Bioaccumulation and bioavailability of polybrominated diphynel ethers (PBDEs) in soil

Earthworms were exposed to artificially contaminated soils of DE-71 and DE-79 to investigate the bioaccumulation and bioavailability of PBDEs in soil. All major congeners were bioavailable to earthworms. The uptake and elimination rate coefficients of PBDEs decreased with their logK_ows. The biota soil accumulation factors of PBDEs also declined with logK_ow. These may be due to the large molecular size and the high affinity of PBDEs to soil particles. The concentrations extracted by Tenax for 6 h correlated very well with those found in earthworms, suggesting that the bioavailability of PBDEs in soil is related to the fraction of rapid desorption from soil. This also indicates that 6 h Tenax extraction is a good proxy for the bioavailability of PBDEs to earthworms in soil. The BSAFs of PBDEs in aged soil decreased 22-84% compared to freshly spiked soil, indicating that aging may diminish the bioavailability of PBDEs in soil significantly.     

Influence of pyrene combination state in soils on its treatment efficiency by Fenton oxidation

Interactions of hydrophobic organic compounds (HOCs) with soil organic matter (SOM) determine their combination state in soils, and therefore strongly influence their mobility, bioavailability, and chemical reactivity. Contact time (aging) of an HOC in soil also strongly influences its combination state and environmental fate. We studied Fenton oxidation of pyrene in three different soils to reveal the influences of SOM, contact time, and combination state on the efficiency of vigorous chemical reactions. Pyrene degradation efficiency depended strongly on the dose of oxidant (H(2)O(2)) and catalyst (Fe(2+)); the greatest degradation was achieved at an oxidant to catalyst molar ratio of 10:1. Pyrene degradation differed among the three soils, ranging from 65.4% to 88.9%. Pyrene degradation efficiency decreased with increasing SOM content, and the aromatic carbon content in SOM was the key parameter. We hypothesize that pyrene molecules that combine with the compact net structure of aromatic SOM are less accessible to Fenton oxidation. Furthermore, pyrene degradation efficiency decreased considerably after aged for 30 days, but further aging to 60 and 180 days did not significantly change degradation efficiency. The Fenton oxidation efficiency of pyrene in both unaged and aged soils was greater than the corresponding desorption rate during the same period, perhaps because Fenton reaction can make pyrene more accessible to the oxidant through the enhancement of HOCs' desorption by generating reductant species or by destroying SOM through oxidation.     

Effects of SOM, surfactant and pH on the sorption-desorption and mobility of prometryne in soils

Sorption and desorption of the herbicide prometryne in two types of soil subjected to the changes of pH and soil organic matter and surfactant were investigated. The sorption and desorption isotherms were expressed by the Freundlich equation. Freundlich K_f and n values indicate that soil organic matter was the major factor affecting prometryne behavior in the test soils. We also quantified the prometryne sorption and desorption behavior in soils, which arose from the application of Triton X-100 (TX100), a nonionic surfactant and change in pH. Application of TX100 led to a general decrease in prometryne sorption to the soils and an increase in desorption from the soils when applied in dosages of the critical micella concentration (CMC) 0.5, 1 and 2. At the concentration below the CMC, the non-ionic surfactant showed a tendency to decrease prometryne sorption and desorption. It appeared that TX100 dosages above CMC were required to effectively mobilize prometryne. Results indicate that the maximum prometryne sorption and minimum prometryne desorption in soils were achieved when the solution pH was near its pK_a. Finally, the influence of TX100 on the mobility of prometryne in soils using soil thin-layer chromatography was examined.     

热脱附气相色谱法测定大气中氯苯类化合物

使用热脱附解析气相色谱法测定7种氯苯类化合物。研究表明该方法在0.005~1.0mg/m3浓度范围内具有良好的线性关系,相关系数大于0.999,氯苯化合物回收率为95.2%~1 07%,相对标准偏差为2.6%~3.3%,检出限为0.005 m g/m3均能较好地满足实验室分析要求,且样品在热脱附管内保存期可达7d。     

Interactions of extracellular DNA with aromatized biochar and protection against degradation by DNase I

With increasing environmental application, biochar (BC) will inevitably interact with and impact environmental behaviors of widely distributed extracellular DNA (eDNA), which however still remains to be studied. Herein, the adsorption/desorption and the degradation by nucleases of eDNA on three aromatized BCs pyrolyzed at 700 °C were firstly investigated. The results show that the eDNA was irreversibly adsorbed by aromatized BCs and the pseudo-second-order and Freundlich models accurately described the adsorption process. Increasing solution ionic strength or decreasing pH below 5.0 significantly increased the eDNA adsorption on BCs. However, increasing pH from 5.0 to 10.0 faintly decreased eDNA adsorption. Electrostatic interaction, Ca ion bridge interaction, and π-π interaction between eDNA and BC could dominate the eDNA adsorption, while ligand exchange and hydrophobic interactions were minor contributors. The presence of BCs provided a certain protection to eDNA against degradation by DNase I. BC-bound eDNA could be partly degraded by nuclease, while BC-bound nuclease completely lost its degradability. These findings are of fundamental significance for the potential application of biochar in eDNA dissemination management and evaluating the environmental fate of eDNA.     

Effect of gastric fluid on adsorption and desorption of endocrine disrupting chemicals on microplastics

• Effect of gastric fluid on EDCs adsorption-desorption to microplastics was evaluated. • The gastric fluid enhanced desorption of EDCs on the surface of microplastics. • Adsorption and desorption isotherms fitted the Freundlich model well. • Desorption ratios of EE2 (55%–59%) on PVC were larger than that of E2 (49%–55%). • Decrease in pH and increase in ionic strength in gastric fluid strengthen desorption. Microplastics and endocrine disrupting chemicals are emerging pollutants in the marine environment because of their potential hazards. The effect of gastric fluid on the adsorption and desorption of 17β-estradiol (E2) and 17α-ethynylestradiol (EE2) to microplastics was investigated. The adsorption and desorption isotherms of E2/EE2 on microplastics could be well fitted by the Freundlich model while the Gibbs free energy of these processes were negative, proving that the reaction occurred spontaneously on the heterogeneous surface of the microplastics. Desorption ratios of EE2 (55%–59%) on PVC were larger than that of E2 (49%–55%) to indicate that EE2 was less stable in gastric fluid, which could be explained by the fact that the hydrophobicity of EE2 was greater than E2. E2/EE2 were more easily desorbed from PVC in the gastric fluid and the desorption amount (5.25–12.91/7.19–17.86 μg/g) increased by 2.51 times in comparison with that in saline solution (2.22–7.81/2.87–10.80 μg/g). The decrease of pH and the increase of ionic strength in gastric fluid could further strengthen desorption of E2/EE2 from PVC. The promotion of gastric juice on desorption of PVC was achieved by reducing the hydrophobicity of the PVC surface. The desorption rate of E2/EE2 at 18°C and 38°C was respectively 44%–47%/46%–50% and 49%–55%/56%–59%, indicating that PVC loaded with E2/EE2 had a relatively greater risk of releasing pollutants in the gastric fluid of constant temperature marine organisms while higher temperatures exposed higher hazards for variable temperature animals. The interaction between microplastics and pollutants might be mainly hydrophobic interaction.     

Contributions of adsorption,bioreduction and desorption to uranium immobilization by extracellular polymeric substances

● EPS immobilizes U(VI) via adsorption, bioreduction and desorption. ● This work provides a framework to quantify the three immobilization processes. ● The non-equilibrium adsorption of U follows pseudo-second-order kinetics. ● The equilibrium adsorption of U followed Langmuir and Freundlich isotherms. Hexavalent uranium (U(VI)) can be immobilized by various microbes. The role of extracellular polymeric substances (EPS) in U(VI) immobilization has not been quantified. This work provides a model framework to quantify the contributions of three processes involved in EPS-mediated U(VI) immobilization: adsorption, bioreduction and desorption. Loosely associated EPS was extracted from a pure bacterial strain, Klebsiella sp. J1, and then exposed to H₂ and O₂ (no bioreduction control) to immobilize U(VI) in batch experiments. U(VI) immobilization was faster when exposed to H₂ than O₂ and stabilized at 94% for H₂ and 85% for O₂, respectively. The non-equilibrium data from the H₂ experiments were best simulated by a kinetic model consisting of pseudo-second-order adsorption (k_a = 2.87 × 10⁻³ g EPS·(mg U)⁻¹·min⁻¹), first-order bioreduction (k_b = 0.112 min⁻¹) and first-order desorption (k_d = 7.00 × 10⁻³ min⁻¹) and fitted the experimental data with R² of 0.999. While adsorption was dominant in the first minute of the experiments with H₂, bioreduction was dominant from the second minute to the 50^th min. After 50 min, adsorption was negligible, and bioreduction was balanced by desorption. This work also provides the first set of equilibrium data for U(VI) adsorption by EPS alone. The equilibrium experiments with O₂ were well simulated by both the Langmuir isotherm and the Freundlich isotherm, suggesting multiple mechanisms involved in the interactions between U(VI) and EPS. The thermodynamic study indicated that the adsorption of U(VI) onto EPS was endothermic, spontaneous and favorable at higher temperatures.     

Combined effect of nonionic surfactant Tween 80 and DOM on the behaviors of PAHs in soil--water system

Batch experiments were performed to examine the desorption behavior of phenanthrene and pyrene in soil–water system in the presence of nonionic surfactant Tween 80 and dissolved organic matter (DOM) derived from pig manure or pig manure compost. Addition of 150 mg l⁻¹ Tween 80 desorbed 5.8% and 2.1% of phenanthrene and pyrene from soil into aqueous phase, respectively, while the addition of both Tween 80 and DOM derived from pig manure compost and pig manure could further enhance the desorption of phenanthrene to 15.8% and 16.2%, respectively, and 6.4% and 10.9%, respectively, for pyrene. In addition, our finding also suggested that subsequent addition of Tween 80 into the soil–water system could further enhance PAHs desorption. The enhancement effect of the co-existence of Tween 80 and DOM was more than the additive effect of the Tween 80 and DOM individually. It is likely that the formation of DOM–surfactant complex in the soil–water system may be a possible reason to explain such desorption enhancement phenomenon. Therefore, it is anticipated that the coexistence of both Tween 80 and DOM derived from pig manure or pig manure compost in soil environment will enhance the bioavailability of PAHs as well as other hydrophobic organic contaminants (HOCs) by enhancing the desorption during remediation process.     

RA-915^＋型测汞仪快速测定土壤中的总汞

本文采用RA-915＋型测汞仪建立了一种快速测定土壤中总汞的热解析冷原子吸收分光光度法。该方法使用土壤标准样品直接固体进样建立标准曲线,不需要任何样品前处理消解过程,可在几分钟内快速测量1个土壤样品中的总汞含量。采用该方法分析了ESS系列4个土壤标准样品和GSS系列15个土壤标准样品,并与原子荧光法比对分析了9个土壤实际样品,结果表明本方法具有快速、准确、简便和稳定性较高等优点。     

Adsorption–desorption behavior of atrazine on agricultural soils in China

Adsorption and desorption are important processes that affect atrazine transport,transformation,and bioavailability in soils.In this study,the adsorption–desorption characteristics of atrazine in three soils(laterite,paddy soil and alluvial soil) were evaluated using the batch equilibrium method.The results showed that the kinetics of atrazine in soils was completed in two steps:a"fast" adsorption and a "slow" adsorption and could be well described by pseudo-second-order model.In addition,the adsorption equilibrium isotherms were nonlinear and were well fitted by Freundlich and Langmuir models.It was found that the adsorption data on laterite,and paddy soil were better fitted by the Freundlich model;as for alluvial soil,the Langmuir model described it better.The maximum atrazine sorption capacities ranked as follows:paddy soil alluvial soil laterite.Results of thermodynamic calculations indicated that atrazine adsorption on three tested soils was spontaneous and endothermic.The desorption data showed that negative hysteresis occurred.Furthermore,lower solution pH value was conducive to the adsorption of atrazine in soils.The atrazine adsorption in these three tested soils was controlled by physical adsorption,including partition and surface adsorption.At lower equilibrium concentration,the atrazine adsorption process in soils was dominated by surface adsorption;while with the increase of equilibrium concentration,partition was predominant.