چکیده:
بندپایان رده پادمان به دلیل تراکم بالا در اکوسیستمهای خشکیزی و حساسیت زیاد به آلودگیهای شیمیایی، از مهمترین شاخصهای زیستی در بررسی آلودگیها هستند. این پژوهش با هدف بررسی تاثیر آلودگیهای فلزات سنگین و هیدروکربنهای نفتی در خاکهای دو منطقه پالایشگاه اصفهان و کارخانه فولاد مبارکه بر تنوع و فراوانی جمعیت پادمان انجام شد. با استفاده از قیف برلز، بندپایان رده پادمان از خاک جداسازی شدند و در مجموع ۱۱ گونه متعلق به 6 خانواده از ۲ زیرراسته پادمان شناسایی شدند. در خاکهای آلوده به فلزات سنگین بیشترین درصد فراوانی مربوط به گونههای Isotomiella minor، Ceratophysella stercoraria و Hypogastura sp. 1 بود و هیچ نمونهای مربوط به گونه Folsomia candida جداسازی نشد. در خاکهای آلوده به مواد نفتی بیشترین درصد فراوانی به ترتیب مربوط به گونههای Hypogastura sp.، Isotomiella minor و Ceratophysella stercoraria بود. در این پژوهش گونه F. candida در هیچکدام از دو نوع خاک آلوده جمع آوری نشد که نشان دهنده تاثیرپذیری زیاد این گونه از آلودگیهای شیمیایی خاک است و میتوان از آن بهعنوان یک نشانگر زیستی در پایش خاکهای آلوده به ترکیبات شیمیایی استفاده نمود. این اولین گزارش از تغییرات فون پادمان در اثر آلودگیهای زیست محیطی خاکها در ایران میباشد.
Expanded AbstractIntroductionSoil pollution and accumulation of heavy metals such as lead, cadmium, silver and mercury in agricultural products of industrial areas is one of the most important environmental issues that threaten the lives of plants, animals and humans. Harmful effects of these pollutants on living organisms, including disruption of biological activities, adverse effects on plants and humans due to their entry into the food chain have been proven. As well as, oil pollution is one of the most common of pollution in terrestrial and aquatic ecosystems. The development of the petrochemical industry and the non-observance of environmental requirements, have led to the introduction of large amounts of hydrocarbon pollutants into the environment in recent decades.Biomarkers include biological processes, species, or communities of living organisms that are used to assess the quality of the environment and how the environment changes over time. In recent years, the use of biomarkers to identify environmental pollutants, especially heavy metals and petroleum hydrocarbons, has increased. Collembolan arthropods are one of the most important soil decomposers with high species diversity and density, especially in forest ecosystems. These organisms are widely used organisms as biomarkers due to their short life cycle, high density and high susceptibility to various contaminants in terrestrial ecosystems. This research was aimed to identify the collembola fauna in soils contaminated with heavy metals and petroleum hydrocarbons in two industrial areas of Isfahan and to investigate the impact of these contaminants on the diversity and population abundance of these organisms as a biological indicator of soil contamination.Materials and MethodsSoil samples were taken from the lands around Isfahan Oil Refinery and the area around Mobarakeh Steel factory, as contaminated areas to petroleum hydrocarbons and heavy metals respectively. Also, a sample of pristine soil (non-contaminated soil) was taken from the test areas as a control. Heavy metals concentration was measured by atomic absorption method and the amount of petroleum hydrocarbons in the samples was measured by Soxhlet method. The terrestrial arthropods were collected using Berlese funnel. To identify the Collembola species, microscopic slides were prepared and identified according to the taxonomic keys.ResultsDiversity of Collembola in contaminated soilsThe results of chemical analysis of soils showed that there were different degrees of contamination with petroleum hydrocarbons and heavy metals including lead, cadmium and nickel in the sampled areas, and the soil of the control area was free of any contamination. The highest concentration of heavy metal in the studied soils was related to cadmium with 21.92 mg/kg and the lowest concentration of nickel was related to 42.85 mg/kg. Sampling was performed to collect collembolan arthropods throughout the year and a total of 11 species of collembola from 6 families and 2 suborders were collected (table 1).As shown in Figure 1a, Istomiella minor, Ceratophysella stercoraria, Hypogastrura sp.1, Entomobrya sp.1 and Onychiurus sp.2 species are more abundant in heavy metal contaminated area than uncontaminated soil (control). Also, Folsomia candida was not found in the soil samples around the steel factory. On the other, the diversity and abundance of Collembola species collected in soils contaminated with petroleum compounds around the oil refinery were similar to soils contaminated with heavy metals (Figure 1-b). In these soils, the highest abundance of collembolan communication is related to Hypogastura sp.1, I. minor and C. stercoraria, respectively. Also, the frequency percentage of F. candida, Pseudosinella sp.2 and Onychurus sp.1 was zero and no samples of these species were collected, which indicates the high sensitivity of these species to petroleum products and hydrocarbon compounds.Sampling was performed to isolate terrestrial Collembola in different seasons of the year. The results showed that these arthropods were active only in spring and summer. In both autumn and winter, no samples of Collembola were collected in either of the two areas contaminated with heavy metals and petroleum compounds. The interesting point in this study was that no significant difference was observed between the collembola population of contaminated soils and non-contaminated soils in spring. However, in summer, the population of non-contaminated soils was much higher than soils contaminated with heavy metals and petroleum compounds and a significant difference (p ≥ 0.05) was observed between them.As shown in Figure 2, the frequency of Hypogastrura sp.1 and Pseudosinella octoppuncta species in oil-contaminated soils is higher than their frequency in heavy metal-contaminated soils. The frequency of Hypogastrura sp.1 in oil-contaminated soils (40%) was significantly higher (p ≥ 0.05) than the frequency of this species in heavy metal-contaminated soils (12.5%) (Fig. 2). Therefore, Hypogastrura sp.1 is the most resistant species to petroleum products among the species studied in this research. Also, the I. minor showed the highest frequency (28.13%) in soils contaminated with heavy metals. Therefore, this species is the most resistant to heavy metals among the studied species.Discussion and conclusionThe main purpose of this study was to compare the Collembola fauna in soils contaminated with heavy metals and petroleum compounds as a biological indicator in the some industrial regions of Isfahan. In this study, a total of 11 species belonging to 6 families from 2 suborders of Collembola were collected. F. candida was not isolated from contaminated soils with heavy metals, while this species has acceptable population abundance in pristine and non-polluted soils. These results indicate the high sensitivity of this species to heavy metals. Lead and cadmium have very destructive effects on the reproduction of F. candida and cause a significant reduction in reproduction of this species. According to Sandifer and Hopkin (1996), when the cadmium concentration in the soil reaches to 1.2 μg / kg, the reproduction of Folsomia species decreases dramatically. The soils studied in this study were also highly contaminated with cadmium and the concentration of this element in some samples was 21.92 mg / kg, which is several hundred times than the global pollution standard, this is why F. candida was not collected from these soils. Also the species F. candida, Pseudosinella sp.2 and Onchiusus sp.1 were not collected from soils contaminated with petroleum hydrocarbons. Studies by Fountain and Hopkin (2005) show the very high susceptibility of these species, especially F. candida, to chemical contaminants and introduce this species as a reliable biomarker against soil pollutants. In contrast, populations of some species such as I. minor, C. stercoraria and Hypogastrura sp.1 was higher in soils contaminated with heavy metals and petroleum compounds than in non-contaminated soils. These results may be due to the fact that some species of Collembola have the ability to detoxify and remove of poisonous chemicals from their bodies with repeated molting. In Conclusion, the genus Folsomia is one of the most well-known soil collembolan which whose species, due to non-migratory living and its low dependence on sub-habitats, make them important organisms for determining air and soil quality and tracking pollution. Among the identified species of this genus, F. candida has been considered as an ecological criterion and biological indicator of soil. In this study, this species was not isolated in soils contaminated with heavy metals and petroleum compounds and was introduced as the most sensitive species to chemicals. On the other hand, I. minor with a population frequency of about 25% in the studied soils was introduced as the most resistant species to chemical compounds.