In recent decades, heavy metal contamination in soil adjacent to chromated copper arsenate (CCA) treated wood has received increasing attention. This study was conducted to determine the pollution level (PL) based on the concentrations of Cr, Cu and As in soils and to evaluate the remediative capacity of native plant species grown in the CCA contaminated site, Gangwon Province, Korea. The pollution index (PI), integrated pollution index (IPI), bioaccumulation factors (BAFshoots and BAFroots) and translocation factor (TF) were determined to ensure soil contamination and phytoremediation availability. The 19 soil samples from 10 locations possibly contaminated with Cr, Cu and As were collected. The concentrations of Cr, Cu and As in the soil samples ranged from 50.56-94.13 mg kg-1, 27.78-120.83 mg kg-1, and 0.13-9.43 mg kg-1, respectively. Generally, the metal concentrations decreased as the distance between the CCA-treated wood structure and sampling point increased. For investigating phytoremediative capacity, the 19 native plant species were also collected in the same area with soil samples. Our results showed that only one plant species of Iris ensata, which presented the highest accumulations of Cr (1120 mg kg-1) in its shoot, was identified as a hyperaccumulator. Moreover, the relatively higher values of BAFshoot (3.23-22.10) were observed for Typha orientalis, Iris ensata and Scirpus radicans Schk, suggesting that these plant species might be applicable for selective metal extraction from the soils. For phytostabilization, the 15 plant species with BAFroot values >1 and TF values 1 were suitable; however, Typha orientalis was the best for Cr.

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Chelating agents added to contaminated soils may increase solubility and phytoextraction efficiency of soil metals. However, they can create negative effects on soil biological quality. A 90-day incubation experiment was conducted to evaluate mixed effects of chelating agents and poultry manure on changes in available Cd, Pb and As, CO2-C efflux, microbial biomass C, dissolved organic C (DOC), and N mineralization in metal-polluted agricultural soil. Application of poultry manure resulted in a considerable increase in soil pH, DOC, CO2-C efflux, net N mineralization, net N nitrification, and microbial biomass C compared to those in unmanured soil. Availability of arsenic increased twice in manure amended soil due to changes in pH and DOC. However, adding poultry manure did not affect the concentrations of available Pb and Cd compared to those in control soil. Chelating agents increased CO2-C efflux, DOC, and metal availability but decreased microbial biomass C and net N mineralization. Maximum decrease in microbial biomass C, net N mineralization, and net N nitrification, was observed in EDTA applied soil possibly due to high metal availability to soil microorganisms. Overall results revealed that the application of synthetic chelators in combination with poultry manure enhances available As and demonstrates better environment for soil biota.

The aim of this study was to investigate the concentrations and pollution status of heavy metals (Cu, Cd, Ni, Pb, Zn and Cr) in the mangrove surface sediments from the Farasan Island, Coast of Red Sea, Saudi Arabia. The ability of mangroves (Avicennia marina) to accumulate and translocate heavy metal within their different compartments was also investigated. Five sampling sites were chosen for collection of sediments and different compartments (leaf, branch and root) of A. marina. The results showed that the maximum and average concentrations of Cd, Cu and Pb in the studied area exceeded their world average concentration of shale. Additionally, only the maximum concentration of Zn exceeded its world average shale concentration. Based on the quality guidelines of sediment (SQGs), the collected sediment samples were in moderate to heavy rate for Cu, non-polluted to heavy rate for Pb and Zn, and non-polluted to moderate rate for Cr and Ni. The average metal concentrations of A. marina in the studied area were observed in the order Cu (256.0–356.6 mg kg−1) > Zn (29.5–36.8 mg kg−1) > Cr (8.15–14.9 mg kg−1) > Ni (1.37–4.02 mg kg−1) > Cd (not detectable-1.04 mg kg−1) > Pb (not detectable). Based on bio-concentration factors (BCF), their most obtained values were considered too high (> 1), suggesting that A. marina can be considered as a high-efficient plant for bioaccumulation of heavy metals. Among all metals, Cu and Cr were highly bio-accumulated in different parts of A. marina. In terms of heavy metal contamination control via phyto-extraction, our findings suggest also that A. marina may be classified as potential accumulator for Cu in aboveground parts, as indicated by higher metal accumulation in the leaves combined with bio-concentration factor (BCF) and translocation factor (TF) values >1.

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The concentrations of nine heavy metals (Fe, Mn, Zn, Cu, Ni, Cd, Cr, Co, and Pb) in soil samples of Arabian Gulf coast, Saudi Arabia, were investigated. Sediment Quality Guideline (SQGs), SQG-Quotient (SQG-Q), toxicity degree index (TDI), enrichment factor (EF), and multivariate analysis, including principle component analysis (PCA) and hierarchical cluster analysis (HCA), were used to measure heavy metals of concern in the study area and to identify their possible sources. The results showed that the concentrations of different heavy metals were 530–5,700 mg kg-1 for Fe; 9-150 mg kg−1 for Mn and 8-69 mg kg−1 for Zn; 1-21 mg kg−1 for Cu and not detectable-17 mg kg−1 for Ni; 6.9-130 mg kg−1 for Cr and not detectable-5 mg kg−1 for Co; and not detectable-24 mg kg−1 for Pb. Based on SQGs, only the maximum and mean Cr concentrations of study area were in heavy and moderate rates of pollution, respectively. The values of SQG-Q and TDI revealed that the investigated sampling points showed the lowest potential of adverse biological effects. The considerable number of collected soil samples has relatively higher EF values of 5–20 for Zn, Cu, Cr, and Pb, suggesting that these four metals may be derived from anthropogenic origin. Multivariate analysis also confirmed this finding that the sources of Zn, Cu, and Pb resulted primarily from anthropogenic sources, whereas Co, Ni, Fe, and Mn were mainly attributed to lithogenic sources. It could be generally concluded that it is possible to use multivariate analyses in combination with EF values as useful tools to identify the natural or anthropogenic sources of heavy metals in soils.

Many studies have reported the positive effect of biochar on soil carbon sequestration and soil fertility improvement in acidic soils. However, biochar may have different impacts on calcareous sandy soils. A 90-day incubation experiment was conducted to quantify the effects of woody waste biochar (10 g kg-1) on CO2–C emissions, K2SO4-extractable C and macro-(N, P and K) and micro-(Fe, Mn, Zn and Cu) nutrient availability in the presence or absence of poultry manure (5 g kg-1 soil). The following six treatments were applied: (1) conocarpus (Conocarpus erectus L.) waste (CW), (2) conocarpus biochar (BC), (3) poultry manure (PM), (4) PM + CW, (5) PM + BC and (6) untreated soil (CK). Poultry manure increased CO2–C emissions and K2SO4-extractable C, and the highest increases in CO2–C emission rate and cumulative CO2–C and K2SO4-extractable C were observed for the PM + CW treatment. On the contrary, treatments with BC halted the CO2–C emission rate, indicating that the contribution of BC to CO2–C emissions is negligible compared with the soils amended with CW and PM. Furthermore, the combined addition of PM + BC increased available N, P and K compared with the PM or BC treatments. Overall, the incorporation of biochar into calcareous soils might have benefits in carbon sequestration and soil fertility improvement.

Biochar is a carbon-rich product obtained by biomass pyrolysis and considered a mean of carbon sequestration. In this research, a sandy calcareous soil from the Farm of the College of Food & Agriculture Sciences, King Saud University, Saudi Arabia, was amended with either woody waste of Conocarpus erectus L. (CW) or the biochar (BC) produced from CW at rates of 0 (control), 10, 30 and 50 g kg−1. The effects of the amendments on soil pH, dissolved organic carbon (DOC), microbial biomass carbon (MBC), CO2 emission and metabolic quotient (qCO2) of the sandy calcareous soil were studied in a 60-d incubation experiment. The results showed that the addition of CW led to a significant decrease in soil pH compared to the control and the addition of BC. The CO2-C emission rate was higher in the first few days of incubation than when the incubation time progressed. The cumulative CO2-C emission from the soil amended with CW, especially at higher rates, was higher (approximately 3- to 6-fold) than that from the control and the soil amended with BC. The BC-amended soil showed significant increases in CO2-C emission rate during the first days of incubation as compared to the non-amended soil, but the increase in cumulative CO2-C emission was not significant after 60 d of incubation. On the other hand, CW applications resulted in considerably higher cumulative CO2-C emission, MBC and DOC than the control and BC applications. With the exception of 0 day (after 1 h of incubation), both CW and BC applications led to lower values of qCO2 as compared to the control. The power function kinetic model satisfactorily described the cumulative CO2-C emission. Generally, the lowest values of CO2 emission were observed in the soil with BC, suggesting that the contribution of BC to CO2 emission was very small as compared to that of CW.

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