Correlating the spatial distribution of atmospheric ammonia with δ15n values at an ammonia release site

A field ammonia (NH₃) release experiment and open top chambers containing moorland monoliths continuously fumigated with NH₃ or sprayed with NH₄Cl were used to assess the potential for using δ¹⁵N values in determining the area of influence around a point NH₃ emission source. δ¹⁵N values are being increasingly used as environmental tracers and we tested the hypothesis that the δ¹⁵N signal from an NH₃ emission source is observable in nearby vegetation. Using modified monitoring devices, atmospheric NH₃ concentrations were found to decrease with distance from source, with δ¹⁵N values also reflecting this trend, producing a signal shift with changing concentration. Open top chamber studies of δ¹⁵N values of Calluna vulgaris (L.) Hull indicated a correlation with deposition treatments in current year shoots. Analysis of Calluna shoots from the NH₃ release showed a similar trend of δ¹⁵N enrichment. Significant linear correlations between δ¹⁵N and percent N in plant material were found, both in the controlled conditions of the open top chambers and at the NH₃ release site, illustrating the possible use of this technique in N deposition biomonitoring.     

Linking field experiments to long-term simulation of impacts of nitrogen deposition on heathlands and moorlands

The results from three long-term field manipulation studies of the impacts of increased nitrogen deposition (0–120 kg N ha^?1 yr^?1) on lowland and upland heathlands in the UK were compared, to test if common responses are observed. Consistent increases in Calluna foliar N content and decreases in litter C:N ratios were found across all sites, while increases in N leaching were not observed at any site over the range 0–80 kg ha^?1 yr^?1. However, the response of Calluna biomass did vary between sites, possibly reflecting site differences in nutrient status and management histories. Five versions of a simulation model of heathland responses to N were developed, each reflecting different assumptions about the fate and turnover of soil N. Model outputs supported the deduction from mass balance calculations at two of the field sites that N additions have resulted in an increase in immobilisation; the latter was needed to prevent the model overestimating measured N leaching. However, this version of the model significantly underestimated Calluna biomass. Model versions, which included uptake of organic N by Callunaand re-mobilisation of N from the soil organic store provided some improvement in the fit between modelled and field biomass data, but re-mobilisation also led to an overestimation of N leaching. Quantification of these processes and their response to increased N deposition are therefore critical to interpreting experimental data and predicting the long-term impacts of atmospheric deposition on heathlands and moorlands.     

Detecting the signal of atmospheric N deposition in recent national-scale vegetation change across Britain

Model estimates of NO_y and NH_x deposition across Britain for 1996 (5 km square resolution) were applied as explanatory variables to account for national-scale, fine-grained changes in plant species composition between 1990 and 1998. Plant species data were recorded from up to 27 fixed plots located within a stratified random sample of 596 1 km². The response variable was a cover-weighted Ellenberg fertility score for each plot. Analyses were carried out separately for woodlands, semi-natural grasslands and heaths/bogs. Most of the variation in the botanical response variable occurred between plots within squares and so could not be explained by the model deposition data. NH_x deposition estimates accounted for significant, but small components of between 1 km² variation in the change in Ellenberg score in grasslands (5.6%) and heath/bogs (9.8%) but not woodlands. NO_y deposition estimates were not significantly associated with vegetation change. Linear models provided the best fit and the slope of the relationship was lower for heath/bogs than grasslands. Further signal attribution at sub-kilometre square scales requires the development of fine-grained models of N deposition that can be generalised across regional sampling domains.     

Measuring the success of the federal government's Brownfields Program

In 1995, the U.S. Environmental Protection Agency (US EPA) initiated the Brownfields Program to help local governments clean up and reuse hundreds of thousands of contaminated former factories and transportation and other commercial sites in cities and industrialized suburbs. By the end of 2002, the Brownfields Program had distributed grants of about $200,000 each to 436 local governments. Program grants have diffused through federal, state, regional, and local levels of government and private and not‐for profit organizations, and have reached into economically distressed neighborhoods. As expected, grant recipients disproportionately had a legacy of contaminated industrial sites and relatively large African American and/or Latino populations. But abandoned factories and environmental justice concerns do not completely explain the geographical distribution of recipients. Award winners tended to be larger cities with more capacity to compete for grants and were likely to be connected to sources of information about the grant opportunity and to decision makers. With a few exceptions, recipients consider the program to be highly successful at stimulating entrepreneurs to remediate and redevelop sites and, sometimes, surrounding neighborhoods. © 2005 Wiley Periodicals, Inc.     

End‐state land uses,sustainably protective systems,and risk management: A challenge for remediation and multigenerational stewardship

This article discusses creating a sustainably protective engineered and human management system in perpetuity for sites with long‐lived radiological and chemical hazards. This is essential at this time because the federal government is evaluating its property as assets and attempting to reduce its holdings, while seeking to assure that health and ecosystems are not put at risk. To assist those who have a stake in the remediation, management, and stewardship of these and analogous privately owned sites, this article discusses current end‐state planning by reviewing the federal government's accelerated efforts to reduce its footprint and how those efforts relate to sustainability. The article also provides a list of questions organized around six elements of risk management and primary, secondary, and tertiary disease and injury prevention. Throughout the article, the U.S. Department of Energy (DOE) is used as an example of an organization that seeks to reduce its footprint, manage its budget, and be a steward of the sites that it is responsible for. However, the approach and questions are appropriate for land controlled by the Department of Defense (DOD), the General Services Administration (GSA), and other public and private owners of sites with residual contamination. © 2005 Wiley Periodicals, Inc.     

Evaluation of simplifying assumptions on pesticide degradation in soil

There is evidence that degradation of pesticides in simple laboratory systems may differ from that in the field, but it is not clear which of the simplifications inherent in laboratory studies present serious shortcomings. Laboratory experiments evaluated several simplifying assumptions for a clay loam soil and contrasting pesticides. Degradation of cyanazine [2-(4-chloro-6-ethylamino-1,3,5-triazin-2-ylamino)-2-methylpropiononitrile] and bentazone [3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] at fluctuating temperature and moisture was predicted reasonably well based on parameters derived from degradation under constant conditions. There was a tendency for slower degradation of cyanazine and bentazone in soil aggregates of 3 to 5 mm in diameter (DT50 at 15 degrees C and 40% maximum water holding capacity of 25.1 and 58.2 d, where DT50 is the time for 50% decline of the initial pesticide concentration) than in soil sieved to <3 mm (DT50 of 19.1 and 37.6 d), but the differences were not significant for most datasets. Degradation of cyanazine, isoproturon [3-(4-isopropylphenyl)-1,1-dimethylurea], and chlorotoluron [3-(3-chloro-p-tolyl)-1,1-dimethylurea] was measured in soil amended with different amounts of lignin. The effect of lignin on degradation was small despite considerable differences in sorption. The DT50 values of cyanazine, isoproturon, and chlorotoluron were 16.2, 18.6, and 33.0 d, respectively, in soil without lignin and 19.0, 23.4, and 34.6 d, respectively, in soil amended with 2% lignin. Degradation of bentazone and cyanazine in repacked soil columns was similar under static and flow conditions with 50.1 and 47.2% of applied bentazone and 74.7 and 73.6% of applied cyanazine, respectively, degraded within 20 d of application. Thus, the assumptions underpinning laboratory to field extrapolation tested here were considered to hold for our experimental system. Additional work is required before general conclusions can be drawn.     

An alum-based water treatment residual can reduce extractable phosphorus concentrations in three phosphorus-enriched coastal plain soils

The accumulation of excess soil phosphorus (P) in watersheds under intensive animal production has been linked to increases in dissolved P concentrations in rivers and streams draining these watersheds. Reductions in water dissolved P concentrations through very strong P sorption reactions may be obtainable after land application of alum-based drinking water treatment residuals (WTRs). Our objectives were to (i) evaluate the ability of an alum-based WTR to reduce Mehlich-3 phosphorus (M3P) and water-soluble phosphorus (WSP) concentrations in three P-enriched Coastal Plain soils, (ii) estimate WTR application rates necessary to lower soil M3P levels to a target 150 mg kg(-1) soil M3P concentration threshold level, and (iii) determine the effects on soil pH and electrical conductivity (EC). Three soils containing elevated M3P (145-371 mg kg(-1)) and WSP (12.3-23.5 mg kg(-1)) concentrations were laboratory incubated with between 0 and 6% WTR (w w(-1)) for 84 d. Incorporation of WTR into the three soils caused a near linear and significant reduction in soil M3P and WSP concentrations. In two soils, 6% WTR application caused a soil M3P concentration decrease to below the soil P threshold level. An additional incubation on the third soil using higher WTR to soil treatments (10-15%) was required to reduce the mean soil M3P concentration to 178 mg kg(-1). After incubation, most treatments had less than a half pH unit decline and a slight increase in soil EC values suggesting a minimal impact on soil quality properties. The results showed that WTR incorporation into soils with high P concentrations caused larger relative reductions in extractable WSP than M3P concentrations. The larger relative reductions in the extractable WSP fraction suggest that WTR can be more effective at reducing potential runoff P losses than usage as an amendment to lower M3P concentrations.     

Polycyclic aromatic hydrocarbons (PAHs) in soils of the Moscow Region--concentrations, temporal trends, and small-scale distribution

The knowledge of the environmental fate of polycyclic aromatic hydrocarbons (PAHs) is restricted to few climatic regions of the world almost excluding the Taiga. Our objectives were to (i) separate anthropogenic from background contributions to PAH concentrations and (ii) determine temporal trends in PAH concentrations during the last century including the change in distribution of PAHs in interior and exterior portions of aggregates in soils of the Moscow region. Along a southeast-bound transect from Moscow (windward in winter) and at a background location northeast of Moscow (leeward in winter), seven topsoil samples were collected in 1910-1954 and 35 in 1998-2003. We fractionated the soils in interior and exterior portions of aggregates > 10 mm and remaining soil without aggregates. The sum of 21 PAHs (sigma21PAHs) concentrations in recent bulk soil ranged from 59 to 1350 ng g(-1). The concentrations of all PAHs were lower outside than in Moscow. The range of the concentrations of the sigma21PAHs in archived soil samples (159-1280 ng g(-1)) was similar as in recent soils. In most recent and archived samples, naphthalene and phenanthrene, were most abundant. The concentrations of low-molecular-weight PAHs decreased during the last century at most sites; those of high-molecular-weight compounds increased. The sigma21PAHs concentrations were accumulated in the exterior of aggregates (109%) and depleted in the interior (95%) relative to the concentration in bulk soil (defined as 100%), which was similar to that in the soil without aggregates (99%). The differences between aggregate interior and exterior did not change during the last century. The dominance of naphthalene and phenanthrene is typical of remote regions. The urban influence on PAH concentrations in the last century was small.     

Effects of commercial diazinon and imidacloprid on microbial urease activity in soil and sod

Diazinon [O,O-diethyl O-2-isopropyl-6-methyl(pyrimidine-4-yl) phosphorothioate] and imidacloprid [1-(1-[6-chloro-3-pyridinyl]methyl)-N-nitro-2-imidazolidinimine] are applied to lawns for insect control simultaneously with nitrogenous fertilizers such as urea, but their potential effect on urease activity and nitrogen availability in turfgrass management has not been evaluated. Urease activity in enzyme assays, washed cell assays, and soil slurries was examined as a function of insecticide concentration. Intact cores from field sites were used to assess the effect of insecticide application on urease activity in creeping bentgrass (Agrostis palustris Huds.) and bluegrass (Poa pratensis L.) sod. Bacterial urease from Bacillus pasteurii and plant urease from jack bean [Canavalia ensiformis (L.) DC.] were unaffected by the insecticides. Both insecticides inhibited the growth of Proteus vulgaris, a urease-producing bacterium, but only diazinon significantly reduced urease activity in washed cells; neither insecticide inhibited urease activity in sonicated cells. Neither diazinon nor imidacloprid inhibited urease activity in Woolper soil (fine, mixed, mesic Typic Argiudoll) slurries, but diazinon slightly inhibited urease activity in Maury soil (fine, mixed, semiactive, mesic Typic Paleudalf) slurries. Imidacloprid had no effect on urease activity in creeping bentgrass or bluegrass sod at up to 10 times the commercial application rate. Diazinon briefly, but significantly, reduced urease activity in bluegrass sod. Co-application of imidacloprid and urea appears to be benign with respect to urease activity in soil and sod. Diazinon, in contrast, appears to have a significant, short-term, inhibitory effect on the microbial urease-producing community, but that effect depends on soil type.