Complete degradation of di-n-octyl phthalate by Gordonia sp. strain Dop5

The present study describes the assimilation of di-n-octyl phthalate by an aerobic bacterium, isolated from municipal waste-contaminated soil sample utilizing di-n-octyl phthalate as the sole source of carbon and energy. The isolate was identified as Gordonia sp. based on the morphological, nutritional and biochemical characteristics as well as 16S rRNA gene sequence analysis. A combination of chromatographic and spectrometric analyses revealed a complete di-n-octyl assimilation pathway. In the degradation process, mono-n-octyl phthalate, phthalic acid, protocatechuic acid and 1-octanol were identified as the degradation products of di-n-octyl phthalate. Furthermore, phthalic acid was metabolized via protocatechuic acid involving protocatechuate 3,4-dioxygenase while 1-octanol was metabolized by NAD⁺-dependent dehydrogenases to 1-octanoic acid, which was subsequently degraded via β-oxidation, ultimately, leading to tricarboxylic acid cycle intermediates. Apart from phthalic acid and 1-octanol metabolizing pathway enzymes, two esterases, di-n-octyl phthalate hydrolase and mono-n-octyl phthalate hydrolase involved in di-n-octyl phthalate degradation were found to be inducible in nature. This is the first report on the metabolic pathway involved in the complete degradation of di-n-octyl phthalate by a single bacterial isolate, which is also capable of efficiently degrading other phthalate esters of environmental concern having either shorter or longer alkyl chains.     

Underwater treatment of lead-contaminated sediment

The sediment associated with the reconstruction of a bridge pier was classifiable as hazardous by the Toxicity Characteristic Leaching Procedure (TCLP), due to elevated concentrations of lead. However, RCRA regulations do not classify the sediment as hazardous unless it is moved. RMT designed an in-situ, underwater treatment process to render the sediment nonhazardous, using phosphate-based chemistry before dredging. Subsequent sediment management was conducted without the additional regulatory requirements and costs associated with managing hazardous waste.     

COMPARING SOME METHODS OF ESTIMATING MEAN AREAL RAINFALL1

ABSTRACT: A comparison of 13 different methods of estimating mean areal rainfall was made on two areas in New Mexico, U.S.A., and one area in Great Britain. Daily, monthly and yearly rainfall data were utilized. All methods, in general, yielded comparable estimates, especially for yearly values. This suggested that a simpler method would be preferable for estimating mean areal rainfall in these areas.     

Bioremediation potential of Brevibacillus parabrevis AMB-CD-2 in spinach under lead toxicity

The present study was conducted to evaluate the impact of lead toxicity on the growth parameters of spinach and the performance of lead-resistant bacterial isolates under lead stress conditions. Out of four bacterial isolates selected for this study, only two isolates AMB-CD-2 and AMB-CD-4 were selected based on their lead tolerance ability. A polybag experiment was conducted with six treatments and four replications in spinach. The treatments included T₁ (RDF + control), T₂ (lead acetate), T₃ (AMB-CD-2 + lead), T₄ (AMB-CD-4 + lead), T₅ (AMB-CD-2), and T₆ (AMB-CD-4). Results showed that lead contamination significantly decreased plant growth parameters, particularly in the treatment T₂ (lead acetate) when compared with other treatments. Similarly, reduced uptake of nitrogen, phosphorus, and potassium (NPK) was recorded in T₂. Inoculation with lead-resistant bacteria, AMB-CD-2, significantly improved plant growth parameters (plant height, root fresh weight, shoot fresh weight, root dry weight, shoot dry weight, and root length). The uptake of NPK was higher in T₅ (AMB-CD-2) in the absence of lead by approximately 0.81%, 0.37%, and 0.42% than in the control, respectively. Through atomic absorption spectrophotometer analysis, the lead concentration in treatment T₂ (control) was about 3.20 mg/g while in treatment T₃ (AMB-CD-2 + lead) it was about 1.32 ppm. The 16S rRNA gene sequencing revealed that AMB-CD-2 resembles Brevibacillus parabrevis. The results demonstrate that the lead-resistant bacteria B. parabrevis AMB-CD-2 showed a significant lead reduction of approximately 58.75% compared to the control.     

Polychlorinated biphenyl (118) activates osteoclasts and induces bone resorption in goldfish

To analyze the effect of polychlorinated biphenyl (PCB) 118 on fish bone metabolism, we examined osteoclastic and osteoblastic activities, as well as plasma calcium levels, in the scales of PCB (118)-injected goldfish. In addition, effect of PCB (118) on osteoclasts and osteoblasts was investigated in vitro. Immature goldfish, in which the endogenous effects of sex steroids are negligible, were used. PCB (118) was solubilized in dimethyl sulfoxide at a concentration of 10 ppm. At 1 and 2 days after PCB (118) injection (100 ng/g body weight), both osteoclastic and osteoblastic activities, and plasma calcium levels were measured. In an in vitro study, then, both osteoclastic and osteoblastic activities as well as each marker mRNA expression were examined. At 2 days, scale osteoclastic activity in PCB (118)-injected goldfish increased significantly, while osteoblastic activity did not change significantly. Corresponding to osteoclastic activity, plasma calcium levels increased significantly at 2 days after PCB (118) administration. Osteoclastic activation also occurred in the marker enzyme activities and mRNA expressions in vitro. Thus, we conclude that PCB (118) disrupts bone metabolism in goldfish both in vivo and in vitro experiments.     

Recycling of nickel smelter slag for arsenic remediation—an experimental study

In this study, recycled Ni smelter slag has been used as a reactive medium for arsenic (As) removal from aqueous solutions. The results of the study showed that 10.16–11.43-cm long columns containing 451–550 g of slag operated for at least 65 days were able to remove 99–100 % As species from continuously flowing contaminated water at an initial As concentration of 10 mg/L. The removal capacities were found to be 1.039 to 1.054 mg As per g of slag. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy data also showed that electrostatic attraction and oxidation–reduction reactions between As species and mixed iron oxides present in the slag were the main mechanisms for the removal of arsenic from aqueous solutions. Theoretical multiplet analysis of XPS data revealed that the amount of goethite in the slag increased from 22 to 60 % during arsenic removal by adsorption and the percentage of magnetite decreased from 50 to 40 %. These changes indicate that redox-mediated reactions occurred as part of the As(V) removal process. Raman spectroscopy studies confirmed that, in addition to surface reactions, internal interactions between the slag and arsenic also occurred. The findings of the study suggest that recycled Ni smelter slag could be an effective low-cost reactive medium for a subsurface remediation system, such as a permeable reactive barrier. Recycling of waste material (slag) for the removal of another waste (arsenic) can significantly reduce the environmental footprint of metallurgical operations and hence contribute to sustainable development. Such recycling also decreases slag disposal costs and eliminates the need to purchase commercial reactive material or obtain expensive natural material for remediation purposes.     

Concentrations of some heavy metals in commercially important finfish and shellfish of the River Ganga

Heavy metals are dangerous to aquatic organisms and it can be bioaccumulated in the food chain leading to diseases in human. Cumulative effects of metals or chronic poisoning may occur as a result of long-term exposure even to low concentrations. The accumulation of heavy metals varies depending upon the species, environmental conditions, and inhibitory processes. Concentrations of zinc, copper, lead, and cadmium were determined in finfish and shellfish species in the Gangetic delta using a PerkinElmer Sciex ELAN 5000 ICP mass spectrometer and expressed as milligrams per kilogram of dry weight. In finfish and shellfish species the concentrations of Zn, Cu, Pb, and Cd were comparatively higher at stations 1 and 2 than the permissible level of WHO. The concentration of metals exhibited significant spatial variation and followed the order station 1 > station 2 > station 3 > station 4, which may be related to different degree of contamination in different location. The metal accumulation exhibited species specificity.     

Load maximization of a liquid-solid circulating fluidized bed bioreactor for nitrogen removal from synthetic municipal wastewater

A novel liquid-solid circulating fluidized bed bioreactor (LSCFB) configured with anoxic and aerobic columns and lava rock as the biofilm carrier was used to treat synthetic municipal wastewater. Four different empty bed contact times (EBCTs) of 0.82, 0.65, 0.55, and 0.44 h were examined to optimize nutrient removal capability of the system. The LSCFB demonstrated tertiary effluent quality organic and nitrogen removal efficiencies. Effluent characteristics of the LSCFB were soluble biological oxygen demand (SBOD)10 mg l(-1) and total nitrogen (TN)<10 mg l(-1) at organic loading rate (OLR) of 5.3 kg m(-3)d(-1) and nitrogen loading rate of 0.54 kg Nm(-3)d(-1). Remarkably low yields of 0.14, 0.17, 0.19, and 0.21 g VSS g(-1)COD were observed at OLR of 2.6, 3.2, 4.1 and 5.3 kg COD m(-3)d(-1), where increment of biomass growth and detachment rate were also experienced with increasing OLR. However the system demonstrated only 30% phosphorus removal, and mass balances along the anoxic and aerobic columns showed biological phosphorus removal in the system. Organic mass balance showed that approximately 40% of the influent COD was utilized in the anoxic column and the remaining COD was oxidized in the aerobic column. The system is very efficient in nitrification-denitrification, with more than 90% nitrification of ammonium and overall nitrogen removal in the LSCFB was 70+/-11% even at an EBCT of 0.44 h.     

Application of Sample Selection Model in Estimating Response Functions for Nitrate Percolation

The Seymour aquifer region of Texas has been identified as containing elevated levels of nitrate in ground water. Various state and federal agencies are currently studying policy options for the region by gathering more site-specific information. However, because of lack of sufficient information, cause and effect relationships between water quality and agricultural practices have not been well established for the region. Some recently available biophysical simulation models have impressive capabilities in generating large amounts of data on environmental pollution resulting from agricultural production practices. In this study, the data generated by a biophysical simulation model were used to estimate the nitrate percolation response functions for the Seymour aquifer region. Interestingly, nitrate percolation values obtained from simulation models often comprise acensoredsample because the non-zero percolation values are only observed under certain climatic events and input levels. It has been shown in the econometric literature that the use of Ordinary Least Squares (OLS) on censored sample data produces biased and inconsistent parameter estimates. Thus, a sample selection model was used in this study to estimate the response functions for nitrate percolation. The study provides some insight into the relationship between nitrate percolation and agricultural production practices. In particular, the study demonstrates the potential of selected design standards in minimizing agricultural nonpoint-source (NPS) pollution for the study area.