Alandra Lopez

All Publications

• Geothermal Arsenic Threats to Intensive Groundwater Utilization in an Arid Basin. Environmental science & technology Honeyman, A. S., Blythe, C., Lopez, A., Vajedian, S., Carney, D., Harmon, E., James, K. A., Gribble, M., Smith, R., Fendorf, S. 2025

  Abstract

  Groundwater quality is critical for safe drinking water and irrigation supplies but can be threatened by geogenic toxins that are difficult to predict. In the arid, high desert San Luis Valley (SLV), Colorado, a groundwater basin serves as the primary water supply with observed arsenic concentrations exceeding the maximum contaminant level (MCL) of 10 μg/L set by the U.S. EPA. However, the sources and processes responsible for As occurrence are unclear. Through a community-engaged sampling effort, we collected 244 groundwater samples and measured major/trace element concentrations. Long-term land subsidence and depth-resolved sediment texture were computed at the same locations. We tested three plausible geochemical processes responsible for As release: (1) overpumping-induced dewatering of As-bearing clays (proxied by land subsidence), (2) pH-promoted desorption as well as reductive dissolution of As(V)/Fe(III) (hydr)oxides, and (3) incursion of higher-As geothermal fluids (proxied by lithium, boron, tungsten, and molybdenum) into groundwater. We find that statistics, statistical/machine learning, and aqueous thermodynamics all agree that geothermal fluid mixing within the aquifer is the main source of dissolved As. Our findings suggest that overpumping draws higher-As thermal fluid from the bottom of the aquifer to pumping depth, leading to increased concentrations of As in drinking/irrigation water supplies at wells.

  View details for DOI 10.1021/acs.est.4c12125

  View details for PubMedID 39960293

• The Influence of Wildfire Smoke on Ambient PM2.5 Chemical Species Concentrations in the Contiguous US. Environmental science & technology Krasovich Southworth, E., Qiu, M., Gould, C. F., Kawano, A., Wen, J., Heft-Neal, S., Kilpatrick Voss, K., Lopez, A., Fendorf, S., Burney, J. A., Burke, M. 2025

  Abstract

  Wildfires significantly contribute to ambient air pollution, yet our understanding of how wildfire smoke influences specific chemicals and their resulting concentration in smoke remains incomplete. We combine 15 years of daily species-specific PM2.5 concentrations from 700 air pollution monitors with satellite-derived ambient wildfire smoke PM2.5, and use a panel regression to estimate wildfire smoke's contribution to the concentrations of 27 different chemical species in PM2.5. Wildfire smoke drives detectable increases in the concentration of 25 out of the 27 species with the largest increases observed for organic carbon, elemental carbon, and potassium. We find that smoke originating from wildfires that burned structures had higher concentrations of copper, lead, zinc, and nickel relative to smoke from fires that did not burn structures. Wildfire smoke is responsible for an increasing share of ambient concentrations of multiple species, some of which are particularly harmful to health. Using a risk assessment approach, we find that wildfire-induced enhancement of carcinogenic species concentrations could cause increases in population cancer risk, but these increases are very small relative to other environmental risks. We demonstrate how combining ground-monitored and satellite-derived data can be used to measure wildfire smoke's influence on chemical concentrations and estimate population exposures at large scales.

  View details for DOI 10.1021/acs.est.4c09011

  View details for PubMedID 39899563

• Molecular insights and impacts of wildfire-induced soil chemical changes NATURE REVIEWS EARTH & ENVIRONMENT Lopez, A., Avila, C. E., Vanderroest, J. P., Roth, H. K., Fendorf, S., Borch, T. 2024

  View details for DOI 10.1038/s43017-024-00548-8

  View details for Web of Science ID 001222400000001

• Metal toxin threat in wildland fires determined by geology and fire severity. Nature communications Lopez, A. M., Pacheco, J. L., Fendorf, S. 2023; 14 (1): 8007

  Abstract

  Accentuated by climate change, catastrophic wildfires are a growing, distributed global public health risk from inhalation of smoke and dust. Underrecognized, however, are the health threats arising from fire-altered toxic metals natural to soils and plants. Here, we demonstrate that high temperatures during California wildfires catalyzed widespread transformation of chromium to its carcinogenic form in soil and ash, as hexavalent chromium, particularly in areas with metal-rich geologies (e.g., serpentinite). In wildfire ash, we observed dangerous levels (327-13,100 µg kg-1) of reactive hexavalent chromium in wind-dispersible particulates. Relatively dry post-fire weather contributed to the persistence of elevated hexavalent chromium in surficial soil layers for up to ten months post-fire. The geographic distribution of metal-rich soils and fire incidents illustrate the broad global threat of wildfire smoke- and dust-born metals to populations. Our findings provide new insights into why wildfire smoke exposure appears to be more hazardous to humans than pollution from other sources.

  View details for DOI 10.1038/s41467-023-43101-9

  View details for PubMedID 38086795

  View details for PubMedCentralID 7812759

• Assessing Analytical Methods for the Rapid Detection of Lead Adulteration in the Global Spice Market. Environmental science & technology Lopez, A. M., Nicolini, C. M., Aeppli, M., Luby, S. P., Fendorf, S., Forsyth, J. E. 2022

  Abstract

  Lead adulteration of spices, primarily via Pb chromate compounds, has been documented globally as a growing public health concern. Currently, Pb detection in spices relies primarily on expensive and time-consuming laboratory analyses. Advancing rapid Pb detection methods, inclusive of their accuracy and precision, would improve field assessments by food safety inspectors, stakeholders, and the public in the hope of reducing Pb exposure risks at its source. Here, we present two field procedures for Pb detection: portable X-ray fluorescence analysis (pXRF) and a simple colorimetric test. We assess their efficacy to detect Pb and its chemical form in seven spice types, including powders, spice-salt mixtures, and dried roots, compared to the proven laboratory technique, inductively coupled plasma mass spectrometry (ICP-MS). Lead concentrations measured using pXRF and ICP-MS were within 5% of each other for spice powders and 24% for dried roots. By pXRF, spice samples were analyzed within collection plastic bags without preparation, resulting in a detection limit of 2 mg Pb/kg for spice powders, which is comparable to national food standards. The colorimetric test utilized here targets hexavalent chromium, making the method selective to Pb chromate adulteration assuming that this is its dominant source in spices. Color development, and thus detection, was observed when Pb concentrations exceeded approximately 5-70 mg/kg in dried turmeric roots and 1000 mg/kg in spice powders; however, it was ineffective for the spice-salt mixture. We show that pXRF analysis and a colorimetric assay provide information that may improve field decisions about Pb adulteration in a range of spice types, helping to minimize Pb exposure.

  View details for DOI 10.1021/acs.est.2c03241

  View details for PubMedID 36343212

• Perchlorate and Agriculture on Mars SOIL SYSTEMS Oze, C., Beisel, J., Dabsys, E., Dall, J., North, G., Scott, A., Lopez, A., Holmes, R., Fendorf, S. 2021; 5 (3)

  View details for DOI 10.3390/soilsystems5030037

  View details for Web of Science ID 000702098200001

• Soil and Aquifer Properties Combine as Predictors of Groundwater Uranium Concentrations within the Central Valley, California Environmental Science & Technology Lopez, A. M., Wells, A., Fendorf, S. 2020: 10

  View details for DOI 10.1021/acs.est.0c05591

• Protecting Groundwater Quality in California: Management Considerations for Avoiding Naturally Occurring and Emerging Contaminants Fakhreddine, S., Sherris, A., Lopez, A. M., Wells, A., Holmes, R., Nico, P., Bruton, T., Fendorf, S., Babbitt, C. Environmental Defense Fund. 2019 40