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Sewage sludge contains significant proportions of nitrogen, phosphorus and organic matter. It therefore has a similar fertiliser value to animal manures and slurries. Typical applications can provide a significant contribution to the nitrogen and phosphate requirements of arable and grassland crops. In addition, sludge can contain potentially harmful substances, including pathogens, persistent organic pollutants and toxic metals. It is therefore necessary to control the use of sewage sludge in order to protect human and animal health and to maintain soil fertility and crop yields. The bioavailability of heavy metals can be affected by several factors. Some of these factors are related to soil and some others may be related to plant characteristics. Soil pH, organic mater content, redox status, carbonate content, chloride content, moisture, source and form of metals and plant genotype may be the most important. However, investigation of any factors which may reduce or enhance the availability of heavy metals in soil and uptake by plants would be crucial. Such knowledge and information on these factors could be used and would help the authorities to manage and control the environmental problems which are concerned with sludge application to agricultural land and could threaten the human health. This paper is going to review and describe the factors and circumstances of which the bioavailability of potentially harmful metals would reduce or enhance in soil.

Geophagia or geophagy is a habit for an uncontrollable urge to eat earth that commonly is occur in poverty-stricken populations and particularly there are in children under three years of age and pregnant women. The custom of involuntary or deliberate eating of soil, especially clayey soil, has a long history and is amazingly widespread. Some researchers have described an anomalous clay layer at a prehistoric site at the Kalambo Falls in Zambia indicating that clay might have been eaten by hominids. Von Humboidt reported from his travels in South America in early 18th century that clay was eaten to some extent at all times by the tribe in Peru. In the mid 19 century it was customary for certain people in the north of Sweden to mix earth with flour in making bread whether the clay effected an improvement in taste. In Iran, geophagia has seen in some of children and pregnant which that is solved with eating starch daily. For example, some reports are shown that there has been geophagia disease in some parts of Fars province, around Shiraz city which have been made different health as well as environmental complications. Clay with a large cation exchange capacity that is also fairly well saturated can release and supplement some macronutrients and micronutrients such as Cu, Fe, Mn and Zn. Deficiency of these elements led to dwarfism, hypogonadism, anemia, hepatosplenomegaly and skin problems. Almost all of these health complication evidences are seen in most of people who has been suffered from geophagy in Iran. However, geophagia has a history of 2000 years and the effects of soil and environmental chemistry on human health have been studied for hundreds years ago in China. In this review it has tried to introduce the geophagia as a nutritional and environmental complication in Iran as well as in the world which could be a serious health risk for human.

Zeolites can change soil solution compositions due to having high capacity of adsorption as well as water holding capacity. Zeolite are able to decrease fertilizer losses and their leaching from the soil and also able to adsorb the environmental pollutants such as heavy metals and toxic elements from the wastewaters. Some soil solutions are rich of different metals as well as anions which may potentially be harmful for the organisms and the environment. Natural zeolites such as clinoptilolite, analcime, laumomtite, phillipsite, mordenite are crystalline alominosilicate minerals and are effective minerals to decrease the risk of toxic cations as well as anions. In a series of experiments different mixtures of soil with zeolite were prepared using 0, 0.5, 1, 5, 10 and 100 percent of zeolite by weight. The constant amounts of mixtures were treated with constant volumes of solutions containing NaCl, NaNO3, KCl and KNO3. The electrical conductivity of each solution was 0, 5, 10, 15 and 20 dS/m. All samples were replicated two times and each batch of experiment was containing 60 samples with total number of 240 samples for the whole experiment. Mixtures of soil with zeolite were treated with different salt solutions and were shake for two hours prior to analysis. All suspensions were filtered and their electrical conductivity was measured at constant temperature. The results showed that electrical conductivity of filtered solutions was lower in mixtures containing zeolite compared to soil. Also the electrical conductivity of the filtered solutions was considerably lower in NO3 – solutions compared to Cl–. It concluded that zeolite could probably reduce the electrical conductivity of soil solutions by adsorption of ions from the primary solutions and it seems that zeolite would tend to adsorb more NO3 – ions compared to Cl– ions from the solutions resulting lower electrical conductivity of NO3 – containing compared to Cl– containing solutions.

Natural zeolites are crystalline alominosilicate minerals with three dimensions. In general, three important factors, structure, texture, chemical composition as well as economic value of natural and synthetic zeolites have made them as valuable materials. Zeolites as catalysts in oil and petrochemical industries, fire distinguishing industries and agricultural industries are just some of their applications. Zeolites are also valuable as soil fertilizer, soil moisture holder, municipals as well as industrials wastewater treatment, harmful and toxic chemicals eliminator metals and gases adsorptive. Zeolites are very effective minerals to decrease the risk of toxic cations as well as anions. In a series of experiments different mixtures of soil with zeolite were prepared using 0, 0.5, 1, 5, 10 and 100 percent of zeolite by weight. The constant amounts of mixtures were treated with constant volumes of solutions containing NaCl, NaNO3, KCl and KNO3. The electrical conductivity of each solution was 0, 5, 10, 15 and 20 dS/m. All samples were replicated two times and each batch of experiment was containing 60 samples with total number of 240 samples for the whole experiment. Mixtures of soil with zeolite were treated with different salt solutions and were shake for two hours prior to analysis. All suspensions were filtered and their electrical conductivity was measured at constant temperature. The results showed that electrical conductivity of filtered solutions was lower in mixtures containing zeolite compared to soil. Also the electrical conductivity of the filtered solutions was considerably lower in K solutions compared to Na. It concluded that zeolite could probably reduce the electrical conductivity of soil solutions by adsorption of ions from the primary solutions and it seems that zeolite would tend to adsorb more K ions compared to Na ions from the solutions resulting lower electrical conductivity of K containing compared to Na containing solutions.

Nitrogen is vital for plants and influences the amount as well as the quality of yield. However, in the absence of proper management, it’s excessive in the water resources could have negative impact on water quality and may cause environmental as well as health complications. To evaluate the nitrate concentrations in groundwater resources in Gorgan area, north of Iran, 47 water samples were taken from different groundwater resources of shallow and deep wells as well as streams. The results showed that nitrate concentrations varied from 0.44 to more that 36 mgL- 1showing different pattern in different resources. In deep wells (wells with the depth of more than 50 meter), nitrate concentrations varied from 1.77 to 12.4 mgL-1 with an average of 5.8 while nitrate concentrations in shallow wells (wells with the depth of less than 50 meter) varied from 0.44 to 36.32 with an average of 13.37 mgL-1 . The corresponding data for streams was found to be varied from 3.54 to 27.9 mgL-1 with an average of 15.84. The results showed that nitrate concentrations was clearly greater in shallower groundwater resources compared to deeper ones showing increase of nitrate accumulation risks due to intensive agricultural activities in these area. The trends of nitrate accumulation showed that water resources is becoming more susceptible since they are the main drinking as well as agricultural source of water in the area. It seems that proper management in terms of fertilizers use and irrigation would be necessary to decrease the risk of nitrate accumulation in water with more emphasis to shallow water resources in the area.