Saturday, 15 July 2006

Change In Soil Biological Activity Under Man-Caused Factors Of The Landfills of Solid Municipal Wastes'.

Dina Nevidomskaya, Rostov State Univ, Bolschaya Sadovaya,105, Rostov-on-Don, Russia

A study of biological properties was carried out by the example of the soil covering of one current landfill and another reclamated Solid Municipal Wastes (SMW) landfill of the lower Don, where calcareous ordinary chernozem is the zone initial soil. The soil covering of the current SMW landfill is above all under a mechanic impact resulting from artificial soil mass compaction, anthropogenic fill and turbation of the soil material, which could not but tell upon the results of biological activity. The activity of the catalase enzyme shows rather an evident association with the humus content (r=0.78) and varies in different subjects of inquiry. The humus content in the technogenous horizons is characterized by a very low humus content of 1.7% and, correspondingly, low catalase activity: 1.5 ml O2 /1 min. The reclamated SMW landfill, unlike the current one, shows the consequences of anthropogeny, which are however now influenced, due to the landfill reclamation, by the natural soil formation processes. The landfill soil is characterized by a comparatively high humus content and high catalase activity (the upper technogenous horizons humus being 4.5–5.8%, the catalase being 3.7–5.8 ml O2 /1 min correspondingly), which gradually subside downwards the profile, a typical feature of the zone soil. The presence of the landfill body leads to the formation of the accumulative anthropogenic landscape, the result being diluvial introduction of materials washed off the landfill body down to meso- and microdeclensions directly near the landfill. Biochemical accumulation is thus facilitated. Proceeding from high humus contents in the soil upper technogenous horizons micro-declensions – 9.1% and catalase 6.8 ml О2 /1 min, one may state that the most probable reason for such a rise is the entrance of a mixture of organic and hydrocarbonaceous wastes, which might essentially influence the activation of the soil microflora. Determined also was the invertase ferment activity, which, among the ferments studied, is a soil contamination ‘sensor'. The invertase activity of the soil investigated is either too low, such soil characterized as too poor, or the invertase is on the whole represented by tracer values. The local SMW landfill hydromorphism with the accompanying technogenous soil alkalization with building dust, as well as high contents of the organic matter and phosphorus introduced into the soil together with the organic part of garbage, corresponds to the needs of an urbotechnogenetically indicating bacterium named azotobacter. A combination of the above factors stimulates azotobacter development since this bacterium is insignificantly represented in steppe zones. According to the results of investigation of the physical and morphological properties of the SMW landfill technogenous soil, the maximum of azotobacter content corresponds to rather high humidity, which is a favorable natural factor for azotobacter development. Some samples of technogenically disturbed soil show, against the background of minor azotobacter contents, a development of other groups of alkaliphilic microorganism like Rhizopus nigrus. Lithochemical observation of the current SMW landfill has revealed contrast lithochemical anomalies of the following elements: Fe, Ni, Co, V. The zones of high contents of such nonferrous metals as Cu, Pb, Zn, were located in the SMW filled area, which confirms the potential danger of the buried waste. The upper topsoil of the reclamated SMW has revealed high Mn content on the landfillå territory periphery; high Sr concentration could be observed across the whole landfill territory and this varied from 500 to 1500 mg/kg. High, anomalous concentrations of Cu, Pb and Zn are associated with filtrate outlet to the landfill surface. Based upon the data concerning SMW landfill soil contamination, making comparisons to our data on biological properties, one may make a conclusion on a selective reaction of various class ferments to contamination: activation of oxydoredutases (in terms of the catalase ferment) and depression of hydrolases (in terms of the invertase ferment). Sufficient microbiological azotobacter activity in the SMW landfill technogenous soil, despite the high contamination level, is first and foremost formed by a system of circumstances facilitating this bacterium development. All this apparently makes azotobacter not too sensitive (to a certain degree) to anthropotechnogenous impacts.

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