关于碎石土路基施工的几项适用技术

本文论述了碎石土路基施工中的方法，应注意的问题，为施工提供依据。     

潜流人工湿地修复河道水质研究

1材料与方法 1．1试验装置潜流人工湿地污染河水处理中试系统建设在河道中段旁。系统分3块,填料分别为砾石、卵石、页岩,均混种芦苇、美人蕉、香蒲,为了景观需要,搭配少量景观植物,包括黄菖蒲、花叶芦竹、旱伞竹、鸢尾、梭鱼草、再力花、雨久花、水葱等。植物种植方法为20cm×25cm。     

排土场不同复垦方式下砾石对饱和导水率和贮水能力的影响

露天煤矿排土场是由矿井下采出的煤矸石,露天矿剥离的表土、岩石及覆土共同组成的松散土石混合堆积体,其内部含有的砾石对土体导水性能和贮水能力有重要影响,以往关于砾石对土壤水分的影响多集中于自然土壤,缺乏对排土场、弃渣场等土石混合工程堆积体的水文-侵蚀过程研究.以海州露天煤矿排土场为研究对象,基于野外调查采样和室内定水头入渗试验,研究了排土场不同复垦方式下土体砾石分布特征及其对饱和导水率和贮水能力的影响,以期为提高矿区水土资源利用效率提供理论依据.结果表明,不同复垦方式下排土场砾石总量随土层深度呈现增加的趋势,并且土体剖面砾石总量的平均值表现为农用地最小,这可能是由频繁耕作导致,不同土层之间砾石总量无显著差异;排土场土体不同粒径砾石相对含量平均值的大小顺序为(2~10 mm)>(>20 mm)>(10~20 mm),表现为大粒径砾石在各种因素的综合作用下正逐渐变为细粒径;排土场土体饱和导水率均表现为灌木林地最高,农用地和荒草地较低;饱和导水率与各粒径砾石含量之间呈极显著线性正相关,且随着砾石粒径的增大其相关性越强;排土场土体贮水能力各指标均以灌木林地和荒草地最强,乔木林地和农用地最差,并且饱和贮水量与各粒径的砾石含量之间均存在显著或极显著的相关关系,最大滞留贮水量与各粒径的砾石含量之间均呈现显著的幂函数相关关系,最大吸持贮水量与粒径2~10 mm砾石含量之间存在显著抛物线相关关系;对于>20 mm的粒径而言,影响土壤贮水能力的砾石含量阈值为14%.     

利用热脉冲技术研究石子覆盖对土壤内部蒸发的影响

地表覆盖能够减少土壤蒸发,对土壤保水、保墒有重要意义.本文基于显热平衡原理,探究了石子覆盖对近表层土壤内部蒸发的影响.应用热脉冲技术测定的热参数和土壤温度得到土壤内部蒸发速率、显热通量、土层上下部显热通量差、潜在汽化热和显热贮藏量变化.与裸土相比,石子覆盖以后近表层显热贮藏量无明显变化,t检验3 ～9 mm、15 ～ 21 mm、27～33 mm p值分别为0.439、0.100和0.096,均大于0.05,显热通量减小,t检验3 mm、15 mm、27 mm p值分别为0、0、0.005,均小于0.05,土层上下部显热通量差明显减小,t检验3～9 mm、15 ～ 21 mm p值均为0＜0.05,27 ～ 33 mm p值为0.059＞0.05,潜在汽化热增加,t检验3 ～9 mm、15 ～ 21 mm、27 ～33 mm p值均为0＜0.05,因此用于土壤蒸发的能量减小,致使土壤蒸发速率降低,t检验3～9 mm、15～21 mm p值均为0＜0.05,27 ～ 33 mm p值均为0.100 ＞0.05.土壤蒸发速率变化趋势与土壤显热通量差变化趋势一致:与裸土相比,石子覆盖以后土壤蒸发速率和土层上下部土壤显热通量差的峰值出现的时间滞后,3～9 mm、15～21 mm峰值出现的时间均滞后两天.因此石子覆盖以后土壤蒸发的变化主要表现在土壤蒸发速率减小且蒸发速率峰值出现时间滞后.     

Mineralization of the herbicide MCPA in urban soils is linked to presence and growth of class III tfdA genes

Mineralization and sorption of ¹⁴C-ring labeled herbicide 2-methyl-4-chlorophenoxyacetic acid (MCPA) were quantified along with the tfdA gene abundance in 7 different soils. The soils tested were five gravel soils from urban locations, one soil from the embankment of a railway track, and finally an agricultural soil as a control. The mineralization experiments were performed with a concentration of MCPA of 5 mg/kg and incubated at 10 °C for a period of 60 days.With K_d values ranging from 0.04 to 0.41 l kg⁻¹ the sorption experiments revealed that binding of MCPA to the six gravel soils was lower compared to the control soil which had a K_d value of 0.91 l kg⁻¹. The potential for MCPA mineralization varied from less than 5 to over 55% mineralized in 60 days. The most rapid MCPA mineralization was observed in the soil from the Danish railway tracks with 55% mineralized after only 18 days. The mineralization data was fitted to degradation kinetic models, which indicated that growth occurred as a response to MCPA degradation in most of the soils.Soil DNA was extracted and tfdA genes responsible for the first step in MCPA degradation were quantified by real-time PCR (qPCR) at appropriate time points throughout the mineralization experiments. Indicating growth of specific MCPA degraders, the abundance of class III tfdA genes showed an increase during MCPA mineralization in those soils able to mineralize MCPA.These findings emphasize the importance of the presence of microorganisms that are able to readily degrade MCPA, to avoid groundwater leaching following use on urban gravel areas that possess low binding ability of the compound.     

甘肃砂田的研究与发展

起源于甘肃中部地区的砂田,是适应干旱、半干旱地区气候、地理、土壤条件的产物,具有明显改良和调节农田小环境的功效。文章简要回顾了甘肃砂田的发展和研究历史,分析了砂田的发展前景和砂田研究中亟待解决的几个问题,期望有助于新时期砂田的可持续发展和现代化生产模式的创新。     

两种荒漠土壤和牧草矿物元素含量的比较研究

对砾石和沙质２种不同的荒漠土壤和牧草矿物元素含量进行了分析,结果表明：砾石荒漠土壤和牧草中Ｆｅ,Ｃｏ,Ｍｏ含量极显著高于沙持荒漠（Ｐ〈０．０１）,牧草Ｃｕ：Ｍｏ仅为１．３：１,沙质荒漠牧草Ｃａ含量过高,Ｐ含量偏低,导致牧草中Ｃａ：Ｐ高达５０;１,同时发现,２种荒漠牧草中Ｓｅ,Ｍｎ,Ｚｎ含量均低于反刍动物的营养需要量,其原因可能与土壤中这些元素含量偏低有直接关系。     

宁夏中部干旱带砂田抗风蚀性能研究

利用风洞模拟实验,研究了净风和挟沙风对砂田土壤风蚀的影响.结果表明:在净风吹蚀下,原状砂田的风蚀速率(0.37 gm-2 min-1)分别是农田和荒地的1/4和1/5,风蚀速率随风速的增加呈指数函数递增,其中砂田的递增速度低于农田或荒地;翻耕后的砂田在常见风速下的风蚀速率与农田和荒地相近(分别为1.67 g m-2 min-1、1.75 gm-2 min-1和1.83 gm-2 min-1),但在大风日则低于农田和荒地(分别为3.61 gm-2 min-1、58.83 g m-2 min-1和13.92 gm-2 min-1).挟砂田沙的风沙流吹蚀导致农田和翻耕砂田的风蚀速率增加,原状砂田则出现轻微的风积现象;挟农田土的风沙流吹蚀使原状砂田、翻耕砂田和荒地产生显著的风积,农田则出现更强烈的风蚀;挟沙风吹蚀下的风蚀(积)速率与风速的关系呈二次曲线函数.砂田的粗糙度明显高于农田(分别为0.023 cm和0.002 cm),且随着风速的增加,其间的差值越大;砂田和农田在不同风速条件下的风速廓线均可用指数函数表述.农田和荒地在压砂利用后,其抗风蚀和减尘性能显著增强.     

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.