بررسی امکان تثبیت ماسه‌های روان با استفاده از پساب صنعتی و میکروارگانیسم‌های خاکزی

به‌منظور بررسی امکان تثبیت ماسه‌های روان با استفاده از پساب صنعتی و میکروارگانیسم‌های خاکزی، دو آزمایش در سال 1398 در دانشگاه یزد طراحی و اجرا شد. آزمایش اول با هدف غربال‌گری باکتری خاکزی مناطق کویری ایران با بیشترین توانایی هیدرولیز اوره انجام شد. نتایج نشان داد باکتری sporosarcina pasteurii با میانگین 3232.3 میکروزیمنس بر دقیقه بیشترین توانایی هیدرولیز اوره را داشت. آزمایش دوم به‌منظور بررسی تثبیت بیولوژیک ماسه‌های روان در شرایط آزمایشگاه به‌صورت فاکتوریل دوعاملی در قالب طرح کاملاً تصادفی با سه تکرار انجام شد. تجزیۀ واریانس داده‌ها نشان داد نوع و میزان مصرف مالچ و اثر متقابل این دو، تاثیر معنی‌داری در سطح احتمال 1% بر صفات مقاومت فشاری، قطر سله و درصد ذرات بزرگ‌تر از 0.84 داشت. بیشترین مقاومت فشاری و درصد ذرات بزرگ‌تر از 0.84 به‌ترتیب به ‌میزان 4.4 کیلوگرم بر سانتی‌متر مربع و 97.5% با کاربرد باکتری sporosarcina pasteurii به‌ میزان یک‌سوم درصد اشباع خاک حاصل شد. بیشترین قطر سله به‌میزان 5.5 سانتی‌متر در کاربرد پساب شورابه کارخانه پتاس به‌میزان یک‌سوم اشباع خاک به دست آمد. نتایج آزمایش نشان داد باکتری‌های sporosarcina pasteurii و pseudomonas fluorescensو پساب شورابۀ کارخانه پتاس، پتانسیل کاربرد به‌عنوان مالچ را دارند.

Investigating the Possibility of Sand Dunes' Stabilization via Industrial Wastewater and Soil Microorganisms

Extended abstractIntroduction: located in the dry belt of the earth, Iran has more than 164 million hectares of drylands. As the rate of wind erosion has significantly increased in recent years, applying sand duneschr('39') stabilization methods seems essential. Therefore, this study sought to identify the soil bacteria affecting the microbialinduced carbonate precipitation and evaluate different amounts of potash wastewater (SSR400 solution) as a cheap solution for stabilizing sand dunes. Materials and methods: To investigate the possibility of sand duneschr('39') stabilization via industrial wastewater and soil microorganisms, two experiments were designed and performed in 2019 at Yazd University. The first experiment was performed to screen the soil bacteria in those Iranchr('39')s desert areas with the highest ability to hydrolyze urea. The tested bacteria included four bacterial isolates from the Eshtehard desert, six bacterial isolates from Iranchr('39')s central desert, and Sporosarcina pasteurii bacteria. The second test was performed to evaluate the stabilization of sand dunes as a twofactor factorial in a completely randomized design with three replications. The first factor included the use of mulch at 0.5, 1, 2 and, 1/3 soil saturation (SP) levels. The second factor was the mulch type that was examined in eight levels: no bacteria, Pseudomonas fluorescens, Sporosarcina pasteurii, Phormidium tenue, Oscillatoria tenuis, b4, distilled water, and potash wastewater (SSR400 solution). Data analysis and statistical calculations were performed using SASV9 and EXCEL software. Also, the mean comparison was performed by the protected LSD test at a 5% probability level. Result: The results of the urea hydrolysis ability test showed that the bacteria in urea hydrolysis had a significant difference in the level of one percent probability. Comparison of the mean results suggested that Sporosarcina pasteurii with an average of 3223.3 mu;s/min of electrical conductivity (EC) had the highest ability to hydrolyze urea. In the next rank, the bacteria isolated from the Eshtehard desertchr('39')s soil (b2) with 2421.3 mu;s/min of electrical conductivity and the bacteria (b4) with 2072.3 micro Siemens per minute belonged to Iranian central desertschr('39') soil. Moreover, the results of comparing b2 bacteriumchr('39')s 16S rRNA sequence with other bacteria in the NCBI gene bankchr('39')s database indicated that the ribosomal RNA sequence of the 16S b2 isolate was 99% similar to the sequences of Pseudomonas fluorescens. On the other hand, the analysis of the variance of the second experimentchr('39')s data showed that the type and amount of mulch application and the interaction of the two had a significant effect at the level of 1% probability on compressive strength and tuber diameter, making the particlechr('39')s percentage greater than 0.84 mm. Following the application of Sporosarcina pasteurii at the rate of 1/3 soil saturation, the highest compressive strength and the highest percentage of particles larger than 0.84mm were observed to be 4.4 kg/cm2 and 97.5%, respectively. Moreover, the compressive strength of potash wastewater (SSR400 solution) and Pseudomonas fluorescens after applying 1/3 soil saturation was 3.88 and 3.85 kg/cm2, respectively. The highest tuberchr('39')s diameter at a rate of 5.5 cm was obtained with the application of potash wastewater (SSR400 solution) at a rate of 1/3 of soil saturation. Also, the tubechr('39')s diameter after applying potash wastewater (SSR400 solution) at the rate of 2 and 1 Lit/m2 was found to be 4.99 and 4.11 cm, respectively. Also, applying Pseudomonas fluorescens and potash wastewater (SSR400 solution) in 1/3 soil saturation led to the creation of 96.4% and 94.4% of particles larger than 0.84 mm, respectively. Discussion and Conclusion: The studychr('39')s results showed that those bacteria with a high ability to hydrolyze urea and deposit calcium carbonate could play an influential role in increasing soil firmness. It was also found that the properties of the calcium, magnesium chloride and calcium nitrate in the potash wastewater (SSR400 solution) increased the adhesion of soilchr('39') particles and the soilchr('39')s stabilization. These solutions increased the surface tension of the soil and strengthened the bond between the soilchr('39')s particles. Moreover, the calcium ion in potash wastewater (SSR400 solution) effectively softened soilchr('39')s colloids and reduced erosion.Generally, the qualitative urea hydrolysis test results indicated that while Sporosarcina pasteurii had a high ability in the hydrolysis of urea and the sand duneschr('39') biological stabilizationrelated traits, Pseudomonas fluorescens was less able in these regards. Moreover, as a mineral mulch, wastewater (SSR400 solution) showed an excellent ability to stabilize sand dunes. However, it should be noted that the very high salinity of this solution can cause many problems in desert lands. Therefore, it is necessary to reduce the solutionchr('39')s salinity before recommending it as mulch. Also, as the application of 1/3 soil saturation increased stabilization in all mulch types, it could be argued that increasing the volume of mulch application per square meter can improve the stabilization of sand dunes. However, due to the limitations of using mulch in desert lands, including water shortages and the difficulty of transporting such solutions to desert areas, applying less amount of the selected mulch may improve soil erosion.