نوع مقاله : مقاله کامل علمی پژوهشی
نویسندگان
1 دانشجوی سابق دانشگاه تبریز
2 دانشگاه تبریز
چکیده
کلیدواژهها
موضوعات
عنوان مقاله [English]
نویسندگان [English]
Background and Objectives: Sodium dodecyl benzene sulfonate (SDBS) as an anionic surfactant may be added to soil by the use of wastewater, sewage sludge and pesticides and affects its physical, chemical and biological properties. The aim of this study was to evaluate the impacts of SDBS on some chemical and physical attributes of a loam-textured soil.
Materials and Methods: In this study, the effect of SDBS as a between-subject factor at four levels (0, 0.01, 0.05 and 0.25 %) and the effect of time as a within-subject variable at eleven levels (0.25, 2, 7, 14, 21, 28, 35, 49, 63, 77 and 91 days) on soil pH, EC, available Fe, Mn, Zn and Cu, dissolved organic matter index and organic carbon were investigated in a repeated measures design with three replications. The effects of SDBS application on SAR, available sulfate, saturation percentage, bulk density and aggregate stability index were assessed in a completely randomized design after 95 days with three replications. For this purpose, 15 kg of the soil was placed in each of 12 polyethylene containers. Then, SDBS solutions at the aforementioned levels were sprayed on the soils, and the soils were incubated at room temperature for 95 days. The interior of the container was separated into two parts by a perforated wall to take undisturbed and disturbed soil samples for physical and chemical soil attributes, respectively. Finally, the properties of the sampled soils were determined at the above time points.
Results:The pH and EC values decreased and increased over the incubation period, respectively.The pH of the soil at the 0.25% SDBS level was first lower and then higher than that of control.The final soil EC values at the 0.01%, 0.05% and 0.25% SDBS levels (543.3, 693.7 and 786 µS cm-1) were higher than control (513.3 µS cm-1).The concentration of available Fe at the 0, 0.01, 0.05 and 0.25% SDBS levels within the first 6 hours of incubation period (3.51, 3.88, 4.02 and 4.56 mg kg-1) decreased to a nearly constant concentration after 63 days (2.19 mg kg-1).From now on, an increase was observed only for 0.01 and 0.05 SDBS levels.The concentration of available Mn also decreased with time.However, the direct relationship between the available concentration of this metal cation and the SDBS level was observed only at the first week of incubation period and after that the changes were irregular.In contrast, such a direct relationship for Zn was absent at the beginning of the experiment but observed at the last month of the incubation period.The first decreasing and then increasing trend in available metal concentration was also observed for Cu but the interaction between the SDBS level and time was not significant.The available concentration of all four cationic metals increased with increasing the level of added SDBS and the observed order was Zn< Fe< Mn ≈ Cu, on average.Dissolved organic matter index showed the soil concentration changes of SDBS more regular than soil organic carbon.Furthermore, soil available sulfate and SAR significantly increased with increasing the SDBS added level.Among the soil physical attributes, only aggregate stability significantly decreased at the 0.25% SDBS level.
Conclusion: In general, results showed that the effect of SDBS addition on the temporal changes of soil available Fe, Mn, Zn and Cu was different for each metals. Therefore, changes in available forms of metal ions in the soils after addition of greywater may be not only due to their presence in greywater, but surfactant alone can be responsible for these changes. The soil EC and SAR significantly increased with increasing the SDBS level. However, aggregate stability decreased significantly only at the highest level of SDBS.
کلیدواژهها [English]
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