Cadmium speciation as influenced by soil water content and zinc and the studies of kinetic modeling in two soils textural classes

Background and aims:Since few studies have existed in the literature about the effect of zinc(Zn)on cadmium(Cd)chemical forms in soils.Therefore,this study has been performed to determine the impact of Zn on cadmium Cd chemical forms in two soil textural classes in Fars province-Iran at two soil water content(SWC)(flooded soil water content(FSWC)and field capacity soil water content(FCSWC))and study the kinetic modeling of Cd.Methods and materials:Variables were three levels of Cd(0,30 and 60 mg kg-1 of soil as CdSO4·8H2O),three levels of Zn(0,5 and 10 mg kg-1 of soil as Zn-EDTA)three level Incubation times(2,4 and eight weeks),two soil textural classes(clay and sandy clay loam)and two SWC.The randomized completed block design(RCBD)was used for this experiment.The Tessier sequential extraction method was used to determine the Cd concentration in(WsEx),(Fe-MnOx),(Car),(Om)and(Res)chemical forms.Results:In the FSWC,Zn reduced the Cd concentration in Fe-MnOx,Car and Om forms and increased the WsEx but had no significant effect on the Res form.Changes in the Cd chemical forms under the in-fluence of Zn in both soils followed a similar trend.In the FCSWC,Zn reduced the Cd concentration Car and Om forms and increased the Cd concentration in the Fe-MnOx and WsEx forms while had no sig-nificant effect on Res form in the sandy clay loam soil.In the clay soil adding Zn reduced the Cd con-centration in Car and Om fractions and increased the Fe-MnOx and Res forms while has no significant effect on WsEx form.The competitive transport and adsorption Interactions between these two ions caused the changing in the Cd concentration in its chemical forms.Zn reduces the Cd concentration in the forms which are easily released into the soil solution from where they can be absorbed by plants.The power function kinetic mode is the best fitted model which can describe the Cd adsorption in our soil samples.The clay and organic compounds control the Cd adsorption in soils.The higher rate of Cd adsorption in almost all shaking times shows that Cd has more ability to occupy the adsorption sites in soils.

前期土壤含水量对水文模拟不确定性影响分析

前期土壤含水量是影响洪水形成的重要流域物理因素,在该次水文模拟中土壤初始含水量采用新安江日模型计算得出.研究中,通过改变日模型模拟的时间长度TP,来研究初始时刻土壤含水量的变化对洪水模拟精度的影响.结果表明:初始土壤含水量对于洪水模拟的精度有显著影响,不同日模型计算时间可以使次洪初始土壤蓄水量W的变化达到42%,而相应的洪峰偏差达到57.7%.土壤和降雨观测数据分析显示,土壤体积含水量与前期累积降雨量有一定地相关关系.为有效解决传统模型与流域真实物理属性数据的融合问题,初步建立了实测土壤体积含水量数据与模型中土壤湿度参数及前期降雨的经验关系.

基于土壤墒情抗差的降雨径流预报模型--设计与实验流域应用

本文旨在将实时监测得到的土壤墒情转化为流域水文模型可以直接使用的土壤含水量,论证将实时土壤墒情资料用于实时预报的可行性;利用实时监测土壤墒情,改进传统的模型结构,设计基于实测土壤墒情的降雨径流水文预报模型.采用土壤含水量误差抗差估计技术以抵御观测资料粗差的影响,提高系统的稳定性;并在此基础上提出了土壤含水量系统响应修正方法,以提高模型计算精度.将该模型应用于实验流域——宝盖洞流域进行应用检验,洪水模拟合格率达到92.3%,整体模拟精度达到甲级.

滴灌玉米叶温的数据驱动模型与不确定性分析

【目的】探寻玉米叶温对不同深度土壤含水率、气象因素的响应关系。【方法】采用不同供水条件下的滴灌玉米土箱试验,基于叶温、气象和土层含水率数据设计3种输入项结合线性回归模型和神经网络模型,研究了玉米叶温与环境因素的数据驱动模型及模型的不确定性。【结果】(1)在叶温变化模拟中,与线性模型相比神经网络模型具有优势,在40%和60%滴灌湿润比处理下的全因素模型的决定系数由0.8提升到了0.9;80%湿润比处理下全因素模型的决定系数由0.5提升到0.7;(2)单因素不确定性分析中,与叶温变化最密切的气象因素是空气温度,其次是空气湿度和净辐射;在土层含水率的不确定性分析中,30~40 cm土层含水率与叶温变化的响应关系最密切。【结论】结合MC(Monte Carlo method)设计的模型不确定性分析,以d-factor指标量化单影响因素与叶温的响应关系,不同深度土层含水率与叶温的响应关系存在差异,30~40 cm土层是水分响应关键土层。

南方典型多雨山区山洪灾害预警指标分析

为研究山洪灾害对山区居民的影响情况,利用水位流量反推法,并考虑前期降雨及土壤含水情况,分别计算较干、一般和较湿3种工况下的临界雨量指标,综合分析得出山洪灾害影响区域的立即转移指标,同时结合涨洪历时,确定合适的提前时间,反推出相应的准备转移指标。以华南山区某典型小流域研究对象,计算分析了典型受山洪影响的沿河村落,确定出不同时段的预警指标,计算结果与山洪灾害现场调查情况较符,为制定防灾减灾对策和措施提供依据。