A comparative study of biodegradability of a carcinogenic aromatic amine (4,4'-diaminodiphenylmethane) with OECD 301 test methods.

4,4'-Diaminodiphenylmethane (MDA) is a widely used compound in industries. Studies on the biodegradability of MDA are necessary for environmental hazard identification and risk assessment. Previous studies have suggested that MDA was not readily biodegradable. In the present study, three batches of biodegradation tests (OECD 301A, B, D and F tests) were performed on MDA in June, August and December of 2012. MDA was found to be readily biodegradable and produced colored intermediates in the 301A, B and F test systems. MDA biodegradation measurements were consistent among the three batches of tests. Differences in the extent of biodegradation determined in different methods originated from different test conditions and assessment endpoints. The 301D test has stringent test conditions and is usually performed on chemicals that are toxic to microorganisms, so the test results obtained from 301D tests are less meaningful for evaluating the biodegradability of MDA. The low MDA biodegradation measurements in the 301B tests compared to the 301A and F tests were due to the assessment method, which did not account for MDA incorporation into biomass in its calculation of CO2 formation rate. The differences in the biodegradation rates, as measured by the different OECD 301 test systems, could also be related to the structure and properties of the chemical. For test substances that can be assessed by all OECD 301 test methods, the highest biodegradation values may be obtained from the 301A and F test methods. This study provides new information to assess the environmental fate in the risk assessment of MDA.

[Characteristics and Ecological Risk Assessment of Pharmaceutical Active Compounds in Guangdong Province].

Pharmaceutically active compounds(PhACs) have become a class of new pollutants in the environment after extensive production and use of PhACs in China. To investigate the pollution characteristics of PhACs in Guangdong Province, raw sewage was collected from 186 sewage treatment plants in 21 cities, including 178 townships and administrative districts in Guangdong Province. The pollution levels of ten typical PhACs in influent water of sewage treatment plants were analyzed using automatic solid phase extraction and high performance liquid chromatography-triple quadrupole mass spectrometry. The spatial distribution characteristics of PhACs in Guangdong Province were fully revealed, and the potential ecological risks of PhACs were evaluated. The results showed that PhACs were detected in all wastewater plants, and the mass concentration of PhACs ranged from 21.00 to 9558.25 ng·L-1. Metoprolo, acetaminophen, bezafibrate, and caffeine were the main pollutants. In terms of spatial distribution, the average mass concentration of ΣPhACs in various regions of Guangdong Province was in the following order:Pearl River Delta>North Guangdong>East Guangdong≈West Guangdong. When the mass concentration of ΣPhACs was over 2500 ng·L-1 in the influent water of sewage treatment plants, the concentration of PhACs in effluent was estimated according to the sewage disposal technology. The ecological risk of PhACs was carried out based on the effluent. The results revealed that the ecological risk of PhACs was low in Guangdong Province, and the risk of bezafibrate was moderate in the cities of Shaoguan, Jiangmen, and Shenzhen. The highest ecological risk of ΣPhACs was located in Shaoguan.

Toxicity of bisphenol A and its bioaccumulation and removal by a marine microalga Stephanodiscus hantzschii.

The toxicity of bisphenol A (BPA) to Stephanodiscus hantzschii, a diatom isolated from tidal water of Futian Mangrove Nature Reserve, China, and the bioaccumulation and removal capability of the marine microalga to BPA were investigated in the present study. Toxicity experiments showed that the 96-h EC50 of BPA was 8.65+/-0.26 mg/L, and the cell number and chlorophyll a content of S. hantzschii decreased significantly with increases in BPA at concentrations higher than 3.00 mg/L. S. hantzschii had high removal capability at low BPA concentrations as BPA was bioaccumulated and biodegraded by cells. After 16-day treatment, 88%, 99%, 92%, 61%, 48%, 28% and 26% of BPA were removed by the diatom in the media supplemented with 0.01, 0.10, 1.00, 3.00, 5.00, 7.00 and 9.00 mg/L BPA, respectively. The present study demonstrated that S. hantzschii was a tolerant isolate that could be used to remove BPA from contaminated waters.

Different bacterial groups for biodegradation of three- and four-ring PAHs isolated from a Hong Kong mangrove sediment.

Mangrove sediments have been found to degrade three- to four-ring PAHs extensively. In the present study, 11 strains from 4 genera Mycobacterium (3 strains), Sphingomonas (5), Terrabacter (2) and Rhodococcus (1) were isolated from a single surface sediment sample of a Hong Kong mangrove swamp, among which the Terrabacter strains were isolated to grow with fluoranthene for the first time. Although all four genera could degrade three- and four-ring PAHs, their in situ activities in natural sediment slurry were found to be different. A cultivable method showed that Sphingomonas strains grew rapidly under the induction of three-ring, but not four-ring PAHs, while only Mycobacterium degrading strains dominated in the four-ring PAHs spiked slurry. Culture-independent method using a reverse transcriptional PCR showed expressions of nahAc-like (mainly found in Gram-negative bacteria) and nidA-like (in Gram-positive bacteria) dioxygenase genes parallel with the degradation of three- and four-ring PAHs, respectively. The present study suggested that surface mangrove sediments harbored diverse PAH-degrading bacteria, which showed different importance for biodegradation of three- and four-ring PAHs in the sediment.

Distribution patterns of octylphenol and nonylphenol in the aquatic system at mai po marshes nature reserve, a subtropical estuarine wetland in Hong Kong.

Spatial and temporal distribution of octylphenol (OP) and nonylphenol (NP) in Mai Po Marshes, a subtropical estuarine wetland in Hong Kong, were investigated. Surface water samples were collected every month from 11 sites during the period of September-December 2004. Concentrations of OP and NP ranged from 11.3 to 348 ng/L and from 29 to 2591 ng/L, respectively. The high levels of NP and OP were found in November and December than in September and October. The levels of OP and NP have no significant spatial differences except September. Total organic matter in the sediments appeared to be an important factor in controlling the fate of these compounds in the aquatic environment.

Vitamin D3 induces vitamin D receptor and HDAC11 binding to relieve the promoter of the tight junction proteins.

Intestinal epithelial barrier dysfunction and vitamin D (VitD)-deficiency play a critical role in a large number of diseases. The histone deacetylases (HDAC) are associated with a large number of immune diseases. This study tests a hypothesis that the interaction between VitD and HDAC is associated with the regulation of epithelial barrier functions. In this study, human intestinal epithelial cell line, T84 cells, was cultured into monolayers to be used as a model to test the epithelial barrier functions. We observed that in a VitD-deficient environment, the T84 monolayer barrier function was compromised. Exposure to calcitriol (the active form of VitD3) in the culture increased the expression of VitD receptor (VDR) in T84 cells. In a VitD-sufficient environment, VDR formed a complex with histone deacetylase-11 (HDAC11); the complex was markedly decreased in a VitD-deficient environment. We also observed that significantly more binding of HDAC11 to the promoter of the tight junction proteins inhibit the gene transcription activities of these loci in the VitD-deficient environment, which were abolished by the presence of calcitriol in the culture. In conclusion, the interaction between VDR and HDAC11 plays a crucial role in the maintenance of the epithelial barrier integrity.

Dependence of bisphenol A photodegradation on the initial concentration of oxalate in the lepidocrocite-oxalate complex system.

To understand the degradation of endocrine disrupting chemicals (EDCs) in natural environment with existence of iron oxides and carboxylic acids, the dependence of bisphenol A (BPA) photodegradation on the initial concentration of oxalate (COX) in lepidocrocite (gamma-FeOOH) aqueous suspension was investigated under both UV and visible lights in this study. Lepidocrocite powder was home-prepared by a hydrothermal process. It was found that BPA degradation was promoted greatly in the presence of oxalate owing to the formation of lepidocrocite-oxalate complex. And there was an optimal COX, which was 2.0 and 2.4 mmol/L, under UV and visible lights, respectively. The first-order kinetic constant, k value increased 38 times from 0.17 x 10(-2) min(-1) in the absence of oxalate to 6.39 x 10(-2) min(-1) in the presence of oxalate with an optimal COX (2.0 mmol/L) under UV irradiation, and almost 306 times from 0.02 x 10(-2) min(-1) in the absence of oxalate to 6.11 x 10(-2) min(-1) in the presence of oxalate with an optimal COX (2.4 mmol/L) under visible irradiation. The BPA degradation rate increased and the first-order kinetic constants decreased with the increase in BPA initial concentration. The dependence of the variation of pH value, total-Fe and Fe2+ during the photoreaction on COX was also investigated. The pH value increased obviously with the reaction time. Total-Fe increased dramatically at the first 5 min and then decreased quickly under UV irradiation and slowly under visible irradiation. The initial concentration of oxalate is a main factor to affect BPA photodegradation in aqueous suspension under both UV and visible lights.

Crystal structure of 4,4',4''-(1,3,5-triazine-2,4,6-tri-yl)tripyridinium trichloride 2.5-hydrate.

The asymmetric unit of the title compound, C18H15N6 (3+)·3Cl(-)·2.5H2O, contains two independent (1,3,5-triazine-2,4,6-tri-yl)tripyridinium cations. Both cations are approximately planar, the r.m.s. deviations of fitted non-H atoms being 0.045 and 0.051 Å. In the crystal, extensive O-H⋯Cl, O-H⋯O, N-H⋯Cl and N-H⋯O hydrogen bonds and weak C-H⋯Cl and C-H⋯O inter-actions link the organic cations, Cl(-) anions and water mol-ecules into a three-dimensional supra-molecular architecture. π-π stacking between the pyridine rings of adjacent cations is also observed, the centroid-to-centroid distance being 3.7578 (8) Å.