THREE‐DIMENSIONAL KRIGING ANALYSIS OF SEDIMENT MERCURY DISTRIBUTION: A CASE STUDY1

ABSTRACT: This study presents an application of a three‐dimensional kriging technique to estimate spatial distribution of total mercury (Hg) in the Cedar‐Ortega Rivers watershed located in the lower St. Johns River basin, Florida. The kriging procedures, including preliminary data analysis, structural data analysis and the log kriging estimation, are presented. Results show watershed wide Hg contamination of river sediment to a depth of 1.0 m. A three‐dimensional plot of Hg against the Florida Sediment Assessment Guidelines (i.e., the probable effect level or PEL) demonstrates that the Cedar River is more contaminated with Hg than the rest of the watershed. The maximum sediment depth with Hg concentrations above PEL value (0.696 mg/kg) is 1.5 m. Hg concentrations at or above this level could pose a significant hazard to aquatic organisms. Analysis of the spatial distribution of Hg in the watershed finds multiple input sources. This study suggests that there is a need to identify the major sources of Hg in the watershed, and to determine the pathways that allow Hg to enter the river.     

Dams and Flows: Immersing in Western Meaning Systems in Search of Ecocultural Reflexivity

In this unprecedented era of anthropogenic ecological destruction, this study illustrates inadequacies in conceptual language available in Western settings to think deeply and holistically about “nature.” At the same time, the study illustrates transformative potential of moments of ecocultural reflexivity. Using free write methodology, we examine ways participants in the United States, New Zealand, and Australia articulate what they mean when they say “nature.” We interpret participant streams of consciousness as representative of a wider Western river-way, a channel of dominant, multiple, and contradictory meanings in continuous movement. We identify conceptual obstructions that provide glimpses into ways Western ecological relations are bounded and dammed by binary, fragmented, and unconsidered meanings. Yet reflexivity in the face of such obstructions, and in potent ecocultural side streams of childhood remembering and ecocentric cosmology, provides some participants a lucid flow of regenerative narratives at a time such shared stories are urgently needed.     

Application of Ecological Classification and Predictive Vegetation Modeling to Broad-Level Assessments of Ecosystem Health

The Little Missouri National Grasslands (LMNG) of western North Dakota support the largest permitted cattle grazing use within all lands administered by the USDA, Forest Service, as well as critical habitat for many wildlife species. This fact, coupled with the need to revise current planning direction for range allotments of the LMNG, necessitated that a broad-level characterization of ecosystem integrity and resource conditions be conducted across all lands within the study area (approximately 800,000 hectares) in a rapid and cost-effective manner. The approach taken in this study was based on ecological classifications, which effectively utilized existing field plot data collected for a variety of previous inventory objectives, and their continuous spatial projection across the LMNG by maps of both existing and potential vegetation. These two map themes represent current and reference conditions (existing vs. potential vegetation); their intersection allowed us to assign various ecological status ratings (i.e., ecosystem integrity and resource condition) based on the degree of departure between current and reference conditions. In this paper, we present a brief review of methodologies used in the development of ecological classifications, and also illustrate their application to assessments of rangeland health through selected maps of ecological status ratings for the LMNG.     

Correction to: Status and trends of circumpolar peregrine falcon and gyrfalcon populations

While collating contributions and comments from 36 researchers, the coordinating authors accidentally omitted Dr. Suzanne Carrière from the list of contributing co-authors. Dr. Carrière’s data are described in Tables 1 and 3, Figure 2 and several places in the narrative. The new author list is thus updated in this article.     

Comparison of concentrations and stereoisomer ratios of mecoprop, dichlorprop and metolachlor in Ontario streams, 2006-2007 vs. 2003-2004

Mecoprop, dichlorprop and metolachlor concentrations and enantiomer signatures were determined in Ontario streams in 2006-2007 and compared to results from 2003 to 2004. Median concentrations of dichlorprop and metolachlor were not significantly different between the two campaigns, but mecoprop was higher in 2006-2007. Concentrations of mecoprop and dichlorprop in Lake Ontario surface water were 1-2 orders of magnitude lower than stream averages. Enantiomer fractions (EFs) > 0.5 of mecoprop in high-concentration stream water samples during 2006-2007 were related to replacement of racemic mecoprop by single (+) enantiomer mecoprop-P after 2004. EFs <0.5 in low-concentration samples suggested enantioselective degradation and/or interconversion. Metolachlor profiles were expressed as SF, the fraction of herbicidally active/(active + inactive) stereoisomers. Samples with higher concentrations of metolachlor had SFs similar to S-metolachlor which is enriched in the active stereoisomers. Low concentrations were associated with lower and more variable SFs, suggesting mixed input of racemic and S-metolachlor or stereoselective degradation.