خيارات البحث
النتائج 711 - 720 من 3,243
A drifter for measuring water turbidity in rivers and coastal oceans
2015
Marchant, Ross | Reading, Dean | Ridd, James | Campbell, Sean | Ridd, Peter
A disposable instrument for measuring water turbidity in rivers and coastal oceans is described. It transmits turbidity measurements and position data via a satellite uplink to a processing server. The primary purpose of the instrument is to help document changes in sediment runoff from river catchments in North Queensland, Australia. The ‘river drifter’ is released into a flooded river and drifts downstream to the ocean, measuring turbidity at regular intervals. Deployment in the Herbert River showed a downstream increase in turbidity, and thus suspended sediment concentration, while for the Johnstone River there was a rapid reduction in turbidity where the river entered the sea. Potential stranding along river banks is a limitation of the instrument. However, it has proved possible for drifters to routinely collect data along 80km of the Herbert River. One drifter deployed in the Fly River, Papua New Guinea, travelled almost 200km before stranding.
اظهر المزيد [+] اقل [-]Evaluation of beach cleanup effects using linear system analysis
2015
Kataoka, Tomoya | Hinata, Hirofumi
We established a method for evaluating beach cleanup effects (BCEs) based on a linear system analysis, and investigated factors determining BCEs. Here we focus on two BCEs: decreasing the total mass of toxic metals that could leach into a beach from marine plastics and preventing the fragmentation of marine plastics on the beach. Both BCEs depend strongly on the average residence time of marine plastics on the beach (τr) and the period of temporal variability of the input flux of marine plastics (T). Cleanups on the beach where τr is longer than T are more effective than those where τr is shorter than T. In addition, both BCEs are the highest near the time when the remnants of plastics reach the local maximum (peak time). Therefore, it is crucial to understand the following three factors for effective cleanups: the average residence time, the plastic input period and the peak time.
اظهر المزيد [+] اقل [-]Preliminary assessment of size distribution of airborne metals and metalloids in the urban aerosols of Guiyang, southwest China
2015
Zhang, Guoping | Li, Haixia | Wei, Xiaofei | Fu, Zhiping
Size–fractionated (7 fractions from <0.39 up to ≥10.2μm) airborne particulate matter (PM) was collected from Guiyang, southwest China. The concentrations of Al, Ti, Mn, Fe, Cu, Zn, As, Sr, Mo, Cd, Sb, Ba, and Pb in PM and the water–soluble concentrations of these elements were determined by inductively coupled plasma mass spectrometry. Compared to most other large cities in China, the total suspended particulate (TSP), PM10.2, and PM2.1 concentrations in Guiyang were at relatively low levels (59.1–222, 48.6–192, and 33.2–131μg/m3). This is consistent with the small industrial scale of this city. In the winter, coal combustion was proven to be the dominant source of airborne PM, whereas in other seasons, road dust resuspension was considered the primary source. Al, Ti, Fe, Sr, and Ba were highly associated with soil particles in the road dust. Cu and Zn could be associated with vehicle emissions that accumulated in road dust, while As, Mo, Cd, Sb, and Pb (and another portion of Zn) could be associated with main local industrial emissions. Compared to the coarse PM, the fine PM typically exhibited lower concentrations of crustal elements but higher concentrations of anthropogenic elements. The anthropogenic elements exhibited higher water solubility than crustal elements. Almost all of the elements in the PM in the winter exhibited the highest water solubility because of the lowest pH of the PM in this season.
اظهر المزيد [+] اقل [-]Source apportionment analysis of airborne VOCs using positive matrix factorization in industrial and urban areas in Thailand
2015
Saeaw, Neungrothai | Thepanondh, Sarawut
Airborne volatile organic compounds (VOCs) concentration data from monitoring stations in industrial and urban (Bangkok) area of Thailand were analyzed using Positive Matrix Factorization (PMF) to identify and elaborate on their source profiles. Analyzed data were obtained from those measured from January 2009 to December 2013 in the study area. The PMF was performed to estimate the contribution of specific source types to ambient concentrations. The most suitable number of factors for a dataset in this study was found to be eleven factors for compositions and characteristics of VOCs. Emission sources of VOCs in industrial area were classified into three to five groups based on their contribution. In industrial area, 42 to 57% of total VOC concentrations were contributed from mobile sources. Contribution to total VOCs concentration from industrial processes and household chemical usage were about 15 to 44% and 3 to 10%, respectively. Moreover, some species of VOCs particularly the ozone depleting substances such as Freon 11, Freon 114 and carbon tetrachloride were found as background concentration in ambient air. As for Bangkok, it was found that most of total VOC concentrations were contributed from mobile source emissions.
اظهر المزيد [+] اقل [-]An almost completed pollution-recovery cycle reflected by sediment geochemistry and benthic foraminiferal assemblages in a Swedish–Norwegian Skagerrak fjord
2015
Polovodova Asteman, Irina | Hanslik, Daniela | Nordberg, Kjell
During the 20th century Idefjord was considered one of the most polluted marine areas in Scandinavia. For decades it received high discharges from paper/pulp industry, which made it anoxic and extremely polluted by heavy metals and organic contaminants. Today the fjord is close to fulfil a complete pollution-recovery cycle, which is recorded in its sediment archives. Here we report results from five sediment cores studied for TC, C/N, heavy metals and benthic foraminifera. All of the cores have laminations deposited during 1940–1980s and indicative of long-lasting anoxia; high TC and heavy metal content, poor foraminiferal faunas and lack of macrofauna. The upper part of the cores deposited since 1980s shows a gradual pollutant decrease and partial foraminiferal recovery. The majority of foraminiferal species in Idefjord are agglutinated opportunistic and stress-tolerant taxa, which to some extent tolerate hypoxia and are early colonisers of previously disturbed environments. The current study demonstrates a value of benthic foraminiferal stratigraphy as a useful tool in understanding processes driving environmental degradation and recovery of coastal ecosystems.
اظهر المزيد [+] اقل [-]Arsenic fractionation in estuarine sediments: Does coastal eutrophication influence As behavior?
2015
Sá, Fabian | Sanders, Christian J. | Patchineelam, Sambasiva Rao | Machado, Eunice da Costa | Lombardi, Ana Teresa
The Paranaguá Estuarine Complex (PEC) includes the naturally oligotrophic (NO) Mel Island which is surrounded by sea grasses, a naturally eutrophic (NE) Benito Inlet adjacent to mangrove wetlands and the highly impacted eutrophic (IE) Paranaguá Bay, home of one of Brazil’s largest ports. The results from this study indicate that reactive As and pyrite increase with sediment depth near Paranaguá port in the IE region. At the NE region, near a mangrove fringe, the reactive As, Fe, Mn and pyrite remained relatively high along the sediment column while near the sea grasses at NO the As contents were low. The degree of trace metal pyritization (DTMP) and the degree of pyritization (DOP) was highest at the IE site, slightly increasing with depth. These baseline results indicate that influence of trophic conditions and presence of marine vegetation may be directly related to As behavior in coastal systems.
اظهر المزيد [+] اقل [-]Distributions and sources of volatile chlorocarbons and bromocarbons in the Yellow Sea and East China Sea
2015
Yang, Bin | Yang, Gui-Peng | Lu, Xiao-Lan | Li, Li | He, Zhen
Six volatile halogenated organic compounds (VHOC), namely, chloroform, carbon tetrachloride, trichloroethylene, bromodichloromethane, dibromochloromethane, and bromoform, were studied in the Yellow Sea and East China Sea from April to May, 2009. The spatial variability of these VHOC was influenced by various factors, including anthropogenic inputs, biogenic production and complicated hydrographic features such as Changjiang Diluted Water, Yellow Sea Cold Water Mass, and Kuroshio Current. Diurnal study results showed that factors such as solar irradiation, biological activity, and tide affected the abundance of these VHOC. Correlation analyses revealed that bromodichloromethane was positively correlated with chlorophyll a in surface seawater. Principal component analysis suggested that chlorinated compounds like carbon tetrachloride originated from anthropogenic sources whereas brominated compounds such as bromodichloromethane originated from biogenic sources. Sources of other chlorinated and brominated compounds may not be governed by biological processes in the marine environment.
اظهر المزيد [+] اقل [-]Abundance, size and polymer composition of marine microplastics ≥10μm in the Atlantic Ocean and their modelled vertical distribution
2015
Enders, Kristina | Lenz, Robin | Stedmon, Colin A. | Nielsen, Torkel G.
We studied abundance, size and polymer type of microplastic down to 10μm along a transect from the European Coast to the North Atlantic Subtropical Gyre (NASG) using an underway intake filtration technique and Raman micro-spectrometry. Concentrations ranged from 13 to 501itemsm−3. Highest concentrations were observed at the European coast, decreasing towards mid-Atlantic waters but elevated in the western NASG. We observed highest numbers among particles in the 10–20μm size fraction, whereas the total volume was highest in the 50–80μm range. Based on a numerical model size-dependent depth profiles of polyethylene microspheres in a range from 10–1000μm were calculated and show a strong dispersal throughout the surface mixed layer for sizes smaller than 200μm. From model and field study results we conclude that small microplastic is ubiquitously distributed over the ocean surface layer and has a lower residence time than larger plastic debris in this compartment.
اظهر المزيد [+] اقل [-]The composition of PM1 and PM2.5 samples, metals and their water soluble fractions in the Bologna area (Italy)
2015
Sarti, Elena | Pasti, Luisa | Rossi, Mauro | Ascanelli, Monica | Pagnoni, Antonella | Trombini, Monica | Remelli, Maurizio
In this study the metal composition of PM1 and PM2.5 samples collected in the surroundings of a municipal incinerator located in a suburban–farming area, less than 10 km away from Northeast of Bologna (Italy) was investigated. Seven out of eight monitoring stations were installed in a domain of 8x9 km2 around the incinerator plant; the eighth station was placed inside the urban area of Bologna. The coordinates of four monitoring stations were selected on the basis of a preliminary study by using a dispersion model. Eleven metals (Al, Sb, As, Cd, Fe, Mn, Ni, Pb, Cu, V, Zn) were quantified in both the filter acid–digests and in the water extracts. The PM2.5 collected in all the sites of the domain were highly correlated with exception of the urban site. The daily average metal concentrations in summer were 1.84% and 1.14% for PM2.5 and PM1 respectively, indicating that fine particles are less enriched in metals. Fe, Al and Zn were the most abundant elements, and they represented about the 80% of the total amount of the analyzed ones. The average water soluble metal compositions were 0.71% and 0.41% for PM2.5 and PM1 respectively. In the sites of the suburban–farming studied area the Principal Component Analysis (PCA) and Cluster Analysis revealed differences between water soluble metal compositions in PM1 and PM2.5. The urban sites were characterized by lower total and soluble metals contents than the other PM2.5 stations installed around the incinerator plant. However, no noticeable difference in the concentrations of metals in the particulate matter between the sites chosen as maxima of incinerator emissions and the control sites was observed.
اظهر المزيد [+] اقل [-]Biomonitoring of airborne fluoride and polycyclic aromatic hydrocarbons in industrial areas of Cordoba, Argentina, using standardized grass cultures of Lolium multiflorum
2015
Judith Hebelen, Rodriguez | Eduardo Daniel, Wannaz | Jurgen, Franzaring | Andreas, Klumpp | Andreas, Fangmeier | Maria Luisa, Pignata
A biomonitoring study was performed employing standardized grass cultures. Plants of Lolium multiflorum were exposed at 4 industrial sites over three–month periods in two seasons (dry and rainy) and the biomass produced was used for subsequent measurements of fluoride, polycyclic aromatic hydrocarbons (phenanthrene, anthracene, pyrene, benzo[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenzo[a,h]–anthracene and benzo[g,h,i]perylene), total chlorophyll, malondialdehyde, water, and sulfur content. The total content of polycyclic aromatic hydrocarbons (PAHs) revealed seasonal variations, with the highest values corresponding to the dry season, although this species showed a high retention capacity of PAHs during rainy season. In addition, sampling sites with high vehicular traffic and metal–mechanical industries were associated with the highest content of PAHs. Furthermore, physiological degradation associated with anthropogenic activities in the sampling sites was observed. Fluoride content in the biomonitor was associated with the production and use of cement, which was higher in the dry season.
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