Daryl F. Dwyer

Effects of Light Regime, Temperature, and Plant Age on Uptake of Arsenic by Spartina Pectinata and Carex Stricta

We report here on efforts to show that a combination of native wetland plant species might perform better than a monoculture in wetlands designed for arsenic remediation by supplementing weaknesses. Carex stricta and Spartina pectinata were used in hydroponic experiments. (i) Arsenic uptake was first assessed at two ages via exposure to control or arsenic-laden solutions (0 or 1.5 mg As L−1 as Na2HAsO4) for two weeks. Age had no significant effect on arsenic concentrations in roots, but translocation factors were greater in older plants of C. stricta and S. pectinata (0.45 and 0.07, respectively) than in younger plants (0.10 and 0.01, respectively). (ii) Seasonal effects were assessed by determining uptake kinetics for both species in conditions representative of spring temperatures (15/5°C) and light regimes (1050 μmol m−2 s−1, 13 h day−1) and summer temperatures (28/17°C) and light regimes (1300 μmol m−2 s−1, 15 h day−1). Both species had comparable rates of arsenic uptake into roots in summer conditions (44.0 and 46.5 mg As kg−1 dry wt. h−1 in C. stricta and S. pectinata, respectively), but C. stricta had a higher maximum net influx rate in spring conditions (24.5 versus 10.4 mg As kg−1 dry wt. h−1).

Increasing Beach Recreation Benefits by Using Wetlands to Reduce Contamination

Abstract The public swimming beach at Maumee Bay State Park (MBSP) on Lake Erie is often posted for occurrences of unsafe levels of bacteria. The main source of bacteria derives from a drainage ditch that discharges near the beach. We have conducted a comprehensive study to determine the feasibility of using a constructed wetland to filter the ditch water, prior to its entry into Maumee Bay. As part of this study, we administered an on-site non-market valuation survey of beach visitors, in which observed and contingent trips to the beach were used to estimate the potential welfare benefits of the restored wetlands. The data were analyzed using three versions of the multivariate Poisson-lognormal (MPLN) model, a random effects count data model. We conclude version one, with flexible covariance structure and vehicle costs of

Assessing the Performance of Evapotranspiration Covers for Municipal Solid Waste Landfills in Northwestern Ohio

0.25 per mile, is the preferred version and use it to estimate an average annual willingness to pay (WTP) of

Analysis of Arsenic Uptake by Plant Species Selected for Growth in Northwest Ohio by Inductively Coupled Plasma–Optical Emission Spectroscopy

166 to construct wetlands and improve water quality. The aggregate annual benefit to an estimated 37,300 annual beach visitors is estimated as

Uptake and Toxicity of Arsenic, Copper, and Silicon in Azolla caroliniana and Lemna minor

6.19 million. The robustness of this estimate to a variety of alternative assumptions is examined. JEL Classification Code: Q51

Two-year performance by evapotranspiration covers for municipal solid waste landfills in northwest Ohio

Evapotranspiration (ET) covers have gained considerable interest as an alternative to conventional covers for the final closure of municipal solid waste (MSW) landfills, but often produce higher rates of percolation in regions that receive more than 32 cmyear � 1 of precipitation. The goal of this project is to design ET covers for MSW landfills in northwestern Ohio (long-term annual rate of precipitation of 83 cmyear � 1 ) that produce rates of percolation < 32 cmyear � 1 , the rate considered acceptable by the Ohio Environmental Protection Agency (OEPA), and promote habitat restoration. To attain this goal, an adequate soil water-storage capacity was provided using dredged sediment amended with organic material. Two plant mixtures were tested to evaluate the performance of ET covers immediately following construction (immature plants seeded onto the soil) and in the future (mature plants transplanted from a restored tall-grass prairie that is more than 10 years old). ET covers were constructed in drainage lysimeters (1.52-m diameter, 1.52-m depth) and watered at a rate of 91.12 to 95:72 cmyear � 1 , which included simulated 100-year rain events (11.7 cm over 24 h) in July and October. During the 1-year monitoring period, the ET covers using the mature plant mixture produced considerably less percolation (0.12 to 11:44 cmyear � 1 ) than the covers with the immature plant mixture (6.71 to 24:16 cmyear � 1 ). Thus far, all ET covers have produced rates of percolation less than the maximum standard by the OEPA, and they will continue to be monitored. DOI: 10.1061/(ASCE)EE.1943-7870.0000326.

Irrigation of Three Wetland Species and a Hyperaccumlating Fern with Arsenic-Laden Solutions: Observations of Growth, Arsenic Uptake, Nutrient Status, and Chlorophyll Content

Abstract Arsenic (As) contamination is widespread in the industrial areas of northwest Ohio. Plant species that both take up As and are appropriate for the climate and growth conditions of the region are needed for phytoremediation to be successfully employed. Actively growing plants from 22 species of native genera were exposed to As in hydroponics systems (either 0, 10, or 50 mg As L−1; 1 week) and commercially available potting mix (either 0, 10, 25, 100, or 250 mg As L−1; 2 weeks), depending on their growth conditions. Aboveground plant tissues were harvested and digested, and concentrations of As were determined by inductively coupled plasma–optical emission spectrometry. The highest tissue concentrations of As (mg As kg−1 dw) were recorded in seven plant species: Rudbeckia hirta (661), Helenium autumnale (363 in tissues formed after exposure to As), Lupinus perennis (333), Echinacea purpurea (298), Coreopsis lanceolata (258), Lepidium virginicum (214), and Linum lewisii (214). These seven species are ecologically diverse, which suggests that phytoremediation of As using diverse assemblages of plants may be an option for a variety of environments.

Three reasons to use annual payments in contingent valuation surveys: Convergent validity, discount rates, and mental accounting☆

Here we report on the analysis of two aquatic plant species, Azolla caroliniana and Lemna minor, with respect to tolerance and uptake of co-occurring arsenic, copper, and silicon for use in engineered wetlands. Plants were cultured in nutrient solution that was amended with arsenic (0 or 20 μM), copper (2 or 78 μM), and silicon (0 or 1.8 mM) either singly or in combination. We hypothesized that arsenic and copper would negatively affect the uptake of metals, growth, and pigmentation and that silicon would mitigate those stresses. Tolerance was assessed by measuring growth of biomass and concentrations of chlorophyll and anthocyanins. Both plant species accumulated arsenic, copper, and silicon; L. minor generally had higher levels on a per biomass basis. Arsenic negatively impacted A. caroliniana, causing a 30% decrease in biomass production and an increase in the concentration of anthocyanin. Copper negatively impacted L. minor, causing a 60% decrease in biomass production and a 45% decrease in chlorophyll content. Silicon augmented the impact of arsenic on biomass production in A. caroliniana but mitigated the effect of copper on L. minor. Our results suggest that mixtures of plant species may be needed to maximize uptake of multiple contaminants in engineered wetlands.

A spatial, multivariable approach for identifying proximate sources of Escherichia coli to Maumee Bay, Lake Erie, Ohio

Evapotranspiration (ET) covers have gained interest as an alternative to conventional covers for the closure of municipal solid waste (MSW) landfills because they are less costly to construct and are expected to have a longer service life. Whereas ET covers have gained acceptance in arid and semi-arid regions (defined by a precipitation (P) to potential evapotranspiration (PET) ratio less than 0.75) by meeting performance standards (e.g. rate of percolation), it remains unclear whether they are suitable for humid regions (P:PET greater than 0.75). The goal of this project is to extend their application to northwest Ohio (P:PET equals 1.29) by designing covers that produce a rate of percolation less than 32 cm yr(-1), the maximum acceptable rate by the Ohio Environmental Protection Agency (OEPA). Test ET covers were constructed in drainage lysimeters (1.52 m diameter, 1.52 m depth) using dredged sediment amended with organic material and consisted of immature (I, plants seeded onto soil) or mature (M, plants transferred from a restored tall-grass prairie) plant mixtures. The water balance for the ET covers was monitored from June 2009 to June 2011, which included measured precipitation and percolation, and estimated soil water storage and evapotranspiration. Precipitation was applied at a rate of 94 cm yr(-1) in the first year and at rate of 69 cm yr(-1) in the second year. During the first year, covers with the M plant mixture produced noticeably less percolation (4 cm) than covers with the I plant mixture (17 cm). However, during the second year, covers with the M plant mixture produced considerably more percolation (10 cm) than covers with the I plant mixture (3 cm). This is likely due to a decrease in the aboveground biomass for the M plant mixture from year 1 (1008 g m(-2)) to year 2 (794 g m(-2)) and an increase for the I plant mixture from year 1 (644 g m(-2)) to year 2 (1314 gm(-2)). Over the 2-year period, the mean annual rates of percolation for the covers with the M and I plant mixtures were 7 and 8 cm yr(-1), which are below the OEPA standard. The results suggest the application of ET covers be extended to northwest Ohio and other humid regions.

Vascular Flora of the King Road Landfill in Northwest Ohio

Engineered wetlands can be an integral part of a treatment strategy for remediating arsenic-contaminated wastewater, wherein, As is removed by adsorption to soil particles, chemical transformation, precipitation, or accumulation by plants. The remediation process could be optimized by choosing plant species that take up As throughout the seasonal growing period. This report details experiments that utilize wetland plant species native to Ohio (Carex stricta, Pycnanthemum virginianum, and Spartina pectinata) that exhibit seasonally related maximal growth rates, plus one hyperaccumulating fern (Pteris vittata) that was used to compare arsenic tolerance. All plants were irrigated with control or As-laden nutrient solutions (either 0, 1.5, or 25 mg As L−1) for 52 d. Biomass, nutrient content, and chlorophyll content were compared between plants treated and control plants (n = 5). At the higher concentration of arsenic (25 mg L−1), plant biomass, leaf area, and total chlorophyll were all lower than values in control plants. A tolerance index, based on total plant biomass at the end of the experiment, indicated C. stricta (0.99) and S. pectinata (0.84) were more tolerant than the other plant species when irrigated with 1.5 mg As L−1. These plant species can be considered as candidates for engineered wetlands.