Editor’s choice: underappreciated science

In the environmental chemical sciences, roughly 10 000 papers are published in the peer reviewed scientific literature every year. So even our most prodigious readers only get exposed to a very small subset of papers within this sea of content, and somehow the process by which any specific paper reaches our attention is often all too random. Thus, it’s not surprising that there exist many interesting papers that just don’t get enough attention every year despite their technical merits and obvious implications. Here, within Environmental Science: Processes & Impacts, we like to call these papers “underappreciated science”, representing a diverse group of good papers that should really have more eyes on them and more pathways to the collective consciousness. All scientific authors probably have a paper or two they wished had gotten a little more attention and a good second chance at reaching some more eyeballs. Here, we have pulled together a few representative selections of recently published papers that deserve more of your attention into an “Underappreciated Science” collection; we hope you’ll find one or two enjoyable and thoughtful reads out of this list that you may have missed the first time!

Starting with a couple selections that fit a “long hot summer” afternoon reading theme, we first think about wildfires and their potential impacts on the chemistry of your drinking water. In “Wildfires and water chemistry: effect of metals associated with wood ash” (DOI: 10.1039/c6em00123h), Cerrato et al. investigated the dissolution and re-adsorption of metals from various ash residues to better understand the impacts of wildfires on water quality in semi-arid regions. Different tree species generate ashes of different chemical composition, these differences were quantified with X-ray diffraction and spectroscopy; subsequent metal transport from carbonate and oxide mineral phases in ash was observed to depend on system alkalinity and pH. Results from this effort are most relevant to understanding the transport and risk of metal exposures to drinking water supplies in post-wildfire watersheds.

In addition to increasing the incidence of wildfires, a warming climate has already increased the incidence of harmful algal blooms and algal toxin concentrations in drinking water supplies. In “Transformation of microcystins to 2-methyl-3-methoxy-4-phenylbutyric acid by room temperature ozone oxidation for rapid quantification of total microcystins” (DOI: 10.1039/c5em00588d), Zhang et al. developed an analytical method for measuring total microcystins in a water sample. Microcystin analysis is complicated by the fact that dozens of microcystin variants exist, and while existing methods of total microcystins analysis based on oxidation to a common product exist, they are complex and resource intensive. Zhang et al. optimized an ozone-based method to promote microcystin oxidation, simplifying sample pre-treatment, sensitivity, and accuracy of microcystin analysis in waters impacted by harmful algal blooms. Similarly focused on microcystins, Maghsoudi et al. identified a bacterial strain implicated in microcystin transformation in “Cyanotoxin degradation activity and mlr gene expression profiles of a Sphingopyxis sp. isolated from Lake Champlain, Canada” (DOI: 10.1039/c6em00001k). Biotransformation is a key fate outcome for cyanotoxins; under near neutral conditions a Sphingopyxis sp., designated strain MB-E, was able to transform several microcystins to products at time scales of hours to days. Genomic sequencing and transcriptomic analyses were used to identify key genes in the transformation pathway, and the pH dependence of the transformation pathways were evaluated with laboratory studies.

A couple of these papers have some interesting observations related to carbon budgets and GHG emissions. In “Landscape geomorphic characteristic impacts on greenhouse gas fluxes in exposed stream and riparian sediments” (DOI: 10.1039/c6em00162a), Vidon and Serchan investigated GHG fluxes at the soil–atmosphere interface in a variety of representative riparian systems, seeking to understand where significant GHG emissions were occurring in riparian watersheds. In particular, they noted the importance of methane (CH₄) production in riparian zones as being especially important to estimating accurate carbon fluxes from natural systems. Landscape geomorphic characteristics were considered to be especially promising potential predictors of GHG fluxes in watersheds. In “Evaluation of antibacterial and antifungal compounds for selective inhibition of denitrification in soils” (DOI: 10.1039/c6em00456c), Ladan and Jacinthe quantified the relative contribution of bacterial and fungal denitrifiers on nitrous oxide (N₂O) emissions from agricultural soils. Denitrification is a critical component of nitrogen cycles and global GHG emissions, and land use and agricultural management practices often intentionally or unintentionally alter denitrification rates, with subsequent impact on N₂O production. In this study, bacteria were identified as particularly important producers of N₂O in soils, thus GHG budgets should carefully consider the role and rates of bacterial production of GHG when agricultural denitrification inhibitors (e.g. biocides) are used to alter nitrogen cycling.

Mercury remains a problematic and difficult environmental pollutant subject to continued global interest. In “Key contributors to variations in fish mercury within and among freshwater reservoirs in Oklahoma, USA” (DOI: 10.1039/c5em00495k), Dong et al. assessed human exposures to environmentally persistent and ubiquitous mercury species in fish tissues by analyzing over 30 fish species (1300 samples) in 61 reservoirs. Surprisingly, small farm ponds were especially prone to disproportionately high mercury concentrations in food fish. Key factors governing mercury concentrations in fish were characterized, and the authors found that pH, water color, rainfall, and nutrients were effective predictors of total mercury concentrations in fish tissues. Outcomes from this work may help to improve exposure assessment and identify surface waters most in need of monitoring for mercury occurrence in fish tissues.

As illustrated by the mercury biogeochemistry study above, environmental redox conditions nearly always dominate fate outcomes for toxic environmental pollutants, yet relatively few researchers have focused on understanding pollutant fate in anoxic and reducing conditions. Probably the typically slow reaction kinetics and long experimental time scales have something to do with that glaring data gap! In “Transformation of chlorpyrifos and chlorpyrifos-methyl in prairie pothole pore waters” (DOI: 10.1039/c6em00404k), Adams et al. focused on the role of reduced sulfur species and environmental redox conditions to the abiotic fate of highly toxic organophosphate insecticides chlorpyrifos and chlorpyrifos-methyl. Notably, these studies were conducted in pore waters collected from prairie potholes, an ecologically rich and biogeochemically complex habitat quite significant to the Great Plains region of North America, yet highly impacted by agrochemicals. Bisulfide was shown to play a key role in abiotic transformation of chlorpyrifos-methyl via nucleophilic addition and dissolved organic matter typically governed both persistence and reactivity of these organophosphates in environmental waters.

We are overrun with synthetic chemicals and problematic environmental pollutants, and it’s clear that in the long term, computational simulation of contaminant fate processes are going to be our most powerful tool to understanding and predicting the environmental fate of anthropogenic pollutants. Trerayapiwat et al. take a strong step in that direction by providing a detailed and thoughtful framework for a priori prediction of photochemical pathways for pollutants in “Sticking to (first) principles: quantum molecular dynamics and Bayesian probabilistic methods to simulate aquatic pollutant absorption spectra” (DOI: 10.1039/c6em00233a). Using quantum chemical methods, excitation energies were predicted theoretically and compared to experimental molar absorption spectra to develop predictive capabilities for phototransformation rates. This research team makes a compelling case that quantum chemical and probabilistic computational tools will clearly provide detailed mechanistic insight and predictive capabilities with respect to environmental transformation reactions as these computational tools mature and are applied to environmental systems.

Along a similar predictive vein, in “A passive dosing method to determine fugacity capacities and partitioning properties of leaves” (DOI: 10.1039/c6em00423g), Bolinius et al. investigated the partitioning properties and capacity of leaf surfaces using a fugacity based model and polydimethylsiloxane sheets as passive dosing devices. This study developed a proof-of-concept approach that employed this PDMS passive dosing method as a reference phase to estimate partitioning coefficients for PCBs as model pollutants. Once the fugacity capacity of leaves is quantified, subsequent leaf–water and leaf–air partition coefficients are readily estimated. Outcomes of this study can be expected to help understand the variable partitioning capacities of leaves from different plant species and improve the quantitative estimation of uptake rates for high priority semi-volatile pollutants on leaf surfaces and vegetation.

Finally, we include a selection on the analytical methods development front. Huang et al. presented a simple and sensitive online derivatization HPLC/fluorescence method for aliphatic amines in “Quantitative analysis of aliphatic amines in urban aerosols based on online derivatization and high performance liquid chromatography” (DOI: 10.1039/c6em00197a). Intended to improve the analysis of aliphatic amines in atmospheric aerosols to better characterize organic nitrogen fluxes, this technique employed a sulfonatoisoindole derivative with excellent fluorescence properties for sensitivity at ng m⁻³ concentrations of particulate aliphatic amines. The described method, potentially suitable for high throughput online applications, was applied to fine particulate matter (PM_2.5 samples) collected from Shanghai, China to characterize concentrations and speciation of short chain amine compounds in aerosols. In particular, methylamine and ethanolamine were observed to dominate speciation of these low molecular weight amines in the method validation samples.

We hope you find a few of these great articles to appreciate. Enjoy!

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