氧化技术在我国的发展提供一定技术参考.砾间接触氧化技术根据水体中溶解氧浓度大小可分为砾间接触氧化法和砾间接触曝气氧化法.根据设施设置的位置又可分为直接方式和分离方式.工程应用中,砾间接触氧化工艺一般包括预处理设施、取水设施、净化设施和放流设施.影响砾间接触氧化工艺处理效果的主要因素有理化因子、砾石床设计因子和水力因子.理化因子主要涉及温度和溶解氧,砾石床设计方面需要考虑填料、填料填充率、污泥储存与排除.水力因子主要是停留时间和水力负荷.     

中卫市压砂地土壤有机质空间变异特点研究

通过野外采集土样,获取研究区不同空间尺度的有机质数据,运用经典统计学、地统计学结合GIS的方法,分析中卫市压砂地土壤有机质的空间变异特点。统计分析表明:区域尺度土壤有机质含量为1.64~14.66 g kg~(-1),田间尺度土壤有机质含量为2.73~6.17 g kg~(-1),均属中等程度变异。中卫市压砂地土壤整体处于缺乏水平(1.0%),地统计结果表明:区域尺度土壤有机质有中等的空间自相关性,其中,接近中下水平(1.0%~1.5%)的区域位于沙坡头区的西南部,向四周逐渐降低。在沙坡头区的中部、海原县的东北部形成了两个有机质极缺的地区(0.6%)。而处于缺乏水平(0.6%~1.0%)的区域分布范围最广,主要分布在中宁县的东北和西南部,沙坡头的东部以及海原县的中部和西北部。田间尺度的土壤有机质有强烈的空间自相关性,分布相对比较均匀,在其西部偏低,偏高值地区分布零散,无规律。     

石砾对土壤水分常数的影响

本文以四川盆周山地常绿阔叶林地土壤为研究对象,分析了石砾对土壤水分常数的影响;同时针对砾质土的特点,对土壤容重的定义进行了补充和完善.结果表明:对于砾质土的土壤,样本间水分常数的测定结果重现性较差,变异较大;石砾含量在一定范围内,可增加土壤孔隙数量,提高土壤的入渗率,但使土壤结构的水稳性降低;当石砾含量超过10%,土壤中有效水分数量将随石砾含量的增加而减少;在地表植被不被破坏时,多砾质土壤发生地表径流的可能性极小,存在入渗过速导致养分的流失和水分的流失问题;与非砾质土相比,砾质土在测试、计算和评价方面都有其特殊性.     

潜流人工湿地修复河道水质研究

[目的]研究不同填料潜流湿地对污染物的处理效果,为小城镇河网水体修复提供依据。[方法]研究了砾石、卵石、页岩3种不同填料潜流湿地对受污染河道水质修复的运行情况及处理效果。[结果]砾石、卵石、页岩填料湿地对受污染水体中TN、TP、CODMn均有较好的去除效果,其中砾石床潜流湿地运行效果最好,平均可分别处理49.4%的TN、34.7%的TP及48.5%的CODMn。[结论]潜流人工湿地可以有效改善受污染河道水质,且投资少、操作简单,适于在小城镇推广。     

不同砾石含量塿土堆积体坡面侵蚀特征研究

为明确砾石含量对关中塿土堆积体坡面径流和侵蚀特性的影响,采用室内模拟降雨试验方法,以土质坡面为对照,研究了10%、20%、30%三种砾石含量堆积体坡面的侵蚀特征。结果表明:(1)1.0mm·min–1雨强下,10%砾石含量时初始产流时间最大,雨强1.0 mm·min–1时,各坡面初始产流时间在10%砾石含量时最小;(2)各砾石含量坡面平均流速均随雨强增大而增大,1.0和2.5mm·min–1雨强条件下10%砾石含量坡面流速最大,而1.5和2.0mm·min–1雨强下,含砾石坡面流速较土质坡面分别减少15.3%～21.2%和13.6%～14.1%;(3)不同雨强条件下各含砾石坡面含沙量在产流前期(0～6 min)急剧下降;产流6 min后,含沙量在1.0、1.5 mm·min–1雨强下逐渐趋于稳定,在2.0、2.5 mm·min–1雨强下呈多峰多谷的变化,该时期砾石主导产沙过程;(4)次降雨侵蚀量随雨强增大呈显著的幂函数关系;而随雨强的增大各砾石坡面侵蚀量较土质坡面分别减少22.4%～42.6%、8.2%～66.3%、2.2%～56.5%和45.0%～68.3%。该研究可为关中地区堆积体坡面水蚀模型的建立提供理论依据。     

连续降雨下岩溶区含砾石石灰土坡面径流产沙特征

为明确砾石含量对岩溶区石灰土工程堆积体坡面径流产沙特征的影响，以土质坡面为对照，采用室内模拟降雨试验方法，研究了递增型降雨（0.5—1.0—2.0—2.5—3.0 mm/min）条件下偏土质（砾石含量30%）和偏石质（砾石含量70%）石灰土坡面的径流特性及侵蚀特征。结果表明：（1）0.5 mm/min雨强下，土质、偏土质和偏石质坡面均未产流；随雨强增大，各坡面径流率呈稳定增长—波动的变化趋势，且土质坡面径流率整体小于两种含砾石坡面；偏土质和偏石质坡面产流量较土质坡面增加了0.49倍和0.37倍；（2）1.0～3.0 mm/min雨强下，土质坡面侵蚀速率变化范围为0.16～5.4 g/(m2?s)，整体呈稳定—波动增加的变化趋势；偏土质和偏石质坡面分别为0.16～5.4 g/(m2?s)和0.06～0.74 g/(m2?s)，前者侵蚀速率变化范围大且波动剧烈，后者变化范围小且稳定；随砾石含量的增加，各坡面侵蚀量呈先增后减的变化趋势，偏土质坡面侵蚀量较土质坡面增加了2.5倍，而偏石质坡面则较其减少了0.9倍；（3）各砾石含量坡面侵蚀速率与径流率均呈极显著正相关（P＜0.01，n=76），土质坡面相关性最好，径流率对侵蚀速率具有显著影响；土质、偏土质和偏石质坡面的侵蚀速率与径流率分别呈极显著幂函数、线性函数和线性函数关系；结果可为桂西北岩溶区弃渣场水土治理提供一定的科学依据。     

Importance of bottom type and background color for growth and blind-side hypermelanosis of the olive flounder,Paralichthys olivaceus

When flatfishes are cultured at high-density in an artificial facility, the bright background color and the carpeted bottom substratum (sand or gravel) help significantly to enhance growth and prevent blind-side hypermelanosis. However, how the bright background and carpeted gravel enhance growth and prevent the hypermelanosis is unknown. Thus, we performed three experiments using the olive flounder, Paralichthys olivaceus. In the first, the acupressure of gravel to blind skin and the burrowing behavior of flounder were assessed to determine which eventually suppressed hypermelanosis. In the second experiment, we assessed whether the color of the carpeted gravel affected flounder hypermelanosis and growth. In the final experiment, we assessed whether hypermelanosis of flounder reared on a gravel bottom was continuously inhibited after removal of the gravel substratum, and whether tank color affected the hypermelanosis and fish growth. The results showed that the burrowing of flounder into gravel was more important than the stimulus of rough gravel on blind-skin to prevent blind-side hypermelanosis. The color of the gravel and tanks did not affect hypermelanosis. Removal of the gravel substratum resulted in enhancement of blind-side hypermelanosis. However, fish growth was enhanced by a bright-colored tank but not a bright-colored bottom substratum. In conclusion, these results confirm that the absence of shelter in which flounder can burrow or hide induces blind-side hypermelanosis, and that flounder consistently burrow beneath the substratum to prevent malpigmentation. Additionally, our results show that a bright-colored tank resulted in increased growth, indicating that flounder should be reared in a bright-background to enhance growth.     

喀斯特小流域不同土地利用方式下土壤容重分析

以贵州毕节撒拉溪镇下小寨小流域为研究单元,分析了土壤中砾石含量以及不同土地利用方式对土壤容重的影响。结果表明,土壤中砾石含量与土壤总容重、细土容重之间均呈显著负相关关系。不同土地利用方式下,0～100 cm不同土层土壤总容重、细土容重未表现出一致的大小顺序。不同土层林地细土容重、总容重与菜地、玉米地、人工草地三者之间均存在显著性的差异,退耕地40～100 cm各土层细土容重、总容重与林地细土容重、总容重均无显著差异,说明减少人为干扰,采取休耕措施可以改善土壤物理性状。