Biodegradation and removal of 3,4-dichloroaniline by Chlorella pyrenoidosa based on liquid chromatography-electrospray ionization-mass spectrometry

Compound-Specific Carbon, Nitrogen, and Hydrogen Isotope Analysis to Characterize Aerobic Biodegradation of 2,3-Dichloroaniline by a Mixed Enrichment Culture

Compound-specific isotope analysis (CSIA) is an established tool to track the in situ transformation of organic chemicals at contaminated sites. In this work, we evaluated the potential of multi-element CSIA to assess biodegradation of 2,3-dichloroaniline (2,3-DCA), which is a major industrial feedstock. Using controlled laboratory experiments, we determined, for the first time, negligible carbon (<0.5‰) and hydrogen (<10‰) isotope fractionation and a significant inverse nitrogen isotope fractionation (>10‰) during aerobic 2,3-DCA biodegradation by a mixed enrichment culture. The tentative identification of a glutamate conjugate of 2,3-DCA as a reaction intermediate indicates that the initial multistep enzymatic reaction may be rate-limiting. The formation of the glutamate adduct would increase the bond energy at the N atom, thus likely explaining the observed inverse N isotope fractionation. The corresponding nitrogen enrichment factor was +6.8 ± 0.6‰. This value was applied to investigate the in situ 2,3-DCA biodegradation at a contaminated site where the carbon and nitrogen isotope signatures from field samples suggested similar aerobic processes by native microorganisms. Under the assumption of the applicability of the Rayleigh model in a pilot wetland treating contaminated groundwater, the extent of biodegradation was estimated to be up to 80-90%. This study proposes multi-element CSIA as a novel application to study 2,3-DCA fate in groundwater and surface water and provides insights into biodegradation pathways.

Booster Biocides Levels in the Major Blood Cockle (Tegillarca granosa L., 1758) Cultivation Areas along the Coastal Area of Peninsular Malaysia

Booster biocides have been rapidly growing in use, mainly in the shipping industry and in agricultural activities. The use of booster biocides is known to cause adverse effects on marine ecosystems, such as by inhibiting the photosynthesis process in marine plants, and they have the potential to accumulate in marine organisms. In the present study, booster biocides of Irgarol 1051, diuron, 3,4-dichloroaniline (3,4-DCA) and chlorothalonil were measured in the major blood cockle (Tegillarca granosa) cultivation areas along the west coast of Peninsular Malaysia. The highest Irgarol 1051 mean was found in the blood cockle with a value of 98.92 ± 13.65 µg/kg in Kapar, Selangor, while the means of diuron and its metabolites and 3,4-DCA showed the highest values of 40.31 ± 7.61 and 41.42 ± 21.58 µg/kg in Kapar, Selangor and Sungai Ayam, Johor, respectively. Sungai Ayam, Johor also exhibited the highest amount of chlorothalonil of 29.76 ± 8.80 µg/kg. By referring to sediment quality guidelines, about 72% and more than 90% of sediment samples exceeded the environmental risk limits (ERLs) and maximum permissible concentration (MPC) for Irgarol 1051 and diuron, respectively. However, referring to the risk characterization ratio (RCR), none of the blood cockle samples exceeded 1, which means that there is no potential for adverse effects to occur. Thus, the contaminants in the marine ecosystem caused by booster biocides are highlighted as a serious issue, mainly in sediment.

Removal and metabolism of triclosan by three different microalgal species in aquatic environment

Triclosan, an antimicrobial additive widely used in personal care products, has caused the contamination of various aquatic environment. Biodegradation was proved to play a vital role in the treatment of triclosan in wastewater. However, there is limited information about the metabolic pathway. In this study, three common freshwater microalgae including Chlorella pyrenoidosa (C. pyrenoidosa), Desmodesmus sp., and Scenedesmus obliquus (S. obliquus) were applied to remove and biodegrade triclosan in aqueous culture medium. High removal rate up to 99.7% was observed during the treatment of 400μgL^-1 triclosan by the three microalgae for 1day. The removal of triclosan attributed to cellular uptake by C. pyrenoidosa, and biotransformation by Desmodesmus sp. and S. obliquus. Simultaneously, triclosan metabolites resulted from hydroxylation, reductive dechlorination, or ether bond cleavage and their conjugates produced through glucosylation and/or methylation were detected in the biodegradation samples. Metabolic pathway of triclosan by algae were firstly proposed in this work, shedding light on the environmental fate of triclosan.

3,4-Dichloroaniline revisited: A study on the fate of the priority pollutant in a sediment-water system derived from a rice growing region in Italy

As ultimate sink for xenobiotics released into the environment, sediments play an important role concerning the evaluation of the fate of foreign compounds. 3,4-Dichloroaniline (3,4-DCA) is a degradation product of herbicide propanil and some urea herbicides. Propanil was extensively used worldwide in rice cultivation. The aim of the study was to examine the fate of ¹⁴C-labeled 3,4-DCA in a sediment-water system; the sediment was derived from a rice field in Northern Italy. After application of ¹⁴C-3,4-DCA, a time-course study was performed using incubation periods from 4h to 56days. Fractions obtained from assays were water phase, sediment phase including methanol and Soxhlet extract as well as non-extractable residues (NER), and mineralized portion (¹⁴CO₂). Soluble fractions were examined by TLC, HPLC and GC-MS. NER found in sediment phases were further fractionated in non-humics, humic acids, fulvic acids and humin. Stability of systems was checked by microbial activity, dissolved oxygen and pH. After 56days of incubation, 23.1% of applied ¹⁴C was mineralized, only 1.30% remained in the water phase, whereas 60.8% was found in the sediment phase, 53.3% of which were NER. Minor metabolites identified were 3,4-dichloroacetanilide (3,4-DCAA) and 3,3',4,4'-tetrachloroazobenzene (TCAB; 2.63% after 56days). According to pH, dissolved oxygen and microbial activity, systems appeared to be stable and not influenced by applied 3,4-DCA. Most striking result was the high mineralization rate as compared to previously published data. This finding suggested an adaptation of the microbial community in the sediment possibly due to decade-long treatment of rice fields with propanil.

Degradation of aqueous 3,4-dichloroaniline by a novel dielectric barrier discharge plasma reactor

Degradation of aqueous 3,4-dichloroaniline (3,4-DCA) was conducted in a novel dielectric barrier discharge (DBD) plasma reactor. The factors affecting the degradation efficiency of 3,4-DCA and the degradation mechanism of 3,4-DCA were investigated. The experimental results indicated that the degradation efficiency of 3,4-DCA increased with increasing input power intensity, and the degradation of 3,4-DCA by the novel DBD plasma reactor fitted pseudo-first-order kinetics. Higher degradation efficiency of 3,4-DCA was observed in acidic conditions. The degradation efficiency of 3,4-DCA, the removal rate of total organic carbon (TOC), and the detected Cl(-) increased dramatically with adding Fe(2+) or Fe(3+). Degradation of 3,4-DCA could be accelerated or inhibited in the presence of H2O2 depending on the dosage. Several degradation intermediates of 3,4-DCA such as 1,2-dichlorobenzene, 2-chloro-1,4-benzoquinone, 3,4-dichlorophenyl isocyanate, 2-chlorohydroquinone, 3,4-dichloronitrobenzene, and 3,4-dichlorophenol were identified by gas chromatography mass spectrometry (GC-MS) analysis. Based on the identification of aromatic intermediates, acetic acid, formic acid, oxalic acid, and Cl(-) released, a possible mineralization pathway of 3,4-DCA was proposed.

Removal and reductive dechlorination of triclosan by Chlorella pyrenoidosa

Triclosan that is widely used as antimicrobial agent has been detected as contaminant in various aquatic environments. In this work, removal and biodegradation of triclosan in water by using a ubiquitous green alga, Chlorella pyrenoidosa was investigated. When C. pyrenoidosa was exposed to a series concentration of triclosan from 100 to 800ngmL(-1), more than 50% of triclosan was eliminated by algal uptake from the culture medium during the first 1h exposure and reached equilibrium after the 6h treatment. In the biodegradation experiments, a removal percentage of 77.2% was obtained after C. pyrenoidosa was cultivated with 800ngmL(-1) triclosan for 96h. A major metabolite from the reductive dechlorination of triclosan was identified by using liquid chromatography coupled with electrospray ionization-mass spectrometry. The ultrastructural morphology of algal cells grown in the presence of triclosan was observed by using transmission electron microscopy and the growth of algal cells was detected. It was found that the trilcosan treatment resulted in the disruption of the chloroplast and the release of organic material into aquatic environment, which indicated that triclosan may affect membrane metabolism.