Satellite taxa regulated the response of constructed wetlands microeukaryotic community to changing hydraulic loading rate.

Revealing how species interaction and assembly processes structure the core and satellite microeukaryotic subcommunities in an engineering environment is crucial for understanding how biodiversity influences system function. By investigating the core and satellite microeukaryotic subcommunities in constructed wetlands (CWs), we depicted an integrated distribution pattern of microeukaryotic communities in the CWs with different hydraulic loading rates (HLRs). Surprisingly, our results suggested that high HLR reduced the diversity and network stability of the microeukaryote community in CW. The stochastic process becomes more important with the increased HLR. In addition, satellite and core taxa varied inconsistently under different HLRs except for niche breadth. And the changes in all taxa were consistent with those in satellite taxa. Satellite taxa, but not core taxa, was an important driver in shaping the dynamics of microeukaryotic communities and played an important role in maintaining the stability of the microeukaryotic community. Overall, our results not only fill a gap in understanding the microeukaryotic community dynamics and its basic drivers of CWs under different HLRs but also highlights the particular importance of satellite microeukaryotes in mediating biogeochemical cycles in CWs ecosystems.

Performance of permeable pavement systems on stormwater permeability and pollutant removal.

Permeable pavement is an effective means for stormwater runoff control and pollutant removal. However, relatively few studies have examined the characteristics of permeable brick and corresponding permeable pavement system (PPS). In this work, the permeable pavement systems consisted of surface permeable brick layer (concrete or ceramic) with structural layer (including a cement mortar layer, a permeable concrete layer, and a gravel layers) were selected as typical cases to assess their permeability and runoff pollutant removal performance by laboratory experiments. The results indicated that PPS had obvious outflow hysteresis effect. The PPS with ceramic brick layer reached the saturation flow rate earlier and showed larger outflow rate than that with concrete brick layer. Both types of PPSs had a relatively high efficiency (83.8-95.2%) in removing suspended solids (SS) in stormwater runoff mainly due to the interception and filtration of the surface brick layer, whereas the structural layer of the PPS played a vital role in the removal of total phosphorus (TP). The percentage of total nitrogen (TN) removal efficiency via ceramic brick layer accounted for via corresponding PPS was obviously larger than that of concrete brick layer. The PPS also displayed a certain chemical oxygen demand (COD) removal ability: around 14.0-27.0% for concrete type and 20.9-28.9% for ceramic type. Subsequently, a multi-objective evaluation model was implemented based on the analytic hierarchy process (AHP) method to identify the optimal scheme in relation to four indices: permeability, environmental benefit, compressive strength, and comprehensive economic cost. The results showed, insofar, the ceramic PPS is preferred with a better economic performance. Our study attempts to select optimal designs of PPS and provides insight into the permeable capacity and the efficiency of pollutant removal in PPS.

CRAGE-Duet Facilitates Modular Assembly of Biological Systems for Studying Plant-Microbe Interactions.

Developing sustainable agricultural practices will require increasing our understanding of plant-microbe interactions. To study these interactions, new genetic tools for manipulating nonmodel microbes will be needed. To help meet this need, we recently reported development of chassis-independent recombinase-assisted genome engineering (CRAGE). CRAGE relies on cassette exchange between two pairs of mutually exclusive lox sites and allows direct, single-step chromosomal integration of large, complex gene constructs into diverse bacterial species. We then extended CRAGE by introducing a third mutually exclusive lox site, creating CRAGE-Duet, which allows modular integration of two constructs. CRAGE-Duet offers advantages over CRAGE, especially when a cumbersome recloning step is required to build single-integration constructs. To demonstrate the utility of CRAGE-Duet, we created a set of strains from the plant-growth-promoting rhizobacterium Pseudomonas simiae WCS417r that expressed various fluorescence marker genes. We visualized these strains simultaneously under a confocal microscope, demonstrating the usefulness of CRAGE-Duet for creating biological systems to study plant-microbe interactions.

CRAGE enables rapid activation of biosynthetic gene clusters in undomesticated bacteria.

It is generally believed that exchange of secondary metabolite biosynthetic gene clusters (BGCs) among closely related bacteria is an important driver of BGC evolution and diversification. Applying this idea may help researchers efficiently connect many BGCs to their products and characterize the products' roles in various environments. However, existing genetic tools support only a small fraction of these efforts. Here, we present the development of chassis-independent recombinase-assisted genome engineering (CRAGE), which enables single-step integration of large, complex BGC constructs directly into the chromosomes of diverse bacteria with high accuracy and efficiency. To demonstrate the efficacy of CRAGE, we expressed three known and six previously identified but experimentally elusive non-ribosomal peptide synthetase (NRPS) and NRPS-polyketide synthase (PKS) hybrid BGCs from Photorhabdus luminescens in 25 diverse γ-Proteobacteria species. Successful activation of six BGCs identified 22 products for which diversity and yield were greater when the BGCs were expressed in strains closely related to the native strain than when they were expressed in either native or more distantly related strains. Activation of these BGCs demonstrates the feasibility of exploiting their underlying catalytic activity and plasticity, and provides evidence that systematic approaches based on CRAGE will be useful for discovering and identifying previously uncharacterized metabolites.

Near-equilibrium glycolysis supports metabolic homeostasis and energy yield.

Glycolysis plays a central role in producing ATP and biomass. Its control principles, however, remain incompletely understood. Here, we develop a method that combines 2H and 13C tracers to determine glycolytic thermodynamics. Using this method, we show that, in conditions and organisms with relatively slow fluxes, multiple steps in glycolysis are near to equilibrium, reflecting spare enzyme capacity. In Escherichia coli, nitrogen or phosphorus upshift rapidly increases the thermodynamic driving force, deploying the spare enzyme capacity to increase flux. Similarly, respiration inhibition in mammalian cells rapidly increases both glycolytic flux and the thermodynamic driving force. The thermodynamic shift allows flux to increase with only small metabolite concentration changes. Finally, we find that the cellulose-degrading anaerobe Clostridium cellulolyticum exhibits slow, near-equilibrium glycolysis due to the use of pyrophosphate rather than ATP for fructose-bisphosphate production, resulting in enhanced per-glucose ATP yield. Thus, near-equilibrium steps of glycolysis promote both rapid flux adaptation and energy efficiency.

Phosphate enhanced abiotic and biotic arsenic mobilization in the wetland rhizosphere.

Although abiotic process of competitive sorption between phosphate (P) and arsenate (As(V)), especially onto iron oxides, are well understood, P-mediated biotic processes of Fe and As redox transformation contributing to As mobilization and speciation in wetlands remain poorly defined. To gain new insights into the effects of P on As mobility, speciation, and bioavailability in wetlands, well-controlled greenhouse experiments were conducted. As expected, increased P levels contributed to more As desorption, but more interestingly the interactions between P and wetland plants played a synergistic role in the microbially-mediated As mobilization and enhanced As uptake by plants. High levels of P promoted plant growth and the exudation of labile organic carbon from roots, enhancing the growth of heterotrophic bacteria, including As and Fe reducers. This in turn resulted in both, more As desorption into solution due to reductive iron dissolution, and a higher fraction of the dissolved As in the form of As(III) due to the higher number of As(V) reducers. Consistent with the dissolved As results, arsenic-XANES spectra from solid medium samples demonstrated that more As was sequestered in the rhizosphere as As(III) in the presence of high P levels than for low P levels. Hence, increased P loading to wetlands stimulates both abiotic and biotic processes in the wetland rhizosphere, resulting in more As mobilization, more As reduction, as well as more As uptake by plants. These interactions are important to be taken into account in As fate and transport models in wetlands and management of wetlands containing As.

Effect of dissimilatory iron and sulfate reduction on arsenic dynamics in the wetland rhizosphere and its bioaccumulation in wetland plants (Scirpus actus).

Microbial redox transformations of arsenic (As) are coupled to dissimilatory iron and sulfate reduction in the wetlands, however, the processes involved are complex and poorly defined. In this study, we investigated the effect of dissimilatory iron and sulfate reduction on As dynamics in the wetland rhizosphere and its bioaccumulation in plants using greenhouse mesocosms. Results show that high Fe (50µM ferrihydrite/g solid medium) and SO42- (5mM) treatments are most favorable for As sequestration in the presence of wetland plants (Scirpus actus), probably because root exudates facilitate the microbial reduction of Fe(III), SO42-, and As(V) to sequester As(III) by incorporation into iron sulfides and/or plant uptake. As retention in the solid medium and accumulation in plants were mainly controlled by SO42- rather than Fe levels. Compared to the low SO42- (0.1mM) treatment, high SO42- resulted in 2 times more As sequestered in the solid medium, 30 times more As in roots, and 49% less As in leaves. An As speciation analysis in pore water indicated that 19% more dissolved As was reduced under high SO42- than low SO42- levels, which is consistent with the fact that more dissimilatory arsenate-respiring bacteria were found under high SO42- levels.

[The Development of Ammonia Sensor Based on Tunable Diode Laser Absorption Spectroscopy with Hollow Waveguide].

Hollow waveguides(HWG)have recently emerged as a novel concept serving as an efficient optical waveguide and a highly miniaturized gas cell. Compared with conventional multi-pass gas cells, HWG gas cell has the advantages of facilitating gas exchanging because of its small size and fast responding speed. In this paper, we poposed an ammonia sensor based on tunable diode laser absorption spectroscopy(TDLAS) using HWG as the gas cell. The sensor employs wavelength modulation spectrum(WMS) with simultaneous detection of the second harmonic(2f) signal and the first hamonic(1f) signal. Normalization of the 2f signal by the 1f signal enables the sensor for calibration free measurement. The sensor performance is tested with gas standards and the result shows good linearity with correlation coefficient of 0.999 8, and the detection limit is 26 ppb with an integration time of 18 s. The sensor based on HWG gas cell is suitable for sensative and real-time monitoring ammonia in the air.

Cadmium adsorption on plant- and manure-derived biochar and biochar-amended sandy soils: impact of bulk and surface properties.

To investigate the role of the bulk and surface composition of both biochar and biochar-amended soils in the adsorption of Cd(2+), as well as the influence of different biochars added to the soils on Cd(2+) adsorption, swine-manure-derived biochars (BSs) and wheat-straw-derived biochars (BWs) were produced at 300, 450, and 600°C. These biochars were added to a sandy soil to investigate the effect of biochars on the adsorption of Cd(2+) by soil. The significantly higher surface C content of the amended soils compared to their bulk C content suggests that the minerals of the biochar-amended soils are most likely covered primarily by biochars. The maximum adsorption capacity (Qmax,total) of the BSs was 10-15 times higher than that of the BWs due to the high polarity and ash content of the BSs. The polarity ((N+O)/C) of the low-temperature biochars greatly affected their Cd(2+) adsorption. The Qmax,total of the BS-amended soils increased with increasing dose, whereas the Qmax,total of the BW-amended soils showed the opposite behavior, which was attributed to the different surface composition characteristics of the two types of soil. The BSs were more effective in immobilizing Cd(2+) upon application to the soil relative to the BWs. This study elucidates the spatial distribution of biochars in biochar-amended soils and highlights the importance of the surface composition of the investigated samples in Cd(2+) adsorption.

Impact of deashing treatment on biochar structural properties and potential sorption mechanisms of phenanthrene.

Knowledge of the mineral effects of biochars on their sorption of hydrophobic organic contaminants (HOCs) is limited. Sorption of phenanthrene (PHE) by plant-residue derived biochars (PLABs) and animal waste-derived biochars (ANIBs) obtained at two heating treatment temperatures (HTTs) (450 and 600 °C) and their corresponding deashed biochars was investigated. The decreased surface polarity and increased bulk polarity of biochars after deashing treatment indicated that abundant minerals of biochars benefit external exposure of polar groups associated organic matter (OM). Organic carbon (OC)-normalized distribution coefficients (K(oc)) of PHE by biochars generally increased after deashing, likely due to enhancement of favorable and hydrophobic sorption sites caused by mineral removal. Positive correlation between PHE log K(oc) by PLABs and bulk polarity combined with negative correlation between PHE log K(oc) values by ANIBs and surface polarity suggested PLABs and ANIBs have different sorption mechanisms, probably attributed to their large variation of ash content because minerals influenced OM spatial arrangement within biochars. Results of this work could help us better understand the impact of minerals, bulk/surface polarity, and sorption domain arrangement of biochars on their HOCs sorption and predict the fate of HOCs in soils after biochar application.

Isolation and characterization of different organic matter fractions from a same soil source and their phenanthrene sorption.

Four humic acids (HAs) including de-ashed HAs (D-HAs), two humins (HMs), nonhydrolyzable carbons, and demineralized fraction (DM) were isolated separately from two soils and characterized detailedly; then their sorption of phenanthrene (Phen) was examined. The sequence of removal of HAs and minerals affected molecular composition of HMs. After de-ashing, thermal stability of HAs was improved; however, sorption (logKoc) also decreased due to removal of amorphous alkyl-C. Significant correlations between CO2 surface area of HAs with their sorption coefficients (n and Koc) suggested that pore filling could dominate Phen sorption. Alkyl-C could facilitate elevated thermal stability of OM and Phen sorption, supporting that thermal stability of OM was correlated with Phen sorption. The OM fraction composed of aromatic moieties (AMs) did not produce the highest logKoc, providing strong evidence to dispute the dominant role of AMs in Phen sorption. No correlations between the Koc values of Phen by all tested sorbents and their bulk or surface polarity were observed, suggesting that the role of bulk or surface polarity of OM fractions in regulating Phen sorption was dependent on soil sources. This work shows the major influence of bulk and surface composition of OM and amorphous alkyl-C isolated from a soil sample on hydrophobic organic compounds sorption.

Sorption of phthalic acid esters in two kinds of landfill leachates by the carbonaceous sorbents.

Sorption of phthalic acid esters (PAEs: diethyl phthalate, DEP: dibutyl phthalate, DBP as model compounds) in landfill leachates by activated carbon (AC), carbon nanotubes (CNTs), and biochars, were examined. The young leachate (YL) and old leachate (OL) were synthesized to imitate acetogenic and methanogenic phases, respectively, and glucose (GLU) and fulvic acid (FA) were selected to represent dissolved organic matter (DOM). GLU in leachates generally facilitated the sorption of PAEs while FA restrained sorption of PAEs, suggesting the type of DOM associated with leachates possibly regulated the removal efficiency of PAEs from leachates. The pores and organic carbon of carbonaceous sorbents should be major factors in influencing the sorption of PAEs in leachates. The data showed PAEs in acetogenic leachates was removed more easily than those in methanogenic leachates and CNTs have the less advantage to remove PAEs from methanogenic leachates compared to AC.

Adsorption of diuron, fluridone and norflurazon on single-walled and multi-walled carbon nanotubes.

The sorption behaviors of diuron (DIU), fluridone (FLU) and norflurazon (NOR) by a single-walled carbon nanotube (SWCNT) and three multi-walled carbon nanotubes (MWCNT) samples including MWCNT10 (<10nm, outer diameter), MWCNT20 (10-20 nm), and MWCNT40 (20-40 nm) were investigated. All adsorption isotherms were nonlinear and were well fitted with the Freundlich model and Dubinin Ashtakhov (DA) model. The linear relationships between the organic carbon (OC)-normalized saturated adsorption capacity (Q(0)(OC)) and surface area (SA) suggest that SA is presumably responsible for the adsorption of DIU and NOR on CNTs. While FLU, DIU, and NOR OC-normalized distribution coefficients (logK(OC)) of CNTs increased with increasing their hydrophobicity (logK(OW)) and the positive relationships between the logK(OW)-normalized logK(OC) (i.e., logK(OC)/logK(OW)) of FLU, DIU, and NOR and their hydrogen bonding ability indicate that the adsorption of FLU, DIU and NOR was mainly controlled by the hydrophobic interaction and hydrogen bonding. The higher logK(OC) or Q(0)(OC) values of MWCNT10 and SWCNT relative to other large MWCNTs and carbonaceous adsorbents suggest that MWCNT10 has the potential to serve as an adsorbent used to reduce the mobility of herbicides in agricultural and environmental applications.

Degradation behavior of 17alpha-ethinylestradiol by ozonation in the synthetic secondary effluent.

Endocrine disrupting chemicals (EDCs) in the secondary effluent discharged from wastewater treatment plants (WWTPs) are of great concern in the process of water reuse. Ozonation has been reported as a powerful oxidation technology to eliminate micropollutants in water treatment. Due to the complexity of the wastewater matrix, orthogonal experiments and single factor experiments were conducted to study the influence of operational parameters on the degradation of 17a-ethinylestradiol (EE2) in the synthetic secondary effluent. The results of the orthogonal experiments indicated that the initial ozone and natural organic matter (NOM) concentration significantly affected EE2 degradation efficiency, which was further validated by the single factor confirmation experiments. EE2 was shown to be effectively degraded by ozonation in the conditions of low pH (6), NOM (10 mg/L), carbonate (50 mg/L), but high suspended solid (20 mg/L) and initial ozone concentration (9 mg/L). The study firstly revealed that the lower pH resulted in higher degradation of EE2 in the synthetic secondary effluent, which differed from EDCs ozonation behavior in pure water. EE2 degradation by ozone molecule instead of hydroxyl radical was proposed to play a key role in the degradation of EDCs by ozonation in the secondary effluent. The ratio between 03 and TOC was identified as an appropriate index to assess the degradation of EE2 by ozonation in the synthetic secondary effluent.

Sorption of 17α-ethinyl estradiol, bisphenol A and phenanthrene to different size fractions of soil and sediment.

The potential for negative effects caused by endocrine disrupting chemicals (EDCs) release into the environment is a prominent concern and numerous research projects have investigated possible environmental fate and toxicity. However, their sorption behavior by size fractions of soil and sediment has not been systematically represented. The sorption of bisphenol A (BPA), 17α-ethinyl estradiol (EE2) and phenanthrene (Phen) by different size fractions of soil and sediment were investigated. Sorption isotherms of EE2, BPA, and Phen by size fractions of soil (SL) and sediment (ST) were well fitted to the Freundlich model. The positive correlation between EE2, BPA and Phen sorption capacity (logK(d)) of size fractions and their organic carbon (OC) content suggests that OC of size fractions in SL and ST should regulate sorption, while the surface area (SA) of size fractions may not account for sorption of EE2, BPA and Phen. Each size fraction of ST had higher sorption capacity (K(d) or K(OC)) of EE2 and BPA than that of SL due to their difference in the polarity of organic matter (OM) between terrestrial and aquatic sources. Sorption capacity logK(d) for size fractions of SL and ST did not follow the order: clay>silt>sand due to the difference in OM abundance and composition between the size fractions. Large particle fractions of ST contributed about 80% to the overall sorption for any EE2, BPA, and Phen. This study was significant to evaluate size fractions of soil and sediment as well as their associated OM affecting EE2 and BPA sorption processes.

Adsorption of tetracycline on soil and sediment: effects of pH and the presence of Cu(II).

Tetracycline (TC) is frequently detected in the environment, however, knowledge on the environmental fate and transport of TC is still limited. Batch adsorption experiments of TC by soil and sediment samples were conducted. The distribution of charge and electrostatic potential of individual atoms of various TC species in the aqueous solution were determined using MOPAC version 0.034 W program in ChemBio3D Ultra software. Most of the adsorption isotherms on the soil, river and marine sediments were well fitted with the Freundlich and Polanyi-Manes (PMM) models. The single point organic carbon (OC)-normalized adsorption distribution coefficients (K(OC)) and PMM saturated adsorption capacity (Q(OC)(0)) values of TC were associated with the mesopore volume and clay content to a greater extent, indicating the mesopore volume of the soil and sediments and their clay content possibly influenced the fate and transport of TC in the natural environment. The adsorption of TC on soil and sediments strongly depended on the pH and presence of Cu(II). The presence of Cu(II) facilitated TC adsorption on soil and sediments at low pH (pH<5), possibly due to the metallic complexation and surface-bridging mechanism by Cu(II) adsorption on soil and sediments. The cation exchange interaction, metallic complexation and Coulombic interaction of mechanisms for adsorption of TC to soils and sediments were further supported by quantum chemical calculation of various TC species in different pH.

Sorption of atrazine and phenanthrene by organic matter fractions in soil and sediment.

Atrazine and phenanthrene (Phen) sorption by nonhydrolyzable carbon (NHC), black carbon (BC), humic acid (HA) and whole sediment and soil samples was examined. Atrazine sorption isotherms were nearly linear. The single-point organic carbon (OC)-normalized distribution coefficients (K(OC)) of atrazine for the isolated HA1, NHC1 and BC1 from sediment 1 (ST1) were 36, 550, and 1470 times greater than that of ST1, respectively, indicating the importance of sediment organic matter, particularly the condensed fractions (NHC and BC). Similar sorption capacity of atrazine and Phen by NHC but different isotherm nonlinearity indicated different sorption domains due to their different structure and hydrophobicity. The positive relationship between (O+N)/C ratios of NHC and atrazine logK(OC) at low concentration suggests H-bonding interactions. This study shows that sediment is probably a less effective sorbent for atrazine than Phen, implying that atrazine applied in sediments or soils may be likely to leach into groundwater.

Sorption of endocrine disrupting chemicals by condensed organic matter in soils and sediments.

Sorption of 17alpha-ethinyl estradiol (EE2) and bisphenol A (BPA) by nonhydrolyzable carbon (NHC), black carbon (BC), and bulk soils and sediments was examined. All sorption isotherms were nonlinear and fitted both Freundlich and Dubinin-Ashtakhov (DA) models. The single-point organic carbon (OC)-normalized distribution coefficient (K(OC)) of EE2 for the isolated NHC and BC was 2.7-4.8 times and 5.4-12.9 times greater, respectively, than that of the bulk samples. However, no clear trend in BPA K(OC) values was observed. Based on the contribution of soil/sediment organic matter (SOM) fractions to the overall sorption of BPA or EE2 by the bulk samples, condensed SOM (NHC and BC) generally played a dominant role to the overall sorption. The BPA adsorption capacity (Q(OC)(0)) from the DA model was higher than that of EE2 on NHC and there was obvious difference in isotherm nonlinearity (n) between EE2 and BPA. These results suggest that BPA may have more access to the pore sites of NHC samples than EE2. The pi-pi bonds formed between BPA and NHC or BC may be stronger than that between EE2 and NHC or BC. This would be attributed to the fact that BPA has two benzene rings, and can also be used to explain the difference in hexadecane-water partition coefficient (K(HW))-normalized K(OC) values (K(OC)/K(HW)) of BPA and EE2 after factoring out the hydrophobic effect. These findings could be useful for predicting fate and ecological risks of endocrine disrupting chemicals (EDCs) (e.g., EE2 and BPA) in natural environments especially when soils or sediments become receptors for EDCs.

Organochlorine pesticides and polybrominated diphenyl ethers in irrigated soils of Beijing, China: levels, inventory and fate.

Limited information on the levels, inventory and fate of Organochlorine pesticides (OCPs) and Polybrominated diphenyl ethers (PBDEs) in the soils irrigated by sewage or wastewater is available. In this study, variation in concentrations, profiles and fate of OCPs and PBDEs were investigated using soil samples collected from a region irrigated by sewage, mixed water and clean water in the east of Beijing, China. No significant variation was observed among groups, except for penta-BDEs. The measured SigmaOCPs and SigmaPBDEs residues ranged from 6.4 to 171.2 ng g(-1) (dw) and 501.9 to 3310.7 pg g(-1) (dw), respectively. SigmaDDTs and BDE-209 were the most abundant congeners accounting for about 76% of SigmaOCPs and 93% of SigmaPBDEs. Concentrations of hexachlorocyclohexanes (HCHs), dichlorodiphenyltrichloroethane (DDTs) and its major degradation products, and hexachlorobenzene (HCB) ranged from 1.2 to 11.4 ng g(-1) (dw), 4.0 to 155.6 ng g(-1) (dw) and 0.3 to 3.4 ng g(-1) (dw), respectively. The major DDT degradation products were p,p'-DDT and p,p'-DDE. The major hexachlorocyclohexane (HCH) isomer in irrigated soils is beta-HCH, reflecting its higher affinity to solids and resistance to degradation than other isomers. Both alpha-HCH/beta-HCH and p,p'-DDT/p,p'-DDE ratios were log-normally distributed and negatively correlated to log(SigmaHCHs) and log(SigmaDDTs), respectively, suggesting no significant recent application of OCPs. Individual BDE congeners, SigmaPBDEs and SigmaOCPs were significantly correlated with total organic carbon (TOC). Moreover, a good correlationship between SigmaPBDEs and black carbon (BC) was obtained but not between SigmaOCPs and BC. Sewage irrigation did not have obvious effect on their contaminant levels and inventory of OCPs and PBDEs.

A QSAR model for predicting mutagenicity of nitronaphthalenes and methylnitronaphthalenes.

A quantitative structure-activity relationship model for prediction of mutagenicity of nitronaphthalenes and methylnitronaphthalenes was developed using some fundamental quantum chemical descriptors. The cumulative cross-validated regression coefficient value for the optimal quantitative structure-activity relationship model is 0.711, showing a good predictive capability for mutagenicity of nitronaphthalenes and methylnitronaphthalenes. Results from this study indicate that mutagenicity of nitronaphthalenes and methylnitronaphthalenes increases with increasing frontier molecular orbital energy value, i.e., the sum of the energy of the highest occupied molecular orbital and the energy of the lowest unoccupied molecular orbital, or decreasing the energy of the second highest occupied molecular orbital, final heat of formation, and core-core repulsion energy values.