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Field performance of the radon-deficit technique to detect and delineate a complex DNAPL accumulation in a multi-layer soil profile
2021
Barrio-Parra, F. | Izquierdo-Díaz, M. | Díaz-Curiel, J. | De Miguel, E.
The performance of the radon (²²²Rn)-deficit technique has been evaluated at a site in which a complex DNAPL mixture (mostly hexachlorocyclohexanes and chlorobenzenes) has contaminated all four layers (from top to bottom: anthropic backfill, silt, gravel and marl) of the soil profile. Soil gas samples were collected at two depths (0.8 m and 1.7 m) in seven field campaigns and a total of 186 ²²²Rn measurements were performed with a pulse ionization detector. A statistical assessment of the influence of field parameters on the results revealed that sampling depth and atmospheric pressure did not significantly affect the measurements, while the location of the sampling point and ground-level atmospheric temperature did. In order to remove the bias introduced by varying field temperatures and hence to be able to jointly interpret ²²²Rn measurements from different campaigns, ²²²Rn concentrations were rescaled by dividing each individual datum by the mean ²²²Rn concentration of its corresponding field campaign. Rescaled ²²²Rn maps showed a high spatial correlation between ²²²Rn minima and maximum contaminant concentrations in the top two layers of the soil profile, successfully delineating the surface trace of DNAPL accumulation in the anthropic backfill and silt layers. However, no correlation could be established between ²²²Rn concentrations in superficial soil gas and contaminant concentration in the deeper two layers of the soil profile. These results indicate that the ²²²Rn-deficit technique is unable to describe the vertical variation of contamination processes with depth but can be an effective tool for the preliminary characterization of sites in which the distance between the inlet point of the sampling probe and the contaminant accumulation falls within the effective diffusion length of ²²²Rn in the affected soil profile.
Mostrar más [+] Menos [-]Dropping the microbead: Source and sink related microplastic distribution in the Black Sea and Caspian Sea basins
2021
D'Hont, Anouk | Gittenberger, Adriaan | Leuven, Rob S.E.W. | Hendriks, A Jan
Microplastic pollution is a growing, yet poorly understood problem. Here, we assessed the relationship between microplastic concentration and distance to rivers, shorelines, cities, sediment grain size or water depth in sediments of the world's largest (semi-)enclosed aquatic basins. Microplastic was extracted from sediment using density separation, elutriation and hydrophobic adhesion. Fibers and transparent or white microplastic particles were the most abundant shape and color. The microplastic concentration in sediments of the Black Sea was about twice as high compared to that in the Caspian Sea. Fragment concentrations decreased with depth, while fiber concentrations were independent of depth. Overall, no relationship with distance to shores, rivers and cities or with grain size was observed. However, within some depth classes concentrations were related to the distance from rivers, shores and cities.
Mostrar más [+] Menos [-]Reducing spatial variation in environmental assessment of marine benthic fauna
2016
Leonardsson, Kjell | Blomqvist, Mats | Rosenberg, Rutger
The Benthic Quality Index, BQI, is widely used for benthic quality assessment. Here, we investigated if spatial variation in the BQI can be reduced by accounting for the environmental factors instead of having different boundaries for different salinity regimes between status classes in the EU Water Framework Directive and Marine Strategy Framework Directive. For this purpose we tested salinity, sediment structure, and depth in a regression model to test their contribution to variations in BQI. The spatial variation in BQI was better explained by depth than by salinity or sediment structure. The proposed assessment method uses the residuals from the regression model between BQI and depth. With this method the variance in BQI between samples was reduced by 50% to 75% in the majority of situations. A method to establish the boundary between good and moderate status and how to derive EQR-values according to the WFD is presented.
Mostrar más [+] Menos [-]Soil lead levels in orchards and roadsides of mission Peninsula, Michigan
1997
Francek, Mark A.
The Pb content in orchard soils at Mission Peninsula, Michigan was determined to assess the impact of historical lead arsenate applications. Soil samples at 72 sites located in five orchards were collected at depths of 2−, 20-, 50−, and 100 cm. Atomic absorption spectroscopy was used to quantify Pb levels (jig g⁻¹). Mean surface Pb levels at individual orchards ranged from <1–136 pg g⁻¹ and rapidly decreased with depth, to < 1-5 μg g⁻¹ at 100 cm. The impact of textural class and slope angle on Pb levels was also analyzed. Correlation coefficients linking Pb levels with textural class were weak, ranging from 0.21 to −0.07. Varying slope steepness and slope position within orchards failed to affect the spatial pattern of soil Pb.Soil Pb levels were also compared at 5 sites along local roads with varying levels of automobile traffic. Samples were collected 1 m from the roadside at the same depth intervals studied in orchards. Average daily traffic along the busiest roadsites ranged from 8200 to 16 000; these sites had Pb levels of 90–210 μg g⁻¹. Such locales had Pb levels similar to the more intensively sprayed orchards.
Mostrar más [+] Menos [-]Soil nutrient leaching in response to simulated acid rain treatment
1987
Kelly, J.M. (Tennessee Valley Authority, Muscle Shoals, AL (USA). Div. of Air and Water Resources, Air Quality Branch) | Strickland, R.C.
Trace metals in the forest floor at Saddleback Mountain, Maine in relation to aspect, elevation, and cover type
1987
Moyse, D.W. (Maine Univ., Orono (USA). Dept. of Plant and Soil Sciences) | Fernandez, I.J.
Organophosphorus flame retardants and plasticizers in water samples of the Rhine, Ems and Elbe Rivers in 2013
2017
Wolschke, Hendrik | Sühring, Roxana | Xie, Zhiyong | Ebinghaus, Ralf
This study reports the occurrence and distribution of organophosphorus flame retardants and plasticizers (OPEs) in the Elbe and Rhine rivers. A special focus of this investigation concerns the potential impacts of a major flood event in 2013 on the OPE patterns and levels in the Elbe River. In this river, 6 of 13 OPEs were detected, with tris-ethyl-phosphate (TEP, 168 ± 44 ng/L), tris-1,3-dichloro-2-propyl-phosphate (TDCPP, 155 ± 14 ng/L) and tris-1-chloro-2-propyl phosphate (TCPP, 126 ± 14 ng/L) identified as the dominant compounds. Relative to previous studies, an increase in the concentrations and relative contributions of TDCPP to the total level of OPEs was observed, which was likely caused by its increased use as a replacement for the technical pentaBDE formulation. During the flood event, the concentrations of OPEs were similar to the normal situation, but the mass fluxes increased by a factor of approximately ten (~16 kg/d normal versus ~160 kg/d flood peak). No input hotspots were identified along the transects of the Elbe and Rhine rivers, and the mass flux of OPEs appeared to be driven by water discharge.
Mostrar más [+] Menos [-]Comparison of soil thermal regimes in a deforested area with various grass cover in the Beskids Mts. [Czech Republic]
1998
Tuma, I. (Akademie Ved, Brno (Czech Republic). Ustav Ekologie Krajiny)
The studies of grass communities, which spread in deforested areas, also involved observations of soil thermal regimes. Three sites were chosen in order to determine differences in diurnal and seasonal variations of soil temperatures: (1) open site (barren) without plant cover, (2) site covered by a young, lower and thinner stand of Avenella flexuosa, and (3) old, dense stand of Calamagrostis villosa with a layer of plant litter on the soil surface. Soil temperatures were measured at the soil surface and in the soil depth of 5 and 10 cm. In summer months, the greatest differences in maximal temperatures recorded at the soil surface and at the 5, 10 cm depth between the bare site and the old stand of C. villosa represented 21.6, 15.9, 12.4 deg C, respectively. Soil temperatures measured in the bare plot in autumn months were lower than those in grass stands.
Mostrar más [+] Menos [-]Organic UV stabilizers and UV filters in the sediment of Chinese Bohai and Yellow Seas in 2016
2018
Apel, Christina | Tang, Jianhui | Ebinghaus, Ralf
Organic UV stabilizers and UV filters are applied to industrial materials and cosmetics worldwide. In plastics they prevent photo-induced degradation, while in cosmetics they protect human skin against harmful effects of UV radiation. This study reports on the occurrence and distribution of organic UV stabilizers and UV filters in the surface sediment of the Chinese Bohai and Yellow Seas for the first time. In total, 16 out of 21 analyzed substances were positively detected. Concentrations ranged from sub-ng/g dw to low ng/g dw. The highest concentration of 25 ng/g dw was found for octocrylene (OC) in the Laizhou Bay. In the study area, characteristic composition profiles could be identified. In Korea Bay, the dominating substances were OC and ethylhexyl salicylate (EHS). All other analytes were below their method quantification limit (MQL). Around the Shandong Peninsula, highest concentrations of benzotriazole derivatives were observed in this study with octrizole (UV-329) as the predominant compound, reaching concentrations of 6.09 ng/g dw. The distribution pattern of UV-329 and bumetrizole (UV-326) were related (Pearson correlation coefficient r > 0.98, p << 0.01 around the Shandong Peninsula), indicating an identical input pathway and similar environmental behavior.
Mostrar más [+] Menos [-]Micro-fibre content of South Africa's sandy beach sediments from 2016 to 2017
2017
de Villiers, Stephanie
In 2016 and 2017 the Department of Environmental Affairs conducted sampling at more than 150 sandy beach sites along the South African coastline, to quantify the extent of micro-plastic pollution at an average spatial sampling scale of about 15 km. Most of the sites along the west coast were sampled 3 times, to investigate seasonal variability. The east and south coasts were sampled twice, during low and higher river runoff conditions, respectively. At all sites, plastic micro-fibres were found to be the dominant micro-plastic constituents present, and the quantitative data for that is presented in this dataset. One of the problematic issues related to comparison of global micro-plastic pollutant levels, presently, is the lack of agreed to measurement methodologies and reporting units. This dataset represents results for samples taken along the high-level water mark, as a composite sample of about 1 L consisting of aliquots taken from at least 3 different sampling spots, sampled to a depth of 5 cm. The micro-fibre count is reported as the number of fibres per liter (or #F/dm3). In order to convert this to other units for comparison with other studies, sediment dry bulk density measurements are included. Data is also provided for the dominant sediment grain size (fine sand is 63 to 250 µm, and medium-coarse sand 250 µm to 1 mm) , and the temperature and salinity of surf-zone water at the time of sampling.
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