Optimization and Decision Heuristics for Chesapeake Bay Nutrient Reduction Strategies

Regional policies to achieve water quality goals assign a unique pollution control technology to every pollution source in a watershed, thereby defining a watershed strategy. For watersheds with even a modest number of pollution sources and control alternatives, the decision problem has combinatorial complexity. The perception of complexity—manifested in innumerable feasible watershed strategies—commonly induces the use of simplifying decision heuristics and ad hoc decision rules that reduce decision complexity by limiting the choice set to a “manageable” number of alternatives. In problems with large complex choice sets, these decision heuristics simplify decision making by excluding the vast majority of feasible alternatives a priori. In contrast, watershed-scale optimization enables decision makers to consider all feasible alternatives implicitly, exploiting rather than restricting the complexity of the feasible choice set. This contrast is illustrated using mixed-integer linear programming to identify interstate watershed strategies that achieve Chesapeake Bay nutrient reduction goals for the Potomac River Basin. The use of optimization in collaborative decision making helped refine and capture decision makers’ underlying values and preferences in policy-relevant constraints reflecting equity and political feasibility. Optimization formulations incorporating these constraints identified more effective and desirable management alternatives that would not otherwise have been considered using familiar decision heuristics and traditional comparisons among a limited number of ad hoc scenarios. Incorporating optimization in collaborative decision making generated superior watershed strategies and eased the cognitive limitations on decision making by substituting the computational burden of solving mixed-integer linear programs for decision makers’ cognitive burden of enumerating alternatives and scenarios for environmental systems with combinatorial complexity.     

Physico-chemical changes in metal-spiked sediments deployed in the field: implications for the interpretation of in situ studies

Manipulative field studies are useful for investigating cause-effect relationships between contamination and benthic community health. However, there are many challenges for creating environmentally relevant exposures and determining what measurements are necessary to correctly interpret the results. This study describes the physical and chemical changes in the properties of metal-spiked marine sediments deployed in four different locations for up to 11 months. The test sediments lost between 20% and 75% of their volume during the deployment period, with the greatest losses occurring at sites affected by strong hydrodynamic activity. More sediment was lost from clean treatments than those spiked with high metal concentrations and corresponded with differential recruitment of infauna to these treatments. In general, a greater proportion of spiked-metals remained at lower energy sites (48-85%) than at higher energy sites (15-48%). The decreased metal concentrations were attributed mostly to the loss of the metal-spiked sediments (through resuspension) and their dilution with sediments depositing from the surrounding environment. A range of recommendations are made for optimising the information gained from field-based studies using metal-spiked sediments. These include the careful documentation of physico-chemical sediment properties pre- and post-deployment, the use of co-located sediment traps and knowledge of site-specific hydrodynamic processes.     

Salting our landscape: an integrated catchment model using readily accessible data to assess emerging road salt contamination to streams

A new integrated catchment model for salinity has been developed to assess the transport of road salt from upland areas in watersheds to streams using readily accessible landscape, hydrologic, and meteorological data together with reported salt applications. We used Fishkill Creek (NY) as a representative watershed to test the model. Results showed good agreement between modeled and measured stream water chloride concentrations. These results suggest that a dominant mode of catchment simulation that does not entail complex deterministic modeling is an appropriate method to model salinization and to assess effects of future applications of road salt to streams. We heuristically increased and decreased salt applications by 100% and results showed that stream chloride concentrations increased by 13% and decreased by 7%, respectively. The model suggests that future management of salt application can reduce environmental concentrations, albeit over some time.     

Constrained Choice and Ethical Dilemmas in Land Management: Environmental Quality and Food Safety in California Agriculture

As environmental and conservation efforts increasingly turn towards agricultural landscapes, it is important to understand how land management decisions are made by agricultural producers. While previous studies have explored producer decision-making, many fail to recognize the importance of external structural influences. This paper uses a case study to explore how consolidated markets and increasing corporate power in the food system can constrain producer choice and create ethical dilemmas over land management. Crop growers in the Central Coast region of California face conflicting demands regarding environmental quality and industry imposed food safety standards. A mail survey and personal interviews were used to explore growers’ perceptions and actions regarding these demands. Results indicate that in many cases growers face serious ethical dilemmas and feel pressured by large processing and retail firms to adopt measures they find environmentally destructive and unethical. Future strategies to address environmental issues on agricultural landscapes should consider the economic constraints producers face and the role of large firms in creating production standards.     

Sorption of trihalomethanes in foods

Trihalomethanes (THMs, namely, CHCl₃, CHCl₂Br, CHClBr₂ and CHBr₃) are disinfection by-products that are present in drinking water. These toxic chemicals are also present in meat, dairy products, vegetables, baked goods, beverages and other foods, although information regarding their concentrations and origin is very limited. This study investigates sorption of THMs occurring during rinsing and cooking of foods and the significance of food as an exposure source.Initial estimates of THM uptake were measured in experiments representing rinsing with tap water at 25 C using nine types of food, and for cooking in tap water at 90 C for fourteen other foods. A subset of foods was then selected for further study over a range of THM concentrations (23.7–118.7 μg/l), temperatures (25 C and 90 C), food concentrations (0.2–1.4, food weight: water weight), and contact times (5–240 min). Data were analyzed using regression and exponential models, and diffusion models were used to help explain the trends of THM uptake.Among vegetables, sorbed THM concentrations at 25 C were 213 to 774 ng/g for CHCl₃, 53 to 609 ng/g for CHCl₂Br, and 150–845 ng/g for CHClBr₂. Meats at 90 C tended to have higher concentrations, e.g., 870–2634 ng/g for CHCl₃. Sorbed concentrations increased with contact time and THM concentration, and decreased with food concentration in rinsing tests (using spinach, iceberg-head lettuce and cauliflower) and cooking tests (using tomato, potato, beef and miso–tofu soup). For most foods, THM uptake was diffusion limited and several hours were needed to approach steady-state levels. Swelling, hydrolysis and other physical and chemical changes in the food can significantly affect sorption. Screening level estimates for CHCl₃ exposures, based on experimental results and typical food consumption patterns, show that uptake via foods can dominate that due to direct tap water consumption, suggesting the importance of sorption and the need for further evaluation of THM intake due to foods.     

Embracing sustainability: the incorporation of sustainability principles in municipal planning and policy in four mid-sized municipalities in Ontario,Canada

The issue of planning for sustainability is becoming more established within Canadian municipal planning. As municipalities begin to align their planning policy to reflect a more sustainable approach, there is an increased interest in how sustainability is being operationalised within municipal documents. This research aims to better understand how principles of sustainability are imbedded within Ontario municipal documents, with a specific focus on the Integrated Sustainability Community Planning approach that has emerged in Canada. Drawing on a nested comparative case study of four mid-sized municipalities, we uncover the language and strategies employed by the municipalities as they relate to the principles of sustainability developed by Gibson [2006a. Sustainability assessment: basic components of a practical approach. Impact Assessment and Project Appraisal, 24 (3), 170–182]. The findings suggest that current policy-based approaches to sustainability are considering more socially oriented strategies focused on promoting community involvement, inclusive decision-making, equity, socio-ecological civility, long-term integrative planning, and responsibility through stewardship. However, there are potential limitations that will require future research to examine policy outcomes associated with sustainability uptake. The ICSP approach must still overcome the issues relating to lack of regulatory authority and the incorporation of policies based on popular trends rather than empirical evidence.     

Long-term copper partitioning of metal-spiked sediments used in outdoor mesocosms

Understanding the effects of sediment contaminants is pivotal to reducing their impact in aquatic environments. Outdoor mesocosms enable us to decipher the effects of these contaminants in environmentally realistic scenarios, providing a valuable link between laboratory and field experiments. However, because of their scale, mesocosm experiments are often complex to set up and manage. The creation of environmentally realistic conditions, particularly when using artificially contaminated sediment, is one issue. Here, we describe changes in geochemistry over 1.5 years of a sediment spiked with four different concentrations of copper, within a large freshwater mesocosm facility. The spiking procedure included proportional amendments with garden lime to counteract the decreases in pH caused by the copper additions. The majority of copper within the spiked mesocosm sediments partitioned to the particulate phase with low microgram per liter concentrations measured in the pore waters and overlying waters. The minimum partition coefficient following equilibration between pore waters and sediments was 1.5?×?10⁴ L/kg, which is well within the range observed for field-contaminated sediments (1?×?10⁴ to 1?×?10⁶ L/kg). Recommendations are made for the in situ spiking of sediments with metals in large outdoor mesocosms. These include selecting an appropriate sediment type, adjusting the pH, allowing sufficient equilibration time, and regular mixing and monitoring of metal partitioning throughout the experimental period.     

Challenges with tracing the fate and speciation of mine-derived metals in turbid river systems: implications for bioavailability

The fast-flowing and highly turbid Lagaip River (0.5–10 g/L suspended solids) in the central highlands of Papua New Guinea receives mine-derived metal inputs in both dissolved and particulate forms. Nearest the mine, metal concentrations in suspended solids were 360, 9, 90, 740 and 1,300 mg/kg for As, Cd, Cu, Pb and Zn, while dissolved concentrations were 2.7, 0.6, 3.1, 0.1 and 25 μg/L, respectively. This creates a significant metal exposure source for organisms nearer the mine. However, because the Lagaip River is diluted by a large number of tributaries, the extent to which mine-derived metals may affect biota in the lower catchments is uncertain. To improve our understanding of the forms of potentially bioavailable metals entering the lower river system, we studied the partitioning and speciation of metals within the Lagaip River system. Dissolved and particulate metal concentrations decreased rapidly downstream of the mine due to dilution from tributaries. As a portion of the particulate metal concentrations, the more labile dilute acid-extractable forms typically comprised 10–30 % for As and Pb, 50–75 % for Cu and Zn, and 50–100 % for Cd. Only dissolved Cd, Cu and Zn remained elevated relative to the non-mine-impacted tributaries (<0.03, 0.5 and 0.3 μg/L), but the concentrations did not appreciably change with increasing dilution downriver. This indicated that release of Cd, Cu and Zn was likely occurring from the more labile metal phases of the mine-derived particulates. Chelex-labile metal analyses and speciation modelling indicated that dissolved copper and lead were largely non-labile and likely complexed by naturally occurring organic ligands, while dissolved cadmium and zinc were predominantly present in labile forms. The study confirmed that mine-derived particulates may represent a significant source of dissolved metals in the lower river system; however, comparison with water quality guidelines indicates the low concentrations would not adversely affect aquatic life.