بررسی تاثیر آلاینده‌های نفتی بر ویژگی‌‌های فیزیکی رسوبات جنگل حرا

نفت خام و مشتقات آن به عنوان یکی از مهم‌ترین منابع سوخت در سطح جهانی شناخته شده که تقاضای فزاینده آن منجر به آلودگی شدید خاک شده که کیفیت محیط زیست و سلامت انسان را تحت تاثیر قرار می‌دهد. اکوسیستم جنگل‌های حرا دارای تنوع زیستی گسترده‌ای است که در برابر آلودگی آسیب‌پذیر بوده آلودگی‌های نفتی یکی از آلاینده‏هایی است که سلامت خاک سواحل به خطر انداخته است.  با توجه به عوامل آلوده کننده در سواحل این مطالعه به بررسی تاثیرات آلاینده‌های هیدروکربنی نفت سفید و گازوئیل بر ویژگی‌های فیزیکی خاک سواحل جنگل‌های حرا پرداخته است. به منظور بررسی تاثیر آلاینده‌های نفتی بر خاک، از لایه سطحی (0-10 سانتی‌متر) رسوبات ساحلی جنگل حرا نمونه برداری شد. و پس از هوا خشک شدن به صورت طرح کاملاً تصادفی با نفت سفید، گازوئیل در سه غلظت (0، 4 و 8 درصد وزنی و حجمی) به صورت جداگانه و در سه تکرار آلوده شدند. نتایج تجزیه واریانس داده‏ها نشان داده که آلاینده‌های نفتی بر پارامترهای فیزیکی خاک مورد مطالعه  تاثیر معنی‌داری  در سطح 1 درصد داشته‌اند. در این پژوهش، مشاهده شد که در حضور نفت سفید، پارامترهای mwdwet ، درصد پراکنش سیلت و رس، bd و ارتفاع کدورت سنجی محلول روند کاهشی و پارامترهای mwddry ، as و pad روند افزایشی نسبت به شاهد داشته‌اند. همچنین، در سطوح مختلف گازوئیل، ویژگی‌های mwdwet و as روند افزایشی و پارامترهای درصد پراکنش رس و سیلت، bd ، ارتفاع کدورت‌سنجی و pad روند کاهشی نسبت به تیمار شاهد داشته‌اند. کمترین pad مربوط به تیمار گازوئیل 4 درصد و بیشترین آن مربوط به نفت سفید 4 درصد بود. نفت سفید تخریب بیشتری نسبت به گازوئیل بر رسوبات جنگل حرا داشته است. این یافته‌ها به درک بهتر اثرات آلودگی نفتی بر خاک‌های ساحلی کمک کرده و پیشنهاداتی برای راهبردهای مدیریتی مناسب برای کاهش این اثرات ارائه می‌دهند. 

assessing the impact of petroleum pollutants on the physical properties of mangrove forest sediments

1- introductioncrude oil and its derivatives represent one of the most significant sources of fuel on a global scale. with continuous industrial advancements, the production and consumption of these resources are increasing daily worldwide. however, this escalating demand has led to substantial soil contamination, adversely influencing environmental quality and human health. the pollution attributed to petroleum hydrocarbons poses a grave threat to the well-being of all living organisms across the planet. environmental degradation resulting from petroleum spills profoundly impacts soil ecosystems, increases hydrophobicity, diminishes water accessibility, and directly contaminates flora and microorganisms. excessive contamination from point sources impairs soil functionality, disrupts plant growth and microbial activity, and results in enduring ecological repercussions.mangrove forests are critical ecosystems that harbor vast biodiversity, both aquatic and terrestrial, and are particularly vulnerable to pollution. oil contaminants jeopardize the integrity of these ecosystems and instigate adverse alterations. factors contributing to oil pollution along coastlines include oil tanker operations and fuel smuggling. therefore, it is imperative to examine the impacts of oil substances on coastal soil. this study explores the ramifications of kerosene and diesel hydrocarbon pollutants on the physical characteristics of sediments from mangrove forest coastlines.2- methodologyto investigate the effects of petroleum pollutants on soil, samples were taken from the surface layer (0-10 cm) of coastal sediments in the mangrove forest of the kulgan area in bandar abbas. samples were placed in plastic containers with a capacity of 3 kg, air-dried, and homogenized. following a completely randomized design, samples were contaminated with kerosene, diesel, and oil compounds at three concentrations (0%, 4%, and 8% w/v) in triplicate. the samples were kept in a soil and water laboratory at a temperature of 18-25°c for 10 days under field capacity to 50% field capacity in dry and wet conditions to stabilize the soil conditions. after a ten-day rest period, samples were slowly taken from the respective treatments with minimal disturbance, air-dried, and several physical parameters of the soil were investigated. statistical analysis and comparison of data averages were conducted using a one-way analysis of variance and duncan’s test with spss16 software at the 5% significance level. 3- results the findings from the one-way variance analysis revealed statistically significant effects of petroleum contaminants on specific physical parameters at the 1% level across all experimental treatments. metrics such as mwdwet, mwddry, turbidity height, clay and silt dispersion percentages in water, the percentage of aggregate destruction (pad), and bulk density were significantly affected compared to the control treatment. the comparison of averages indicated that both concentrations of kerosene significantly increased the mwddry value compared to the control and diesel treatments (4% and 8%). simultaneously, the bulk density (bd) and turbidity height of the soil solution decreased with increases in mwddry, as, and pad. diesel treatments exhibited positive trends in mwdwet, mwddry, and as properties, while parameters such as clay and silt dispersion percentages, bd, turbidity height, and pad showed negative trends compared to the control. the minimum recorded pad was 4% for diesel, while the maximum pad was 4% for kerosene.4- discussion & conclusions      this research demonstrates that both kerosene and diesel oil pollutants significantly affect the physical properties of mangrove forest soils, with notable differences in their impacts. both pollutants penetrated the soil, causing particle separation, increased pore spaces, and increased total soil volume due to their hydrophobic properties, leading to decreased bd. kerosene and diesel, having low water solubility, formed complexes with soil mineral particles, helping stabilize soil structure and reducing the dispersion of clay and silt in wet conditions. both types of oil pollution caused a decrease in turbidity height; however, diesel treatments resulted in more suspended soil particles compared to kerosene. this is due to diesel’s higher viscosity and slower flow rate, which delayed the settling of suspended particles and increased turbidity. kerosene showed a higher percentage of soil degradation than diesel because its shorter hydrocarbon chains break down faster, resulting in more destructive effects on the soil. in conclusion, kerosene has more detrimental effects on the physical characteristics of mangrove forest sediments than diesel. the observed changes in bd, as, soil solution turbidity, and pad underline the impact of kerosene and diesel. these findings enhance our understanding of oil pollution’s effects on coastal soils and suggest appropriate management strategies to mitigate these impacts. this study highlights the need for further research into the long-term effects of petroleum hydrocarbons on soil health and ecosystem stability. future research should investigate the biochemical pathways through which these hydrocarbons interact with soil constituents and the potential for remediation strategies to restore affected soils. understanding the precise mechanisms of pollutant-soil interactions will be critical for developing effective mitigation and rehabilitation techniques to protect mangrove forests and similar ecosystems from ongoing and future petroleum contamination.4- discussion & conclusions      this research demonstrates that both kerosene and diesel oil pollutants significantly affect the physical properties of mangrove forest soils, with notable differences in their impacts. both pollutants penetrated the soil, causing particle separation, increased pore spaces, and increased total soil volume due to their hydrophobic properties, leading to decreased bd. kerosene and diesel, having low water solubility, formed complexes with soil mineral particles, helping stabilize soil structure and reducing the dispersion of clay and silt in wet conditions. both types of oil pollution caused a decrease in turbidity height; however, diesel treatments resulted in more suspended soil particles compared to kerosene. this is due to diesel’s higher viscosity and slower flow rate, which delayed the settling of suspended particles and increased turbidity. kerosene showed a higher percentage of soil degradation than diesel because its shorter hydrocarbon chains break down faster, resulting in more destructive effects on the soil.