Multi-criteria risk management with the use of <Emphasis Type="Italic">DecernsMCDA</Emphasis>: methods and case studies

Emerging challenges of risk management, environmental protection, and land-use planning requires integration of stakeholder values and expert judgment. The process of decision making in situation of high uncertainty can be assisted through the use of decision support systems (DSSs). Such DSSs are often based on tools for spatial data representation (GIS) and environmental models that are integrated using multi-criteria decision analysis (MCDA). This paper presents DecernsMCDA implementing all major types of multi-criteria methods and tools (AHP, MAUT, Outranking) under the same user interface. In addition to providing ability for testing model uncertainty associated with selection of specific MCDA algorithms, DecernsMCDA implements new algorithms for parameter uncertainty analysis based on probabilistic approaches and fuzzy sets. The paper illustrates application of DecernsMCDA for selecting remedial alternative at radiologically contaminated sites.     

Target loads of atmospheric sulfur deposition for the protection and recovery of acid-sensitive streams in the Southern Blue Ridge Province

An important tool in the evaluation of acidification damage to aquatic and terrestrial ecosystems is the critical load (CL), which represents the steady-state level of acidic deposition below which ecological damage would not be expected to occur, according to current scientific understanding. A deposition load intended to be protective of a specified resource condition at a particular point in time is generally called a target load (TL). The CL or TL for protection of aquatic biota is generally based on maintaining surface water acid neutralizing capacity (ANC) at an acceptable level. This study included calibration and application of the watershed model MAGIC (Model of Acidification of Groundwater in Catchments) to estimate the target sulfur (S) deposition load for the protection of aquatic resources at several future points in time in 66 generally acid-sensitive watersheds in the southern Blue Ridge province of North Carolina and two adjoining states. Potential future change in nitrogen leaching is not considered. Estimated TLs for S deposition ranged from zero (ecological objective not attainable by the specified point in time) to values many times greater than current S deposition depending on the selected site, ANC endpoint, and evaluation year. For some sites, one or more of the selected target ANC critical levels (0, 20, 50, 100μeq/L) could not be achieved by the year 2100 even if S deposition was reduced to zero and maintained at that level throughout the simulation. Many of these highly sensitive streams were simulated by the model to have had preindustrial ANC below some of these target values. For other sites, the watershed soils contained sufficiently large buffering capacity that even very high sustained levels of atmospheric S deposition would not reduce stream ANC below common damage thresholds.     

Sorption of arsenic from soil-washing leachate by surfactant-modified zeolite

Post-treatment of leachate from soil-washing remedial actions may be necessary depending on the amounts of dissolved contaminants present. Uptake of arsenic species by surfactant-modified zeolite (SMZ) from a synthetic soil leachate (pH of approximately 12 [NaOH]) was measured as a test of SMZ as a post-treatment sorbent. Batch sorption isotherms were prepared using leachate to SMZ ratios from 40:1 to 4:1, and temperatures of 25 and 15 degrees C. Equilibrium levels of dissolved and total solution arsenic were similar. At each temperature, sorption appeared to reach a plateau or maximum, then decreased at the highest solution concentration, corresponding to the lowest amount of zeolite added (2.5 g). A maximum sorption value of 72.0 mmol of arsenic per kg of SMZ (5400 mg/kg) was observed at 25 degrees C, and 42.1 mmol/kg (3150 mg/kg) at 15 degrees C. Total arsenic recoveries varied from 74 to 125%. Surfactant-modified zeolite removed up to 97% of dissolved organic carbon and decolorized the leachate solutions. Excluding the points for the highest arsenic to SMZ ratio, the sorption isotherms were well described by the linearized form of the Langmuir equation, with coefficients of determination greater than 0.90 at both temperatures. Sorption of arsenic by SMZ is attributed to anion exchange with counterions on the surfactant head groups, and/or partitioning of organic carbon-complexed arsenic into the surfactant bilayer.     

Selection of a water-extractable phosphorus test for manures and biosolids as an indicator of runoff loss potential

The correlation of runoff phosphorus (P) with water-extractable phosphorus (WEP) in land-applied manures and biosolids has spurred wide use of WEP as a water quality indicator. Land managers, planners, and researchers need a common WEP protocol to consistently use WEP in nutrient management. Our objectives were to (i) identify a common WEP protocol with sufficient accuracy and precision to be adopted by commercial testing laboratories and (ii) confirm that the common protocol is a reliable index of runoff P. Ten laboratories across North America evaluated alternative protocols with an array of manure and biosolids samples. A single laboratory analyzed all samples and conducted a separate runoff study with the manures and biosolids. Extraction ratio (solution:solids) was the most important factor affecting WEP, with WEP increasing from 10:1 to 100:1 and increasing from 100:1 to 200:1. When WEP was measured by a single laboratory, correlations with runoff P from packed soil boxes amended with manure and biosolids ranged from 0.79 to 0.92 across all protocol combinations (extraction ratio, filtration method, and P determination method). Correlations with P in runoff were slightly lower but significant when WEP was measured by the 10 labs (r=0.56-0.86). Based on laboratory repeatability and water quality evaluation criteria, we recommend the following common protocol: 100:1 extraction ratio; 1-h shaking and centrifuge 10 min at 1500xg (filter with Whatman #1 paper if necessary); and determining P by inductively coupled plasma-atomic emission spectrometry or colorimetric methods.     

Effects of nutrient limitation on toxin production and composition in the marine dinoflagellate Protogonyaulax tamarensis

Toxin production was measured by high pressure liquid chromatography (HPLC) when the marine dinoflagellate Protogonyaulax tamarensis (NEPCC 255) was grown under nitrogen or phosphorus limitation. The major toxins found in P. tamarensis (255) consisted of (N21-SO ₃ ^- )STX (11%), (N21-SO ₃ ^- )NeoSTX (44%), and [(N21-SO ₃ ^- )GTX₂ plus (N21-SO ₃ ^- )GTX₃] (20%). Total toxin content on a per cell basis was high for cultures in log phase (30 to 40 fmol cell^-1) and then decreased to ca 20 fmol cell^-1 as the cultures entered stationary phase. There was a gradual decrease in the toxin content per cell during nitrogen-limited stationary phase to ca 3 fmol cell^-1 or less. Phosphorus-limited cultures showed a markedly different response than nitrogen-limited cultures. Toxin content in P-limited cells dramatically increased at the start of stationary phase, reaching levels 3 to 4 times that observed in control and nitrogen-limited cultures. These results cannot be explained by changes in the average cell volume. Eventhough dramatic effects on the total toxin concentration were observed in response to nutrient limitation (N or P), the toxin composition (on a percent basis) remained constant. This suggests that the individual toxin composition of a given isolate is a fixed genetic trait and not a transient response to changing environmental factors.     

Enzyme activities of fish skeletal muscle and brain as influenced by depth of occurrence and habits of feeding and locomotion

Activities of lactate dehydrogenase (LDH), pyruvate kinase (PK), malate dehydrogenase (MDH) and citrate synthase (CS) were measured in the white skeletal muscle of marine fishes having different depths of occurrence and different feeding and locomotory strategies. There were significant depth-related differences in the two glycolytic enzymes, LDH and PK. LDH activity was most variable, and differed by 3 orders of magnitude between the most active shallow-living species and certain deep-sea fishes likely to have only minimal capacities for active locomotion. Superimposed on the depth-related patterns was a high degree of interspecific variation (up to 20-fold) in enzymic activity among species from any given range of depth of occurrence. Variation of both LDH and PK activities, noted for shallow- and deep-living fishes, seems to be largely accounted for by differences in feeding habits and locomotory performance. Active pelagic swimmers have much higher activities of LDH and PK than, for example, deep-living sit-and-wait predators. Benthopelagic fishes like rattails and the sablefish have the highest activities found among deep-living fishes, suggesting that these species engage in relatively active food-searching behavior compared to most other deep-sea fishes. The activity of CS, an enzyme of the citric acid cycle and an indicator of aerobic metabolism, varied little among species. Thus, the large interspecific variation in glycolytic potential (LDH and PK) among species is not associated with a similar variation in aerobic metabolism of white muscle. The much higher and more variable activity of MDH relative to CS suggests that, in addition to its function in the citric acid cycle, MDH may play an important role in redox balance in fish white muscle. In a comparison of white muscle composition between the shallow- and deep-living species, water content did not differ significantly, but protein content was significantly higher in shallow- than in deep-living fishes (211 and 130 mg g^-1 wet wt of muscle, respectively). The differences in muscle protein content are small relative to the differences between shallow- and deep-living species in LDH, PK and MDH activities. Thus, depthrelated differences in muscle enzymic activity are caused by factors other than enzyme dilution. Enzyme activities (LDH, PK and CS) in brain tissue were relatively constant among species regardless of depth of occurrence or feeding and locomotory habits. Habitat and lifestyle do not seem to influence the demands for overall metabolic function in brain. The utility of muscle enzymic activity data for making predictions about the ecological characteristics of difficult-to-observe, deep-living, fishes is discussed.