Salt Marsh Diking and Restoration: Biogeochemical Implications of Altered Wetland Hydrology

Experimental short-term desalination and drainage of salt marsh cores in greenhouse microcosms caused Spartina production to increase after one growing season, reflecting decreased salt stress and sulfide toxicity. However, production thereafter declined, likely due to pyrite oxidation and acidification in drained treatments and sulfide accumulation in waterlogged treatments. A survey of longer-term (decadal) effects of diking on peat composition of Cape Cod, Massachusetts, USA, marshes revealed acidification, Fe(II) mobilization, and decreased organic content in drained sites. Despite the aerobic decomposition of organic matter, abundant nutrients remained as sorbed NH₄ and mineral-bound PO₄. In diked, seasonally waterlogged sites, porewater alkalinity, sulfide, ammonium and orthophosphate were much lower, and organic solids higher, than in adjacent natural marsh. Seawater was added to cores from diked marshes to study the effects of tidal restoration. Salination of the drained peat increased porewater pH, alkalinity, ammonium, orthophosphate, Fe, and Al; copious ammonium N, and Fe(II) for sulfide precipitation favored Spartina growth. Salination of diked–waterlogged peat increased sulfate reduction and caused 6–8 cm of sediment subsidence. The resulting increase in porewater sulfides and waterlogging decreased vigor of transplanted Spartina alterniflora. Results indicate that seawater restoration should proceed cautiously to avoid nutrient loading of surface waters in drained sites or sulfide toxicity in diked–waterlogged marshes.     

Validity of Performance Criteria and a Tentative Model for Regulatory Use in Compensatory Wetland Mitigation Permitting

The purpose of this paper is to develop the principles for a manageable and practical set of performance criteria that will reasonably assure no net loss in a situation in which it cannot be absolutely assured. To this end, the performance criteria proposed for 116 compensatory wetland projects on file with the Army Corps of Engineers in San Francisco, between 1988 and 1995, were examined. The trends discerned in the project proposals were analyzed and evaluated in light of the current state of wetland science. Specific suggestions for the development of uniform criteria in each of four major wetland types—riparian, perennial tidal, perennial nontidal, and seasonal—are discussed, and a system of regulation tying qualitative assessment with quantitative requirements is outlined as a reasonable solution to the enforcement of the no-net-loss policy.     

Biological Control of Water Hyacinth Under Conditions of Maintenance Management: Can Herbicides and Insects Be Integrated?

Neochetina eichhorniae and N. bruchi. We therefore sampled water hyacinth and weevil populations at 54 sites distributed statewide. Half were under maintenance control, half were not treated with herbicides. General site conditions were assessed, demographic data were collected on weevil and plant populations, the reproductive condition of the weevils was determined, and plant nutrient and proximate composition of water hyacinth leaves were analyzed. Water hyacinth infestations under maintenance control were minimal when compared to unmanaged sites. Likewise, on a population basis, all weevil cohorts were much lower due to the paucity of plants. Plants at unmanaged sites, where weevil intensities were much higher, suffered high levels of stress and showed low growth potential. Lower percentages of the female weevils were reproductive at unmanaged sites when compared to managed sites, so densities of reproductives and immatures were similar at both site types. Reproductive status of the weevils improved with increased plant quality. Plant quality, in turn, declined as stresses arising from weevil feeding increased. Plant quality was positively correlated with plant growth potential and flower production. Thus, maintenance control improved plant nutritive quality thereby inducing reproductive vigor of the weevils, but ensuring plant regrowth and the need for future control. This suggests that biological and herbicidal controls should be integrated, using herbicides to maintain water hyacinth infestations below management thresholds but in a manner that conserves biological control agent populations. This approach would lead to improved plant nutritional quality that would, in turn, stimulate reproduction in biological control agent populations.     

Assessments of Wetland Functions: What They Are and What They Are Not

/ Many methods have been developed over the last two decades to provide information about wetland functions, but there has been little discussion of the models and algorithms used. Methods for generating information about wetlands were analyzed to understand their similarities, differences, and the type of information provided. Methods can first be grouped by the type of information they provide-classifications, characterizations, ratings, assessments, and evaluations. Methods that characterize, rate, or assess wetlands may generate information using one of two conceptual approaches-logic and mechanistic. Most methods that generate a numeric assessment of performance or value of wetland functions rely on the mechanistic approach to constructing models. Rapid assessment methods based on mechanistic models, however, do not assess the rates or dynamics of ecological processes occurring in wetlands. Rather, they provide a clear and concise way of organizing our current, and often subjective, knowledge about wetland functions. This is one limitation of current methods that is often misunderstood both by wetland managers and the scientific community. The advantages and limitations of the assumptions and the computational elements inherent in these approaches are discussed to provide wetland managers and regulators a better understanding of the information they are using. KEY WORDS: Wetlands; Functions; Assessment; Models; Methods     

污染稻、麦籽实中Cd、Cu、Pb的分布及其存在形态初探

采用组织化学及溶剂提取法研究了污染水稻、小麦籽实中Cd、Cu、Pb的分布及存在形态．结果表明,3种金属元素在水稻、小麦籽实各形态结构中的浓度具有明显不均一性,胚中浓度显著高于胚乳,颖壳,皮层中浓度也较高;糙米、麦粒中的Cd、Cu、Pb在去离子水、0.1mol EDTA、1％醋酸、2.5％　NaCl、0.2％NaOH、70％乙醇中的溶出比例有显著差异;综合2项试验结果可以看出Cd、Cu、Pb在籽实中主要与谷物成分结合形成配合物,其优势形态是蛋白质结合态．     

溢油多环芳烃模糊指数的研究

通过用氧化铝柱层析和等梯度呷醇：水=85％：15％）反相高效液相色谱（C18硅烷柱）紫外检测器254nm,测定30多种油品和我国海洋环境油类样品中的多环芳烃（PAHs）,建立了溢油PAHs模糊指数结果表明,油类PAHs响应因子和相对保留值的变异系数分别在8.4％－16.5％和0.00％－5.4％之间,回收率在74.6％－111.2％之间,精密度和准确度较好;海洋环境油类的多环芳烃模糊指数值（0.00383－0.01839）与润滑油类的值（0.00106－0.00942）接近,较石油及其它产品油的值（0.06983－1.00000）低;用润滑油类作为标准油,PAHs模糊指数作为溢油芳烃类监测的指示物（指标）,可提高监测海洋环境油类的代表性和可靠性