Arbuscular mycorrhizal fungi affecting the growth, nutrient uptake and phytoremediation potential of different plants in a cadmium-polluted soil.

Heavy metals stress is of great concern as it contaminates the environment affecting human health and the growth and quality of different plants including the medicinal ones. The use of soil microbes is among the most efficient methods for treating heavy-metal polluted soils. The objective was to investigate the effects of arbuscular mycorrhizal (AM) fungi (Glomus mosseae) on the nutrient uptake (N, P, K, Fe, and Mn,) and Cd removal of different plants including rosemary (Salvia rosmarinus), amaranth (Amaranthus sp.), and ornamental cabbage (Brassica oleracea) in a Cd-polluted soil. The experiment was a three-way factorial on the basis of a randomized complete block design with three replicates. The experimental soil was sprayed with Cd (0, 10, 25, 50, 75 and 100 mg kg-1), and after 2 months it was inoculated with 100 g of mycorrhizal inoculums, and was planted in 4-kg pots. Plant growth (root and aerial part) and nutrient uptake as well as Cd removal from the contaminated soil were significantly affected by the experimental treatments. AM fungi significantly increased plant P uptake (35%) compared with N (24%), K (4%), Fe (24%) and Mn (13%). According to the results, rosemary was the most effective plant for the bioremediation of the soil. There were significant differences between plant roots and aerial part in terms of plant nutrient uptake and phytoremediation potential. Although increasing Cd concentration decreased plant growth and nutrient uptake, mycorrhizal fungi was able to alleviate the stress by significantly increasing plant growth, nutrient uptake and phytoremediation potential.

An integrated approach for spatial distribution of potentially toxic elements (Cu, Pb and Zn) in topsoil.

In this study, statistical analysis and spatial distribution were performed to compare raw data and centred log-ratio (clr) transformed data of three copper (Cu), lead (Pb), and zinc (Zn) potentially toxic elements (PTEs) concentration for 550 surface soil samples in Khuzestan plain. The results of both approaches showed that classical univariate analysis and compositional data analysis are essential to find the real structure of data and clarify its different aspects. Results also indicated that spatial distributions of raw data and clr-transformed data were completely different in three studied metals. Raw data necessarily shows the effects of anthropogenic activities and needs an additional evaluation of human health risk assessment for these three studied elements. Data obtained from clr-coefficient maps also demonstrated the role of geological processes in the distribution pattern of potentially toxic elements (PTEs). To improve the understanding of the implications for PTE pollution and consequences for human health, a RGB colour composite map was produce to identify the potential origin of PTEs from areas with higher than typical baseline concentrations.

Assessment of the potential ecological and human health risks of heavy metals in Ahvaz oil field, Iran.

The potential hazard to human health from exposure to heavy metals in surface soil was assessed using 66 soil samples collected from Ahvaz oil field. To this end, the contents of heavy metals were measured by the inductively coupled plasma spectroscopy (ICP-OES). Mean levels of As, Cd, Co, Cr, Cu, Ni, Pb, V, and Zn were 5.9, 0.4, 7.1, 36.5, 41.2, 39.8, 67.4, 31.5, and 77.6 mg/kg, respectively. Contents of all studied heavy metals, with the exception of Co, Cr, and V, were several times higher than that of baselines. Correlation coefficients and principal component analysis (PCA) identified two main groups as sources of heavy metals in the surface soil of Ahvaz oil-field. Metals such as Co, Cr, and V were observed to originate from natural sources and As, Cd, Cu, Ni, Pb, and Zn originated from anthropogenic sources such as petroleum leakage and the pollution caused by drilling mud from oil wells. Pb and Zn were of significantly high EF mean enrichment value, and Co, Cu, Cd, and As had high enrichment in surface soil. Pb, Cr, V, Zn, Co, Cu, Ni, and As had a low potential ecological risk (PER) whereas Cd had a moderate PER. The risk of carcinogenic and non-carcinogenic diseases was detected to be higher in children than in adults. The carcinogenic risk (Cr) calculation was more than 1 × 10-6 for children and adults. Additionally, the CR of Cr for both children and adults indicated risk under control conditions.

Application of exploratory and Spatial Data Analysis (SDA), singularity matrix analysis, and fractal models to delineate background of potentially toxic elements: A case study of Ahvaz, SW Iran.

It is essential to study spatial distribution of Potentially Toxic Elements (PTEs) in surface soil, and separate PTEs geochemical background from their human sources, and also determine their correlation with other environmental factors in order to assess their impacts on humans, provide realistic environmental geochemical maps, and carry out soil management. For this purpose, this study was designed to investigate the surface soil in Ahvaz, Southwest of Iran. The applied methods were exploratory data analysis (EDA), including boxplot, Q-Q plot, probability plot (PP), concentration-area (C-A), number-size (N-S) fractal model, and singularity index (SI) model. The obtained results revealed that the fractal models led to a more realistic distinction among the geochemical population compared to the EDA methods such as probability plot. Furthermore, the C-A model was found to be more effective on the separation of subpopulation compared to the N-S and PP models. The studied elements exhibited a similar pattern implying that pollution is a function of geochemical dispersion regarding the surface soil in Ahvaz (Zn â‰« Pb > Cu > As). The studied metals-major elements plot also indicated that there was no meaningful relationship between Pb, Zn, Cu, and major elements in the study area. Plots of association of Pb, Zn, Cu, and As distinctly showed two general geogenic and anthropogenic populations. Moreover, the results of SI revealed that the highly contaminated area was consistent with the main defined hotspots and anthropogenic sources of elements as well as places affected by the contaminated area that have not been reported in previous studies. Furthermore, a combination of geochemical and geographical model comprising different statistical models was developed to more effectively separate geogenic from anthropogenic sources. Also, the geochemical background for the studied elements (Pb 180 mg/kg; Cu 200 mg/kg; Zn 90 mg/kg; As 65 mg/kg) was shown to be higher than the Iranian soil quality guideline with Pb, Zn, Cu, and As of 100, 80, 200, and 18 mg/kg, respectively.

Ecological and human health risk assessment of toxic metals in street dusts and surface soils in Ahvaz, Iran.

This study aimed to examine the concentrations and environmental health risk of the potentially toxic metals including Pb, Zn, Cu, Cd, Cr, and As in street dusts and surface soils of Ahvaz, the capital of Khuzestan province, located in the southwest of Iran. To this end, a total of 81 street dusts and 96 surface soils were collected from Ahvaz urban areas. Toxic metals were measured by inductively coupled plasma-mass spectrometry and evaluated using enrichment factors, potential ecological risk index and human health risk assessment. Lead in street dusts and Pb and Cu in surface soil showed the highest enrichment factor. The results revealed that there are two major sources of toxic metals in Ahvaz, including industrial activities and road traffic emissions and also resuspension of soil and dust particles. Cu, Pb, Zn, and Cr in Ahvaz soil and dust particles are strongly influenced by anthropogenic activity, mainly industrial and traffic emissions, while As and Co originate from resuspension of soil natural parent particles. The potential ecological risk index (RI) values for dust samples indicated that 58.02% of all samples showed low potential ecological risk. Moreover, 33% and 9% of samples showed moderate and considerable ecological risk, respectively. In addition, the RI values for soil samples indicated that 57% and 40% of all samples had low and moderate ecological risk, respectively, and 3% had a high ecological risk. The hazard index (HI) values of studied potentially toxic metals showed that there is no non-carcinogenic risk for children and adults. Furthermore, the HI value for children was 2-7 times upper than those for adults, which confirm that children show more potential health risks for exposition to these potential toxic metals. Cancer risks of the studied potential toxic elements for both adults and children decreased in the following order Crdust > Crsoil > Cddust > Cdsoil > Asdust > Assoil > Pbdust > Pbsoil. The carcinogenic risk values of Cd, As, and Pb for adults and children was lower than 1 × 10-6, suggesting carcinogenic risk of potentially toxic metals in the street dust and surface soil could be neglected. On the other hand, the carcinogenic risk value of Cr was greater than 1 × 10-6 for both adults and children revealing that the carcinogenic risks of Cr essentially need more consideration for environmental management control.

Spatial distribution and human health risk assessment of mercury in street dust resulting from various land-use in Ahvaz, Iran.

Mercury as a toxic element and its associated health hazard has been an important topic of research for urban pollution for many years. In this paper, the spatial distribution, pollution assessment, and health risk associated with Hg in roadside dust 96 street dust samples, representing differing land-uses, have been investigated. Land-uses included residential areas (RA), industrial areas (IA), public gardens (PG), roadside areas (RS), and suburban areas (SA) in the city of Ahvaz, Iran were investigated. Compared with other cities, the concentration of Hg in Ahvaz was considerably higher with a mean value of 2.53 mg kg-1, ranging from 0.02 to 8.75 mg kg-1. Residential areas exhibited higher Hg in street dust than other areas, as demonstrated by spatial mapping illustrating hot spots associated with old urban areas with high residential density, high volume traffic of roadside areas, and industrial districts: including oil-drilling activities, steel smelting-related industries, and small industrial towns around Ahvaz. However, Hg concentrations in street dust near to the public gardens (PG) and suburban areas (SA) were not at elevated levels compared other land-uses investigated in this study. A health risk assessment model of non-carcinogenic effects was evaluated for both children and adults. The HQ values also revealed that the main exposures route for children and adults decreased as follows: vapour > ingestion > dermal contact > inhalation. The hazard index (HI) in each area is less than the safe level (HI ≤ 1) for children and adults, but higher for children. The HI value decreases as the following order: RS > IA > RA > SA > PG, which indicates potentially serious health hazards for children in the study areas.