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Soil and air pollution caused by heavy metals and limestone dust are prevalent in urban environments and they are an alarming threat to the environment and humans. This study was designed to investigate the changes in morphological and physiological traits of three urban tree species seedlings (Bombax ceiba, Conocarpus lancifolius, and Eucalyptus camaldulensis) under the individual as well as synergetic effects of heavy metal lead (Pb) and limestone dust toxicities. The tree species were grown under controlled environmental conditions with nine treatments consisting of three levels of dust (0, 10, and 20 g) and three levels of Pb contaminated water irrigation (0, 5, and 10 mg L-1). The results depicted that the growth was maximum in T1 and minimum in T9 for all selected tree species. B. ceiba performed better under the same levels of Pb and limestone dust pollution as compared with the other two tree species. The B. ceiba tree species proved to be the most tolerant to Pb and limestone pollution by efficiently demolishing oxidative bursts by triggering SOD, POD, CAT, and proline contents under different levels of lead and dust pollution. The photosynthetic rate, stomatal conductance, evapotranspiration rate, and transpiration rate were negatively influenced in all three tree species in response to different levels of lead and dust applications. The photosynthetic rate was 1.7%, 3.1%, 7.0%, 11.03%, 16.2%, 23.8%, 24.8%, and 30.7%, and the stomatal conductance was 5%, 10.5%, 23.5%, 40%, 50.01%, 61.5%, 75%, and 90.9%, greater in T2, T3, T4, T5, T6, T7, T8, and T9 plants of B. ceiba, respectively, as compared to T1. Based on the findings, among these three tree species, B. ceiba is strongly recommended for planting in heavy metal and limestone dustpolluted areas followed by E. camaldulensis and C. lancifolius due to their better performance and efficient dust and heavy metal-scavenging capability. [ABSTRACT FROM AUTHOR]

One of the major environmental problems is the fast accumulation of brick kiln emissions near the peripheries of almost all urban centers. An enormous quantity of substandard coal, wood, rubber tires, or saw wood is used as fuel in these brick kilns, creating environmental pollution through carbon and heavy metals present in the emissions. The present study was designed to determine the distribution pattern of heavy metals in a soil–water-plant system under the influence of brick kiln emissions. Ash, soil (0–15 cm), water, and plant samples were collected from the adjacent areas of the brick kilns. Geo-accumulation index and contamination factors were used to assess the toxicity of metals to soil and plants. It was found that the concentrations of Cd in water, soil, coal, and plant samples were found in the range of 0.004–0.024 mg L−1, 0.02–0.66, 0.002–0.042, and 0.06 to 0.07 mg kg−1, respectively, while Pb concentration was found within the range of 0–0.08 mg L−1, 0.30–8.60, 0.011–0, and 0.01–0.08 mg kg−1 in water, soil, and plant samples, respectively. The concentration of Cd in brick kilns ash was in the range of 0–0.04 mg kg−1 while Pb was found within the range of 0.01–0.05 mg kg−1 for ash. Geo-accumulation index and contamination factor values for Cd were found higher suggesting proper pollution prevention measures to be implemented. Based on the results, it was concluded that Cd concentrations in soil, plants, and water samples were higher in the subject area due to brick kiln emissions and higher Cd concentrations in the fuel material. [ABSTRACT FROM AUTHOR]

The effect of organic amendments on phytoavailability of nickel (Ni) and other metals in soil may change with time due to transformation of organic matter. We investigated the residual effect of organic amendments (farm manure [FM], poultry manure [PM], pressmud [PrM], and activated carbon [AC]) to immobilize Ni and other metals in soil and absorption of metals by Egyptian clover. Fresh and dry weights of Egyptian clover increased significantly (p < 0.05) due to residual effect of amendments compared to control. Extractable Ni and other metals had significant positive correlation with residual organic matter in soil. Extractable manganese (Mn) in post-harvest soil of Egyptian clover increased compared with that of post-harvest soil of maize (previous crop). However, extractable copper (Cu) decreased with amendments. Copper was the maximum in control followed by AC. Zinc in soil decreased in FM and PrM treated pots but increased in pots amended with PM and AC. Concentration of Ni, Mn, and Cu was the minimum in shoots of those plants grown with AC amended pots compared to the control. It was concluded that AC was the most effective for immobilization of metals in soil which consequently decreased the concentration of metals in shoots of Egyptian clover. [ABSTRACT FROM AUTHOR]

We investigated effect of farm yard manure (FYM) and compost applied to metal contaminated soil at rate of 1% (FYM-1, compost-1), 2% (FYM-2, compost-2), and 3% (FYM-3, compost-3). FYM significantly (P < 0.001) increased dry weights of shoots and roots while compost increased root dry weight compared to control. Amendments significantly increased nickel (Ni) in shoots and roots of maize except compost applied at 1%. FYM-3 and -1 caused maximum Ni in shoots (11.42 mg kg−1) and roots (80.92 mg kg−1), respectively while compost-2 caused maximum Ni (14.08 mg kg−1) and (163.87 mg kg−1) in shoots and roots, respectively. Plants grown in pots amended with FYM-2 and compost-1 contained minimum Cu (30.12 and 30.11 mg kg−1) in shoots, respectively. FYM-2 and compost-2 caused minimum zinc (Zn) (59.08 and 66.0 mg kg−1) in maize shoots, respectively. FYM-2 caused minimum Mn in maize shoots while compost increased Mn in shoots and roots compared to control. FYM and compost increased the ammonium bicarbonate diethylene triamine penta acetic acid (AB-DTPA) extractable Ni and Mn in the soil and decreased Cu and Zn. Lower remediation factors for all metals with compost indicated that compost was effective to stabilize the metals in soil compared to FYM. [ABSTRACT FROM PUBLISHER]

Urbanization and industrialization have resulted in contamination of soils with heavy metals and other pollutants. Nickel (Ni) is one of the toxic metals, which adversely affect plant growth by altering different physiological and metabolic processes. Mineral nutrients can reduce toxic effects of Ni on physiological and metabolic functions of plants, thus improving plant growth. The role of calcium (Ca) to alleviate Ni toxicity in rice was investigated. Rice plants were grown with Ni (20 and 40 mg kg−1) and Ca (80 and 160 mg kg−1) in different combinations and without Ni and Ca as a control. Nickel (40 mg kg−1) significantly decreased shoot (54%) and root dry weights (54%), chlorophyll content (57%), the photosynthetic rate (two-fold), transpiration rate (34%) and stomatal conductance (39%) compared to control. Application of Ni (40 mg kg−1) increased the Ni concentration in shoots 22-fold and in roots 11-fold compared to control. Application of Ca (160 mg kg−1) reduced the adverse effects of Ni and the studied parameters improved to the maximum values compared to control. Calcium decreased the translocation of Ni towards the shoots that was evident from a lower translocation factor (42%) for the plants supplied with Ca compared to those grown without Ca (62%). The phytotoxicity induced by Ni on different growth and physiological parameters was alleviated by Ca as indicated by the minimum values of the phytotoxicity index for Ca fed plants (0) compared to those without Ca (2.6). [ABSTRACT FROM AUTHOR]

The use of organic amendments is a common practice in Pakistan to improve soil fertility. Organic amendments affect the chemical speciation and thus the bioavailability of heavy metals and their uptake and toxicity to plants. The present study evaluates the influence of organic amendments viz. farm yard manure (FM), poultry manure (PM), press mud (PrM) and activated carbon (AC) on nickel (Ni) bioavailability in soil, as well as its uptake into, and growth responses of, Trifolium alexandrinum. Pot experiments were conducted where T. alexandrinum was exposed to three different concentrations of Ni i.e., 30, 60 and 90 mg kg-1 in the form of NiCl2 solution in the presence and absence of organic amendments each applied at 15 g kg-1 soil. The results showed that the effect of organic amendments on Ni bioavailability and uptake by T. alexandrinum depended on the Ni concentration in the soil and the amendment type. Application of organic amendments generally increased Ni phytoavailability in soil and Ni uptake by plants at low Ni levels (Ni-0 and Ni-30) but decreased at higher levels (Ni-60 and Ni-90). [ABSTRACT FROM AUTHOR]

Lead is a highly toxic heavy metal, but its putative toxicity with respect to its speciation remains to unveil. In this study, Pb-induced toxicity to Vicia faba pigment contents was assessed against Pb speciation and accumulation. After a culture period of three weeks, V. faba seedlings were exposed to 5 μM of lead nitrate alone or chelated by citric acid (CA) or ethylenediaminetetraacetic acid (EDTA). The plants were treated for 1, 4, 8, 12 and 24 h in nutrient solution. Exposure to Pb-5 caused increased production of reactive oxygen species, lipid peroxidation and decrease in V. faba chlorophyll contents during 24 h. Lead-induced oxidative stress and toxicity to chlorophyll contents varied with the speciation of Pb. Addition of EDTA to Pb solution alleviated Pb-induced oxidative stress and toxicity to V. faba pigments by decreasing Pb accumulation in V. faba leaves. However, addition of citric acid to Pb did not affect Pb accumulation or toxicity to V. faba leaves. It is proposed that metal speciation plays an important role in Pb toxicity to V. faba pigment. Moreover, organic ligands vary greatly in terms of their ability to modify Pb phytoaccumulation and toxicity. [ABSTRACT FROM AUTHOR]

Wheat (Triticum aestivum L.) cultivation in cadmium (Cd) polluted soil is a core concern to food quality and food security all over the world. Cadmium toxicity is mainly associated with a Cd influx from contaminated soils to human via grain consumption. Organic amendments are widely used for Cd immobilization and enhancement in plant growth, but the residual effects of these amendments are mostly unknown. The present study addressed the long-term effects of organic amendments in contaminated soils by evaluating their residual effects on 3rd crop (wheat) in the sequence. Initially six organic amendments viz. rice husk biochar (RHB), wheat-straw biochar (WSB), cotton-stick biochar (CSB), poultry manure (PM), press mud (PrMd) and farm manure (FM) were applied once at a rate of 2% in Cd (50 mg kg−1) contaminated soil with wheat-rice rotation. After the harvest of wheat and rice crops, wheat (Var. Galaxy) was again grown in the same pots. Results revealed that plants grown under Cd stress (without any amendment) contain more tissue (root, shoot and grain) and soil AB-DTPA extractable Cd. The soil amended with RHB has shown lowest AB-DTPA extractable Cd (69% lower than control). Similarly, RHB application has significantly reduced wheat root, shoot and grain Cd concentrations compared to control and other amendments. Results have confirmed the effectiveness of RHB residual contents as an active amendment for restriction of Cd in non-bioavailable pool of soil and better growth and yield of wheat. • Residual effects of rice husk biochar (RHB) and press mud (PrMd) were higher compared to other amendments. • The increase in wheat growth and yield was highest in residual RHB treatment. • Cd immobilization index was highest in RHB treatment. • The grain Cd was below threshold level in RHB treatment. [ABSTRACT FROM AUTHOR]