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Excessive accumulation of heavy metal(loid)s in agricultural environment usually originates from anthropogenic activities. Both large diversities of emission sources and complexity of plant accumulation challenge the understanding of the site-specific effects of emission sources on heavy metal(loid)s in wheat grains. Herein, both soil samples and wheat grain samples (n = 80) were collected from the farmland of Jiyuan City, China. Soil and grain burdens of heavy metal(loid)s were determined by inductively coupled plasma mass spectrometry (ICP-MS) and/or X-ray fluorescence spectrometry (XRF). The quotients (Q) were developed to indicate relative impacts of industrial plants and traffic to soil sites. Principal component analysis-absolute principal component scores-multivariate linear regression (PCA-APCS-MLR) analysis was conducted to reveal the source contributions to heavy metal(loid)s in grains, considering Q values, soil, and wheat grain data. Results showed that contributions of main sources and factors drastically varied with soil sites, and usually overlapped to different extents. For grain Cd and grain Pb, natural soil silicate (0.066/0.104 mg/kg) and iron-bearing minerals (- 0.044/ - 0.174 mg/kg) contributed to high extents, while metal smelting activities (0.018/0.019 mg/kg) and agronomic activities (- 0.017/ - 0.019 mg/kg) unexpectedly posed low or moderate contributions. The pH-mediated availability of soil Cd (0.035 mg/kg) and the sand-dust weather (0.028 mg/kg) also made considerable contributions to grain Cd. For grain As, both natural soil iron-bearing (- 0.048 mg/kg) and silicate minerals (- 0.013 mg/kg) made negative contributions. The results benefit to the decision-making of pollution remediation of farmland soils in the regional scales.

A variety of semi-volatile banned pesticides (SVBPs) are ubiquitous in soils of mid-latitude regions. SVBPs undertake complicated soil-gas exchange processes in mid-latitude regions, challenging the understanding of source or sink roles of soils for the semi-volatile contaminants. Herein, we develop structural equation models (SEMs) to unveil source or sink roles of mid-latitude soils (Liaoning, China) in winter and summer for 12 SVBPs (7 organochlorine and 5 organophosphorus pesticides). The 12 SVBPs exhibit different distribution patterns in soils, dependent of sampling seasons, soil characteristics, topographic/climate conditions of soil sites and chemical properties of compounds. SEM Model I (winter) and Model II (summer) reveal the distribution patterns of SVBPs in soils over season changes, indicating sink-source switches of soils for SVBPS from winter to summer. In winter, soil is a sink of 12 SVBPs in the study area, associated with the inputs of SVBPs in soils by air-particulate partition and dry depositions. However, in summer, soil is mainly a source of the same contaminants, mainly through the volatilization and leaching of SVBPs in soils. The sink-source switches of soils for SVBPs are usually dependent of chemical properties of compounds to higher extents than soil characteristics and topographic/climate conditions of soil sites, though these parameters pose different influences in winter and summer. It has been revealed that soil acts as a sink of SVBPs in winter, associated with the inputs of SVBPs in soils by air-particulate partition and dry depositions, whereas soil acts as a source of SVBPs in summer, mainly through the volatilization and leaching of SVBPs in soils. This finding may provide new insights into the unique distribution patterns of SVBPs in soils in mid-latitude regions.

Because of the rigid crystalline structure and recalcitrant components, maize straw returned is slowly decomposed in soils. Straw residues are substantially accumulated in soils and pose detrimental impacts to crop plantation. Here we report the pretreatments of urea and NaOH (USH) to enhance maize straw decomposition in the field. The USH reagents interacted synergistically to destruct straw, mainly through breaking the rigid hydrogen bonding network and chemically hydrolyzing recalcitrant lignin. The synergy was evident for the USH reagents containing 6-8% urea and 0.1-1% NaOH under various temperature conditions (-20 °C to 25 °C). The USH (7%/0.1%) pretreatment resulted in notable enhancement (37%) of straw decomposition in the field within 6 months, superior to current biological-based treatments (6-28%). Moreover, this pretreatment posed no influence on the adsorption of straw residues collected at the early stage of decomposition (27 days) toward five commonly used herbicides. Those straw residues collected on 67 days and later exhibited high adsorption capacity, indicated by 0.5- to 4-folded increases in K

A compact photoneutron source (PNS), based on an electron LINAC was designed and constructed to provide required experimental nuclear data for Thorium Molten Salt Reactor (TMSR). All devices including the LINAC, the neutron production target and the detector systems were arranged in a shared hall, leading to a high background of neutron and γ-ray. The necessary shielding design was made to reduce the backgrounds. A series of preliminary measurements of total cross section in thermal neutron energy region for some key nuclides of TMSR, such as 232Th and 7Li, have been performed at this PNS. It was found, however, that additional shielding needs to be constructed to further reduce the neutron and γ-ray backgrounds. MCNP is a major tool for the background shielding design since it has the calculation capability for a coupled neutron-photon-electron transport problem. A two-step subsection simulation based on MCNP involving with variance reduction techniques (Sub-Var method) was performed to provide required flux and spectrum calculation for the new background shielding design. Based on the simulated results, a new local shielding was designed and constructed, which can reduce the thermal neutron background by three orders of magnitude and the γ-ray background by two orders of magnitude. The neutron flux and energy spectrum were measured under the new shielding condition and compared with the simulated ones, showing a good agreement with each other in the thermal energy region. Therefore, a significant improved shielding for the PNS is achieved, which is expected to provide a required assurance for the future measurements of neutron cross section at the PNS.

Cadmium (Cd) and other heavy metals usually coexist in soils. Effects of coexisting heavy metals on the accumulation and transfer of Cd in field soils by wheat remain poorly understood. Here we revealed changeable effects of coexisting Pb, Zn and Cu on the Cd transfer from soils to wheat grains. Soil burdens of Cd were found to exhibit positive correlations (r = 0.459–0.946) with those of coexisting Pb, Zn and Cu (particularly Pb). Effects of three coexisting metals on to the uptake of Cd by wheat varied in the directions and/or extents with types of metals and transfer processes of Cd. Coexisting Zn inhibited the uptake of Cd by wheat grains to higher extent than Pb and Cu. Soil Zn, along with soil Cd, soil pH and soil Ca, was used to construct the predictive model of grain Cd (R2 = 0.868). External verifications of the model on 572 datasets of large representation performed well. The predictive accuracy was about 54%, 73% and 89% for a factor of 1, 2 and 5 above and below the ideal fit, respectively. This finding has practical interest in risk assessments and remediation measures of Cd-contaminated soil sites in regional scales.

Nano zero-valent iron (nZVI) materials usually have low selectivity in water toward target contaminants (e.g., p-nitrophenol) and nontarget water constituents (e.g., nitrates and dissolved organic matter-DOM). Here we prepared the selective nZVI entrapped in the matrix of cyclodextrin polymer (CDP), using in situ impregnation and aqueous KBH4 reduction of FeCl3 in the matrix of CDP. The nZVI-CDP composites feature the network structure of CDP with mainly 40–80 nm nZVI particles entrapped in the network and 300 nm iron particles coated on the network surface. nZVI entrapped displays high stability and selective CDP facilitates the access of p-nitrophenol to nZVI, both accounting for the high selectivity of the composites. Chemical degradation of the nZVI materials, combined with adsorption, contributed to the p-nitrophenol removal. The nZVI materials usually exhibited similar or higher p-nitrophenol removal at different levels of nitrates, DOM or sulfides. Column experiments showed that the nZVI materials completely decontaminated 63 column volumes of groundwater containing p-nitrophenol, 6-fold higher than mixed nZVI and CDP. The nZVI materials were estimated to have potential performance duration of averaging 109 d, indicating the long-term performance in groundwater.

Cadmium (Cd) is one of the most toxic substances released in the environment. Cd-contaminated soils usually have a large pool of bioavailable Cd species and lead to excessive Cd accumulation in planted cereal crops. Treatment methods for stable immobilization of Cd in soils are desirable. Here we reported that facile combinations of thiosulfate (STS) and zerovalent iron (ZVI) reinforced Cd immobilization in soils and reduced Cd accumulation in wheat. STS mildly activated Cd in soils through the formation of soluble Cd(S2O3)x complexes, whereas intermediates of STS (e.g., sulfate and sulfides) and ZVI synergically facilitated immobilization of Cd in soils. The synergy was ascribed to the facilitated formation of FeOOH with high Cd-binding affinity and formation of stable sulfate-Cd-FeOOH complexes and poorly available CdSx. STS-ZVI treatments increased residual Cd in soils by 101–123% and decreased Cd accumulation in wheat shoots by 13–68%, depending on chemical compositions and doses of binary reagents. Field applications of STS and ZVI (0.06–0.11 kg/m2) demonstrated 24–39% reductions of grain Cd.

Predicting plant cuticle-water partition coefficients (Kcw) and understanding the partition mechanisms are crucial to assess environmental fate and risk of organic pollutants. Up to now, experimental Kcw values are determined for only hundreds of compounds because of high experimental cost. For this reason, computational models, which can predict Kcw values based on chemical structures, are promising approaches to evaluate new compounds. In this study, a large dataset consisting of 279 logKcw values for 125 unique compounds were collected and curated. A poly-parameter linear free energy relationship (pp-LFER) model was developed with stepwise multiple linear regression based on this dataset. The resulted pp-LFER model has good predictability and robustness as indicated by determination coefficient (R2adj,tra) of 0.93, bootstrapping coefficient (Q2BOOT) of 0.92, external validation coefficient (Q2ext) of 0.94 and root mean square error of 0.52 log units. Contribution analysis of different interactions indicated that dispersion and hydrophobic interactions have the highest positive contribution (56%) to increase the partition of pollutants onto plant cuticles. In addition, for organic pollutions containing benzene ring (13-31%), double bond (9-17%) or nitrogen-containing heterocycles (9-17%), π/n-electron pairs interactions exhibit obvious positive contributions to logKcw. In conclusion, the proposed pp-LFER model is beneficial for predicting logKcw of potential organic pollutants directly from their molecular structures.

Thorium-fueled Pebble Bed Fluoride salt-cooled High-temperature Reactor (PB-TFHR) is a newly developed reactor concept featuring the technology of High Temperature gas-cooled Reactor (HTR) and the molten salt cooling for thorium-based fuels. To attain a deep burnup with enough negative temperature coefficient of reactivity (TCR), a systematic study for the graphite-to-heavy metal ratio (C/HM) from 66 to 800 and the 233U-to-HM ratio (233U/HM) from 5.0% to 20.0% are carried out. Neutronics characteristics, including the effective multiplication factor (keff), the TCR and the conversion ratio (CR) are analyzed in terms of neutron usage, core safety and burnup. The results show that the fuel pebble with a higher 233U/HM owns a wider range of under-moderated area, which is favorable to improve TCR. Moreover, a strongly negative TCR is obtained by optimizing the C/HM and 233U/HM ratios. In order to evaluate the 233U saving for thorium based fuel, the burnup per fissile mass (Bu) is introduced. Bu can be improved through reducing C/HM, and it increases firstly and then achieves saturation as 233U/HM increases. A burnup level of 122 GWd/tHM can be achieved for the recommended pebble design with 233U/HM of about 12.5% and C/HM of about 124. With the optimized design, an improved TCR can be obtained with a value of about −2.77 pcm/K, which is much more superior to our previous work.

Information about bioaccumulation and tissue distribution of antibiotics in wild marine fish is still limited. In the present study, tissue levels, bioaccumulation and distribution patterns of 9 sulfonamide (SA), trimethoprim (TMP), 5 fluoroquinolone (FQ), and 4 macrolide (ML) antibiotics were investigated in gill, muscle, kidney, and liver tissues of seven wild fish species collected from Laizhou Bay, North China in 2016. All the 19 antibiotics were detected in these fish tissues with the total concentrations ranging from 22ng/g dry weight (dw) to 500ng/g dw. The mean values of logarithm bioaccumulation factors (BAFs) in the gills, muscles, kidneys, and livers ranged from 2.2 to 4.8, 1.9 to 4.0, 2.5 to 4.9, and 2.5 to 5.4, respectively. Log BAFs of antibiotics in these tissues significantly increased (r=0.61-0.77, p

Molten Salt Reactor (MSR) with Th-233U fuel cycle attracts more and more attention with its excellent performance such as desirable breeding capacity, low waste production and high inherent safety. Considering the fact that there is no available 233U in the nature, it is necessary to analyze the fuel transition from enriched 235U/Th to 233U/Th and then give a flexible transition scenario for a graphite-moderated MSR. By employing an in-house developed tool which is based on SCALE6.1, two scenarios, a Breeding and Burning (B&B) scenario and a Pre-breeding scenario, are studied. The evolution of the inventories of main nuclides, net 233U production and isothermal temperature coefficient are presented and discussed in the B&B scenario. It is found that the fuel transition can be achieved smoothly by using enriched uranium with greater than 40% concentration of 235U. The fuel transition can still be accomplished with 20% enriched uranium but takes a long double time of about 79 years. Meanwhile, we perform an analysis of the Pre-breeding scenario and conclude that it is efficient to produce 233U and the double time ranges from 2.07 years for the 10-day reprocessing to 10.7 years for the 180-day reprocessing. A comparison of these two scenarios is conducted, which indicates that the B&B scenario is more favorable than the Pre-breeding scenario from the aspect of resource utilization efficiency. Finally, a combined three-stage program for developing Th-based MSRs is proposed.

Despite the importance of bioavailability for organic chemical bioaccumulation by terrestrial and benthic invertebrates, the principles of bioavailability for organic chemical bioaccumulation remain poorly understood. Here we use large-scale databases with contrasting geographic, compound and organism coverage (from 925 sites, 446 compounds and 184 invertebrate species), and report that bioavailability for organic chemical bioaccumulation follows the power law. It represents that the internal concentration of organic chemicals is the composite power function of the lipid fraction of invertebrates, bulk site concentration of compounds, and organic carbon content of soils/sediments. This law directly links environmental exposures and body burdens of organic chemicals in contaminated sites, and provides a method for enabling case-specific risk assessments of a vast number of organic chemicals and contaminated sites. Our findings may pave the way for translating bioavailability knowledge into risk-oriented regulation of organic chemicals and contaminated sites.

Compared with nanoscale zero-valent iron particles (nZVI), sulfidated zero-valent iron nanoparticles (S-nZVI) exhibit higher reactivity and selectivity towards the remediation of halogenated organic pollutants such as trichloroethene (TCE). However, traditional methods of preparing S-nZVI are not safe and environmentally friendly to some degree. In this study, we developed a biological precipitation method to prepare S-nZVI, in which sulfate-reducing bacteria (SRB) played an important role for the in situ formation of ferrous disulfide on the surface of nZVI. The results show that the obtained sulfidated nZVI particles (BP-S-nZVI) exhibit excellent performance in TCE degradation, and the first-order rate coefficient (Kobs) and the efficiency of electron utilization were up to (1.66 ± 0.1)× 10-1 h-1 and 85%, respectively. Moreover, zero-valent iron utilization efficiency of BP-S-nZVI reached 95%. Meanwhile, the particles were well characterized and the mechanism for enhanced reactivity was explored. The prominent advantage of this novel method is that the harmful chemical sulfidating agents such as dithionite (S2O42−) and sodium sulfide (Na2S) are not required, making the preparation process more environmental-friendly, green and sustainable.

Outspread straw return practice leads to accumulation of structurally diverse organic materials in soils, including raw straw and straw residues. This practice provides a supplementary source of organic sorbents for compounds released into soils. However, effects of accumulated straw materials on sorption of compounds in soils remain poorly understood. Here we report that straw materials accumulated in soils display changing chemical structure and properties during decomposition, the majority of which distribute in exponential growth or decay manners with decomposition extents of materials. Sorption of straw materials toward 40 commonly used pesticides and antibiotics takes a compromise of decreasing crystalline index and increasing water absorption capacity of the sorbent materials during decomposition. This tradeoff in sorption leads to case-specific sorption trends of organic compounds in soils with straw return practice, following a composite linear sorption model of mixed soils and straw materials. The predictive model shows that relatively hydrophobic, hydrogen bond acceptor-rich chemicals (about 22.5% of the 40 compounds) display decreasing sorption capacity in organic matter-rich and/or relatively acidic soils with straw return. This finding may contradict the notion that crop straw return usually increases sorption and decreases leaching of compounds in soils.

Cross-linked cyclodextrin polymer (CDP) materials have high sorption capacity and selectivity toward organic contaminants in water, depending on the polymeric network. The network structure is difficult to predict, due to the exothermic nature of polymerization reactions for material preparation. Here, we prepared CDP composite materials with rigid bulk structure and flexible polymeric network through facile KMnO4 oxidation treatments of CDPs. These materials featured regular embedment of nanorod MnO2 particles in the polymeric matrix and had mechanical stability, associated with the oxidation of short chains of the polymeric network. The structure and properties of materials (e.g., the cross-linking degree, pore volume and CD unit content) were regulated by KMnO4 dosage, the majority of which were linearly increased or decreased with increasing oxidant doses. The cross-linking degree, pore volume and CD unit type/content of materials were found to pose important impacts on sorption capacity of CDP materials toward compounds. These property alterations accounted for a compromise of amounts and accessibility of sorption sites, consistent with the important sequence of sorption mechanisms of CDP materials (association complexation ≥ network meshing ≫ inclusion complexation). This compromise has practical interest in the preparation of CDP materials with more useful properties of sorbents. Reuse experiments of chosen CDP materials showed high removal efficiency and stability of materials toward pesticides in water. Removal efficiency of reused materials toward pesticides in water was increased by an average of 22.5%.

Little information is available about the bioaccumulation and biomagnification of antibiotics in marine food webs. Here we investigate the levels and trophic transfer of 9 sulfonamide (SA), 5 fluoroquinolone (FQ), and 4 macrolide (ML) antibiotics, as well as trimethoprim in nine invertebrate and ten fish species collected from a marine food web in Laizhou Bay, North China in 2014 and 2015. All the antibiotics were detected in the marine organisms, with SAs and FQs being the most abundant antibiotics. Benthic fish accumulated more SAs than invertebrates and pelagic fish, while invertebrates exhibited higher FQ levels than fish. Generally, SAs and trimethoprim biomagnified in the food web, while the FQs and MLs were biodiluted. Trophic magnification factors (TMF) were 1.2 – 3.9 for SAs and trimethoprim, 0.3 – 1.0 for FQs and MLs. Limited biotransformation and relatively high assimilation efficiencies are the likely reasons for the biomagnification of SAs. The pH dependent distribution coefficients (logD) but not the lipophilicity (logKOW) of SAs and FQs had a significant correlation (r = 0.73; p < 0.05) with their TMFs. Although the calculated estimated daily intakes (EDI) for antibiotics suggest that consumption of seafood from Laizhou Bay is not associated with significant human health risks, this study provides important insights into the guidance of risk management of antibiotics.

It is essential to monitor pesticides in the environment to help ensure water and soil quality. The diffusive gradients in thin-films (DGT) technique can measure quantitative in situ labile (available) concentrations of chemicals in water, soil, and sediments. This study describes the systematic development of the DGT technique for nine current pesticides, selected to be representative of different classes with a wide range of properties, with two types of resins (HLB (hydrophilic-lipophilic-balanced) and XAD 18) as binding layer materials. The masses of pesticides accumulated by DGT devices were proportional to the deployment time and in inverse proportion to the thickness of the diffusive layer, in line with DGT theoretical predictions. DGT with both resin gels were tested in the laboratory for the effects of typical environmental factors on the DGT measurements. DGT performance was independent of the following: pH in the range of 4.7-8.2; dissolved organic matter concentrations

Persulfate-based chemical oxidation of petroleum hydrocarbons (TPHs) in soils usually varies drastically with soil sites. Complex effects of soil components on persulfate oxidation of TPHs remains poorly understood, impeding the understanding of persulfate oxidation in practical systems. Here we provided empirical evidence for the interrelated effects of natural soils components and target TPHs on persulfate oxidation of TPHs. Inputs of TPHs led to notable alterations of organic matter, minerals and pH of soils, which in turn influenced distributions and availability of TPHs in soils. These soil/TPH properties and oxidant dose constituted five interrelated terms that were used to develop a predictive model of persulfate oxidation of TPHs. Such interrelation accounted for ilmenite-base coupling activation of persulfate oxidation, Fe/Mn mineral activation of persulfate oxidation, chemical oxidant demand of soils, mass transfer-reactivity limiting of TPHs, and applicable parameters of persulfate oxidation, respectively. The interrelation-based model of persulfate oxidation of TPHs displayed high predictive accuracy of 43% for a factor of 0.3 above and below the ideal fit, despite large differences in contaminated sites and applicable parameters. This finding may have practical interests in the optimization of persulfate oxidation.

Micro Reactors with power below 10 MW can offer many benefits for ocean or space exploration with their favorable characteristics, such as low specific mass, long-lasting life, highly flexible power supply and strong environment adaptability. The heat pipe cooled micro molten salt reactor (micro-MSR) which is an innovative concept combining molten salt reactor and heat pipe technology, is proposed in this work and furthermore, a 50 kWth version of micro-MSR is designed. The main neutronic characteristics, including the neutron spectrum, reactivity control with control drums inserted in the radial reflector, temperature reactivity coefficient (TRC), neutron flux, power deposition, and neutron balance are provided and discussed, respectively. The diameter and height of the designed core are about 0.69 m and 0.96 m, respectively, and the total mass of the core is merely about 1.3 tons, which is desirable for application in space, ocean and remote, off-grid locations. Meanwhile, an analysis of reactivity worth and interference effects of control drums are performed, which indicates that the reactivity control can be achieved by using the control drums. The results of TRC that governs the inherent safety of the micro-MSR demonstrate the feasibility of a self-actuated shutdown mechanism owing to a sufficiently negative TRC of about −13.91 pcm/K. A design of radiation shield mainly for effective protection of the electronic components is provided and it is found that a 47 cm thickness of shield can limit the neutron and gamma dose to the permissible range. Additionally, the performance of the heat pipes (HPs) in the core is evaluated, and the results indicate that the heat transfer capacity of the HP is great enough to ensure the cooling of the fuel salt in the core.

The unique feature of molten salt reactor (MSR) is that heavy metal fuel and fission products can be dissolved in a molten fluoride salt to form a eutectic mixture which acts as both fuel and coolant. The fission energy from fissile fuel is released immediately into the fuel salt in the core, and the delayed neutron precursors (DNP) have a loss due to fuel circulation in the primary loop, which both make MSR be characterized by the strong interplay between the neutronics and thermal hydraulics (TH) and imply that the software developed for traditional solid-fueled reactors is not applicable to MSR. In this study, a new coupled neutronics and TH code named TMSR3D is developed for evaluating the steady-state characteristics of liquid-fueled MSR. In this code, the fourth order standard nodal expansion method (NEM) is implemented to solve the neutron diffusion equations, and the parallel multi-channel model is adopted to take into account the feedbacks of local temperature to group constants. Besides, a convection term is introduced into the traditional balance equations for DNP to consider the influence of fuel salt flow. Some experiment data of Molten Salt Reactor Experiment (MSRE) are chosen to verify the code, and the core characteristics including the distributions of neutron fluxes, DNP and temperature under the rated condition are simulated and discussed. Furthermore, the impacts of the inlet mass flow rate, inlet fuel temperature and the fuel salt residence time out of the core are analyzed in detail. The numerical results indicate that the TMSR3D code can provide a reliable description of the neutronics-TH coupling phenomena and of the steady state analysis for graphite-moderated channel-type MSRs.

General Atomics (GA) is developing the Energy Multiplier Module (EM2) which is a compact gas-cooled fast reactor as one of candidates of the Generation-IV nuclear energy systems. In the EM2 core, low enriched uranium is used as igniting fuel and depleted uranium is used for converting and burning. It indicates that EM2 can maintain critical operation for more than 30 years without refueling. To further study the Th-U fuel cycle performance in the EM2, two kinds of start-up strategies with Th-U (Th + U-233) and semi Th-U (Th + enriched U-235) are evaluated. Neutronics characteristics, such as the effective multiplicity factor (k(eff)) and conversion ratio (CR) are analyzed from neutron usage point of view. The simulated results for the two kinds of fuels are compared with the U-Pu fuel from the design of GA. The analysis gives an insight into the pros and cons of U-Pu and Th-U fuel cycles in terms of the breeding capability and the discharged radio-toxicity. The breeding performance of the second generation EM2 is also presented and compared with that of the first generation EM2. It indicates that the multi-generation EM2 can deepen the burnup and reduce the waste management pressure for each kind of fuel loading strategy. (C) 2015 Elsevier Ltd. All rights reserved.

In a liquid-fueled molten salt reactor (MSR), the fuel salt acts as both fuel and coolant, and the fission energy is released into the fuel salt immediately. The delayed neutron precursors drift through the graphite channels in the core and the primary loop during operation. Therefore, the dynamics for a MSR is characterized by the strong interplay between the neutronics and thermal hydraulics, which is significantly different from that of a solid-fueled reactor, such as PWR. In this study, a dynamic analysis for a graphite moderated, fluoride based, liquid-fueled molten salt reactor with a power of 2 MWth (TMSR-LF) is carried out based on a coupled neutronics/thermal hydraulics code named TMSR-2D. The steady-state characteristics including the distributions of flow field, temperature and neutron fluxes, and effective delayed neutron fraction under different fuel flow rates, transients perturbed by fuel pump start-up and coast-down, overcooling and overheating of inlet fuel and reactivity insertion are simulated and analyzed. The numerical results indicate that the dynamic behavior of TMSR-LF is acceptable in the aspect of reactor safety. Furthermore, the dynamic analysis offers valuable information for future construction and operation of this experimental reactor.

Mariculture activities and river inputs lead to coastal seawaters with DOM levels that are comparable to or even higher than those in terrestrial water bodies. However, effects of seawater DOM, and especially of DOM occurring in areas impacted by mariculture, on photodegradation of organic micropollutants, are largely unknown. In this study, simulated sunlight irradiation experiments were performed to probe the effects of DOM extracted from mariculture impacted seawaters and from offshore areas, on photodegradation of three sulfonamide antibiotics (SAs). Results show that the SAs are transformed mainly by indirect photodegradation induced by triplet excited DOM (3DOM*). Compared with DOM from the more pristine coastal waters, the DOM from mariculture impacted areas undergoes less photobleaching, contains higher percentage of humic-like materials and higher proportions of aromatic and carbonyl structures. Thus, the DOM from mariculture areas exhibits higher rates of light absorption, higher formation quantum yields of 3DOM*, higher 3DOM* steady-state concentrations and higher reactivity on photodegradation of the SAs. Photochemistry of the seawater DOM is different from that reported for freshwater lake DOM. This study highlights the importance of probing the effects of DOM from coastal seawaters on photodegradation of organic micropollutants since coastal seawaters are sinks of many aquatic pollutants.

The removal of aqueous micropollutants remains challenging because of the interference of natural water constituents that are typically 3-9 orders of magnitude more concentrated. Cyclodextrins, which feature molecular recognition and are widely applied in separation and catalysis, are promising materials in the development of pollutant treatment technologies. Here, we described the facile integration of cyclodextrin polymer (CDP) adsorption and KMnO4 oxidation for recyclable capture and destruction of aqueous micropollutants (i.e., antibiotics and TBBPA). CDP exhibited adsorption efficiencies of 0.81-88% and 0.81-94% toward 14 pollutants at 50.0 ng/L and 50.0 μg/L, respectively, at a solid-to-liquid ratio of 1:1250. The presence of simulated or natural water constituents (e.g., Mg(2+), Ca(2+), DOC, and a combination thereof) did not decrease the adsorption potential of CDP toward these pollutants because the pollutants, based on molecular specificity, were entrapped in the CD cavity. Subsequent KMnO4 oxidation completely degraded the retained pollutants, demonstrating that the pollutants could be broken down in the cavity. Pristine CDP was rearranged into the structurally loose composites that featured a porous CDP architecture with uniform embedment of δ-MnO2 nanoparticles and different adsorption efficiencies. δ-MnO2 loading was a linear function of the number of times the integrated procedure was repeated, underlying the accurate control of CDP recycling. Thus, this approach may represent a new method for the removal of aqueous micropollutants.

Molten salt reactor (MSR) has fascinating features: inherent safety, no fuel fabrication, online fuel reprocessing, etc. However, the graphite moderated MSR may present positive feedback coefficient which has severe implications for the transient behavior during operation. In this paper, the feedback coefficient and the breeding ratio are optimized based on the fuel-to-graphite ratio variation for a thorium based MSR (TMSR). A certain thermal core with negative feedback coefficient and relative high initial breeding ratio is chosen for the reprocessing scheme analysis. The breeding performances for the TMSR under different online fuel reprocessing efficiencies and frequencies are evaluated and compared with other MSR concepts. The results indicate that the thermal TMSR can get a breeding ratio greater than 1.0 with appropriate reprocessing scheme. The low fissile inventory in thermal TMSR leads to a short doubling time and low transuranic (TRU) inventory. The lifetime of graphite used for the TMSR is also discussed. (C) 2014 Elsevier B.V. All rights reserved.

Chemical forms-dependent binding interactions between phenolic compounds and human transthyretin (hTTR) have been elaborated previously. However, it is not known whether the binding interactions between ionizable halogenated alphatic compounds and hTTR also have the same manner. In this study, poly-/perfluorinated chemicals (PFCs) were selected as model compounds and molecular dynamic simulation was performed to investigate the binding mechanisms between PFCs and hTTR. Results show the binding interactions between the halogenated aliphatic compounds and hTTR are related to the chemical forms. The ionized groups of PFCs can form electrostatic interactions with the -NH+3 groups of Lys 15 residues in hTTR and form hydrogen bonds with the residues of hTTR. By analyzing the molecular orbital energies of PFCs, we also found that the anionic groups (nucleophile) in PFCs could form electron donor - acceptor interactions with the -NH+3 groups (electrophile) in Lys 15. The aforementioned orientational interactions make the ionized groups of the PFCs point toward the entry port of the binding site. The roles of fluorine atoms in the binding interactions were also explored. The fluorine atoms can influence the binding interactions via inductive effects. Appropriate molecular descriptors were selected to characterize these interactions, and two quantitative structure-activity relationship models were developed.

Thyroid disrupting chemicals (TDCs) can compete for the binding sites of transport proteins with thyroid hormones (THs) and alter the homeostasis of THs. The halogen moieties in TDCs play key role in determining the interactions between TDCs and transthyretin (TTR). Herein, the effects of halogenation on the binding interaction was investigated by analyzing the TTR crystal structures, the TDCs-TTR complex from molecular simulation, and the relative competing potency of a chemical with T 4 binding to hTTR (log RP ). We found that the halogen moieties in TDCs can affect the binding interactions by forming halogen bonds and halogen-hydrogen bonds with TTR and through inductive effects and hydrophobic effects. The halogen bonds (mainly halogen-oxygen bonds) and halogen-hydrogen bonds enhance the binding between organic halogenated compounds and TTR. Besides, for the halogenated phenolic compounds, the inductive effect is a main factor determining the log RP values. The hydrophobic effect is a critical factor governing the interactions between non-ionizable compounds (e.g. polybrominated diphenyl ethers) and TTR.

While many cyclodextrin-based applications have been developed to assess or enhance bioavailability of organic pollutants, the choice of cyclodextrin (CD) is largely empirical, with little consideration of pollutant diversity and environmental matrix effects. This study aimed at developing a mathematical model for quantifying CD alteration of bioavailability of organic pollutants. Cyclodextrin appears to have multiple effects, together contributing to its bioavailability-enhancing property. Cyclodextrin is adsorbed onto the adsorbent matrix to different extents. The adsorbed CD is capable of sequestrating organic pollutants, highlighting the role of a pseudophase similar to solid environmental matrix. Aqueous CD can reduce adsorption of organic pollutants via inclusion complexation. The two effects cancel each other to a certain degree, which determines the levels of organic pollutants dissolved (comprising freely dissolved and CD-included forms). Additionally, the CD-included form is nearly identical in biological activity to the free form. A mathematical model of one variable (i.e., CD concentration) was derived to quantify effects of CD on the bioavailability of organic pollutants. Model analysis indicates that alteration of bioavailability of organic pollutants by CD depends on both CD (type and level) and environmental matrix. The selection of CD type and amendment level for a given application may be predicted by the model.

Hydroxylated polybrominated diphenyl ethers (HO-PBDEs) pose potential ecological risks due to their endocrine disrupting effects and extensive sources. It is of great importance to know their environmental transformation for the purpose of ecological risk assessment. Photodegradation is an important transformation pathway of HO-PBDEs. As HO-PBDEs ionize in natural waters, the photochemical reactivities of both neutral and anionic HO-PBDEs need to be unveiled. In this study, six HO-PBDEs were selected as model compounds. Their direct photolysis rate constants (k(d)), quantum yields (Φ), light absorptions (A), second-order reaction rate constants with (1)O(2) (k(1O2)) and (·)OH (k(OH)) at different pH were determined, as well as these parameters for the neutral and anionic HO-PBDEs. The k(d), Φ, A, k(1O2) and k(OH) for the anions are much higher than those for the neutral molecules and vary with the bromination degree. Molecular parameters computed with the density functional theory (DFT) were employed to construct structure-reactivity equations. The ether bond strength, the frontier molecular orbital energy and the charge distribution were found to be the intrinsic structural characters governing the photochemical reactivities. The half-lives range from 0.7 to 60.1h for the photodegradation including the direct photolysis and the reactions with (1)O(2) and ()OH in surface waters at 45°N latitude under the continuous solar irradiation of sunny noon on 15 July. Direct photolysis is the dominant pathway. The photochemical reactivities of other HO-PBDEs at a given pH can also be estimated based on the structure-reactivity equations, which is important for the ecological risk assessment of HO-PBDEs.

A rational screening of cyclodextrin-based polymer (CDP), in terms of the relationship between adsorption potential and adsorbent-adsorbate, was investigated to adsorb and separate pesticides from water. Seven spherical porous CDPs were prepared with onefold or composite cyclodextrin(s) as complex and epichlorohydrin as cross-linking reagent. The adsorption kinetics and isotherms of the polymers toward a mixture of ten distinct pesticides clearly demonstrate that the adsorbents with a homogeneous open network structure can absorb pesticides via multiple adsorption interactions such as CD inclusion, loading into swelling water and physical adsorption on network. The multivariate regression analysis distinguishes the quantitative contributions of polymer properties to its adsorption potential, among which CD content, swelling capacity and pore size appear to be major influencing factors. Consequently, a facile mixture of three CDPs (i.e., β-CDP, RM-CDP and HP-CDP) was screened to obtain above prerequisite properties. The multiplex polymer could superiorly separate the pesticides at environmentally relevant levels from water.

Transformation products usually differ in environmental and toxicological properties compared to the parent contaminants, thus causing potential and unknown environmental risks. To elucidate differential chiral recognition of the aryloxypropanoate herbicide quizalofop ethyl (QE) and its primary product (quizalofop acid, QA), their enantiomeric separation and toxicological impacts to two freshwater algae were investigated. Addition of trace water (0.02-0.08%, v/v) to the mobile phase selectively affected retention of analyte and induced simultaneous enantio-separation for the two compounds with intrinsical water-specific resolution mechanisms, although they both possessed a chiral center in the 2-position of propionates. In algal suspensions, QE was rapidly degraded to produce the acid metabolite (QA), and the product further declined, whereas a reduction of QA as starting compound did not occur. Uptake and/or transformation of QE and QA were found a lack of enantioselectivity and isomer inversion, while cellular membrane permeability, membrane potential and algal growth showed enantioselectivity to different extents. These results suggested the presence of receptor chirality that was involved in the toxicological processes but invalid for uptake and transformation. Therefore, quizalofop acid, identified as environmentally relevant contaminant associated with application of the herbicide, participated in the toxicological processes of the parent compound, and exhibited distinct toxicological and chromatographic retention properties.

For ecological risk assessment of the large and ever-increasing number of chemical pollutants, it is of importance to develop computational methods to screen or predict their environmental photodegradation behavior. This study developed a computational method based on the density functional theory (DFT) to predict and evaluate the photodegradation behavior and effects of water constituents, taking a sunscreen and personal care product 2-phenylbenzimidazole-5-sulfonic acid (PBSA) as a model compound. Energy and electron transfer reactions of excited state PBSA (PBSA*) with (3)O(2) and water constituents were evaluated. The computational results indicated that PBSA* could photogenerate (1)O(2) and O(2)(-)·, triplet excited state humic/fulvic acid analogs could not photosensitize the degradation, and the anions (Cl(-), Br(-), and HCO(3)(-)) could not quench PBSA* or its radical cation chemically. Experiments employing simulated sunlight confirmed that PBSA photodegraded via the direct and self-sensitization mechanism involving O(2)(-)·. The photodegradation was pH-dependent. The direct and self-sensitized photodegradation was inhibited by fulvic acid. The main photodegradation products were identified, and the pathways were clarified. These results indicate that the DFT-based computational method can be employed to assess the environmental photochemical fate of organic pollutants.

Fluoroquinolone antibiotics (FQs) are frequently detected as emerging pollutants in aqueous environments. In this study, kinetics, influencing factors and mechanisms on the photodegradation of gatifloxacin, a representative FQ, were investigated. The photo-degradation follows the pseudo-first-order kinetics. Gatifloxacin photodegrades with a quantum yield of (5.94 ± 0.95) × 10−3 in pure water and undergoes direct photolysis as well as self-sensitized photodegradation. The FQ photodegrades slower in freshwater and seawater than in pure water, which is attributed to the integrative effects of pH and the aqueous dissolved matter (e.g., humic acids and NO3−) on the photodegradation. A toxicity test using Vibrio fischeri revealed the formation of hazardous photoproducts.

The separation of chiral transformation products greatly complements the understanding of the stereochemistry of chiral pollutants. In this study, direct enantiomeric resolution of metalaxyl and its main degradation product metalaxyl acid, often co-occurring in the environment, was carried out in normal-phase high-performance liquid chromatography with a Chiralcel OJ-H column. (R)-Metalaxyl acid and (S)-metalaxyl, which were almost parallel bonding to the chiral stationary phase, tended to separate, started to overlap, coeluted, and separated again with subtle changes of the mobile phase consisting of n-hexane, 2-propanol, acetic acid, and trace water. Their competition above hampered an acceptable direct separation in fresh mobile phases. Aged mobile phases with a storage period of 3-5 days, however, significantly improved their separation, in which trace water from moisture air diffusion was found to play a major role. Trace water differentially affected peak width and retention times and then induced enhanced peak separation, confirmed by deliberate addition of water to fresh mobile phases. Furthermore, none of the studied factors, involving temperature, concomitant analytes, and trace water, could cause changes of the configuration of the chiral stationary phase. Simultaneous enantiomeric separation of both compounds was achieved in aged or fresh mobile phases with adventitious or added water and gave satisfactory peak separation, all with Rs values of more than 1.20 in environmental samples.

The ubiquity of fluoroquinolone antibiotics (FQs) in surface waters urges insights into their fate in the aqueous euphotic zone. In this study, eight FQs (ciprofloxacin, danofloxacin, levofloxacin, sarafloxacin, difloxacin, enrofloxacin, gatifloxacin, and balofloxacin) were exposed to simulated sunlight, and their photodegradation was observed to follow apparent first-order kinetics. Based on the determined photolytic quantum yields, solar photodegradation half-lives for the FQs in pure water and at 45 degrees N latitude were calculated to range from 1.25 min for enrofloxacin to 58.0 min for balofloxacin, suggesting that FQs would intrinsically photodegrade fast in sunlit surface waters. However, we found freshwater and seawater constituents inhibited their photodegradation. The inhibition was further explored by a central composite design using sarafloxacin and gatifloxacin as representatives. Humic acids (HA), Fe(III), NO(3)(-), and HA-Cl(-) interaction inhibited the photodegradation, as they mainly acted as radiation filters and/or scavengers for reactive oxygen species. The photodegradation product identification and ROS scavenging experiments indicated that the FQs underwent both direct photolysis and self-sensitized photo-oxidation via *OH and (1)O(2). Piperazinyl N(4)-dealkylation was primary for N(4)-alkylated FQs, whereas decarboxylation and defluorination were comparatively important for the other FQs. These results are of importance toward the goal of assessing the persistence of FQs in surface waters.

The photoinduced acute toxicity of fourteen anthraquinone derivatives to Daphnia magna was investigated. Whilst in the dark, all of dyes exhibited no observable toxicity at the maximum test concentration used, in the presence of visible light, all of the colorants, with the exception of three nitroanthraquinones, were acutely toxic towards the water flea over a wide range of medium effective concentrations (4.3–4186.7 nmol L−1). Generally, the acute toxicity of the dyes was higher in the presence of full-spectrum simulated solar radiation compared with visible light; in addition, the photoinduced toxicity of the dyes increased with increase in their hydrophobicity. The energy gap between the lowest unoccupied molecular orbital and the highest occupied molecular orbital was found to indicate the relative photoinduced toxicity of the dyes. Time-dependent density functional theory calculations revealed that singlet oxygen and the superoxide anion could be generated through direct energy transfer or autoionization of the excited state of the dyes.

The reaction with hydroxyl radical ( OH) is the most important removal process in the daytime for organic pollutants in the atmosphere, thus the OH reaction rate constants (kOH) are important to assessing the fate of organic pollutants in the troposphere. In this study, experimental data for log kOH of 722 organic chemicals were employed to develop quantitative structure–activity relationships (QSARs) for kOH, applying 22 molecular structural descriptors and partial least squares (PLS) regression. The QSAR development followed the OECD guidelines, with special attention to validation, applicability domain and mechanistic interpretation. For the established model, the leave-many-out cross-validated QCUM2 = 0.865, R2 = 0.878, and RMSE = 0.391 log units, indicating good robustness and predictivity. The predictive capability was also evaluated by external validation with QEXT2 = 0.872. The applicability domain of the model is composed of compounds containing C, H, N, O, S, F, Cl, Br, I, and Si atoms in various functional groups and analyzed by Williams plot. The main molecular structural factors governing kOH are the compactness of the molecule, the molecular ability of donating electrons and the number of halogen atoms in a molecule.

Mixture toxicities were determined for 12 industrial organic chemicals bearing four different modes of toxic action (MOAs) to Vibrio fischeri , to compare the predictability of the integrated fuzzy concentration addition–independent action (IFCA–IA) model and the two-stage prediction (TSP) model. Three mixtures were designed: The first and second mixtures were based on the ratios of each component at the 1% and 50% effect concentrations (EC 1 and EC 50 ), respectively; and the third mixture contained an equimolar ratio of individual components. For the EC 1 , EC 50 and equimolar ratio, prediction errors from the IFCA–IA model at the 50% experimental mixture effects were 0.3%, 6% and 0.6%, respectively; while for the TSP model, the corresponding errors were 2.8%, 19% and 24%, respectively. Thus, the IFCA–IA model performed better than the TSP model. The IFCA–IA model calculated two weight coefficients from the molecular structural descriptors, which weigh the relation between concentration addition (CA) and independent action (IA) through the fuzzy membership functions. Thus, MOAs are not pre-requisites for mixture toxicity prediction by the IFCA–IA approach, implying the practicability of this method in toxicity assessment of mixtures.

Factor analysis model with nonnegative constraints (FA-NNC) and positive matrix factorization (PMF) were successful in source identification of polychlorinated dibenzo- p -dioxins/dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs) in pine ( Cedrus deodara ) needle samples collected from Dalian, China. The source profiles and source contributions derived from the two receptor models were comparable. The results suggested that the main sources of PCDD/Fs were various combustion processes (58–74%), pentachlorophenol contamination (15–17%), secondary aluminum smelters (9–12%), and traffic emissions (2–13%). As for PCBs, two sources were identified as PCB3 and PCB5, two typical Chinese technical PCB products. The overall source contributions of PCB3 are 72–80% and PCB5 20–28%, which is qualitatively consistent with the proportions of technical PCB products produced in China. This can be the first attempt to semi-quantitatively apportion PCDD/Fs and PCBs in vegetation samples using different receptor models.

Nano-Co 3 O 4 was prepared by precipitation method and was successfully applied as heterogeneous catalyst to activate peroxymonosulfate (PMS) and degrade a model compound Acid Orange 7 (AO7). The catalyst exhibits spherical morphologies with minor particle agglomeration, small particle average size (20 nm) and high specific surface area (18 m 2 /g). The degradation kinetics of AO7 induced by nano-Co 3 O 4 /PMS system was investigated at both acidic and neutral pH conditions. The heterogeneous character of PMS activation with nano-Co 3 O 4 is more pronounced at neutral pH as indicated by fast degradation rate of AO7 and low dissolved Co ion. The catalyst presented a long-term stability through using the catalyst for multiple runs in the degradation of AO7. The main degradation intermediates of AO7 identified by GC/MS and LC/MS were 4-hydroxybenzenesulfonic acid, 1,2-naphthalenedione, coumarin, phthalic anhydride, phthalimide and 2-formyl-benzoic acid. Proposed degradation pathways were elucidated in light of the analyzed degradation products and frontier electron density theory.

Hydrolysis of fenoxaprop-p-ethyl (FE), a widely used herbicide, was studied in aqueous buffer solutions at pH ranging from 4.0 to 10.0. The degradation kinetics, strongly dependent on pH values, followed first-order kinetics. FE was relatively stable in neutral media, whereas it degraded rapidly with decreasing or increasing pH. In acidic conditions (pH = 4, 5), the benzoxazolyl-oxy-phenyl ether linkage of FE was cleaved to form ethyl 2-(4-hydroxyphenoxy)propanoate (EHPP) and 6-chloro-2,3-dihydrobenzoxazol-2-one (CDHB). While in basic conditions (pH = 8, 9, 10), herbicidal activity fenoxaprop-p (FA) was formed via breakdown of the ester bond of the herbicide. Both the two pathways were concurrent in neutral conditions (pH = 6, 7). Toxicity studies on Daphnia magna showed that FE was most toxic to D. magna with 48 h EC(50) of 14.3 micromol/L, followed by FA (43.8 micromol/L), CDHB (49.8 micromol/L), and EHPP (333.1 micromol/L). Mode of toxic action analysis indicated that EHPP exhibited toxicity via polar narcosis, whereas CDHB belonged to reactive acing compound. The mixture toxicity of CDHB and EHPP was nonadditive and can be predicted by a response addition model. Therefore, the evaluation of overall FE toxicity to D. magna in the aquatic systems needs to consider the degradation of FE.

Diclofop-methyl (DM) is a broad-spectrum herbicide but often shows a reduced biological activity against the target grasses due to its poor water solubility and slow translocation within plant tissues. Randomly methylated beta-cyclodextrin (MCD) is an effective inclusion complexation agent and, as a potential formulation additive, may thus improve the behavior of DM. We evaluated the complexing role of MCD by measuring the solubility and soil sorption of DM as a function of MCD concentration, as well as the dissolution rates of DM-MCD complexes. The complex was also extensively characterized by UV, fluorescence, Fourier transform infrared, nuclear magnetic resonance, and differential scanning calorimetry techniques. The apparent solubility of DM linearly increased with MCD concentration, indicating the formation of a 1:1 complex. In contrast, diclofop was not complexed by MCD. The DM-MCD complex appeared to have formed within the hydrophobic cavity of MCD. With the measured stability constant of 4740 L mol(-)(1), the complex was apparently stable, which resulted in DM resistant to hydrolysis, and hence the ratio of DM to the sum of DM and diclofop increased toward unity with increasing MCD concentration. The DM-MCD complex also quickly dissolved to a maximum within 5 min, due presumably to the hydrophilicity of MCD. The sorption of DM by soil was significantly reduced in the presence of MCD. All the results suggest that MCD may effectively improve the availability of DM to pests and for bioremediation.

Successive sulfoxidation is widely recognized as a general characteristic of the metabolism of chiral or prochiral thioethers, producing sulfoxides, and sulfones. However, information related to the stereochemistry of this process in soils is rare. In this study, the biotic transformation of the insecticide fenamiphos (a model thioether) was followed over two months in three soils, through separate incubations with fenamiphos parent, the sulfoxide intermediate (FSO), the sulfone intermediate (FSO2), and their respective stereoisomers. The results showed that the successive sulfoxidation involved oxidation of fenamiphos to FSO and subsequently to FSO2 as well as diastereomerization/enantiomerization of FSO, all of which were primarily biotic and stereoselective. The concomitant hydrolysis of fenamiphos, FSO, and FSO2 to phenols that occurred at lower rates was biotically favorable, but not stereoselective. The stereochemistry of this successive sulfoxidation transferred principally through two parallel systems, R(+)-fenamiphos → SRPR(+)-/SSPR(-)-FSO → R(+)-FSO2 and S(-)-fenamiphos → SRPS(+)-/SSPS(-)-FSO → S(-)-FSO2, between which unidirectional intersystem crossing occurred at FSO via isomeric conversions and created a system of S(-)-fenamiphos → SRPR(+)-/SSPR(-)-FSO → R(+)-FSO2. This pattern accounts for the enrichment of the intermediates SSPR(-)-/SSPS(-)-FSO and R(+)-FSO2 that are toxicologically close to the highly toxic S(-)-fenamiphos, associated with soil application of fenamiphos. Selective formation/depletion of these intermediate stereoisomers leads to dramatic variations in the ecotoxicological effects of the thioether insecticide.

Understanding the interactions between organic pollutants and carbon nanotubes (CNTs) is critical for fate assessment of both CNTs and organic pollutants. In this study, the chromatographic approach was introduced based on CNTs as stationary phase for the evaluation of such interactions. The pristine multi-walled carbon nanotubes (MWCNTs) were packed into columns of high-pressure liquid chromatography (HPLC) and the retention factors (k') were determined to characterize the adsorption affinity of organic compounds onto MWCNTs. Nine compounds were tested. The results showed that their lnk' values followed the order: benzene < toluene < phenol < chlorobenzene < bromobenzene < aniline < sulfamethoxazole < sulfadiazine ≈ sulfadimidine. The linear solvation energy relationship (LSER) theory was adopted to correlate lnk' with the molecular solvatochromic parameters. We found that lnk' of the studied compounds correlate positively with molecular polarizability (E) significantly, suggesting that the π-/n-electrons-dependent polarizable interactions play a major role for the adsorption. Moreover, the thermodynamic parameters calculated from van't Hoff equations revealed that the interactions between the compounds and MWCNTs were spontaneous and exothermic processes.