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Trace element dynamics of biosolids-derived microbeads
Wijesekara, Hasintha,Bolan, Nanthi S.,Bradney, Lauren,Obadamudalige, Nadeeka,Seshadri, Balaji,Kunhikrishnan, Anitha,Dharmarajan, Rajarathnam,Ok, Yong Sik,Rinklebe, Jö,rg,Kirkham, M.B.,Vithanage, M Elsevier 2018 CHEMOSPHERE - Vol.199 No.-
<P><B>Abstract</B></P> <P>This study focused on quantifying and characterising microbeads in biosolids (i.e., treated sewage sludge), and in examining interactions of microbeads with trace elements when biosolids are added to soil. Under laboratory conditions, batch experiments were conducted to investigate the adsorption of Cu onto pure and surface modified microbeads suspended in soil. The ecotoxicity of microbead-metal complexes to soil microbial activities was also investigated by monitoring basal respiration and dehydrogenase activity. Concentrations of the microbeads were 352, 146, 324, and 174 particles kg<SUP>−1</SUP> biosolids for ≤50, 50–100, 100–250, 250–1000 μm size fractions, respectively. The Scanning Electron Microscope (SEM) images illustrated wrinkled and fractured surfaces due to degradation. The adsorption of dissolved organic matter onto microbeads was confirmed through FT-IR microscopy, while using Inductively Coupled Plasma Mass Spectrometer (ICP-MS) the presence of trace metals including Cd (2.34 ng g<SUP>−1</SUP>), Cu (180.64 ng g<SUP>−1</SUP>), Ni (12.69 ng g<SUP>−1</SUP>), Pb (1.17 ng g<SUP>−1</SUP>), Sb (14.43 ng g<SUP>−1</SUP>), and Zn (178.03 ng g<SUP>−1</SUP>) was revealed. Surface modified microbeads were capable of adsorbing Cu compared to the pure microbeads, which may be attributed to the complexation of Cu with dissolved organic matter associated with the microbeads in the matrix. It was further revealed that the biosolids derived microbead-metal complexes decreased soil respiration (up to ∼ 26%) and dehydrogenase activity (up to ∼ 39%). Hence, microbeads reaching biosolids during wastewater treatment are likely to serve as a vector for trace element contamination, transportation, and toxicity when biosolids are applied to soil.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Biosolids are a major source for microbeads in soil. </LI> <LI> A first-time study on microbial toxicity of biosolids-derived microbeads. </LI> <LI> Microbeads serve as a vector for transportation of trace elements in soil. </LI> <LI> Dissolved organic matter enhanced the adsorption of trace elements by microbeads. </LI> <LI> Microbeads decreased microbial respiration and dehydrogenase activity in soil. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Bradney, Lauren,Wijesekara, Hasintha,Palansooriya, Kumuduni Niroshika,Obadamudalige, Nadeeka,Bolan, Nanthi S.,Ok, Yong Sik,Rinklebe, Jö,rg,Kim, Ki-Hyun,Kirkham, M.B. Pergamon 2019 Environment international Vol.131 No.-
<P><B>Abstract</B></P> <P>Particulate plastics in the terrestrial and aquatic environments are small plastic fragments or beads (i.e., 5 mm down to the nanometre range). They have been frequently referred to as ‘micro-plastics’ or ‘nano-plastics’. Research has identified particulate plastics as a vector for toxic trace elements in the environment. The adsorption of toxic trace elements by particulate plastics may be facilitated by their high surface area and functionalized surfaces (e.g., through the attachment of natural organic matter). Other factors, such as environmental conditions (e.g., pH and water salinity), surface charge, and trace element oxidation status, also influence the adsorption of trace elements onto particulate plastics. Because of their small size and persistence, particulate plastics and the associated toxic trace elements are readily ingested and accumulated in many terrestrial and aquatic organisms. Thus, these plastics can have severe environmental consequences, such as the development of metal toxicity, within aquatic and terrestrial organisms. Humans could also become exposed to particulate plastics through food chain contamination and airborne ingestion. This review provides an overview of the sources of particulate plastics in the environment. To this end, we describe particulate plastics made of synthetic polymers, their origin, and characteristics with emphasis on how particulate plastics and associated toxic trace elements contaminate terrestrial and aquatic ecosystems. Future research needs and strategies are discussed to help reduce the environmental risks of particulate plastics as a potent vector for the transportation of toxic trace elements.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Particulate plastics include microplastics and nanoplastics. </LI> <LI> The review covers the ecological and human health impacts of particulate plastics. </LI> <LI> Trace-element-sorbed particulate plastics damage aquatic and terrestrial ecosystems. </LI> <LI> Dissolved organic matter facilitates trace element sorption onto particulate plastics. </LI> <LI> Particulate plastics pose human health threats by entering the food chain. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Phosphorus-cadmium interactions in paddy soils
Seshadri, B.,Bolan, N.S.,Wijesekara, H.,Kunhikrishnan, A.,Thangarajan, R.,Qi, F.,Matheyarasu, R.,Rocco, C.,Mbene, K.,Naidu, R. Elsevier Scientific Pub. Co 2016 Geoderma Vol.270 No.-
<P>Regular application of phosphate (P) fertilisers has been identified as the main source of heavy metal(loid) contamination including cadmium (Cd) in agricultural soils. Some of these P fertilisers that act as a source of Cd contamination of soils have also been found to act as a sink for the immobilisation of this metal(loid). In paddy soils, redox reactions play an important role in the (im)mobilisation of nutrients and heavy metal(loid)s, as a result of flooding of the rice plains. Although a number of studies have examined the potential value of P compounds in the immobilisation of metals in contaminated soils, there has been no comprehensive review on the mechanisms involved in the P-induced (im)mobilisation of Cd in paddy soils. There are a number of factors that influences P induced Cd (im)mobilisation in paddy soils that include pH, redox reactions, liming effect, rhizosphere acidification and root iron plaques. Following a brief overview of the reactions of Cd and common P compounds that are used as fertiliser in soils, the review focuses on the above mentioned mechanisms for the (im)mobilisation of Cd by P compounds in paddy soils. The role of iron plaques on Cd status in soil and rice plants is also discussed followed by a summary and future research needs. (C) 2015 Elsevier B.V. All rights reserved.</P>
In Vitro and Intracellular Antioxidant Activities of Brown Alga Eisenia bicyclis
Yoon, Na-Young,Lee, Sang-Hoon,Wijesekara, Isuru,Kim, Se-Kwon The Korean Society of Fisheries and Aquatic Scienc 2011 Fisheries and Aquatic Sciences Vol.14 No.3
The antioxidant activities of a methanolic extract of Eisenia bicyclis and its organic solvent fractions, including dichloromethane ($CH_2Cl_2$), ethyl acetate (EtOAc), n-butanol (n-BuOH), and water ($H_2O$) fractions, were investigated. Scavenging activities against DPPH, hydroxyl, superoxide anion, and peroxynitrite radicals were evaluated using electron spin resonance spectrometry; intracellular reactive oxygen species (ROS) were evaluated by a 2',7'-dichlorofluorescein diacetate assay using RAW264.7 mouse macrophages. The antioxidant activities of the individual fractions were: EtOAc>n-BuOH>$CH_2Cl_2$ >$H_2O$. The EtOAc fraction exhibited strong radical scavenging activity and a significantly reduced ROS level in RAW264.7 cells. Moreover, the phenolic contents of the extract and fractions followed the same order as their radical scavenging activities. Our results indicate that E. bicyclis is a valuable natural source of antioxidants that may be applicable to the functional food industry.
Vithanage, M.,Rajapaksha, A. U.,Wijesekara, H.,Weerarathne, N.,Ok, Y. S. Springer Science + Business Media 2014 Environmental Earth Sciences Vol.71 No.2
Inorganic arsenic (As) pesticides have been widely used for decades in many countries. However, insufficient data are available on the chemical speciation of inorganic arsenicals in tropical paddy soils. Inorganic As-containing pesticides were used in tropical countries, a few decades ago, however, their fate have not been studied. Hence, the objective of this study was to determine fractionation of inorganic arsenicals and to assess As lability with/without fertilizer application using a static incubation experiment. Eight soils from wet and dry regions of Sri Lanka were amended with 1,000 mg/kg arsenate for this purpose. The FT-IR and XRF results suggested that soils in the wet region were rich in Fe/Al-oxides. Paddy soils in the dry zone showed high As lability. These low-humic gley soils have low Fe/Al oxyhydroxide and alkaline pH. In contrast, the wet zone had soils with higher As retention capacity, high amounts of Fe/Al oxyhydroxide, and acidic pH. Arsenic lability increased considerably 30 days after fertilizer application. Overall, As lability was mainly influenced by soil mineralogical and chemical properties, i.e., Fe/Al oxyhydroxide, pH, organic matter, and fertilizer application.
The potential value of biochar in the mitigation of gaseous emission of nitrogen
Thangarajan, Ramya,Bolan, Nanthi S.,Kunhikrishnan, Anitha,Wijesekara, Hasintha,Xu, Yilu,Tsang, Daniel C.W.,Song, Hocheol,Ok, Yong Sik,Hou, Deyi Elsevier 2018 Science of the Total Environment Vol.612 No.-
<P><B>Abstract</B></P> <P>Nitrogen (N) losses through gaseous emission of ammonia (NH<SUB>3</SUB>) and nitrous oxide (N<SUB>2</SUB>O) can contribute to both economic loss and environmental degradation. This study examined the effect of biochar and a chemical nitrification inhibitor, dicyandiamide (DCD), on N transformation and N losses via gaseous emission of NH<SUB>3</SUB> and N<SUB>2</SUB>O from agricultural soils treated with a range of organic and inorganic N sources. The addition of DCD reduced N<SUB>2</SUB>O emission from both organic and inorganic N sources treated soils by 75%, but increased ammonium (NH<SUB>4</SUB> <SUP>+</SUP>) concentration and subsequently induced high NH<SUB>3</SUB> emission from the soils. In contrast, the addition of biochar reduced both N<SUB>2</SUB>O and NH<SUB>3</SUB> emissions from organic and inorganic N sources treated soils by 23% and 43%, respectively. The effectiveness of biochar and DCD in reducing NH<SUB>3</SUB> volatilization and N<SUB>2</SUB>O emission depends on the nature of the N sources and their initial mineral N concentration. The study demonstrated that biochar can be used to mitigate N losses resulting from NH<SUB>3</SUB> volatilization and N<SUB>2</SUB>O emission.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Biochar and dicyandiamide (DCD) effects on N transformation and losses were studied. </LI> <LI> DCD decreased N<SUB>2</SUB>O emission from N sources applied soil but increased NH<SUB>3</SUB> emission. </LI> <LI> Although DCD significantly reduced N<SUB>2</SUB>O emission, biochar decreased total N loss by 25%. </LI> <LI> Biochar can replace chemical nitrification inhibitors thereby mitigating gaseous N loss. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>