Soil is a major reservoir for contaminants as it possesses an ability to bind various chemicals. These chemicals can exist in various forms in soil and different forces keep them bound to soil particles. It is essential to study these interactions because the toxicity of chemicals may strongly depend on the form in which they exist in the environment. Another thing is that soil variability and some environmental properties may change in soil and cause leaching of trace toxic elements like heavy metals tightly bound to soil particles. Metals associated with urban soil are of environmental con- cern because of their direct and indirect effects on human health. The main purposes of this study undertaken in the Mysore city industrial zone were to identify heavy metals with dangerous environmental load and to find out of their environmental impact (Fe, Cr, Cu, Zn, and Ni). The purpose of this work was to provide information on heavy metals concentration in industrial zone soil of Mysore city, India. Soil samples were analyzed for pH, organic matter, and elec- trical conductivity. Total and available heavy metal concentrations were determined by AAS. In the present study, heavy metalspeciation in soil sample carried out were shows that all metals were mainly associated with the oxidizable and residual fraction, which allows us to predict their mobility in the soil sample.
Speciation analysis of trace elements in soils may be performed using either physical or chemical methods, but the latter offers a reliable and more sensitive approach. The chemical protocols basically employ chemical solu- tions of varying, but specific, strengths and reactivities to release heavy metals from the different fractions of soil samples of interest as a means of quantifying the coex- isting metal species . Elemental quantification in soils can be achieved through single reagent leaching, ion exchange resins, and sequential extraction procedures. The theory involved in the latter is that the most mobile metals are leached in the first fraction and continue in order of decreasing of mobility. Common examples of the sequential extraction techniques are the Tessier Pro- cedure, the Community Bureau of Reference (BCR) Procedure, the Maiz Short Extraction Procedure, the Galán Procedure, and the Geological Society of Canada Procedure [24,65-67]. These sequential extraction pro- cedures promote fractionation. However, despite that a number of extraction schemes have been proposed and developed by several researchers, there abound contro- versies regarding some of the sequential techniques. Nevertheless, the Tessier Procedure is generally accepted as the most commonly used protocol followed closely by the Community Bureau of Reference Procedure, although it is still plagued by limitations.
Two heavy metal polluted soil samples were collected from the Copperbelt Prov- ince, Zambia influenced by mining activities. The first sampling site was located in Nkana West close to a waste ore-site (Site 1). The second area (Site 2) was lo- cated 500 m away from the ore-waste site. For each site 500 g of soil samples were taken within a triangular radius at a depth of 20 cm. Samples were air dried at room temperature and further at 85˚C to a constant weight. About 250 g of rep- resentative samples were pulverized and passed through a sieve mesh of 2 mm. 2.2. Extraction and Analysis of Heavy Metals
The results evaluating soils around Kilema Rice Milling Industry, Lafia reveals that the dominant metal concentration were in the order: Fe > Pb > Co > Ni while Cd and Cr were below detection limit, the potential mobility of the metals within the soil were in the order: Co > Ni = Fe > Pb. The Geoaccumulation index of all the heavy metals determined showed that the test control soils were strongly contaminated with Pb only with relatively high mobility factor. The mobility of metals was less pronounced in the test soil due to high organic matter content around the milling industry usually generated as waste during rice processing.
The exchangeable form of heavy metals can be considered as mobile and it can be used to quantify the short term availability of heavy metals for leaching or uptake by plants . They are considered to be the ones that occur in the ion exchange complexes and which are elucidated depending on the ionic composition of pore waters. They also include metals which are bound to carbonates that can be easily released at lowered soil reaction and are easily available to plants . Silicate minerals provide sites for cation exchange and a few sites for chemical adsorption of heavy metals . Soils and sludges with higher cation exchange capacities have greater tendency for retaining metals. For example, cadmium retention has been observed to be higher in soils with higher cation exchange capacity [35, 28]. Kuo et al.  showed that Cd retention was greater in fine textured soils with high cation exchange capacity (CEC) compared to coarse-textured soils with lower CEC. McBride et al.  showed that Cd retention was most closely related to the exchangeable base content of the soil. Hydrogen ion activity (pH) is probably the most important factor governing metalspeciation, solubility from mineral surfaces, transport, and eventual bioavailability of metals in solutions. pH affects both solubility of metal hydroxide minerals and adsorption-desorption processes. Most metal hydroxide minerals have very low solubility under high pH conditions in natural water. Because hydroxide ion activity is inversely related to pH, the solubility of metal hydroxide minerals increases with decreasing pH, and more dissolved metals become potentially available for involvement in biological processes as pH decreases. Ionic metal species also are commonly the most toxic forms to aquatic organisms . Many metals at high soil contamination levels will form precipitates with oxides, hydroxides and carbonates  ,especially at higher soil pH.
Abstract: The authors apply the chemical speciation model WHAM/Model VII to investigate the distribution of metal species of Fe(III) and the divalent cations of Ni, Cu, Zn, Cd, Hg, and Pb, in the water column of estuaries and coastal areas. The authors compare, for the same locations, measured and modeled free ion and organically bound metal concentrations. The modeled free ion calculations show varying levels of agreement with experimental measurements. Where only natural organic matter is considered as the organic ligand, for Ni, Cd, and Pb, agreement within 1 order of magnitude is found in 122 of 128 comparisons. For Fe and Zn comparisons 12 of 34 (Fe) and 10 of 18 (Zn) agree to within 1 order of magnitude, the remaining modeled values being over 1 order of magnitude higher than measurements. Copper measurements agree within 1 order of magnitude of modeled values in 314 of 533 (59%) cases and are more than 1 order of magnitude lower than modeled values in 202 cases. There is a general tendency for agreement between modeled and measured values to improve with increasing total metal concentrations. There are substantial variations among different analysis techniques but no systematic bias from the model is observed across techniques. It would be bene ﬁ cial to cross-validate the different analytical methods, in combination with further modeling. The authors also assessed the effect of including an anthropogenic organic ligand (ethylenediamine tetraacetic acid (EDTA)) in the modeling, given its known presence in some coastal environments. Except for Cd, all metals were sensitive to the presence of EDTA, even at a low concentration of 50 nM. Environ Toxicol Chem 2015;34:53 – 63. # 2014 The Authors. Published by Wiley Periodicals, Inc. on behalf of SETAC. This is an open access article under the terms of the Creative Commons Attribution- NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
under urea fertilization and/or organic manure fertilization in a controlled environment (phytotron). We used ATR-FTIR spectroscopy to identify and quantify C species and measured and quantified GHG emissions and analyzed it against vegetable yield. Analysis of the soils of both ecoregions showed that the combined use of manure and urea acted differently in the RF and DS soils in terms of regulating microbial activity, C speciation and GHG emissions. We found that the combined use of manure and urea increased the rate of microbial decomposition in the DS samples, thus, increasing the proportion of the processed C species including aliphatic-C, aromatic-C and carboxylic-C forms in the DS samples, while no such effect on microbial decomposition was observed in the RF samples. We also found that the combined use of manure and urea led to an increase in cumulative CO 2 and
Seed germination can typically represent the first step to effective phytoremediation because plant performance at the early stages sets the pace for root and shoot development as well as to determine the extent to which the soil environment may negatively or positively impact plant growth. The lack of significant effect of the contaminants on seed germination can be understood to mean that the seeds of these plants are resistant to penetrative phytotoxic stress of the contaminant combination and at the tested concentrations. Even though, at early growth stage, the nutritional needs of embryonic plants are not provided from the soil environment but internally from seed stored materials(Kapustka 1997), prevention of interference by contaminants with nutritional materials stored in plant seed is preferred. The ability of plants to prevent penetration of contaminants into the seed is attributed to the nature of the selective permeability of the seed coat (Klokk, 1984; Wierzbicka & Obidziń ska, 1998). Plant seed coats acts as a barrier between a plant embryo and the toxic environment, protecting the embryos from contamination until the embryonic roots start to develop (Kapustka 1997). The differential germination response of plants in contaminated soil is accounted for by the fact that the seed coat composition, as well as the permeability of seed coats, varies from plant to plant.
Abstract— Soil contamination by heavy metals is a worldwide environmental problem. Hence determining the chemical forms of a metal in soils is important to evaluate its mobility and bioavailability. This study determined the distribution and speciation of some heavy metals (Fe, Cu, Zn, Pb and Cd) in soils around some selected auto repair workshops in Oghara, Delta State, Nigeria. Soil samples were collected with the aid of soil Augar within a depth of 0 – 15 cm from the vicinity of the four selected auto repair workshops in Oghara, Delta State, Nigeria. The control samples were taken from a site free from auto repair and commercial activities. The soil samples were assessed for some physico-chemical properties, total heavy metal concentration, chemical speciation, mobility and some metal assessment indices of the heavy metals as a function of soil properties. The mean concentration of Fe, Cu, Zn, Pb and Cd in all the sites analyzed were 550.54, 31.08, 36.15, 4.21 and 1.11 mg/kg respectively. Site B and the control had the highest and lowest total concentration of the five metals analyzed respectively. The levels of Cu were above the DPR target value in sites A and B, while the levels of Cd were above the target value in all the sites except in the control site. All the metals were found to be mostly concentrated in the residual fraction except Zn which was found mostly in the carbonate fraction. The mobility factors revealed that Zn is the most mobile element with an average mobility factor of 41.54% while Cd is the least mobile element with an average mobility factor of 16.51%. Contamination factors, index of geoaccumulation and pollution load index were also calculated. This study showed that mechanic workshop is one of the major sources of anthropogenic heavy metals concentration in the environment.
rhizosphere. One of the most important pH effects is the solubilization of nutrients, toxic elements and changes in microbial activity. However, in this study, the concentration of some metals (e.g., Cd and Pb) in Blackfriars was below the detection limits for ICP and this could be explained by the low solubility of these metals due to high pH (See table 3.1 in chapter 3) of the soils, which may have been kept high due to added tap water of pH= 7.93± 0.3. Soils that have neutral pH are suitable for plants as a very high or very low pH can cause disease and be toxic to the plants. In home gardens, where fertilizers are frequently used, the soil pH may be low. Therefore, a test for soil pH is needed regularly to check whether the pH is decreasing due to fertilizer application. If this is the case, gardeners can use a lime (a fertilizer that has a high pH and contains a high amounts of Ca or Mg) to increase soil pH and reduce metal solubility.
The remediation of soil by physical treatment includes technologies that separate the contaminants from the soil solids. The separation process is a volume reduction process that transfers the contaminant to another media, e.g., air or water, and collects it in a concentrated form. Depending on quantity and concentration, the new contaminated media may require further treatment. This additional treatment can either destroy the contaminant or concentrate it for recovery/reuse or ultimate disposal. Hence, physical separation treatment frequently leads to the need for a treatment train to complete the process. Physical treatment using separation technologies is done either in situ or physical adsorption. The main advantages of in situ treatment are that it allows the soil to be remediated without having to excavate or transport it. It also avoids land disposal restrictions on the re deposition of treated soil. In situ remediation generally involves longer treatment times. Because of the heterogeneity of the subsurface, it is also more difficult to assure uniformity of treatment. In situ treatment must also be concerned with avoiding the spread of contamination as a result of inducing the contaminants to move away from the zone of contaminated soil.
DOI: 10.4236/jep.2018.97048 771 Journal of Environmental Protection soil and put it to practical use. Based on the Soil Contamination Countermea- sures Act (Act No. 53 of 2002) by Ministry of the Environment, Government of Japan , the restoration of contaminated soil involves satisfying the environ- mental quality standards for the amounts leached in soil and content in soil. The most reliable method for restoring contaminated soil is to purify it by soil wash- ing. Purification is a very attractive and highly effective method for dealing with contaminated soil. However, it is not very practical because it is economically inefficient and can be applied only under limited conditions, such as when the clay component of the soil is extremely low . At present, there are few effi- cient and economical methods for removing heavy metals, namely, inorganic pollutants, from soil. As with excavation removal, it is common for contami- nated soil to be brought to a treatment facility and processed. However, there is a limit to the amount of contaminated soil that can be accepted at existing dis- posal sites, and establishing new disposal sites is difficult due to the opposition of neighboring residents and the strengthening of regulations. In view of the re- cent circumstances, it has become necessary to avoid treatment by landfilling with contaminated soil, to appropriately treat the target soil right at the excava- tion site, and to create technologies for recycling this soil as earth and sand. Thus, researching new methods for removing harmful substances from soil at a low cost is important.
K a b a t a - P e n d i a s (2001) reported that Cu levels of various soils ranged 1-200 mgkg -1 . In our study the concentration of Cu in soil samples was 6.11 mgkg -1 d.m. The Cu mobility seemed to be dependent on mineral fractions, since carbonates contents were positively correlated with Cu total fraction and negatively correlated with Cu mobilizable fraction. In our study the content of Cu in plant samples was 3.21 mgkg -1 d.m. K a b a t a - P e n d i a s (2001) also reported that Cu levels of various plants from unpolluted regions in different countries changed between 2.1 and 8.4 mgkg -1 . According to results of our study, a concentration of Cu in species P. visianii was within limits of mentioned concentrations. The literature data were shown that copper availability to plants might be reduced due to high iron content in soil solution. In well-aerated soil Fe occurs mostly in the form of Fe 3+ oxides or hydroxides, which are known as efficient sorbents for inorganic cations such as Cu.
Concentration and distribution patterns of some heavy metals in stream sediments in Ibadan, a typical urban city in Nigeria were investigated. Stream sediments were collected from seven streams at 30 sampling sites within Ibadan metropolis and analysed for their total metal concentrating and speciation. The sediments were totally decomposed with hydrofluoric acid and Aqua regia for total metal concentration and subjected to sequential extraction for their speciation Pb, Zn, Ni, Co, Cd, and Cr were determined in this study using Atomic Absorption Spectrophotometer. The overall mean concentrations (ug/g dry weight of sample) and ranges were Pb(136.95±95.2,15.6- 44.40), Zn(102±69, nd-240), Ni 137.0±11.50,4.17-14.20),Co(25.20±7.9,11.50-62.50), Cu(45.90±28. 3,6.89-134),Cd(2.57±0.37,1.4-3.8) and Cr 54.20±20.4,14.40-12.70) giving an order of Pb>Zn>Cu>Ni>Co>Cd. The mean concentrations of Pb and Zn were very high especially in areas with high population and traffic densities. Speciation studies revealed largely anthropogenic heavy metal enrichment for Pb, Zn, Cu and Cd and implicated refuse dumping and urban run-off water, transporting metals from land derived wastes as the source of the enrichment of the streams. Ni, Co and Cr were identified as being of geometrical origin. There were no significant difference among Ni, Co, Cd and Cr mean concentrations between the streams, indicating that they may be from the same source. Many of the metals showed significant correlation at P>0.05 levels.
of cocoa plant growth so still needed the treatment for the management of the cocoa plant. Based on discussions with the owner of the plantation, it is known that the cacao crop age ranges from 10 to 20 years. Fertilizer application is done within 6 months while spraying pesticides on crops routinely every 2 weeks. Based on this problem, this study aims to investigate the content of heavy metals such as Pb, Cd, Ni, Cd, and Zn in the soil of cocoa plantation of East Kolaka. In addition, the purpose is also to identify of metal pollution potential through determination of pH value of plantation soil.
in the function of the size, thermal desorption profiles demonstrated that the mercury species present in the sam‑ ples do not vary with the mercury concentration and the particle size. By means of HgTPD, mercury oxide (HgO) was identified in the beach sands, whereas mercury sulfide (HgS) was found in the soil sample taken from the vicinity of the beach. Complementary methodologies foster the HgTPD conclusions and verify that mercury is present mostly in insoluble stable (HgS) or low‑mobility (HgO) forms in the samples studied. Analyses by ICP‑MS after sequential extrac‑ tion and HPLC separation of mercury species show that inorganic mercury is the predominant form in the samples. Conclusions: The technique HgTPD is a very useful tool to ascertain the origin of mercury in contaminated beach sands and shoreline soils. In the particular area studied in this work, the species identified indicate that previous mining activity was the source of the mercury and rule out the possibility that contamination is derived from coal combustion activities ongoing in the region.
As soil samples were analyzed to specify soil elements, it is investigated that some elements are remained within the world average and others are unfortunately exceeded the world standard level. Among the analyzed components Mg, Al, K, Ca, Fe, Rb exceeds threshold level of environment and others are in the limit. Exceeding concentration of the elements may negatively interfere with plant growth and development. Cluster analysis illustrating two major clusters which indicate their common sources or allure for each other. Correlation matrix is showing significant positive relation among themselves. Limit exceeding components are frequently used as agro-chemicals and industrial raw materials in process industries. Though they are crucial for soil microbes but when threshold limit exceeds it may be lethal for the biosphere. The food chain can be interrupted by the imbalance condition of the soil matrix. Important bio-chemical reaction of the soil is hampered thus following changes effects on biosphere. It is obvious that they are required for soil nutrient but should be maintained the standard to comply the basic reactions in soil matrix.
Some of these heavy metals i.e. As, Cd, Hg, Pbare not essential for plants growth, since they do not perform any known physiological function in plants. Considering the edible part of the plant in most vegetable species, the risk of transference of heavy metals from soil to humans should be a matter of concern.Uptake of heavy metals by plants and subsequent accumulation along the food chain is a potential threat to animal and human health.The absorption by plant roots is one of the main routes of entrance of heavy metals in the food chain.Heavy metal accumulation in plants depends upon plant species and the efficiency of different plants in absorbing metals is evaluated by either plant uptake or soil to plant transfer factors of the metals.Elevated Pb in soils may decrease soil productivity, and a very low Pb concentration may inhibit some vital plant processes, such as photosynthesis, mitosis and water absorption with toxic symptoms of dark green leaves, wilting of older leaves, stunted foliage and brown short roots. Heavy metals are potentially toxic and phytotoxicity for plants resulting in chlorosis, weak plant growth, yield depression, and may even be accompanied by reduced nutrient uptake, disorders in plant metabolism and reduced ability to fixate molecular nitrogen in leguminous plants. Seed germination was gradually delayed in the presence of increasing concentration of lead (Pb), it may be due to prolong incubation of the seeds that must have resulted in the neutralization of the toxic effects of lead by some mechanisms e. g. leaching, chelation, metal binding or/and accumulation by microorganisms.
understanding on how SOC may influence the mobility and transformation of MSMA- derived As. Some research has indicated that increased SOC can decrease MMA and DMA sorption to soils, but no clear correlation between SOC content and As sorption has been documented (Shimizu et al. 2011b). Another study concluded that soil substrate composition significantly influenced As mobility and speciation in percolate water following MSMA application; however, although clay content was seen as a driving factor on As downward leaching potential, the presence of SOC (peat) did not significantly change As retention in soils (Feng et al. 2005). Similarly, in one study, As species transformation was enhanced by SOC content (Dickens and Hiltbold 1967), whereas in another study, addition of cellulose depressed the species transformation of organic arsenicals (Gao and Burau 1997). Given these apparently contradictory findings, research is needed to discern the effect of SOC on As sorption and species transformation within soils.