The contamination of soil by heavy metals and metalloids is a worldwide problem due to the accumulation of these compounds in the environment, endangering human health, plants, and animals. Heavy metals and metalloids are normally present in nature, but the rise of industrialization has led to concentrations higher than the admissible ones. They are non-biodegradable and toxic, even at very low concentrations. Residues accumulate in living beings and become dangerous every time they are assimilated and stored faster than they are metabolized. Thus, the potentially harmful effects are due to persistence in the environment, bioaccumulation in the organisms, and toxicity. The severity of the effect depends on the type of heavy metal or metalloid. Indeed, some heavy metals (e.g., Mn, Fe, Co, Ni) at very low concentrations are essential for living organisms, while others (e.g., Cd, Pb, and Hg) are nonessential and are toxic even in trace amounts. It is important to monitor the concentration of heavy metals and metalloids in the environment and adopt methods to remove them. For this purpose, various techniques have been developed over the years: physical remediation (e.g., washing, thermal desorption, solidification), chemical remediation (e.g., adsorption, catalysis, precipitation/solubilization, electrokinetic methods), biological remediation (e.g., biodegradation, phytoremediation, bioventing), and combined remediation (e.g., electrokinetic–microbial remediation; washing–microbial degradation). Some of these are well known and used on a large scale, while others are still at the research level. The main evaluation factors for the choice are contaminated site geology, contamination characteristics, cost, feasibility, and sustainability of the applied process, as well as the technology readiness level. This review aims to give a picture of the main techniques of heavy metal removal, also giving elements to assess their potential hazardousness due to their concentrations.

Remediation of Metal/Metalloid-Polluted Soils: A Short Review

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Effect of Poultry Manure on Growth and Yield of Maize (Zea mays Var Praecox) in Jalingo, Taraba State, Nigeria

The grain legumes are a vital component of the sustainable crop production systems as these are not only a good source of dietary proteins but also help to improve soil nutrients status through biological nitrogen fixation. Mungbean (Vigna radiata (L.) Wilczek) is one of the leading grain legumes which is planted all across the globe. Zinc (Zn) is one of the most critical micronutrients required by crop plants, including mungbean, as well as for the human being. This study was carried out to optimize the Zn soil application for vigorous seedling growth, grain yield and grain biofortification of mungbean. Zinc was soil applied at 0, 2.5, 5.0, 7.5 and 10 mg Zn kg-1 soil. The results showed that soil application of Zn improved the seedling growth, morphological and yield parameters, grain yield and grain Zn concentration of mungbean. However, Zn soil application at 10 mg Zn kg-1 soil was significantly better for improving the seedling growth, morphological and yield parameters, grain yield and grain biofortification. It is recommended that Zn should be soil applied at 10 mg Zn kg-1 soil to harvest better grain yield and Zn-enriched grains of mungbean to overcome Zn malnutrition.

Soil application of zinc improves the growth, yield and grain zinc biofortification of mungbean

Genetic diversity and Agro-climatic conditions contribute significantly to the agronomic and morphological features of the food plant species, and their nutraceutical potential. The present study was intended to evaluate the impact of growing conditions on total phenolic and total flavonoid contents, and in vitro antioxidant potential in the bulbs and leaves of onion varieties planted under diverse environmental conditions. Standard analytical methods were used to quantify total phenolic content (TPC), total flavonoid content (TFC), and free radicals’ scavenging/antioxidant capacity. The impact of climatic and soil conditions was assessed using statistical tools. In general, onion varieties cultivated at three different locations viz. Kalar Kahar, Lahore and Swabi exhibited significant variations in TPC and TFC, and antioxidant activities. The bulbs and leaves of Mustang (V1) variety planted at Lahore and Swabi had significantly (p < 0.05), high levels of TPC (659.5 ± 6.59, and 631.1 ± 8.58 mg GAE/100 g, respectively). However, leaves of Red Orb (V2) and bulbs of Mustang (V1), and Golden Orb (V6), harvested from Kalar Kahar depicted the highest concentration of TFC (432.5 ± 10.3, 303.0 ± 6.67, and 303.0 ± 2.52 mg QE/100 g DW, respectively). Likewise, bulbs of V1 planted at Kalar Kahar, Lahore and Swabi exhibited maximum inhibition of DPPH, ABTS, and H2O2 radicals (79.01 ± 1.49, 65.38 ± 0.99, and 59.76 ± 0.90%, respectively). Golden Orb (V6) harvested from Lahore had the highest scavenging of OH radical (67.40 ± 0.09%). Likewise, bulbs of V1 variety planted at KalarKahar and Swabi had significant capacity to scavenge ferric ions (415.1 ± 10.6 mg GAE/100 g DW), and molybdate ions (213.7 ± 0.00 mg AAE/100 g DW). Conversely, leaves of Amazon (V8), planted at Lahore and Swabi depicted significant levels of DPPH, ABTS, H2O2 radical scavenging (90.69 ± 0.26, 63.55 ± 1.06, 51.86 ± 0.43%, respectively), and reduction of ferric ions (184.2 ± 6.75 mg GAE/100 g DW). V6 leaves harvested from Lahore and that of Super Sarhad (V3) from Swabi showed the highest inhibition of OH radical (61.21 ± 0.79%), and molybdate ions (623.6 ± 0.12 mg AAE/100 g DW), respectively. Pearson correlation and principal component analysis revealed strong relationships of climatic conditions, soil properties and elevation with TPC, TFC and free radicals’ scavenging potential in the bulbs and leaves of onion varieties. The variations in the total phenolic and flavonoid contents, and antioxidant potential of different varieties, and their associations with climatic and soil factors revealed the complexity of the growing conditions and genetic makeup that imposed significant impacts on the synthesis of secondary metabolites and nutraceutical potential of food and medicinal plant species.

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Variations in Total Phenolic, Total Flavonoid Contents, and Free Radicals’ Scavenging Potential of Onion Varieties Planted under Diverse Environmental Conditions

Soil bacterial community structure in the habitats with different levels of heavy metal pollution at an abandoned polymetallic mine.

A field experiment was conducted during winter season of 2014-2015 at a farm field located in Swabi Khyber Pakhtunkhwa, Pakistan, with the main aim to evaluate the influence of different organic manures on wheat (Triticum aestivum L.) production. The experiment was laid out in a randomized complete block design (RCBD), with four replications. The treatments were: T1 (control, no manure), T2 (Cattle manure), T3 (Poultry manure), and T4 (Sheep manure). All the organic manures were applied at the rate of 10 tha. At maturity, plant height (cm), number of grains per spike, grain yield, and biological yield were recorded. Results led to the conclusion that T3 (poultry manure) gave the best results, as compared to other treatments. The values of plant height, biological yield and grain yield were 87 cm, 13.66 tha and 5.750 tha, respectively, for poultry manure treatment. Results for number of grains per spike and 1000-grain weight were found non-significant in the prevailing soil condition.

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Application of different organic manures in optimizing optimum yield for wheat in calcareous soil

The present research was carried out with the main aim to evaluate the levels of heavy metals in some contaminated or expected to be contaminated by industrial effluents and some non contaminated soils of district Swabi. A total of 30 soil samples were collected from 15 different selected soil series of Swabi area at 0-15 cm and 15-30 cm depths and analyzed for various chemical properties using standard analytical techniques and for extractable heavy metals Zn, Cu, Fe, Cr, Co, Ni, Cd and Pb using Atomic Absorption Spectrophotometer. All soil samples were found non saline having EC values between 0.13-0.56 dsm -1 . Soil reaction or pH value ranged from 7.21-8.60 except Mansabdar soil which had pH value of 9.21. It was found that swabi soil was moderately to strongly calcareous in nature, alkaline in reaction having deficient to marginal in organic matter content. Furthermore all soil samples were found almost adequate in Fe, Cu and Zn for most of agriculture crops. The higher concentrations of Ni (22.21 and 21.9 mg kg -1 ) and Cr (8.02 and 5.11 mg kg -1 ) at both surface and sub surface were recorded in Gadoom Amazai soils located near ghee mills and many other industries. Higher levels of heavy metals were observed in contaminated soils as compared with non contaminated soils. Decreased in concentration levels of metals were observed in majority of soils with increase in depth. No correlation was found between AB-DTPA extractable heavy metals and soil chemical properties and it might be due to samples collected from different locations with different thermodynamic characteristics. Keyword: Heavy metals, Swabi soils World Scientific News 105 (2018) 1-13

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Heavy metals distribution in different soil series of district Swabi, Khyber Pakhunkhawa, Pakistan

Beneficial Effect of Melatonin on Growth and Chlorophyll Content in Wheat (Triticum aestivum L.) Grown Under Salt Stress Conditions

Fertilization of Mung bean (Vigna radiataL) is one of the most crucial management technique which effects crop growth and yield. Therefore the present study was carried out at Agricultural Research Station Kohat under rain fed conditions during spring 2017, to assess the response of mung bean (Vigna radiateL.) to three levels of iron (0, 2 and 5 kg ha-1) and three levels of zinc (0, 5 and 10 kg ha-1). The experiment was laid out in randomized complete design with split plot arrangement and replicated three times. The results revealed that application of Fe at the rate 5 kg ha-1and Zn at the rate 10 kg ha-1significantly increased biological yield, grain yield, straw yield, nodule numbers and weight by 5624 kg ha-1, 968 kg ha-1, 4655 kg ha-1, 35 and 0.67g respectively whereas the interaction was found non- significant. The nitrogen content in grains and straw was also significantly increased by 2.22% and 3.56% respectively with application of Fe at 5 kg ha-1and Zn at 10 kg ha-1, however their interaction was also found non-significant. Similarly the plant nitrogen uptake was also significantly increased by 323.33 kg ha-1with application of Fe at 5 kg ha-1and Zn at 10 kg ha-1.It was concluded that Fe and Zn enhanced mung bean productivity.

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Response of Mung Bean Crop to Different Levels of Applied Iron and Zinc

Soil pollution is a highlighted concern of modern society, particularly in developing countries. The Drosh-Shishi valley, which is a hilly region near Afghanistan with a land area of around 15,000 km2, is situated in the south of Chitral District (Pakistan) and has a population of approximately 450,000. Nowadays, this region is being explored for soil pollution, specifically heavy metals which pose a potential risk to human health. Therefore, our main goal was to investigate possible sources of heavy metals’ spread and to assess the content levels in soil and the associated risks for human. We collected 34 representative samples from transported sediments and 31 from agricultural crops. We analyzed the soil samples for the contents of Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn using ICP-OES analyzers. These values were used to obtain the contamination factor (CF) and to estimate the potential health risk caused by heavy metals according to the USEPA dose–response model. Our results suggest that the heavy metal pollution has a geogenic source, but it is also aggregated by chemical fertilizers used in farming. Regarding levels, most of the metals except Pb showed contents above the permissible level, with CF values from moderate to high. Overall, Cu and Ni showed a significant total cancer risk (TCR > 1 × 10−4) in children. Therefore, we conclude that heavy metal pollution is causing a serious threat to humans in this area, and we recommend that authorities should make more efforts in monitoring the heavy metals content in soils to reduce potential health risks.

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Aftab Jamal

Papers

Application of different organic manures in optimizing optimum yield for wheat in calcareous soil

Heavy metals distribution in different soil series of district Swabi, Khyber Pakhunkhawa, Pakistan

Beneficial Effect of Melatonin on Growth and Chlorophyll Content in Wheat (Triticum aestivum L.) Grown Under Salt Stress Conditions

Response of Mung Bean Crop to Different Levels of Applied Iron and Zinc

Assessment of the Ecological and Health Risks of Potentially Toxic Metals in Agricultural Soils from the Drosh-Shishi Valley, Pakistan