Journal of Hazardous Materials 279 (2014) 156–162

Contents lists available at ScienceDirect

Journal of Hazardous Materials journal homepage: www.elsevier.com/locate/jhazmat

Evaluation on joint toxicity of chlorinated anilines and cadmium to Photobacterium phosphoreum and QSAR analysis Hao Jin a,∗ , Chao Wang b , Jiaqi Shi b , Lei Chen a a b

School of Life and Chemistry, Jiangsu Second Normal University, Nanjing, Jiangsu 210013, PR China State Key Laboratory of Pollution Control and Resources Reuse, School of Environment, Nanjing University, Nanjing, Jiangsu 210023, PR China

h i g h l i g h t s • • • • •

Cd has different effects on joint toxicity when in different concentrations. The toxicity of most binary mixtures decreases when Cd concentration rises. Different QSAR models are developed to predict the joint toxicity. Descriptors in QSARs can help to elucidate the joint toxicity mechanism. Van der Waals’ force or complexation may reduce the toxicity of mixtures.

a r t i c l e

i n f o

Article history: Received 18 March 2014 Received in revised form 21 June 2014 Accepted 23 June 2014 Available online 11 July 2014 Keywords: Chlorinated anilines Cadmium Photobacterium phosphoreum Joint toxicity QSAR models

a b s t r a c t The individual IC50 (the concentrations causing a 50% inhibition of bioluminescence after 15 min exposure) of cadmium ion (Cd) and nine chlorinated anilines to Photobacterium phosphoreum (P. phosphoreum) were determined. In order to evaluate the combined effects of the nine chlorinated anilines and Cd, the toxicities of chlorinated anilines combined with different concentrations of Cd were determined, respectively. The results showed that the number of chlorinated anilines manifesting synergy with Cd decreased with the increasing Cd concentration, and the number manifesting antagonism decreased firstly and then increased. The joint toxicity of mixtures at low Cd concentration was weaker than that of most binary mixtures when combined with Cd at medium and high concentrations as indicated by TUTotal . QSAR analysis showed that the single toxicity of chlorinated anilines was related to the energy of the lowest unoccupied molecular orbital (ELUMO ). When combined with different concentrations of Cd, the toxicity was related to the energy difference (EHOMO − ELUMO ) with different coefficients. Van der Waals’ force or the complexation between chlorinated anilines and Cd had an impact on the toxicity of combined systems, which could account for QSAR models with different physico-chemical descriptors. © 2014 Elsevier B.V. All rights reserved.

1. Introduction The individual toxicity of chlorinated anilines is commonly investigated in the literatures [1–3]. However, the toxic effects caused by the presence of mixture of compounds instead of a single substance have been a growing concern in recent years. The effects of chemical mixtures on ecosystems and organisms may be different from that would be observed from individual chemical alone [4]. In other words, in terms of ecological risk assessment in contaminated aquatic environments, using toxicity data of single chemical may fail to predict interactions and associated effects of

∗ Corresponding author. Tel.: +86 25 89758338; fax: +86 25 89758338. E-mail address: [email protected] (H. Jin). http://dx.doi.org/10.1016/j.jhazmat.2014.06.068 0304-3894/© 2014 Elsevier B.V. All rights reserved.

chemicals in mixtures [5,6]. Therefore, it is necessary to develop techniques to analyze and predict the combined effect of toxic chemicals in the realistic environment [7,8]. In the past decade, interest has arisen in examining the toxic effects of complicated mixtures of environmental contaminants [5,6,9–11]. Most studies have been carried out on the combined toxicity either among heavy metals [12–14] or among organic pollutants [5–8,10,15]. However, information on the joint toxicity of organic compounds and heavy metals to organisms is still lacking. Jiang et al. [16] found that the interactive toxic effect of phenanthrene and Cd to earthworm Eisenia andrei was antagonistic. Rodea-Palomares et al. [17] investigated the mixtures of Cd and the perfluorinated surfactants (perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA)) to bioluminescent cyanobacterium Anabaena CPB1337 and found that the interaction

H. Jin et al. / Journal of Hazardous Materials 279 (2014) 156–162

157

Fig. 1. Chemical structures of the selected chlorinated anilines.

between either PFOS or PFOA and Cd was mostly antagonistic. Wang et al. [18] investigated the combined toxicity of five polycyclic aromatic hydrocarbons (PAHs) and Cd on the antioxidant responses of Selenastrum capricornutum, finding that the interactions could be additive, synergistic, or antagonistic. In order to predict the toxicity of chemicals with little or no empirical data, the quantitative structure–activity relationships (QSARs), as reliable tools, have been introduced into the field of environmental toxicology [19]. In comparison with single toxicity prediction, the combined toxicity of chemical mixtures predicted by QSAR models is currently a major challenge in aquatic ecotoxicology [20]. On the one hand, the combined effects of contaminants are various, such as simple addition, antagonism and synergism [20–23]. On the other hand, some studies have shown that the composition of compounds, the toxic ratios, and the concentration of compounds might lead to different toxic responses [20,23,24]. Therefore, contaminants, their concentrations and ratios should be considered when modeling mixture toxicity. Chlorinated anilines and Cd are environmental pollutants of considerable concern. They are present in the environment at detectable levels and considered priority pollutants in environmental risk assessment [25,26]. In this paper, the aquatic organism, P. phosphoreum, was chosen as the test organism to determine individual toxicities of chlorinated anilines and Cd. In order to investigate the effect of combined ratios on the joint toxicity, mixture toxicity between chlorinated anilines and Cd was determined by setting three different levels of Cd concentrations (0.2 × IC50 , 0.5 × IC50 , 0.8 × IC50 ) [20]. The objectives of the present study are: firstly, to evaluate the acute toxic effects of binary mixtures of each individual chlorinated anilines and Cd; secondly, to develop QSAR models to investigate the relationships between joint toxicity and calculated molecular parameters at different Cd concentrations; thirdly, to elucidate the joint toxicity mechanism.

2. Materials and methods 2.1. Chemicals Nine chlorinated anilines (purity of ≥97%, see Fig. 1 for chemical structures) were purchased from Aladdin Industrial Corporation. Other compounds such as NaCl used for preparation of liquid medium were of chemically pure quality. The toxicity of cadmium was evaluated using cadmium sulfate, 8/3-hydrate (3CdSO4 ·8H2 O, purity of >99%) provided by Sinopharm Chemical Reagent Co., Ltd. Since chlorinated anilines own low solubility in water, each stock solution of tested aromatic compounds was prepared by dissolving the chemicals in deionized water containing 10% dimethylsulfoxide. In the final experiments, the content of dimethylsulfoxide was diluted to less than 1%, which has little effect on the luminescent intensity of P. phosphoreum. 2.2. Bioassay The freeze-dried powder of P. phosphoreum sp. T3 was obtained from the Institute of Soil Science, Chinese Academy of Sciences (Nanjing, China). The test was carried out according to the national standard method of China (Water quality – Determination of the acute toxicity – Luminescent bacteria test. GB/T 15441-1995). The concentration series were arranged in a 96-well (8 rows × 12 columns) black flat-bottom microplate (GRE, USA). Bioluminescence of various treatments and controls (solution only containing 3% NaCl) were determined on Tecan Infinite 200® PRO multimode microplate reader after the exposure of 15 min at 25 ◦ C. To investigate the influence of Cd concentration on the binary joint toxicity of each chlorinated aniline and Cd to P. phosphoreum, Cd concentration was set at three levels, 0.2, 0.5, and 0.8 × IC50 of Cd (low, medium and high levels). Each concentration of Cd combined with nine concentrations of the tested chlorinated aniline, which

158

H. Jin et al. / Journal of Hazardous Materials 279 (2014) 156–162

varied from low to high by equal interval of logarithm, was used in the mixture toxicity test. The IC50 of each chlorinated aniline compound at each level of Cd concentration was obtained according to the method described above. Particularly, Cd will not be precipitated in the condition of present study, so it is able to coexist with chlorinated anilines.

Table 1 Single and joint toxicity of chlorinated anilines and Cd. Mixture

CCd (×IC50 )

TUCA (CCA )a

TUTotal

1

Cd + ochloroaniline

0 0.2 0.5 0.8

(112.10) 0.28 (31.84) 0.20 (22.66) 0.24 (27.03)

0.48 0.70 1.04

2

Cd + mchloroaniline

0 0.2 0.5 0.8

(84.22) 0.36 (30.48) 0.24 (20.54) 0.38 (32.15)

0.56 0.74 1.18

3

Cd + pchloroaniline

0 0.2 0.5 0.8

(54.95) 0.29 (15.70) 0.23 (12.82) 0.17 (9.26)

0.49 0.73 0.97

4

Cd + 2,3dichloroaniline

0 0.2 0.5 0.8

(30.79) 0.73 (22.56) 0.47 (14.45) 0.40 (12.21)

0.93 0.97 1.20

5

Cd + 2,4dichloroaniline

0 0.2 0.5 0.8

(27.23) 0.59 (16.16) 0.30 (8.08) 0.24 (6.50)

0.79 0.80 1.04

6

Cd + 2,5dichloroaniline

0 0.2 0.5 0.8

(19.26) 1.04 (20.07) 0.64 (12.37) 0.65 (12.48)

1.24 1.14 1.45

7

Cd + 2,6dichloroaniline

0 0.2 0.5 0.8

(22.14) 1.26 (27.88) 0.98 (21.64) 0.58 (12.84)

1.46 1.48 1.38

8

Cd + 3,4dichloroaniline

0 0.2 0.5 0.8

(22.73) 0.84 (19.19) 0.35 (7.86) 0.33 (7.46)

1.04 0.85 1.13

9

Cd + 2,4,5trichloroaniline

0 0.2 0.5 0.8

(10.96) 1.17 (12.80) 0.56 (6.09) 0.51 (5.58)

1.37 1.06 1.31

No.

2.3. Theoretical calculation In this study, all the calculations were performed with density functional theory (DFT) method using Gaussian 09W program package [27]. The Becke-3-Lee-Yang-Parr (B3LYP) [28,29] methods with 6-311G** basis set was employed to determine the electronic, structural, and thermodynamic properties of the chlorinated anilines. The selected parameters were energy of the highest occupied molecular orbital (EHOMO ), energy of the lowest unoccupied molecular orbital (ELUMO ), the energy difference (EHOMO − ELUMO ), mean polarizability (˛), dipole moment (), the charge on the nitrogen atom (qN− ), the most positive partial charge on a hydrogen atom (qH− ), molecular volume (V), zero-point energy (ZPE), the standard state entropy (S◦ ), absolute enthalpy (H◦ ) and Gibbs free energies (G◦ ) [30–34]. 2.4. Statistical analyses of QSAR models QSAR models were developed using the stepwise linear regression method in the statistic package SPSS17.0 (SPSS Company, Chicago, IL, USA). Model quality was mainly characterized by the number of observations (n), the correlation coefficient (R2 ), the standard error of estimated (SE), Fisher’s criterion (F) and a significance level (P). In addition, the cross-validation coeffi2 ) and the root-mean-square error of cross-validation cient (QLOO (RMSECV ), calculated with LOO-CV statistics, were used to verify internal predictability of each model [35,36]. 2.5. Evaluation methods for joint toxicity Toxic unit (TU) [37] was applied to analyze and quantify the joint effects of mixtures. In this study, TU was correlated with IC50 based on the concentration-response results of individual toxicity tests. This concept is mathematically expressed for the components of a mixture as the following formula TUi =

Ci IC50i

(1)

where TUi is the toxic unit of a chemical i in an n-component mixture, Ci is the concentration of the chemical i that causes 50% inhibition on the bioluminescence of P. phosphoreum in the mixed system, and IC50i is the concentration of the chemical causing the same response when acting alone. The sum of TUi is defined as TUtotal (TUtotal = ˙TUi ). Since the ideal simple addition determined from TUtotal = 1 is not easy to reach, Broderius et al. [38] defined simple addition with TUtotal values equal to 1 ± 0.2. The method was also applied by Su et al. [20]. In general, when TUtotal < 0.8, 0.8 ≤ TUtotal ≤ 1.2 and TUtotal > 1.2, the combined effect was defined as synergism, simple addition and antagonism, respectively. 3. Results and discussion 3.1. Evaluation on joint toxicity of chlorinated anilines and Cd The single and joint toxicity of chlorinated anilines with Cd were listed in Table 1. The toxicity of Cd to P. phosphoreum was measured and the IC50 of Cd was 1.742 ± 0.096 mg/L. At the low Cd concentration (0.2 × IC50 ), simple addition, antagonism and synergism existed for different mixtures. The binary combined

a TUCA is the toxic unit of chlorinated anilines in the presence of different concentrations of Cd; CCA is the concentration causing 50% inhibition on the bioluminescence of chlorinated anilines in mixtures (mg/L).

effects were synergistic for Cd combined with o-chloroaniline, m-chloroaniline, p-chloroaniline and 2,4-dichloroaniline, with TUtotal values varied from 0.48 to 0.79. Simple addition was found for Cd combined with 2,3-dichloroaniline (TUtotal = 0.93) and 3,4-dichloroaniline (TUtotal = 1.04). Other three mixtures, Cd combined with 2,5-dichloroaniline, 2,6-dichloroaniline and 2,4,5trichloroaniline showed antagonism. At the medium Cd concentration (0.5 × IC50 ), most binary mixtures show simple addition with TUtotal values ranging from 0.80 to 1.14. Synergism was found for Cd combined with o-chloroaniline (TUtotal = 0.70), m-chloroaniline (TUtotal = 0.74) and p-chloroaniline (TUtotal = 0.73), and no antagonism occurred. At the high Cd concentration (0.8 × IC50 ), most binary mixtures showed simple addition with TUtotal values ranging from 0.80 to 1.20. Antagonism was found for Cd combined with 2,5-dichloroaniline (TUtotal = 1.45), 2,6-dichloroaniline (TUtotal = 1.38) and 2,4,5-trichloroaniline (TUtotal = 1.31). No synergism was observed. Previous studies for a heavy metal and other organisms were taken for comparison. Rodea-Palomares et al. [17] investigated the mixtures of Cd combined with PFOS or PFOA to bioluminescent cyanobacterium Anabaena CPB1337 and found that the interaction between either PFOS or PFOA and Cd was mostly antagonistic. Kungolos et al. [23] studied combined effects of three agrochemicals and copper on Vibrio fischeri, Pseudokirchneriella subcapitata and Daphnia magna, and found that the effects of binary mixtures were

H. Jin et al. / Journal of Hazardous Materials 279 (2014) 156–162

159

Table 2 The descriptors of chlorinated anilines and the relative errors from QSAR models. No.

Compounds

ELUMO

EHOMO − ELUMO

1 2 3 4 5 6 7 8 9 10 11 12 13

o-Chloroaniline m-Chloroaniline p-Chloroaniline 2,3-Dichloroaniline 2,4-Dichloroaniline 2,5-Dichloroaniline 2,6-Dichloroaniline 3,4-Dichloroaniline 2,4,5-Trichloroaniline 2,4,6-Trichloroaniline 3,4,5-Trichloroaniline 2,3,4,5-Trichloroaniline Pentachloroaniline

−0.017 −0.018 −0.019 −0.027 −0.032 −0.227 −0.225 −0.222 −0.230 −0.042 −0.040 −0.048 −0.055

−0.200 −0.201 −0.193 −0.198 −0.190 −0.197 −0.197 −0.192 −0.188 −0.187 −0.191 −0.187 −0.184

a

Relative error (%) Eq. (2)

Eq. (3)

Eq. (4)

Eq. (5)

6.28 2.05 −4.26 −1.47 6.91 −8.67 −8.03 −3.20 8.82 8.16a 10.24a 4.84a 2.49a

3.54 −0.58 −5.88 −3.25 2.49 −5.58 5.33 4.36 −1.86 12.64a 15.46a 12.35a 10.15a

3.90 −4.18 7.57 −5.43 1.83 −8.89 11.71 −7.77 −3.80 5.95a 8.08a 5.75a 4.27a

7.43 6.45 0.36 −12.45 2.78 −7.51 −5.06 −1.58 7.50 4.35a 6.48a 4.16a 2.83a

The IC50 values (mg/L) were predicted by Eqs. (2)–(5).

mainly antagonism and simple addition. Su et al. [20] obtained the similar results when studying the interactive toxic effects of 11 nitroaromatic compounds and copper on P. phosphoreum. The results were consistent with those in the present paper. However, there were some exceptions such as synergistic effects of Cd combined with o-chloroaniline, m-chloroaniline, p-chloroaniline and 2,4-dichloroaniline at the Cd concentration of 0.2 × IC50 and synergism of Cd combined with o-chloroaniline, m-chloroaniline and p-chloroaniline at the Cd concentration of 0.5 × IC50 . The result indicates that the joint toxicity is dependent on the positions where functional groups substituted in the chlorinated anilines besides the Cd concentrations. The complex situation was also recorded in other researches on the joint toxicity of nitroaromatic compounds and copper to P. phosphoreum [20] as well as the combined toxicity of three antifouling biocides and three heavy metals to Chaetoceros gracilis [39]. Since different Cd concentrations resulted in different combined actions of binary mixtures, different QSAR models are necessarily developed and used to assess the ecological risk in the realistic environment. 3.2. QSAR study of the single toxicity of chlorinated anilines

log IC50 = −28.212(EHOMO − ELUMO ) − 4.187 n = 9, R2 = 0.832, 2 SE = 0.0603, F = 34.769, P = 0.001, QLOO = 0.7769,

RMSECV = 0.064

log IC50 = 39.630 ELUMO + 2.585 n = 9, R2 = 0.919, SE = 0.0988, (2)

The only parameter selected in the equation is ELUMO , which reflects the reduction potential of a compound. In other words, the larger the ELUMO value of a compound is, the easier it is for the compound to obtain electrons. The positive coefficient (39.630) indicates that the toxicity of chlorinated anilines increases with the increasing ELUMO value. 3.3. QSAR study of the joint toxicity of chlorinated anilines with Cd Stepwise linear regression method was also used to analyze the joint toxicity of chlorinated anilines with Cd at three combined levels. When Cd was at the low concentration (0.2 × IC50 ), a one-parameter QSAR model (Eq. (3)) was produced by stepwise

(3)

The only parameter selected in Eq. (3) is (EHOMO − ELUMO ), the energy difference, which plays a critical role in determining molecular electrical transport properties and characterizing the molecular chemical stability. For medium and high Cd concentrations (0.5 × IC50 and 0.8 × IC50 ), the same QSAR analysis was performed respectively and lead to the following equations: 0.5 × IC50 of Cd :

log IC50 = −42.770(EHOMO − ELUMO ) − 7.243

n = 9, R2 = 0.837, SE = 0.0900, F = 35.87, P = 0.001, 2 QLOO = 0.7774, RMSECV = 0.094

0.8 × IC50 of Cd :

Twelve physico-chemical descriptors of chlorinated anilines, using the stepwise linear regression method in the statistic package SPSS 17.0, were applied to analyze the single toxic data of nine chlorinated anilines. Only one significant variable (ELUMO ) was selected in the QSAR model. The calculated ELUMO and (EHOMO − ELUMO ) are listed in Table 2. The model is expressed as Eq. (2):

2 F = 79.481, P = 0.000, QLOO = 0.8135, RMSECV = 0.151

regression.

(4)

log IC50 = −55.638(EHOMO − ELUMO ) − 9.791

2

n = 9, R = 0.903, SE = 0.0869, F = 65.18, P = 0.000, 2 QLOO

= 0.8204, RMSECV = 0.107

(5)

It is found from Eqs. (2)–(5) that parameters of electronic properties (ELUMO , EHOMO − ELUMO ) are closely correlated with the toxicity of these aniline derivatives when chlorinated anilines are combined with Cd at any concentration in this study. Compared with Eq. (2), parameter EHOMO is selected into Eqs. (3)–(5) by stepwise regression, which implies that EHOMO as well as ELUMO plays a distinctive role in establishing QSAR models of chlorinated anilines combined with Cd. ELUMO , which reflects the ability of the molecule to accept an electron, describes the electrophilicity of compounds [34]. EHOMO , is a measurement of the ability of a molecule to donate an electron pair, directs the nucleophilic reactivity of a compound. According to the theory of frontal molecular orbitals (FMO), many chemical reactions occur due to attracting interactions between an electron donor and an electron acceptor. The energy difference between HOMO and LUMO levels, expressed as relative hardness index, is often regarded as one of the criteria for stability of aromatic systems [40]. The small value of EHOMO − ELUMO points to high molecular stability and low reactivity. So the reason may be that the orbital of electrons has been changed by the added Cd, decreasing the capability of the lowest unoccupied molecular orbital to attract electrons. For the change of electron orbital,

160

H. Jin et al. / Journal of Hazardous Materials 279 (2014) 156–162

Fig. 2. Computed isodensity surfaces of HOMO and LUMO orbitals for organic cations of these chlorinated anilines. The HOMO stands for the ability to donate an electron, and LUMO represents the ability to obtain an electron. Different colors represent different phases, respectively. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of the article.)

the Van der Waals’ force or complexation between aniline derivatives and Cd ion may account for that. Similar conclusion has been reported that organic compounds could complex with metal ions and thus decrease the total toxicity of the mixtures to aquatic species. Su et al. [20] reported that the complexation between nitroaromatic compounds and copper ion significantly influenced

their joint toxicity toward Photobacterium phosphoreum. Kim et al. [41] determined the combined toxicity of copper ion and phenol derivatives to Daphnia magna, finding that the effect of complexation reaction played an important role in the joint toxicity. In addition, the frontier molecular orbitals (HOMO and LUMO) (Fig. 2) as well as corresponding density of state of the compounds are

H. Jin et al. / Journal of Hazardous Materials 279 (2014) 156–162

161

Table 3 Equations of linear regression and correlation coefficients for the predicted versus experimental values of logIC50 of the test.

R2 y yr0 = k˜ R02 yr0 = k y ˜ R 20

0 × IC50

0.2 × IC50

0.5 × IC50

0.8 × IC50

0.9191 yr0 = 0.9968˜ y 0.9122 yr0 = 1.001y ˜ 0.9214

0.8324 yr0 = 0.9984˜ y 0.799 yr0 = 1.003y ˜ 0.8343

0.8367 yr0 = 0.9955˜ y 0.8057 yr0 = 0.9995y ˜ 0.8471

0.9030 yr0 = 0.9953˜ y 0.8931 yr0 = 0.9998y ˜ 0.9082

y and ˜ y represent the predicted and experimental values of log IC50 for the test, respectively. R2 is the correlation coefficient between y and ˜ y. Regression of y against y or ˜ y against y through the origin (yr0 = k˜ y and ˜ yr0 = k y) were characterized by R02 ˜ and R 20 , respectively.

Fig. 3. Plot of experimental and predicted values of chlorinated anilines from Eq. (2), Eq. (3), Eq. (4) and Eq. (5).

0.5 × IC50Cd , 0.8 × IC50Cd ) also satisfied these conditions, verifying the goodness of fit of the models. In general, the QSAR models developed in this paper are able to predict the joint toxicity of chlorinated anilines whether combined with low, medium concentration or high concentration of Cd very accurately. 4. Conclusion

depicted to illustrate the possible toxic mechanism of these chlorinated anilines. Also, the evaluation of joint toxicity provided support for elucidating the result in this paper. With the increasing concentrations of Cd, the number of synergism of combined actions decreased (4 at the Cd concentration of 0.2 × IC50 , 3 at the Cd concentration of 0.5 × IC50 and 0 at the Cd concentration of 0.8 × IC50 ), while the antagonism number decreased first and then increased (3 at the Cd concentration of 0.2 × IC50 , 0 at the Cd concentration of 0.5 × IC50 and 3 at the Cd concentration of 0.8 × IC50 ). Compared with the joint toxicity of mixtures at low Cd concentration, the toxicity of most binary mixtures was weaker when combined with Cd at medium and high concentrations as indicated by TUTotal . This generally indicates that the joint toxicity is weakened with the increasing concentrations of Cd in the mixtures. Because Cd may form complex with chlorinated aniline and affect the energy of frontal molecular orbital for the latter. As we mentioned before, ELUMO and EHOMO play a distinctive role in establishing QSAR models, i.e., the electrophilicity and nucleophilic reactivity of compound may be changed. Different Cd concentrations contributed to different combined effects, so four QSAR models were developed to assess the potential risk of chlorinated anilines combined with four concentrations of Cd. 3.4. Evaluation of the QSAR models The parameters of chlorinated anilines as well as the relative errors calculated from Eqs. (2)–(5) are listed in Table 2. As is shown in Table 2, 94.44% of relative error values are lower than 10% and all the relative error values remain within 20%. The scatter plot of experimental versus predicted values is shown in Fig. 3 to confirm the robustness of the models. It is obviously found that the predicted values are very close to the experimental ones. The degree of concordance between the predicted (y) and experimental (˜ y) values was also analyzed. The linearity and correlation coefficients are listed in Table 3. As to the equations of linear regression and correlation coefficients for 0 × IC50Cd , R2 = 0.9191, R02 = 0.9122, R 20 = 0.9214, whereas the values of slopes k and k were 0.9968 and 1.001, respectively. The model was considered to be acceptable, because it satisfied the conditions suggested by Golbraikh and Tropsha 2 [42]: QLOO > 0.5, R2 > 0.6, R02 or R 20 close to R2 , and the k and k values were between 0.85 and 1.15. Other models (0.2 × IC50Cd ,

The results of combined toxicity between Cd and nine chlorinated anilines show that the number of chlorinated anilines manifesting synergy with Cd is decreasing as the concentration of Cd increases (4 at the Cd concentration of 0.2 × IC50 , 3 at the Cd concentration of 0.5 × IC50 and 0 at the Cd concentration of 0.8 × IC50 ), and the number manifesting antagonism decreased first and then increased (3 at the Cd concentration of 0.2 × IC50 , 0 at the Cd concentration of 0.5 × IC50 and 3 at the Cd concentration of 0.8 × IC50 ). Compared with the joint toxicity of mixtures at low Cd concentration, the toxicity of most binary mixtures is weaker when combined with Cd at medium and high concentrations as indicated by TUTotal . It indicates that combinations of mixed concentrations may have an effect on the joint action. Since different Cd concentrations contributed to different combined effects, four QSAR models were developed to assess the potential risk of chlorinated anilines combined with four concentrations of Cd. QSAR analysis shows that physico-chemical descriptors are different in the toxicity of chlorinated anilines to P. phosphoreum when Cd exists or not. ELUMO took effect in the toxicity of chlorinated anilines alone, and when Cd was introduced, (EHOMO − ELUMO ) is the main influencing parameter. This implies that Cd has significant influences on the toxicity of chlorinated anilines. The reason may be that the Van der Waals’ force or the complexation between Cd and chlorinated anilines has an impact on the toxicity of combined systems. References [1] N. Dom, D. Knapen, D. Benoot, I. Nobels, R. Blust, Aquatic multi-species acute toxicity of (chlorinated) anilines: experimental versus predicted data, Chemosphere 81 (2010) 177–186. [2] N. Dom, I. Nobels, D. Knapen, R. Blust, Bacterial gene profiling assay applied as an alternative method for mode of action classification: pilot study using chlorinated anilines, Environ. Toxicol. Chem. 14 (2011) 1059–1068. [3] M.W. Falk, S. Wuertz, Effects of the toxin 3-chloroaniline at low concentrations on microbial community dynamics and membrane bioreactor performance, Water Res. 44 (2010) 5109–5115. [4] K. Mochida, K. Ito, H. Harino, A. Kakuno, K. Fujii, Acute toxicity of pyrithione antifouling biocides and joint toxicity with copper to red sea bream (Pagrus major) and toy shrimp (Heptacarpus futilirostris), Environ. Toxicol. Chem. 25 (2006) 3058–3064. [5] J.R. Shaw, T.D. Dempsey, C.Y. Chen, J.W. Hamilton, C.L. Folt, Comparative toxicity of cadmium, zinc, and mixtures of cadmium and zinc to daphnids, Environ. Toxicol. Chem. 25 (2006) 182–189. [6] N.L. Cooper, J.R. Bidwell, A. Kumar, Toxicity of copper, lead, and zinc mixtures to Ceriodaphnia dubia and Daphnia carinata, Ecotoxicol. Environ. Saf. 72 (2009) 1523–1528. [7] M. Faust, R. Altenburger, T. Backhaus, H. Blanck, W. Boedeker, P. Gramatica, V. Hamer, M. Scholze, M. Vichi, L.H. Grimme, Predicting the joint algal toxicity of

162

[8]

[9]

[10]

[11]

[12]

[13]

[14]

[15]

[16]

[17]

[18]

[19]

[20]

[21] [22]

[23]

[24]

[25]

H. Jin et al. / Journal of Hazardous Materials 279 (2014) 156–162 multi-component s-triazine mixtures at low-effect concentrations of individual toxicants, Aquat. Toxicol. 56 (2001) 13–32. M. Faust, R. Altenburger, T. Backhaus, H. Blanck, W. Boedeker, P. Gramatica, V. Hamer, M. Scholze, M. Vichi, L.H. Grimme, Joint algal toxicity of 16 dissimilarly acting chemicals is predictable by the concept of independent action, Aquat. Toxicol. 63 (2003) 43–63. R. Altenburger, M. Nendza, G. Schüürmann, Mixture toxicity and its modeling by quantitative structure–activity relationships, Environ. Toxicol. Chem. 22 (2003) 1900–1915. C.Y. Chen, S.L. Chen, C. Christensen, Individual and combined toxicity of nitriles and aldehydes to Raphidocelis subcapitata, Environ. Toxicol. Chem. 24 (2005) 1067–1073. K.T. Kim, S.J. Klaine, S.J. Lin, P.C. Ke, S.D. Kim, Acute toxicity of a mixture of copper and single-walled carbon nanotubes to Daphnia magna, Environ. Toxicol. Chem. 29 (2010) 122–126. W.P. Norwood, U. Borgmann, D.G. Dixon, A. Wallace, Effects of metal mixtures on aquatic biota: a review of observations and methods, Human Ecol. Risk Assess. 9 (2003) 795–811. I. Sterenborg, N.A. Vork, S.K. Verkade, C.A.M. van Gestel, N.M. van Straalen, Dietary zinc reduces uptake but not metallothionein binding and elimination of cadmium in the springtail, Orchesella cincta, Environ. Toxicol. Chem. 22 (2003) 1167–1171. I.D. Green, K. Walmsley, Time-response relationships for the accumulation of Cu, Ni and Zn by seven-spotted ladybirds (Coccinella septempunctata L.) under conditions of single and combined metal exposure, Chemosphere 93 (2013) 184–189. Z.F. Lin, K.D. Yin, P. Shi, L.S. Wang, H.X. Yu, Development of QSARs for predicting the joint effects between cyanogenic toxicants and aldehydes, Chem. Res. Toxicol. 16 (2003) 1365–1371. Z. Jiang, Z.Y. Zhao, Y.T. Lu, Evaluation of genotoxicity of combined soil pollution by cadmium and phenanthrene on earthworm, J. Environ. Sci. 18 (2006) 1210–1215. ˜ I. Rodea-Palomares, F. Leganés, R. Rosal, F. Fernández-Pinas, Toxicological interactions of perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) with selected pollutants, J. Hazard. Mater. 201–202 (2012) 209–218. P. Wang, L.J. Luo, L. Ke, T.G. Luan, N.F.Y. Tam, Combined toxicity of polycyclic aromatic hydrocarbons and heavy metals to biochemical and antioxidant responses of free and immobilized Selenastrum capricornutum, Environ. Toxicol. Chem. 32 (2013) 673–683. V. Yangali-Quintanilla, A. Sadmani, M. McConville, M. Kennedy, G. Amy, A QSAR model for predicting rejection of emerging contaminants (pharmaceuticals, endocrine disruptors) by nanofiltration membranes, Water Res. 44 (2010) 373–384. L.M. Su, X.J. Zhang, X. Yuan, Y.H. Zhao, D.M. Zhang, W.C. Qin, Evaluation of joint toxicity of nitroaromatic compounds and copper to Photobacterium phosphoreum and QSAR analysis, J. Hazard. Mater. 241–242 (2012) 450–455. G. Shen, Y. Lu, J. Hong, Combined effect of heavy metals and polycyclic aromatic hydrocarbons on urease activity in soil, Ecotox. Environ. Saf. 63 (2006) 474–480. G. Gatidou, N.S. Thomaidis, Evaluation of single and joint toxic effects of two antifouling biocides, their main metabolites and copper using phytoplankton bioassays, Aquat. Toxicol. 85 (2007) 184–191. A. Kungolos, C. Emmanouil, V. Tsiridis, N. Tsiropoulos, Evaluation of toxic and interactive toxic effects of three agrochemicals and copper using a battery of microbiotests, Sci. Total Environ. 407 (2009) 4610–4615. D.Y. Tian, Z.F. Lin, J.Q. Yu, D.Q. Yin, Influence factors of multicomponent mixtures containing reactive chemicals and their joint effects, Chemosphere 88 (2012) 994–1000. T. Abe, H. Saito, Y. Niikura, T. Shigeoka, Y. Nakano, Embryonic development assay with Daphnia magna: application to toxicity of aniline derivatives, Chemosphere 45 (2001) 487–495.

[26] R.J. Qu, X.H. Wang, Z.T. Liu, Z.G. Yan, Z.Y. Wang, Development of a model to predict the effect of water chemistry on the acute toxicity of cadmium to Photobacterium phosphoreum, J. Hazard. Mater. 262 (2013) 288–296. [27] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb, J.R. Cheeseman, G. Scalmani, V. Barone, B. Mennucci, G.A. Peterson, H. Nakatsuji, M. Caricato, X. Li, H.P. Hratchian, A.F. Izmaylov, J. Bloino, G. Zheng, J.L. Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, T. Vreven, J.A. Montgomery Jr., J.E. Peralta, F. Ogliaro, M. Bearpark, J.J. Heyd, E. Brothers, K.N. Kudin, V.N. Staroverov, R. Kobayashi, J. Normand, K. Raghavachari, A. Rendell, J.C. Burant, S.S. Iyengar, J. Tomasi, M. Cossi, N. Rega, J.M. Millam, M. Klene, J.E. Knox, J.B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R.E. Stratmann, O. Yazyev, A.J. Austin, R. Gammi, C. Pomelli, J.W. Ochterski, R.L. Martin, K. Morokuma, V.G. Zakrzewski, G.A. Vorth, P. Salvador, J.J. Dannenberg, S. Dapprich, A.D. Daniels, O. Farkas, J.B. Foresman, J.V. Ortiz, J. Cioslowski, D.J. Fox, Gassian 09 Revision A. 02, Gaussian Inc., Wallingford, CT, 2009. [28] A.D. Becke, Density-function exchange-energy approximation with correct asymptotic behavior, Phys. Rev. A 38 (1988) 3098–3100. [29] C. Lee, W. Yang, R.G. Parr, Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density, Phys. Rev. B 37 (1988) 785–789. [30] X.M. Sun, T.L. Sun, Q.Z. Zhang, W.X. Wang, Degradation mechanism of PCDDs initiated by OH radical in Photo-Fenton oxidation technology: Quantum chemistry and quantitative structure–activity relationship, Sci. Total Environ. 402 (2008) 123–129. [31] X.H. Qu, H. Wang, Q.Z. Zhang, X.Y. Shi, F. Xu, W.X. Wang, Mechanistic and kinetic studies on the homogeneous gas-phase formation of PCDD/Fs from 2,4,5-trichlorophenol, Environ. Sci. Technol. 43 (2009) 4068–4075. [32] J.Q. Shi, R.J. Qu, A. Flamm, H.X. Liu, Y. Xu, Z.Y. Wang, Environment-related properties of polyhydroxylated dibenzo-p-dioxins, Sci. Total Environ. 414 (2012) 404–416. [33] M. Karelson, V.S. Lobanov, A.R. Katritzky, Quantum-chemical descriptors in QSAR/QSPR studies, Chem. Rev. 96 (1996) 1027–1043. [34] A.E.M.F. Soffers, M.G. Boersma, W.H.J. Vaes, J. Vervoort, B. Tyrakowska, J.L.M. Hermens, I.M.C.M. Rietjens, Computer-modeling-based QSARs for analyzing experimental data on biotransformation and toxicity, Toxicol. In Vitro 15 (2001) 539–551. [35] P. Gramatica, Principles of QSAR models validation: internal and external, QSAR Comb. Sci. 26 (2007) 694–701. [36] T. Puzyn, N. Suzuki, M. Haranczyk, How do the partitioning properties of polyhalogenated POPs change when chlorine is replaced with bromine? Environ. Sci. Technol. 42 (2008) 5189–5195. [37] S. Xu, N. Nirmalakhandan, Use of QSAR models in predicting joint effects in multi-component mixtures of organic chemicals, Water Res. 32 (1998) 2391–2399. [38] S.J. Broderius, M.D. Kahl, M.D. Hoglund, Use of joint response to define the primary mode of toxic action for diverse industrial organic chemicals, Environ. Toxicol. Chem. 14 (1995) 1591–1605. [39] A. Koutsaftis, I. Aoyama, The interactive effects of binary mixtures of three antifouling biocides and three heavy metals against the marine algae Chaetoceros gracilis, Environ. Toxicol. 21 (2006) 432–439. [40] T.I. Netzeva, A.O. Aptula, S.H. Chaudary, J.C. Duffy, T.W. Schulz, G.D. Cronin, M.Y. Schüürmann, Structure–activity relationships for the toxicity of substituted poly-hydroxylated benzenes to Tetrahymena pyriformis: influence of free radical formation, QSAR Comb. Sci 22 (2003) 575–582. [41] K.T. Kim, Y.G. Lee, S.D. Kim, Combined toxicity of copper and phenol derivatives to Daphnia magna: effect of complexation reaction, Environ. Int. 32 (2006) 487–492. [42] A. Golbraikh, A. Tropsha, Beware of q2!, J. Mol. Graph. Model 20 (2002) 269–276.

Evaluation on joint toxicity of chlorinated anilines and cadmium to Photobacterium phosphoreum and QSAR analysis.

The individual IC50 (the concentrations causing a 50% inhibition of bioluminescence after 15min exposure) of cadmium ion (Cd) and nine chlorinated ani...
1MB Sizes 1 Downloads 3 Views