Self-inhibition can limit biologically enhanced TCE dissolution from a TCE DNAPL

Biodegradation of trichloroethene (TCE) near a Dense Non Aqueous Phase Liquid (DNAPL) can enhance the dissolution rate of the DNAPL by increasing the concentration gradient at the DNAPL-water interface. Two-dimensional flow-through sand boxes containing a TCE DNAPL and inoculated with a TCE dechlorinating consortium were set up to measure this bio-enhanced dissolution under anaerobic conditions. The total mass of TCE and daughter products in the effluent of the biotic boxes was 3-6 fold larger than in the effluent of the abiotic box. However, the mass of daughter products only accounted for 19-55% of the total mass of chlorinated compounds in the effluent, suggesting that bio-enhanced dissolution factors were maximally 1.3-2.2. The enhanced dissolution most likely primarily resulted from variable DNAPL distribution rather than biodegradation. Specific dechlorination rates previously determined in a stirred liquid medium were used in a reactive transport model to identify the rate limiting factors. The model adequately simulated the overall TCE degradation when predicted resident microbial numbers approached observed values and indicated an enhancement factor for TCE dissolution of 1.01. The model shows that dechlorination of TCE in the 2D box was limited due to the short residence time and the self-inhibition of the TCE degradation. A parameter sensitivity analysis predicts that the bio-enhanced dissolution factor for this TCE source zone can only exceed a value of 2 if the TCE self-inhibition is drastically reduced (when a TCE tolerant dehalogenating community is present) or if the DNAPL is located in a low-permeable layer with a small Darcy velocity.     

Biotransformation of atrazine and metolachlor within soil profile and changes in microbial communities

Biotransformation studies of atrazine, metolachlor and evolution of their metabolites were carried out in soils and subsoils of Northern Greece. Trace atrazine, its metabolites and metolachlor residues were detected in field soil samples 1 year after their application. The biotransformation rates of atrazine were higher in soils and subsoils of field previously exposed to atrazine (maize field sites) than in respective layers of the field margin. The DT₅₀ values of atrazine ranged from 5 to 18 d in the surface layers of the adapted soils. DT₅₀ values of atrazine increased as the soil depth increased reaching the value of 43 d in the 80-110 cm depth layer of adapted soils. Metolachlor degraded at slower rates than atrazine in surface soils, subsoils of field and field margins with the respective DT₅₀ values ranging from 56 to 72 d in surface soils and from 165 to 186 d in subsoils. Hydroxyatrazine was the most frequently detected metabolite of atrazine. The maximum concentrations of metolachlor-OXA and metolachlor-ESA were detected in the soil layers of 20-40 cm depth after 90 d of incubation. Principal Component Analysis (PCA) of soil Phospholipid Fatty Acids (PLFAs), fungal/bacterial and Gram-negative/Gram-positive ratios of the PLFA profiles revealed that the higher biotransformation rates of atrazine were simultaneously observed with the abundance of Gram-negative bacteria while the respective rates of metolachlor were observed in soil samples with abundance of fungi.     

Phytoremediation of textile effluent and mixture of structurally different dyes by Glandularia pulchella (Sweet) Tronc

Plants of Glandularia pulchella (Sweet) Tronc. performed decolorization of structurally different dyes to varying extent because of induction of different set of enzymes in response to specific dyes. Differential pattern of enzyme induction with respect to time was obtained for lignin peroxidase, veratryl alcohol oxidase, tyrosinase and dichlorophenolindophenol reductase during the decolorization of dye mixture, whose combined action resulted in greater and faster decolorization of dyes. HPLC, FTIR and High Performance Thin Layer Chromatography (HPTLC) analysis confirmed degradation of dyes from textile effluent and mixture. HPTLC demonstrated progressive decolorization of dye mixture along with preferential degradation of the dyes. G. pulchella showed reduction in American Dye Manufacturer's Institute from 405 to 21 and 418 to 22, in case of textile effluent and mixture of dyes respectively. The non-toxic nature of the metabolites of degraded textile dye effluent and mixture of dyes was revealed by phytotoxicity studies.     

Agricultural pesticide residues of farm runoff in the Okanagan Valley, British Columbia, Canada

The objectives of this study were to determine environmental occurrence and concentrations of selected currently-used-pesticides and some transformation products in agricultural farms in the Okanagan Valley (OKV), and to conduct a simple risk assessment of environmental pesticides levels detected in OKV on non-target aquatic organisms. The OKV is the tree fruit country of the Province of British Columbia where considerable amount of pesticides are applied annually. Water, sediment and soil samples were collected at eleven sites in early June and late September following rainfall events and/or extended periods of irrigation from drainage ditches and/or from small streams. Undisturbed reference sites were also sampled. Study results showed that forty of the eighty chemicals analyzed, including organochlorine, nitrogen-containing and organophosphate pesticides commonly used for OKV crops, were detected in runoff and small stream water samples. Among which, endosulfan-sulfate was the most frequently detected chemical. Also, azinophos-methyl (0.699-25.5 ng/L), diazinon (0.088-214 ng/L) exceeded, and α-, β- endosulfan, endosulfan sulphate approached the guidelines for the protection of aquatic life.     

Bacterial assisted phytoremediation for enhanced degradation of highly sulfonated diazo reactive dye

Purpose

Phytoremediation is the exploitation of plants and their rhizospheric microorganisms for pollutants treatment like textile dyes, which are toxic, carcinogenic and mutagenic from the effluent. The purpose of this work was to explore a naturally found plant and bacterial synergism to achieve an enhanced degradation of Remazol Black B dye (RBB).

Methods

In vitro cultures of Zinnia angustifolia were obtained by seed culture method. Enzymatic analysis of the plant roots and Exiguobacterium aestuarii strain ZaK cells was performed before and after decolorization of RBB. Metabolites of RBB formed after its degradation were analyzed using UV?CVis spectroscopy, high-performance liquid chromatography (HPLC), Fourier transform infrared (FTIR) and gas chromatography?Cmass spectrometry (GC-MS). Phytotoxicity studies were performed.

Results

The consortium ZE was found to be more efficient than individual plant and bacteria. Z. angustifolia roots showed significant induction in the activities of lignin peroxidase, laccase, DCIP reductase and tyrosinase during dye decolorization. E. aestuarii showed significant induction in the activities of veratryl alcohol oxidase, azo reductase and DCIP reductase. Analysis of metabolites revealed differential metabolism of RBB by plant, bacteria and consortium ZE. E. aestuarii and Z. angustifolia led to the formation of 3,6-diamino-4-hydroxynaphthalene-2-sulfonic acid, (ethylsulfonyl)benzene, and 3,4,6-trihydroxynaphthalene-2-sulfonic acid and propane-1-sulfonic acid, respectively, whereas consortium ZE produced 4-hydroxynaphthalene-2-sulfonic acid, naphthalene-2-sulfonic acid and 4-(methylsulfonyl)phenol. The phytotoxicity study revealed the nontoxic nature of the metabolites formed after dye degradation.

Conclusion

Consortium ZE was found to be more efficient and faster in the degradation of RBB when compared to degradation by Z. angustifoila and E. aestuarii individually.     

Fallout traces of the Fukushima NPP accident in southern West Siberia (Novosibirsk,Russia)

Background  

The fallout of artificially produced radioactive isotopes has been recorded at a site in southern West Siberia (54°50′43.6″ N, 083°06′22.4″ E, Novosibirsk, Russia).     

Modeling and optimization of trihalomethanes formation potential of surface water (a drinking water source) using Box–Behnken design

Purpose  

The present research aims to investigate the individual and interactive effects of chlorine dose/dissolved organic carbon ratio, pH, temperature, bromide concentration, and reaction time on trihalomethanes (THMs) formation in surface water (a drinking water source) during disinfection by chlorination in a prototype laboratory-scale simulation and to develop a model for the prediction and optimization of THMs levels in chlorinated water for their effective control.     

Acute toxicity tests with Daphnia magna, Americamysis bahia, Chironomus riparius and Gammarus pulex and implications of new EU requirements for the aquatic effect assessment of insecticides

Threshold concentrations for treatment related effects of 31 insecticides, as derived from aquatic micro-/mesocosm tests, were used to calibrate the predictive value of the European Tier-1 acute effect assessment on basis of laboratory toxicity tests with Daphnia magna, Chironomus spp., Americamysis bahia and Gammarus pulex. The acute Tier-1 effect assessment on basis of Daphnia (EC(50)/100) overall was protective for organophosphates, carbamates and most pyrethroids but not for neonicotinoids and the majority of insect growth regulators (IGRs) in the database. By including the 28-day water-spiked Chironomus riparius test, the effect assessment improves but selecting the lowest value on basis of the 48-h Daphnia test (EC50/100) and the 28-day Chironomus test (NOEC/10) is not fully protective for 4 out of 23 insecticide cases. An assessment on basis of G. pulex (EC(50)/100) is sufficiently protective for 15 out of 19 insecticide cases. The Tier-1 procedure on basis of acute toxicity data (EC(50)/100) for the combination of Daphnia and A. bahia and/or Chironomus (new EU dossier requirements currently under discussion) overall is protective to pulsed insecticide exposures in micro-/mesocosms. For IGRs that affect moulting, the effect assessment on basis of the 48-h Chironomus test (EC(50)/100) may not always be protective enough to replace that of the water-spiked 28-day C. riparius test (NOEC/10) because of latency of effects.     

Particulate matter emission rates from beef cattle feedlots in Kansas-reverse dispersion modeling

Open beef cattle feedlots emit various air pollutants, including particulate matter (PM) with equivalent aerodynamic diameter of 10 microm or less (PM10); however limited research has quantified PM10 emission rates from feedlots. This research was conducted to determine emission rates of PM10 from large cattle feedlots in Kansas. Concentrations of PM10 at the downwind and upwind edges of two large cattle feedlots (KS1 and KS2) in Kansas were measured with tapered element oscillating microbalance (TEOM) PM10 monitors from January 2007 to December 2008. Weather conditions at the feedlots were also monitored. From measured PM10 concentrations and weather conditions, PM10 emission rates were determined using reverse modeling with the American Meteorological Society/U.S. Environmental Protection Agency Regulatory Model (AERMOD). The two feedlots differed significantly in median PM10 emission flux (1.60 g/m2-day for KS1 vs. 1.10 g/m2-day for KS2) but not in PM10 emission factor (27 kg/1000 head-day for KS1 and 30 kg/1000 head-day KS2). These emission factors were smaller than published U.S. Environmental Protection Agency (EPA) emission factor for cattle feedlots.