Soil testing to predict phosphorus leaching

Subsurface pathways can play an important role in agricultural phosphorus (P) losses that can decrease surface water quality. This study evaluated agronomic and environmental soil tests for predicting P losses in water leaching from undisturbed soils. Intact soil columns were collected for five soil types that a wide range in soil test P. The columns were leached with deionized water, the leachate analyzed for dissolved reactive phosphorus (DRP), and the soils analyzed for water-soluble phosphorus (WSP), 0.01 M CaCl2 P (CaCl2-P), iron-strip phosphorus (FeO-P), and Mehlich-1 and Mehlich-3 extractable P, Al, and Fe. The Mehlich-3 P saturation ratio (M3-PSR) was calculated as the molar ratio of Mehlich-3 extractable P/[Al + Fe]. Leachate DRP was frequently above concentrations associated with eutrophication. For the relationship between DRP in leachate and all of the soil tests used, a change point was determined, below which leachate DRP increased slowly per unit increase in soil test P, and above which leachate DRP increased rapidly. Environmental soil tests (WSP, CaCl2-P, and FeO-P) were slightly better at predicting leachate DRP than agronomic soil tests (Mehlich-1 P, Mehlich-3 P, and the M3-PSR), although the M3-PSR was as good as the environmental soil tests if two outliers were omitted. Our results support the development of Mehlich-3 P and M3-PSR categories for profitable agriculture and environmental protection; however, to most accurately characterize the risk of P loss from soil to water by leaching, soil P testing must be fully integrated with other site properties and P management practices.     

Coupled abiotic-biotic mineralization of 2,4,6-trinitrotoluene (TNT)

Munitions wastes such as TNT are widespread contaminants in soils and ground waters. We investigated a coupled abiotic-biotic treatment scheme for remediation of aqueous solutions of TNT. Mineralization of aqueous TNT (0.22 mM) was initially optimized with minimum reactant use (Fe3+ and H2O2) in light-assisted and dark, modified Fenton reactions at acidic and neutral pH. Complete TNT degradation occurred under all reaction conditions within 24 h. Using the optimum reactant concentrations, coupled abiotic-biotic reactions showed an increase in TNT mineralization, from 47 to 80%, after biomass addition to the acidic, dark Fenton-like reaction. Comparable increases of TNT mineralization were observed under neutral pH with similar reaction conditions. In light-assisted Fenton-like reactions at neutral pH, no increase in cumulative TNT mineralization (66%) was seen in coupled abiotic-biotic reactions. Abiotic photo-Fenton-like reactions alone, at acidic pH, produced complete TNT mineralization and required no biotic assistance. While light-enhanced Fenton reactions alone can provide high levels of TNT mineralization, the dark abiotic-biotic reaction scheme has perhaps a wider use due to a similar extent of TNT mineralization in the absence of light, leading to possible applications in soil slurry and in situ processes in the subsurface.     

The true distribution and accumulation of radiocaesium in stem of Scots pine (Pinus sylvestris L.)

The radial and vertical distributions of radiocaesium, potassium and calcium were determined in two Scots pine stands (17 and 58 yr old) similarly affected by the Chernobyl fallout. For both age classes, concentrations are always the lowest in the stemwood, highest in the inner bark and intermediary levels were observed for the outer bark. Due to the cumulative character of its biomass. however. stemwood is a long-term major reservoir of 137Cs. With tree development, changes in the 137Cs radial distribution are well described by variations in the sap ascent pattern and reveal an important transfer between tree rings. It is shown that. both the biomass evolution and knowledge of the evolution of the 137Cs radial gradient are important to predicting 137Cs accumulation in wood with time. According to the common transfer factor (TF) approach, one would expect a decrease in radiocaesium accumulation with time (from 0.0047 +/- 0.0013 to 0.0035 +/- 0.0008 m2kg(-1) for the 17 and 58 yr old trees, respectively). With the wood immobilisation potential (WIP) approach, it was, however, clearly shown that additional annual uptake was highest for the older stand (3.12 +/- 0.23 Bq cm(-3) yr(-1) for the 58-year-old stand compared to 1.99 +/- 0.30 Bq cm(-3) yr(-1) for the younger stand). Following the WIP approach, it was moreover possible to distinguish between the 137Cs incorporated via the root uptake process and a possible lasting effect of interception. It is shown that, whereas for the younger stand (5 yr old at the time of the accident) root uptake contributed exclusively to the wood contamination, the former process explained only 48% of the measured total 137Cs content in the wood of the older tree.     

PM2.5 assessment in 21 European study centers of ECRHS II: Method and first winter results

The follow-up of a cohort of adults from 29 European centers of the former European Community Respiratory Health Survey (ECRHS) I (1989-1992) will examine the long-term effects of exposure to ambient air pollution on the incidence, course, and prognosis of respiratory diseases, in particular asthma and decline in lung function. The purpose of this article is to describe the methodology and the European-wide quality control program for the collection of particles with 50% cut-off size of 2.5 microm aerodynamic diameter (PM2.5) in the ECRHS II and to present the PM2.5 results from the winter period 2000-2001. Because PM2.5 is not routinely monitored in Europe, we measured PM2.5 mass concentrations in 21 participating centers to estimate background exposure in these cities. A standardized protocol was developed using identical equipment in each center (U.S. Environmental Protection Agency Well Impactor Ninety-Six [WINS] and PQ167 from BGI, Inc.). Filters were weighed in a single central laboratory. Sampling was conducted for 7 days per month for a year. Winter mean PM2.5 mass concentrations (November 2000-February 2001) varied substantially, with Iceland reporting the lowest value (5 microg/m3) and northern Italy the highest (69 microg/m3). A standardized procedure appropriate for PM2.5 exposure assessment in a multicenter study was developed. We expect ECRHS II to have sufficient variation in exposure to assess long-term effects of air pollution in this cohort. Any bias caused by variation in the characteristics of the chosen monitoring location (e.g., proximity to traffic sources) will be addressed in later analyses. Given the homogenous spatial distribution of PM2.5, however, concentrations measured near traffic are not expected to differ substantially from those measured at urban background sites.     

Assessing chronic toxicity of bisphenol A to larvae of the African clawed frog (Xenopus laevis) in a flow-through exposure system

A number of currently used industrial chemicals are estrogenic, and therefore have potential to disrupt sexual differentiation in vertebrate wildlife during critical developmental windows. We assessed the effect of larval exposure to bisphenol A (BPA) on growth, development and sexual differentiation of the gonad in the African Clawed frog, Xenopus laevis. Larvae were maintained in flow-through conditions at 22 +/- 1 degrees C and exposed to BPA at mean measured concentrations of 0.83, 2.1, 9.5, 23.8, 100, and 497 microg/l, from developmental stages 43/45-66 (completion of metamorphosis). Each test concentration, plus dilution water control (DWC) and positive control (17beta-estradiol (E2), 2.7 microg/l) employed four replicate test vessels with 40 larvae per tank. Individual froglets were removed from test vessels upon reaching stage 66, and the study was terminated at 90 days. Froglets were dissected and sex was determined by inspection of gross gonadal morphology. Test concentrations of BPA had no effect on survival, growth, developmental stage distributions at exposure days 32 and 62, or mean time to completion of metamorphosis, compared to DWC. Analysis of post-metamorphic sex ratio, determined by gross gonadal morphology, indicated no significant deviations from expected (50:50) sex ratio, in DWC or any BPA test concentration. In contrast, exposure of larvae to (E2) resulted in feminisation, with sex ratio deviating significantly (31% male, replicates pooled). Exposure to BPA in the concentration range 0.83-497 microg/l in flow-through conditions had no observable effect on larval growth, development or sexual differentiation (as determined by gross gonadal morphology) in this study.     

Soot sorption of non-ortho and ortho substituted PCBs

Field-observations of distribution coefficients well above expectations from bulk organic-matter partitioning for several chlorinated aromatic compound classes have lead to the hypothesis that enhanced affinity to soot may not be limited to polycyclic aromatic hydrocarbons but may extend as a significant process for a wider range of hydrophobic organic compounds. This suggestion was here tested in soot-column sorption experiments with a series of ortho- and non-ortho substituted polychlorinated biphenyls (PCBs), using diesel particulate matter (NIST standard reference material SRM-1650) as model soot sorbent. For congeners of similar hydrophobicity, considerably higher affinities toward the soot sorbent were observed for the non-ortho substituted PCBs. Mono- to tetra-ortho substituted PCBs exhibited log-based soot-water distribution coefficients (K(sc)) from 5.25 to 5.51 l/kg(sc) at solute concentrations corresponding to 1-13 microg/l. In contrast, biphenyl, mono- and dichloro- non-ortho substituted PCBs yielded logK(sc) values between 5.09 and 6.35 l/kg(sc). These results are 20-50, and 75-110 times higher, respectively, than the corresponding K(ow)-predicted K(oc) numbers. This strong interaction with soot, particularly of non-ortho substituted PCBs, may fundamentally affect their environmental distribution and bioavailable exposure.     

Flooding patterns of the Okavango Wetland in Botswana between 1972 and 2000

The inundated area of the Okavango Delta changes annually and interannually. The variability relates to regional precipitation over the catchment area in the Angolan highlands, and to local rainfall. The patterns of the wetland were captured using more than 3000 satellite images for the period 1972 to 2000, near daily NOAA AVHRR data for 1985-2000, and less frequent images of the Landsat sensors from 1972 onwards. One AVHRR image for every 10-day period was classified into land and water using an unsupervised classification method. Evaluation against Landsat TM and ERS2-ATSR data indicate an agreement of 89% for the size of estimated inundation area. Results show that the wetland area has varied between approximately 2450 km2 and 11400 km2 during the last 30 years.     

An Investigation of Environmental Racism Claims: Testing Environmental Management Approaches with a Geographic Information System

The purpose of this research was to explore the concept of an environmental racism claim through the use of several environmental management tools. The EPAs Toxics Release Inventory, Cumulative Exposure Project, and the Los Angeles County Department of Health Services' Hot Zone Census Tract Assessment were combined with racial and socioeconomic data to test claims that minorities in South Central Los Angeles are disproportionately exposed to environmental lead. Multivariate analysis indicated that race is strongly associated with the number of cases of elevated blood lead levels in South Central, irrespective of poverty status. Proximity to point sources, a common focal point for studies of environmental racism, was not a contributing factor to health outcomes. Proximity to transportation corridors was consistently the strongest indicator of environmental lead exposure, while median home values were significantly and positively related to elevated blood lead levels. Implications for environmental justice advocates and social and environmental scientists are discussed.     

Aerial measurements on uranium ore mining, milling and processing areas in Germany

The paper describes aerial measurements at several sites containing residues from uranium mines, waste rock dumps and tailings ponds of the Wismut company in Saxony and Thuringia. For the measurements, a computerized gamma-ray spectrometer equipped with a HPGe-detector and a NaI(Tl)-detector array with a volume of 121 was used. Radioactive anomalies from natural radionuclides have been detected and mapped. The activity concentrations of 226Ra, 228Th and 40K in areas with elevated radioactivity from natural radionuclides were determined from aerial measurements. Ground-based measurements--as far as available--confirmed these results. The mean 226Ra activity concentrations in the different waste rock dumps were found to be in the range 370 to 1600 Bq kg-1. The highest mean 226Ra activity concentrations were measured for the tailings ponds with values up to 1300 Bq kg-1. For 40K and 208Tl, activity concentrations of 860 and 40 Bq kg-1, respectively, were obtained as averages of all measurements. These values are commonly found in the environment. In general, there is reasonable agreement between the results measured with different detectors and measuring methods.     

New advancements for in situ treatment using electrical resistance heating

Electrical resistance heating (ERH) is proving to be an effective technology to rapidly heat the subsurface and, in doing so, removing volatile organic compounds. Practitioners of this technology have observed that other processes (biodegradation, abiotic degradation, hydrolysis, and possibly others) occur to break down the chemicals of concern, and remediation is not solely accomplished through vaporization. Few sites treated using ERH have been monitored during and after treatment to identify and evaluate the processes occurring and assess the contribution of these other biological and chemical processes in the remediation effort so that they may be incorporated in the remediation design. At Fort Lewis, Washington, a landfill has been undergoing ERH treatment in three phases, where chlorinated volatile organic compounds represent the primary chemicals of concern in soil and groundwater. Other chemicals of concern include petroleum products, oils, and lubricants. The Fort Lewis remediation projects provided an opportunity to observe the reactions occurring in the subsurface during ERH and fine‐tune the study with each phase of operation. This study is still under way. However, the data gathered to date, which focuses on biodegradation, provides insights into the processes that have been observed. For the Fort Lewis site, biotic and abiotic degradation processes have been observed throughout the range of operating temperatures. At the lower temperature ranges (up to 70°C), biological processes appear to predominate. Above 70°C, abiotic processes become much more active. The goal of this work is to eventually optimize the use of these intrinsic processes in ERH remediation to reduce energy requirements and costs. © 2007 Wiley Periodicals, Inc.