Mobile Organic Compounds Research Articles

Occurrence and fate of perfluoroalkyl and polyfluoroalkyl substances (PFAS) in an urban aquifer located at the Besòs River Delta (Spain)

Urban aquifers are at risk of contamination from persistent and mobile organic compounds (PMOCs), especially per- and polyfluoroalkyl substances (PFAS), which are artificial organic substances widely used across various industrial sectors. PFAS are considered toxic, mobile and persistent, and have therefore gained significant attention in environmental chemistry. Moreover, precursors could transform into more recalcitrant products under natural conditions. However, there is limited information about the processes which affect their behaviour in groundwater at the field-scale. In this context, the aim of this study is to assess the presence of PFAS in an urban aquifer in Barcelona, and identify processes that control their evolution along the groundwater flow. 21 groundwater and 6 river samples were collected revealing the presence of 16 PFAS products and 3 novel PFAS. Short and ultra-short chain PFAS were found to be ubiquitous, with the highest concentrations detected for perfluorobutanesulfonic acid (PFBS), trifluoroacetic acid (TFA) and trifluoromethanesulfonic acid (TFSA). Long chain PFAS and novel PFAS were found to be present in very low concentrations (<50 ng/L). It was observed that redox conditions influence the behaviour of a number of PFAS controlling their attenuation or recalcitrant behaviour. Most substances showed accumulation, possibly explained by sorption/desorption processes or transformation processes, highlighting the challenges associated with PFAS remediation. In addition, the removal processes of different intensities for three PFAS were revealed. Our results help to establish the principles of the evolution of PFAS along the groundwater flow, which are important for the development of conceptual models used to plan and adopt site specific groundwater management activities (e.g., Managed Aquifer Recharge).

Phytotoxicity and hormesis in common mobile organic compounds in leachates of wood-derived biochars

AbstractAlthough addition of pyrolyzed organic materials (biochars) to soil generally results in increased growth and physiological performance of plants, neutral and negative responses have also commonly been detected. Toxicity of organic compounds generated during pyrolysis, sorbed by biochars, and then released into the soil solution, has been implicated as a possible mechanism for such negative effects. Conversely, water-soluble biochar constituents have also been suggested to have “hormetic” effects (positive effects on plants at low concentrations); however, no specific compounds responsible have been identified. We investigated the relative phytotoxicity—and possible hormetic effects—of 14 organic compounds common in aqueous extracts of freshly produced lignocellulosic biochars, using seed germination bioassays. Of the compounds examined, volatile fatty acids (VFAs: acetic, propionic, butyric, valeric, caproic, and 2-ethylbutyric acids) and phenol, showed acute phytotoxicity, with germination-based ED50 values of 1–30 mmol L−1, and 2-ethylbutyric acid showed ED50 values of 0.1–1.0 mmol L−1. Other compounds (benzene, benzoic acid, butanone, methyl salicylate, toluene, and 2,4-di-tert-butylphenol) showed toxic effects only at high concentrations close to solubility limits. Although phytotoxic at high concentrations, valeric and caproic acid also showed detectable hormetic effects on seedlings, increasing radicle extension by 5–15% at concentrations of ~ 0.01–0.1 mmol L−1. These data support the hypothesis that VFAs are the main agents responsible for phytotoxic effects of lignocellulosic biochar leachates, but that certain VFAs also have hormetic effects at low concentrations and may contribute to positive effects of biochar leachates on early plant development in some cases. Graphical Abstract

Predicting the impact and duration of persistent and mobile organic compounds in groundwater systems using a contaminant mass discharge approach

This study investigated methods for predicting the duration and impact on groundwater quality from persistent and mobile organic compounds (PMOCs) at a drinking water well field affected by multiple contaminant sources. The fungicide metabolite N,N-dimethylsulfamide (DMS), which frequently occurs above the Danish groundwater quality criterion (0.1 μg/L), was used as an example. By combining contaminant mass discharge (CMD) estimations, modeling, and groundwater dating, a number of important discoveries were made. The current center of contaminant mass was located near the source area. The CMD at the well field was predicted to peak in 2040, and an effect from the investigated sources on groundwater quality could be expected until the end of the 21st century. A discrepancy in the current CMD at the well field and the estimated arrival time from the studied source area suggested an additional pesticide source, which has not yet been thoroughly investigated. The presence of the unknown source was supported by model simulations, producing an improved mass balance after inclusion of a contaminant source closer to the well field.The approach applied here was capable of predicting the duration and impact of DMS contamination at a well field at catchment scale. It furthermore shows potential for identification and quantification of the contribution from individual sources, and is also applicable for other PMOCs. Predicting the duration of the release and impact of contaminant sources on abstraction wells is highly valuable for water resources management and authorities responsible for contaminant risk assessment, remediation, and long-term planning at water utilities.

Long-term leaching through clayey till of N,N-dimethylsulfamide, a Persistent and Mobile Organic Compound (PMOC)

Environmental pollution with Persistent and Mobile Organic Compounds (PMOC) from anthropogenic activities is an increasing cause for concern. These compounds are readily leached to groundwater aquifers and are likely to resist degradation, putting pressure on groundwater resources. Pesticides can form PMOCs upon degradation in the environment. The PMOC N,N-dimethylsulfamide (DMS) was the most frequently detected pesticide metabolite in Danish drinking water wells in 2020, although the pesticidal use of the last parent compound (tolylfluanid) ended in 2007. This study aimed to improve the understanding of the leaching of the PMOC DMS from clayey tills by combining a review of compound properties, sources and use, comprehensive field observations and numerical flow and solute transport modeling. The modeling explored the mechanisms of DMS retention during vertical transport in clayey till and the fingerprint in the underlying aquifer. The results were supported by detailed field observations at an agricultural site with strawberry production. Porewater samples were collected from clayey till to a depth of 12 m bgs by a custom designed installation method of suction cups. Groundwater sampling (249 samples) was designed to provide vertical concentration profiles at various distances from the presumed sources. The review of properties showed that the parent compounds and intermediates degrade quickly in topsoil, releasing the highly persistent and mobile DMS. We tested the effect of fractures on transport with different hydraulic apertures and a scenario without fractures by numerical modeling. The results showed that the presence of fractures can smooth the breakthrough curve below the clayey till, leading to faster breakthrough, lower maximum concentration, and several decades of prolonged leaching in simulations with the largest aperture (20 μm). The fracture-matrix interaction is a possible explanation for the observed delay of leaching from clayey till. The vertical concentration profiles in groundwater were used for identifying the sources at the field site and testing source strengths. Assigning one point source (200 μg/L) and two diffuse sources (40–50 μg/L) to the model produced vertical concentration profiles that compared well with observed field data in clayey till and the aquifer. All results were integrated into a conceptual model for the environmental fate of PMOCs in soil and groundwater. The findings of this study imply that the presence of fractures in clayey till should be considered in conceptual site models, since they can substantially prolong the leaching of PMOCs to groundwater. The integration of comprehensive field investigations and numerical modeling is key to understand the fate of PMOCs in complex field systems with different source types. Together with widespread occurrences of PMOCs in groundwater systems, the results highlight the need for improved approval procedures for pesticides and biocides which considers their persistent and mobile metabolites.

Dilute-and-shoot coupled to mixed mode liquid chromatography-tandem mass spectrometry for the analysis of persistent and mobile organic compounds in human urine

In this work, a comprehensive method for the simultaneous determination of 33 diverse persistent and mobile organic compounds (PMOCs) in human urine was developed by dilute-and-shoot (DS) followed by mixed-mode liquid chromatography coupled with tandem mass spectrometry (MMLC-MS/MS). In the sample preparation step, DS was chosen since it allowed the quantification of all targets in comparison to lyophilization. For the chromatographic separation, Acclaim Trinity P1 and P2 trimodal columns provided greater capacity for retaining PMOCs than reverse phase and hydrophilic interaction liquid chromatography. Therefore, DS was validated at 5 and 50 ng/mL in urine with both mixed mode columns at pH = 3 and 7. Regarding figures of merit, linear calibration curves (r2 > 0.999) built between instrumental quantification limits (mostly below 5 ng/mL) and 500 ng/mL were achieved. Despite only 60% of the targets were recovered at 5 ng/mL because of the dilution, all PMOCs were quantified at 50 ng/mL. Using surrogate correction, apparent recoveries in the 70–130% range were obtained for 91% of the targets. To analyse human urine samples, the Acclaim Trinity P1 column at pH = 3 and 7 was selected as a consensus between analytical coverage (i.e. 94% of the targets) and chromatographic runs. In a pooled urine sample, industrial chemicals (acrylamide and bisphenol S), biocides and their metabolites (2-methyl-4-isothiazolin-3-one, dimethyl phosphate, 6-chloropyridine-3-carboxylic acid, and ammonium glufosinate) and an artificial sweetener (aspartame) were determined at ng/mL levels. The outcomes of this work showed that humans are also exposed to PMOCs due to their persistence and mobility, and therefore, further human risk assessment is needed.

Supercritical Fluid Chromatography Coupled to High-Resolution Mass Spectrometry Reveals Persistent Mobile Organic Compounds with Unknown Toxicity in Wastewater Effluents.

Broad screening approaches for monitoring wastewater are normally based on reversed-phase liquid chromatography (LC) coupled to high-resolution mass spectrometry (HRMS). This method is not sufficient for the very polar micropollutants, neglected in the past due to a lack of suitable analytical methods. In this study, we used supercritical fluid chromatography (SFC) to detect very polar and yet-undetected micropollutants in wastewater effluents. We tentatively identified 85 compounds, whereas 18 have only rarely been detected and 11 have not previously been detected in wastewater effluents such as 17α-hydroxypregnenolone, a likely transformation product (TP) of steroids, and 1H-indole-3-carboxamide, a likely TP from new synthetic cannabinoids. Suspect screening of 25 effluent wastewater samples from 8 wastewater treatment plants revealed several distinct potential pollution sources such as a pharmaceutical company and a golf court. The analysis of the same samples with LC-HRMS showed clearly how SFC increases the ionization efficiency for low-molecular-weight micropollutants (m/z < 300 Da) by a factor 2 to 87 times, which significantly improved the mass spectra for identifying very polar compounds. In order to assess which micropollutants might be of environmental concern, literature and toxicological databases were screened. There was a lack of available hazard and bio-activity data for regulatory-relevant in vitro and in vivo assays for >50% of the micropollutants. Especially, 70% of the data were lacking for the whole organism (in vivo) tests.

Broad-range extraction of highly polar to non-polar organic contaminants for inclusive target analysis and suspect screening of environmental samples

The lack of carefully optimized extraction techniques for the analysis of compounds with diverse polarities limits the identification of toxic pollutants in aqueous environmental matrices, particularly those that are considered persistent and mobile organic compounds (PMOCs). Tailored extraction techniques for specific classes of chemicals often result in very low to no extraction of either very polar or relatively non-polar chemicals, depending on the sorbent used. Hence, it is crucial to develop a balanced extraction for a wider range of polarity, especially for non-target analysis of chemical residues, in order to capture the occurrence of the full profile of micropollutants. Herein, a tandem solid-phase extraction (SPE) technique incorporating both hydrophilic-lipophilic balance (HLB) and mixed-mode cation exchange (MCX) sorbents was developed to extract and analyze 60 model compounds with a wide range of polarities (log Kow from ‐1.9 to 5.5) from untreated sewage matrices. Extraction efficiencies were assessed in NanoPure™ water and untreated sewage samples; 51 compounds in NanoPure™ water and 44 compounds in untreated sewage had ≥60 % extraction recoveries using the developed tandem SPE method. The method limits of detection ranged from 0.25 to 88 ng/L in untreated sewage matrix. The applicability of the extraction method was demonstrated in untreated wastewater samples; using the tandem SPE for suspect screening analysis captured an additional 22 compounds that were not extracted when using the HLB sorbent only. The optimized SPE method was also evaluated for the extraction of per- and polyfluoroalkyl substances (PFAS) by analyzing the same sample extracts under negative electrospray ionization liquid chromatography-tandem mass spectrometry (LC-MS/MS). The wastewater samples revealed the presence of sulfonamide-, sulfonic-, carboxylic-, and fluorotelomer sulfonic- PFAS with chain lengths 8, 4–8, 4–9, and 8, respectively, indicating that the tandem SPE procedure provides an efficient one-step extraction for the analysis of PMOCs that include pharmaceuticals, pesticides, and PFAS.

Quantitation of guanidine derivatives as representative persistent and mobile organic compounds in water: method development

Persistent and mobile organic compounds (PMOCs) are highly soluble in water, thereby posing a threat to water resource quality. Currently, there are no methods that can accurately quantify guanidine derivative PMOCs, other than 1,3-diphenylguanidine (DPG) and cyanoguanidine (CG), in aqueous media. In this study, we developed a quantitation method that combines solid-phase extraction and liquid chromatography (LC)-tandem mass spectrometry to detect seven guanidine derivatives in aquatic environments and applied it to environmental water samples. Five LC columns were examined, and among them, a hydrophilic interaction liquid chromatography column was chosen owing to its suitable instrument detection limit and retention factor. Method precision was assessed using seven replicate analyses of river water. The corresponding analyte recoveries ranged from 73 to 137% (coefficient of variation = 2.1–5.8%). DPG and CG were detected in ultrapure water samples at levels up to 0.69 and 150 ng L−1, respectively; DPG and CG levels up to 44 and 2600 ng L−1, respectively, were detected in lake water, river water, sewage effluent, and tap water sampled in Western Japan. This is the first reported detection of DPG in the surface water of Japan, revealing that DPG and CG are ubiquitous compounds in aquatic environments. Moreover, this is the first study to detect 1-(o-tolyl)biguanide and N,N′′′-1,6-hexanediylbis(N′-cyanoguanidine) in water. This study provides a foundation for further research on the distribution, fate, and emission source of these pollutants, which is critical to maintain high water quality and to determine regulatory limits for these pollutants.Graphical

Identifying persistent, mobile and toxic (PMT) organic compounds detected in shale gas wastewater

Shale gas exploitation is a water-intensive process, generating flowback and produced water (FPW) with complex chemical compositions. Reuse, disposal and treatment of FPW are of increasing concern, because of the potential risk of FPW contamination to the surrounding aquatic environment and drinking water sources when emitted. Among numerous organic substances present in FPW, of particular concern are those that are persistent, mobile and toxic (PMT) and very persistent and very mobile (vPvM). PMT and vPvM substances have the greatest potential to spread in groundwater and are the hardest to remediate. This study presents the outcome of a literature review to identify organic compounds that were previously detected in FPW. The 162 target compounds identified from this review were assessed to see if they can be considered PMT/vPvM substances based on their substance properties. Our results indicated that most FPW substances are “not PMT”, accounting for 108 (66.7 %) compouds. In total 22 FPW substances can be considered PMT/vPvM or very likely to meet this criteria if more data were available. Examples of PMT substances in FPW include anthracene, 1,4-dioxane and 1,4-dichlorobenzene. PMT/vPvM compounds identified in FPW should be prioritized for risk management measures and monitoring in order to protect regional water resources.

Stormwater Bioretention Cells Are Not an Effective Treatment for Persistent and Mobile Organic Compounds (PMOCs).

Bioretention cells are a stormwater management technology intended to reduce the quantity of water entering receiving bodies. They are also used to reduce contaminant releases, but their performance is unclear for hydrophilic persistent and mobile organic compounds (PMOCs). We developed a novel eight-compartment one-dimensional (1D) multimedia model of a bioretention cell ("Bioretention Blues") and applied it to a spike and recovery experiment conducted on a system near Toronto, Canada, involving PMOC benzotriazole and four organophosphate esters (OPEs). Compounds with (log DOC) (organic carbon-water distribution coefficients) < ∼2.7 advected through the system, resulting in infiltration or underdrain flow. Compounds with log DOC > 3.8 were mostly sorbed to the soil, where subsequent fate depended on transformation. For compounds with 2.7 ≤ log DOC ≤ 3.8, sorption was sensitive to event size and compound-specific diffusion parameters, with more sorption expected for smaller rain events and for compounds with larger diffusion coefficients. Volatilization losses were minimal for all compounds tested. Direct uptake by vegetation also played a negligible role regardless of the compounds' physicochemical properties. Nonetheless, model simulations showed that vegetation could play a role by increasing transpiration, thereby increasing sorption to the bioretention soil and reducing PMOC release. Model results suggest design modifications to bioretention cells.

Electro-assisted removal of polar and ionic organic compounds from water using activated carbon felts

Highly water-soluble, persistent, and mobile organic compounds (PMOCs) are more and more often detected in surface and groundwater, evoking potential threats to the environment and human health. Traditional water treatment strategies, including adsorption by activated carbon materials, fail to efficiently remove PMOCs due to their hydrophilic nature. Electro-assisted sorption processes offer a clean, facile, and promising solution to remove PMOCs on activated carbon-based electrodes and potentially allow an easy on-site sorbent regeneration (trap&release). In this work, the electrosorption of five selected PMOCs, that is, tetrapropylammonium (TPA+), benzyltrimethylammonium (BTMA+), p-tosylate (p-TsO-), p-toluenesulfonamide (p-TSA), and methyl-tert-butyl ether (MTBE), were investigated on two comprehensively characterized activated carbon felt (ACF) types carrying different surface functionalities. Significant enrichment factors in ranges of 102 to 103 for charged PMOCs were expected by our first estimation for electro-assisted trap&release on ACFs in flow systems applying potentials in the range of −0.1 V/+0.6 V vs. SHE for ad-/desorption, respectively. Defunctionalized ACF carrying larger density in surface π-systems and lower O-content promises a higher capability in electrosorption processes than the pristine material in terms of better material stability (tested for 5 cycles over 500 h) and better removal efficiency of ionic PMOCs. To improve ACFs adsorption performance for cationic and anionic PMOCs, permanent chemical surface modification and reversible electric polarization as alternative strategies are compared. Our findings explore future electrode and process design of electrosorption for applications to treat water contaminated by emerging PMOCs.

Adsorption of polar and ionic organic compounds on activated carbon: Surface chemistry matters

Persistent and mobile organic compounds (PMOCs) are often detected micropollutants in the water cycle, thereby challenging the conventional wastewater and drinking water treatment techniques. Carbon-based adsorbents are often less effective or even unable to remove this class of pollutants. Understanding of PMOC adsorption mechanisms is urgently needed for advanced treatment of PMOC-contaminated water. Here, we investigated the effect of surface modifications of activated carbon felts (ACFs) on the adsorption of six selected PMOCs carrying polar or ionic groups. Among three ACFs, defunctionalized ACF bearing net positive surface charge at neutral pH provides the most versatile sorption efficiency for all studied PMOC types representing neutral, anionic and cationic compounds. Ion exchange capacity giving quantitative information of sorbent surface charges at specified pH is recognized as a frequently underestimated key property for evaluating adsorbents aiming at PMOC adsorption. A most recently developed prediction tool for Freundlich parameters in PMOC adsorption was applied and the prediction results are compared to the experimental data. The comparison demonstrates the so far underestimated importance of the sorbent surface chemistry for PMOC adsorption affinity and capacity. PMOC adsorption mechanisms were additionally investigated by adsorption experiments at various temperatures, pH values and electrolyte concentrations. Exothermic sorption was observed for all sorbate-sorbent pairs. Adsorption is improved for ionic PMOCs on AC carrying sites of the same charge (positive or negative) at increased electrolyte concentration, while not affected for neutral PMOCs unless strong electron donor-acceptor yet weak non-Coulombic interactions exist. Our findings will allow for better design and targeted application of activated carbon-based sorbents in water treatment facilities.

Investigation of polar mobile organic compounds (PMOC) removal by reverse osmosis and nanofiltration: rejection mechanism modelling using decision tree

Abstract Polar mobile organic compounds (PMOC) are highly polar chemicals and tend to accumulate in short water cycles. Due to their properties, PMOC might be partially eliminated by advanced water treatment technologies. The goal of this study is to investigate the rejection of 22 PMOC (highly mobile and persistent) by reverse osmosis (RO) and nanofiltration (NF) membranes. The impact of transmembrane pressure was evaluated through laboratory-scale cross-flow constant pressure filtration tests. Among the investigated experimental conditions, PMOC rejection with NF at eight bars is comparable to values obtained on RO at 15 bars. Negatively charged PMOC are highly rejected by both RO and NF membranes while guanidine-like compounds exhibit higher passage values and are strongly impacted by transmembrane pressure. In order to model the rejection mechanism, decision tree methodology was employed to link PMOC physicochemical properties to rejection values. Based on laboratory-scale results, decision trees were computed and emphasized that the NF rejection mechanism is governed by electrostatic interaction and sieving effects. In contrast, PMOC rejection on the RO membrane strongly depends on the topological polar surface area (TPSA) of the PMOC. This study suggests that micropollutant TPSA should be more investigated in order to describe RO removal efficiency. Moreover, it is shown that the decision tree is a powerful numerical tool in order to reveal the specific sequence leading to micropollutant removal by RO and NF membranes.

Getting to the root of the matter: Water-soluble and volatile components in thermally-treated biosolids and biochar differentially regulate maize (Zea mays) seedling growth.

The use of thermally treated biomass, including biochar, as soil amendments can improve soil fertility by providing nutrients, stable C and improving soil water-holding capacity. However, if the degree of carbonization is low, these soil amendments can lower crop productivity as a result of high salinity or organic compounds. The overall effect of these soil amendments is mediated by complex relationships between production conditions, soil properties and environmental conditions. This study aimed to 1) characterize the physiochemical properties and organic compounds released by three soil amendments (softwood biochar or pyrogenic carbonaceous biosolids), 2) determine the effects of these amendments on maize (Zea mays) seedling productivity, and 3) relate properties of these amendments to effects on maize seedling productivity under controlled environment conditions. Physicochemical properties and mobile organic compounds (water-soluble and volatile organic compounds were determined. The amendments were tested in maize germination and greenhouse experiments. Chemical fingerprinting of volatile and water-soluble compounds revealed over 100 mobile organic species. Increasing treatment temperature from 270 to 320°C reduces phytotoxicity of pyrogenic carbonaceous biosolids soil amendments. Water-soluble components of pyrogenic carbonaceous biosolids produced at 270°C (inorganic N, Na and/or organic compounds) were associated with reduced maize seedling productivity. Volatile components of pyrogenic carbonaceous biosolids produced at 320°C were associated with improved maize seedling productivity; nitrogen uptake was increased in spite of smaller root systems as a result of increased mineralization of soil or amendment N and/or uptake of organic N compounds. These results suggest that pyrogenic carbonaceous biosolids have potential benefits to provide plant nutrients when the amount of organic and inorganic species are limited during early growth stages, under greenhouse conditions. Future studies should examine these effects under field conditions to confirm whether controlled environment results translate into effects on yield.

Organophosphate Ester Transport, Fate, and Emissions in Toronto, Canada, Estimated Using an Updated Multimedia Urban Model.

Organophosphate esters (OPEs), used as flame retardants and plasticizers, occur at relatively high concentrations in urban air and surface waters. We tested the hypothesis that some OPEs could be considered persistent and mobile organic compounds (PMOCs), using the poly parameter linear free energy relationship-modified Multimedia Urban Model (ppLFER-MUM) in Toronto, Canada, as a case study. Modeled air emissions of ∑6OPEs of 3300 (190-190 000) kg yr-1 were 10-100 times higher than emissions of polychlorinated biphenyls (∑5PCBs) and polybrominated diphenyl ethers (∑5PBDEs). Model results suggested that measured ∑6OPE stream concentrations of ∼2000 ng L-1 originate from emissions to urban air transferred to water mostly via precipitation. Water transport removed 7-28% of total air inputs compared to 0.1-10% for PCBs and 2-10% for PBDEs. Chlorinated OPEs were efficiently transported via surface water due to their persistence and high solubility. Loadings of ∑6OPEs to Lake Ontario from wastewater treatment plants, streams, and atmospheric deposition were 70%, 18%, and 13%, respectively, of ∑6OPE loadings of 3100 (1200-45 000) kg yr-1. Our results support the hypothesis that three chlorinated OPEs, tris(2-chloroethyl)phosphate phosphate (TCEP), tris(chloroisopropyl)phosphate (TCiPP), and tris(1,3-dichloroisopropyl)phosphate (TDCiPP), fit the profile of PMOCs due to their mobility and persistence in surface waters.

Effect of clay and iron sulphate on volatile and water-extractable organic compounds in bamboo biochars

Improved plant disease resistance, seed germination and plant productivity have recently been associated with mineral-enhanced biochars. This has generated interest in characterizing those biochar organic compounds which may contribute to their favorable properties. This study builds on recent physico-chemical characterization of a series of mineral-enhanced bamboo biochars produced between 350 and 550 °C. Here, these biochars are subjected to aqueous extraction followed by liquid chromatography organic carbon detection (LC-OCD) and thermal desorption gas chromatography mass spectrometry (TD-GC/MS). These techniques provide a structural insight into their more bio-available organic compounds and how they vary with pyrolysis temperature. In comparison to neat biochar, their mineral-enhanced composites produce at least three times the water-extractable organic carbon, nitrogen and VOCs, and this increase is further amplified at pyrolysis higher temperatures. However, the biochar carbon fraction that is mobile is low, with total TD-GC/MS compatible VOCs reporting approximately 0.2% and LC-OCD solubles approximately 1–2%. Prior mineral impregnation of bamboo enhances the release of oxygenated compounds including humics and phenolics from its biochars. This increase in mobile oxygenates occurs at higher pyrolysis temperatures despite these minerals catalyzing lignocellulose condensation and carbonization. This anomaly is explained by oxygenates relatively small contribution and the self inerting batch pyrolysis conditions producing different biochar surface and bulk molecular properties. By describing the impact of mineral amendments on the yield and structure of mobile organic compounds that may be released from biochar, this work contributes to our understanding of biochar efficacy in soils.

Recent trends in water analysis triggering future monitoring of organic micropollutants

Water analysis has been an important area since the beginning of analytical chemistry. The focus though has shifted substantially: from minerals and the main constituents of water in the time of Carl Remigius Fresenius to a multitude of, in particular, organic compounds at concentrations down to the sub-nanogram per liter level nowadays. This was possible only because of numerous innovations in instrumentation in recent decades, drivers of which are briefly discussed. In addition to the high demands on sensitivity, high throughput by automation and short analysis times are major requirements. In this article, some recent developments in the chemical analysis of organic micropollutants (OMPs) are presented. These include the analysis of priority pollutants in whole water samples, extension of the analytical window, in particular to encompass highly polar compounds, the trend toward more than one separation dimension before mass spectrometric detection, and ways of coping with unknown analytes by suspect and nontarget screening approaches involving high-resolution mass spectrometry. Furthermore, beyond gathering reliable concentration data for many OMPs, the question of the relevance of such data for the aquatic system under scrutiny is becoming ever more important. To that end, effect-based analytics can be used and may become part of future routine monitoring, mostly with a focus on adverse effects of OMPs in specific test systems mimicking environmental impacts. Despite advances in the field of water analysis in recent years, there are still many challenges for further analytical research.Graphical abstractRecent trends in water analysis of organic micropollutants that open new opportunities in future water monitoring. HRMS high-resolution mass spectrometry, PMOC persistent mobile organic compounds

Thermal treatment and leaching of biochar alleviates plant growth inhibition from mobile organic compounds.

Recent meta-analyses of plant responses to biochar boast positive average effects of between 10 and 40%. Plant responses, however, vary greatly across systems, and null or negative biochar effects are increasingly reported. The mechanisms responsible for such responses remain unclear. In a glasshouse experiment we tested the effects of three forestry residue wood biochars, applied at five dosages (0, 5, 10, 20, and 50 t/ha) to a temperate forest drystic cambisol as direct surface applications and as complete soil mixes on the herbaceous pioneers Lolium multiflorum and Trifolium repens. Null and negative effects of biochar on growth were found in most cases. One potential cause for null and negative plant responses to biochar is plant exposure to mobile compounds produced during pyrolysis that leach or evolve following additions of biochars to soil. In a second glasshouse experiment we examined the effects of simple leaching and heating techniques to ameliorate potentially phytotoxic effects of volatile and leachable compounds released from biochar. We used Solid Phase Microextraction (SPME)–gas chromatography–mass spectrometry (GC-MS) to qualitatively describe organic compounds in both biochar (through headspace extraction), and in the water leachates (through direct injection). Convection heating and water leaching of biochar prior to application alleviated growth inhibition. Additionally, growth was inhibited when filtrate from water-leached biochar was applied following germination. SPME-GC-MS detected primarily short-chained carboxylic acids and phenolics in both the leachates and solid chars, with relatively high concentrations of several known phytotoxic compounds including acetic acid, butyric acid, 2,4-di-tert-butylphenol and benzoic acid. We speculate that variable plant responses to phytotoxic organic compounds leached from biochars may largely explain negative plant growth responses and also account for strongly species-specific patterns of plant responses to biochar amendments in short-term experiments.

Micro-XRF and FT-IR/ATR analyses of an optically degraded ancient document of the Trieste (Italy) cadastral system (1893): A novel and surprising iron gall ink protective action

This paper aims to identify causes and processes of an undesired age-related optical phenomenon in which two kinds of paper – a white paper and a green one – and an iron-gall ink are involved together with unavoidable environmental agents. Documents under examination are dated 1893 and come from the Trieste cadastral system archive (Ufficio del catasto tavolare di Trieste). The green paper, with a high content of lignin and kaolin is a pre-printed payment order used in accounting operations and it is adjacent to a white lignin-free paper. Diffused brown stains appear on the white paper mainly from being in prolonged contact with the green one which was handwritten using iron-gall ink. The green page induces a strong browning effect on the contact side of the white one, except for inked areas. The manuscript black lines of the lignin-containing page seem to protect the adjacent surface, where a mirror image appears. A particular type of mirror effect, which we propose to call negative mirror effect, is clearly evidenced. Micro-XRF (micro-X-ray fluorescence spectroscopy) and FT-IR ATR (attenuated total reflectance Fourier transform infrared spectroscopy) techniques were used to achieve information on both diagnostic inorganic and organic components. By way of our chemical model we can hypothesise the migration of oxidised brown low molecular weight extra-cellulose compounds (from lignin and/or hemicelluloses) from green recto to white verso pages. The browning process is only hindered in sharp correspondence with the areas of the green recto folio written with the iron-gall ink: this ink acts as a physical barrier to the migration or, as a second hypothesis, it is able to withhold the mobile organic compounds by way of a specific but still unknown interaction. In the field of scientific research on metal-gall ink corrosion this is a novel, interesting and surprising case of the reverse, in which the ink itself is not the cause of the corrosion, but the unforeseen preventive agent.

Relationships between Chemical Characteristics and Phytotoxicity of Biochar from Poultry Litter Pyrolysis.

Three biochars were prepared by intermediate pyrolysis from poultry litter at different temperatures (400, 500, and 600 °C with decreasing residence times) and compared with biochars from corn stalk prepared under the same pyrolysis conditions. The phytotoxicity of these biochars was estimated by means of seed germination tests on cress (Lepidium sativum L.) conducted in water suspensions (at 2, 5, and 40 g/L) and on biochars wetted according to their water-holding capacity. Whereas the seeds germinated after 72 h in water suspensions with corn stalk biochar were similar to the control (water only), significant inhibition was observed with poultry litter biochars. In comparison to corn stalk, poultry litter generated biochars with higher contents of ash, ammonium, nitrogen, and volatile fatty acids (VFAs) and a similar concentration of polycyclic aromatic hydrocarbons (PAHs). Results from analytical pyrolysis (Py-GC-MS) indicated that nitrogen-containing organic compounds (NCCs) and aliphatic components were distinctive constituents of the thermally labile fraction of poultry litter biochar. The inhibition of germination due to poultry litter biochar produced at 400 °C (PL400) was suppressed after solvent extraction or treatment with active sludge. A novel method based on solid-phase microextraction (SPME) enabled the identification of mobile organic compounds in PL400 capable of being released in air and water, including VFAs and NCCs. The higher phytotoxicity of poultry litter than corn biochars was tentatively attributed to hydrophilic biodegradable substances derived from lipids or proteins removable by water leaching or microbial treatments.