Passive sampling: partition coefficients for a silicone rubber reference phase

Silicone rubber sheeting can be used as a passive sampling device for hydrophobic organic contaminants in the environment to determine the available concentrations in water and sediments. Reliable sampler-water partition coefficients are required to determine the sampling rates and the dissolved contaminant concentrations in water and in sediment pore water. Log partition coefficients (logK(sr,w)) for silicone rubber-water have been estimated for 32 polycyclic aromatic hydrocarbons (PAHs), 2 deuterated PAH analogues and 32 chlorobiphenyls (CBs) using the cosolvent method, with methanol as cosolvent. Strong linear relationships were found with literature values for the corresponding log octanol-water partition coefficients (logK(ow)) for both CBs and PAHs, confirming that partitioning into the silicone rubber is strongly determined by the hydrophobicity of the compounds, which suggests logK(ow) is a good predictor of logK(sr,w) and that absorption is the main mechanism for accumulation of analytes into the silicone rubber polymer.     

Assessment of natural radiation exposure levels and mass attenuation coefficients of lime and gypsum samples used in Turkey

The activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K in lime and gypsum samples used as building materials in Turkey were measured using gamma spectrometry. The mean activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K were found to be 38 ± 16, 20 ± 9, and 156 ± 54 Bq kg^???1 for lime and found to be 17 ± 6, 13 ± 5, and 429 ± 24 Bq kg^???1 for gypsum, respectively. The radiological hazards due to the natural radioactivity in the samples were inferred from calculations of radium equivalent activities (Ra_eq), indoor absorbed dose rate in the air, the annual effective dose, and gamma and alpha indices. These radiological parameters were evaluated and compared with the internationally recommended limits. The experimental mass attenuation coefficients (μ/ρ) of the samples were determined in the energy range 81–1,332 keV. The experimental mass attenuation coefficients were compared with theoretical values obtained using XCOM. It is found that the calculated values and the experimental results are in good agreement.     

Distribution and partition of polycyclic aromatic hydrocarbon in surface water of the Pearl River Estuary, South China

Water samples were collected in the Pearl River Estuary in July 2002 and April 2003. The particulate and dissolved phase polycyclic aromatic hydrocarbons (PAHs) were determined. Total PAH concentrations in water samples were higher in April of 2003 (C (p): 4.0-39.1 ng/L or 445.1-1,089.9 ng/g; C (w): 15.9-184.2 ng/L) than in July of 2002 (C (p): 2.6-26.6 ng/L or 297.7-1,336.6 ng/g; C (w): 12.9-28.3 ng/L). It was found that 5, 6-ring PAHs enrich in the inner estuary samples and so did 3-ring PAHs in the July samples. Compositional differences in the suspended particulate matter (SPM) might be responsible for this observation. The partition coefficient (K (p)) increased with the increasing of the particular organic carbon content of suspended particles as well as the salinity of water, decreased with the increase of the total suspended particles content of samples. A linear correlation between logK (OC) and logK (OW) was found in two sampling periods. The observed values of logK (OC) exceed their predicted values derived form linear free energy relationship between logK (oc) and logK (ow), which could be attributed to the nonlinear sorption of soot-like carbons in suspended particles.     

Remobilization of polychlorinated biphenyls from sediment and its consequences for their transport in river waters

A laboratory experiment was performed to examine the remobilization of indicator polychlorinated biphenyls (iPCBs) from sediments and its results were applied to the real-world data for explaining the transport of PCBs in river. Seven PCB concentrations were determined in three series of model water–sediment systems (3 g of river sediment, three different volumes of distilled water (0.5, 0.25, and 0.15 ml), and 5 mg of biocide) after 11 days of incubation. Solid-phase extraction was used for separation of analytes from the aqueous phase and solvent extraction for isolation of analytes from the sediments, respectively. The extracts were analyzed for individual iPCB congeners using gas chromatography–mass spectrometry method. For each series of the experiment, the concentrations of PCBs in aqueous phase were similar. The average sediment/water partition coefficient value was 10⁴?l/kg. The solubility of individual PCB congeners in water did not influence the desorption of PCBs from the sediment. Although the dominant form of PCBs in a water–sediment system occurs as suspended and colloidal fractions, these compounds are transported mostly in a dissolved form. Suspended and colloidal matter is a major sink for PCBs in low-energy aquatic environments. In contrast, the dissolved PCBs are readily transported in running waters. The mobilization of PCBs from sediments to aqueous phase, with respect to their solubility in water, seems to be limited, thus reducing the risk of secondary pollution.     

Correlated Parameters Uncertainty Propagation in a Rainfall-Runoff Model,Considering 2-Copula; Case Study: Karoon III River Basin

Hydrological models are widely used to investigate practical issues of water resources. Parametric uncertainty is considered as one of the most important sources of uncertainty in environmental researches. Generally, it is assumed that the parameters are independent mutually, but correlation within the parameter space is an important factor having the potential to cause uncertainty. The objective and innovation of this study was to address the effects of parameters correlation on a continuous hydrological model uncertainty. HEC-HMS with soil moisture accounting (SMA) infiltration method was used to model daily flows and simulate certainty bounds for Karoon III basin, southwest of IRAN, in two scenarios, independent and correlated parameters using 2-copula. The parameters were represented by probability distributions, and the effect on prediction error were evaluated using Latin hypercube sampling (LHS) on Monte Carlo simulation (MCS). Saturated hydraulic conductivity (K), Clark storage-coefficient (R), and time of concentration (tc) were chosen for investigation, based on observed sensitivity analysis of simulated peak over threshold (POT). One hundred runs were randomly generated from 100 parameter sets captured from LHS of parameters distributions in each sub-basin. Using generated parameter sets, 100 continuous hydrographs were simulated and values of certainty bounds calculated. Results showed that when 2-copula correlated R and tc, with 0.656 Kendall’s Tau and 0.818 Spearman’s Rho coefficients, were propagated, decreasing of outputs’ sharpness was more than when considering K and R (K-R), with 0.166 and 0.262; therefore, incorporation of correlations in the MCS is important, especially when the correlation coefficients exceed 0.65. The model was evaluated at the outlet of the basin using daily stream flow data. Model reliability was better for above-normal flows than normal and below-normal. Reliability increases of simulated flow when considering correlated R-tc was more than K-R because of the correlation values. Incorporation of copula for K-tc not only did not improve the model reliability but also decreased it. Results showed improvement of model reliability, by decreasing predicted error of hydrologic modeling, when dealing with correlated parameters in the system.     

Correlation of Black Smoke and Nitrogen Oxides Emissions Through Field Testing of in-Use Diesel Vehicles

The U.S. Environmental Protection Agency Environmental Monitoring and Assessment Program (EMAP) uses water clarity as a water quality indicator for integrated assessments of coastal waters. After the publication of the first National Coastal Condition Report (USEPA, 2001c), the national water clarity reference value of 10% of ambient surface light at 1~m depth was reevaluated and modified to reflect expected differences in regional reference light conditions. These regional differences range from naturally turbid estuaries like those found in Mississippi and Louisiana to clear water estuaries expected to support extensive beds of submerged aquatic vegetation in, e.g., Florida and Tampa Bays. For the second National Coastal Condition Report, water clarity was assessed based on regional reference values (USEPA, 2004). Different regional water clarity reference values and data collection methods necessitated the development of a water clarity index based on light attenuation coefficients (k). This index incorporates regional reference conditions and is interchangeable with secchi depth and percent light transmission calculated from light meter measurements. Evaluation of the water clarity index shows that k values based on transmissivity at 1~m can be estimated from secchi depth measurements and successfully used as a surrogate for transmissivity calculated from light meter data. An approach for assessing water clarity in Gulf of Mexico estuaries using light meter data and secchi depth is presented.     

气相色谱/质谱法测定水中15种酞酸酯类化合物

采用固相萃取-气相色谱/质谱法测定水中15种酞酸酯类化合物,确定方法的最优条件为:依次用10 m L正己烷和丙酮混合溶剂(V/V=5∶1)、甲醇和空白试剂水活化C18固相萃取柱后,水样以5 m L/min过柱萃取,再以8 m L正己烷:丙酮(V/V=5∶1)混合溶剂洗脱后,浓缩至1 m L,进气相色谱/质谱测定。该法的检出限为0.18~0.38μg/L,在0.50~20.0 mg/L范围内线性良好,相关系数均0.996。空白水样的加标回收率为71.8%~120%,相对标准偏差为1.73%~12.7%;实际废水水样的加标回收率为64.8%~135%,相对标准偏差为2.75%~18.0%。     

Effects of salinity and organic matter on the partitioning of perfluoroalkyl acid (PFAs) to clay particles

The influence of salinity and organic matter on the distribution coefficient (K(d)) for perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) in a brackish water-clay system was studied. The distribution coefficients (K(d)) for PFAs onto inorganic clay surfaces increased with salinity, providing evidence for electrostatic interaction for the sorption of PFAs, whereas the relationship between K(d) and organic carbon content (f(oc)) suggested that hydrophobic interaction is the primary driving force for the sorption of PFAs onto organic matter. The organic carbon normalized adsorption coefficient (K(oc)) of PFAs can be slightly overestimated due to the electrostatic interaction within uncoated inorganic surfaces. In addition, the dissolved organic matter released from coated clay particles seemed to solvate PFA molecules in solution, which contributed to a decrease in K(d). A positive relationship between K(d) and salinity was apparent, but an empirical relationship for the 'salting-out' effect was not evident. The K(d) values of PFAs are relatively small compared with those reported for persistent organic pollutants. Thus, sorption may not be a significant route of mass transfer of PFAs from water columns in estuarine environments. However, enhancement of sorption of PFAs to particulate matter at high salinity values could evoke potential risks to benthic organisms in estuarine areas.     

Distribution of gamma-ray emitting radionuclides in the marine environment of the Burullus Lake: II. Bottom sediments

The sediment compartment has the ability to trap large amounts of radionuclides and to indicate the radiological impact of pollution. The present work shows the results obtained related to the concentrations of ¹³⁷Cs and natural radionuclides in sediment in the Burullus Lake, Egypt. The average values of ²²⁶Ra, ²³²Th, and ⁴⁰K in the bottom sediments collected from the east of the Burullus Lake ranged from 10.3 to 21.8 Bq/kg, from 11.9 to 34.4 Bq/kg, and from 268 to 401 Bq/kg, respectively. The study has shown that ⁴⁰K concentration is nearly uniform throughout the studied area while ²²⁶Ra and ²³²Th are more concentrated in the northeastern shore. Lake sediments showed contamination with ¹³⁷Cs (2.7–15.9 Bq/kg). The ¹³⁷Cs sediment activities indicated higher concentrations in the off-shore sites. Concentrations of all γ -ray emitting radionuclides except ⁴⁰K in water samples were below the detection limits. The ⁴⁰K sediment–water distribution coefficients of the near-shore samples were higher than the off-shore samples.     

Models for the adsorption of organic compounds at gas-water interfaces

The solvation parameter model is used to characterize interactions responsible for adsorption at the gas-water interface for bulk water at 15 and 25 degrees C, snow at -6.8 degrees C, mineral-supported water films (alumina, calcium carbonate and quartz) at 15 degrees C, and dry soil at 15 degrees C. The mineral-supported water films and dry soil adsorption data are modeled at different relative humidities in the range 40-99%. The models produce satisfactory results with standard errors of the estimate of 0.12 to 0.17 for regression of the model predicted adsorption equilibrium constants against the experimental values (range for equilibrium constants -2 to -7 log units). The water surface is polar with a significant capacity for dipole-type and hydrogen-bonding interactions. In addition, it is strongly electron lone pair repulsive. Dispersion interactions favor adsorption at the water surface. Mineral-supported water films at relative humidities greater than 40% demonstrate adsorption properties similar to bulk water. The adsorption characteristics, however, depend on the relative humidity and the nature of the support. In the case of dry soil the adsorption properties at different relative humidities cannot simply be explained by adsorption of a water film covering the soil surface and the changes in adsorption characteristics with relative humidity are more complex than the mineral-supported water films.     

In vivo laser-induced fluorescence detection of pyrene in nematodes and determination of pyrene binding constants for humic substances by fluorescence quenching and bioconcentration experiments

The bioconcentration of pyrene by bacterivorous thread worms (nematodes) of the species Caenorhabditis elegans was studied with laser-induced fluorescence (LIF) spectroscopy, fluorescence imaging and a radiotracer method. The vibronic band intensities of the LIF spectra indicated that the microenvironment of pyrene in the nematodes was similar to a low-polarity solvent, and thus provided direct evidence that pyrene was accumulated in lipid-rich areas inside the nematodes. The concentration of pyrene in the nematodes was estimated from the monomer/excimer fluorescence intensity ratio. Results from this method were in fair agreement with results using 14C labeled pyrene for measuring pyrene bioconcentration. Preliminary results indicated that LIF measurements of pyrene may be possible even in single nematodes. Fluorescence microscopic observations revealed that pyrene was not adsorbed on the outside of the organisms, but was strongly concentrated in restricted areas inside the worms. In the second part of the study, the effects of six different humic substances (HS) on the bioconcentration of pyrene were investigated and sorption coefficients (KDOC) calculated from reductions in bioconcentration (KDOC(biol)) were compared with sorption coefficients measured with a fluorescence quenching technique (KDOC(flu)). The results of these two different experimental methods agreed well (with KDOC(biol) being slightly lower than KDOC(flu), indicating that the fraction of pyrene that was determined as freely dissolved by the fluorescence quenching method was comparable to the bioavailable fraction.     

Calibration and verification of a dissolved oxygen management model for a highly polluted river with extreme flow variations in Pakistan

A dissolved oxygen (DO) model is calibrated and verified for a highly polluted River Ravi with large flow variations. The model calibration is done under medium flow conditions (431.5 m³/s), whereas the model verification is done using the data collected during low flow conditions (52.6 m³/s). Biokinetic rate coefficients for carbonaceous biochemical oxygen demand (CBOD) and nitrogenous biochemical oxygen demand (NBOD) (i.e, K _cr and K _n ) are determined through the measured CBOD and ammonia river profiles. The calculated values of K _cr and K _n are 0.36 day^?1 and 0.34 day^?1, respectively. The close agreement between the DO model results and the field values shows that the verified model can be used to develop DO management strategies for the River Ravi. The biokinetic coefficients are known to vary with degree of treatment (DOT) and therefore need to be adjusted for a rational water quality management model. The effect of this variation on level of treatment has been evaluated by using the verified model to attain a DO standard of 4 mg/L in the river using the biokinetic rate coefficients as determined during the model calibration and verification process. The required DOT in this case is found to be 96 %, whereas the DOT is 86 % if adjusted biokinetic rate coefficients are used to reflect the effect of wastewater treatment. The cost of wastewater treatment is known to increase exponentially as the removal efficiency increases; therefore, the use of appropriate biokinetic coefficients to manage the water quality in rivers is important.     

应用小鼠淋巴细胞彗星试验检测地下水遗传毒性

应用小鼠淋巴细胞彗星试验对长治市5个点位地下水水质作遗传毒性研究。结果表明,各水样有机浓集物均可对小鼠淋巴细胞DNA产生不同程度的遗传损伤,随着剂量的增加,Olive尾矩与阴性对照组(0.72±0.09)相比均有显著性差异(P0.05,P0.01)。在试验浓度范围内,以彗星尾部DNA含量、彗星尾长、尾矩和Olive尾矩所指示的DNA损伤程度随剂量增大而逐渐增加,存在显著的剂量-效应关系,其相关系数0.815。