Maintaining Volunteer Commitment to Local Watershed Initiatives

Australia's Landcare program is advanced as a successful international example of local watershed groups and governments working together to improve natural resource management. One of the aspects considered critical in the success of watershed groups is engaging widespread participation. This paper draws on two regional surveys that explored burnout, or loss of engagement, among Landcare participants in the state of Victoria using the Maslach Burnout Inventory. Survey findings indicated that a large proportion of respondents were experiencing high burnout in terms of low personal accomplishment and suggested that there was potential for burnout to increase. The authors suggest that the expectations of watershed groups must be based around a realistic assessment of the capacity for volunteer groups to deliver improved environmental and social outcomes.     

Remote Assessment of Forest Health in Southern Arizona, USA: Evidence for Ozone-Induced Foliar Injury

This paper examines possible ozone-induced foliar injury to ponderosa pine areas in the Rincon Mountains of southern Arizona from 1972 to 1992. Spatiotemporal differences in a satellite-derived vegetation index (VI) are examined with respect to antecedent moisture conditions, temporal variations in ozone exposure levels, and measured foliar injury values from 1985. Seasonal ozone exposure levels (SUM60 and W126) increased from 1982 to 1998 and were significantly correlated (r = 0.49 and 0.53, α= 0.05) with annual population totals in the Tucson area. Extensive masking of satellite images from 1972, 1986, and 1992 resulted in two optimal change detection areas, with one site, TVWMica, exposed mostly to the Tucson air pollution plume, while the other site, EMica, was more protected from Tucson-derived pollution. An overall increase in VI from 1972 to 1992 at both sites appears to have been caused by an increase in moisture availability. Larger foliar injury values in 1985 were associated with a smaller increase in VI (i.e., a smaller increase in green leaf biomass) from 1972 to 1986. From 1972 to 1986 and from 1986 to 1992, VI values at TV/WMica increased at a slower rate compared to those at EMica. The reduced increase in “green-up” may have been caused partially by ozone-induced foliar injury and resulting decreases in green leaf biomass. However, these spatial differences in VI values may have also been caused by a number of other factors. Results nevertheless reveal the strong possibility of distinct, topographically based, spatial variations in ozone-induced foliar injury within the Rincons.     

Potential Long-Term Ecological Impacts Caused by Disturbance of Contaminated Sediments:A Case Study

Several submerged barges were recently removed from the Passaic River, New Jersey, USA, in two areas (areas 1 and 2) where contaminated sediments are known to exist. During removal of the single barge in area 1, elevated turbidity levels and chemical parameters were measured. Greater increases were measured in area 2, where several barges were removed. In both areas, water column concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and several metals exceeded one or more water quality criteria; turbidity levels in area 2 also exceeded regulatory criteria. Potential chemical bioaccumulation from the water column into residential aquatic receptors was estimated using standard models and assumptions. The modeled results predicted that steady-state tissue concentrations of bioaccumulative chemicals would not occur as a result of the brief increase in water column concentrations that occurred during barge removal but that metals and PCDD/Fs could bioaccumulate to levels that exceed regulatory ecological criteria during long-term sediment disturbance activities. In addition, based on some simplistic assumptions regarding settling of suspended sediments, we estimate that chemical bioaccumulation from surface sediments into the food web could result in substantial increases in PCDD/F body burdens in the benthic forage fish, mummichog. Our findings are consistent with the limited number of field studies that have measured increased body burdens of bioaccumulative chemicals following dredging. We suggest that, prior to consideration of extensive dredging as a remedial alternative for any river system, the potential significant and long-term impacts on the food web must be evaluated.     

Risk-Based Analysis of Environmental Monitoring Data: Application to Heavy Metals in North Carolina Surface Waters

The state of North Carolina's Department of Environment and Natural Resources (NCDENR) conducts routine water quality monitoring throughout the state to assess the health of aquatic systems. The current study reports the results of a retrospective (1990–2000) ecological risk assessment of six heavy metals (arsenic, cadmium, copper, lead, mercury, and zinc) in 17 North Carolina basins that was conducted to estimate the risk of heavy metal toxicity to freshwater organisms and assess the sufficiency of NCDENR's monitoring data to identify water-quality-related ecological threats. Acute and chronic ecotoxicological thresholds (ETs) were calculated for each metal based upon the 10th percentile of species sensitivity distributions and were normalized for water hardness. Statewide probabilities (expressed as percentages) of a random sample exceeding acute or chronic ETs among the six metals ranged from 0.01% to 12.19% and 0.76% to 21.21%, respectively, with copper having the highest and arsenic and mercury the lowest risk. Basin-specific probabilities varied significantly depending upon water hardness and presumably watershed development. Although the majority of specific sites where data were collected were at low risk for metal toxicity, some specific sites had a high probability of toxic events associated with one or more metals. Analytical detection limits for metals were frequently higher than estimated chronic ET, limiting the ability to assess the risk of chronic toxicity in soft-water basins. Results suggest risk-based criteria may be useful for assessing and validating the sufficiency of monitoring programs and prioritizing management goals.     

Testing the Basic Assumption of the Hydrogeomorphic Approach to AssessingWetland Functions

The hydrogeomorphic (HGM) approach for developing "rapid" wetland function assessment methods stipulates that the variables used are to be scaled based on data collected at sites judged to be the best at performing the wetland functions (reference standard sites). A critical step in the process is to choose the least altered wetlands in a hydrogeomorphic subclass to use as a reference standard against which other wetlands are compared. The basic assumption made in this approach is that wetlands judged to have had the least human impact have the highest level of sustainable performance for all functions. The levels at which functions are performed in these least altered wetlands are assumed to be "characteristic" for the subclass and "sustainable." Results from data collected in wetlands in the lowlands of western Washington suggest that the assumption may not be appropriate for this region. Teams developing methods for assessing wetland functions did not find that the least altered wetlands in a subclass had a range of performance levels that could be identified as "characteristic" or "sustainable." Forty-four wetlands in four hydrogeomorphic subclasses (two depressional subclasses and two riverine subclasses) were rated by teams of experts on the severity of their human alterations and on the level of performance of 15 wetland functions. An ordinal scale of 1-5 was used to quantify alterations in water regime, soils, vegetation, buffers, and contributing basin. Performance of functions was judged on an ordinal scale of 1-7. Relatively unaltered wetlands were judged to perform individual functions at levels that spanned all of the seven possible ratings in all four subclasses. The basic assumption of the HGM approach, that the least altered wetlands represent "characteristic" and "sustainable" levels of functioning that are different from those found in altered wetlands, was not confirmed. Although the intent of the HGM approach is to use level of functioning as a metric to assess the ecological integrity or "health" of the wetland ecosystem, the metric does not seem to work in western Washington for that purpose.     

Managing Urban Trees and Their Soil Envelopes in a Contiguously Developed City Environment

Urban Hong Kong is covered by high building, road, and population densities. Its urban morphology is inherently not conducive to extensive or high-grade greening. Recent renewal of old areas has squeezed out some limited interstitial plantable space, although in new development areas modest spaces have been earmarked for greenery. The study aims at evaluating the major constraints to urban trees and their companion urban soil envelopes and at providing specific recommendations to improve tree management in the city. The analysis covers the above-ground confinements that dampen tree performance, the less tangible but rather difficult institutional restrictions that impose a somewhat unnecessary lid on tree planting, the multiplicity of players and stakeholders involved in urban-tree management that militates against coordination and cooperation, the widespread occupation of underground space by utility lines often to the exclusion of trees, and the extremely poor quality of urban soils that are often used without amelioration to support tree growth. The management recommendations furnish practical suggestions and hints to improve the short- and long-term welfare of trees in terms of quality, quantity, and spatial distribution. The conclusion enumerates some concrete measures for consideration by decision-makers to upgrade the city's greenery to close the gap between science and policy.     

Land-use dynamics in a southern Illinois (USA) watershed

The Cache River of southernmost Illinois is used as a case study for developing and demonstrating an approach to quantitatively link (1) national agricultural policy and global agricultural markets, (2) landowner's decisions on land use, (3) spatial patterns of land use at a watershed scale, and (4) hydrologic impacts, thus providing a basis to predict, under a certain set of circumstances, the environmental consequences of economic and political decisions made at larger spatial scales. The heart of the analysis is an estimation, using logistic regression, of the affect of crop prices and Conservation Reserve Program (CRP) rental rates on farmland owner's decisions whether to reenroll in the CRP or return to crop production. This analysis shows that reasonable ranges for crop prices (80%–150% of 1985–1995 values) and CRP rental rates (0–125% of 1985–1995 rates) result in a range of 3%–92% of CRP lands being returned to crop production, with crop prices having a slightly greater effect than CRP rental rates. Four crop price/CRP rental rate scenarios are used to display resulting land-use patterns, and their effect on sediment loads, a critical environmental quality parameter in this case, using the agricultural non point source (AGNPS) model. These scenarios demonstrate the importance of spatial pattern of land uses on hydrological and ecological processes within watersheds. The approach developed can be adapted for use by local governments and watershed associations whose goals are to improve watershed resources and environmental quality.     

Design and Performance of a Channel Reconstruction Project in a Coastal California Gravel-Bed Stream

A 0.9 km-reach of Uvas Creek, California, was reconstructed as a sinuous, meandering channel in November 1995. In February 1996, this new channel washed out. We reviewed project documents to determine the basis for the project design and conducted our own historical geomorphological study to understand the processes operating in the catchment and project reach. The project was designed using a popular stream classification system, based on which the designers assumed that a "C4" channel (a meandering gravel-bed channel) would be stable at the site. Our historical geomorphological analysis showed that the reach had been braided historically, typical of streams draining the Franciscan Formation in the California Coast Ranges, with episodic flows and high sand and gravel transport. After the project washed out, Uvas Creek reestablished an irregular, braided sand-and-gravel channel, although the channel here was narrower than it had been historically, probably due to such factors as incision caused by gravel mining. Our study casts doubt on several assumptions common in many stream restoration projects: that channel stability is always an appropriate goal; that channel forms are determined by flows with return periods of about 1.5 years; that a channel classification system is an easy, appropriate basis for channel design; and that a new channel form can be imposed without addressing the processes that determine channel form.     

高层建筑热压中和面位置的确定

根据通风网络理论 ,结合建筑物各楼层门窗间的串并联关系 ,率先引入了能够反映建筑门窗结构和气密性特征的特征参量“风阻” ,并应用中和面上、下渗进渗出风量平衡的关系 ,得出了求解热压中和面位置的一元方程式 ,使建筑热压中和面的求解成为可能     

Proactive Management of Air Quality

Traditional air resource management systems have difficulty in addressing global issues, sustainable development, direct citizen participation, and integration with broad economic interests. As reactive management systems, they tend to be compliance-driven, static, and rigid. In contrast, proactive management systems are principle-driven, innovative, and flexible. Bridge scientists play a key role in supporting the transformation of raw data into wise action. Decision-makers need to integrate social values with knowledge about emissions, atmospheric processes, and potential environmental effects using the primary tools of measurements, monitoring, and modeling. The Alberta Clean Air Strategic Alliance, a unique partnership of governments, industry, and public interest groups formed in 1994, operates a comprehensive air management system that is capable of addressing air issues of greater complexity and uncertainty. Its success is measured by the satisfaction of its diverse stakeholders and by the number and scope of its initiatives.