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Ecotoxicology and Human Environmental Health
Environmental Risks of Nano Zero-Valent Iron for Arsenate Remediation: Impacts on Cytosolic Levels of Inorganic Phosphate and MgATP in Arabidopsis thaliana 2-
Weilan Zhang, Irene M. C. Lo, Liming Hu, Chia Pao Voon, Boon L. Lim, and Wayne K. Versaw Environ. Sci. Technol., Just Accepted Manuscript • DOI: 10.1021/acs.est.7b06697 • Publication Date (Web): 19 Mar 2018 Downloaded from http://pubs.acs.org on March 19, 2018
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Environmental Science & Technology
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Environmental Risks of Nano Zero-Valent Iron for Arsenate Remediation:
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Impacts on Cytosolic Levels of Inorganic Phosphate and MgATP2- in
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Arabidopsis thaliana
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Weilan Zhang1, Irene M. C. Lo1,*, Liming Hu2, Chia Pao Voon3, Boon Leong Lim3, Wayne K.
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Versaw4
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and Technology, Hong Kong, China
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Department of Civil and Environmental Engineering, The Hong Kong University of Science
State Key Laboratory of Hydro-Science and Engineering, Department of Hydraulic
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Engineering, Tsinghua University, Beijing 100084, China
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School of Biological Sciences, the University of Hong Kong, Pokfulam, Hong Kong, China
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Department of Biology, Texas A&M University, College Station, TX 77843, USA
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*
Corresponding author: Email:
[email protected]; Fax: 852-23581534; Tel: 852-23587157
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TOC Art
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Abstract: The use of nano zero-valent iron (nZVI) for arsenate (As(V)) remediation has proven
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effective, but full-scale injection of nZVI into the subsurface has aroused serious concerns for
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associated environmental risks. This study evaluated the efficacy of nZVI treatment for arsenate
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remediation and its potential hazards to plants using Arabidopsis thaliana grown in a hydroponic
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system. Biosensors for inorganic phosphate (Pi) and MgATP2- were used to monitor in vivo Pi
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and MgATP2- levels in plant cells. The results showed that nZVI could remove As(V) from
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growth media, decrease As uptake by plants, and mitigate As(V) toxicity to plants. However,
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excess nZVI could cause Pi starvation in plants leading to detrimental effects on plant growth.
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Due to the competitive adsorption of As(V) and Pi on nZVI, removing As(V) via nZVI treatment
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at an upstream site could relieve downstream plants from As(V) toxicity and Pi deprivation, in
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which case 100 mg/L of nZVI was the optimal dosage for remediation of As(V) at a
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concentration around 16.13 mg/L.
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Keywords: Arabidopsis, arsenate, biosensor, nano zero valent iron
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Introduction
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Arsenic (As) is one of the most toxic and carcinogenic chemical elements arising from natural
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and anthropogenic sources. The concentration of As in industrial wastewater, especially from
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mining and smelting industries, can be up to 1000-2000 mg/L.1, 2 Wastewater without specific
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arsenic removal treatment poses significant risks to the surrounding environments.
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the high-priority risk of arsenic to human health, a large body of literature also suggests that
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subsurface arsenic would be available and toxic to plants, and therefore pose a risk to the
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ecosystem.4, 5 Inorganic As(V) (arsenate) is a common form of arsenic found in water supplies
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and is the main arsenic species in aerobic soils.6 According to previous studies, the primary
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Besides
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cause of As(V) toxicity in plants is the formation of unstable ADP-As and the resulting
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disruption of energy flows in cells.7 As(V) ions enter root cells through inorganic phosphate (Pi)
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transporters because of their chemical similarities. Toxicity results from the replacement of Pi
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with As(V) in adenosine triphosphate (ATP) synthesis, depriving cells from energy sources.4, 7
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Excessive As(V) in polluted water and soil not only accumulates and hinders the growth of wild
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vegetation, but can also end up in crops, reducing the quality of agricultural products, entering
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food chains, and eventually affecting the human body.8, 9 Consequently, effective remediation
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methods for subsurface As(V) removal have been widely investigated.
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Using engineered nanomaterials for environmental remediation has the potential to
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remove contaminants and increase the heavy metal and metalloid remediation efficiency.10
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Among the engineered nanomaterials, nano zero-valent iron (nZVI) is the predominant reagent
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for in-situ remediation due to its fast reaction rates and high heavy metal and metalloid
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adsorption capacity.11-14 nZVI is able to remove As(V) in contaminated water or soil through
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adsorption and surface precipitation processes.15, 16 The number of arsenic contaminated sites
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remediated with nZVI has increased rapidly since its introduction in 2001.17 However,
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information on the potential environmental impact of full-scale nZVI application is scarce. Few
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studies have investigated the toxicity of nZVI towards plants.18 Libralato et al. did not detect any
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toxic effects of nZVI at concentrations ranging from 4.81 to 33,560 mg/L on Lepidium sativum,
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Sinapis alba, and Sorghum saccharatum.19 El-Temsah and Joner described an inhibiting effect of
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nZVI at concentrations higher than 250 mg/L on the germination and growth of Lolium perenne,
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Hordeum vulgare, and Linum usitatissimum.20 Ma et al. evaluated the toxicity of nZVI in the
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range 0-1000 mg/L to cattail (Typha latifolia) and hybrid poplar (Populous deltoids×Populous
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nigra) in a hydroponic system.21 After 4 weeks of exposure, nZVI at high concentrations (>200
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mg/L) exhibited strong toxic effects (lower biomass and transpiration) on cattail and hybrid
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poplar, but nZVI at lower concentrations (
