Effects of different deposition models on the calculated dose conversion factors from 222Rn progeny

Regional lung deposition for radon progeny (size range, 1 nm to 1000 nm, monodispersed) has been determined employing Gormley-Kennedy, Ingham, Cohen-Asgharian and Yu-Cohen expressions (which describe diffusion deposition), together with Gurman and Cheng formulae for impaction and sedimentation, respectively. The deposition values have been compared with those obtained by using the algebraic expressions recommended by ICRP66. The behavior of the deposition curves for breathing rates of 0.45, 0.78 and 1.2 m3 h(-1) are similar, with a broad maximum in the range (1-100) nm. In the particle size range (1-100) nm, where the thermodynamic efficiency predominates, there are large differences among the five approaches, with ICRP values lying somewhat in the middle. Dose Conversion Factors nearly follow the regional deposition trends, Cohen-Asgharian and Ingham, close to the highest values, Yu-Cohen the lowest and ICRP, again, somewhat in the middle.     

Study of harmful algal blooms in a eutrophic pond, Bangladesh

The purpose of this research was to analyze the underlying mechanisms and contributing factors related to the seasonal dynamic of harmful algal blooms in a shallow eutrophic pond, Bangladesh during September 2005–July 2006. Two conspicuous events were noted simultaneously throughout the study period: high concentration of phosphate–phosphorus (>3.03; SD 1.29 mg l^???1) and permanent cyanobacterial blooms {>3,981.88 × 10³ cells l^???1 (SD 508.73)}. Cyanobacterial blooms were characterized by three abundance phases, each of which was associated with different ecological processes. High nitrate–nitrogen (>2.35; SD 0.83 mg l^???1), for example, was associated with high cyanobacterial abundance, while low nitrate–nitrogen (0.36; SD 0.2 mg l^???1) was recorded during moderate abundance phase. Extremely low NO₃–N/PO₄–P ratio (>3.55, SD 2.31) was recorded, and all blooming taxa were negatively correlated with this ratio. Cyanobacterial blooms were positively correlated with temperature (r?=?0.345) and pH (0.833; p?=?0.05) and negatively correlated with transparency (r?=???0.956; p?=?0.01). Although Anabaena showed similar relationship with water quality parameters as cyanobacteria, the co-dominant Microcystis exhibited negative relationship with temperature (r?=???0.386) and nitrate–nitrogen (r?=???0.172). This was attributed to excessive growth of Anabaena that suppressed Microcystis’s growth. Planktothrix was the third most dominant taxa, while Euglena was regarded as opportunistic.     

Ecochemical assessment of environmental chemicals Part 2: Standard supplementary screening procedure to evaluate more volatile and less persistent chemicals in plant cell cultures

The described methodology allows the determination of metabolic turnover, biomineralization and volatilization of organic environmental chemicals. The overall accountability of radiolabelled chemicals with standardized soybean and wheat cell cultures determined is nearly quantitative. The total balance of the radiolabelled dichlofluanid, 2,4-dichlorophenoxyacetic acid, monolinuron, lindane, parathion and pentachlorophenol recovered by this method are reported.     

Radon progeny dose conversion coefficients for Chinese males and females

The airway dimensions for Caucasian males have been scaled by multiplying by factors 0.95 and 0.88 to give those for Chinese males and females, respectively. Employing the most recent data on physical and biological parameters, the radiation doses to the basal and secretory cells due to alpha particles from 218Po and 214Po, homogeneously distributed in the mucous layer, have been calculated. The emission of alpha particles has been simulated by a Monte Carlo method. For both basal and secretory cells, the dose conversion coefficients (DCCs) for physical conditions of sleep, rest, light and heavy exercise, have been obtained for Chinese males and females for unattached progeny, and for attached progeny of diameters 0.02, 0.15, 0.25, 0.30 and 0.50 micron. For basal cells, the coefficients lie in the range 0.69-6.82 mGy/(Js/m3) or 8.7-86 mGy/WLM for unattached progeny and in the range 0.045-1.98 mGy/(Js/m3) or 0.57-25 mGy/WLM for attached progeny. The corresponding ranges for Caucasian males are 1.27-8.81 mGy/(Js/m3) or 16-111 mGy/WLM-1 and 0.05-2.30 mGy/(Js/m3) or 0.64-29 mGy/WLM. For secretory cells, the coefficients lie in the range 0.095-16.82 mGy/(Js/m3) (1.2-212 mGy/WLM) for unattached progeny and in the range 0.095-6.67 mGy/(Js/m3) (1.2-84 mGy/WLM) for attached progeny. The corresponding ranges for Caucasian males are 0.34-21.51 mGy/(Js/m3) (4.3-271 mGy/WLM) and 0.1-7.78 mGy/(Js/m3) (1.3-98 mGy/WLM). The overall DCCs calculated for a typical home environment are 0.59 and 0.52 mSv/(Js/m3) (7.4 and 6.5 mSv/WLM) for Chinese males and females, respectively, which are 80 and 70% of the value, 0.73 mSv/(Js/m3) (9.2 mSv/WLM), for Caucasian males.     

Equilibrium sampling used to monitor malodors in a Swine waste lagoon

The concentrations of malodorous compounds in a 0.4-ha anaerobic lagoon that received waste from approximately 2000 sows were monitored during the late summer to late fall of 2006 to gain insight into the factors influencing their concentrations. Selected malodorous compounds were measured by the use of equilibrium samplers consisting of submersible stir plates and stir bar sorbtive sampling with polydimethylsiloxane-coated magnetic stir bars. During the same period, air and water temperatures, suspended solids, total organic carbon and nitrogen content, and wastewater pH were recorded. Concentrations of malodorous compounds were higher at the surface of the lagoon than at the middle or bottom of the lagoon. Skatole concentration, for instance, averaged 54, 24, and 38 microg L(-1) near the surface, in the middle, and at the lowest sampling depths, respectively. While the lagoon was being pumped down during field application of wastewater, concentrations of malodorous compounds fluctuated widely, increased 16-fold as compared with the sampling period before pumping, and continued to increase as fall progressed and temperatures cooled. Suspended solids, volatile suspended solids, and total organic carbon increased near the bottom of the lagoon during this same period. The increases in the concentrations of malodorous compounds in the wastewater during the fall could have been due to a combination of several factors. These factors include reduced degradation by lagoon bacteria, less wind stripping of volatile compounds from the lagoon surface due to lowering of the lagoon surface after crop application, and/or reduced evaporation of malodorous compounds due to falling temperatures.     

Variability of water quality and metal pollution index in the Ganges River,Bangladesh

Environmental Science and Pollution Research - The Ganges River is one of the biggest transboundary streams in the Indian sub-continent. The significant part of this waterway channel drains one of...     

Evaluating mobilization and transport of arsenic in sediments and groundwaters of Aquia aquifer, Maryland, USA

Groundwater and sediment samples were collected along a flow path in the Aquia aquifer (Paleocene), Maryland in order to examine and study the factors influencing "evolution" of arsenic (As) in these groundwaters. The Aquia crops out near Washington, DC, where it is unconfined, and extends approximately 90 km down dip to the south and east towards and beneath the Chesapeake Bay. The studied flow path was chosen owing to (i) the number of accessible wells, (ii) differences in total dissolved As concentrations in groundwaters from some of the sampled wells, which reach values >/=667 nmol kg(-1) or >/=50 ppb, and (iii) the distinct difference in total dissolved As concentrations in Aquia groundwaters between the northern and southern portions of the study area. In groundwater samples, in situ separation of inorganic As species [As(III) and As(V)] were performed by using anion exchange chromatography. Subsequently, As concentrations were determined by inductively coupled plasma mass spectrometry. In situ measurements of Fe concentrations and speciation, dissolved S(-II) concentrations, pH, alkalinity, and oxidation-reduction potential (Eh) were determined to establish the oxidation-reduction conditions and solution chemistry along the flow path. Concentrations of As in 12 analyzed groundwater samples range from approximately 0.75 to 1 072 nmol kg(-1), and As(III) concentrations ranging from 0.24 to 980 nmol kg(-1) appears to be the dominant form of As in solution. 50% of the studied wells yielded groundwaters with concentrations that exceed the US EPA's Maximum Contaminant Level for As in drinking water of 133 nmol kg(-1) or 10 ppb. In order to examine the solid phase speciation of As within the aquifer sediments, we collected a number of Aquia sediment samples from a drill core that was archived at the Maryland Geological Survey. These sediment samples were evaluated using a previously established sequential extractions procedure. Solid phase As concentrations range between 973 and 2,012 nmol kg(-1). Additionally, petrographic, X-Ray diffraction and diffuse reflectance spectroscopy analyses of the Aquia sediments reveal presence of glauconite, and smectite along with goethite and hematite within the samples. Here, we present the possible mechanisms responsible for the elevated As concentrations in the studied groundwaters of the Aquia aquifer.