Simulated upland placement of estuarine dredged materials

Placement of estuarine dredged materials on the land surface can result in severe environmental issues if acid sulfate conditions develop. In this study, upland placement of marine dredged material was simulated using a mesocosm experiment. Dredged materials were sampled from eight low energy and high energy subaqueous soil-landscape units of four estuaries in Rhode Island. Soils were mapped in the low energy landscape units (i.e. coves and bottoms) as Sulfiwassents and in the high energy units (i.e. deltas and fans) as Psammowassents. Dredged materials were characterized for various physical and chemical properties, placed into mesocosms, and exposed to natural climatic conditions outside. In addition, high energy and low energy materials were mixed at ratios of 20:1, 10:1, 5:1, and 2.5:1 and placed in mesocosms. Mesocosm leachate was collected and analyzed for pH, conductivity, and sulfate content for over 2 years (one year for the mixed mesocosms). Dredged materials ranged from sand to silt loam textures with the Sulfiwassents having finer textures and higher levels of carbon and calcium carbonates. Inorganic sulfide concentrations ranged from 56 to 3410 μg g− 1, with an average of 228 μg g− 1 for the Psammowassents and 2319 μg g− 1 for Sulfiwassents. Concentrations of Zn in the Sulfiwassent materials decreased by more than half after 2-years suggesting leaching of Zn during oxidation of the dredged materials. Leachate from low energy Sulfiwassents showed a large drop in pH (pH ≤ 4.0) associated with sulfide oxidation and creation of acid sulfate conditions, while leachate from coarser textured Psammowassents increased in pH to \u3e 8.0, presumably from the formation of salts. These conditions generally persisted for the duration of the experiment. Salts washed out of the dredged material fairly quickly such that leachate conductivities reached \u3c 5 dS m− 1 in 10 months. Sulfate content of the leachate varied for the first 18 months with the Sulfiwassent materials having higher levels and taking longer to wash out. Leachate from mixing as little as 5% Sulfiwassent with Psammowassent materials resulted in acid sulfate leachate (pH \u3c 4) in less than a year. Our results suggest that developing soil interpretations for upland placement of dredged materials of estuarine subaqueous soils should be focused on limitations as the result of creation of acid sulfate conditions and leaching of metals for Sulfiwassents and potentially high pH values for Psammowassents

Temporal Variability in the Vertical Separation Distance of Septic System Drainfields Along the Southern Rhode Island Coast

Many coastal communities rely on individual onsite wastewater treatment (i.e., septic) systems to treat and disperse wastewater. Proper wastewater treatment in these systems depends on sufficient volume of unsaturated soil below the drainfield’s infiltrative surface. This is governed by the vertical separation distance—the distance between the groundwater table and the drainfield infiltrative surface—which is specified in (regulatory jurisdictions’ onsite wastewater system) regulations. Groundwater tables along the southern New England coast are rising due to sea-level rise, as well as changes in precipitation and water use patterns, which may compromise the functioning of existing septic systems. We used long-term shallow groundwater monitoring wells and ground-penetrating radar surveys of 10 drainfields in the southern Rhode Island coastal zone to determine whether septic system drainfields have adequate separation distance from the water table. Our results indicate that only 20% of tested systems are not impaired by elevated groundwater tables, while 40% of systems experience compromised separation distance at least 50% of the time. Surprisingly, 30% of systems in this study do not meet separation distance requirements at any time of the year. Neither age of system nor a system’s geographical relationship to a tidal water body was correlated with compromised separation distance. The observed compromised separation distances may be a result of inaccurate methods, specified by the regulations, to determine the height of the seasonal high water table. Our preliminary results suggest that enacting changes in the regulatory permitting process for coastal zone systems may help protect coastal drinking and surface water resources

Insect and Hydroponic Farming in Africa: The New Circular Food Economy

Interestingly, some relief from today\u27s woes may come from ancient human practices. While current agri-food production models rely on abundant supplies of water, energy, and arable land and generate significant greenhouse gas emissions in addition to forest and biodiversity loss, past practices point toward more affordable and sustainable paths. Different forms of insect farming and soilless crop farming, or hydroponics, have existed for centuries. In this report the authors make a persuasive case that frontier agriculture, particularly insect and hydroponic farming, can complement conventional agriculture. Both technologies reuse society\u27s agricultural and organic industrial waste to produce nutritious food and animal feed without continuing to deplete the planet\u27s land and water resources, thereby converting the world\u27s wasteful linear food economy into a sustainable, circular food economy. As the report shows, insect and hydroponic farming can create jobs, diversify livelihoods, improve nutrition, and provide many other benefits in African and fragile, conflict-affected countries. Together with other investments in climate-smart agriculture, such as trees on farms, alternate wetting and drying rice systems, conservation agriculture, and sustainable livestock, these technologies are part of a promising menu of solutions that can help countries move their land, food, water, and agriculture systems toward greater sustainability and reduced emissions. This is a key consideration as the World Bank renews its commitment to support countries\u27 climate action plans. This book is the Bank\u27s first attempt to look at insect and hydroponic farming as possible solutions to the world\u27s climate and food and nutrition security crisis and may represent a new chapter in the Bank\u27s evolving efforts to help feed and sustain the planet