بررسی پارامتریک رفتار هیدرولیکی پرکلرواتیلن در سیستم‌های دو فازی

نوع مقاله : علمی - پژوهشی

نویسندگان

1 کارشناسی ارشد خاکشناسی، دانشکده کشاورزی، دانشگاه تربیت مدرس، تهران

2 گروه خاکشناسی، دانشکده کشاورزی، دانشگاه تربیت مدرس، تهران

3 گروه علوم خاک، دانشکده علوم کشاورزی، دانشگاه گیلان، رشت

4 گروه عمران، دانشکده مهندسی، دانشگاه شهید چمران اهواز، اهواز

چکیده

بیان کمّی ویژگی های هیدرولیکی خاک نقش مهمی در پیش­گیری از ورود آلاینده­های هیدروکربنی به خاک و آبهای زیر زمینی دارد. به منظور بررسی رفتار هیدرولیکی پرکلرواتیلن به عنوان یک آلاینده­ی سمّی کلردار در خاک، منحنی­های نگهداشت پرکلرواتیلن و آب در خاک بدست آمد. سپس هدایت هیدرولیکی اشباع برای این دو سیال به روش بار ثابت تعیین که مقدار آن برای آب و پرکلرواتیلن به ترتیب 27/395 و 84/410 سانتی متر بر روز بدست آمد سپس پارامترهای مدل­های نگهداشت ون­گنوختن، بروکس-کوری و کوسوگی بدست آمد. هدایت هیدرولیکی غیر اشباع به عنوان تابعی از پتانسیل ماتریک خاک بر پایه­ی مدل­های معلم-ون­گنوختن، معلم­- بروکس­-کوری و معلم-کوسوگی تعیین شد. دقت مدل­ها به ­وسیله­ی آماره­های خطای ماکزیمم، ریشه میانگین مربعات خطا، ضریب تعیین، کارایی مدل و ضریب جرم باقیمانده مورد ارزیابی قرار گرفت. نتایج نشان داد که برای سیال پرکلرواتیلن، مدل ون­گنوختن نسبت به دو مدل دیگر از دقتی بیشتر برخوردار است. مقدار پارامترهای توزیع تخلخل و نقطه ورود هوا در سیستم دو فازی آب-هوا نسبت به پرکلرواتیلن-هوا کاهش یافت. این رفتار به دلیل لزوجت و مقاومت بیشتر آب نسبت به پرکلرواتیلن در برابر جریان است. به این مفهوم که زهکشی آب نسبت به پرکلرواتیلن از محیط متخلخل به مکش بالاتری نیاز دارد. بنابراین می­توان نتیجه گرفت که در یک مقدار معین از فاز مایع، آب نسبت به پرکلرواتیلن نگهداشت بیشتری دارد. به دلیل لزوجت کمتر پرکلرواتیلن، هدایت هیدرولیکی اشباع و غیر­اشباع محیط متخلخل برای پرکلرواتیلن بیشتر از آب است. سیال پرکلرواتیلن با توجه به هدایت هیدرولیکی بیشتر و نگهداشت کمتری که نسبت به آب دارد، در صورت ورود به محیط متخلخل حرکت سریع­تری به سمت آب­های زیر زمینی خواهد داشت.

کلیدواژه‌ها


عنوان مقاله [English]

Parametric Assessment of Perchloroethylene Hydraulic Behavior in Two-Phase System

نویسندگان [English]

  • Mansour Chatrenour 1
  • Mehdi Homaee 2
  • Safoora Asadi Kapourchal 3
  • Mohammed Mahmoodian Shoshtari 4
1 Department of Soil Science, Faculty of Agriculture, Tarbiat Modares University, Tehran
2 Department of Soil Science, Faculty of Agriculture, Tarbiat Modares University, Tehran
3 Department of Soil Science, Faculty of Agricultural Sciences, University of Guilan, Rasht
4 Department of Civil Engineering, Faculty of Engineering, Shahid Chamran University, Ahvaz
چکیده [English]

Quantitative description of soil hydraulic properties is crucial for preventing organic contaminations entering into the soil and groundwater. In order to assess hydraulic behavior of Perchloroethylene, as a toxic chlorinated contaminant in soil, retention curves of Perchloroethylene and water were determined. The Saturated hydraulic conductivity of both examined fluids was determined by constant head method. The Perchloroethylene and water hydraulic conductivities were obtained to be 492.84 and 450.27 cm day-1, respectively. The porous medium retention parameters is obtain based on van Genuchten, Brooks-Corey and Kosugi retention models. Further, the unsaturated hydraulic conductivity for both fluids were obtained based on Mualem-Brooks-Corey, Mualem-van Genuchten and Mualem-Kosugi models. The accuracy performance of models were assessed by some statistics including ME, RMSE, EF, CD and CRM. Results indicated that the van Genuchten model providing better estimations than other models when the studied fluid was Perchloroethylene. The results further indicated that the magnitudes of the pore-size distribution parameters and the bubbling pressure parameters are reduced in water-air system compares to Perchloroethylene -air system. This can be attributed to high viscosity of water and its considerable resistance against flow. This implies that more suction is needed to drain out water from porous medium than Perchloroethylene. Consequently, porous medium provides less retention for Perchloroethylene at a given quantity of fluid than water. Owing to less amount of Perchloroethylene viscosity, the saturated and unsaturated porous medium hydraulic conductivity of Perchloroethylene was more than that of water. Since Perchloroethylene has lower retention and larger hydraulic conductivity than water, its infiltration into porous medium would lead to faster movement towards groundwater.

کلیدواژه‌ها [English]

  • Soil Hydraulic Models
  • Soil Retention Curve
  • Unsaturated Hydraulic Conductivity
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