A Quantitative Review of Irrigation Development in the Yazoo–Mississippi Delta from 1991 to 2020

The Yazoo–Mississippi Delta is one of the regions within the Lower Mississippi River Basin where substantial irrigation development and consequent groundwater depletion have occurred over the past three decades. To describe this irrigation development, a study was conducted to analyze existing geospatial datasets and to synthesize the results with those of past government surveys. The effort produced a quantitative review characterizing three aspects of irrigation development from 1991 to 2020. First, the expansion of irrigated area was tracked in terms of absolute area and in terms of fraction relative to total land or cropland area. Second, trends in irrigated land cover were traced in terms of irrigated crop mix, irrigated fractions of main crops, and comparisons with non-irrigated land. Third, changes in irrigation systems were examined in terms of water sources, energy sources, and application methods. Original findings of this study for the end of 2020 included moderate positive spatial autocorrelation in the density of irrigated areas; a higher irrigated crop preference for soybean and rice over cotton and corn in highly hydric soils; and 91% and 3% of permitted areas studied being respectively under groundwater withdrawal permits exclusively and under surface water diversion permits exclusively. By compiling such information, this paper can serve as a convenient reference on the recent history and status of irrigation development in the Yazoo–Mississippi Delta.

Mercury Distribution in an Upper St. Lawrence River Wetland Dominated by Cattail (Typha Angustifolia)

Legacy mercury (Hg) exists in Upper St. Lawrence River wetland hydric soils and is impacted by a new water level management plan (established in 2017) implemented to restore biodiversity and reduce the monotypic nature of riparian wetlands, currently dominated by Typha spp.. The distribution of Hg within the various components of a riparian wetland provides insight into potential impacts of water level fluctuations. Hydric soil represents 83% of the wetland Hg burden while wetland plant biomass contributed 17%, mostly due to organic detritus (13%). Although Typha roots had a bioconcentration factor of 1.2 (relative to hydric soils) and had the highest total Hg among living tissues (25 ± 9.3 ng/g dry wt.), detritus had the highest overall Hg content (110 ± 53 ng/g dry wt.). While root tissue Hg correlated significantly with soil Hg (p = 0.045), it was determined here that Typha spp. has limited use as a biomonitor in wetlands with low levels of Hg contamination, as in this ecosystem. Hg contained within the organic detritus contributed more to the overall Hg burden in these monotypic Typha wetlands than any other tissue or biomass component analyzed. Consequently, shifts in the plant community that are expected to result from a new water level management plan may alter Hg storage within these wetlands and affect its mobility in this ecosystem.

Characterizing Groundwater Interaction with Lakes and Wetlands Using GIS Modeling and Natural Water Quality Measurements

Wetlands provide many benefits, including flood attenuation, groundwater recharge, water-quality improvement, and habitat for wildlife. As their structure and functions are sensitive to changes in hydrology, characterizing the water budgets of wetlands is crucial to effective management and conservation. The groundwater component of a budget, which often controls resiliency and water quality, is difficult to estimate and can be costly, time-consuming, and invasive. This study used a GIS approach using a digital elevation model (DEM) and the elevations of lakes, wetlands, streams, and hydric soils to produce a water-table surface raster for a portion of the Itasca Moraine, Minnesota, U.S. The water-table surface was used to delineate groundwatersheds and groundwater flow paths for lakes and wetlands, and map recharge and discharge rates across the landscape. Specific conductance and pH, which depend on the hydrological processes that dominate a wetlands water budget, were measured in the field to verify this modeling technique. While the pH of surface waters varied in the study area, specific conductance increased from 16.7 to 357.5 μS/cm downgradient along groundwater flow paths, suggesting increased groundwater interaction. Our results indicate that basic GIS tools and often freely available public-domain elevation datasets can be used to map and characterize the interaction of groundwater in the water budgets of lakes and wetlands, as exemplified by the Itasca Moraine region. Combining this with grid cell-by-cell water balance provides a means to estimate recharge and discharge, thereby affording a way to quantify groundwater contribution to and from lakes and wetlands. Applied elsewhere, this cost-efficient technique can be used to assess the vulnerability of lakes and wetlands to changes in land use, groundwater development, and climate change.

Delineation of soil drainage class by electromagnetically measurements of soil magnetic susceptibility

<p>Soil has the most important role in agriculture. For instance, it prevents run off and also through its capacity for storing water, it acts as a water reservoir and provide water resources for plant roots. Water retention characteristics, nutrient holding capacities and solute transport of soil can affect its productivity. So, the plant growth is directly associated with the type of soil drainage. The prediction of soil drainage classes is one of the major steps in developing crop modelling. Among different physical and chemical soil health indicators, soil magnetic susceptibility (MS) is a promising factor for soil surveying because it is strongly affected by soil drainage class. The extremely reducing conditions, present in hydric soils, significantly enhance dissolution of soil ferrimagnetic minerals such as magnetite and maghemite. Since the MS of soils is mainly controlled by magnetite and maghemite concentrations, therefore MS values are typically very low in hydric, i.e. poorly drained or gleyed, soils.</p><p>The common method for measuring soil MS is utilizing handheld or laboratory MS meters (e.g. Bartington MS2 sensors). Such MS meters are required soil specimen to be available to directly measure MS of that specimen. So, their application is limited to surface soils, soil exposures and sampled soils. Other types of instruments for quickly measuring soil properties are electromagnetic induction (EMI) instruments. Although the EMI instruments were primarily invented to measure electrical conductivity (EC) of the topsoil for assessment of soil salinity, they can also be utilized to measure absolute value of the volume MS of the topsoil. These volume MS values can be further processed and inverted to reveal MS variations of soil layers.</p><p>In this study, 1-D inversion of volume MS data, measured by Geonics EM38 instrument in both vertical and horizontal magnetic dipole configurations, was done to calculate MS of selected soil profiles in order to delineate soil drainage classes. Besides, laboratory measurements of volume and mass-specific MS of soil core samples, collected in the same soil profiles, were done using Bartington MS2B and MS2C sensors. Results show a strong and positive relationship between MS values measured in the laboratory and volume MS recovered from inversion technique. Furthermore, the results reveal that MS in a well drained profile is higher than that of a poorly drained profile. Since EMI measurements of soil MS are done quickly in the field, then using surface MS measurements facilitates hydric soil delineation in a faster and more precise way.</p>

Evaluating the use of iron-coated tubes for wetland delineation in South Africa: A pilot study in the Kruger National Park

The identification of hydric soils is important for wetland delineation and protection. South Africa currently uses the Department of Water Affairs and Forestry (DWAF) wetland delineation guidelines which can be subjective in certain contexts. A robust technical standard that can be legally conclusive is therefore required and should be developed for South African conditions. The National Technical Committee of Hydric Soils (NTCHS, 2007) in the United States of America has accepted the Indicator of Reduction in Soils (IRIS) tube methodology as a technical standard, but this had not yet been tested in South Africa. It is proposed that the NTCHS (2007) be adapted for use in South Africa. These Fe-coated tubes are installed into the soil and if reducing conditions are present, the Fe coating is removed. The aim of this study was to evaluate the use of IRIS tubes as a technical standard for wetland delineation in South Africa. The study took place in three different wetland systems (Malahlapanga, Nshawu and the Tshuthsi spruit) in the Kruger National Park. Piezometers were installed in triplicate in each zone, and the water table, pH and Eh were recorded monthly. Soils were classified, soil wetness indicators identified, and vegetation described. The study took place from September 2012 to August 2013. The areal percentage of paint removed from the top 300 mm of the IRIS tubes was quantified by scanning the tubes and then compared to the DWAF wetland indicators. It was found that the DWAF indicators and the IRIS tube method were mostly in agreement; however, the conditions at the Tshutshi spruit were not favourable for Fe reduction, and hence the use of IRIS tubes, due to the high pH values recorded. The IRIS tubes were therefore a useful tool for wetland delineation in the majority of conditions, but are not recommended in high pH, sodic environments. Further research is recommended over a wider geographical area as well as testing the MIRIS methodology (Manganese Indicators of Reduction in Soils) in wetlands that would inhibit Fe reduction.

Density separation of soils as sample preparation for the determination of plastics

<p>Plastics are found ubiquitously in all environmental media. Evidence of microplastic occurrence was also provided for various biota. At the beginning of the scientific debate, the oceans as final plastics sinks were in the foreground, whereas current research work focuses on the sources of input, including<br>surface waters. The water content of these surface waters are influenced by urban and rural areas, including the adjoining soils.<br>Like oceans, soils are a final sink for many substances, including plastics. Sources of plastics are diverse and depend on use and management. With respect to analytics, soil material is much more complex than suspended solids in water. Therefore the type of soil, grain size, the organic content as well as containing metal ions are important parameters.<br>For the detection of plastics, there are different analytical methods. Spectroscopic methods determine the particle numbers, sizes, and shapes. Pyrolytic methods return the total contents of plastics within the sample. These include the Thermo-Extraction-Desorption-Gas-Chromatography-MassSpectrometry (TED-GC-MS).<br>In many environmental samples, there are substances that interfere with both the sample detection and sample preparation. Thus, mineral components must be removed in order to be able to grind better. For their removal, density separation is suitable. In this article, experiments with density separation will be presented.<br>There are different options to prepare solid samples with density separation, including major methodological differences in the selection of the separation solution and the phase separation.<br>Various plastic spiked solid samples (terrestrial and sub hydric soils) were biologized. Subsequently, recovery tests were carried out using a density separation method with different separation solutions.<br>Ultrasound was used to destroy soil agglomerates and release occluded plastics. The separated floated material was sucked off through a 6 μm stainless steel filter. The plastic content in the rinsed organic material was quantified with a TED-GC-MS analysis.<br>The presented method shows medium (PE: 47 – 82 %) to high (PS: 89 – 100 %) recovery rates depending on the separation solution used and the environmental sample examined.</p>