Publications by authors named "Heileen Hsu-Kim"

Article Synopsis
  • The study demonstrates that biomolecular condensates, not just ion channels, can influence the electrochemical environment in bacterial cells.
  • Condensate formation creates an electric potential gradient that alters key cellular properties like pH and membrane potential, leading to variability in electrochemical properties among cells.
  • This modulation impacts how cells interact with their environment and affects bacterial survival under antibiotic stress by shifting gene expression profiles.
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Acid mine drainage (AMD) from inactive coal mines can be enriched in rare earth elements (REEs) and has gained much attention as an alternative source for these technology-critical metals. However, AMD is a relatively low-grade REE resource in which the abundance of impurities and the composition variability of the feedstock create major uncertainties for the performance of REE extraction technologies. This study sought to identify AMD feedstock variables that influence the extraction efficiency of REEs by supported liquid membranes (SLMs).

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Mercury (Hg)-impaired aquatic ecosystems often receive multiple inputs of different Hg species with varying potentials for transformation and bioaccumulation. Over time, these distinct input pools of Hg homogenize in their relative distributions and bioaccumulation potentials as a result of biogeochemical processes and other aging processes within the ecosystem. This study sought to evaluate the relative time scale for homogenization of multiple Hg inputs to wetlands, information that is relevant for ecosystem management strategies that consider Hg source apportionment.

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Control of the electrochemical environment in living cells is typically attributed to ion channels. Here we show that the formation of biomolecular condensates can modulate the electrochemical environment in cells, which affects processes globally within the cell and interactions of the cell with its environment. Condensate formation results in the depletion or enrichment of certain ions, generating intracellular ion gradients.

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Background: Few birth cohorts in South America evaluate the joint effect of minerals and toxic metals on neonatal health. In Madre de Dios, Peru, mercury exposure is prevalent owing to artisanal gold mining, yet its effect on neonatal health is unknown.

Objectives: We aimed to determine whether toxic metals are associated with lower birth weight and shorter gestational age independently of antenatal care and other maternal well-being factors.

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Liquid elemental mercury (Hg) pollution can remain in soils for decades and, over time, will undergo corrosion, a process in which the droplet surface oxidizes soil constituents to form more reactive phases, such as mercury oxide (HgO). While these reactive coatings may enhance Hg migration in the subsurface, little is known about the transformation potential of corroded Hg in the presence of reduced inorganic sulfur species to form sparingly soluble HgS particles, a process that enables the long-term sequestration of mercury in soils and generally reduces its mobility and bioavailability. In this study, we investigated the dissolution of corroded Hg in the presence of sulfide by quantifying rates of aqueous Hg release from corroded Hg droplets under different sulfide concentrations (expressed as the S:Hg molar ratio).

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Lead (Pb) is an important developmental toxicant. The mitochondrial calcium uniporter (MCU) imports calcium ions using the mitochondrial membrane potential (MMP), and also appears to mediate the influx of Pb into the mitochondria. Since our environment contains mixtures of toxic agents, it is important to consider multi-chemical exposures.

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Coal combustion byproducts are known to be enriched in arsenic (As) and selenium (Se). This enrichment is a concern during the handling, disposal, and reuse of the ash as both elements can be harmful to wildlife and humans if mobilized into water and soils. The leaching potential and bioaccessibility of As and Se in coal fly ash depends on the chemical forms of these elements and their association with the large variety of particles that comprise coal fly ash.

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At mercury (Hg)-contaminated sites, streambank erosion can act as a main mobilizer of Hg into nearby waterbodies. Once deposited into the waters, mercury from these soils can be transformed to MeHg by microorganisms. It is therefore important to understand the solid-phase speciation of Hg in streambanks as differences in Hg speciation will have implications for Hg transport and bioavailability.

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Background: Studies have shown elevated blood lead levels (BLL) in residents of remote communities in the Amazon, yet sources of lead exposure are not fully understood, such as lead ammunition consumed in wild game.

Methods: Data was collected during two cross-sectional studies that enrolled 307 individuals in 26 communities. Regression models with community random effects were used to evaluate risk factors for BLLs, including diet, water source, smoking, sex, age, and indigenous status.

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Mercury emissions from artisanal and small-scale gold mining throughout the Global South exceed coal combustion as the largest global source of mercury. We examined mercury deposition and storage in an area of the Peruvian Amazon heavily impacted by artisanal gold mining. Intact forests in the Peruvian Amazon near gold mining receive extremely high inputs of mercury and experience elevated total mercury and methylmercury in the atmosphere, canopy foliage, and soils.

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Mercury is a risk in aquatic ecosystems when the metal is converted to methylmercury (MeHg) and subsequently bioaccumulates in aquatic food webs. This risk can be difficult to manage because of the complexity of biogeochemical processes for mercury and the need for accessible techniques to navigate this complexity. Here, we explored the use of diffusive gradient in thin-film (DGT) passive samplers as a tool to simultaneously quantify the methylation potential of inorganic Hg (IHg) and the bioaccumulation potential of MeHg in freshwater wetlands.

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Silver nanoparticles (AgNPs) are extensively used in consumer products and biomedical applications, thus guaranteeing both environmental and human exposures. Despite extensive research addressing AgNP safety, there are still major knowledge gaps regarding AgNP toxicity mechanisms, particularly in whole organisms. Mitochondrial dysfunction is frequently described as an important cytotoxicity mechanism for AgNPs; however, it is still unclear if mitochondria are the direct targets of AgNPs.

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Total mercury content (THg) in hair is an accepted biomarker for chronic dietary methylmercury (MeHg) exposure. In artisanal and small-scale gold mining (ASGM) communities, the validity of this biomarker is questioned because of the potential for contamination from inorganic mercury. As mining communities may have both inorganic and organic mercury exposures, the efficacy of the hair-THg biomarker needs to be evaluated, particularly as nations begin population exposure assessments under their commitments to the Minamata Convention.

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Silver nanoparticles (AgNPs) are well-proven antimicrobial nanomaterials, yet little is elucidated regarding the mechanism underlying cytotoxicity induced by these nanoparticles. Here, we tested the hypothesis that mitochondria are primary intracellular targets of two AgNPs and silver ions in mouse hepatocytes (AML12) cultured in glucose- and galactose-based media. AML12 cells were more sensitive to mitochondrial uncoupling when grown with galactose rather than glucose.

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Background: In-utero exposure to mercury and other trace metals pose a significant threat to child health and development, but exposures and health impacts in artisanal and small-scale gold mining (ASGM) environments are poorly defined.

Objectives: We describe the CONAMAD study design, a prospective birth cohort consisting of multiparous women (18 and over) living in rural and peri-urban Peruvian Amazon communities exposed to ASGM.

Methods: Pregnant women are enrolled from health posts across four zones of Madre de Dios, Peru.

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All cells produce extracellular vesicles (EVs). These biological packages contain complex mixtures of molecular cargo and have a variety of functions, including interkingdom communication. Recent discoveries highlight the roles microbial EVs may play in the environment with respect to interactions with plants as well as nutrient cycling.

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Scandium (Sc) has great potential for use in aerospace and clean energy applications, but its supply is currently limited by a lack of commercially viable deposits and the environmental burden of its production. In this work, a biosorption-based flow-through process was developed for extraction of Sc from low-grade feedstocks. A microbe-encapsulated silica gel (MESG) biosorbent was synthesized through sol-gel encapsulation of , a bacterium that selectively adsorbs Sc.

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Background: In Peru, anemia has been a persistent health problem that is known to lead to irreversible cognitive and developmental deficits in children. The Peruvian government has recently made anemia a primary health concern by passing legislation in 2017 that makes anemia an intersectoral priority. This new legislation fortifies previous programs while creating new programs that target specific age groups.

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Micelle enhanced ultrafiltration (MEUF) is a surfactant-based membrane separation process that may be used to separate target ions from mixed metal aqueous solutions, such as leachates of coal ash and other geological wastewaters. The ability of MEUF to separate rare earth elements (REEs) was evaluated using sodium dodecyl sulfate (SDS) as the sorbent in surfactant micelle phase, which was subsequently separated using ultrafiltration, acidification, and ferricyanide precipitation. Separation experiments were performed with a synthetic coal ash leachate feedstock as an example mixed-metal feedstock.

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Children living near artisanal and small-scale gold mining (ASGM) are at risk of exposure to mercury, a neurotoxicant. It is not certain whether such exposures are harming development, as they occur in underresourced contexts entwined with other stressors, such as malnutrition and enteric infection. This study sought to investigate the association between hair-mercury levels and visual-motor, cognitive, and physical development among children living near ASGM in the Peruvian Amazon.

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Human exposure to mercury is a leading public health problem. Artisanal and small-scale gold mining (ASGM) is a major source of global mercury emissions. Although occupational mercury exposure to miners (via mercury vapor inhalation) is known, chronic mercury exposure to nearby residents that are not miners (via mercury-contaminated fish consumption) is poorly characterized.

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Multiple mechanisms for plastic consumption by marine animals have been proposed based on the feeding cues and behavior of the animal studied. We investigated plastic consumption in sea anemones. We found that anemones readily consumed pristine National Institute of Standards and Technology low-density polyethylene and high-density polyethylene II and III pre-production pellets.

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Reliable predictions of the environmental fate and risk of engineered nanomaterials (ENMs) require a better understanding of ENM reactivity in complex, biologically active systems for chronic low-concentration exposure scenarios. Here, simulated freshwater wetland mesocosms were dosed with ENMs to assess how their reactivity and seasonal changes in environmental parameters influence ENM fate in aquatic systems. Copper-based ENMs (Kocide), known to dissolve in water, and gold nanoparticles (AuNPs), stable against dissolution in the absence of specific ligands, were added weekly to mesocosm waters for 9 months.

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Artisanal and small-scale gold mining (ASGM) is a significant contributor of mercury (Hg) contamination and deforestation across the globe. In the Colorado River watershed in Madre de Dios, Peru, mining and deforestation have increased exponentially since the 1980s, resulting in major socioeconomic shifts in the region and two national state of emergency (2016 and 2019) in response to concerns for wide-scale mercury poisoning by these activities. This research employed a watershed-scale soil particle detachment model and environmental field sampling to estimate the role of land cover change and soil erosion on river transport of Hg in a heavily ASGM-impacted watershed.

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