预应力混凝土连续小箱梁桥荷载试验研究

为评估鄂钢东西区连接公路桥在正常运营状态下的承载能力和安全性,选取该桥第一、三联的预应力混凝土连续小箱梁进行静、动荷载试验。在静荷载下测试最不利断面的应力和挠度,通过动荷载试验来测试该桥的自振频率、振幅和冲击系数,并与理论值进行对比。结果表明：主梁测试桥面的挠度校验系数和断面的应力校验系数的理论值大于实测值,其最大相对残余变形和残余应变率均不超过20%;第一、三联一阶竖向振动频率实测值分别为3.20、3.55 Hz,实测值均大于计算值,结构整体刚度满足要求;第一、三联实测桥梁冲击系数分别在0.12～0.16和0.15～0.18,桥梁在冲击荷载作用下能正常运营。在正常运营状态下,桥梁结构的整体刚度满足设计要求,且处于弹性工作状况,该桥的自振频率和冲击系数均在合理范围内,表明鄂钢东西区连接公路桥整体承载能力满足公路I级荷载要求。     

Toward better understanding vacuum ultraviolet–iodide induced photolysis via hydrogen peroxide formation,iodine species change,and difluoroacetic acid degradation

• UV/VUV/I^– induces substantial H₂O₂ and IO₃^– formation, but UV/I^– does not. • Increasing DO level in water enhances H₂O₂ and iodate productions. • Increasing pH decreases H₂O₂ and iodate formation and also photo-oxidation. • The redox potentials of UV/VUV/I^– and UV/VUV changes with pH changes. • The treatability of the UV/VUV/I^– process was stronger than UV/VUV at pH 11.0. Recently, a photochemical process induced by ultraviolet (UV), vacuum UV (VUV), and iodide (I^–) has gained attention for its robust potential for contaminant degradation. However, the mechanisms behind this process remain unclear because both oxidizing and reducing reactants are likely generated. To better understand this process, this study examined the evolutions of hydrogen peroxide (H₂O₂) and iodine species (i.e., iodide, iodate, and triiodide) during the UV/VUV/I^– process under varying pH and dissolved oxygen (DO) conditions. Results show that increasing DO in water enhanced H₂O₂ and iodate production, suggesting that high DO favors the formation of oxidizing species. In contrast, increasing pH (from 6.0 to 11.0) resulted in lower H₂O₂ and iodate formation, indicating that there was a decrease of oxidative capacity for the UV/VUV/I^– process. In addition, difluoroacetic acid (DFAA) was used as an exemplar contaminant to verify above observations. Although its degradation kinetics did not follow a constant trend as pH increases, the relative importance of mineralization appeared declining, suggesting that there was a redox transition from an oxidizing environment to a reducing environment as pH rises. The treatability of the UV/VUV/I^– process was stronger than UV/VUV under pH of 11.0, while UV/VUV process presented a better performance at pH lower than 11.0.     

Migration,Transformation and Removal of Macrolide Antibiotics in The Environment: A Review

Environmental Science and Pollution Research - Macrolide antibiotics (MAs), as a typical emerging pollutant, are widely detected in environmental media. When entering the environment, MAs can...     

National emissions inventory and future trends in greenhouse gases and other air pollutants from civil airports in China

Environmental Science and Pollution Research - Civil aviation is an important source of air pollutants, but this field has received insufficient attention in China. Based on the standard emissions...     

Enhanced reductive dechlorination in columns treated with edible oil emulsion

The effect of edible oil emulsion treatment on enhanced reductive dechlorination was evaluated in a 14 month laboratory column study. Experimental treatments included: (1) emulsified soybean oil and dilute HCl to inhibit biological activity; (2) emulsified oil only; (3) emulsified oil and anaerobic digester sludge; and (4) continuously feeding soluble substrate. A single application of emulsified oil was effective in generating strongly reducing, anaerobic conditions for over 14 months. PCE was rapidly reduced to cis-DCE in all three live columns. Bioaugmentation with a halorespiring enrichment culture resulted in complete dechlorination of PCE to ethene in the soluble substrate column (yeast extract and lactate). However, an additional treatment with a pulse of yeast extract and bioaugmentation culture was required to stimulate complete dechlorination in the emulsion treated columns. Once the dechlorinating population was established, the emulsion only column degraded PCE from 90-120 microM to below detection with concurrent ethene production in a 33 day contact time. The lower biodegradation rates in the emulsion treated columns compared to the soluble substrate column suggest that emulsified oil barriers may require a somewhat longer contact time for effective treatment. In the HCl inhibited column, partitioning of PCE to the retained oil substantially delayed PCE breakthrough. However, reduction of PCE to more soluble degradation products (cis-DCE, VC and ethene) greatly reduced the impact of oil-water partitioning in live columns. There was only a small decline in the hydraulic conductivity (K) of column #1 (low pH+emulsion, K(final)/K(initial)=0.57) and column #2 (live+emulsion, K(final)/K(initial)=0.73) indicating emulsion injection did not result in appreciable clogging of the clayey sand. However, K loss was greater in column #3 (sludge+emulsion, K(final)/K(initial)=0.12) and column #4 (soluble substrate, K(final)/K(initial)=0.03) indicating clogging due to biomass and/or gas production can be significant.     

An exploration of the relationship between adsorption and bioavailability of pesticides in soil to earthworm

A study was conducted to determine the adsorption/desorption of butachlor, myclobutanil and chlorpyrifos on five soils using a batch equilibration technique and to study the relationship between bioavailability to Allolobophora caliginosa and the adsorption/desorption of these three pesticides. The results showed that the adsorption/desorption processes of the tested compounds were mainly controlled by soil organic matter content (OM) and octanol/water-partitioning coefficient (K(ow)), and that the bioavailability of the pesticides was dependent on characteristics of pesticides, properties of soils, and uptake routes of earthworms. Bioconcentration of butachlor and myclobutanil was negatively correlated with Freundlich adsorption constant K(af) and K(df). However, only a slightly positive correlation between bioconcentration and K(af) and K(df) was observed for chlorpyrifos due to its high affinity onto soil.     

The measurement of fine particulate semivolatile material in urban aerosols

Ammonium nitrate and semivolatile organic material (SVOM) are significant components of fine particles in urban atmospheres. These components, however, are not properly determined with methods such as the fine particulate matter (PM2.5) Federal Reference Method (FRM) or other single filter samplers because of significant losses of semivolatile material (SVM) from particles collected on the filter during sampling. The R&P tapered element oscillating microbalance (TEOM) monitor also does not measure SVM, because this method heats the sample to remove particle bound water, which also results in evaporation of SVM. Recent advances in monitoring techniques have resulted in samplers for both integrated and continuous measurement of total PM2.5, including the particle concentrator-Brigham Young University organic sampling system (PC-BOSS), the real-time total ambient mass sampler (RAMS), and the R&P filter dynamics measurement system (FDMS) TEOM monitor. Results obtained using these samplers have been compared with those obtained with either a PM2.5 FRM sampler or a TEOM monitor in studies conducted during the past five years. These studies have shown the following: (1) the PC-BOSS, RAMS, and FDMS TEOM are all comparable. Each instrument measures both the nonvolatile material and the SVM. (2) The SVM is not retained on the heated filter of a regular TEOM monitor and is not measured by this sampling technique. (3) Much of the SVM is also lost during sampling from single filter samplers such as the PM2.5 FRM sampler. (4) The amount of SVM lost from single filter samplers can vary from less than one-third of that lost from heated TEOM filters during cold winter conditions to essentially all during warm summer conditions. (5) SVOM can only be reliably collected using an appropriate denuder sampler. (6) A PM2.5 speciation sampler can be easily modified to a denuder sampler with filters that can be analyzed for semivolatile organic carbon (OC), nonvolatile OC, and elemental carbon using existing OC/elemental carbon analytical techniques. The research upon which these statements are based for various urban studies are summarized in this paper.     

Predictive abilities of numerical sediment quality guidelines in Sydney Harbour, Australia, and vicinity

Matching chemical and toxicological data of surficial sediments from Sydney Harbour, Australia, and vicinity, were collected to evaluate predictive abilities of Effects Range-Low (ERL), Effects Range-Median (ERM) and other sediment quality guidelines (SQGs). Samples (n=103) containing a wide range of chemicals and concentrations were subjected to a battery of 4-6 toxicity tests. ERLs and functionally equivalent low-range SQGs were highly predictive of non-toxicity when not exceeded, as incidences of toxicity were 0-8%. ERMs and other mid-range SQGs were predictive of toxicity in combined test data with > or = 80% of toxic samples with one or more SQG exceeded. Predictive abilities of mid-range SQGs were low for amphipod survival tests (generally < 20% toxic samples), but the incidence of toxicity increased with increasing numbers of SQGs exceeded and increasing mean SQG quotients. Predictive abilities of SQGs generally matched their narrative intent when outcomes of multiple toxicity tests were considered, and were consistent with North American data. Functionally equivalent SQGs gave comparable results (except where developed for single chemical classes), indicating that predictive abilities were primarily influenced by sensitivities of test species and/or the bioavailability of contaminants.