Sediment Contaminant Chemistry and Toxicity of Freshwater Urban Wetlands in Southern California1

Brown, Jeffrey S., Martha Sutula, Chris Stransky, John Rudolph, and Earl Byron, 2010. Sediment Contaminant Chemistry and Toxicity of Freshwater Urban Wetlands in Southern California. Journal of the American Water Resources Association (JAWRA) 46(2):367-384. DOI: 10.1111/j.1752-1688.2009.00407.x Abstract: Wetlands provide many critical functions in urban ecosystems, including habitat for wetland-dependent fauna and enhancement of water quality. Interest in restoring or creating wetlands to enhance these functions is increasing due to the scale and extent of wetland loss and water quality problems associated with urbanization. One of the most pressing questions associated with urban wetland restoration is the extent to which urban wetlands tend to concentrate contaminants, and if so, whether an associated risk to wildlife exists. The goal of this study was to better understand these potential risks, and the associated tradeoffs with using wetlands to treat urban runoff. Sediment toxicity, contaminant chemistry, and macroinvertebrate (MI) community metrics were measured in 21 southern California wetlands that receive urban runoff as their primary water source. MI organisms in 18 of the 21 urban wetlands examined were considered to be at risk due to sediment contaminant concentrations and toxicity. Most of the sites were either toxic to the amphipod Hyalella azteca, exceeded a sediment quality guideline, or both. Sediment chemistry and toxicity identification evaluation studies suggest that pyrethroid pesticides may have been responsible for much of the toxicity documented in this study. The mean Probable Effects Concentration quotient (an index of degree of sediment contamination) was found to negatively correlate with MI diversity in these wetlands suggesting that toxicity was affecting organisms at the base of the food chain in these wetlands.     

Use of created cattail (Typha) wetlands in mitigation strategies

In order to balance pressures for land-use development with protection of wetland resources, artificial wetlands have been constructed in an effort to replace lost ecosystems. Despite its regulatory appeal and prominent role in current mitigation strategies, it is unclear whether or not created systems actually compensate for lost wetland resources. Mitigation predictions that rely on artificial wetlands must be analyzed critically in terms of their efficacy. Destruction of wetlands due to burial by coal fly ash at a municipal landfill in Danvers, Massachusetts, USA, provided an opportunity to compare resulting growth of created cattail (Typha) marshes with natural wetland areas. Once the appropriate cattail species was identified for growth under disturbed landfill conditions, two types of artificial wetlands were constructed. The two systems differed in their hydrologic attributes: while one had a surface water flow characteristic of most cattail wetlands, the second system mimicked soil and water conditions found in naturally occurring floating cattail marshes. Comparison of plant growth measurements for two years from the artificial systems with published values for natural cattail marshes revealed similar structure and growth patterns. Experiments are now in progress to investigate the ability of created cattail marshes to remove and accumulate heavy metals from polluted landfill leachate. Research of the type reported here must be pursued aggressively in order to document the performance of artificial wetlands in terms of plant structure and wetland functions. Such research should allow us to start to evaluate whether artificial systems actually compensate for lost wetlands by performing similar functions and providing the concomitant public benefits.     

Comparison of Function of Created Wetlands of Two Age Classes in Central Pennsylvania

Hydrogeomorphic (HGM) functional assessment models were used to assess whether function in created wetlands of two ages (1 year old and >12 years old) was equivalent to that of natural (reference) mainstem floodplain wetlands. Reference wetlands scored higher than both created age classes for providing energy dissipation and short-term surface water storage. Reference wetlands scored higher in maintaining native plant community and structure than 1-year-old sites, and 12-year-old wetlands scored higher than reference sites for providing vertebrate habitat structure. Analysis of individual model variables showed that reference wetlands had greater vegetative biomass and higher soil organic matter content than both created wetland age classes. Created wetlands were farther from natural wetlands and had smaller mean forest patch sizes within a 1-km-radius circle around the site than did the reference sites, indicating less hydrologic connectivity. Created wetlands also had less microtopographic variation than reference wetlands. The 1-year-old created sites were placed in landscape settings with greater land use diversity and road density than reference sites. The 12-year-old sites had a higher gradient and a higher percentage of their surrounding area in urban land use. These results show that the created wetlands were significantly structurally different (if not functionally so) from reference wetlands even after 12 years. The most profound differences were in hydrology and the characteristics of the surrounding landscape. More attention needs to be focused on placing created wetlands in appropriate settings to encourage proper hydrodynamics, eliminate habitat fragmentation, and minimize the effects of stressors to the site.     

人工湿地的生态休闲利用与设计

人工湿地系统除了可以起到净化污水的作用,在经过精心设计后,还可发挥与自然湿地系统同样的生态保护功能,更可为人们提供一个休闲娱乐、旅游观光、科教科研的场所,越来越多的人工湿地系统开始重视并采用一系列的设计手段以充分发挥其自然价值和社会价值。本文详细地介绍了目前人工湿地综合利用研究进展,分析了综合利用时一些潜在的问题,及其设计时应当加以考虑的注意事项和建议。     

多工艺组合人工湿地在西北农村地区的发展现状及展望

介绍了人工湿地的分类和特点,发展组合人工湿地的原因及国内外近年来多工艺组合人工湿地发展现状及未来趋势,结合实际分析各个工艺的优点与不足.对多工艺组合人工湿地在我国西北农村地区的使用进行分析和展望,可运用组合人工湿地工艺弥补传统水处理工艺的不足,如光催化高级氧化法与人工湿地组合工艺可有效减少水处理时产生的二次污染和土地占...     

Estimating the Benefits of Environmental Enhancement: A Case Study of the River Darent

The provision of leisure facilities is usually assessed on their value to users. This paper outlines the use of contingent valuation methods in an ex ante appraisal of the costs and benefits of enhancing river flow for recreational purposes in a low flow river. A number of rivers in England and Wales experience low flows, especially during summer months, due to over abstraction of water, creating a trade-off between leisure uses and the demands of water consumers. The sequential benefits of enhanced flows are estimated from those associated with abstraction up to licensed limits: to river flow at 70% of licensed abstraction levels; to flow levels required for an environmentally acceptable flow regime, which would permit leisure activities such as fishing, enhanced scenic walking and wildlife encounters. These benefits are compared to the costs which would be incurred to achieve these enhanced flow regimes. The study illustrates the importance of including non-user benefits in benefit-cost analysis, if leisure provision is to be provided in certain areas.     

Valuing Recreational Benefits of Coral Reefs: The Case of Mombasa Marine National Park and Reserve, Kenya

A contingent valuation study was conducted with adult Kenyan citizens and foreign tourists to estimate the value of recreational benefits arising from coral reefs at Mombasa Marine National Park and Reserve (MMNPR), and to assess the implications for local reef management. Citizen and foreign visitors to MMNPR were willing to pay an extra $2.2 (median = $2.2 (median = 1.6) and $8 (median = $8 (median = 6.7) per visit respectively, in addition to current park entrance fees, to support reef quality improvements. By aggregating visitors’ willingness to pay bids over the number of visitors to MMNPR in 2006–2007 the value of benefits was estimated at 346,733, which was more than twice the total annual operational expenditure of346,733, which was more than twice the total annual operational expenditure of 152,383 for MMNPR. The findings indicate that annual revenues from citizen and foreign visitors may be increased by 60% to 261,932 through the implementation of proposed higher park fees of261,932 through the implementation of proposed higher park fees of 3.10 for citizens and $15 for foreign visitors. However, any fee increase would serve to intensify concerns among citizens that only relatively affluent Kenyans can afford to visit MMNPR. Park managers need to demonstrate that the extra revenue would be used to fund the proposed conservation activities. This valuation study demonstrates that visitors are prepared to pay higher user fees for access to the marine protected area revealing considerable untapped resource to finance reef quality improvements.     

Vegetative Ecological Characteristics of Restored Reed (Phragmites australis) Wetlands in the Yellow River Delta, China

In this study, we compared ecological characteristics of wetland vegetation in a series of restoration projects that were carried out in the wetlands of Yellow River Delta. The investigated characteristics include plant composition structure, species diversity and community similarity in three kinds of Phragmites australis wetlands, i.e. restored P. australis wetlands (R1, R2, R3 and R4: restored in 2002, 2005, 2007 and 2009, respectively), natural P. australis wetland (N) and degraded P. australis wetland (D) to assess the process of wetlands restoration. The coverage of the R1 was 99%, which was similar to natural wetland. Among all studied wetlands, the highest and lowest stem density was observed in R1 and R2, respectively, Plant height and stem diameter show the same trend as N > R2 > R1 > R3 > D > R4. Species diversity of restored P. australis wetlands became closed to natural wetland. Both species richness and Shannon–Wiener index had similar tendency: increased first and then decreased with restored time. The highest species richness and species diversity were observed in R2, while the lowest values of those parameters were found in natural P. australis wetland. Similarity indexes between restored wetlands and natural wetland increased with the restoration time, but they were still less than 50%. The results indicate that the vegetation of P. australis wetlands has experienced a great improvement after several years’ restoration, and it is feasible to restored degraded P. australis wetlands by pouring fresh water into those wetlands in the Yellow River Delta. However, it is notable that costal degraded P. australis wetland in this region may take years to decades to reach the status of natural wetland.     

The Importance of Supratidal Habitats for Wintering Shorebirds and the Potential Impacts of Shrimp Aquaculture

Intensive black tiger shrimp (Penaeus monodon) aquaculture ponds have replaced significant areas of coastal wetlands throughout tropical Asia. Few studies have assessed potential impacts on avian foraging habitats. At Khao Sam Roi Yod National Park, Thailand, seminatural wetlands have been converted to either shrimp ponds or to salinization ponds that provide saline water for shrimp aquaculture. Although shorebirds cannot feed in aquaculture ponds, hypersaline ponds can provide productive foraging areas. Thus, the overall impact of the shrimp industry on shorebirds depends partly on the relative quality of the salt ponds compared to seminatural wetlands. In this study, we examined wintering shorebird use of tidal (N = 5 sites) and supratidal areas (four wetland sites, four salt pond sites) and compared the shorebird community (14 species), prey availability, profitability, and disturbance rates between wetlands and salt ponds. Two shorebird species fed in higher densities in wetlands, whereas seven species were more abundant in salt ponds. Large juvenile fish and dragonfly larvae were more abundant in wetlands, whereas there were more small Chironomid midge and fly larvae in salt ponds. We conclude that salt ponds might provide higher-quality foraging habitats compared to wetlands for small shorebirds species because of the abundance of small larvae. However, the shrimp aquaculture industry reduces habitat availability for shorebirds feeding on larger prey. This study demonstrates a comprehensive, multispecies approach to assess the impacts of a large-scale change in coastal habitats for wintering shorebirds.     

Quantitative assessment of tidal wetlands using remote sensing

Effective management of tidal wetlands requires periodic data on the boundaries, extent, and condition of the wetlands. In many states, wetlands are defined wholly, or in combination with other criteria, by the presence of particular emergent halophytic plants. Many important characteristics of the wetlands ecosystem are related directly to the production of emergent plant material or may be inferred from knowledge of the distribution of emergent plant species. Remote-sensing techniques have been applied to mapping of the distribution of wetland vegetation but not to quantitative evaluation of the condition of that vegetation.Recent research in the tidal wetlands of Delaware and elsewhere has shown that spectral canopy reflectance properties can be quantitatively related to the emergent green biomass ofSpartina alterniflora (salt marsh cord grass) throughout the peak growing season (April through September, in Delaware). Periodic measurements of this parameter could be applied to calculations of net aerial primary productivity for large areas ofS. alterniflora marsh in which conventional harvest techniques may be prohibitively time consuming. The method is species specific and, therefore, requires accurate discrimination ofS. alterniflora from other vegetation types. Observed seasonal changes in species spectral signatures are shown to have potential for improving multispectral categorization of tidal wetland vegetation types.     

Waterbird Population Changes in the Wetlands at Chongming Dongtan in the Yangtze River Estuary,China

We studied the changes in wetland habitats and waterbird communities between the 1980s and the 2000s at Chongming Dongtan, a Ramsar site in the Yangtze River estuary, an ecologically important region. This region is an important stopover site for shorebirds along the East Asian–Australasian flyway and is extensively used by waterfowl. A net loss of 11% of the wetland area was estimated during study periods at Chongming Dongtan. The change was dependent on wetland types: while the area of artificial habitats such as paddy fields and aquacultural ponds more than doubled, more than 65% of natural habitats including sea bulrush (Scirpus mariqueter) and common reed (Phragmites australis) marshes were lost over the two decades. An exotic plant species introduced from North America, smooth cordgrass (Spartina alterniflora), occupied 30% of the vegetated intertidal zone by the 2000s. Although waterbird species richness did not change between the 1980s (110) and the 2000s (111), 13 species found in 1980s were replaced by 14 newly recorded species. Moreover, there were more species with declining trends (58) than with increasing trends (19). The population trends of species were affected by residential status and habitat types. Transients, wintering migrants, and habitat specialists were more likely to show declining trends compared to those breeding at Dongtan (including year-round and summer residents) and habitat generalists. Furthermore, species associated mainly with natural wetlands were more likely to decline than those associated mainly with artificial wetlands. These patterns suggest that the loss and change of wetland habitats at Chongming Dongtan adversely affected local population dynamics and might have contributed to the global decline of some waterbird species. Because Chongming Dongtan provides stopover and wintering habitats for many migratory waterbirds, protection and restoration of natural wetlands at Chongming Dongtan are urgently needed.     

Wise Use of Wetlands: Current State of Protection and Utilization of Chinese Wetlands and Recommendations for Improvement

Wetland protection and utilization sometimes appear to be in conflict, but promoting the wise use of wetlands can solve this problem. All countries face the challenge of sustainable development of wetlands to a greater or lesser extent, but the problem is especially urgent in developing countries, such as China, that want to accelerate their economic development without excessive environmental cost. Chinese wetlands contribute greatly to economic development, but improper use of these natural resources has endangered their existence. It is thus necessary to provide scientific guidance to managers and users of wetlands. In this paper, we analyze the present status of Chinese wetland protection and utilization, and discuss problems in six categories: a lack of public awareness of the need for wetland protection; insufficient funding for wetland protection and management; an imperfect legal system to protect wetlands; insufficient wetland research; lack of coordination among agencies and unclear responsibilities; and undeveloped technologies related to wetland use and protection. The wise use of Chinese wetlands will require improvements in four main areas: increased wetland utilization research, scientific management of wetland utilization, improved laws and regulations to protect wetlands, and wider dissemination of wetland knowledge. Based on these categories, we propose a framework for the optimization of wetland use by industry to provide guidance for China and other countries that cannot sacrifice economic benefits to protect their wetlands.     

Non-market valuation of off-highway vehicle recreation in Larimer County, Colorado: Implications of trail closures

Few economic studies are available to measure off-highway vehicle recreation benefits foregone when trails must be closed to protect the environment. This paper estimates the non-market benefits associated with off-highway vehicle (OHV) recreation on National Forest lands in Larimer County, Colorado. We use a contingent valuation model (CVM) to estimate benefits to OHV users, which includes dirt bike riders, all terrain vehicle (ATV) riders, and 4-wheel drive (4 × 4) users. Using CVM we find the mean consumer surplus estimates to be $78 per person per day. These results are consistent with the few previous estimates of OHV recreation benefits. This equates to a per trail per summer consumer surplus of at least between $219,467 and $296,876, and a county level surplus per summer to be at least between $796,447 and $1,077,367. These benefits can be compared to environmental costs to obtain a more complete picture of the effects of trail closure, as well as the negative spillovers to non-motorized users.     

Building Local Community Commitment to Wetlands Restoration: A Case Study of the Cache River Wetlands in Southern Illinois, USA

Natural resource professionals are increasingly faced with the challenges of cultivating community-based support for wetland ecosystem restoration. While extensive research efforts have been directed toward understanding the biophysical dimensions of wetland conservation, the literature provides less guidance on how to successfully integrate community stakeholders into restoration planning. Therefore, this study explores the social construction of wetlands locally, and community members’ perceptions of the wetland restoration project in the Cache River Watershed of southern Illinois, where public and private agencies have partnered together to implement a large-scale wetlands restoration project. Findings illustrate that the wetlands hold diverse and significant meanings to community members and that community members’ criteria for project success may vary from those identified by project managers. The case study provides managers with strategies for building community commitment such as engaging local citizens in project planning, minimizing local burdens, maximizing local benefits, and reducing uncertainty.     

Status and trends of freshwater wetlands in the coal-mining region of Pennsylvania,USA

The impact of surface mining for coal on the nature and extent of freshwater wetlands was assessed on 73,200 ha in western Pennsylvania. The influence of mining on wetlands was not uniform across physiographic regions, varying with regional differences in hydrology and soils. Overall, mined lands supported 18% more palustrine wetlands than unmined lands, primarily because of a 270% gain in permanent, open-water wetlands on mined lands in the glaciated region. Open-water wetlands declined on mined lands in unglaciated regions owing to unfavorable hydrologic conditions. The number and size of emergent wetlands declined as a result of mining. Mined lands supported 81% fewer riverine wetlands than unmined lands. This was caused primarily by avoidance of lands containing streams, and secondarily by a 10% reduction in replacement of riverine wetlands during reclamation. Land managers need to develop land use policies that maximize the ecological and social benefits that can be derived from developing diverse wetland communities on mined lands.     

Intelligent Databases Assist Transparent and Sound Economic Valuation of Ecosystem Services

Assessment and economic valuation of services provided by ecosystems to humans has become a crucial phase in environmental management and policy-making. As primary valuation studies are out of the reach of many institutions, secondary valuation or benefit transfer, where the results of previous studies are transferred to the geographical, environmental, social, and economic context of interest, is becoming increasingly common. This has brought to light the importance of environmental valuation databases, which provide reliable valuation data to inform secondary valuation with enough detail to enable the transfer of values across contexts. This paper describes the role of next-generation, intelligent databases (IDBs) in assisting the activity of valuation. Such databases employ artificial intelligence to inform the transfer of values across contexts, enforcing comparability of values and allowing users to generate custom valuation portfolios that synthesize previous studies and provide aggregated value estimates to use as a base for secondary valuation. After a general introduction, we introduce the Ecosystem Services Database, the first IDB for environmental valuation to be made available to the public, describe its functionalities and the lessons learned from its usage, and outline the remaining needs and expected future developments in the field.     

The Value of Footpath Provision in the Countryside: A Case-study of Public Access to Urban-fringe Woodland

This paper presents a case-study of valuation of public access to a woodland site owned by The Crown Estate in Windsor Forest. It supports the view that contingent valuation is an appropriate technique to use for assessing recreational benefits in the countryside and that consistent and useful results can be obtained. The study found that the recreational benefits far outweighed the costs of access provision, thus giving reassurance to the providers that their efforts are worthwhile.     

Comparing the Economic Value of Mountain Biking Estimated Using Revealed and Stated Preference

This research compares non-market valuation techniques by applying a count data travel cost method (TCM) and dichotomous choice contingent valuation method (CVM) to a form of recreation for which it has not been previously applied: mountain biking. Due to mountain biking's increasing popularity these estimates of benefits may be useful in addressing conflicts. One of the most famous mountain biking sites in the US (Moab, Utah) was chosen as the site for which to apply these two models. The benefits that were estimated for trips taken in the spring of 1996 are US$205 and US$235,for the TCM and CVM, respectively.These values are not statistically different using conventional significant levels.     

Human Influences on Water Quality in Great Lakes Coastal Wetlands

A better understanding of relationships between human activities and water chemistry is needed to identify and manage sources of anthropogenic stress in Great Lakes coastal wetlands. The objective of the study described in this article was to characterize relationships between water chemistry and multiple classes of human activity (agriculture, population and development, point source pollution, and atmospheric deposition). We also evaluated the influence of geomorphology and biogeographic factors on stressor-water quality relationships. We collected water chemistry data from 98 coastal wetlands distributed along the United States shoreline of the Laurentian Great Lakes and GIS-based stressor data from the associated drainage basin to examine stressor-water quality relationships. The sampling captured broad ranges (1.5–2 orders of magnitude) in total phosphorus (TP), total nitrogen (TN), dissolved inorganic nitrogen (DIN), total suspended solids (TSS), chlorophyll a (Chl a), and chloride; concentrations were strongly correlated with stressor metrics. Hierarchical partitioning and all-subsets regression analyses were used to evaluate the independent influence of different stressor classes on water quality and to identify best predictive models. Results showed that all categories of stress influenced water quality and that the relative influence of different classes of disturbance varied among water quality parameters. Chloride exhibited the strongest relationships with stressors followed in order by TN, Chl a, TP, TSS, and DIN. In general, coarse scale classification of wetlands by morphology (three wetland classes: riverine, protected, open coastal) and biogeography (two ecoprovinces: Eastern Broadleaf Forest [EBF] and Laurentian Mixed Forest [LMF]) did not improve predictive models. This study provides strong evidence of the link between water chemistry and human stress in Great Lakes coastal wetlands and can be used to inform management efforts to improve water quality in Great Lakes coastal ecosystems.     

Nitrate Removal in a Restored Spring‐Fed Wetland,Pennsylvania, USA1

ABSTRACT:  In 2001, the 1.04‐ha Hornbaker wetland in south‐central Pennsylvania was restored by blocking an artificial drainage ditch to increase water storage and hydraulic retention time (HRT). A primary goal was to diminish downstream delivery of nitrate that enters the wetland from a limestone spring, its main source of inflow. Wetland inflow and outflow were monitored weekly for two years to assess nitrate flux, water temperature, pH, and specific conductivity. In Year 2, spring discharge was measured weekly to allow calculation of nitrate loads and hydraulic retention time. Surface runoff was confirmed to be a small fraction of wetland inflows via rainfall‐runoff modeling with TR‐55. The full dataset (n = 102) was screened to remove 13 weeks in which spring discharge constituted < 85% of total inflows because of high precipitation and surface runoff. Over two years (n = 89), mean nitrate‐nitrogen concentrations were 7.89 mg/l in inflow and 3.68 mg/l in outflow, with a mean nitrate removal of 4.19 mg/l. During Year 2 (n = 47), for which nitrate load data were available, the wetland removed an average of 2.32 kg N/day, 65% of the load. Nitrate removal was significantly correlated with HRT, water temperature, and the concentration of nitrate in inflow and was significantly greater during the growing season (5.36 mg/l, 64%) than during the non‐growing season (3.23 mg/l, 43%). This study indicates that hydrologic restoration of formerly drained wetlands can provide substantial water quality benefits and that the hydrologic characteristics of spring‐fed wetlands, in particular, support effective nitrogen removal.