Acid Volatile Sulfides,Equilibrium Partitioning,and Hazardous Waste Site Sediments

/ Information provided by acid volatile sulfide (AVS) andequilibrium partitioning (EqP) theory is described, including two caseexamples, relative to hazardous waste site sediments. AVS and EqP are toolsin the toolbox, which can serve three main functions: screening,prioritization, and assisting in explaining observed effects. They should notbe used in isolation for decision making, particularly at hazardous waste orother sites where the sediments are contaminated by materials such as coal,coke, and pitch.KEY WORDS: Acid volatile sulfides; Equilibrium partitioning; Sediments;Hazardous waste     

GROUND WATER FLOW AND RUNOFF IN A COASTAL PLAIN STREAM1

ABSTRACT: The quantity, seasonality, and sources of flow were analyzed for two segments of Four Mile Branch, a small stream on the Coastal Plain of South Carolina using data obtained from USGS gauging stations. Flows in the “upstream segment,” a 12.6-km² watershed comprising the head waters of Four Mile Branch, averaged 0.129 m³ s^?1 and showed a distinctly seasonal pattern, with maximum flows in February and March and minimum flows in September and October. Inflow to the “downstream segment,” a 2.2-km² watershed associated with the main channel, averaged 0.059 m³ s^?1 and showed no seasonal patterns. Discharges per unit area of watershed were greater for the downstream segment, 0.83 m³ per year per m² of land surface, than for the upstream segment, 0.32 m³ per year per m². The differences in discharge rates and seasonalities between the two segments reflect differences in aquifers supplying the different segments. Analyses of Streamflow by hydrograph separation and Streamflow partitioning methods indicated that greater than 90 percent of the flows in the upstream and downstream segments were due to ground water-driven base flows.     

Relation of enhanced Pb solubility to Fe partitioning in soils

It is well documented that Pb solubility may be related to Fe chemistry in soils and enhanced Pb solubility may occur under certain reducing conditions; however, quantification of such relationships is unavailable. Based on metal classification, Pb (II) and Fe (II) are similar in some chemical characteristics. Thus, competition between Pb and Fe for ligands in soils may be important in determining Pb solubility. In this paper, Pb solubility was examined in a sandy soil after spiking with Pb and incubating for 40 days under water-flooded or non-water-flooded conditions. Solution chemistry in soil columns was adjusted using different concentrations of NaCl, CaCl(2) and deionized water of varying pH before incubation. The results showed that Pb solubility in the soil was not correlated well with pH, dissolved organic C or aqueous Fe concentrations. However, an index of Fe partition behavior using the ratio of aqueous Fe to sorbed Fe was related to Pb solubility. Enhanced Pb solubility occurred only when the index was < approximately 2 kg l(-1). The index can be a simple measure of Fe's ability to compete with Pb for ligands in solution. The ability of Fe to compete with Pb decreases as the index decreases and as the ratio approached its minimum, substantial increases in Pb solubility will be expected. In general, the index was not sensitive to changes in solution chemistry. A similar trend was observed using one data set published in the literature.     

粤港澳大湾区大气中硝基多环芳烃污染特征与风险评估

为探究粤港澳大湾区硝基多环芳烃(NPAHs)污染特征与来源,利用大气主动采样技术采集44个环境空气样品,并使用气相色谱-三重四级杆串联质谱测定NPAHs浓度.结果表明,同时使用滤膜、PUF和XAD-2树脂,可以更高效采集到气态和颗粒态的NPAHs,准确表征环境空气中NPAHs的污染状况.粤港澳大湾区环境空气中ρ(∑18...     

深圳市空气中多氯联苯污染的初步研究

于2001年春季使用大流量采样器对深圳市气相和颗粒相空气样品进行采集,分析其中的多氯联苯(PCBs)的含量和分布,计算出PCBs的氯数分布和气 固两相之间的分配,并将所得结果与国外的同类研究进行了对比。结果表明,深圳市空气中PCBs的质量浓度处于中等污染水平;与国外同类研究相比,深圳市空气中颗粒相PCBs的质量浓度贡献远高于其他地区的对应值;lgKp与lgPL0线性回归分析表明,深圳市空气中的PCBs接近气 固分配的平衡状态。      

Simulation of arsenic partitioning in tributaries to drinking water resevoirs

Arsenic released by bottom sediments was determined by experiments in which the sediments were artificially re-suspended using a particle entrainment simulator (PES) to simulate river conditions. Sediment cores were collected from various tributaries to drinking water reservoirs in Connecticut spiked with arsenic, and run in the PES at simulated bed-flow shear stresses from 0.0 to 0.6 N/m². Under equilibrium conditions, the dissolved fraction of arsenic was found to range from 8.3 to 22.1 μg/l, which in most cases exceeded EPA Maximum Contaminant Level (MCL) of 10 μg/l. Experimental results from these simulations have shown that bed-flow shear stress causes an increased concentration of dissolved arsenic, most notably at shear stresses of 0.4, 0.5, and 0.6 N/m². For the solid phase under equilibrium, the concentrations of arsenic ranged between 71 and 275 mg/kg. The average concentration of arsenic on the solid phase as well as partitioning coefficient values (K _p) were highest at initial shear stress. This was attributed to the higher fraction of colloidal material and finer organic particles in the suspended solid mixture. Particles of such nature proved to have higher affinity to arsenic. K _p values were determined from PES data and were found to range from 4,687 to 24,090 l/kg. However, on a mass load basis, the amount of arsenic found in suspended sediment increased with the increase of shear stress. Similarly, the amount of arsenic in the solid phase increased significantly for sites with high Volatile Organic Carbon (VOC) content. Because of the influence of Total Suspended Solids (TSS) and VOC concentrations on K _p, the use of the PES is more appropriate in obtaining K _p values that would be found under real stream conditions when compared to the traditional way of measuring K _p using a jar study technique.     

Sampling and Analysis of Organic Compounds in Diesel Particulate Matter

The fraction of atmospheric semi-volatile organic compounds (SVOC) is partitioned between the gaseous and particulate phases. Certain of these compounds eg. polynuclear aromatic hydrocarbons (PAH) and their derivatives have been shown to exhibit mutagenic or carcinogenic properties. Emissions from diesel engines are an important source of these contaminants. In a dilution chamber, we studied a diesel engine emissions. It is shown firstly, that the gaseous fraction is predominant (by up to 20 times) with respect to the particulate phase. Secondly, the polar compounds, neglected in the majority of previous studies, are the predominant species. A test campaign was carried out in Paris-Porte d'Auteuil which yielded similar results to the laboratory experiments.     

Selenium assimilation and loss by an insect predator and its relationship to Se subcellular partitioning in two prey types

Subcellular selenium (Se) distributions in the oligochaete Tubifex tubifex and in the insect Chironomus riparius did not vary with Se exposure duration, which was consistent with the observations that the duration of prey Se exposure had little influence on either Se assimilation or loss by a predatory insect (the alderfly Sialis velata). However, these two prey types differed in how Se was distributed in their cells. Overall, the predator assimilated a mean of 66% of the Se present in its prey, which was similar to the mean percentage of Se in prey cells (62%) that was theoretically available for uptake (that is, Se in the protein and organelle fractions). Likewise, data for cadmium, nickel and thallium suggest that predictions of trace element transfer between prey and predator are facilitated by considering the subcellular partitioning of these contaminants in prey cells.     

Atmospheric partitioning and the air–water exchange of polycyclic aromatic hydrocarbons in a large shallow Chinese lake (Lake Chaohu)

The residual levels of polycyclic aromatic hydrocarbons (PAHs) in the atmosphere and in dissolved phase from Lake Chaohu were measured by (GC–MS). The composition and seasonal variation were investigated. The diffusive air–water exchange flux was estimated by a two-film model, and the uncertainty in the flux calculations and the sensitivity of the parameters were evaluated. The following results were obtained: (1) the average residual levels of all PAHs (PAH16) in the atmosphere from Lake Chaohu were 60.85 ± 46.17 ng m⁻³ in the gaseous phase and 14.32 ± 23.82 ng m⁻³ in the particulate phase. The dissolved PAH16 level was 173.46 ± 132.89 ng L⁻¹. (2) The seasonal variation of average PAH16 contents ranged from 43.09 ± 33.20 ng m⁻³ (summer) to 137.47 ± 41.69 ng m⁻³ (winter) in gaseous phase, from 6.62 ± 2.72 ng m⁻³ (summer) to 56.13 ± 22.99 ng m⁻³ (winter) in particulate phase, and 142.68 ± 74.68 ng L⁻¹ (winter) to 360.00 ± 176.60 ng L⁻¹ (summer) in water samples. Obvious seasonal trends of PAH16 concentrations were found in the atmosphere and water. The values of PAH16 for both the atmosphere and the water were significantly correlated with temperature. (3) The monthly diffusive air–water exchange flux of total PAH16 ranged from −1.77 × 10⁴ ng m⁻² d⁻¹ to 1.11 × 10⁵ ng m⁻² d⁻¹, with an average value of 3.45 × 10⁴ ng m⁻² d⁻¹. (4) The results of a Monte Carlo simulation showed that the monthly average PAH fluxes ranged from −3.4 × 10³ ng m⁻² d⁻¹ to 1.6 × 10⁴ ng m⁻² d⁻¹ throughout the year, and the uncertainties for individual PAHs were compared. (5) According to the sensitivity analysis, the concentrations of dissolved and gaseous phase PAHs were the two most important factors affecting the results of the flux calculations.     

Statistical uncertainty in hazardous terrestrial concentrations estimated with aquatic ecotoxicity data

Since chemicals’ ecotoxic effects depend for most soil species on the dissolved concentration in pore water, the equilibrium partitioning (EP) method is generally used to estimate hazardous concentrations (HC50) in the soil from aquatic toxicity tests. The present study analyzes the statistical uncertainty in terrestrial HC50s derived by the EP-method. For 47 organic chemicals, we compared freshwater HC50s derived from standard aquatic ecotoxicity tests with porewater HC50s derived from terrestrial ecotoxicity tests. Statistical uncertainty in the HC50s due to limited species sample size and in organic carbon–water partitioning coefficients due to predictive error was treated with probability distributions propagated by Monte Carlo simulations. Particularly for specifically acting chemicals, it is very important to base the HC50 on a representative sample of species, composed of both target and non-target species. For most chemical groups, porewater HC50 values were approximately a factor of 3 higher than freshwater HC50 values. The ratio of the porewater HC50/freshwater HC50 was typically 3.0 for narcotic chemicals (2.8 for nonpolar and 3.4 for polar narcotics), 0.8 for reactive chemicals, 2.9 for neurotoxic chemicals (4.3 for AChE agents and 0.1 for the cyclodiene type), and 2.5 for herbicides–fungicides. However, the statistical uncertainty associated with this ratio was large (typically 2.3 orders of magnitude). For 81% of the organic chemicals studied, there was no statistical difference between the hazardous concentration of aquatic and terrestrial species. We conclude that possible systematic deviations between the HC50s of aquatic and terrestrial species appear to be less prominent than the overall statistical uncertainty.