The experiment applied four soil surface treatments ( one control and three pam coverage rates : 80 % , 60 % , 4 % ) . after corn seeds were planted , granular pam mixed with loess soil was spread to cover the soil surface . two replicates were adopted in the experiments 在实验区挑选一块坡面相对比较均一、坡度在5 7的连片玉米田，分别在玉米田的土壤表面采用4个不同的处理：即pam覆盖率80 、 60 、 40和对照，实验采用两个重复。
On the basis of the existing researches about the fully coupled thermal field and moisture movement in unsarurated loess soils , this paper gives the finite element module of thermal field after consideration of various natural elements such as wind speed , radiation , evaporation , and meanwhile put forwards the finite element module of moisture movement on saturated - unsaturated loess soils . furthermore , the paper also probes into the thermal and moisture transferring and coupled theory , and gives finite element module of fully coupled thermal field and moisture movement in unsarurated loess soils 在国内外有关非饱和土温度场、水分迁移场及其耦合问题研究的基础上，给出了考虑辐射、蒸发、风速等边界条件的温度场有限元方程，给出了计算饱和-非饱和土水分迁移场的有限元方程，对非饱和黄土中温度场和水分迁移场传输机理及其耦合问题进行了初步的研究，给出了土体温度场和水分迁移场之间耦合问题的有限元计算模式，分析了温度和含水量之间的相互作用和影响。
The tests of metal absorption and de - absorption on loess and red layer demonstrate that the loess soil is a very strong absorbent to metals . when metals in water - soil solution is high ( > 1 x 10 - 6 ) , absorptive ability for loess in depth and red earth is higher than loess in surface soil . but when metals when metals in water - soil solution is low ( > 1 x 10 - 6 ) , which is much closer to the natural conditions , absorptive ability for loess in surface soil is bigger than loess in depth and red earth 吸附和解吸试验研究表明，黄土对金属离子具有很强的吸附能力：对于浓度较高的水?土体系，深部黄土和红土吸附能力大于地表黄土；而对于更接近自然界条件的低浓度水?土体系( ng级ml ) ，地表黄土吸附效率高于深部黄土，使以离子形式迁移的一部分金属在地表黄土中得以被吸附固定而形成异常，这部分金属可被中性盐提取剂提取。
2 . according to the weighted average , soil co2 concentration is 0 . 58 - 13 . 29 times of that in atmosphere and is relatively lower than similar research , meanwhile , soil co2 concentration in profile varied irregularly , which possibly is due to the chemical and physical characteristic of loess soils , season change and arid climate etc . the variation of soil co2 concentration in profile is mainly controlled by soil temperature and soil moisture , in contrast with soil temperature , the control role of soil moisture is minor . in conclusion , in order to have a good command of the distribution and change rule of soil profile co2 concentration as well as its effect factors , multi - point and successive location experiment should be made , meanwhile establish indoor soil - pillar monitoring experiment 土壤co _ 2的浓度约为大气co _ 2浓度的0 . 58 ? 13 . 29倍与同类研究相比要低，这是与黄土的土质特性，观测期又逢特别干旱年制约了土壤微生物的活动，再加上土壤中有机质亏损，养分不足造成的；土壤co _ 2含量的变化是随温度的升高而升高，在夏季达最高值，冬季最低；在土壤co _ 2浓度变化的影响因子温度和水分中，温度的影响作用高于水分；土壤剖面co _ 2浓度随着深度增加，总的变化趋势是递增的，但也有反复，甚至有的顺剖面而下几乎保持一恒值，这与季节变化和黄土自身结构的通透性以及在观测期内的干旱气候等条件有关。
