Characterized by expensive housing, high socioeconomic status, and topographic relief, Upper Sonoran Lifestyle communities
are found primarily along the Wildland-Urban Interface (WUI) in the Phoenix, Arizona metro area. Communities like these sprawl
into the wildlands in the United States Southwest, creating a distinct urban fringe. This article, through locational comparison,
introduces and evaluates a new field assessment tool for monitoring anthropogenic impact on soil–vegetation interactions along
the well-maintained multi-use recreational trails in Upper Sonoran Lifestyle region. Comparing data from randomly selected
transects along other multi-use trails with data from a control site revealed three key indicators of anthropogenic disturbances
on soil–vegetation interactions: soil disturbance, vegetation disturbance, and vegetation density. Soil and vegetation disturbance
displayed an average distance decay exponent factor of −0.60, while vegetation density displayed a reverse decay average of
0.60. Other important indicators of disturbance included vegetation type, biological soil crusts, and soil bulk density. The
predictive ability of this new field tool enhances its applicability, offering a powerful rapid ecological assessment method
for monitoring long-term anthropogenic impact in the Upper Sonoran Lifestyle, and other sprawling cities along the WUI. 相似文献
Abstract: Excessive loads of nutrients transported by tributary rivers have been linked to hypoxia in the Gulf of Mexico. Management efforts to reduce the hypoxic zone in the Gulf of Mexico and improve the water quality of rivers and streams could benefit from targeting nutrient reductions toward watersheds with the highest nutrient yields delivered to sensitive downstream waters. One challenge is that most conventional watershed modeling approaches (e.g., mechanistic models) used in these management decisions do not consider uncertainties in the predictions of nutrient yields and their downstream delivery. The increasing use of parameter estimation procedures to statistically estimate model coefficients, however, allows uncertainties in these predictions to be reliably estimated. Here, we use a robust bootstrapping procedure applied to the results of a previous application of the hybrid statistical/mechanistic watershed model SPARROW (Spatially Referenced Regression On Watershed attributes) to develop a statistically reliable method for identifying “high priority” areas for management, based on a probabilistic ranking of delivered nutrient yields from watersheds throughout a basin. The method is designed to be used by managers to prioritize watersheds where additional stream monitoring and evaluations of nutrient‐reduction strategies could be undertaken. Our ranking procedure incorporates information on the confidence intervals of model predictions and the corresponding watershed rankings of the delivered nutrient yields. From this quantified uncertainty, we estimate the probability that individual watersheds are among a collection of watersheds that have the highest delivered nutrient yields. We illustrate the application of the procedure to 818 eight‐digit Hydrologic Unit Code watersheds in the Mississippi/Atchafalaya River basin by identifying 150 watersheds having the highest delivered nutrient yields to the Gulf of Mexico. Highest delivered yields were from watersheds in the Central Mississippi, Ohio, and Lower Mississippi River basins. With 90% confidence, only a few watersheds can be reliably placed into the highest 150 category; however, many more watersheds can be removed from consideration as not belonging to the highest 150 category. Results from this ranking procedure provide robust information on watershed nutrient yields that can benefit management efforts to reduce nutrient loadings to downstream coastal waters, such as the Gulf of Mexico, or to local receiving streams and reservoirs. 相似文献
Extraction of labile metals from solid media is environmentally more meaningful than a total digestion. A variety of reagents
have been introduced in the literature, but dilute HCl has received the greatest attention. We compare metal concentrations
liberated by a dilute HCl leach with the sum of the 3-step optimized (standardized) BCR sequential extraction procedure. This
is the first study to compare these procedures over a range of grain sizes. Road-deposited sediments from 10 sites in Honolulu
were fractionated into six grain size classes. Aliquots of individual fractions were digested with dilute HCl, the 3-step
BCR procedure (‘labile’), and a 4-acid (total) procedure. Results indicated that the weighted labile concentrations of Al,
Cu, Fe, Mn, Ni, Pb and Zn were statistically greater than those from the dilute HCl leach. However, regression analysis indicated
strong statistically significant relationships between the two partial extraction procedures for all metals. On a whole-sample
basis, the toxicity classifications for anthropogenic-enhanced metals (Cu, Pb and Zn) were similar between extractions. Taken
together, results suggest that the application of dilute HCl to solid media provides a rapid, cost-effective, and environmentally
meaningful approach for contaminant monitoring. 相似文献
Biosolid application to soil may be a supply of nutrients and micronutrients but it may also accumulate toxic compounds which would be absorbed by crops and through them be incorporated to the trophic chain.
The present study deals with the effect of biosolid application on Cr, Cu, Pb, Ni, and Zn in agricultural soils. The procedure used is sequential extraction so that the availability of those metals may be estimated and related to their bioavailability as determined through two indicator plants grown in greenhouse: ryegrass (Lolium perenne L.) and red clover (Trifolium pratense). Results showed that biosolid application to soil increased total Cu and Zn content. Sequential extraction showed that the more labile Zn fractions increased after biosolid application to soil. This was confirmed when assessing the total content of this metal in shoot and root of the plants under study, since a higher content was found in plant tissues, while no significant differences were found for Cu, Cr, Ni, and Pb. 相似文献