Biomedical subjects

John H Rodgers

Publications and source records attributed to John H Rodgers.

4 recordsLinked to original sources

PubMed2005

Evaluation of a constructed wetland treatment system specifically designed to decrease bioavailable copper in a wastestream.

A specifically designed constructed wetland decreased copper concentrations in a wastestream to 22 microg Cu/L and eliminated associated toxicity. Metal toxicity is a function of both concentration and form. This research measured copper partitioning to ligands within the wetland and observed changes in copper form with regard to bioavailability. Average monthly copper concentrations in the constructed wetland treatment system ranged from 10 to 47 microg/L in the upstream (i.e., inflow to the constructed wetland prior to the retention basin) and from non-detection to 11 microg/L in the downstream (i.e., outflow to the receiving stream). On average, 78% total-recoverable, 85% acid-soluble, and 83% soluble copper were removed from inflow to outflow of this constructed wetland; however, total recoverable and acid-soluble copper measurements were not useful indicators of bioavailable copper. Survival of Ceriodaphnia dubia increased from an average of 2% survival in the inflow to 96% in the outflow and reproduction increased from an average of 8 to 24 neonates/female, respectively. Soluble copper is a more accurate predictor of the concentration at which effects were observed. Average ratio of acid volatile sulfides to simultaneously extractable metals was 1.4: 0.06 micromol/g indicating sufficient sulfides to sequester available metals in the system.

Animals↗

PubMed2004

The responses of selected terrestrial plants to short (<12 days) and long term (2, 4 and 6 weeks) hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) exposure. Part I: Growth and developmental effects.

Soils contaminated with explosive materials like hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) is a concern nation-wide on military installations and sites where explosives are manufactured, stored, or disposed. Terrestrial plants are a vital group of receptor organism, yet limited published information is available on the potential impacts of RDX exposure in terrestrial plants. This research comprised the initial phases in the development of a short-term (<12 days) screening experiment for assessing the environmental impacts of RDX exposure in terrestrial plants. Fifteen plants (dicots and monocots) were exposed to three soils amended with 0-4000 microg g(-1) of RDX during the short-term screening experiments. Growth responses (maximum root and shoot lengths, percent emergence) and adverse developmental effects were the assessment endpoints. Sunflower was identified as the most RDX sensitive plant and selected for evaluation during the long-term (2, 4, and 6 weeks) experiments. Two life stages of sunflower (embryos and 2-week old seedlings) were exposed to Grenada soil amended with 0-100 microg g(-1) of RDX. The assessment endpoints during the long-term experiments included: biomass, maximum shoot and root length, root bio-volume, maximum stem diameter, number of leaves, and adverse developmental effects. Statistically significant differences were measured in several of the growth parameters following the short and long term exposure studies, however there were no consistent patterns. The consistent indicators of detrimental impacts from RDX exposure were the adverse developmental effects observed, regardless of life stage, soil type, or exposure duration. Typically, more adverse developmental effects were observed in dicots than monocots. The efficacy of the short-term screening experiments for estimating the impacts of long-term RDX exposure was validated.

Hazardous Waste↗

PubMed2003

Performance of a hybrid reverse osmosis-constructed wetland treatment system for brackish oil field produced water.

Using constructed wetlands, produced waters from oil fields (i.e., waters that have been in contact with oil in situ) can be treated to enhance water quality for irrigation purposes, or subsequent discharge to receiving aquatic systems. In produced water containing elevated levels of salt (i.e., brackish-produced waters), the ability to decrease the conductivity of the produced water may influence potential reuse of the water for irrigation purposes. The objectives of this research were (1) to determine the efficacy of a pilot-scale hybrid reverse osmosis (RO)-constructed wetland system for treatment and reuse of produced waters from an oil field, and (2) to assess the quality of treated water in terms of physicochemical characteristics and toxicity influencing reuse of the water for irrigation or other designated uses. Specifically, the performance of the hybrid treatment system was examined in terms of outflow water conductivity, total dissolved solids (TDS), and toxicity using Ceriodaphnia dubia and Pimephales promelas in 7-day static/renewal exposure tests. Prior to treatment, significant mortality was observed for C. dubia and P. promelas exposed for 7 days to 6.25% untreated produced water. Following treatment through the hybrid system, no significant mortality was observed in C. dubia or P. promelas exposed to 100% treated produced water when compared to the control organisms. The pilot-scale RO-constructed wetland system effectively decreased conductivity by 95% and TDS by 94% in the brackish produced water tested in this study. Following treatment, the produced water was suitable for irrigation or discharge to surface waters. Therefore, hybrid RO-constructed wetland treatment systems present a viable alternative for treatment and reuse of produced waters from oil fields.

Agriculture↗

PubMed2002

Ecological effects of an anionic C12-15 AE-3S alkylethoxysulfate surfactant in outdoor stream mesocosms.

The ecological assessment of a C12-15 AE-3S linear alkylethoxysulfate (AES) anionic surfactant to invertebrates, fish, periphyton, and an aquatic macrophyte was conducted in a 30-d outdoor stream mesocosm study with five replicated concentrations and controls. Alkylethoxysulfate structural integrity and exposure concentrations were maintained during the 30-d treatment period, with average measured concentrations of 0.7, 1.27, 2.2, 4.31, and 10.18 mg/L. No effects were observed on the aquatic macrophyte Myriophyllum aquaticum at the highest concentration tested. A sevenfold increase in periphyton biomass at 10.18 mg/L was observed relative to controls primarily because of increases in density of the filamentous alga Mougeotia sp. Densities of the invertebrates Annelida (Stylaria), Amphipoda, Copepoda, Trichoptera (Hydropsychidae), Cladocera, and Diptera (Chironomidae) significantly decreased in streams treated with AES at 10.18 mg/L. Densities of drifting invertebrates were not observed to be affected at any concentration tested. Reproduction of Pimephales promelas significantly decreased at 1.27 mg/L and growth of juvenile Lepomis macrochirus was significantly affected at 4.31 mg/L. Multivariate cluster analysis and nonmetric multidimensional scaling ordination showed distinct structural effects on the invertebrate communities in the streams treated with AES at 10.18 mg/ L compared to the control and streams treated at < 10.18 mg/L through the 30-d treatment. Convergence of the communities treated at 10.18 mg/L toward control communities in the ordination suggests recovery in these communities after termination of surfactant treatment. The results from this study support an ecosystem value of > 2.0 mg/L, and indicate that the conservative Dutch risk assessment for AESs has at least a fivefold margin of safety.

Animals↗