Mar 19, 2018 - Department of Civil and Environmental Engineering, The Hong Kong University of ... State Key Laboratory of Hydro-Science and Engineering, ...
Article pubs.acs.org/est
Cite This: Environ. Sci. Technol. XXXX, XXX, XXX−XXX
Environmental Risks of Nano Zerovalent Iron for Arsenate Remediation: Impacts on Cytosolic Levels of Inorganic Phosphate and MgATP2− in Arabidopsis thaliana Weilan Zhang,† Irene M. C. Lo,*,†,⊥ Liming Hu,‡ Chia Pao Voon,§ Boon Leong Lim,§ and Wayne K. Versaw∥ †
Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Hong Kong, China ‡ State Key Laboratory of Hydro-Science and Engineering, Department of Hydraulic Engineering, Tsinghua University, Beijing 100084, China § School of Biological Sciences, the University of Hong Kong, Pokfulam, Hong Kong, China ∥ Department of Biology, Texas A&M University, College Station, Texas 77843, United States S Supporting Information *
ABSTRACT: The use of nano zerovalent iron (nZVI) for arsenate (As(V)) remediation has proven effective, but fullscale injection of nZVI into the subsurface has aroused serious concerns for associated environmental risks. This study evaluated the efficacy of nZVI treatment for arsenate remediation and its potential hazards to plants using Arabidopsis thaliana grown in a hydroponic system. Biosensors for inorganic phosphate (Pi) and MgATP2− were used to monitor in vivo Pi and MgATP2− levels in plant cells. The results showed that nZVI could remove As(V) from growth media, decrease As uptake by plants, and mitigate As(V) toxicity to plants. However, excess nZVI could cause Pi starvation in plants leading to detrimental effects on plant growth. Due to the competitive adsorption of As(V) and Pi on nZVI, removing As(V) via nZVI treatment at an upstream site could relieve downstream plants from As(V) toxicity and Pi deprivation, in which case 100 mg/L of nZVI was the optimal dosage for remediation of As(V) at a concentration around 16.13 mg/L.
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INTRODUCTION
accumulates and hinders the growth of wild vegetation but can also end up in crops, reducing the quality of agricultural products, entering food chains, and eventually affecting the human body.8,9 Consequently, effective remediation methods for subsurface As(V) removal have been widely investigated. Using engineered nanomaterials for environmental remediation has the potential to remove contaminants and increase the heavy metal and metalloid remediation efficiency.10 Among the engineered nanomaterials, nano zerovalent iron (nZVI) is the predominant reagent for in situ remediation due to its fast reaction rates and high heavy metal and metalloid adsorption capacity.11−14 nZVI is able to remove As(V) in contaminated water or soil through adsorption and surface precipitation processes.15,16 The number of arsenic contaminated sites remediated with nZVI has increased rapidly since its
Arsenic (As) is one of the most toxic and carcinogenic chemical elements arising from natural and anthropogenic sources. The concentration of As in industrial wastewater, especially from mining and smelting industries, can be up to 1000−2000 mg/ L.1,2 Wastewater without specific arsenic removal treatment poses significant risks to the surrounding environments.2,3 Besides the high-priority risk of arsenic to human health, a large body of literature also suggests that subsurface arsenic would be available and toxic to plants, and therefore pose a risk to the ecosystem.4,5 Inorganic As(V) (arsenate) is a common form of arsenic found in water supplies and is the main arsenic species in aerobic soils.6 According to previous studies, the primary cause of As(V) toxicity in plants is the formation of unstable ADP-As and the resulting disruption of energy flows in cells.7 As(V) ions enter root cells through inorganic phosphate (Pi) transporters because of their chemical similarities. Toxicity results from the replacement of Pi with As(V) in adenosine triphosphate (ATP) synthesis, depriving cells from energy sources.4,7 Excessive As(V) in polluted water and soil not only © XXXX American Chemical Society
Received: Revised: Accepted: Published: A
December 29, 2017 February 13, 2018 March 19, 2018 March 19, 2018 DOI: 10.1021/acs.est.7b06697 Environ. Sci. Technol. XXXX, XXX, XXX−XXX
Article
Environmental Science & Technology introduction in 2001.17 However, information on the potential environmental impact of full-scale nZVI application is scarce. Few studies have investigated the toxicity of nZVI toward plants.18 Libralato et al. did not detect any toxic effects of nZVI at concentrations ranging from 4.81 to 33,560 mg/L on Lepidium sativum, Sinapis alba, and Sorghum saccharatum.19 ElTemsah and Joner described an inhibiting effect of nZVI at concentrations higher than 250 mg/L on the germination and growth of Lolium perenne, Hordeum vulgare, and Linum usitatissimum.20 Ma et al. evaluated the toxicity of nZVI in the range 0−1000 mg/L to cattail (Typha latifolia) and hybrid poplar (Populous deltoids × Populous nigra) in a hydroponic system. 21 After 4 weeks of exposure, nZVI at high concentrations (>200 mg/L) exhibited strong toxic effects (lower biomass and transpiration) on cattail and hybrid poplar, but nZVI at lower concentrations (
