Heavy metal pollution in water and soil is a serious concern to human health and the associated environment. Some heavy metals have bio-importance but the bio-toxic effects of many of them in human health are of great concern. Hence, there was a need for proper understanding of the concentration levels of these heavy metals in ground water and soil around the community residing in the vicinity of the defunct mine. Mining has become prominent in this area because of the existence of copper lodes, veins and veinlets. It was therefore necessary to assess these selected metals associated with copper mining as their concentration has a tendency to affect the environment and human health. The objective of this study was to establish the levels of lead (Pb)-zinc (Zn)-copper (Cu)-arsenic (As)-nickel (Ni) metals in ground water and soil associated with an old copper mine in the vicinity of the township and to compare them with the South African and international standards in order to safeguard the health of the community using such water for drinking purpose. Clean sampling plastic bottles were used to collect water from five water boreholes being used at present. Water samples were filtered using membrane filtration set LCW (0.45 μm). The samples were digested sequentially with different procedures for the total metal concentration. Concentrations of four metals commonly associated with Cu mining were examined at five different water boreholes which are used for drinking and industrial purposes. Flame Atomic Absorption Spectrophotometer (Perkin Elmar S/n 000003F6067A, Singapore) was used to analyze metals in water samples at Eskom Ga-Nala Laboratory: pH, electrical conductivity and turbidity were analyzed using an auto titrator meter (AT- 500,Japan), conductivity meter (Cole-parmer® YO-19601-00) and turbidity meter (AL 250TIR, Agua lytic, German) respectively. Soil samples were collected from the selected areas where human health is of a serious concern, and a hand held auger drill was used to recover samples, while shovels were used to prepare the sampling area. The samples were sieved up to 63.0 μm particle size and digested with aqua-regia. Flame Atomic Absorption Spectrophotometer (Model: AA400; Year: 2008; Manufacturer: Perkin Elmer; Germany; Serial no: 201S6101210) was used at the University of Venda Laboratory to analyze soil from the study area for possible heavy metal contamination due to the defunct Cu mine in the area. v The results showed variation of the investigated parameters in water samples as follows: pH, 6.0 to 7.51; EC, 70.0 to 96.40 μS/cm and turbidity, 1.05 to 4.56 NTU. The mean concentration of the metals increased in the followed order: Pb<Cu<As<Ni. Ni is the most abundant in the ground water determined with value of (6.49 μg/g). The observations have confirmed that most ground water contains an appreciable quantity of Ni. The mean value of As in water is (4.20 to 4.84 μg/g), Pb and Cu have (2.13 to 2.58 μg/g) and (1.52 to 2.52 μg/g) respectively. For soil samples, the mean concentration of the metals increased in the following order: Pb<Cu<Zn<As<Ni. Pb ranged from (0.023 to 0.036 μg/g) followed by Cu (0.28 to 0.45 μg/g) then Zn (0.026 to 0.053 μg/g), the mean range of As in soil ranged from (0.054 to 0.086 μg/g). However, some studies show much higher contamination of As from the natural sources and Ni with (0.057 to 0.144 μg/g) lastly. Accumulation of heavy metals in soil is of concern due to their toxic effects on human and animals. The quality of ground water from the five boreholes studied was satisfactory with turbidity (T), electrical conductivity (EC) and heavy metals (HM’s) below the WHO limit. The water therefore may, according to the WHO Standards be safely used as a drinking water. The concern lies on pH which was slightly (0.5) below the standard. There is a serious need to monitor the ground water which is now used for drinking purposes. This study revealed that heavy metal pollution in soil from the abandoned Cu mine in Musina is a threat to the health of the community. Although pollution was between medium and low in the contamination index, it is therefore important for the Musina Municipality or mine owner of Musina (TVL) Development Co Ltd copper mine to advocate possible remedial actions which will safeguard the environment and human health. The tailing at Musina’s old Cu mine have high pH and they lack normal soil stabilization processes, as a result the tailing does not develop a good plant cover. Pollution of the ground water resources is also evident in the study area where there is seepage or ingress of polluted water to the underground aquifers. Small-scale mining in Musina is causing further degradation to the environment but it supports the South African Waste Hierarchy by promoting the reuse and recycling of the tailing and mine dumps for the production of bricks. Mine workers are exposed to the above mentioned toxic heavy metals daily. Medicine will not help stop the poisoning. The only way to stop the metal poisoning is to stop being exposed to the heavy metals. / Environmental Sciences / M. Sc. (Environmental Management)

M. Tech. (Department of Chemical Engineering, Faculty of Engineering and Technology), Vaal University of Technology. / Heavy metal ions are one of the most toxic materials in the environment. Adsorption is the most used process for the removal of heavy metals from wastewater. Much research has been conducted into processes to remove heavy metals using different adsorbents. Various adsorbents have been used to remove heavy metal ions from wastewater especially those that are harmful to mankind. Zeolite, clay, activated carbon and biopolymers are the most common adsorbents used. In this research, gelatin, and cellulose nanocrystals (CNCs) were used to synthesize a hydrogel membrane to remove Cu(II) and Co(II) metal ions from mining processes wastewater. The synthetic wastewater was prepared in the laboratory to conduct the experiments. Batch experiments were conducted to obtain the optimum conditions for the Cu(II) and Co(II) metal ions. The effect of parameters such as pH, ratio, contact time, and temperature were also determined. The optimum conditions obtained were 120 min contact time for both metal ions at the temperature of 30oC, pH 5 for copper and pH 7 for cobalt. The high removal of both metals ions was obtained using the ratio 3:1 (75% Gelatin and 25% CNCs) at the temperature of 303K. The maximum adsorption capacity of Cu(II) and Co(II) was 7.6923 mg/g and 10.988 mg/g, respectively. The high percentage removal of Cu(II) and Co(II) metal ions obtained was found to be 70.5% for Cu(II) at pH 5 and 74.5% for Co(II) at pH 7. The experimental data fit well to Pseudo-first-order kinetic and Freundlich isotherm models (KF= 1.89x103 mg/g for copper and 3.7x102 mg/g for cobalt) for both metal ions. The values of energy (E) from D-R model have shown that the adsorption of both metal ions was of physical nature (E<8kJ/mol) then confirmed by the thermodynamic results (ΔH°). The kinetic diffusion models have shown that the experimental data fit well with the film diffusion (R2= 0.977 and 0.989) for both metal ions at pH 5. Negative values of ΔG°obtained for both metal ions indicate that the adsorption process was spontaneous. The positive values of ΔH° obtained showed a physical adsorption process and also indicate that the adsorption process of both metal ions was endothermic. The positive values of ΔS° indicate an increase in randomness at the solid/solution interface during adsorption.

The mining industry produces vast quantities of overburden and mill tailings. In many instances the disposal of these wastes on the Earth's surface have caused local, and occasionally even regional, water resources to become contaminated. Contamination typically arises from the oxidation of metal sulfide minerals contained within these wastes. Upon oxidation these minerals release sulfate, their associated metal cations and acidity into solution. This study investigated the potential for groundwater contamination arising from a Pb/Zn tailings impoundment in the North West Province of South Africa (Pering Mine). The tailings is composed predominantly of dolomite, which imparts to the material an alkaline pH and a high acid buffering capacity. Acid-base accounting (ABA) established that the capacity of the tailings to buffer acidity surpasses any acid producing potential that could arise from pyrite (FeS2), galena (PbS) and sphalerite (ZnS) oxidation. These minerals account for about 3 to 6% of the tailings by mass. Total elemental analysis (XRF) showed that the material has high total concentrations of Fe (19083 mg kg-I), Zn (5481 mg kg-I), Pb (398 mg kg-I), S (15400 mg kg-I), Al (9152 mg kg-I) and Mn (29102 mg kg-I). Only a very small fraction of this, however, was soluble under saturated conditions. An estimation of potentially available concentrations, using the DTPA extraction method, indicated that high concentrations of Zn (1056 mg kg-I), and moderate concentrations of Pb (27.3 mg kg-I) and Cu (6.01 mg kg-I) could potentially be available to cause contamination. A number of leaching experiments were undertaken to accurately quantify the release of elements from the tailings material. These experiments were aimed at determining the potential for groundwater contamination and also provided a means whereby the long-term release of contaminants could be modelled using the convection-dispersion equation for solute transport. Four leaching treatments were investigated. Two consisted of using distilled water under intermittent and continuous flow, while a third used intermittent flow of deoxygenated distilled water to assess leaching under conditions of reduced oxygen. The.mobilisation of potential contaminants under a worst case scenario was assessed by means of leaching with an acetic acid solution at pH 2.88 (after the US Environmental Protection Agency's toxicity characteristic leaching procedure). The acid buffering potential of the tailings was considerable. Even after 8 months of weekly leaching with 1 pore volume of acetic acid solution the pH of the effluent was maintained above pH 5.90. The protracted acidity caused very high concentrations of Pb, Zn, Mu, Ca, Mg, Hg and S to be released into solution. Leaching the tailings with distilled water also caused the effluent to have noticeable traces of contamination, most importantly from S, Mg, Mu and Zn. In many instances concentrations significantly exceeded guideline values for South African drinking water. Modelling solute transport with the convectiondispersion equation predicted that sol- and Mu contamination could persist for a very long period of time. (±700 years under continuous saturated leaching), while Mg and Zn concentrations would most likely exceed recommended limits for a much shorter period of time (±300 years under the same conditions). In light of the various column leaching experiments it was concluded that seepage from the Pering tailings impoundment could cause groundwater contamination. A drill-rig and coring system were used to collect both tailings and pore-water samples from eight boreholes spread out across the tailings impoundment. These investigations showed that most of the impoundment was aerobic (Eh ranged from +323 to +454 mY) and alkaline (pH 8.0 to 9.5). This chemical environment favours sulfide oxidation and as a consequence high concentrations of S have been released into the pore-water of the impoundment (S concentrations ranged from 211 to 1221 mg r l ). The acidity released as a by-product of sulfide oxidation was being buffered by dolomite dissolution, which in turn was releasing high concentrations of Mg (175 to 917 mg r l ) and Ca (62.6 to 247 mg r l ) into solution. Metal concentrations in the pore-water were low as a result of the strong metal sorbing capacity of the tailings and possible secondary precipitation. The only metal which significantly exceeded recommended limits throughout the impoundment was Hg (concentrations were between 100 and 6000 times the recommended limit of 0.001 mg r l ). Under the current geochemical conditions it is expected that Hg, S and Mg will likely pose the greatest threat to groundwater. The main concerns associated with mine tailings are that of mine drainage and dust blow off..In order to eradicate the latter problem, the tailings impoundment at Pering Mine was covered with a layer of rocks. Modelling the water balance of the impoundment using the computer model HYDRUS-2D showed that the rock cladding has potentially increased the volume of drainage water seeping from the impoundment. In light of the leaching experiments and field work, which proved that water passing through the tailings became enriched with various potentially toxic elements, it is expected that the problem of groundwater contamination around Pering Mine has been further exacerbated by the rock cladding. It was therefore concluded that there would be a strong likelihood of groundwater contamination in the vicinity of the mine. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2006.

The original aims of this project were to investigate the potential for phytoremediation, with emphasis on metal accumulation, of three contrasting industrial processing wastes. These were tailings material (PT) from the decommissioned Pering Pb/Zn Mine (Reivilo, North West Province, South Africa (SA)), smelter slag (SS) from the Samancor Mnsmelter (Meyerton, Gauteng, SA) and electro-winning waste (EW) from MMC (Nelspruit, Mpumalanga, SA). It became evident, however, early in the project, that the use of metal hyperaccumulating plants was not a viable technology for these wastes. The project objectives were thus adapted to investigate alternative remedial technologies. The use of endemic and adapted grass species was investigated to revegetate the PT. In addition, chemically-enhanced phytoremediation was investigated to induce metal hyperaccumulation by grasses grown in the PT (Part 1). Revegetation of the SS and EW were not considered feasible, thus land disposal of these two Mn-rich processing wastes was investigated (Part 2). Part 1 - Revegetation of tailings from Pering Mine The PT was found to be alkaline (pH > 8.0), and consisted mainly of finely crushed dolomite. It was generally nutrient poor with high amounts of readily extractable Zn. It also had a very high P-sorption capacity. Seven grass species (Andropogon eucomus Nees; Cenchrus ciliaris L.; Cymbopogon plurinodis Stapf ex Burtt Davy; Digitaria eriantha Steud; Eragrostis superba Peyr; Eragrostis tef (Zucc.) Trotter and Fingeruthia africana Lehm) were grown in PT treated with different rates of inorganic fertiliser under glasshouse conditions. The fertiliser was applied at rates equivalent to 100 kg N, 150 kg P and 100 kg K ha-1 (full), half the full rate (half) and no fertiliser (0). Seed of C. ciliaris, C. plurinodis, D. eriantha, E. superba and F. africana were collected from Pering Mine. Seed of A. eucomus was collected from the tailings dam of an abandoned chrysotile asbestos mine. These were germinated in seedling trays and replanted into the pots. A commercial variety of E. tef was tested, but due to poor survival this species was subsequently excluded. The foliage and root biomass of the grasses and concentrations of Ca, Cu, Fe, K, Mg, Mn, Pb and Zn in the foliage were determined. The yield of all the grasses increased with an increase in fertiliser rate, with a significant species by fertiliser interaction (p = 0.002). The highest yield was measured for C ciliaris, followed by D. eriantha (4.02 and 3.43 g porI, respectively), at the full fertiliser application rate. Cymbopogon plurinodis was the third highest yielding species, while the yields of E. superba and F. africana were similar. There were positive linear correlations between foliage yield and fertiliser application rate for all grasses. The root biomass of the grasses also increased with an increase in fertiliser application rate. The interaction between grass species and fertiliser level had a non-significant (p = 0.085) effect on the yield of grasses, though there were significant individual effects of species (p < 0.001) and fertiliser (p < 0.001). Digitaria eriantha had the highest root biomass at each fertiliser application rate, followed by C plurinodis and C ciliaris. Similarly to foliage yield, there were positive linear correlations between root biomass and fertiliser application level. Positive, linear correlations were found between foliage yield and root biomass, though the strength of these varied. The weakest correlation was found for D. eriantha (R2 = 0.42) but this was attributed to a moderately high variance in foliage yield and roots becoming potbound. Generally, nutrient concentrations were within adequacy ranges reported in the literature, except for P concentrations. This was attributed to the high P-sorption capacity of the PT. Zinc concentrations were higher than the recommended range for grasses, and also increased with an increase in fertiliser application rate. This was attributed to the high available Zn concentrations in the PT and improved growth of the grasses at higher fertiliser application rates. It was recommended that C ciliaris and D. eriantha be used for revegetation due to high biomass production and that E. superba be used because of rapid growth rate and high self-propagation potential. Both C plurinodis and F. africana can also be used but are slower to establish, while A. eucomus was not a suitable species for revegetation of the PT. Inorganic fertiliser improved the growth of all these species and is recommended for the initial establishment of the grasses. An experiment was conducted to investigate the potential of inducing metal hyperaccumulation in three grass species (C ciliaris, D. eriantha and E. superba) grown in the PT. Grasses were grown in fertilised tailings for six weeks, then either ethylenediaminetetraacetic acid (EDTA) or diethylentriaminepentaacetic acid (DTPA) was added to the pots at rates of 0, 0.25, 0.5, 1 and 2 g kg-I. Grasses were allowed to grow for an additional week before harvesting. The concentrations of Cu, Pb and Zn were determined in the foliage. The interactive effect of species and chelating agent on the uptake of Cu was marginally significant (p = 0.042) and non-significant for Pb and Zn (p = 0.14 and 0.73, respectively). While the addition of the chelating agents resulted in an increase in Pb uptake by the grasses, it did not induce metal hyperaccumulation in the grasses. This was attributed to the ineffectiveness of the chelating agents in the PT in the presence of competing base cations (mainly Ca). The use of this technology was not recommended. Part 2 - Land disposal of Mn-rich processing wastes Chemical characterisation of the SS showed that it was an alkaline (pH > 9.5), Mn-rich silicate (glaucochroite), that generally·had low amounts of soluble and readily extractable metals. Acidic extractants removed high amounts of Mn, Ca and Mg, attributed to the dissolution of the silicate mineral. The EW was highly saline (saturated paste EC = 6 780 mS m,l) with a near-neutral pH. It had high amounts of soluble Mu, NHt+, S, Mg, Ca and Co. The primary minerals were magnetite, jacobsite (MnFe204) and gypsum. The effect of SS and EW on selected chemical properties of six soils was investigated by means of an incubation experiment, and their effect on the yield and element uptake by ryegrass was investigated in selected soils under glasshouse conditions. Five A-horizons (Bonheim (Ba), Hutton (Hu), lnanda (la), Shortlands (Sd) and Valsrivier (Va» and an Ehorizon (Longlands (Lo» were treated with SS at rates of 30, 60, 120,240 and 480 g kg'l and EW at rates of20, 40,80,160 and 320 g kg'l. Soils were incubated at field capacity at 24 QC and sampled periodically over 252 days. The soil pH, both immediately and over time, increased, while exchangeable acidity decreased after the addition of SS to the soils. The pH at the high rates of SS tended to be very high (about 8). The electrical conductivity (EC) of the soils also increased with an increase in SS application rates and over time. The most marked changes tended to occur in the more acidic soils (e.g. la). In the soils treated with EW, there was generally an increase in the pH of the acid soils (e.g. la) while in the more alkaline soils the pH tended to decrease (e.g. Va), immediately after waste application. There was a general decrease in pH over time, with a concurrent increase in exchangeable acidity, due to nitrification processes. The EC of all the soils increased sharply with an increase in EW application rate, attributed to the very saline nature of the EW. Water-soluble Mn concentrations in the soils treated with SS tended to be below measurable limits, except in the acid la. Iron concentrations decreased with an increase in SS application rate and over time for all soils. The water-soluble concentrations of Mn, Ca, Mg and S increased sharply with an increase in EW application rate in all soils. There was also a general increase in Mn concentrations over time. Iron concentrations tended to be low in the EW-treated soils, while Co concentrations increased as EW application rate increased. Exchangeable (EX, 0.05 M CaCh-extractable) concentrations of Fe, Co, Cu, Zn and Ni were low in the SS-treated soils. The concentrations of EX-Mn tended to increase with an increase in SS application rate in the la soil, but generally decreased in the other soils. There was also a decrease over time, attributed to the high pH leading to immobilisation of Mn. The EX-metal concentrations of the EW-treated soils were generally low, except for Mn. The concentrations of EX-Mn increased sharply as EW application rate increased. The contribution of EX-Mn was calculated to range from 209 to 3 340 mg Mn for EW rates of 20 to 320 g kg-I, respectively. In the Lo soil the expected amount of Mn was extracted at the different EW application rates. In the other soils the EX-Mn concentrations were typically higher than expected. This was attributed primarily to the dissolution ofMn from the EW due to the interaction between soil organic matter and the EW. There was generally an increase in EX-Mn concentrations over time, attributed to the decrease in pH of the soils treated with EW. The above-ground biomass production of ryegrass grown in Lo and Hu soils treated with SS increased at low application rates, but decreased again at the highest rates. The reduction in yield was attributed to an increase in soil pH leading to trace nutrient deficiencies. At the lower SS application rates, nutrient concentrations of the ryegrass tended to be within typical adequate ranges reported in the literature. Of concern was the elevated Mn concentration in the ryegrass foliage, though no toxicity symptoms were seen. This was attributed to the dissolution of the silicate mineral due to soil acidification processes and the possible ameliorating effect of high Ca and Si concentrations on Mn toxicity. The growth of ryegrass was generally poor in the Hu soil treated with EW and it did not survive beyond germination in the Lo soil treated with EW. In the Hu soil plants grew well in the 20 and 40 g kg-I EW treatments, but died at the higher rates. In both cases mortality was thought to be due to the high salinity that resulted in toxicity and osmotic stress in the newly germinated seedlings. The improved growth at the lower rates ofEW, in the Hu soil, was attributed mainly to increased N availability. The concentrations of Mn in the foliage were elevated in the soils treated with EW. A pot experiment was conducted to test the effect of applying either humic acid (HA) or compost (at a rate of 20 g kg-I) with lime (at rates of 0, 5 and 10 Mg ha-I) on the growth and nutrient uptake of ryegrass grown in the Hu soil treated with EW at rates of 0, 10, 20 and 40 g kg-I. A basal P-fertiliser was also applied in this experiment. The highest yields were measured in the treatments receiving either HA or compost at the highest application rate ofEW. The addition oflime did not improve the yield of the HA treatments, but did in the compost treatments. Generally, nutrient concentrations were adequate. The Mn concentrations were markedly lower than expected, and this was attributed to the formation of insoluble Mn-P compounds due to the addition of fertiliser. The effect of either HA or compost on Mn concentrations was not marked, but lime reduced Mn uptake. A leaching column experiment showed that, generally, the Mn was not readily leached through a simulated soil profile, though the addition of compost may enhance mobility. There was also evidence to indicate an increase in salinity and that Co concentrations of the leachate may be a problem. These data suggest that soil organic matter may be a very important factor in determining the release of Mn from the wastes, notably the EW. The land disposal of the SS and EW was not recommended at the rates investigated here, as both showed the potential for Mn accumulation in above-ground foliage, even at low application rates, while high application rates negatively impacted on plant growth. It appears that P-compounds may be beneficial in reducing Mn availability in the EW, but further testing is required. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2007.

Pollution of soil by trace metals has become one of the biggest global environmental challenges resulting from anthropogenic activities, therefore, restoration of metal contaminated sites needs due attention. The use of phytoremediation technologies as nature-based solution to pollution, could support successful implementation of green economic development strategies; with economically affordable and environmentally friendly benefits. The present investigation employed an exploratory study on the phytoremediation potentials of three selected native plants; Phytolacca dodecandra (L’Herit), Adhatoda schimperiana (Hochst) and Solanum incanum L, dominating areas close to heavy metal contamination sources; in metropolitan centers of Addis Ababa. In this work, concentration of six heavy metals of interest chromium (Cr), lead (Pb), cadmium (Cd), nickel (Ni) copper (Cu) and zinc (Zn) were examined in soil and in different tissues (leaves, stems and roots) of selected plants (both seedlings and mature plants), in dry and rainy seasons using atomic absorption spectrophotometer. Efficiency of phytoremediation is discussed based on calculated values of Bio-concentration Factor (BCF), Translocation Factors (TF) and Bioaccumulation Coefficient (BAC). Phytolacca dodecandra showed BCF, TF and BAC > 1 for Zn, Pb, Ni, Cu and Cd Adhatoda schimperiana gave BCF, TF and BAC > 1 for Zn, Cu, Ni and Cr; likewise, BCF, BAC and TF values of > 1 were noted in Solanum incanum for Zn, Cu, Pb and Ni. Based on these scenarios, the three plants could be utilized for phytoextraction of contaminated soil. Conversely, BCF and BAC for Cr levels in tissues of Phytolacca dodecandra were all < 1, which indicates unsuitability for phytoremediation of Cr in contaminated soils. Besides, Adhatoda schimperiana retained Pb and Cd in their roots showing root BCF > 1, while BAC and TF < 1, which highlights its suitability for phytostabilization. Moreover, BCF, TF and BAC values of < 1 noted for Cr and Cd in Solanum incanum reveal that Solanum incanum may not be a good candidate for remediation of Cr and Cd contaminated environments. In conclusion, results from this study revealed that the selected plants can accumulate substantial amounts of the above trace metals in their tissues and can serve as prospective phytoremediators of most of these metals. Phytoextraction and phytostabilization were the main mechanisms of remediation in this study. / Environmental Sciences / Ph. D. (Environmental Sciences)

Indiana University-Purdue University Indianapolis (IUPUI) / The etiology of many neurodegenerative diseases is unknown, but a number of studies indicate that a combination of both genetic and environmental factors contribute to the progression of disease. Exposure to environmental metals, such as Mn2+, Fe2+, Cu2+, and Al3+, has been shown to increase cell death that is characteristic of neurodegenerative disorders such as AD, PD, Wilson’s disease and Menkes disease. These metals are important in numerous biological processes in the brain and their homeostasis is regulated through multiple mechanisms of transport, storage, and secretion. The vertebrate divalent metal transporter-1 (DMT-1) has been implicated in transport and homeostasis of these divalent cations. In these studies I utilize Caenorhabditis elegans (C. elegans) to show that long term exposure to Mn2+ decreases animal viability in a dose-dependent manner, and I demonstrate that C. elegans homologues to DMT-1, SMF-1, SMF-2, and SMF-3, play specific roles in divalent metal ion-induced DA neurodegeneration. I show that SMF-1 contributes to Fe2+-induced DA neuron degeneration, SMF-3 contributes to Al3+-induced DA neuron degeneration, and both SMF-2 and DAT-1 contribute to Cu2+-induced DA neuron cell death. These studies utilize C. elegans as a powerful model to characterize molecules and pathways involved in metal toxicity and metal-induced DA neuron degeneration.