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Environmental Fate Models, with Emphasis on Those Applicable to Air
Published in James N. Seiber, Thomas M. Cahill, Pesticides, Organic Contaminants, and Pathogens in Air, 2022
James N. Seiber, Thomas M. Cahill
Empirical laboratory/field models can be divided into microcosms and mesocosms. A microcosm is typically enclosed in a laboratory chamber system (glass, Teflon®) that is constructed to simulate natural systems on a reduced scale, for measuring responses to varying conditions (e.g., moisture, nutrients, sunlight, and temperature) over time. When a chemical, or a mixture, is placed in the chamber, one can measure the water, air, plant, and animal concentrations of radio labelled precursors under different sets of conditions to obtain approximations of how the chemical might behave in the outdoor environment. A mesocosm is any outdoor experimental system that examines the natural environment under controlled conditions. Possible scenarios could include dosing experiments to evaluate the impact of chemical exposures (e.g., pesticides and solvents) on organisms or communities in their natural habitats. Mesocosm studies may be conducted in an enclosure or partial enclosure that is small enough so that key variables can be brought under control.
The Challenges of Remediating Metals Using Phytotechnologies
Published in Edgardo R. Donati, Heavy Metals in the Environment, 2018
Sabrina G. Ibañéz, Ana L. Wevar Oller, Cintia E. Paisio, Lucas G. Sosa Alderete, Paola S. González, María I. Medina, Elizabeth Agostini
According to the International Union of Pure and Applied Chemistry, a mesocosm is an enclosed and essentially self-sufficient experimental environment or ecosystem that is on a larger scale than a laboratory microcosm (Duffus et al., 2007). Other definitions described them based on certain characteristics that confer more advantages to mesocosms (Amiard-Triquet, 2015). However, all researchers agree on highlighting the important advantages of these systems which allow studying a number of questions concerning ecosystems and their processes as well as they permit an improvement of the realism of field conditions. In fact, they allow taking into account both direct effects of contaminants and indirect effects from the interaction between species and the environment in a natural or reconstructed ecosystem. It is assumed that mesocosms did not cause significant artifacts and the results obtained can be extrapolated to field conditions (Tingey et al., 2008).
Mesocosm Studies
Published in Susan B. Norton, Susan M. Cormier, Glenn W. Suter, Ecological Causal Assessment, 2014
Joseph M. Culp, Alexa C. Alexander, Robert B. Brua
Mesocosms are outdoor or indoor facilities with controlled physicochemical conditions and sometimes standardized biological assemblages. They are used to simulate complex exposure dynamics under simulated but realistic field conditions (Culp and Baird, 2006). Mesocosms are variously defined, but here we follow the general classification of Boyle and Fairchild (1997). They describe mesocosms as facilities that range in size from ponds or large experimental streams with defined physical dimensions and water quality, to smaller semicontrolled limnocorrals, tanks, and streams, to small (<1 m3) tanks or recirculating streams (i.e., sometimes labeled microcosms) with strictly controlled biological assemblages and physicochemical conditions.
Engineered nanomaterials in the environment: Are they safe?
Published in Critical Reviews in Environmental Science and Technology, 2021
Jian Zhao, Meiqi Lin, Zhenyu Wang, Xuesong Cao, Baoshan Xing
The microcosm and mesocosm approaches could be more realistic to reveal the ecotoxicity of NMs in terrestrial and aquatic ecosystems (Jovanović et al., 2016; Lu et al., 2020; Vijayaraj et al., 2018). A mesocosm experiment (5 weeks) was conducted to investigate the toxicity of TiO2 NMs to periphytic algae. TiO2 NMs at 0.05 mg/L (ECRs) did not show significant changes on growth and algal assemblage composition, suggesting that TiO2 NMs had low environmental risk in natural waters (Wright et al., 2018). However, TiO2 NMs at 5 mg/L (concentration in wastewater) decreased periphyton biomass and altered algal assemblage structure, indicating that the toxicity of TiO2 NMs in wastewater should be paid more attention. In another mesocosm study, TiO2 NMs at 0.025 and 0.25 mg/L reduced the biomass of Rotifera, however, the growth of Cladocera, Copepoda, phytoplankton, macrophytes, chironomids and fish was unaffected (Jovanović et al., 2016). Therefore, TiO2 NMs at ECRs would not significantly affect the main functions of freshwater ecosystem. For CuO NMs (12.5 µg/L) in a mesocosm, no mortality was observed for the endobenthic species (Scrobicularia plana and Hediste diversicolor) after exposure for 21 days (Buffet et al., 2013), although some biochemical parameters such as behavioral biomarkers, antioxidant defenses and genotoxicity were changed during exposure.
Road salt chloride retention in wetland soils and effects on dissolved organic carbon export
Published in Chemistry and Ecology, 2020
Kayla M. McGuire, Kristin E. Judd
A number of factors may affect how salt affects DOC mobility in soils, and our findings that salt reduced or had no effect on DOC export is consistent with other studies in both uplands [34,36] and wetlands [43], although the underlying mechanism may differ or be difficult to discern. For example, Green et al. [39] found that while soils that had no previous exposure to road salts released more DOC upon salt application, soils with a long history of salt exposure released less DOC when exposed to salt than controls. Chronic salt exposure could enhance soil respiration through elevating the pH of naturally acidic soils (e.g. through enhanced NH4+ mobilisation [37]), or DOC mobilisation effects could be short-lived (i.e. the ‘when it’s gone, it’s gone’ hypothesis [39]). Previous chronic salt exposure could explain reduced DOC export from the urban PC soils that receive stream water overflow that can reach conductivities of >5 mScm−1 during snow melt (unpublished data). However, the other two sites used in our study are not likely to receive large salt inputs. Salt could also reduce DOC mobilisation by lowering pH, due to the mobile anion effect, reducing DOC mobilisation [38,39]. Such a mechanism was found in soils from a coastal fen peatland [41]. Our experimental setup also may have altered environmental conditions in a way that favoured that favoured DOC consumption over DOC mobilisation. A laboratory mesocosm experiment similar to ours found a reduction in DOC release under elevated Clin [67]. The frequent flushing events may have reduced anoxia in the wetland sediments and encouraged aerobic respiration. Interestingly, in our study, one site that did not experience a significant decrease in DOC export (PMP) had the lowest OM (Table 1), supporting the idea that shifts in microbial respiration may be the cause of reduced DOC export.
Evaluation of the effectiveness of bioaugmentation and biostimulation in atrazine removal in a polluted matrix using degradation kinetics
Published in Soil and Sediment Contamination: An International Journal, 2023
Godwin O. Aliyu, Chukwudi U. Anyanwu, Chukwudi I. Nnamchi, Chukwudi O. Onwosi
The viable cell counts were carried out on the treatments to examine the combined effect of atrazine and soil amendments on the bacterial population (Figure 3). At the beginning of the experiment, each treatment mesocosm possessed 108 cells of A. faecalis per gram of soil. However, after 35 days, the viable counts in the soils treatments increased to 9.6 ± 0.37 x 108 CFU g−1, 9.4 ± 0.92 x 108 CFU g−1, 6.3 ± 1.60 x 108 CFU g−1 and 3.4 ± 0.08 x 108 CFU g−1 in treatments B + M, M, B, and C, respectively. The multiple comparisons of the individual treatments showed that the bacterial counts were significantly different (0.0001 > p > .001). However, there was no significant difference (p = .9901) in microbial counts when treatments M and B + M were compared (Figure 3i). This was further validated using the confidence interval plots which indicated that the difference in means between the two treatments contains zero (Figure 3ii). Overall, there was an initial reduction in the mean viable bacterial count up till the 14th day, after which an increase in the bacterial count was observed till the 35th day of the study. However, the least bacterial count was observed in treatment C (control) possibly because the poor nutritional status of sterilized soil sparsely encouraged microbial activities. In the current study, a significant percentage of atrazine was dissipated within the first week in amended soil (i.e., 83.3, 78.5, and 81.9% in treatments B, M, and B + M, respectively). There was a further 6.9, 6.4, and 4.4% increase in atrazine removal in treatments B, M, and B + M, respectively; by the 14th day. On the contrary, there was 28 and 46% atrazine removal in the unamended soil (control) by the 7th and 14th day, respectively. Therefore, the rise in bacterial count observed after this period could be attributed to the high atrazine dissipation levels during the initial days of the experiment in the amended soils. These results showed that the application of low-cost biostimulating agents (poultry manure and biochar) supported microbial activities and also enhanced the dissipation of atrazine in contaminated soils.