Notes

This paper addresses how fire regime - the intensity, severity and frequency of fires - influences DOM quantity and composition in surface waters in forested catchments, and how long it takes for water quality to recover to pre-fire levels
A review of post-fire studies in Mediterranean regions reporting on DOM related parameters has been conducted. The literature shows that post-fire DOM composition and reactivity is different from DOM generated under processes of biological degradation, and hence our reliance on DOM 'bulk properties' and surrogate DOM bulk parameters may not provide sufficient information to deal with the potential complexity of the organic compounds produced by a catchment fire. Appropriate measures are important to adequately operate conventional water treatment facilities, for example. Critical parameters for the effects of burning include the alteration of DOM composition, aromaticity, and the relative amounts of labile/recalcitrant organic components. The literature shows mixed information for the influence of both burn severity and fire intensity, on these parameters, which indicates DOM response to fire is highly variable. For fire frequency, the evidence is more unequivocal, indicating that frequent fires change the composition of DOM to components that are less bioavailable, and elevate the degree of aromaticity, which may be detrimental to water quality.

In addition, and in general terms, the more recent the fire, the more aromatic and humified DOM components are found, and vice versa. The recovery of surface water quality to pre-fire conditions was variable, with no safe temporal thresholds suggested in the literature. In Seebio Light-Activated Acid Producer , fire-induced changes in DOM composition were observable up to 16 years post-fire. The lack of clearly observed trends in post-fire DOM with fire regimes could be attributed to numerous factors such as limited long-term and event-based observations, experimental design challenges, and site-specific biological, physical and hydrological factors. The application of terminologies used to describe fire regimes such as burn severity and fire intensity also creates challenges in comparing the outcomes and results from declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this Sorption and molecular fractionation of biochar-derived dissolved organic matter of Environmental Science and Engineering, Nankai University, Tianjin, 300350, of Environmental Science and Engineering, Nankai University, Tianjin, 300350, Molecular fractionation of dissolved organic matter (DOM) induced by the sorption on soil minerals is a common geochemical process in soil, which has been well documented on natural DOM. Biochar is an emerging soil amendment and can continuously release DOM into the soil. However, reports regarding the interactions of soil minerals and biochar-derived DOM are limited.

Herein, the molecular fractionation of DOMs derived from biochar samples obtained by pyrolyzing maize straw (MS) at 300 and 500 °C (M3 and M5) and MS (selected as the control) after sorption on ferrihydrite, a common soil mineral, was investigated for the first time. Results showed that biochar-derived DOMs contained greater aromatic and less aliphatic and O-containing structure compared to MSDOM. The sorption affinities of ferrihydrite for the three DOMs were in the order of M5DOM > M3DOM > MSDOM. A greater decrease in zeta potential and more external CO species were observed in ferrihydrite after sorption of M5DOM than after sorption of MSDOM or M3DOM. DOM components with high molecular weights and high contents of unsaturated oxidized or aromatic structures were preferentially sorbed by ferrihydrite via hydrophobic partition, H-bonding and electrostatic interactions. Polycyclic aromatics and polyphenols in MSDOM and M3DOM were the primary components sorbed by ferrihydrite, while the highly unsaturated and phenolic compounds in M5DOM showed stronger affinity to ferrihydrite. The oxygen-containing functional groups and unsaturation level are the primary parameters controlling the molecular fractionation of biochar-derived DOM on ferrihydrite.

The results of this study help to get deep insight on the environmental behavior of straw- and biochar-derived DOMs in declare no competing financial interest.Probing solvation and reactivity in ionized polycyclic aromatic hydrocarbon-water clusters with photoionization mass spectrometry and electronic Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian Polycyclic aromatic hydrocarbons (PAHs) may comprise up to 20% of the carbon budget in our galaxy and most PAHs condense onto water-rich icy grain mantles. Benzene-water clusters have been invoked as model systems for studying the photo-processing of water ice mantles containing PAHs. However, there is a paucity of information on larger aromatics, where the extended π cloud could affect photo-processing. In this study, tunable vacuum ultraviolet (VUV) photoionization of naphthalene-water clusters Nx(H2O)y (N denotes naphthalene) is performed using synchrotron radiation and analyzed by reflectron time-of-flight mass spectrometry. Naphthalene clusters up to x = 4 are generated as are naphthalene-water clusters up to y = 25.
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