Refinar búsqueda
Resultados 571-580 de 1,908
Water concentrations of PAH, PCB and OCP by using semipermeable membrane devices and sediments
2013
Karacık, B. | Okay, O.S. | Henkelmann, B. | Pfister, G. | Schramm, K.-W.
Water concentrations of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were estimated from semipermeable membrane devices (SPMDs) and from sediment pollutant concentrations. SPMDs were deployed in the Istanbul Strait and Marmara Sea and retrieved after 7 and 21days. Performance reference compounds (PRCs) were used to determine the site-specific sampling rates of the compounds. Water concentrations (Cw) of the analyzed compounds estimated by using two different calculation methods for SPMDs were found similar. Cw of total PAHs estimated from SPMDs (Cw-spmd) were found between 13 and 79ngL−1 and between 7.0 and 68ngL−1 for 7 and 21days of deployments respectively. Water concentrations of PCBs using sediment data was found as between 0.001 and 11.0ngL−1. The highest value of Cw-spmd for two deployments were 2.8ngL−1 for OCPs. Cw estimated from sediment concentrations were generally higher than those estimated from SPMDs.
Mostrar más [+] Menos [-]Acid-volatile sulfide and simultaneously extracted metals in surface sediments of the southwestern coastal Laizhou Bay, Bohai Sea: Concentrations, spatial distributions and the indication of heavy metal pollution status
2013
Zhuang, Wen | Gao, Xuelu
Surface sediments were collected from the coastal waters of southwestern Laizhou Bay and the rivers it connects with during summer and autumn 2012. The acid-volatile sulfide (AVS) and simultaneously extracted metals (SEM) were measured to assess the sediment quality. The results showed that not all sediments with [SEM]–[AVS]>0 were capable of causing toxicity because the organic carbon is also an important metal-binding phase in sediments. Suppose the sediments had not been disturbed and the criteria of US Environmental Protection Agency had been followed, heavy metals in this area had no adverse biological effects in both seasons except for few riverine samples. The major ingredient of SEM was Zn, whereas the contribution of Cd – the most toxic metal studied – to SEM was <1%. The distributions of AVS and SEM in riverine sediments were more easily affected by anthropogenic activity compared with those in marine sediments.
Mostrar más [+] Menos [-]Combined SEM/AVS and attenuation of concentration models for the assessment of bioavailability and mobility of metals in sediments of Sepetiba Bay (SE Brazil)
2013
Ribeiro, Andreza Portella | Figueiredo, Ana Maria Graciano | Santos, José Osman dos | Dantas, Elizabeth | Cotrim, Marycel Elena Barboza | Cesar Lopes Figueira, Rubens | V. Silva Filho, Emmanoel | Cesar Wasserman, Julio
This study proposes a new methodology to study contamination, bioavailability and mobility of metals (Cd, Cu, Ni, Pb, and Zn) using chemical and geostatistics approaches in marine sediments of Sepetiba Bay (SE Brazil). The chemical model of SEM (simultaneously extracted metals)/AVS (acid volatile sulfides) ratio uses a technique of cold acid extraction of metals to evaluate their bioavailability, and the geostatistical model of attenuation of concentrations estimates the mobility of metals. By coupling the two it was observed that Sepetiba Port, the urban area of Sepetiba and the riverine discharges may constitute potential sources of metals to Sepetiba Bay. The metals are concentrated in the NE area of the bay, where they tend to have their lowest mobility, as shown by the attenuation model, and are not bioavailable, as they tend to associate with sulfide and organic matter originated in the mangrove forests of nearby Guaratiba area.
Mostrar más [+] Menos [-]Microscopic observation of symbiotic and aposymbiotic juvenile corals in nutrient-enriched seawater
2013
Tanaka, Yasuaki | Iguchi, Akira | Inoue, Mayuri | Mori, Chiharu | Sakai, Keinan | Suzuki, Atsushi | Kawahata, Hodaka | Nakamura, Takashi
Symbiotic and aposymbiotic juvenile corals, which were grown in the laboratory from the gametes of the scleractinian coral Acropora digitifera and had settled down onto plastic culture plates, were observed with a microscope under different nutrient conditions. The symbiotic corals successfully removed the surrounding benthic microalgae (BMA), whereas the aposymbiotic corals were in close physical contact with BMA. The areal growth rate of the symbiotic corals was significantly higher than that of the aposymbiotic corals. The addition of nutrients to the culture seawater increased the chlorophyll a content in the symbiotic coral polyps and enhanced the growth of some of the symbiotic corals, however the average growth rate was not significantly affected, most likely because of the competition with BMA. The comparison between the symbiotic and aposymbiotic juvenile corals showed that the establishment of a symbiotic association could be imperative for post-settlement juvenile corals to survive in high-nutrient seawater.
Mostrar más [+] Menos [-]Characteristics of gas–phase nitric acid and ammonium–nitrate– sulfate aerosol, and their gas–phase precursors in a suburban area in Cairo, Egypt
2013
Hassan, Salwa K. | El–Abssawy, Ahmed A. | Khoder, Mamdouh I.
Simultaneous measurements of gaseous SO2, NO2, HNO3, NH3 and particulate SO42–, NO3– and NH4+ were carried out in a suburban area in Cairo during summer 2009 and winter 2009–2010. PTFE membrane filters were used to collect particulate SO42–, NH4+ and NO3–, followed by the impregnated filter to collect HNO3. Colorimetric methods were used for determination of NO2, SO2, NH3, SO42–, NH4+ NO3–, and HNO3 levels. The mean concentrations of NO2, SO2 and NH3 were 75.0, 40.1 and 29.1 µg/m3 in winter and 54.1, 25.1 and 44.9 µg/m3 in summer, respectively. The daytime/nighttime concentration ratios were 1.3 and 1.2 for NO2, 1.3 and 1.2 for SO2 and 0.6, and 0.8 for NH3 during the winter and summer, respectively. The mean values of NH4+, SO42–, NO3–, HNO3 and total NO3– were 4.4, 19.0, 3.4, 1.1 and 4.5 µg/m3 in winter and 7.5, 28.0, 4.2, 3.1 and 7.3 µg/m3 in summer, respectively. The levels of NH4+, SO42–, NO3– and HNO3 were relatively higher in daytime than in nighttime. Sulfur conversion (Fs) and nitrogen conversion ratios (Fn) in summer were about 1.78 and 2.15 times higher than in winter, respectively. Fs and Fn were higher in daytime than in nighttime. Significant positive correlation was found between Fs and relative humidity. The positive correlation between Fn and relative humidity was insignificant. The correlation between the concentration of NH4+ and NO3– indicates that NO3– may be found in fine mode (NH4NO3) in winter and it may be present predominantly as a coarse mode, such as Ca(NO3)2, Mg(NO3)2 and NaNO3 in summer. The concentration of SO42– was significantly correlated with NH4+ concentration, suggesting neutralization by NH3 and indicating that the forms of (NH4)2SO4 and/or NH4HSO4 exist in the aerosol. The NH4+/SO42– molar ratio indicates that SO42– in aerosol may be present as (NH4)2SO4, (NH4)2SO4.CaSO4.2H2O and CaSO4.
Mostrar más [+] Menos [-]Chemical composition, diurnal variation and sources of PM2.5 at two industrial sites of South China
2013
Huang, Bo | Liu, Ming | Ren, Zhaofang | Bi, Xinhui | Zhang, Guohua | Sheng, Guoying | Fu, Jiamo
Diurnal PM2.5 samples were collected during summer and winter at an industrial complex site (site A) and an electronic waste (e–waste) recycling site (site B) in Qingyuan, South China. The concentration of organic carbon (OC), elemental carbon (EC), water soluble ions (WSI) and elements were investigated for their seasonal and diurnal variations. Organic matter (OM) was the most abundant specie in winter, accounting for 40.2% and 48.8% of PM2.5 in sites A and B, respectively; while in summer, excluding the elemental portion, WSI was the biggest part, which accounted for 37% and 49.4% of PM2.5 mass in sites A and B, respectively. Significantly higher concentrations were observed for most of the analyzed chemical species in winter. Average acidity of PM2.5 at both sites was significantly higher in summer. Diurnal variation with elevated concentrations of PM2.5 in nighttime samples was found at site B. Secondary inorganic aerosols (NH4+, NO3− and SO42−) exhibited clear day–to–night variation. Concentration of SO42− was about 15% higher in daytime samples. NH4+ and NO3− co–varied in winter, but were weakly associated with each other in summer. Sites A and B samples were almost all ammonium–rich in winter, whereas the summer samples were ammonium–poor during the daytime but ammonium–rich in the night. Positive matrix factorization (PMF) model analysis showed that secondary formation, biomass burning, regional industries, coal combustion and dust had significant contribution to PM2.5. Among them, secondary formation and biomass burning together contributed approximately 50% of PM2.5 mass at both sites. Additionally e–waste recycling activities resulted in high pollution of Cu at Site B.
Mostrar más [+] Menos [-]Biomonitoring of 2,4’–methylene diphenyldianiline for assessment of exposure to methylene diphenyl diisocyanate aerosol
2013
Mirmohammadi, Seyedtaghi | Najafpour, Ghasem | Ahmad, Anees | Hakimi, Ibrahim
The exposure to methylene diphenyl diisocyanate (MDI) aerosol was investigated by biomnitoring of 2,4’–methylene diphenyldianiline (MDA) in urines of exposed workers. Biological monitoring was done for its metabolite by the analysis of isocyanate–derived diamines released from protein adducts in urine or plasma by GC–MS. The urine samples, at the end of working shifts of polyurethane factory, were collected in polystyrene bottles containing 10 g citric acid, and stored at 4 °C until analysis. The mean concentration values of MDA in the five selected factories were in the range of 3.01 to 3.58 µmol/mol creatinine for all subjects and the highest mean value of MDI concentration was 99 µg/m³ from indoor air samples analysis. The results show a linear relationship between MDI and MDA concentrations with a value of R2=0.801 (P<0.05). This study demonstrates that not only urinary MDA is detectable following diisocyanates aerosol exposure but also it is likely to be a useful practical biomarker to monitor diisocyanates exposure in the workplaces or for the epidemiologic studies.
Mostrar más [+] Menos [-]A baseline assessment of beach debris and tar contamination in Bonaire, Southeastern Caribbean
2013
Debrot, Adolphe O. | van Rijn, Jimmy | Bron, Patrick S. | de León, Ramon
Data on beach debris and tar contamination is provided for 21 natural beach sites in Bonaire, Southeastern Caribbean. Transects amounting to a combined length of 991m were sampled March–May 2011 and a total of 8960 debris items were collected. Highest debris and tar contamination were found on the beaches of the windward east-coast of the island where geometric mean debris concentrations (± approx. 70% confidence limits) were 115±58itemsm−1 and 3408±1704gm−1 of beach front. These levels are high compared to data collected almost 20years earlier on the nearby island of Curaçao. Tar contamination levels averaged 223gm−1 on windward beaches. Contamination levels for leeward west-coast beaches were generally two orders of magnitude less than windward beaches.
Mostrar más [+] Menos [-]Trace metal enrichments in nearshore sediments and accumulation in mussels (Modiolus capax) along the eastern coast of Baja California, Mexico: Environmental status in 1995
2013
Muñoz-Barbosa, Albino | Huerta-Diaz, Miguel Angel
The biogeochemistry of trace metals in nearshore sediments and mussel was studied at 15 stations along a 1000km long transect paralleling the west coast of the Gulf of California (GOC). Total trace metal (Me) and enrichment factor (EFMe) values in sediments were low due to negligible anthropogenic influence in the region. Past copper mining, however, near Santa Rosalia caused concentrations of Pb, Mn, Co, Zn and Cu which were 10–3.3×103 times greater than the average for the rest of the transect. Mussels also showed relatively high trace metal concentrations at the Santa Rosalia stations, but the variability in the spatial distribution was low and had undefined trends. Our results show that, with the exception of Co and Cu, the contamination caused by the copper mine affected sediments to a greater extent than mussels.
Mostrar más [+] Menos [-]Enhanced ex situ bioremediation of crude oil contaminated beach sand by supplementation with nutrients and rhamnolipids
2013
Nikolopoulou, M. | Pasadakis, N. | Norf, H. | Kalogerakis, N.
Mediterranean coastal regions are particularly exposed to oil pollution due to extensive industrialization, urbanization and transport of crude and refined oil to and from refineries. Bioremediation of contaminated beach sand through landfarming is both simple and cost-effective to implement compared to other treatment technologies. The purpose of the present study was to investigate the effect of alternative nutrients on biodegradation of crude oil contaminated beach sand in an effort to reduce the time required for bioremediation employing only indigenous hydrocarbon degraders.A natural sandy soil was collected from Agios Onoufrios beach (Chania, Greece) and was contaminated with weathered crude oil. The indigenous microbial population in the contaminated sand was tested alone (control treatment) or in combination with inorganic nutrients (KNO3 and K2HPO4) to investigate their effects on oil biodegradation rates. In addition, the ability of biosurfactants (rhamnolipids), in the presence of organic nutrients (uric acid and lecithin), to further stimulate biodegradation was investigated in laboratory microcosms over a 45-day period.Biodegradation was tracked by GC/MS analysis of aliphatic and polycyclic aromatic hydrocarbons components and the measured concentrations were corrected for abiotic removal by hopane normalizations. It was found that the saturated fraction of the residual oil is degraded more extensively than the aromatic fraction and the bacterial growth after an incubation period of approximately 3weeks was much greater from the bacterial growth in the control.The results show that the treatments with inorganic or organic nutrients are equally effective over almost 30days where C12–C35n-alkanes were degraded more than 97% and polyaromatic hydrocarbons with two or three rings were degraded more than 95% within 45days. The results clearly show that the addition of nutrients to contaminated beach sand significantly enhanced the activity of indigenous microorganisms, as well as the removal of total recoverable petroleum hydrocarbons (TRPH) over a 45-day study period.
Mostrar más [+] Menos [-]