Ahmad Farid Abu Bakar

Arsenic, Zinc, and Aluminium Removal from Gold Mine Wastewater Effluents and Accumulation by Submerged Aquatic Plants (Cabomba piauhyensis, Egeria densa, and Hydrilla verticillata)

The potential of three submerged aquatic plant species (Cabomba piauhyensis, Egeria densa, and Hydrilla verticillata) to be used for As, Al, and Zn phytoremediation was tested. The plants were exposed for 14 days under hydroponic conditions to mine waste water effluents in order to assess the suitability of the aquatic plants to remediate elevated multi-metals concentrations in mine waste water. The results show that the E. densa and H. verticillata are able to accumulate high amount of arsenic (95.2%) and zinc (93.7%) and resulted in a decrease of arsenic and zinc in the ambient water. On the other hand, C. piauhyensis shows remarkable aluminium accumulation in plant biomass (83.8%) compared to the other tested plants. The ability of these plants to accumulate the studied metals and survive throughout the experiment demonstrates the potential of these plants to remediate metal enriched water especially for mine drainage effluent. Among the three tested aquatic plants, H. verticillata was found to be the most applicable (84.5%) and suitable plant species to phytoremediate elevated metals and metalloid in mine related waste water.

Cumulative impacts of dissolved ionic metals on the chemical characteristics of river water affected by alkaline mine drainage from the Kuala Lipis gold mine, Pahang, Malaysia

This paper describes the variations in levels of dissolved metals with spatial and hydrological conditions along the Kermoi River, which drains a gold mining area. The spatial analysis of data on metal levels in the river indicates that the levels of almost all types of studied ionic species tend to increase when moving from an upstream location towards the mining area; significant enrichments of 91%, 55%, 8% and 75% in As, Mn, Zn and levels, respectively, were observed, indicating that the mining area is a source of these metals. From the mining area towards a downstream location, metal levels tended to decrease, suggesting that a natural attenuation process occurred for all metals except As. We also found that different hydrological conditions clearly impacted the level of metals in and the water quality of the river. Correlation analyses revealed that different types of metals were associated with different flow conditions. We recommend that remediation strategies such as the construction of wetlands and the installation of phytoremediation technology at mining sites be considered.

Chemical speciation and bioavailability of rare earth elements (REEs) in the ecosystem: a review

Rare earths (RE), chemically uniform group of elements due to similar physicochemical behavior, are termed as lanthanides. Natural occurrence depends on the geological circumstances and has been of long interest for geologist as tools for further scientific research into the region of ores, rocks, and oceanic water. The review paper mainly focuses to provide scientific literature about rare earth elements (REEs) with potential environmental and health effects in understanding the research. This is the initial review of RE speciation and bioavailability with current initiative toward development needs and research perceptive. In this paper, we have also discussed mineralogy, extraction, geochemistry, analytical methods of rare earth elements. In this study, REEs with their transformation and vertical distribution in different environments such as fresh and seawater, sediments, soil, weathering, transport, and solubility have been reported with most recent literature along key methods of findings. Speciation and bioavailability have been discussed in detail with special emphasis on soil, plant, and aquatic ecosystems and their impacts on the environment. This review shows that REE gained more importance in last few years due to their detrimental effects on living organisms, so their speciation, bioavailability, and composition are much more important to evaluate their health risks and are discussed thoroughly as well.

Reviews of the toxicity behavior of five potential engineered nanomaterials (ENMs) into the aquatic ecosystem

Presently, engineered nanomaterials (ENMs) are used in a wide variety of commercial applications, resulting in an uncontrolled introduction into the aquatic environment. The purpose of this review is to summarize the pathways and factors that controlling the transport and toxicity of five extensively used ENMs. These toxicological pathways are of great importance and need to be addressed for sustainable implications of ENMs without environmental liabilities. Here we discuss five potentially utilized ENMs with their possible toxicological risk factors to aquatic plants, vertebrates model and microbes. Moreover, the key effect of ENMs surface transformations by significant reaction with environmental objects such as dissolved natural organic matter (DOM) and the effect of ENMs surface coating and surface charge will also be debated. The transformations of ENMs are subsequently facing a major ecological transition that is expected to create a substantial toxicological effect towards the ecosystem. These transformations largely involve chemical and physical processes, which depend on the properties of both ENMs and the receiving medium. In this review article, the critical issues that controlling the transport and toxicity of ENMs are reviewed by exploiting the latest reports and future directions and targets are keenly discussed to minimize the pessimistic effects of ENMs.

Toxicity evaluation of ZnO and TiO2 nanomaterials in hydroponic red bean (Vigna angularis) plant: Physiology, biochemistry and kinetic transport

The toxicity and kinetic uptake potential of zinc oxide (ZnO) and titanium dioxide (TiO2) nanomaterials into the red bean (Vigna angularis) plant were investigated. The results obtained revealed that ZnO, due to its high dissolution and strong binding capacity, readily accumulated in the root tissues and significantly inhibited the physiological activity of the plant. However, TiO2 had a positive effect on plant physiology, resulting in promoted growth. The results of biochemical experiments implied that ZnO, through the generation of oxidative stress, significantly reduced the chlorophyll content, carotenoids and activity of stress-controlling enzymes. On the contrary, no negative biochemical impact was observed in plants treated with TiO2. For the kinetic uptake and transport study, we designed two exposure systems in which ZnO and TiO2 were exposed to red bean seedlings individually or in a mixture approach. The results showed that in single metal oxide treatments, the uptake and transport increased with increasing exposure period from one week to three weeks. However, in the metal oxide co-exposure treatment, due to complexation and competition among the particles, the uptake and transport were remarkably decreased. This suggested that the kinetic transport pattern of the metal oxide mixtures varied compared to those of its individual constituents.

Assessment of heavy metal pollution in surficial sediments from a tropical river-estuary-shelf system: A case study of Kelantan River, Malaysia

To understand the source-to-sink of pollutants in the Kelantan River estuary and the adjacent shelf area in Malaysia, a total of 42 surface sediment samples were collected in the Kelantan River-estuary-shelf system to analyze for grain size, total organic carbon (TOC) content, Al and heavy metals (Cr, Ni, Cu, Zn, Cd and Pb). The surficial sediments were mainly composed of clayey silt and the TOC content in sediments decreased from the river to the shelf. The surficial sediments experienced Pb pollution; Cr only showed a certain level of pollution in the coastal area of the estuary but not in other areas, and Ni, Cu, Zn, and Cd showed no pollution. The heavy metals mainly originated from natural weathering and erosion of rocks and soils in the catchment and enriched near the river mouth. Total organic carbon can promote the enrichment of heavy metals in sediments.

Ionic release behavior of polymer-coated and uncoated metal nanoparticles (MNPs) in various conditions: effects of particle shape, size, and natural media reactivity

Metal nanoparticles (MNPs), due to its increasingly wide applications in consumer products, raises its concern towards ecotoxicology. Once released into the environment, the zero-valent metal (M°) readily oxidized to ionic metal (M+) which is reported as the main source of toxicity related to MNPs. The current study investigated the oxidative dissolution and M+ release profiles, from polymer-coated and uncoated MNPs. The polyethylene imine coated silver nanoparticles (PEI@AgNPs), polyethylene glycol coated zinc oxide micro-rods (PEG@ZnOMRs), and uncoated titanium dioxide nanoparticles (TiO2NPs) were synthesized with different size, shape, and surface functionalities, and M+ flow behavior was investigated through column transport experiment. The results obtained revealed that the ionic dissolution and M+ loss was 1.6–3.3% for PEI@AgNPs, 8.3–12.6% for TiO2NPs, and 13.6–19.0% for PEG@ZnOMRs. These results suggested that PEI surface coating greatly inhibit the M+ release and maximum column retention occurs in order of PEI@AgNPs ˃ TiO2NPs ˃ PEG@ZnOMRs.