盐田藻垫和多糖的防渗作用研究

A STUDY ON THE PERMEATION-PROTECTING CREATED BY ALGAL MAT AND POLYSACCHARIDIS IN SALTWORKS

从广饶盐田藻垫提取多糖，分析盐田表土中多糖的含量，再把多糖按比例（４％，８５）加入干净土样，在布氏漏斗中进行渗透对照实验，测定结果和计算数据表明：多糖显著地降低了土壤的孔隙度（１４—２６５）；增加了土壤的含水量降低了土壤对水的渗透率（６０－９８％），并具有一定的离子选择透性（Ｃａ，Ｍｇ，Ｚｎ等减少，Ｋ增加）．在土层上加一薄层（２ｍｍ）藻垫进行类似的对照实验，也证明了藻垫明显的防渗作用．

This paper analyzed the concentration of polysaccharidis in saltwork soil (including mat), and did the comparative permeation tests by adding polysaccharidis to soil and covering a thin algal mat on the surface of soil. Results obtained show that polysaccharidis obviously decreases the empty degree (14-26% ) and reduces the quantity of permeating water (60-98%). Similar phenomenon is found in the mat-covering test.Otherwise, it is found in test that the soil (added polysaccharidis) has a selecting permeation of ions: the concentration of Ca. Mg. Zn reduces and that of K raises. The permeation-protecting effect created by mat and polysaccharidis is very striking, which will be significant to the study in biological perrneation-protecting. Tile algal mat can be divided into three layers: (1) an aerobic layer; (2) a redox-discontinuity layer; (3) an anaerobic layer.As a result of the decay of organic material below the redox-discontinuity layer (RDL), an anaerobic micro environment appears in which hydrogen sulfide (H2S) is duced by the activity of sulfate-reducing bacteria. If there is enough H2S,photosynthetically active purple bacteria which precipitate elementary sulfur within their cells would form a purpleered chromatium 'plate beneath the RDL.Iron, bound on clay and Other minerals but somewhat soluble in the pore water, is in solution as F●++underneath the RDL and precipitates as ferric-hydroxide above the RDL,due to mobilization and upward migration or by duffusion of Fe++in pore water. Under the RDL, Fe++could be fixed as FeS or FeCO3(James. 1966). In the high productivity microenvironment of such an algal mat, the redox gradients are very high, with an Eh difference of more than 500 my across the RDL. In cross sections of algal mat, the Fe++ predpitate is clearly visible a3 a rusty red layer directly above the RDL. This iron hydroxide leaks out of the sediment on furrows an.d along edges in.the form of small streamlets. Such a microbially induced mobilization of iron algal mats of saltworks might supply iron to evaporitic basins of fossil-salt deposits. The algal mat is a valuable organo-sedimentary e Structure for transforming soil, purification of brine, reducillg leakage of the brine, raising water temperatures and accelerating evaporation.