A Methodological Approach for Exposure Assessment Studies in Residences Using Volatile Organic-Compound-Contaminated Water

Abstract

This paper presents a methodological approach for assessing total exposures to volatile organic compounds (VOCs) in residences using contaminated water supplies. This approach is founded on assessment of ingestion, inhalation, and dermal exposures; both long-term (i.e., 12 to 24 hr) lowlevel exposures and short-term (i.e., =10 min) high-level exposures are considered.

The methodology is based on the collection of water samples to establish the identity of the contaminants, maximum source terms, and possible dermal and ingestion exposures; integrated whole-air samples are collected to assess long- and short-term inhalation exposures; whole-air grab samples are used to confirm peak and typical inhalation exposures; and alveolar breath samples are used to confirm exposures and to estimate contaminant concentrations in the blood of the test subjects. While we do not suggest that this methodology should supersede any current investigative approach, this material is primarily offered as a consolidated reference to the many people or organizations who might contemplate a study of this type. Application of this investigative protocol should provide detailed exposure assessment information, while it supplies critical real world data for risk assessment specialists, toxicologists, and modeling experts. Data from a recent field study assessing exposures to trichloroethylene are presented to illustrate the utility and some of the limitations of this strategy.     

Reducing phosphorus flux from organic soils in surface flow treatment wetlands

Treatment wetlands have a finite period of effective nutrient removal after which treatment efficiency declines. This is due to the accumulation of organic matter which decreases the capacity and hydraulic retention time of the wetland. We investigated four potential solutions to improve the soluble reactive P (SRP) removal of a municipal wastewater treatment wetland soil including; dry down, surface additions of alum or calcium carbonate and physical removal of the accreted organic soil under both aerobic and anaerobic water column conditions. The flux of SRP from the soil to the water column under aerobic conditions was higher for the continuously flooded controls (1.1 ± 0.4 mg P m⁻² d⁻¹), dry down (1.5 ± 0.9 mg P m⁻² d⁻¹) and CaCO₃ (0.8 ± 0.7 mg P m⁻² d⁻¹) treatments while the soil removal and alum treatments were significantly lower at 0.02 ± 0.10 and −0.07 ± 0.02 mg P m⁻² d⁻¹, respectively. These results demonstrate that the two most effective management strategies at sequestering SRP were organic soil removal and alum additions. There are difficulties and costs associated with removal and disposal of soils from a treatment wetland. Therefore our findings suggest that alum addition may be the most cost effective and efficient means of increasing the sequestering of P in aging treatment wetlands experiencing reduced P removal rates. However, more research is needed to determine the longer term effects of alum buildup in the organic soil on the wetland biota, in particular, on the macrophytes and invertebrates. Since alum effectiveness is time limited, a longer term solution to P flux may favor the organic soil removal.     

Hematology and Some Biochemical Parameters of Wild Rodents in Pistachio Gardens of Kerman Province, Southeast Iran

Wild rodents were collected using live snap traps in pistachio gardens of Kerman Province, Southeast Iran from 2007 to 2009, then some physiological parameters of them were measured. The samples were identified as follow: Nesokia indica, Meriones persicus, Meriones lybicus and Tatera indica. Blood samples were obtained from the heart, then the blood parameters (glucose, cholesterol, triglyceride, total protein, HDL, red and white blood cell number) in wild species of rodents and laboratory rat were compared. The results showed that there were no significant differences in serum glucose, triglyceride, HDL and total protein levels among different experimental groups. The concentration of cholesterol in T. indica was more than that in N. indica (P < 0.01). The total numbers of red blood cells also showed significant difference between wild garden rodent species and laboratory rat (P < 0.01), while the numbers of white blood cells showed no significant difference.     

CASE STUDIES OF AGRICULTURAL WATER CONSERVATION1

Farmers from four irrigation districts in Texas and California were questioned about water conservation practices they are now using, those they plan to adopt, and potential incentives that government might offer to induce still further water conservation on their part. While responses differed somewhat from place to place and among individual farmers, the general results were: a) farmers reported that “water conservation” is not new to them, it is something they practice regularly; b) recent innovations such as laser controlled land leveling devices have permitted some substantial water use reductions in recent years; and c) even greater incentive mechanisms that government could provide and that farmers would accept as useful incentives, such as long term low interest loans for water saving equipment, would probably not be able to reduce water use in agriculture much further than 15 percent below current levels. It is recommended nonetheless that Federal agencies and local water districts and individuals should nonetheless pursue water conservation training and education programs, demonstrations of conjunctive use and water banking opportunities for water saving, and increased loan programs for installation of water saving equipment.     

四川省部分豆科植物根瘤菌的遗传多样性

从四川省豆科植物鸡眼草属、合欢属、豇豆属、葛属、金合欢、杭子梢分离获得了103株根瘤菌,采用AFLP、BOXAIR-PCR研究了这些菌株的遗传多样性.结果表明,分离自四川省豆科植物6个属的根瘤菌存在明显的遗传多样性,AFLP分析中,全部供试菌株的相似性为21%,全部供试菌株可分为26个AFLP遗传群;BOXAIR-PCR聚类分析结果表明,103个菌株分在70%相似性水平处,供试菌株被分为18个BOX遗传群.除部分菌株外,多数根瘤菌按宿主类型聚群,同一宿主而地理来源不同的根瘤菌分布于不同的遗传群,表明宿主和地理环境对根瘤菌具有深刻影响.图3表1参9     

Simultaneous transport of parent and daughter compounds in aquifers with linear first-order sorption kinetics

In soils, daughter compounds may be generated from a parent compound by microbial metabolism, chemical reactions, radioactive decay, or other mechanisms. These daughter compounds are also acted upon by soil physical, chemical and biological processes. A system often referred to as a cascade or chain of compounds system results. While a great deal of attention has been given to this problem with the linear equilibrium assumption applied uniformly to all transport and reacting compounds, little attention has been given to the simultaneous transport and fate of a parent-daughter chain with a first-order rate assumed for the adsorption-desorption kinetics of each compound and with the soil partitioned into three sorption classes.A general one-dimensional cascade or chain model for the simultaneous transport of parent and daughter compounds in sorbing, homogeneous, water table aquifers is presented. The model is based on an advective-dispersive mass accounting formulation for both compounds and includes: (a) first-order rate of conversion of parent to daughter; (2) first-order rates of loss of either parent or daughter or both due to metabolism, chemical reaction and/or irreversible processes; (3) partitioning of the aquifer material into three sorption classes, namely mildly sorbing, strongly sorbing and organic matter; (4) linear first-order kinetic rules for adsorption and desorption operating on each of the sorbing soil fractions for each compound; (5) constantly emitting sources of rectangular shape of parent compound; and (6) mass accounting boundary conditions; and a tailorable initial distribution on [0, ∞). Mathematical analysis yields a coupled, linear system of equations including two transport and fate equations, initial and boundary data, and six kinetic rules, namely three each for parent and daughter compound. A numerical scheme for solving the system of equations was developed using readily available procedures since analytical solutions could not be found. Solutions for scenarios based on leaking underground sources are presented.     

Pilot scale application of a method for the analysis of perfluorinated compounds in surface soils

A growing number of studies now indicate that perfluorinated compounds (PFCs) are globally distributed in the environment. Their widespread distribution and presence in remote locations has led to questions about the importance of atmospheric and oceanic transport. Describing their distribution in surface soils is also an essential but neglected element in developing a comprehensive understanding of their occurrence in the environment. Soils are the critical link between global atmospheric and hydrologic processes where both local and distant contaminants can accumulate and be released into aquatic and terrestrial communities. Because PFC concentrations in soils will influence ground and surface water, wildlife, and crops, methods to accurately measure PFCs in soil are clearly needed. To help answer this need, we developed a method for the analysis of nine perfluorinated carboxylic acids and four perfluorinated sulfonic acids in soil. Samples from six nations (n = 10 per nation) were analyzed by LC-MS/MS to demonstrate the method performance parameters and to make preliminary observations about the occurrence of the PFCs in soils in different parts of the world. The resulting method shows acceptable performance characteristics for the target compounds in most soils while documenting the widespread occurrence of PFCs in surface soils.     

Herbicide sorption coefficients in relation to soil properties and terrain attributes on a cultivated prairie

The sorption of 2,4-D and glyphosate herbicides in soil was quantified for 287 surface soils (0-15 cm) collected in a 10 x 10 m grid across a heavily eroded, undulating, calcareous prairie landscape. Other variables that were determined included soil carbonate content, soil pH, soil organic carbon content (SOC), soil texture, soil loss or gain by tillage and water erosion, and selected terrain attributes and landform segments. The 2,4-D sorption coefficient (Kd) was significantly associated with soil carbonate content (-0.66; P < 0.001), soil pH (-0.63; P < 0.001), and SOC (0.47; P < 0.001). Upper slopes were strongly eroded and thus had a significantly greater soil carbonate content and less SOC compared with lower slopes that were in soil accumulation zones. The 2,4-D Kd was almost twice as small in upper slopes than in lower slopes. The 2,4-D Kd was also significantly associated with nine terrain attributes, particularly with compounded topographic index (0.59; P < 0.001), gradient (-0.48; P < 0.001), mean curvature (-0.43; P < 0.001), and plan curvature (-0.42 P < 0.001). Regression equations were generated to estimate herbicide sorption in soils. The predicted power of these equations increased for 2,4-D when selected terrain attributes were combined with soil properties. In contrast, the variation of glyphosate sorption across the field was much less dependent on our measured soil properties and calculated terrain attributes. We conclude that the integration of terrain attributes or landform segments in pesticide fate modeling is more advantageous for herbicides such as 2,4-D, whose sorption to soil is weak and influenced by subtle changes in soil properties, than for herbicides such as glyphosate that are strongly bound to soil regardless of soil properties.     

The Roles of Photooxidation and Biodegradation in Long-term Weathering of Crude and Heavy Fuel Oils

Although spilled oil is subject to a range of natural processes, only combustion, photooxidation and biodegradation destroy hydrocarbons and remove them from the biosphere. We present laboratory data that demonstrate the molecular preferences of these processes, and then examine some oil residues collected from previously documented releases to confirm the important roles that these processes play in removing spilled oil from both marine and terrestrial environments.     

Analysis of anaerobic BTX biodegradation in a subarctic aquifer using isotopes and benzylsuccinates

In situ biodegradation of benzene, toluene, and xylenes in a petroleum hydrocarbon contaminated aquifer near Fairbanks, Alaska was assessed using carbon and hydrogen compound specific isotope analysis (CSIA) of benzene and toluene and analysis of signature metabolites for toluene (benzylsuccinate) and xylenes (methylbenzylsuccinates). Carbon and hydrogen isotope ratios of benzene were between -25.9 per thousand and -26.8 per thousand for delta13C and -119 per thousand and -136 per thousand for delta2H, suggesting that biodegradation of benzene is unlikely at this site. However, biodegradation of both xylenes and toluene were documented in this subarctic aquifer. Biodegradation of xylenes was indicated by the presence of methylbenzylsuccinates with concentrations of 17-50 microg/L in three wells. Anaerobic toluene biodegradation was also indicated by benzylsuccinate concentrations of 10-49 microg/L in the three wells with the highest toluene concentrations (1500-5000 microg/L toluene). Since benzylsuccinate typically accounts for a very small fraction of the toluene present in groundwater (generally <1 mol%), the signature metabolite approach works best at higher toluene concentrations when it is not constrained by detection limits. In wells with lower toluene concentrations (410-640 microg/L), carbon and hydrogen isotopic values were enriched by up to approximately 2 per thousand for delta13C and approximately 70 per thousand for delta2H. This evidence of isotopic fractionation verifies the effects of biodegradation in these low concentration wells where metabolites may already be below detection limits. The combined use of signature metabolite and CSIA data is particularly valuable given the challenge of verifying biodegradation in subarctic environments where degradation rates are typically much slower than in temperate environments.