پذيرفتاري مغناطيسي و ارتباط آن با غلظت برخي فلزات سنگين و خصوصيات خاكهاي سطحي اطراف اصفهان

Magnetic Susceptibility and its Relationship with the Concentration of Selected Heavy Metals and Soil Properties in Surface Soils of the Isfahan Region

به منظور بررسي پذيرفتاري مغناطيسي خاك و ارتباط آن با غلظت برخي فلزات سنگين و خصوصيات خاكهاي سطحي منطقه اصفهان تعداد 158 نمونه مركب خاك از عمق 0 تا 5 سانتيمتري از منطقه‌اي به وسعت 700 كيلومتر مربع برداشته شد و موقعيت نقاط با دستگاه GPS تعيين شد. پذيرفتاري مغناطيسي درجاي خاك با استفاده از حسگر MS2F در صحرا در همه نقاط اندازه‌گيري شد. پس از آماده‌سازي نمونه‌ها مقدار پذيرفتاري مغناطيسي در فركانس kHz 46/0 (lf?) نيز اندازه‌گيري شد. همچنين غلظت كل برخي فلزات سنگين و ويژگي‌هاي خاك شامل pH، هدايت الكتريكي، بافت، سنگريزه، ماده آلي، كربنات كلسيم معادل و گچ در نمونه‌ها تعيين شد. نتايج نشان داد كه غلظت فلزات مس، روي، سرب، آهن و منگنز همبستگي مثبت و معني‌داري با پذيرفتاري مغناطيسي دارند كه مي‌تواند به دليل انتشار آلودگي‌هاي حاصل از ترافيك و فعاليت‌هاي صنعتي در منطقه مطالعاتي باشد. نتايج تجزيه‌وتحليل رگرسيون خطي چندگانه با روش گام‌به‌گام نشان داد كه فلزات Pb، Cr، Zn و Fe و درصد شن، گچ و ماده آلي تقريباً 76 درصد از كل تغييرات پذيرفتاري مغناطيسي در فركانس پايين را توجيه مي‌كنند. معادله رگرسيوني به دست آمده بين پذيرفتاري مغناطيسي درجا با خصوصيات خاك و غلظت عناصر سنگين نشان داد كه 71 درصد از تغييرات پذيرفتاري مغناطيسي درجا با فلزات Pb و Mn و درصد شن، سنگريزه، گچ و ماده آلي در خاكهاي منطقه توجيه مي‌شوند. بنابراين، بر اساس اندازه‌گيري پذيرفتاري مغناطيسي مي‌توان ميزان آلودگي خاك به برخي فلزات سنگين را پيش‌بيني كرد.

In recent years, urban development and industrialization have caused the accumulation of magnetic minerals and heavy metals in soil, which, in turn, reduced the environmental quality. In order to investigate the soil magnetic susceptibility and its relationship with the concentration of selected heavy metals and soil properties, a total of 158 composite surface soil samples (0-5 cm) were taken from an area of about 700 km2. Locations of the sampling sites were determined using a GPS and their land uses were recorded. The in situ magnetic susceptibility for the topsoil samples was measured by Bartington MS2F sensor in the field. Magnetic susceptibility (?lf) was also measured at low frequency (0.46 kHz) using a Bartington MS2 dual frequency sensor. Besides, the concentration of total copper (Cu), zinc (Zn), lead (Pb), manganese (Mn), iron (Fe), nickel (Ni), chromium (Cr) and cobalt (Co) was measured in all the soil samples. Selected soil properties including pH, electrical conductivity, organic matter, calcium carbonate equivalent and gypsum were also determined to understand the relationships between magnetic susceptibility and soil properties. The concentration of Cu, Zn, Pb, Mn and Fe are positively correlated with magnetic properties which could be attributed to an input from traffic emissions and industrial activities. A significant negative correlation was found between ?lf and gypsum and electrical conductivity. This could be due to the fact that any increase in soluble salts and gypsum in soil causes the dilution effect for magnetic minerals. Moreover, the results of multiple regression analysis between ?lf with heavy metal concentrations and soil properties indicated that LnPb, LnZn, LnFe and Cr and percentage of sand, gypsum and SOM could explain approximately 76% of the total variability of ?lf in the study area. The results of the in situ magnetic susceptibility showed that 71% of the total variability of MS2F could be explained by LnPb, LnMn and percentage of sand, gravel, gypsum and SOM in the study area. In conclusion, the concentration of heavy metals and also soil properties appear to greatly influence the soil magnetic susceptibility and, therefore, soil pollution with major heavy metals could be well predicted by magnetic susceptibility measurements.