Assessing arsenic toxicity from tin mine pounds using Wolffia
Assessing Arsenic Toxicity from Tin Mine Ponds using Wolffia
หัวหน้าโครงการ
:
Raymond James Ritchie
ทีมวิจัย
:
Raymond James Ritchie
หัวหน้าโครงการ
วันที่เริ่มโครงการ
:
31 ก.ค. 2555
วัตถุประสงค์
:
The aquatic plant Wolffia will be used to study of arsenic accumulation and metabolism. Wolffia is a very small aquatic angiosperm with no roots and is very small (? 1 mm) and so is suitable for laboratory studies in simple culture tubes and on agar plates. It is fast growing (t2 ? 2-3 days) and can be grown in fully defined media and so biophysical analysis of uptake is feasible in particular dealing with the redox properties of arsenate (As(V)) (HAsO42-) and arsenite (As(III)) (As(OH)3). The very simple anatomy of Wolffia will help in the analysis and interpretation of arsenic uptake studies. Wolffia accumulates As(III) throughout the frond and so has greater phytoremediation potential than rooted vascular plants including its relative Lemna (Mkandawire & Dudel 2005; Zhang et al 2009; Rahman & Hasegawa 2011). pH and redox potential affect the availability of arsenic and the form in which it is present. Effects of arsenic will be measured in growth studies, photosynthesis studies using PAM (Pulse Amplitude Modulation) fluorometry and analysis of uptake of arsenic using chromatography to separate different forms of arsenic and AAS assay. Competition studies will be made to characterise discrimination between arsenate (As(V)) and phosphate. As(V)/Pi competition is well known in qualitative terms but the discrimination ratio between these two substrates for phosphate transporters has not been quantified. Arsenite (As(III)) is much more toxic than As(V) and enters cells by a different mechanism than arsenate. As(III) is not treated as an analogue of phosphate and enters cells through aquaporins. It behaves as an analogue of silicic acid (Si(OH)3). Interactions between As(III) and Silicate uptake have not been studied in detail.
Wolffia is used as a vegetable in SE-Asia and is known as watermeal or khai-nam (Bhanthumnavin & McGarry 1971). Arsenic accumulation by Wolffia is of direct public health importance in Thailand (Zhang et al 2009; Duester et al 2011; Rahman & Hasegawa 2011) but might not be a dangerous hyperaccumulator like ferns (Sridokchan et al 2005) and some flowering plants (Chinakovid et al 2008). The very small size, rapid growth and easy handling of the plant makes it also a very promising species for bioassay and bioindicator applications. The results of the study will help in assessing the public health problems associated with acid soils and abandoned tin mines. Arsenic accumulation has received great attention in rice (Berg et al 2007; Brammer & Ravenscroft 2009; Li et al 2009; Carey et al 2009; Ma et al 2009; Williams et al 2009; Wu C et al 2011; Wu Z et al 2011).
The proposed study using Wolffia has the advantage that they can be done on a very small scale in the laboratory rather than slow studies using rice etc. The very small scale of the experiments also contributes significantly to the safety aspects of working with arsenic compounds. The smaller the scale the more inherently safe are the experiments.
