In this research, the capability of vermiculite in arsenic extraction, associated with characterizing its main properties was evaluated. To address this purpose, vermiculite was artificially contaminated with arsenic at 7 and 28-day intervals. Then, arsenic was extracted from contaminated soils by different extractants. Various physical and mechanical tests were performed to investigate the effect of arsenic as an anionic contaminant on the properties of the vermiculite, as well as to evaluate how the properties of the contaminated soil were altered by the extraction process. The carbonate bonding phase was probably mainly responsible for the adsorption and fixation of arsenic with more than 50% portion among measured fractions at different curing times. Based on the vermiculite condition, hydrochloric acid was the best extractant for removing arsenic in all studied samples (around 3 -18 % more than other extractants). The clay soil demonstrated few changes due to arsenic contamination and modification. In general, the most promising characteristics of vermiculite as clay liner are its stability after contamination due to high CEC and SSA; however, its workability and strength (UCS between 110 to 220 kPa at different soil conditions) is a challenge and must be improved by adding coarser fractions like silt particles. In general, the results of this study regarding the effects of arsenic contamination and extraction onto vermiculite’s physical properties can provide appropriate information for researchers and geo-environmental engineers.

In current study, the enhanced efficiency of copper (Cu) phytoremediation potential of Calendula officinalis L. was investigated in a Cu-spiked calcareous soil, using foliar and soil application of humic acid. For this purpose, in a greenhouse experiment, seedlings of C. officinalis were transferred to Cu-spiked soils (0, 250 and 500 mg/kg) and treated separately with soil (soil drench) and foliar (spraying plant leaves) humic acid applications at different levels (0, 10, 20 μM). The humic acid treatments were applied 2 weeks after transferring plant, and eventually the various biochemical-physiological traits and phytoremediation indices of Cu in C. officinalis were measured at (specific) time points. According to the results, C. officinalis grew normally without any toxicity signs in Cu-spiked soils, however with increasing the Cu levels, the dry weight biomass decreased and antioxidant enzymes activities increased. Both foliar and soil humic acid application in Cu-spiked soils increased dry weight biomass, photosynthetic pigment contents, Cu concentration, and bioconcentration factor (BCF). Furthermore, the application of this organic substance, obviously moderated the Cu stress since the antioxidant enzymes activities reduced compared to the control. Based on the results, the obtained translocation factor (TF) and BCF values of Cu, which were >1, indicated that this plant is a Cu-hyperaccumulator, which could extract Cu via phytoextraction mechanism. Generally, the results of this study showed that, among the humic acid treatments, application of 20 μM (especially soil drench application) had the best effect on increasing Cu phytoremediation efficiency in the studied soil and it recommended to enhance the efficiency of Cu phytoremediation in calcareous soils.

The present study tries to investigate the effect of composting process on some properties and heavy metals status of two municipal sewage sludge (MSS) as affected by three different organic bulking agents (BAs) at three levels (10%, 25%, and 45% V/V). According to the results, the composting process could reduce the fecal coliform to class A, a reduction more obvious in treatments with BAs than produced composts without them. Changes in the chemical properties of the composts vary according to the type of MSS and Bas. Based on the compost quality standard, most of the produced samples are classified in compost-class II. Examination of the total form of three heavy metals (HMs: Zn, Ni, Fe) of both MSS shows that composting process without BAs increases the HMs total concentration, but using of BAs have not been clear trends. In the contrary, BAs application reduced the available form of Fe and Ni, but increased the Zn available form. Examination of chemical forms of each studied HMs also shows that the composting process reduces the Ni and Fe mobility factor, but increases that of Zn. Generally, while, prepared composts can classify into the compost-class II, based on their properties, the high concentration of total Zn above the standard limit makes it extremely restrictive to be used as class II compost. However, according to EPA regulations, the composts with this concentration of Zn can be used as a relatively safe organic material on agricultural land.

In order to investigate the accumulation and bio-absorption of lead and cadmium in radish and cress, the present study has been conducted in a completely randomized design in three replicates in a hydroponic growing medium. The first factor includes the plant type at two levels (radish and cress), and the second factor is consisted of lead (Pb) (first experiment) at two levels (50 and 100 mg/L), cadmium (Cd) (second experiment) at one level (10 mg/L), and a combination of lead and cadmium (third experiment) again at two levels. After 23 days, roots and aerial parts of both plants have been dried for 48 hours at 70°C in an oven. Then, half gram (0.5 g) of the dried templates has been used to measure the accumulation of Pb and Cd by means of an atomic absorption spectrometer. The highest amount of Pb in radish and crest roots belong to 100 mg/L concentration and the combined Cd (10) + Pb (100) mg/L treatment, respectively, and the highest amount of Cd occurs in Cd (10) + Pb (50) for radish roots and in Cd (10) + Pb (100) combination for cress. Moreover, the Translocation Factor (TF), with a value below 1 and higher bio-concentration factor (BCF) in roots, compared to the aerial part of both radish and cress, seem to be due to the low capability of these plants to transfer Pb and Cd from roots to aerial part. There is a high potentiality for lead accumulation in the roots that prevent its transfer to the aerial part.

Industrial activities compromise the ambient air quality at a local, regional and global level through gaseous and dust emissions. This study reviews uptake mechanisms and the associated phytotoxicity of pollutants in plants, focusing on heavy metals and SO2. It further describes detoxification mechanisms and the resultant biochemical and physiological changes in plants. Finally, the morpho-physiological and growth responses to stress-induced biochemical changes are discussed. Heavy metals and SO2 enter the plant tissue through the stomata, cuticular layers, lenticels and root hairs. In the plant cells, SO2 converts to SO32- or SO42- ions upon reacting with water molecules, which in excess are toxic to plants. However, the detoxification process of SO32- increases the production of reactive oxygen species (ROS). ROS are toxic to plants and damages biomolecules such as lipids, proteins, carbohydrates and DNA. On the other hand, heavy metals, such as Cu and Fe catalyse the Fenton/Haber-Weiss reactions, breaking down H2O2 into OH•. Additionally, Pb and Zn inhibit the activities of ROS-detoxifying enzymes, while other heavy metals bind to cellular layers making them rigid, thereby reducing cell division. Therefore, pollutant toxicity in plants affects biochemical parameters damaging organic molecules and limiting cambial activity. Damaged biomolecules inhibit the plant's capacity to carry out physiological functions, such as photosynthesis, stomatal functions, transpiration and respiration while impaired cambial activity reduces cell division and elongation resulting in reduced plant growth and productivity.

Greenhouse experiment was conducted for four months using Leucaena leucocephala and Pleurotus tuber-regium to determine their bioremediation potentials. Leucaena leucocephala, Pleurotus tuber-regium and Leucaena leucocephala combined with Pleurotus tuber-regium were tested for their ability to improve nutrient (N, P, K, total organic carbon) and reduce heavy metals (Zn, Ni, Pb, Cu) of soil polluted with spent engine oil [5% (w/v)] and soil without spent engine oil was used as control. Bioaccumulation of nutrients and heavy metals in Leucaena leucocephala and Pleurotus tuber-regium were also determined. The highest reduction in Zn, Ni, Pb and Cu (41%, 48.39%, 61.60 and 52.72% respectively) were recorded in soil remediated with Leucaena leucocephala alone, reduction of 30.40%, 26.53%, 48.07% and 39.60% respectively were recorded in soil remediated with Pleurotus tuber-regium alone while in soil remediated with combined Pleurotus tuber-regium and Leucaena leucocephala, reductions of 32.7%, 33.43%, 88.41% and 46.22% respectively were recorded. Bioaccumulation of Zn, Ni, Pb and Cu in Leucaena leucocephala increased by 73.41%, 85.46%, 3366.04% and 125.53% respectively, similarly in Pleurotus tuber-regium by 30.16%, 21.67%, 71.11% and 53.21% respectively. These studies have shown that Pleurotus tuber-regium and Leucaena leucocephala are capable of bioremediating spent engine oil polluted soil although, treatment with Leucaena leucocephala alone tends to be most effective of these treatments.

The present study was carried out to investigate the adsorption and leaching behavior of Cu2+, Zn2+ and Pb2+ by sediments collected from the western banks of three different sectors along River Nile at Aswan governorate, Egypt. The feasibility of sediments for the removal of Cu2+, Zn2+ and Pb2+ from aqueous solutions was tested under the effect of three conditions (pH, initial metal concentration and contact time). By increasing pH, the adsorption of Cu2+ and Pb2+ by sediments decreased while that of Zn2+ increased. The optimum pH values for Cu2+, Zn2+ and Pb2+ removal were determined as 5, 8.5 and 5, respectively. The adsorption capacities of sediments for metal ions were in the order of Pb2+ > Cu2+ > Zn2+. The maximum uptake for Cu2+, Zn2+ and Pb2+ by sediments occurred at contact times of 48 h, 24 h and 72 h, respectively. Adsorption data were fitted well by Freundlich, Dubinin–Radushkevich and Temkin isotherms. The experimental results obtained were analyzed using two adsorption kinetic models, pseudo-first-order and pseudo-second-order, in which pseudo-second-order equation described the data more than pseudo-first-order one. The average leaching percentages of Cu2+, Zn2+ and Pb2+ from sediments were 0.77%, 2.72% and 0.38%, respectively, with respect to pH, 0.83%, 2.49% and 0.38%, respectively , with respect to temperature, and also 0.79%, 2.34% and 0.38%, respectively with respect to contact time. The leaching percentages of metal ions from sediments were in the order of Zn2+ > Cu2+ > Pb2+.

The ever increasing pile-up of electronic waste in dumping sites, especially in developing countries such as China, Pakistan, India and several African countries, might have caused a significant alteration in the microbial community of the contaminated sites. This change in the microbial population may have significant impact to the soil ecology function. The major pollutants of electronic waste are heavy metals like cadmium, lead, nickel, mercury, hexavalent chromium, arsenic and persistent organic pollutants like polychlorinated biphenyls and polybrominated diphenyl ethers. In general, the toxic pollutants reduce the normal soil microbial biota but give rise to increase in the heavy metal resistant and organic pollutants remediating microbes. With the development of culture- independent approach as a tool for studying microbial diversity, the microbial community structures in toxic waste contaminated sites have been revealed gradually. Studies on the microbial community structure of electronic waste contaminated sites show that there are significant differences between the contaminated and the non-contaminated sites. Soil pH in the e-waste contaminated sites of various regions has been reported in a wide range varying from pH 4 to pH 12. However, the predominant phyla so far identified in the electronic waste contaminated sites, based on studies through culture independent approach, are Firmicutes, Proteobacteria, Actinobacteria, Acidobacteria, Chloroflexi, Crenarchaeota and Bacteroidetes accounting for more than 80% of the total sequence reads on an average. The genera like Pseudomonas, Bacillus, Clostridium, Rhodococcus, Achromobacter and many unclassified bacteria are the common types in the contaminated sites.

Due to rapid industrialization and urbanization, environmental pollution has become a major concern in developing countries; therefore, the main objective of the current study is to determine heavy metal contents of Pb, and Ni for 42 topsoil samples, collected from 14 green spaces along the 1st and 2nd ring roads in Hamedan City in 2016. For this purpose, after determining some chemical properties as well as acid digestion of soil samples, Pb and Ni concentrations have been found in the soil samples with ICP-OES. All statistical analyses have been conducted, using SPSS 18.0 statistical package, with the results showing that the metal levels in soil samples, collected from green space of 1st and 2nd ring road, have been 34.86±10.28 and 41.57±10.08 mg/kg for Pb and 14.0-20.33 and 14.0-20.0 mg/kgfor Ni, respectively. Also the mean concentration of Pb and Ni have been lower than MPL. According to heavy metal concentration maps, the spatial distribution patterns of Pb, and Ni contents in the soil samples are generally similar along the 1st and 2nd ring road. Due to the fact that traffic volume in the 2nd ring was higher than the 1st one, there has been a significant difference in the mean contents of Pb between the topsoil samples, collected from the 1st and 2nd ring roads; therefore, it is recommended to keep environmental health in order to control the anthropogenic sources, causing the pollutants discharge into the environment is recommended.

Water and sediment samples were collected from six different stations, located along the Nil River between February and June 2015. Concentrations of cadmium, lead, zinc, and copper were determined. The extent of the sediment pollution was assessed, using the multiple pollution indices, namely contamination factor (CF), pollution load index (PLI), and the geoaccumulation index (Igeo). The results showed that the level of metals in water samples exceeded background concentrations for Cd and Pb, and the average values for those elements were higher than those of Zn and Cu, ranked as the following: Pb (0.58)> Zn (0.38)> Cd (0.32)> Cu (0.061). For sedimentary samples, the results showed that Zn and Pb concentrations were greater than the concentrations of Cu and Cd, exceeding the background values (except for Cu). The concentration of the tested heavy metals decreased to the following order: Zn (96.2)> Pb (61.5)> Cu (38.83)> Cd (2.34). The Igeo values revealed that Cd (2.87) and Pb (1.61) had accumulated significantly in the Nil River. Contamination factor (CF) confirmed that the sedimentary samples were moderate to very high in terms of Cd, Pb, and Zn contamination. The Pollution Load Index (PLI) values were above one (>1), indicating an advanced decline of the sediment quality. Also, the results showed that the stations, located at the middle portion of the river (S3, S4, and S5) have higher levels of metals than the other stations (S1, S2, and S6). The assessment of heavy metals' levels in water and sedimentary samples indicated that river water and the sediments in the study area were strongly impacted by agricultural activities and domestic waste water.