Black carbon-dominated PCDD/Fs sorption to soils at a former wood impregnation site

The influence of black carbon (BC) on the sorption of 17 native polychlorinated-p-dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) was studied in five soil samples from a sawmill site where wood used to be impregnated with chlorophenol preservatives. The presence of BC caused measured total organic carbon (TOC)-water distribution ratios (K(TOC)) to be a median factor of 51 (interquartile range 18-68, n=85) higher than modeled amorphous organic carbon (AOC)-water distribution ratios (K(AOC)). K(TOC) was a factor of 73+/-27 above K(AOC) for PCDFs (n=10) and a factor of 20+/-13 (n=7) for PCDDs. The reason for this difference is probably that attaining a planar configuration after sorption to BC is less thermodynamically favorable for PCDDs than for PCDFs. BC-water distribution ratios were calculated from K(TOC), K(AOC) and BC contents, and ranged from 10(9.9) (2,3,7,8-Tetra-CDD) to 10(11.5) l kg(-1) (Octa-CDF). More than 90% of the PCDD/Fs in the soil was calculated to be BC-sorbed. Dissolved organic carbon (DOC)-water distribution ratios were measured to be in the same order of magnitude as K(AOC). This study shows that strong sorption to BC should be included when assessing ecotoxicological risk or modeling transport to groundwater of PCDD/Fs in soil.     

Assessment of chemical and biochemical stabilization of organic C in soils from the long-term experiments at Rothamsted (UK)

Biological and chemical stabilization of organic C was assessed in soils sampled from the long-term experiments at Rothamsted (UK), representing a wide range of carbon inputs and managements by extracting labile, non-humified organic matter (NH) and humic substances (HS). Four sequentially extracted humic substances fractions of soil organic matter (SOM) were extracted and characterized before and after a 215-day laboratory incubation at 25 degrees C from two arable soils, a woodland soil and an occasionally stubbed soil. The fractions corresponded to biochemically stabilised SOM extracted in 0.5M NaOH (free fulvic acids (FA) and humic acids (HA)) and chemically plus biochemically stabilised SOM extracted from the residue with 0.1M Na4P2O7 plus 0.1M NaOH (bound FA and HA). Our aim was to investigate the effects of chemical and biochemical stabilization on carbon sequestration. The non-humic to humic (NH/H) C ratio separated the soils into two distinct groups: arable soils (unless fertilised with farmyard manure) had an NH/H C ratio between 1.05 and 0.71, about twice that of the other soils (0.51-0.26). During incubation a slow, but detectable, decrease in the NH/H C ratio occurred in soils of C input equivalent or lower to 4Mgha(-1)y(-1), whereas the ratio remained practically constant in the other soils. Before incubation the free to bound humic C ratio increased linearly (R2=0.91) with C inputs in the soils from the Broadbalk experiment and decreased during incubation, showing that biochemical stabilization is less effective than chemical stabilization in preserving humic C. Changes in delta13C and delta15N after incubation were confined to the free FA fractions. The delta13C of free FA increased by 1.48 and 0.80 per thousand, respectively, in the stubbed and woodland soils, indicating a progressive biological transformation. On the contrary, a decrease was observed for the bound FA of both soils. Concomitantly, a Deltadelta15N of up to +3.52 per thousand was measured after incubation in the free FA fraction and a -2.58 Deltadelta15N in the bound FA. These changes, which occurred during soil incubation in the absence of C inputs, indicate that free FA fractions were utilised by soil microorganisms, and bound FA were decomposed and replaced, in part, by newly synthesized FA. The 13CPMAS-TOSS NMR spectra of free HA extracted before and after 215 days of incubation were mostly unchanged. In contrast, changes were evident in bound HA and showed an increase in aromatic C after incubation.     

Derivation of new emission factors for quantification of mass emissions when using optical gas imaging for detecting leaks

This paper describes the development of new "leak/no-leak" emission factors that are suitable for estimating facilities' fugitive emissions when using an alternative work practice (AWP) that is based on optical gas imaging technology for detecting leaking piping system components. These emission factors were derived for valves, pumps, and connectors/flanges for instrument leak detection thresholds ranging from 3 to 60 g/hr using a combination of field data and Monte Carlo statistical simulation techniques. These newly derived leak/no-leak emission factors are designed to replace the U.S. Environment Protection Agency (EPA) 1995 Protocol factors, which were based on Method 21 monitoring of leaks at "uncontrolled" facilities. The emission factors published in the 1995 Protocol have not been updated since the 1970s. This derivation is based on results where the authors document the use of a Monte Carlo simulation technique to quantify the required leak detection thresholds that provide equal--or better--environmental benefits for an AWP. The use of these newly derived emission factors is demonstrated for different methods of computing fugitive emissions from a hypothetical model refinery. The resulting facility emissions calculated by using these new emission factors is compared with the existing emission estimation methods provided in the EPA 1995 Protocol. The results demonstrate that the new emission factors provide an emission estimate that is the closest to that obtained from the direct determination of total emissions by Monte Carlo simulations.     

Root establishment of perennial ryegrass (L. perenne) in diesel contaminated subsurface soil layers

The efficiency of rhizosphere biodegradation of petroleum hydrocarbons heterogeneously distributed in soils is dependent on the ability of plant roots to prospect into contaminated zones. Rhizobox experiments were conducted to study the influence of diesel contaminated layers on the spatial distribution and the development of the roots of perennial ryegrass. Root distribution and root and shoot development were monitored over time. The final root and above ground biomass and the final TPH concentration were determined. The spatial distribution of the contaminant as well as the irrigation method used affected root distribution, plant development and TPH degradation and therefore ryegrass remediation potential. The results show that roots colonise fully uncontaminated soil and grow preferentially between zones of contamination. Conversely, when no immediate uncontaminated soil is available, roots grow through contaminated zones in order to prospect for uncontaminated soil.     

Characterization of a fatty acid-binding protein from the Pacific oyster (Crassostrea gigas): pharmaceutical and toxicological implications

Environmental Science and Pollution Research - Pharmaceuticals and their metabolites constitute a class of xenobiotics commonly found in aquatic environments which may cause toxic effects in...     

Mediterranean alien harmful algal blooms: origins and impacts

Environmental Science and Pollution Research - Harmful algal blooms (HABs) are mostly phytoplankton blooms, which have detrimental environmental and socioeconomic impacts. The Mediterranean Sea due...     

Effect of eight common Brazilian drugs on Lemna minor and Salvinia auriculata growth

Environmental Science and Pollution Research - The growth of two species of macrophytes (Lemna minor and Salvinia auriculata) under the effect of a mixture of amoxicillin, caffeine, carbamazepine,...     

Monitoring of dust emission on gravel roads: Development of a mobile methodology and examination of horizontal diffusion

Traffic-generated fugitive dust on gravel roads impairs visibility and deposits on the adjacent environment. Particulate matter smaller than 10 μm in diameter (PM₁₀) is also associated with human health problems. Dust emission strength depends on the composition of granular material, road moisture, relative humidity, local climate (precipitation, wind velocity, etc.), and vehicle characteristics.The objectives of this study were to develop a reliable and rapid mobile methodology to measure dust concentrations on gravel roads, evaluate the precision and repeatability of the methodology and correspondence with the currently used visual assessment technique. Downwind horizontal diffusion was studied to evaluate the risk of exceeding the maximum allowed particulate matter concentration in ambient air near gravel roads according to European Council Directive [European Council Directive 1999/30/EC of 22 April 1999 relating to limit values for sulphur dioxide, nitrogen dioxide and oxides of nitrogen, particulate matter and lead in ambient air. Official Journal of the European Communities. L163/41.].A TSI DustTrak Aerosol Monitor was mounted on an estate car travelling along test sections treated with various dust suppressants. Measured PM₁₀ concentrations were compared to visual assessments performed at the same time. Airborne particles were collected in filters mounted behind the vehicle to compare the whole dust fraction with the PM₁₀ concentration. For measuring the horizontal diffusion, DustTraks were placed at various distances downwind of a dusty road section.The mobile methodology was vehicle and speed dependent but not driver dependent with pre-specified driving behaviours. A high linear correlation between PM₁₀ of different vehicles makes relative measurements of dust concentrations possible. The methodology gives continuous data series, mobility, and easy handling and provides fast, reliable and inexpensive measurements for estimating road conditions to make road maintenance more efficient.Good correlations between measured PM₁₀-values, visually assessed dust generation and dust collected in filters were obtained. PM₁₀ seems to be correlated to the whole dust fraction that impairs visibility on gravel roads.A decay in PM₁₀ concentration as a function of distance from the road was observed. Measured particles principally did not travel further than 45 m from the road. The risk of exceeding the PM₁₀ concentration stated in the EC-directive seems small.     

Removal of organic contaminants in bioretention medium amended with activated carbon from sewage sludge

Bioretention, also known as rain garden, allows stormwater to soak into the ground through a soil-based medium, leading to removal of particulate and dissolved pollutants and reduced peak flows. Although soil organic matter (SOM) is efficient at sorbing many pollutants, amending the bioretention medium with highly effective adsorbents has been proposed to optimize pollutant removal and extend bioretention lifetime. The aim of this research was to investigate whether soil amended with activated carbon produced from sewage sludge increases the efficiency to remove hydrophobic organic compounds frequently detected in stormwater, compared to non-amended soil. Three lab-scale columns (520 cm³) were packed with soil (bulk density 1.22 g/cm³); activated carbon (0.5% w/w) was added to two of the columns. During 28 days, synthetic stormwater—ultrapure water spiked with seven hydrophobic organic pollutants and dissolved organic matter in the form of humic acids—was passed through the column beds using upward flow (45 mm/h). Pollutant concentrations in effluent water (collected every 12 h) and polluted soils, as well as desorbed amounts of pollutants from soils were determined using GC-MS. Compared to SOM, the activated carbon exhibited a significantly higher adsorption capacity for tested pollutants. The amended soil was most efficient for removing moderately hydrophobic compounds (log K _ow 4.0–4.4): as little as 0.5% (w/w), carbon addition may extend bioretention medium lifetime by approximately 10–20 years before saturation of these pollutants occurs. The column tests also indicated that released SOM sorb onto activated carbon, which may lead to early saturation of sorption sites on the carbon surface. The desorption test revealed that the pollutants are generally strongly sorbed to the soil particles, indicating low bioavailability and limited biodegradation.

     

Value of biochars from Miscanthus x giganteus cultivated on contaminated soils to decrease the availability of metals in multicontaminated aqueous solutions

The objective of this study was to evaluate the sorption efficiency of eight biochars, made from Miscanthus x giganteus cultivated on contaminated agricultural soil, in aqueous solutions contaminated with metals alone or mixed with polycyclic aromatic hydrocarbons. These biochars were produced in different pyrolysis conditions (temperature, 400/600 °C; heating rate, 5/10 °C min⁻¹; duration, 45/90 min) and compared with an uncontaminated commercialized biochar made of wood. The physicochemical characterization of the Miscanthus biochars confirmed the impact of the pyrolysis on the biochar parameters with substantial differences between the biochars in terms of pH, cation exchange capacity, and specific surface area. The sorption experiment showed higher sorption efficiency of Cd, Pb, and Zn for the Miscanthus biochars produced at 600 °C compared with the biochars produced at 400 °C when the aqueous solutions were mono- or multicontaminated. Furthermore, the desorption study showed that the sorption process was largely irreversible. Therefore, the high sorption capacity of Miscanthus biochars and the low sorption reversibility confirmed that these biochars are a suitable sorbent for metals.