Reconstruction of 137Cs signal in Cuba using 7Be as tracer of vertical transport processes in the atmosphere

Levels of 137Cs and 7Be in aerosols have been measured in the region of Cienfuegos (Cuba) during the period 1994-1998. 137Cs showed the same seasonal trend as 7Be and the monthly regimes of precipitation seemed to be responsible for the observed pattern. The 137Cs/7Be ratio obtained in Cienfuegos and Miami (FL) in this period was used to calibrate the long-term database of 137Cs concentrations recorded in Miami (250 km from Cienfuegos). The database was then employed to reconstruct the 137Cs monthly concentrations in Cienfuegos since 1957.     

Presence, distribution, and origins of polycyclic aromatic hydrocarbons (PAHs) in sediments from Bahía Blanca estuary, Argentina

This paper is the first comprehensive survey of polycyclic aromatic hydrocarbons (PAHs) in coastal sediments in Bahia Blanca, Argentina, and provides useful information on their levels of concentration, composition, and sources of these pollutants. The total concentrations of PAHs ranged from 15 to 10,260 ng g^???1. The highest contents (mean 3,315 ng g^???1) of total PAHs in marine sediments were found in the inner channels of the estuary, while the lower ones (204 ng g^???1) belong to samples collected far away from contamination sources. The global average recorded in this study (1,500 ng g^???1) indicates that the studied area lies within the referenced category of industrialized coastal zones under chronic pollution. The diagenetic PAH contribution was found to be negligible at all sampled locations; however, the calculation of molecular ratios determined an overimposition of pyrolitic PAHs over the petrogenic input. Further, the use of principal components analysis (PCA) clearly separated ring group compounds and enabled the determination of pyrolitic/combustion PAHs dominancy.     

Sources and behaviour of polybrominated diphenyl ethers (PBDEs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in Spanish sewage sludge

Presence, sources and behaviour of polybrominated diphenyl ethers (PBDEs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were evaluated in Spanish sewage sludge. A total of 120 samples were seasonally collected from October 2005 to September 2006 at 31 urban wastewater treatment plants (WWTPs). Concentrations of PBDEs (ranging between 57.5 and 2606 ng/g dry weight) were two to three orders of magnitude higher than those obtained for PCDDs (0.17-5.03 ng/g d.w.) and PCDFs (0.05-3.07 ng/g d.w.). All the samples presented International Toxicity Equivalents (I-TEQ) levels (ranging between 2.06 and 44.4 ng/kg d.w.) below the limit values proposed by European Union for land application. Congener patterns evaluation revealed that the use of Deca-BDE commercial mixture seems to be the major source of PBDEs in the sludge. Nevertheless, origin of PCDD/Fs should be related to atmospheric deposition, faeces and presence of PCDD/Fs precursors such as pentachlorophenol in the sludge. No correlations (p > 0.05) were found between pollutant concentrations (PBDEs and PCDD/Fs) and wastewater treatment plant (WWTP) characteristics (capacity nor sludge rate). Lower levels of PBDEs and PCDFs were found in WWTPs using biological nitrogen and phosphorous elimination, suggesting that these compounds are susceptible of microbial elimination. According to our knowledge, this is the first work comparing together both PBDEs and PCDD/Fs sludge patterns.     

Study of the uncertainty in NO<Subscript>2</Subscript> chemiluminescence measurements due to the NO–O<Subscript>3</Subscript> reaction in sampling lines

Introduction  

The change in light intensity that takes place when an ambient air sample is drawn into the detection chamber of a chemiluminescence monitor generates changes in the concentrations of several species, such as NO₂, NO and O₃. Although this phenomenon has been known for several decades, there is still no commonly accepted approach on when or how to correct for it in NO₂ and O₃ readings.     

Limitation of the concentration of organic pollutants in sewage sludge for agricultural purposes: A case study in South Spain

In 2000, the EU published the third draft of a future sludge directive entitled “Working document on sludge” where limit values for some organic compounds, including di-(2-ethyhexyl)phthalate (DEHP), sum of nonylphenol (NP), nonyphenol mono-(NP1EO) and diethoxylates (NP2EO), seven polychlorinated biphenyl congeners (PCB), polycyclic aromatic hydrocarbons (PAH) and linear alkylbenzene sulphonates (LAS), are fixed. In the present work, the monitoring of these organic compounds in sludge samples from four wastewater treatment plants (WWTPs) is reported. All WWTPs use anaerobic biological stabilization of sludge. The highest concentration levels were found for LAS, NPE and DEHP, in this order, with, in general, anaerobically-digested dehydrated sludge and compost samples being the most contaminated samples. DEHP, NPE, LAS and PAH were found at concentration levels above the limit values fixed in the third draft of the future EU sludge directive in the 44%, 88%, 13% and 6% of the analyzed anaerobically-digested dehydrated sludge and compost samples.     

Laser induced fluorescence instrument for NO2 measurements: Observations at a central Italy background site

A laser induced fluorescence (LIF) instrument has been developed to measure tropospheric NO₂ with low detection limit. The instrument design, development and first measurements are reported. There are also details of the temporal gate system built for the fluorescence acquisition. The instrument is able to make fast measurements (up to 4 Hz) and shows a limit of detection of 10 pptv/60 s. Continuous observations (2 weeks in summer 2007) in a small town in central Italy were used to test the performance of the instrument and to study the photochemistry of ozone in a background site. LIF and a commercial chemiluminescence (CL) instrument simultaneous observations of NO₂ show a good linearity (LIF = 1.02 CL + 0.6 (ppb), R² = 0.98) but there is a bias of the commercial instrument of about 0.60 ppbv on average. The overestimation of the CL system is probably due to conversion of NO_y species into NO by the molybdenum converter used in the CL instrument to detect NO₂. Analysis of 1 s data is used to test the instrument response and the coupling between nitrogen oxides and ozone.     

High bromine oxide concentrations in the semi-polluted boundary layer

Bromine chemistry in the marine boundary layer is recognized to play an important role through catalytic ozone destruction, changes to the atmospheric oxidising capacity (by changing the OH/HO₂ and NO/NO₂ ratio) and oxidation of compounds such as dimethyl sulphide (DMS). However, the chemistry of bromine in polluted environments is not well understood and its effects are thought to be inhibited by reactions involving NO_x (NO₂ & NO). This paper describes long-path Differential Optical Absorption Spectroscopy (DOAS) observations of bromine oxide (BrO) at a semi-polluted coastal site in Roscoff, France. Significant concentrations of BrO (up to 7.5 ± 1.0 pptv) were measured during daytime, indicating the presence of unknown sources or efficient recycling of reactive bromine from bromine nitrate (BrONO₂), which should be the major reservoir for bromine in a high NO_x environment. These measurements indicate that bromine chemistry can play an important role in polluted environments.     

Influence of particle location on the number of charges per charged nanoparticle at the outlet of a needle charger

This study has investigated numerically the influence of particle location on the number of charges per charged particle in the 10-40 nm size range at the outlet of a needle charger by simulating flow field, electric field, particle charging, and particle trajectory at various conditions. The results show that the total (i.e., diffusion + field charging) number of charges per particle increase with decreasing ratio values of radial location at the outlet of the charger due to the particle position close to the needle tip. It has also been shown that in the outlet region of the charger there is a critical radial location at which the number of charges per particle is a maximum; this critical radial location represents the point at which the charged particle trajectory becomes closest to the needle electrode. The maximum value of number of charges increases with increasing Reynolds number and slightly increases with decreasing applied voltage for particle diameter larger than 20 nm. The maximum number of charges per charged nanoparticle increases with increasing particle diameter. In addition, the minimum ratio value of radial particle location decreases with increasing Reynolds number for various particle diameters.     

Population characteristics of young African women influencing prenatal exposure to DDT (Manhiça, Mozambique)

The concentrations of dichlorodiphenyltrichloroethane (DDT) compounds in cord blood of 214 children born between 2003 and 2006 in Manhiça (Mozambique) have been determined. In this time interval, corresponding to the period before DDT reintroduction for indoor residual spraying, the observed values averaged 0.8 and 0.4 ng/ml for 4,4′-dichlorodiphenyldichloroethylene (4,4′-DDE) and 4,4′-DDT, respectively, and were similar to those found in western countries. However, the 4,4′-DDT/4,4′-DDE ratio was high indicating that the inputs of these compounds arriving to children in utero originated from recent uses of the insecticide. The strongest factor affecting DDT concentration was parity. A well-defined decreasing concentration trend was observed for the cord blood concentrations in the period of study. The trend was also observed for multiparae and primiparae mothers independently. Children from multiparae women showed much lower concentrations than primiparae women. Children from mothers with secondary school level exhibited lower concentrations of these pesticides than mothers with lower degree of education.