Heng Yi Teah

Accumulation of heavy metals and trace elements in fluvial sediments received effluents from traditional and semiconductor industries

Metal accumulation in sediments threatens adjacent ecosystems due to the potential of metal mobilization and the subsequent uptake into food webs. Here, contents of heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn) and trace elements (Ga, In, Mo, and Se) were determined for river waters and bed sediments that received sewage discharged from traditional and semiconductor industries. We used principal component analysis (PCA) to determine the metal distribution in relation to environmental factors such as pH, EC, and organic matter (OM) contents in the river basin. While water PCA categorized discharged metals into three groups that implied potential origins of contamination, sediment PCA only indicated a correlation between metal accumulation and OM contents. Such discrepancy in metal distribution between river water and bed sediment highlighted the significance of physical-chemical properties of sediment, especially OM, in metal retention. Moreover, we used Se XANES as an example to test the species transformation during metal transportation from effluent outlets to bed sediments and found a portion of Se inventory shifted from less soluble elemental Se to the high soluble and toxic selenite and selenate. The consideration of environmental factors is required to develop pollution managements and assess environmental risks for bed sediments.

Adsorption of tetracycline on Fe (hydr)oxides: effects of pH and metal cation (Cu2+, Zn2+ and Al3+) addition in various molar ratios

Iron (Fe) (hydr)oxides control the mobility and bioavailability of tetracycline (TC) in waters and soils. Adsorption of TC on Fe (hydr)oxides is greatly affected by polyvalent metals; however, impacts of molar metal/TC ratios on TC adsorptive behaviours on Fe (hydr)oxides remain unclear. Results showed that maximum TC adsorption on ferrihydrite and goethite occurred at pH 5–6. Such TC adsorption was generally promoted by the addition of Cu2+, Zn2+ and Al3+. The greatest increase in TC adsorption was found in the system with molar Cu/TC ratio of 3 due to the formation of Fe hydr(oxide)–Cu–TC ternary complexes. Functional groups on TC that were responsible for the complexation with Cu2+shifted from phenolic diketone groups at Cu/TC molar ratio < 1 to amide groups at Cu/TC molar ratio ≥ 1. For the addition of Al3+, the complexation only took place with phenolic diketone groups, resulting in the enhanced TC adsorption at a molar Al/TC ratio of 1. However, TC adsorption decreased for Al/TC molar ratio > 1 as excess Al3+ led to the competitive adsorption with Al/TC complexes. For the Zn2+ addition, no significant correlation was found between TC adsorption capacity and molar Zn/TC ratios.

Capacity and recycling of polyoxometalate applied in As(III) oxidation by Fe(II)-Amended zero-valent aluminum

Arsenic remediation is often initiated by oxidizing As(III) to As(V) to alleviate its toxicity and mobility. Due to the easy availability, zero-valent Al (ZVAl) like Al can was considered as potential alternatives to facilitate As(III) oxidation. This study determined the capability and recycling of polyoxometalate (POM) to catalyze As(III) oxidation in Fe(II)-amended ZVAl systems. POM acquired electrons from ZVAl more effectively at pH 1 than at pH 2. While 76% of the reduced POM [POM(e-)] reacted with O2(g) to generate H2O2 at pH 1, only 60% of POM(e-) was used to produce H2O2 at pH 2. The remaining POM(e-) was oxidized by the generated H2O2. Such additional consumption of POM(e-) and H2O2 led to the incomplete As(III) oxidation in the system without residual ZVAl and emphasized the need for a continuous electron supply from ZVAl to compensate the depletion of POM(e-). After the hydrolyzation at pH 6.0, the XANES data evidenced that not only As(V) but WO4 released from the POM retained on surfaces of Al/Fe hydroxides. The competition for sorption sites on Al/Fe hydroxides between As(V) and WO4 led to the incomplete As removal. Despite the loss of WO4, the POM re-polymerized at pH 1 still showed the comparable capability to catalyze As(III) oxidation with original POM. This study revealed electron transfer pathways from ZVAl to As(III) as catalyzed by POM and evidenced the effective POM recycling after As removal, which lowers the cost of POM application and turns the ZVAl/Fe(II)/POM/O2 system into a practical strategy for As remediation.

Drawing Lessons from the Minamata Incident for the General Public: Exercise on Resilience, Minamata Unit AY2014

This chapter introduces the Minamata Unit, a GPSS-GLI Exercise on Resilience conducted around Minamata City, Kumamoto Prefecture, in Japan. The disruption caused by Minamata mercury pollution persists even 60 years after the incidents. Such a long history of development can provide invaluable insights into the study of the impact of industrial pollution to a society, which includes the significance of identifying new pollutants, the intricate social tension between victims and local community, and the urge to heal the strained bonds. Drawing lessons from the Minamata incident can prevent and mitigate similar incidents in developing countries, where environmental regulation is typically less stringent than in developed countries. In the present chapter, the authors describe the outcomes of a week-long field exercise in Minamata, designed for students of sustainability science. The aims of the unit were for participants to understand the complexities of the Minamata incident, not only the causal relationship between the pollutant and its impact on human health, but also the impacts the disease had on the society. Also, it attempted to examine the responsibility of scientists and the government, especially when certain issues regarding the case remain scientifically uncertain, by redefining the issue in the contemporary context. In order to facilitate learning by the participants of the unit presented in this chapter and students of future units, the exercise organisers requested the production of educational materials as the final output. Students were divided into three working groups, each tasked with the development of a different type of media material, namely blog posting , video production , and game development. The prearranged field activities included stakeholder interviews, site visits, and an intensive group work. Overall, the student groups completed the production of the tangible outputs, though their effectiveness in reaching the target audience and helping future sustainability science students require further analysis.

Designing Field Exercises with the Integral Approach for Sustainability Science: A Case Study of the Heihe River Basin, China

This chapter introduces one of the GPSS-GLI exercises, the Oasis Unit, which has been conducted annually in northwestern China. The unit aims to equip the students who take it with a wide knowledge base and leadership competency, and is thus strongly field-oriented. The Integral Approach proposed by Ken Wilber is applied when designing this unit, which provides an interdisciplinary and transdisciplinary framework for synthesizing the complex problems of sustainability, as well as allowing the inclusion of methodologies from different academic fields. In the present chapter a practical implementation of the approach is showed and discussed, using as a case study the 2015 Oasis Unit within two contexts—(1) as a holistic framework for addressing sustainability problems, and (2) as a design approach for educational field exercises. Finally, the authors summarize the usefulness of the integral approach in designing field exercises based on the seven year long experience of the University of Tokyo in organizing the Oasis Unit.