Soil’s Hidden Power : The Stable Soil Organic Carbon Pool Controls the Burden of Persistent Organic Pollutants in Background Soils

Persistent organic pollutants (POPs) tend to accumulate in cold regions by cold condensation and global distillation. Soil organic matter is the main storage compartment for POPs in terrestrial ecosystems due to deposition and repeated air–surface exchange processes. Here, physicochemical properties and environmental factors were investigated for their role in influencing POPs accumulation in soils of the Tibetan Plateau and Antarctic and Arctic regions. The results showed that the soil burden of most POPs was closely coupled to stable mineral-associated organic carbon (MAOC). Combining the proportion of MAOC and physicochemical properties can explain much of the soil distribution characteristics of the POPs. The background levels of POPs were estimated in conjunction with the global soil database. It led to the proposition that the stable soil carbon pools are key controlling factors affecting the ultimate global distribution of POPs, so that the dynamic cycling of soil carbon acts to counteract the cold-trapping effects. In the future, soil carbon pool composition should be fully considered in a multimedia environmental model of POPs, and the risk of secondary release of POPs in soils under conditions such as climate change can be further assessed with soil organic carbon models

An international laboratory comparison of dissolved organic matter composition by high resolution mass spectrometry: Are we getting the same answer?

High-resolution mass spectrometry (HRMS) has become a vital tool for dissolved organic matter (DOM) characterization. The upward trend in HRMS analysis of DOM presents challenges in data comparison and interpretation among laboratories operating instruments with differing performance and user operating conditions. It is therefore essential that the community establishes metric ranges and compositional trends for data comparison with reference samples so that data can be robustly compared among research groups. To this end, four identically prepared DOM samples were each measured by 16 laboratories, using 17 commercially purchased instruments, using positive-ion and negative-ion mode electrospray ionization (ESI) HRMS analyses. The instruments identified ~1000 common ions in both negative- and positive-ion modes over a wide range of m/z values and chemical space, as determined by van Krevelen diagrams. Calculated metrics of abundance-weighted average indices (H/C, O/C, aromaticity, and m/z) of the commonly detected ions showed that hydrogen saturation and aromaticity were consistent for each reference sample across the instruments, while average mass and oxygenation were more affected by differences in instrument type and settings. In this paper we present 32 metric values for future benchmarking. The metric values were obtained for the four different parameters from four samples in two ionization modes and can be used in future work to evaluate the performance of HRMS instruments

Solid-phase extraction-stepwise elution (SPE-SE) procedure for isolation of dissolved organic matter prior to ESI-FT-ICR-MS analysis

Characterization of dissolved organic matter (DOM) at the molecular level will greatly improve our understanding of its bio-geochemical role in controlling the fate of contaminants in the environment, and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) is the most powerful analytical technique for this purpose. Before FT-ICR-MS analysis, isolation, desalination and concentration of DOM are necessary, and solid-phase extraction (SPE) is the most widely applied pretreatment procedure. However, some molecular information is lost using conventional SPE methods. Here, we propose a novel strategy of SPE enrichment using stepwise elution (SPE-SE). Compounds in DOM were divided into three fractions by this SPE-SE procedure according to their polarity and ionization efficiency. The diversity of DOM molecules identified by ESI-FT-ICR-MS using SPE-SE exceeded those using conventional SPE methods by more than 50%. This method is feasible and has the potential to be used as a pretreatment strategy for complex DOM matrixes prior to ESI-FT-ICR-MS analysis, especially for those rich in nitrogenous molecules, carbohydrates, lipids and/or aromatic compounds. (C) 2016 Elsevier B.V. All rights reserved

Cellular internalization and intracellular biotransformation of silver nanoparticles in <i>Chlamydomonas reinhardtii</i>

<p>It is necessary to elucidate cellular internalization and intracellular biotransformation in order to accurately assess the toxicity and fate of nanoparticles after interaction with organisms. Therefore, this work employed a combination of high resolution imaging and <i>in situ</i> detection spectroscopic techniques to systematically investigate the intracellular localization, morphology and chemical speciation of silver in the cells of <i>Chlamydomonas reinhardtii</i>, a unicellular freshwater green alga, after exposure to AgNPs coated with polyvinylpyrrolidone at a concentration of 2.0 mg/L. High resolution secondary ion mass spectrometry and high-angle annular dark field scanning transmission electron microscopy together with energy dispersive spectroscopy and selected area electron diffraction collectively confirmed that after 48 h of exposure, AgNPs entered the periplasmic space after cellular internalization into the algal cells. Silver was also found to coexist with sulfur inside the cytoplasm in both crystalline and amorphous forms, which were further identified as β-Ag₂S and silver thiolates with synchrotron X-ray absorption spectroscopy. In combination, these analyses demonstrated that silver inside algae could be attributed to the uptake and sequestration of Ag⁺ ion released from AgNPs, which was further sequestrated into cellular compartments. This study provides solid evidence for particle internalization and biotransformation of AgNPs after interaction with algae.</p

Molecular Characterization Related to Ovary Early Development Mechanisms after Eyestalk Ablation in <i>Exopalaemon carinicauda</i>

Eyestalk ablation is an effective method to promote ovarian development in crustaceans. Herein, we performed transcriptome sequencing of ovary and hepatopancreas tissues after eyestalk ablation in Exopalaemon carinicauda to identify genes related to ovarian development. Our analyses led to the identification of 97,383 unigenes and 190,757 transcripts, with an average N50 length of 1757 bp. In the ovary, four pathways related to oogenesis and three related to oocyte rapid growth were enriched. In the hepatopancreas, two vitellogenesis-associated transcripts were identified. Furthermore, short time-series expression miner (STEM) and gene ontology (GO) enrichment analyses revealed five terms related to gamete generation. In addition, two-color fluorescent in situ hybridization results suggested that dmrt1 might play a vital role in oogenesis during the early stage of ovarian development. Overall, our insights should support future studies focusing on investigating oogenesis and ovarian development in E. carinicauda.</i

Uptake, Translocation, and Biotransformation of Organophosphorus Esters in Wheat (<i>Triticum aestivum</i> L.)

The uptake, translocation and biotransformation of organophosphate esters (OPEs) by wheat (<i>Triticum aestivum</i> L.) were investigated by a hydroponic experiment. The results demonstrated that OPEs with higher hydrophobicity were more easily taken up by roots, and OPEs with lower hydrophobicity were more liable to be translocated acropetally. A total of 43 metabolites including dealkylated, oxidatively dechlorinated, hydroxylated, methoxylated, and glutathione-, and glucuronide- conjugated products were detected derived from eight OPEs, with diesters formed by direct dealkylation from the parent triesters as the major products, followed with hydroxylated triesters. Molecular interactions of OPEs with plant biomacromolecules were further characterized by homology modeling combined with molecular docking. OPEs with higher hydrophobicity were more liable to bind with <i>Ta</i>LTP1.1, the most important wheat nonspecific lipid transfer protein, consistent with the experimental observation that OPEs with higher hydrophobicity were more easily taken up by wheat roots. Characterization of molecular interactions between OPEs and wheat enzymes suggested that OPEs were selectively bound to <i>Ta</i>GST4–4 and CYP71C6v1 with different binding affinities, which determined their abilities to be metabolized and form metabolite products in wheat. This study provides both experimental and theoretical evidence for the uptake, accumulation and biotransformation of OPEs in plants