Uptake of the NO <Subscript>3</Subscript> Radical on Aqueous Surfaces

Using a single drop experiment, the uptake of NO₃ radicals on aqueous solutions of the dye Alizarin Red S and NaCl was measured at 293 K. Uptake coefficients in the range (1.7–3.1) ⋅ 10^{− 3} were measured on Alizarin Red S solutions. The uptake coefficients measured on NaCl solutions were in the range of (1.1–2.0) ⋅ 10⁻³ depending on the salt concentration. Both experiments lead to a consistent result for the mass accommodation coefficient of α_NO3 = (4.2_{− 1.7}^+2.2)⋅ 10⁻³. The product H(D_l k_Cl−^II)^0.5 for the NO₃ radical was determined to be (1.9 ± 0.2) M atm^{− 1} cm s^−0.5 M^−0.5 s^−0.5 by fitting the uptake data for the NaCl solutions to the so-called resistance model. The yield of the chemical NO₃ radical source was characterized using UV-VIS and FT-IR spectroscopy. The amount of gas-phase NO₃ radicals measured at elevated humidities was less than expected. Instead, a rise of the gas-phase HNO₃ concentration was found indicating a conversion of gas-phase NO₃ radicals to gas-phase HNO₃ on the moist reactor walls.     

Interactions of chlorpyrifos and methyl mercury: a mechanistic approach to assess chemical mixtures

The mechanism of interaction between chlorpyrifos, an organophosphate insecticide, and methyl mercury was assessed utilizing the amphipod, Hyalella azteca. Previous studies have demonstrated that chlorpyrifos and methyl mercury interact additively with survival as the endpoint. In addition, exposure to chlorpyrifos and methyl mercury increased the accumulation and decreased the elimination of methyl mercury. To further examine the mechanism responsible for these interactions, the in vivo and in vitro inhibition of acetylcholinesterase enzyme activity was assessed following exposure to methyl mercury and chlorpyrifos. In vivo, methyl mercury antagonized the effects of chlorpyrifos on acetylcholinesterase inhibition. Additional studies demonstrated that methyl mercury did not affect the in vitro bioactivation of chlorpyrifos or the subsequent inhibition of acetylcholinesterase enzyme activity. Chemical-chemical interactions were examined utilizing chromatographic techniques and suggested the formation of a chlorpyrifos-methyl mercury complex. The formation of this complex may result in increased accumulation of methyl mercury, apparent additive toxicity, and protection against chlorpyrifos-mediated acetylcholinesterase inhibition.     

CONVERSION RATES OF SURFACE HOX RADICALS IN BEIJING CITY

1INTRODUCTIONThe hydroxyl radicals play a central role in atmospher-ic photochemistry, reacting with a lot of compounds, often initiating their oxidation and subsequent loss and resulting in the formation of ozone and other deleteri-ous oxidants, acids, and fine particles in polluted ar-eas. A thorough understanding of this role is necessary for efficient, cost-effective pollution control. There-fore, the measurement of OH is very significant (E-HHAT etal., 1991). Nevertheless, most me…     

Treating ballast water with hydroxyl radical on introduced organisms

1 INTRODUCTION The introduction of invasive marine species into new environments by ship’s ballast water, by attaching to ships’ hulls or via other vectors has been recognized as one of the four major threats to the world’s oceans by Global Environment…     

Fe/Ag催化臭氧氧化降解苯酚的研究

为研究双金属催化剂去除有机污染物的效果,采用自制Fe/Ag催化剂对模拟苯酚废水进行了臭氧催化氧化处理。通过扫描电子显微镜(SEM)、比表面积分析仪(BET)和X射线衍射(XRD)对催化剂进行表征,并考察了催化剂类型、催化剂投加量和溶液初始pH值对降解效果的影响规律。结果表明:与Fe相比,Fe/Ag比表面积减少了22.8%,在Fe/Ag/O₃与含苯酚废水的反应体系中,反应遵循臭氧直接作用和活性自由基(·OH、·O₂、H₂O₂)共同作用的机理;Fe/Ag在反应过程中体现出良好的协同作用;300 mg/L的苯酚模拟废水在pH=6.3、Fe/Ag投加量为1.00 g的最优反应条件下经60 min反应,苯酚与化学需氧量(COD)去除率比单独臭氧氧化分别提高了18.4%和29.4%。     

Observing the atmospheric evolution of ozone-depleting substances

The atmospheric observations of ozone-depleting substances (ODSs) have been essential for following their atmospheric response to the production and use restrictions imposed by the Montreal Protocol and its Amendments and Adjustments. ODSs have been used since the first half of the 20th century in industrial and domestic applications. However, their atmospheric growth went unnoticed until the early 1970s, when they were discovered using gas chromatograph-electron capture detection (GC-ECD) instruments. Similar instrumentation formed the basis of global flask and in situ measurements commenced by NOAA and ALE/GAGE/AGAGE in the late 1970s. The combination of these networks, supported by a number of other laboratories, has been essential for following the tropospheric trends of ODSs. Additionally, ground-based remote sensing measurements within NDACC and aircraft-based observation programs have been crucial for measuring the evolution of the ODS abundances over the entire atmosphere. Maintaining these networks at least at their current state is vital for ensuring the on-going verification of the success of the Montreal Protocol.     

Formation of black carbon-like and alicyclic aliphatic compounds by hydroxyl radical initiated degradation of lignin

Exposure of lignin-derived organic matter (OM) to hydroxyl radicals originating from Fenton type reactions generates condensed aromatic and alicyclic aliphatic compounds, as shown using ultrahigh resolution mass spectrometry. Although condensed aromatic compounds are common in soil and dissolved OM, their presence has been attributed largely to combustion. A non-pyrogenic route for the formation of condensed aromatic compounds from lignin is suggested here, specifically that hydroxyl radical-initiated oxidation of lignin is capable of producing black carbon-like condensed aromatic compounds. Alicyclic aliphatic compounds are also produced, likely as part of a concerted process involving ring opening, polymerization and/or cyclization and hydrogen abstraction. Hydroxyl radicals associated with lignin degradation are produced through photochemistry in aqueous systems and enzymatic microbial processes in soil.     

ARIMA乘积季节模型在大坝位移监测中的应用

提出了应用ARIMA乘积季节模型对大坝位移监测数据进行分析和预报的新方法,并给出了基于开源R语言建立乘积季节模型的方法步骤和关键技术。结合某大坝径向位移监测数据进行计算分析,结果表明：ARIMA乘积季节模型能较准确地预报大坝位移趋势,具有较高的预测精度。     

Kinetic Determination of Trace Amounts of Nitrite Using an Optical Chemical Sensor

An optical chemical sensor (optode) is proposed for the kinetic determination of nitrite ion. The optode was fabricated by the immobilization of methyl violet on a triacetylcellulose polymeric membrane. Methyl violet is covalently bonded to a transparent triacetylcellulose film. By immersion of the sensor into an acidic nitrite solution, the absorbance of the sensor at 596 nm decreases with time that is due to the reaction of nitrite with the immobilized methyl violet. A fixed time method of 15 min was used to monitor the reaction. The linear range for the determination of nitrite was 0.20–8.00 µg mL^?1 and the limit of detection was 0.08 µg mL^?1. The optodes were one‐shot, they had durability more than 2 months and were easily prepared. The optode was successfully applied to the determination of nitrite ion in spring water and sewage samples.