Search

Exposure to toxic metals has been increased during recent decades, especially in megacities where various anthropogenic sources discharge loads of pollution to overcrowded urban districts. Soil as a simultaneous sink and source of metallic pollution is considered as an optimum media for monitoring such pollution. In this study, 41 surface soil samples were collected from a district in south of Tehran megacity. Despite determination of bulk metal concentrations (Ni, Cu, Cr, Zn, Co, Cd, Pb Mn, Fe, Ca and Na), a single-step extraction scheme was used for determination of anthropogenic portions. Enrichment factor and geo-accumulation (Igeo)/pollution (Ipoll) indices were calculated to estimate the enrichment class and degree of contamination, respectively. Except for Cd and Pb, other toxic metals showed no or negligible exceedance of reference values. Descending order of anthropogenic contribution from bulk metal concentrations was detected to be as: Cd > Pb > Mn > Cr > Zn > Co > Cu > Ni. Cadmium and lead were detected by all three indices to be in extreme and moderate/significant classes. Relatively high concentrations of Na were attributed to intense salt spraying for streets deicing during winter time when sampling occurred, while Ca concentrations were justified by geogenic source mainly dominance of limestones (dolomites). A prompt decision should be made to avoid further exposure of metals of concern to citizens in this overcrowded district of Tehran megacity.

Determining the main sources of pollution (MSP) in groundwater is crucial to improve water quality (WQ) status. Field studies were conducted in this research, where five sampling campaigns were carried out from 36 wells in the southern Tehran aquifer. In all samples, WQ parameters were measured and evaluated regarding the Iranian drinking water standard (IDWS). Finally, by using the principal component factor analysis (PCFA), the probable MSP in the aquifer were determined. The results showed that all ions, total hardness, and total dissolved solids were above the IDWS. To analyze the PCFA results, only the first four of twenty rotated principal factors (RPFs) that conserved a high percentage of the variance of the data (about 90%) were considered. The results of the first PRF revealed that the geological structure was the MSP in the aquifer. Furthermore, the second RPF was mainly affected by nutrients (nitrate and orthophosphate) and microbial parameters (fecal and total coliforms), indicating the importance of agricultural activities and sewage effluents as another MSP in the aquifer. Finally, the remarkable share of heavy metals and pH in formation of the third and fourth RPFs, respectively, reflected the role of industrial activities as a probable MSP of groundwater.

Nowadays, with the ever-increasing growth of the population and the development of various industries, we are experiencing an increase in man-made leachates such as urban solid wastes, chemicals, and wastewater. Generally, the groundwater in aquifers is contaminated by these pollutants seeping through the above-ground sediment. The vulnerability of groundwater to contaminants can be assessed, which means those areas with lower vulnerability can be distinguished from those areas with high vulnerability. Hydrogeological parameters are presented in a modified DRASTIC method which assesses depth to groundwater surface (D), recharge (R), soil media (S), topography (T), impact of vadose zone (I), conductivity of aquifer, hydraulic capabilities (C), and the effect of land use activity (L). This study aims at zoning the pollution potential of the Mashhad aquifer by using the modified DRASTIC method and GIS to assess the old and new landfill sites. The results show that new and existing (old) landfill sites for solid waste disposal in Mashhad site selections should be closed down due to their location in high vulnerability zones where the risk of groundwater pollution is high.

Annually, a great volume of sediment and suspended particulate matters (SPMs) enters into the seas through estuaries. In the estuarine zone, metals present in SPMs may undergo conservative or non-conservative changes. In the present study, oxidation-reduction potential (ORP) as the most complex chemical parameter of open sea water and its relationship with the behavior of t metals in the estuarine area were investigated. Dissolved oxygen was used as a strong oxidant to increase the ORP. According to the absorption and desorption experiment, Mn and Cu are desorbed from SPMs during estuarine mixing. However, Zn and Pb are absorbed into the SPMs. In addition, the analysis results were indicative of the conservative behavior of Ni. The results of the three-step chemical partitioning of the SPMs revealed that Mn and Cu are desorbed from the SPMs physically, whereas Zn is absorbed into the SPMs chemically. Also, results showed that Pb is physically desorbed from the SPMs, while it is absorbed into SPMs chemically. All metals, except for Ni and Zn, whose reactions with the SPMs are not affected by an increase in the ORP, are affected by the escalation of this parameter.

In this study, arsenic concentration of Haraz River water at 20 stations and relative risk and hazard levels regarding ingestion and dermal exposure routes are evaluated. Furthermore, the quantitative threat caused by the consumption of Rainbow trout muscle from the area is also analyzed. The concentration of arsenic increases from upstream areas towards the downstream estuarine zone with a substantial rise in the central part. Arsenic-containing drainage discharged from the Central Alborz coal mine, hot spring spas, as well as municipal (Amol city) and agricultural (numerous rice paddies) land uses that become denser towards downstream are considered as major pollution sources. The inhabitants are not exposed to a significant hazard or risk regarding dermal exposure. However, for the oral ingestion exposure route, all 20 samples present hazard quotient values greater than unity and risk values greater than one in ten thousand. The results show that if the river water is used for drinking, a high-risk status would be imposed on consumers. Finally, the concentration of arsenic in muscle tissues of ten Rainbow trout fish samples was found to range from 0.48 to 1.30 μg/kg of dry weight which is below the allowed daily intake. However, if we consider that lots of other constituents in the total daily intake within the study area contain arsenic, estimated values may be interpreted as a trigger for further health threats.

The hydrochemical characteristics of groundwater in the southern parts of Tehran Province are considered. Twenty-three sampling stations were selected and major anions/cations, electrical conductivity and pH were detected. Sulfate and chloride were found as major anions, while no specific dominant cation was determined. More than half of the samples were found to be unsuitable for drinking purposes, due to high concentrations of anions/cations. Regarding agricultural use, almost all samples were classified as having high-risk levels of salinity, while for alkali hazard considerable risks were observed in most cases. Generally, an increasing trend of salinity is observed from northwest to southeast of the study area. Such increase may be justified by the adjacency of the Iran central desert and salt lake to the southern boundaries of the study area. Extended use of sulfate-containing fertilizers may also play a key role in justifying the high sulfate concentration in comparison to other anions.

The Ahvaz oil field located in southern Iran has been identified as a possible point of elemental pollution, since elevated levels of metallic pollution (As, Cd, Cr, Ni, Cu, Zn, Pb and V) have been introduced to the adjacent environment through the oil excavation activities. The concentration of metals Cr, Ni, Cu, Pb and Zn are far below all reference values while that of As, Cd and V are remarkably above limits. Enrichment factor (EF) reports the mean waste status to be enriched by all three elements As, Cd and V while the Igeo values manifest the strongly polluted condition for Cd and moderately polluted for As and V. In order to quantify the association of metal concentrations with various Acid soluble, reducible, oxidizable and pseudo-total phases and consequently to estimate the potential mobility of existent metallic pollution, the sequential chemical partitioning technique was used for the samples collected from clean soil, drilling mud and wastage pit. According to the results achieved by chemical partitioning analysis, Cd seems to be mobile. Similar conditions exist for V with relatively lower risk level. Regarding As, the potential mobility is estimated to be low as a remarkable portion of bulk concentration (more than 70 %) is accumulated in the pseudo-total phase. Paying attention to the bulk and partitioning concentrations of three enriched elements in the drilling mud, it is concluded that the main cause of wastage pit contamination may be attributed to the nature of drilling mud utilized in excavation activities. Additionally, the geological texture in different depths may also play a role in this scenario.

Evaluating the metallic risky pollution of soil in the vicinity of National Iranian Lead and Zinc Company in Zanjan Province, Iran is considered in this study. Twenty-six composite samples were collected from the surface soil of the study area including two lead and zinc depots. Total concentration of elements lead, zinc, chromium, cadmium, cobalt, arsenic, iron and manganese were analyzed. To envisage a more realistic view of the environmental risks, anthropogenic and bioavailable fraction of total concentration values were also detected. Total concentration values of arsenic, cadmium, lead and zinc were higher than that of shale and mean earth crust. Bioavailable and anthropogenic fractions analysis showed that Cd may be considered as the most threatening bioavailable pollutant. Lead and arsenic were also introduced as elements of concern. Enrichment factor assessed As and Cd to be significantly and Pb to be moderately enriched in topsoil samples while pollution index categorized Pb in moderately polluted status. Hierarchical cluster analysis indicates a probable kind of analogy in origin, behavior and destiny of mentioned elements. Because of their remarkable biological and anthropogenic fractions in soil samples, current abandoned open-dumped depots are potential pollution sources within the area. Strict monitoring procedure should be performed to prevent further mobility of metallic pollutants toward food chain.

The Haraz River flows northwards through the Iranian Alborz mountains in the central region of Mazandaran province and empties into the Caspian Sea. This area has been a rich source of minerals from times immemorial. About 45 mines (coal, limestone, sand and gravel, etc.) have been operational for the last eight decades. Towards the estuary, the river receives a discharge of industrial, agricultural and urban wastes. Eight sediment samples from the Haraz River and its main tributaries were collected and analyzed for base metals as well as Sr and Fe. The chemical partitioning of metals (Cu, Zn, As, Cd, Pb, Fe, Ni, Cr, Co and Sr) in each sample was determined in four fractions (acid-soluble, reducible, oxidizable and residual). The total content of each metal was also determined. The results showed relatively higher concentrations of Cd, As, Sr and Pb in comparison to that of shale. However, based on the chemical partitioning of metals, it is found that Pb, Co, Cd and Sr are the most mobile metals. In spite of the high As concentrations in sediments, it is not likely that this element is a major hazard for the aquatic environment, since it is found mainly in the residual fraction. Cadmium is the metal that showed the highest percentages in the acid-soluble fraction (the most labile) and the lowest in the residual fraction. However, Fe, Cr and Ni are present in the greatest percentages in the residual fraction, which implies that these metals are strongly linked to the sediments.

The problem of leachate treatment is something critical for the landfill of Tehran (Kahrizak). Natural Leachate treatment is a way to help the environment rehabilitate itself, and lessen the threats of pollution for alive habitats. It produces an appropriate situation for existing plants and animals to keep on living and also it may help other existences to find their new habitat in the site of rehabilitated landfill. One of the biggest problems in Tehran is lack of water. Therefore it can help using recycled water for irrigation and keep microclimate of the region alive. Designing a good region to recycle the leachate naturally and absorb the contaminants of soil and water in the originate site, is a huge responsibility for environmental designers.

The Haraz River is one of the most significant rivers in the southern Caspian Sea basin. Towards the estuary, the river receives discharges of industrial, agricultural, and urban wastes. In the present investigation, bulk concentrations of Cu, Zn, As, Cd, Pb, Fe, Ni, Cr, Co, and Sr in Haraz River (Iran) bed sediments were measured from several sample locations. In addition, association of studied metals with various sedimentary phases was assessed to determine the proportions of metals in different forms. The intensity of sediment contamination was evaluated using an enrichment factor (EF), geo-accumulation index (Igeo), and a newly developed pollution index (Ipoll). Both EF and Igeo formulae compare present concentrations of metals to their background levels in crust and shale, respectively. In a specific area with its own geological background like Haraz River water basin where naturally high concentrations of metals may be found, such a comparison may lead to biased conclusions regarding levels of anthropogenic contamination. Accordingly, chemical partitioning results are substituted for the mean crust and shale levels in the new index (Ipoll). The Pearson correlation coefficient between the anthropogenic portion of metallic pollution in Haraz river-bed sediments with Ipoll showed much more value in comparison with those of geochemical accumulation index and enrichment factor. The order of metals introduced by anthropogenic activities are as follows: Sr > Pb > Co > Cd > Zn > Cu > Ni > As > Cr > Fe. The results showed relatively higher concentrations of Cd, As, Sr, and Pb in comparison with those of shale. However, based on the chemical partitioning of metals, it is found that Sr, Pb, Co, and Cd are the most mobile metals. In spite of the high As concentrations in sediments, it is not likely that this element is a major hazard for the aquatic environment since it is found mainly in the residual fraction. Also, Fe, Cr, and Ni are present in the greatest percentages in the residual fraction, which implies that these metals are strongly linked to the sediments.