About

John Reinfelder is a Professor in the Department of Environmental Sciences at Rutgers, the State University of New Jersey. His research focuses on aquatic biogeochemistry, phytoplankton physiology and ecology, mercury stable isotopes, sulfur geochemistry, acid mine drainage, and trace element accumulation in rice. He is involved in several current projects including the regulation of diatom physiology and stoichiometry by temperature, microbially catalyzed cycling of iron and other trace elements in soil, mercury cycling and bioaccumulation in the West Antarctic Peninsula's coastal marine ecosystem, and the accumulation of cadmium and other trace elements in rice. These projects often involve collaborations with researchers from institutions such as the Guangdong Institute of Eco-Environmental and Soil Sciences, Virginia Institute of Marine Sciences, and Polar Oceans Research Group. Professor Reinfelder's past research has addressed topics such as the regulation of diatom physiology and stoichiometry by CO2, carbon fixation in marine diatoms, biogeochemistry of arsenic in the Newark Basin, geomicrobiology of acid-mine drainage-contaminated soils, estuarine phytoplankton and organic carbon dynamics, and mercury stable isotopes in marine food webs. His work integrates field studies and laboratory investigations to understand elemental cycling and ecological processes in aquatic environments. He has collaborated with scientists from various universities including South China University of Technology, Rutgers, Delft, and National Taiwan University.

Research topics

• Chemistry
• Environmental chemistry
• Biology
• Photochemistry
• Environmental science
• Metallurgy
• Atmospheric sciences
• Geology
• Physics
• Meteorology
• Materials science
• Waste management
• Biophysics
• Nanotechnology
• Ecology
• Biochemistry
• Nuclear chemistry
• Environmental engineering
• Engineering
• Organic chemistry
• Oceanography

Selected publications

• Organosulfur compound-driven mobilization of colloidal metals and organic matter from acid mine drainage-contaminated paddy soils

  Journal of Hazardous Materials · 2026-03-09

  article
  PublisherDOI

• Effects of Equilibrium and Non‐Equilibrium Adsorption States on the Photoreduction and Isotope Fractionation of Hg(II) in Urban Aerosols

  Journal of Geophysical Research Atmospheres · 2026-03-11

  articleOpen accessCorresponding

  Abstract Mercury (Hg) photoreduction on urban aerosols plays a critical role in atmospheric Hg cycling, yet the effects of the adsorption state on its kinetics and isotopic fractionation remain poorly constrained. This study investigates Hg(II) photoreduction under equilibrium (EAC) and non‐equilibrium adsorption conditions (NAC) using a flow‐through semi‐batch suspension reactor. NAC resulted in photoreduction rates double those under EAC, attributable to a higher fraction of readily reducible, soluble Hg(II). A two‐compartment kinetic model confirmed faster aqueous‐phase than solid‐phase reduction, with efficiency enhanced at higher relative humidity (RH). Pronounced mass‐dependent fractionation (MDF) occurred: Hg(0) was enriched in light isotopes (δ 202 Hg ≤ −2.02‰), while the remaining Hg(II) became increasingly enriched in heavy isotopes. MDF was stronger under NAC (ε 202 Hg = 1.55–2.02‰) than EAC (1.30‰ at 68% RH), consistent with adsorption experiments showing preferential retention of heavy isotopes in the aqueous phase under EAC (δ 202 Hg up to 0.75‰). Mass‐independent fractionation (MIF) signals indicated odd‐isotope enrichment in the remaining Hg(II) (Δ 199 Hg up to 0.87‰) and depletion in Hg(0), consistent with magnetic isotope effects. Critically, instantaneous isotope fractionation trends revealed kinetic control: MDF decreased as the reaction slowed, whereas MIF peaked mid‐reaction before declining, supporting the two‐compartment model. By coupling the adsorption state to photoreaction kinetics and isotopic fractionation, this study provides a mechanistic basis for understanding Hg redox processes in urban aerosols. These findings underscore that adsorption history and RH jointly regulate Hg(II) reactivity and isotopic signatures—essential for refining atmospheric Hg models, particularly in urban environments with dynamic aerosol and moisture conditions.

  PublisherDOI

• The biological weathering of bastnaesite by Aspergillus niger and adsorption effect on dissolved La and Ce

  Chemical Geology · 2026-02-28

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  PublisherDOI

• Impaired development of offspring of eastern oysters Crassostrea virginica deployed in urban versus non-urban estuaries

  Marine Ecology Progress Series · 2025-11-10

  articleSenior author

  The eastern oyster Crassostrea virginica , a keystone species in estuaries along the Atlantic and Gulf coasts of the USA, holds significant economic and ecological importance globally. Despite ongoing oyster restoration efforts, challenges persist in urbanized estuaries. We examined the reproductive success of 18 mo old oysters deployed for 12 mo in 2 highly urbanized sites, Newark Bay and New York Bay, USA, and a reference site in southern New Jersey (Great Bay). Developmental endpoints of second-generation oysters were observed after strip spawning field-deployed oysters and rearing fertilized eggs through juvenile stages in a controlled laboratory setting. Our results highlight transitional larval phases, including the rarely recognized blastula and gastrula stages. Due to lower rates of fertilization and spat production, reproductive success for oysters deployed at the 2 urban sites was one-fourth to one-half of that for oysters deployed at the reference site, and the progeny of oysters deployed at the urban sites had poorly mineralized, eroded, and malformed shells. We observed that trochophore larvae from adults deployed at the urban sites had irregular shapes, underdeveloped embryonic ectoderm, and poor mineralization. Exposure of adults in the urbanized estuaries to chemical contamination, or to low salinity, dissolved oxygen or calcium carbonate saturation states, separately or in combination, may have impaired oyster reproduction. Our results indicate that while eastern oysters can tolerate environmental stress, the synergistic effects of multiple stressors may hinder their successful reproduction and limit the re-establishment of oyster populations in urban estuaries.

  PublisherDOI

• Phenol–Quinone Redox Couples of Natural Organic Matter Promote Mercury Methylation in Paddy Soil

  Environmental Science & Technology · 2025-01-07 · 16 citations

  article

  Methylmercury in paddy soils poses threats to food security and thus human health. Redox-active phenolic and quinone moieties of natural organic matter (NOM) mediate electron transfer between microbes and mercury during mercury reduction. However, their role in mercury methylation remains elusive. Here, artificial organic matter (AOM), i.e., biochar, wherein the phenol–quinone ratio and associated redox properties varied, was used as a redox-tunable model NOM to investigate the impact of the phenol–quinone redox couples on mercury methylation in Hg-contaminated paddy soils. Our findings confirm that AOM with higher phenol–quinone ratios (i.e., electron donor capacities) stimulated microbial methylation (4.9-fold increase) and dark abiotic methylation (2.2-fold increase). The phenol–quinone ratio had contrasting effects on the abundance of the Hg methylation gene hgcA and metabolic genes corresponding to Hg-methylating and demethylating clades (i.e., dsrA, dsrB, mcrA, and pmoA), especially under anaerobic (simulated flooding) conditions. The key Hg methylators were from Geobacteraceae, including Oryzomonas, Fundidesulfovibrio, and Geomobilimonas. The microbial methylation driven by the phenol–quinone ratio was further validated by NOM such as humic and fulvic acids. Notably, abiotic methylation was observed in aerobic sterilized soil, yet additional evidence is necessary to confirm the potential abiotic pathway, hampered by the difficulty of identifying effective methyl donors in soil. Our results reveal the potential of phenol–quinone redox properties in NOM to drive mercury methylation, offering novel insights into mercury methylation in paddy soils.

  PublisherDOI

• Physical Contact between Bacteria and Carbonaceous Materials: The Key Switch Triggering Activated Carbon and Biochar to Promote Microbial Iron Reduction

  Environmental Science & Technology · 2025-04-10 · 22 citations

  article

  Carbonaceous materials, including activated carbon and pyrolytic carbon, have been recognized for about over a decade as effective electron shuttles or conductive materials in promoting microbial Fe(III) mineral reduction. However, recent studies reveal inhibitory effects, sparking debates about their overall impact. We hypothesized that the physical contact between bacteria and carbon is an overlooked yet critical factor in determining whether carbon promotes or inhibits microbial Fe(III) reduction. Using systems containing Shewanella oneidensis MR-1, activated carbon, and ferrihydrite, we investigated how carbon–iron oxide aggregate structure affects Fe(III) reduction kinetics. At low activated carbon-to-iron oxide ratios (C/Fe = 5:7 by mass), ferrihydrite aggregated with carbon, forming carbon-encapsulated particles that suppressed Fe(III) reduction rates. Conversely, at higher ratios (C/Fe = 100:7), the ferrihydrite dispersed on the carbon surface, enhancing both the rate and extent of Fe(III) reduction. Tests with 11 different carbonaceous materials (activated carbon and biochar) all confirmed that the microstructure of iron oxides─whether encapsulating or dispersed─on carbon surfaces is critical for determining Fe(III) reduction rates. This insight resolves the debate on whether carbonaceous materials promote or inhibit Fe(III) mineral reduction and enhances our understanding of their roles in biogeochemical processes and environmental remediation.

  PublisherDOI

• Polyethylene microplastics and nanoplastics colored with inorganic pigments in aquatic environments: Effects of mechanical aging on physicochemical properties, aggregation kinetics, and metal release

  Journal of Hazardous Materials · 2025-07-15 · 5 citations

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  PublisherDOI

• Sweat-induced aggregation of nanoplastics with different sizes and functionalities: Implications for global and body-region variability in dermal penetration risks

  Journal of Hazardous Materials · 2025-07-01 · 4 citations

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  PublisherDOI

• Supporting Information for "Effects of Equilibrium and Non-Equilibrium Adsorption States on the Photoreduction and Isotope Fractionation of Hg(II) in Urban Aerosols"

  Zenodo (CERN European Organization for Nuclear Research) · 2025-12-16

  peer-reviewOpen access

  revised the informatino about Two-Compartment Pseudo-First-Order Rate Model and Data Analysis

  PublisherDOI

• Lipophilic Resazurin in Bioelectrochemical Systems: Role in Regulating Carbon Metabolic Pathways

  ChemElectroChem · 2025-06-16

  articleOpen access

  Lipophilic electron shuttles (ESs), such as phenazine and phenoxazine, can penetrate the outer membrane and enter the periplasmic space, mediating extracellular electron transfer reactions. This study investigates how lipophilic ESs (resazurin, a phenoxazine) regulate carbon metabolic pathways in bioelectrochemical systems using Shewanella oneidensis MR‐1 as a model organism. Through the analysis of acetate yield, CO 2 production, coulombic efficiency, and other parameters, it is found that resazurin increases coulombic efficiency (26% vs 17% for anthraquinone‐2,6‐disulfonic acid [AQDS]) and reduces acetate yield (82% vs 90% for AQDS) while slightly increasing CO 2 production (13.1% vs 11.8% for AQDS), indicating a shift in carbon metabolism. Transcriptome analysis reveals significant upregulation of genes involved in the NADH‐dependent metabolic pathway (e.g., nuoHIJKLMN ) and ATP synthesis ( atpABDEFGH ) under resazurin conditions. Mutant strains lacking key genes in oxidative phosphorylation (Δ atp ) or substrate‐level phosphorylation (Δ ack&pta ) further confirm the regulatory role of lipophilic shuttles. The study proposes that lipophilic ESs penetrate the periplasm, altering the redox state of inner‐membrane quinones and activating the NADH‐dependent metabolic pathway via the Arc system. This mechanism enhances TCA cycle activity and overall lactate metabolic efficiency. The findings provide insights into microbial carbon metabolic regulation and offer strategies for optimizing bioelectrochemical systems for bioremediation.

  PublisherOA PDFDOI

Recent grants

• ETBC: COLLABORATIVE RESEARCH: MASS-DEPENDENT AND INDEPENDENT MERCURY ISOTOPE FRACTIONATION DURING MICROBIAL METHYLATION AND REDOX TRANSFORMATIONS OF MERCURY IN NATURAL WATERS

  NSF · $398k · 2010–2014

• Microbial Controls on the Mobilization and Speciation of Arsenic from Newark Basin Shale

  NSF · $445k · 2004–2009

• Collaborative Research: Transformations and mercury isotopic fractionation of methylmercury by marine phytoplankton

  NSF · $230k · 2016–2019

Frequent coauthors

• Steven J. Eisenreich

  32 shared

• Robert Miskewitz

  19 shared

• Richard I. Hires

  18 shared

• W. Scott Douglas

  New Jersey Department of Transportation

  17 shared

• Zhi Dang

  South China University of Technology

  17 shared

• Lisa A. Totten

  Delaware River Basin Commission

  17 shared

• Tamar Barkay

  Rutgers, The State University of New Jersey

  17 shared

• Sandra M. Goodrow

  New Jersey Department of Environmental Protection

  17 shared

Labs

• Reinfelder RV Oceanus, New York BightPI

Education

• Ph.D. Oceanography

  Stony Brook University

  1993

• B.A. Biology

  Johns Hopkins University

  1987