重金属的土水分配行为研究——根际土壤溶液采样器的应用

采用根际土壤溶液采样器(Rhizon-SMS)原位采集河南平原耕地土壤溶液.用土壤溶液中重金属浓度对数作为因变量、土壤溶液理化性质作为自变量,进行多元线性逐步回归,结果表明:只有有机碳进入Cu的相关方程,pH进入Cd的相关方程.土壤溶液pH和土壤中的Zn都作为自变量进入Zn的相关方程.土壤溶液中的Cu与pH没有线性关系,而Cd和Zn与土壤溶液pH有显著的线性关系(p＜0.01).计算了土壤中Cu、Cd、Zn在土壤与土壤溶液中的分配系数Kd.本研究中,3种重金属的Kd大小顺序为:Cu＞Zn＞Cd.根据Freeze 和Cherry模型,联合log(Kd-Cd)、log(Kd-Zn)与pH的线性关系,估计了Cd和Zn在土壤中的迁移速度.     

高效液相色谱法测定土壤中的二氯喹啉酸

用50 ml甲醇︰0.05 mol/L硼砂溶液(p H=10)(9︰1,v/v)作为提取剂对20 g(或适量)土壤样品中残留的二氯喹啉酸振荡提取2 h,离心过滤后分取滤液25 ml浓缩,甲醇定容至2 ml,再用滤膜过滤后待测定;高效液相色谱仪(HPLC)以1.0 ml/min的甲醇︰1%乙酸水溶液(55︰45,V/V)为流动相,柱温45℃,在238 nm的紫外光波长下进行二氯喹啉酸的外标法定量。该方法精密度为6.0%,检出限为0.012 mg/kg,不同类型土壤的加标回收率74.9%~98.8%,能满足有机分析要求。该方法既简捷易操作,又能满足土壤中二氯喹啉酸低残留量的测定。     

弧底梯形渠道无喉道量水槽水位流量关系数值模拟

目前为适应我国多数渠道断面方式和灌区管理方式,开发研制新型量水配套设施对灌区节水起着至关重要的作用。利用Fluent 6.3大型流体力学数值仿真软件,结合有限体积法、RNG k-ε湍流模型和VOF模型,在不同渠道底坡上对不同量水槽水位流量进行数值模拟试验研究。结果表明:（1）量水槽流态上游水面平稳属于缓流,量水槽槽内水流为急流,可知由缓流过度到急流必然会发生临界流,量水槽沿程弗劳德数可知量水槽喉口附近扩散段内产生临界流;（2）弧底梯形渠道无喉道量水槽具有较好的水位流量关系,渠道收缩比ε与渠道比降i对形成单值稳定的水位流量关系有较大的影响,随着渠道尺寸增大同时收缩比ε减小,量水槽水位流量逐渐在较大的底坡范围内形成统一的水位流量关系。（3）流量系数与量水槽宽和收缩比具有较好的线性关系,同时流量系数随R,H、ε的增大而变大,回归分析建立的量水槽流量公式,测流公式平均误差值小于5%,说明弧底梯形渠道无喉道量水槽测流是可行的,满足明渠测流要求。研究成果对灌区渠道量水槽的设计优化提供了一定的参考和建议。     

石佛寺人工湿地对水体中富营养物质去除效果分析

以石佛寺人工湿地为研究对象,通过对湿地内各项水体富营养指标监测数据的分析,研究人工湿地对辽河水中富营养物质的去除效果。结果表明:2009年石佛寺人工湿地建成以来,水库出口处水体富营养情况明显好于湿地建成前,其中DO含量明显增加,有机物COD_Mn,BOD₅及营养盐NH₃-N,TN和TP的含量有显著降低。辽河水流经湿地内部,部分时段水体中DO含量的变化率出现负值,但湿地出口处DO含量均达到7.0 mg/L以上;湿地对有机物及营养盐具有良好的去除效果,且去除效果在汛期好于非汛期,2009—2011年的去除率均达到正值,对有机物COD_Mn,BOD₅的最大去除率分别可达到48.3%,65.8%,对营养盐NH₃-N,TN和TP的最大去除率分别可达到78.1%,88.2%和72.0%;2012—2013年部分时段的去除率出现了负值,说明随着湿地运行时间的延长,植物死亡后的腐烂分解会导致富营养物质的二次释放。     

美国路易斯安那州土壤碳估算的尺度效应——美国STATSGO和SSURGO两大最新土壤数据库的比较研究

Estimation of soil organic carbon (SOC) pools and fluxes bears large uncertainties because SOC stocks vary greatly over geographical space and through time.Although development of the U.S.Soil Survey Geographic Database (SSURGO),currently the most detailed level with a map scale ranging from 1:12 000 to 1:63 360,has involved substantial government funds and coordinated network efforts,very few studies have utilized it for soil carbon assessment at the large landscape scale.The objectives of this study were to 1) compare estimates in soil organic matter among SSURGO,the State Soil Geographic Database (STATSGO),and referenced field measurements at the soil map unit;2) examine the influence of missing data on SOC estimation by SSURGO and STATSGO;3) quantify spatial differences in SOC estimation between SSURGO and STATSGO,specifically for the state of Louisiana;and 4) assess scale effects on soil organic carbon density (SOCD) estimates from a soil map unit to a watershed and a river basin scale.SOC was estimated using soil attributes of SSURGO and STATSGO including soil organic matter (SOM) content,soil layer depth,and bulk density.Paired t-test,correlation,and regression analyses were performed to investigate various relations of SOC and SOM among the datasets.There were positive relations of SOC estimates between SSURGO and STATSGO at the soil map unit (R2=0.56,n=86,t=1.65,P=0.102;depth:30 cm).However,the SOC estimated by STATSGO were 9%,33% and 36% lower for the upper 30-cm,the upper 1-m,and the maximal depth (up to 2.75 m) soils,respectively,than those from SSURGO.The difference tended to increase as the spatial scale changes from the soil map unit to the watershed and river basin scales.Compared with the referenced field measurements,the estimates in SOM by SSURGO showed a closer match than those of STATSGO,indicating that the former was more accurate than the latter in SOC estimation,both in spatial and temporal resolutions.Further applications of SSURGO in SOC estimation for the entire United States could improve the accuracy of soil carbon accounting in regional and national carbon balances.     

广西财政支农与农民增收的关系分析

采用广西1995—2011年的相关数据,综合运用计量模型、误差修正模型和脉冲响应函数,对财政支农与农民增收之间的关系进行了实证研究,结果表明:(1)财政支农是农民增收的Granger原因,对农民增收有显著促进作用;(2)农村资本和农民受教育年限对农民增收有重要影响,农民人均受教育年限的提高抑制了农民收入水平的提高,农村资本数量的增大促进了农民收入水平的提高;(3)在短期内,财政支农对农民增收作用强度小幅较弱,农村资本对农民增收作用强度增加,农民人均受教育年限对农民增收的抑制作用遭到弱化。     

干湿交替条件下土壤磷释放及其与土壤性质的关系

通过四川瀑布沟水电站消落区典型土壤磷释放室内模拟试验,研究淹水及干湿交替条件下消落区土壤性质变化情况以及土壤性质与磷释放之间的关系,以期为预防水库水体富营养化,水库消落区合理利用与科学制定管理对策提供参考。结果表明：淹水能够提高土壤活性氧化铁（Feox）含量,淹水风干后土壤Feox含量降低至淹水前的水平;淹水后Feox变化幅度为：旱地〉水田〉果园,紫色土〉冲积土。土壤磷吸持饱和度（DPS）与无定形铁铝氧化物Alox密切相关;土壤最大吸磷量（Qm）淹水时最高增加至2 758.01 mg/kg,土壤淹水后Qm、土壤最大缓冲容量（MBC）、土壤吸磷指数（PSI）值升高;淹水能够明显提高土壤的磷素缓冲容量、土壤的最大缓冲能力和吸附能力、土壤磷的保持率,其原因也是与淹水后土壤无定形铁铝氧化物含量大幅度增加有关;通过主成分分析,土壤磷释放能力主要与土壤磷水平和土壤吸磷能力有关,且主要指标包括土壤有机质含量（OM）、土壤有效磷含量（Olsen-P）、土壤磷保持率（f）、土壤最大吸磷量（Qm）、土壤活性氧化铁（Feox）、土壤活性氧化铝（Alox）等,说明四川省瀑布沟水电站消落区土壤存在较大的磷释放风险。     

三种植被类型植物根系对崇明岛海岸带稳定性的影响

Coastal erosion is currently a major problem along the southern coast of Chongming Island, Shanghai. To enhance the erosion protection ability of coastal shelterbelts, two woody tree species, Taxodium ascendens and Salix babylonica, were planted separately into Phragmites australis + Scirpus mariqueter communities in 2006. Two years later, we investigated whether either of these experiments reduced erosion and increased stability in the native herbaceous plant community. We also examined soil stability and root length density under T. ascendens added, S. babylonica added and native herbaceous vegetation conditions along an intertidal gradient from the soil surface to a depth of 40 cm in each experiment, thus to determine the capacity of T. ascendens and S. babylonica to contribute to shoreline stabilization. Topsoil under the native vegetation had greater stability at the middle and higher intertidal zones because its soil stability index and root length density were significantly higher than in the T. ascendens or S. babylonica planted communities. The effect of T. ascendens on soil stability was not generally better than that of the native vegetation. Only at the 20-30 cm soil depth of the middle intertidal zone and in the 10-20 cm layer of the higher intertidal zone the soil stability index and root length densities under the T. ascendens added condition were significantly higher (P < 0.05) than those of the native vegetation. The S. babylonica planted soil had greater stability in the deeper soil layer than the soil under either the native vegetation or the T. ascendens added condition, and its soil stability index and root length density were significant higher (P < 0.05) than those of other vegetation conditions at the 30-40 cm soil depth for the lower intertidal zone and at the 20-40 cm layer for middle and higher intertidal zones.     

窄缝式挑坎体型及动水压强特性分

通过窄缝式挑坎的体型布置、动水压强特性等资料的总结和分析研究，对窄缝式挑坎的体型布置和反弧收宿段动水压强的计算方法进行探讨，将反弧收缩段的窄缝式挑坎动水压强分为两部分：一为反弧段曲率边界引起的离心惯性力，二为窄缝挑坎水流横向收缩产生的附加动水压强。通过分析研究和水力模型试验，提出了窄缝式挑坎最大动水压强的估算式。研究成果可供工程设计参考。     

模拟数控铣床的改造

本文对数控模拟铣床的改造,进给机构用两个步进电动机做动力源,控制系统用8051单片机作为主控制器,用数字信息通过单片机传送给步进电动机控制其按一定方式运行,即可达到零件的加工要求。