Investigating the quantitative structure-activity relationships for antibody recognition of two immunoassays for polycyclic aromatic hydrocarbons by multiple regression methods.

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous contaminants found in the environment. Immunoassays represent useful analytical methods to complement traditional analytical procedures for PAHs. Cross-reactivity (CR) is a very useful character to evaluate the extent of cross-reaction of a cross-reactant in immunoreactions and immunoassays. The quantitative relationships between the molecular properties and the CR of PAHs were established by stepwise multiple linear regression, principal component regression and partial least square regression, using the data of two commercial enzyme-linked immunosorbent assay (ELISA) kits. The objective is to find the most important molecular properties that affect the CR, and predict the CR by multiple regression methods. The results show that the physicochemical, electronic and topological properties of the PAH molecules have an integrated effect on the CR properties for the two ELISAs, among which molar solubility (S(m)) and valence molecular connectivity index ((3)χ(v)) are the most important factors. The obtained regression equations for Ris(C) kit are all statistically significant (p < 0.005) and show satisfactory ability for predicting CR values, while equations for RaPID kit are all not significant (p > 0.05) and not suitable for predicting. It is probably because that the Ris(C) immunoassay employs a monoclonal antibody, while the RaPID kit is based on polyclonal antibody. Considering the important effect of solubility on the CR values, cross-reaction potential (CRP) is calculated and used as a complement of CR for evaluation of cross-reactions in immunoassays. Only the compounds with both high CR and high CRP can cause intense cross-reactions in immunoassays.

Effects of nitrite and toxic Microcystis aeruginosa PCC7806 on the growth of freshwater rotifer Brachionus calyciflorus.

Over the last two centuries, anthropogenic activities have increased the nitrogen amount in aquatic ecosystems, which has resulted in increased occurrences of blooms of cyanobacteria. This study investigated the effects of nitrite and the cyanobacterium Microcystis aeruginosa on population growth in the rotifer Brachionus calyciflorus. The rotifer was treated for 12 days with nitrite alone (medium containing 0, 3, 6, 10 mg NO (2)(-) -N L(-1)), M. aeruginosa alone (medium containing 0 mg NO(2)(-)-N L(-1) + 5.0 × 10(5) cell ml(-1) M. aeruginosa precultured at 0, 3, 6, 10 mg NO(2)(-)-N L(-1)), and nitrite in combination with M. aeruginosa (medium containing 3, 10 mg NO(2)(-)-N L(-1) + 5.0 × 10(5) cell ml(-1) M. aeruginosa precultured at corresponding nitrite concentrations). We observed that a nitrite concentration of 10 mg NO(2)(-)-N L(-1) markedly inhibited the growth of B. calyciflorus; however, rotifer growth declined slightly in the presence of M. aeruginosa precultured at 6 mg NO(2)(-)-N L(-1). Furthermore, reduced population growth of B. calyciflorus was observed when it was treated with both nitrite and M. aeruginosa compared to nitrite alone or M. aeruginosa alone. These results suggested that a high tolerance of B. calyciflorus to nitrite levels may be attributed to the absence of specific respiratory structures and pigments; and that the increased toxicity of nitrite in combination with M. aeruginosa may have been due to increased production of microcystin. It is also possible that nitrite and microcystin could act in a synergistic way in causing toxicity.

[Mechanism study on the extraction of nonylphenol by ionic liquids in water through IR spectroscopy and quantum chemical calculation].

The interaction mechanism of the typical ionic liquid (IL) 1-methyl-3-butyl imidazolium hexafluorophosphate ([BMIM][PF6]), imidazolium ionic liquid with hydroxyl group and nonylphenol (NP) was studied through infrared (IR) spectroscopy and quantum chemical calculations for density functional theory. The results indicated the hydrogen bonds could not be found in the IR spectra before and after IL [BMIM][PF6] extracting NP while the absorption peaks of the hydroxyl group of the ILs containing hydroxyl group have red shifts after the ILs extracting NP. It could be seen in the theoretical calculation that the cation [BMIM]+ of [BMIM][PF6] has the C--H...O hydrogen bond interaction with NP. The O--H...O type hydrogen bond could also be formed between the cation [C4H9OHIM]+ of the IL with hydroxyl group and NP. It could be concluded through the two mechanism study methods that the strength of hydrogen bond between the IL with hydroxyl group and NP was bigger than the one between the typical IL [BMIM][PF6] and NP, followed by the bigger extraction efficiency of NP by the former, which coincided with the extraction experiment result.

Predicting the cross-reactivities of polycyclic aromatic hydrocarbons in ELISA by regression analysis and CoMFA methods.

Immunoassays have been regarded as a possible alternative or supplement for measuring polycyclic aromatic hydrocarbons (PAHs) in the environment. Since there are too many potential cross-reactants for PAH immunoassays, it is difficult to determine all the cross-reactivities (CRs) by experimental tests. The relationship between CR and the physical-chemical properties of PAHs and related compounds was investigated using the CR data from a commercial enzyme-linked immunosorbent assay (ELISA) kit test. Two quantitative structure-activity relationship (QSAR) techniques, regression analysis and comparative molecular field analysis (CoMFA), were applied for predicting the CR of PAHs in this ELISA kit. Parabolic regression indicates that the CRs are significantly correlated with the logarithm of the partition coefficient for the octanol-water system (log K(ow)) (r(2) = 0.643, n = 23, P < 0.0001), suggesting that hydrophobic interactions play an important role in the antigen-antibody binding and the cross-reactions in this ELISA test. The CoMFA model obtained shows that the CRs of the PAHs are correlated with the 3D structure of the molecules (r(cv)(2) = 0.663, r(2) = 0.873, F(4,32) = 55.086). The contributions of the steric and electrostatic fields to CR were 40.4 and 59.6%, respectively. Both of the QSAR models satisfactorily predict the CR in this PAH immunoassay kit, and help in understanding the mechanisms of antigen-antibody interaction.

Sediment-porewater partition of nonylphenol polyethoxylates: field measurements from Lanzhou Reach of Yellow River, China.

Nonylphenol polyethoxylates (NPnEO) and nonylphenol (NP) have drawn much environmental concern because of their weak estrogenic activities. The present study focused on the spatial distribution of NPnEO and NP in surface sediments and their corresponding porewaters along Lanzhou Reach of Yellow River, China. Long EO chain NPnEO analogs with n > 2 were not measurable in most sediment and porewater samples, so only NP, nonylphenol monoethoxylate (NP1EO) and nonylphenol diethoxylate (NP2EO) were discussed in this study. Concentrations of NP, NP1EO, and NP2EO in the sediments ranged from 61.3 to 113.9, 31.1 to 55.9, and 47.9 to 74.1 ng/g dry weight, respectively. A significant correlation (R2= 0.56, p < 0.01) was observed between NP levels and organic carbon content of the sediments, whereas no correlation was found for the more hydrophilic NP1EO and NP2EO. The concentrations of NP, NP1EO, and NP2EO in the porewaters ranged from 0.35 to 1.95, 0.06 to 0.63, and 0.08 to 0.38 microg/L. The mean in situ log K(oc) values (n = 13, S1 excluded) of NP, NP1EO, and NP2EO were 4.48, 4.94, and 5.06, respectively, which were lower than those measured in batch adsorption experiments.

Application of Markov model to environmental fate of phenanthrene in Lanzhou Reach of Yellow River.

The theory of Markov Chain is used scientifically to describe the transfer/transformation of phenanthrene in Lanzhou Reach of Yellow River. In Markov Model (MM), the states of phenanthrene in Lanzhou Reach are divided into six different states, namely being degraded, leaving the system with the addvective flow, being in air, being in water, being adsorbed on suspending substances (SS), and being in bottom sediment (BS). The MM is simulated by using Matlab6.5 to reveal the temporal changes and environmental fate of phenanthrene in Lanzhou Reach. It is shown that the environmental system will be steady in 30,000-35,000 h, the final distributions of phenanthrene in air, water, SS, and BS are 23,033 kg, 1961 kg, 800 kg, and 2824 kg respectively, with the corresponding percent of 80%, 7%, 3%, and 10%. The results of MM are approximate to the results of Fugacity Model (FM), so Markov Chain can be used to evaluate the environmental fate of pollutants in multimedia environment. The outputs of MM include the following aspects: (1) The residual time of pollutant in different environmental media and the transiting time of pollutant between different environmental media; (2) The response time of the environmental system; (3) The total mass of pollutant transferred or degraded during a given time interval; (4) The time needed for the environmental system to be steady and the final steady distributions of pollutant in the environmental system.

Polycyclic aromatic hydrocarbons in the surface sediments from Yellow River, China.

Fourteen surface sediment samples were collected from Lanzhou Reach of Yellow River, China in July 2005. The concentrations of 16 priority polycyclic aromatic hydrocarbons (PAHs) were determined by gas chromatography equipped with a mass spectrometry detector (GC-MS). Total concentrations of the PAHs ranged from 464 to 2621 ng/g dry weight. Sediment samples with the highest PAH concentrations appeared at the downstream of Lanzhou City, where there was the biggest wastewater discharge pipeline from Lanzhou Oil Refinery Factory and Lanzhou Chemical Industry Company. Municipal sewage also contributed to the PAH contamination in the sediments. A correlation existed between the sediment organic carbon content (f(oc)) and the total PAH concentrations (r(2)=0.57), suggesting that sediment organic carbon content played an important role in controlling the PAHs levels in the sediments. According to the observed molecular indices, PAHs contamination in Lanzhou Reach of Yellow River originated both from the high-temperature pyrolytic processes and from the petrogenic source, showing a mixed PAH input pattern, which was also confirmed by the results of a principal component analysis (PCA). According to the numerical effect-based sediment quality guidelines (SQGs) of the United States, the levels of PAHs at most studied sites in Lanzhou Reach of Yellow River should not exert adverse biological effects. Although at some sites (such as S10, S12, etc.) one PAH may exceed the effects range low (ERL), individual PAH did not exceed the effects range median (ERM). The results indicated that sediments in all sites should have potential biological impact, but should have no impairment.

Source analysis of particulate-phase polycyclic aromatic hydrocarbons in an urban atmosphere of a northern city in China.

Particle-associated polycyclic aromatic hydrocarbon (PAH) concentrations were investigated at six sampling sites in the heating (February to March 2001) and nonheating (August to September 2001) periods in an industrial city in Northern China. Thirteen PAHs were measured. The total average concentrations (nanograms per meter cubed) of PAHs ranged between 78.93 and 214.63 during the heating period and from 31.48 to 102.26 in the nonheating period. Benzo(a)pyrene occurred at the highest level at a site near an industrial area but occurred at low concentrations far from the city center and industrial areas. In addition, ambient PAH profiles were studied. The five and six-ring species occurred in high fractions at the sampling site. By diagnostic ratio analysis, the major source at each sampling site in the city was coal combustion in the heating period; in the nonheating period, the major sources were relatively complex. Finally, the similarities among the six regions were assessed by principal component analysis, cluster analysis, and coefficient of divergence. These multivariate statistical analyses produced similar results, which agreed with the results from the diagnostic ratio analysis.

Impact of atrazine and nitrogen fertilizers on the sorption of chlorotoluron in soil and model sorbents.

Sorption of chlorotoluron in ammonium sulfate, urea and atrazine multi-solutes system was investigated by batch experiments. The results showed application of nitrogen fertilizers to the soil could affect the behavior of chlorotoluron. At the same concentration of N, sorption of chlorotoluron decreased as the concentration of atrazine increased on the day 0 and 6 in soil, respectively. The sorption of chlorotoluron increased from 0 to 6 d when soils were preincubated with deionized water, ammonium sulfate and urea solution for 6 d. That indicated incubation time was one of the most important factors for the sorption of chlorotoluron in nitrogen fertilizers treatments. The individual sorption isotherms of chlorotoluron in rubbery polymer and silica were strictly linear in single solute system, but there were competition sorption between pesticides or between pesticides and nitrogen fertilizers. That indicated the sorption taken place by concurrent solid-phase dissolution mechanism and sorption on the interface of water-organic matter or water-mineral matter.

Distribution and dissipation pathways of nonylphenol polyethoxylates in the Yellow River: Site investigation and lab-scale studies.

Spatial distribution of nonylphenol polyethoxylates (NPEOs) and nonylphenol (NP) was investigated in a field study in Lanzhou Reach of the Yellow River. NPEOs and their metabolites were found in the river, with the maximum dissolved concentrations of 6.38 nmol/L for NPEOs, 0.19 nmol/L for nonylphenol ethoxy acetic acids (NPECs) and 0.79 nmol/L for NP, respectively. The maximum concentrations in the sediment and suspended particle samples were 1.50 and 5.09 nmol/g for NPEOs and NP, respectively. The effects of particles, light and microorganism on the dissipation of NPEOs in the river water were investigated based on lab-scale experiments. When natural particles were removed, 72% and 22% degradation of NPEOs were achieved at 120 h in non-sterile and sterile conditions with light, respectively. Different concentrations of NPECs were also observed in these experiments. When suspended particle matters (SPMs) were present, about 38-50% of NPEOs were sorbed to the particulate phase in only 1 h. As a result, the degradation of NPEOs and production of NPECs were inhibited. However, the combined sorption and degradation in the presence of SPMs resulted in lower dissolved NPEO concentrations than those in the absence of SPMs. Biodegradation was the most important pathway for NPEOs degradation in the river water, while NPECs seemed to be produced through both biological and abiological pathways.

Effect of surfactants on desorption of aldicarb from spiked soil.

Surfactant enhanced desorption of aldicarb from spiked soil was investigated in this paper. Anionic (sodium dodecyl benzene sulphonate, SDBS), cationic (hexadecyl trimethyl ammonium bromide, HTAB) and nonionic (octyl polyethylene glycol phenyl ether, OP) surfactants were tested to determine their optimal desorption conditions including desorption time, mixing speed and surfactant concentrations. The results showed that the optimal operating conditions were obtained at 2 h, 150 rpm, and surfactants concentrations were 1000, 100, and 200 mg l(-1) for SDBS, OP, and HTAB, respectively. The paper also investigated the desorption efficiency of mixture of different kinds of surfactants for aldicarb-spiked soil, and found that anionic-nonionic surfactant mixtures gave the best desorption efficiency up to 77%, while anionic-cationic surfactant mixture gave a poor desorption efficiency similar to water, suggesting that mixture of anionic-nonionic surfactants were highly promising on remediation of aldicarb-contaminated soil.

Seasonal and spatial distribution of nonylphenol in Lanzhou Reach of Yellow River in China.

Nonylphenol (NP) is known as an endocrine disruptor and consequently has drawn much environmental concern. This study focused on seasonal variation and spatial distribution of NP in various matrices including water, suspended particles, and sediment taken from Lanzhou Reach of Yellow River in China. NP was measured in July and November in 2004. Concentrations of NP in water ranged from 34.2 to 599.0 ng/l, in suspended particles from 49.6 to 2835.2 ng/g dry wt, and in sediment from 38.4 to 863.0 ng/g dry wt. In terms of most water and suspended particles samples, concentrations were higher in warmer seasons than in colder seasons. Good linear correlations (R(2)=0.90 in July, R(2)=0.97 in November) were obtained for NP concentrations between water and suspended particles. In terms of sediment samples, concentrations were higher in November than in July, probably due to greater deposition of suspended particles. Reasonable linear correlations (R(2)=0.60 in July, R(2)=0.79 in November) were obtained for NP concentrations between water and sediment.

Ionic liquid-containing semipermeable membrane devices for monitoring the polycyclic aromatic hydrocarbons in water.

Ionic liquid-containing semipermeable membrane devices (IL-SPMDs) were developed to monitor the polycyclic aromatic hydrocarbons in water. Uptake kinetics of naphthalene, 1-methylnaphthalene, phenanthrene, pyrene, chrysene by layflat low-density polyethylene tubing (15 cm x 2 cm) filled with 0.5 ml 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid were studied in a laboratory continuous-flow system for the duration of 16 days. The device concentration factors were in the range of 830-7800 for the studied PAHs. The kinetic parameters of IL/water partition coefficients, analytes uptake rate constants and sampling rates were estimated using mathematical models. These parameters were used in the field experiment to estimate the concentrations of the PAHs in Lanzhou section of Yellow River in China, with the result in comparison with that obtained by triolein-SPMD.

Influences of copper speciation on toxicity to microorganisms in soils.

OBJECTIVE: To investigate the relationship between copper speciation and microbial features (microbial communities and copper tolerance level) in order to determine the adverse effect of different forms of Cu on microorganisms. METHODS: Tessier's sequential extraction procedure was used to qualify the different Cu forms (exchangeable, carbonate bound, Fe/Mn oxide bound, residue and organic matter bound), and the copper tolerance level (expressed as IC50, influence concentration) was measured by the plate-count method. RESULTS: By simple correlation analysis, the IC50 was positively correlated with the concentration of exchangeable Cu (R2 = 0.8204), while weakly correlated with other forms of Cu. CONCLUSION: The bacterial community tolerance increases in the copper-contaminated soil while sensitive bacteria decrease in the copper-contaminated soils. The exchangeable Cu exerts high toxicity to microbial communities.

Plant uptake of aldicarb from contaminated soil and its enhanced degradation in the rhizosphere.

Experiments were conducted to investigate the degradation of aldicarb, an oxime carbamate insecticide, in sterile, non-sterile and plant-grown soils, and the capability of different plant species to accumulate the pesticide. The degradation of aldicarb in soil followed first-order kinetics. Half lives (t1/2) of aldicarb in sterile and non-sterile soil were 12.0 and 2.7 days, respectively, which indicated that microorganisms played an important part in the degradation of aldicarb in soil. Aldicarb disappeared more quickly (p< or =0.05) in the soil with the presence of plants, and t1/2 of the pesticide were 1.6, 1.4 and 1.7 days in the soil grown with corn, mung bean and cowpea, respectively. Comparison of plant-promoted degradation and plant uptake showed that the enhanced removal of aldicarb in plant-grown soil was mainly due to plant-promoted degradation in the rhizosphere.

Sediment-porewater partition of polycyclic aromatic hydrocarbons (PAHs) from Lanzhou Reach of Yellow River, China.

Pollution of polycyclic aromatic hydrocarbons (PAHs) in the aquatic environment has drawn much attention around the world. The occurrence of 16 priority PAHs in the sediments and corresponding porewaters in Lanzhou Reach of Yellow River, China, and their partitioning behavior between the two phases were investigated. The results demonstrated that the total PAH levels in the sediments were positively correlated with the sediment clay contents (R(2)=0.756). Concentrations of total PAHs in porewaters ranged from 48.2 to 206 microg/L, and indeno[1,2,3-cd]pyrene (InP) was the most abundant compound measured in the porewater samples with a mean value of 42.9 microg/L. The compositions of PAHs in porewaters were dominated by their compositions in the sediment samples. The in situ organic carbon normalized partition coefficients logK(oc)(') of the PAHs between sediments and porewaters were significantly correlated with their octanol-water partition coefficients (logK(ow)) when logK(ow) values were less than 5.5 (naphthalene (Nap) excluded). logK(oc)(') values of 14 PAHs were lower than those predicted by the Karickhoff relationship. This discrepancy was largest for InP, dibenzo[a,h]anthracene (DBA), and benzo[ghi]perylene (BgP). The results in present study showed the tendency of PAHs release from sediment to porewater, indicating that PAHs sequestered in the sediments may be a pollution source to aquatic ecosystem.

[Photodegradation of nonylphenol polyethoxylates in aqueous solution].

Two lamps, including simulated sunlight lamp and UVA-365 nm lamp, were used to study the kinetics and changes of component distribution of NPEOs mixture in solution during photodegradation, as well as the effect of H2O2 on the photodegradation. LC-MS was used to analyze the products of NPEOs photodegradation. It was found that photodegradation of NPEOs occurred under both simulated sunlight and UVA irradiation, with the degradation rate being 6.20 x 10(-3) micromol/(L x h) and 1.18 x 10(-2) micromol/(L x h), respectively. The component distribution of short chain NPEO(1,3) increased during the photodegradation process under simulated sunlight, while no obvious change was observed under UVA irradiation. The presence of the oxidant, H2O2, was found to be propitious to the photodegradation of NPEOs, especially under the irradiation of simulated sunlight. At different added concentrations of H2O2, the 96 h degradation percentage of NPEOs increased from 20.9% (non-H2O2) to 44.4% (0.01 mmol/L H2O2) and even 91.5% (1.00 mmol/L H2O2), respectively. The analysis for degradation products using LC-MS suggested that CA(3-9)PEC3 might he the major photodegradation products of NPEOs, based on which the reaction mechanism of NPEOs photodegradation was speculated.

[Changes of algal communities in water body with different proportions of nitrogen and phosphorus].

A simulation test was conducted in aquaria to study the responses of algal communities to different N/P ratios in urban water body. The water sample was taken from a small artificial lake in Tianjin, and its initial N/P ratio was adjusted to 0. 5:1,7.2:1, 25:1 and 50:1, respectively. The results showed that in high N/P ratio groups, the numbers of Chlorophyta species decreased, while those of Cyanophyta species didn' t change very much. The numbers of these two species were both decreased in low N/P ratio group. Algal biomass, cell density and chlorophyll a content in medium and high N groups were higher than those in control and high P groups. The mean value of chlorophyll a reached the highest (69.7 microg x L(-1)) in high N group, and was 54.3, 30.3 and 29.7 microg x L(-1) in medium N, control, and high P groups, respectively. At the mid-late stages of culture, green algae Dictyosphaerium pulchellum was dominant in high P group, while blue algae Phormidium tenue, P. corium, Lyngbya limnetica and Microcystis aeruginosa were dominated in high N/P ratio groups. Control group had the highest species richness, while medium and high N groups had the highest and lowest ecological species dominance, respectively.

[Effects of nitrogen source and aeration mode on algae growth in freshwater].

Aquarium microcosms were used to study the effects of nitrogen source and aeration mode on the growth and species changes of algae in freshwater. Nitrate nitrogen(NO3(-) -N) and ammonia nitrogen(NH4(+) -N) were used as nitrogen sources. For each nitrogen source, four modes of aeration were selected, including control, continuous aeration, aeration during the day, and aeration at night. In the early stage of the experiment, algae in the NH4(+) -N treatment experiment grew well. In the later stage, algae in the NO3(-) -N treatment experiment grew better. For different aeration modes, continuous aeration show varied effects on algae growth in the two nitrogen source treatments. Day-only aeration had little effect on algae growth. Night-only aeration inhibited algae growth considerably. In NH(+) -N treatments, cyanophyta became dominant species easily. In contrast, chlorophyta dominated in NO3(-) -N treatments.

[Impact of aldicarb and its complex pollution on DNA of zebrafish embryo].

This paper deals with the impact of a complex pollution system composed of a very toxic carbamate pesticide, aldicarb and the widely used anionic surfactant, sodium dodecylbenzenesulfonate(SDBS), on DNA of zebrafish (Brachydanio rerio) embryo. The results indicated that DNA damage caused by aldicarb became more serious with its increasing concentration, but single-strand break caused by aldicarb in low concentration and short time could be repaired, and high concentration led to double-strand break which was difficult to repaire. SDBS in certain concentration (20 mg.L-1) could reduce the toxicity of aldicarb in the complex pollution system.