Using a subaqueous soil‐landscape conceptual model previously developed in an adjacent subestuary, a subaqueous soil survey was undertaken for the South River subestuary of Chesapeake Bay. Using ...available bathymetry, subaqueous landforms and soil map units were delineated prior to the initiation of any field work. To evaluate the predictive usefulness of the conceptual model, the study area was subsequently sampled at 52 points along specified transects. The soils were described and classified, and the observed soils were compared to the predicted soils from the model using a bootstrapping analysis approach. We concluded that the conceptual model did provide significant positive guidance to generate a useful soil map in South River, by successfully predicting the distribution of soil material types. It did not, however, address the distribution of hypersulfidic materials prevalent in South River soils. The additional information gained on the soils and pedogenic processes gained during this study were incorporated into the final soil survey for the subestuary, and they were also used to refine the soil‐landscape conceptual model to improve its potential usefulness in future mapping of western shore subestuaries of Chesapeake Bay.
Core Ideas
The soil‐landscape paradigm beneficially applies to relatively shallow (less than 8 m) estuarine environments.
Subaqueous soil properties are associated with specific subaqueous landforms.
The conceptual model used to predict soil distribution in South River was effective.
Soil physical properties are superior to taxonomic groups as a basis for evaluating a soil‐landscape model.
Freshwater salinization is an emerging global problem impacting safe drinking water, ecosystem health and biodiversity, infrastructure corrosion, and food production. Freshwater salinization ...originates from diverse anthropogenic and geologic sources including road salts, human-accelerated weathering, sewage, urban construction, fertilizer, mine drainage, resource extraction, water softeners, saltwater intrusion, and evaporative concentration of ions due to hydrologic alterations and climate change. The complex interrelationships between salt ions and chemical, biological, and geologic parameters and consequences on the natural, social, and built environment are called Freshwater Salinization Syndrome (FSS). Here, we provide a comprehensive overview of salinization issues (past, present, and future), and we investigate drivers and solutions. We analyze the expanding global magnitude and scope of FSS including its discovery in humid regions, connections to human-accelerated weathering and mobilization of ‘chemical cocktails.’ We also present data illustrating: (1) increasing trends in salt ion concentrations in some of the world’s major freshwaters, including critical drinking water supplies; (2) decreasing trends in nutrient concentrations in rivers due to regulations but increasing trends in salinization, which have been due to lack of adequate management and regulations; (3) regional trends in atmospheric deposition of salt ions and storage of salt ions in soils and groundwater, and (4) applications of specific conductance as a proxy for tracking sources and concentrations of groups of elements in freshwaters. We prioritize FSS research needs related to better understanding: (1) effects of saltwater intrusion on ecosystem processes, (2) potential health risks from groundwater contamination of home wells, (3) potential risks to clean and safe drinking water sources, (4) economic and safety impacts of infrastructure corrosion, (5) alteration of biodiversity and ecosystem functions, and (6) application of high-frequency sensors in state-of-the art monitoring and management. We evaluate management solutions using a watershed approach spanning air, land, and water to explore variations in sources, fate and transport of different salt ions (
e.g.
monitoring of atmospheric deposition of ions, stormwater management, groundwater remediation, and managing road runoff). We also identify tradeoffs in management approaches such as unanticipated retention and release of chemical cocktails from urban stormwater management best management practices (BMPs) and unintended consequences of alternative deicers on water quality. Overall, we show that FSS has direct and indirect effects on mobilization of diverse chemical cocktails of ions, metals, nutrients, organics, and radionuclides in freshwaters with mounting impacts. Our comprehensive review suggests what could happen if FSS were not managed into the future and evaluates strategies for reducing increasing risks to clean and safe drinking water, human health, costly infrastructure, biodiversity, and critical ecosystem services.
In this study we conducted a sensitivity and uncertainty analysis using the Annual P Loss Estimator (APLE) model focusing on model predictions of soil test phosphorus (STP). We calculated and ...evaluated the sensitivity coefficients of predicted STP and changes in STP using 1‐ and 10‐yr simulations with and without P application. We also compared two methods for estimating prediction uncertainties: first‐order variance approximation (FOVA) and Monte Carlo simulation (MCS). Finally, we compared uncertainties in APLE‐predicted STP with uncertainties in measured STP collected from multiple sites in Maryland under different manuring and cropping treatments. Results from our sensitivity analysis showed that predicted STP and changes in STP for 1‐yr simulations without P inputs were most sensitive to initial STP, whereas model STP predictions were most sensitive to manure and fertilizer application rates when sensitivity analyses included P inputs. For the 10‐yr simulations without P application inputs, the range in sensitivity coefficients for crop uptake and precipitation were much greater than for the 1‐yr simulations. Prediction uncertainties from FOVA were comparable to those from MCS for model input uncertainties up to 50%. Using FOVA to calculate APLE STP prediction uncertainties using the Maryland data set, the mean measured STP for nearly all site years fell within the 95% confidence intervals of the STP prediction uncertainties. Our results provide users of APLE insight into what model inputs require the most careful measurement when using the model to predict changes in STP under conditions of P drawdown (i.e., no P application) or P buildup.
Core Ideas
Initial soil test phosporus (STP) is most important input in predicting STP when P application is not modeled.
Fertilizer and manure rates are most important inputs when predicting STP following P application.
First‐order variance approximation is an appropriate method to estimate prediction uncertainties in STP with APLE.
Prediction uncertainties generally overlap measured STP across treatments.
Regenerative stormwater conveyance (RSC), a relatively new stormwater management approach, is extensively implemented throughout the mid-Atlantic for nutrient control, but little is known of its ...pollutant reduction capabilities and controlling factors. This study examined effects of organic carbon (C) quantity and quality on stream water quality and nutrient retention at two RSCs near Annapolis, Maryland, USA by comparing longitudinal changes in water quality at paired restored and unrestored stream reaches, and conducting lab experiments simulating RSC processes. Results showed that RSCs consistently had lower dissolved oxygen saturation (DO%) and pH relative to nearby unrestored streams, probably due to release of labile dissolved organic carbon (DOC). At one RSC, with high nitrate (NO3−) inputs, retention of N (16–37%) and release of DOC (18–54%) were observed with the highest retention of N during summer, and the rates of N retention and DOC release were larger than that of the adjacent unrestored tributary (N: 5–8%, DOC: <18%). At another RSC site with lower NO3− concentrations, N retention and DOC release were not apparent. Mesocosm experiments showed that NO3− retention varies with organic C quantity and quality depending on incubating temperature; retention of total N did not increase with organic C due to release of other N species (e.g., organic N). Lab mesocosms showed an increase in the release of soluble reactive phosphorus (SRP) with increasing organic C quantity and quality. However, field measurements did not show any evidence of SRP release at RSCs. The changes in SRP concentrations in streams seemed to be a function of iron levels and leaf litter inputs, but control factors for SRP warrant further investigation. This study suggests that RSC as a restoration approach may be effective for reducing N depending upon C quantity and quality as well as water temperature and N levels.
Display omitted
•We examined effects of regenerative stormwater conveyances (RSCs) on water quality.•RSCs reduced dissolved oxygen and pH in stream surface and ground water.•RSCs retained nitrogen but retention varied with nitrogen concentration and seasons.•Nitrogen retention varied with organic carbon quantity and quality and temperature.•Release of soluble reactive phosphorus from RSCs warrants further investigation.
•RSCs implemented in degraded stream reaches create a series of step pools that can decrease stormflow velocities and nutrient and sediment loads.•Organic matter (OM) and iron (Fe)-rich substrates ...used in construction increase dissolved organic carbon (DOC) and Fe concentrations in stream water.•Some Fe in stream water is used by iron-oxidizing bacteria (FeOB) in the low-flow environments of RSCs to make Fe flocculate.•Fe flocculate generally does not have a large impact on stream habitat, but localized, dense mats sometimes occur that embed stream habitat.•Considering the quality and strategic use of Fe-rich substrates and prevalence of OM in RSCs will likely decrease the incidence of flocculate.
Regenerative streamwater conveyances (RSCs) are a relatively new stream restoration best management practice (BMP) being extensively implemented in degraded perennial streams and stormwater drainages throughout the mid-Atlantic. Although there is currently a great deal of interest in this type of BMP as a means of reducing nutrient and sediment export from disturbed catchments, little is known of its pollutant reduction capabilities and whether there are unintended ecological consequences associated with these structures. For example, dense accumulations of flocculate from iron-oxidizing bacteria (FeOB) have been observed at numerous RSC sites, yet it is unknown whether this flocculate is predominately natural, a consequence of leached iron (Fe) from the materials used in the RSC construction, or because of mobilized Fe from catchment soils influenced by higher groundwater levels that may occur after construction. We analyzed Fe and other solute concentrations in groundwater and perennial streams at RSC and control sites located in the Coastal Plain and Piedmont physiographic provinces of MD and DC, and conducted leaching experiments using RSC soils and construction materials. Iron flocculate from FeOB in RSCs is commonly localized and depends on several factors including a source of reduced Fe, the availability of dissolved organic carbon (DOC), and specific hydrological (i.e., low flow) and physical (i.e., warmer temperatures) conditions. Sources of reduced Fe are derived from both construction materials and catchment soils, which leach Fe in the presence of DOC originating from natural organic matter (OM) deposits and OM incorporated into the RSCs (i.e., wood chips, leaves, logs). Using construction materials that have relatively low Fe content in areas strongly influenced by OM will likely decrease the spatial and temporal presence of dense mats of Fe flocculate thereby improving stream habitat.
We review and contrast three frameworks for analyzing human-land interactions in the Holocene: the traditional concept of favored and disfavored landscapes, the new concept of ResourceCultures from ...researchers at University of Tübingen, and complex adaptive systems, which is a well-established contemporary approach in interdisciplinary research. Following a theoretical integration of fundamental concepts, we analyze three paired case studies involving modern agriculture in Germany and Belize, prehistorical changes in land use in southwest Germany, and aquaculture on the Pacific and Atlantic coasts of North America. We conclude that ResourceCultures and complex adaptive systems provide different but complementary strengths, but that both move beyond the favor-disfavor concept for providing a holistic, system-level approach to understanding human-land interactions. The three frameworks for understanding human responses to contemporary cultural and biophysical challenges are relevant to new thinking related to sustainability, resilience, and long-term environmental planning in the Anthropocene.
Factors driving freshwater salinization syndrome (FSS) influence the severity of impacts and chances for recovery. We hypothesize that spread of FSS across ecosystems is a function of interactions ...among five state factors: human activities, geology, flowpaths, climate, and time. (1) Human activities drive pulsed or chronic inputs of salt ions and mobilization of chemical contaminants. (2) Geology drives rates of erosion, weathering, ion exchange, and acidification‐alkalinization. (3) Flowpaths drive salinization and contaminant mobilization along hydrologic cycles. (4) Climate drives rising water temperatures, salt stress, and evaporative concentration of ions and saltwater intrusion. (5) Time influences consequences, thresholds, and potentials for ecosystem recovery. We hypothesize that state factors advance FSS in distinct stages, which eventually contribute to failures in systems‐level functions (supporting drinking water, crops, biodiversity, infrastructure, etc.). We present future research directions for protecting freshwaters at risk based on five state factors and stages from diagnosis to prognosis to cure.
A soil‐landscape conceptual model developed in the Rhode River subestuary of Maryland was applied to create a soil survey for the adjacent West River subestuary. The survey for the West River ...subestuary was completed before samples were collected there to evaluate the soil‐landscape conceptual model used to generate the soil survey. The West River subestuary was then sampled along transects that crossed soil map units to compare observed soil taxa with predicted soil taxa. Observed transect samples were classified and scored based on their similarity to predicted taxa in soil map units. These data were resampled via a bootstrapping method to determine if the predictions of the West River subestuary soil survey were significantly different from random predictions. Significant information was provided by the survey, and therefore by the soil‐landscape conceptual model used to generate it.
Core Ideas
Soil surveys can be statistically evaluated using bootstrapping statistical methods.
A polygon‐based soil survey can function as a testable hypothesis.
A soil‐landscape model developed in one setting can be evaluated in similar settings.
RhodeRiver, a subestuary on the western shore of Chesapeake Bay, contains a diverse array of subaqueous soils that range from submerged paleosols to fine‐textured fluid soils and organic soils. A ...subaqueous soil survey was completed for the Rhode River subestuary by collecting bathymetric data, delineating landforms, and sampling and describing soils across the submerged landscape. Soil map units were developed by correlating soil properties and taxonomic classification with delineated landforms, resulting in the development of seven proposed soil series corresponding to new soil map units. Geologic maps and other supporting information about the dominant factors of soil formation in this landscape were used with the soil survey of Rhode River to develop a conceptual subaqueous soil‐landscape model of soil genesis to explain the origin and distribution of soils in Rhode River. This is the first time that a subaqueous soil‐landscape model has been developed for the flooded river valley geomorphic setting of Chesapeake Bay, and it will assist subaqueous soil surveys in other western shore Chesapeake Bay subestuaries and similar environmental settings where upland environments have been or are currently submerging.
Core Ideas
Soil‐landscape conceptual models are used to guide U.S. soil surveys.
These models are rarely recorded and are lost over time after surveys are completed.
Subaqueous soil distribution in Rhode River is correlated with soil forming factors.
We propose a new soil‐landscape model to guide soil surveys in Chesapeake Bay.
The 8th International Acid Sulfate Soils Conference presented examples and discussions for classification of 'acid sulfate soils' and related issues for 'subaqueous soils'. When these soils are ...disturbed or exposed, the sulfides (predominantly pyrite) react with oxygen to produce sulfuric acid; soil materials that do this to a great extent are recognised as 'sulfidic materials' in Soil Taxonomy. Soil Taxonomy describes physical and chemical properties and thresholds for incubation of sulfidic materials for acidification, and has developed definitions for features and materials commonly seen in these soils. However, based on discussions and examples from field tours the conference has several proposals to modify and add to existing definitions, such as adding new subgroups, defining sulfuric materials and editing the definition of the sulfuric horizon. These changes are centred on improving the interpretative value of taxa in Soil Taxonomy as well as use and management recommendations and their value in soil survey products.
PDF
