Water Quality Assessment of Surface Waters and Wastewaters by Traditional and Ecotoxicological Indicators in Ogosta River, Bulgaria

Surface water samples in Ogosta River, Bulgaria and wastewater samples at the inlet and outlet of WWTP–Montana were tested for the traditional parameters and ecotoxicological effect. The river and Dam surface waters comply with category A1 of Directive 75/440/EEC for pH, EC, COD, TSS, NO3–, Cl–, SO42–, B, Ba, Co, Cr, Cu, Hg, Mn, Ni, Pb, Se, V and Zn; with category A2 for BOD5, NH4+–N and Fe; and with category A3 for TNb and As. The average annual concentrations of Al, Cr (III), Cr (VI) and U are lower than the set limits in the Water Framework Directive. Arsenic concentration in all the samples exceeds the maximum allowed concentration, a results from natural processes. All the levels of the studied parameters in the outlet wastewater samples are lower than the limits, set in Directive 91/271/EEC and in the complex permit of the WWTP. The results of the biotest Phytotoxkit F™ show low ecotoxicity of the water samples. Optimization of the sample pretreatment prior to this ecotoxicological test is analyzed and discussed.

Ecotoxicological effects of glyphosate, 2,4 D and atrazine on freshwater systems: concentrations, risk assessment and establishment conditions of a tropical specie

Pesticides are agents of global change, since they can be transported to environmental compartments, cause adverse effects on non-target species. The most worldwide used pesticide is glyphosate. Some studies have already shown adverse effects on aquatic species caused by glyphosate, which is triggering global discussions about its legislation and use. Brazil has up to date no prospect of reducing or banning the use of the three most used pesticides in the country, glyphosate, 2,4 D and atrazine. The knowledge on adverse effects of pesticides and other chemical contaminants in tropical species is still scarce, maybe because many do not have defined protocols for ecotoxicological test conditions. The purposes of the each chapter of this study were: (1) to investigate the global glyphosate concentrations in surface freshwaters, to compare the countries laws and to carry out environmental risk assessments; (2) to investigate the Brazilian concentrations of glyphosate, 2,4D and atrazine in surface freshwater, and to assess the potential environmental risks they represent; (3) to describe the steps and the challenges for culturing the tropical test species Chironomus xanthus as well as to discuss its current use in ecotoxicology. Information on glyphosate concentrations in surface freshwater is scarce and known values very irregular among the countries investigated, with 95% of the studied systems showing concentrations that represent a risk to aquatic species. Most countries evaluated did not have restrictive legislation for the glyphosate presence in water resources, resulting in the non-protection of aquatic organisms. There was an increase in the annual sales of 2,4D, atrazine and glyphosate between 2009 and 2018 in Brazil. Although most environment concentrations were below the limit allowed by Brazilian legislation, the observed concentrations represented a medium to high risk for ecosystems in 65%, 72% and 94% of the Brazilian states for 2,4 D, atrazine and glyphosate, respectively. The ecotoxicological effect of pesticides, as well as of other contaminants in freshwater sediments are very often performed with benthic macroinvertebrates. Chironomus xanthus has been increasingly used for the past of years. Therefore, conditions for Chironomus xanthus establishment, maintenance and operation in the laboratory are necessary, due to the absence of protocols for this species.

Influence of Extremophiles on the Generation of Acid Mine Drainage at the Abandoned Pan de Azúcar Mine (Argentina)

The risk of generation of acid drainages in the tailings of the Pan de Azúcar mine that closed its activities more than three decades ago, was evaluated through biooxidation studies using iron- and sulfur-oxidizing extremophilic leaching consortia. Most of tailings showed a high potential for generating acid drainage, in agreement with the results from net acid generation (NAG) assays. In addition, molecular analysis of the microbial consortia obtained by enrichment of the samples, demonstrated that native leaching microorganisms are ubiquitous in the area and they seemed to be more efficient in the biooxidation of the tailings than the collection microorganisms. The acid drainages detected at the site and those formed by oxidation of the tailings, produced a significant ecotoxicological effect demonstrated by a bioassay. These drainages, even at high dilutions, could seriously affect a nearby Ramsar site (Laguna de Pozuelos) that is connected to the Pan de Azúcar mine through a hydrological route (Cincel River).

The Ecotoxicological Effects of Microplastics on Primary Producers in the Marine Environment

Plastic debris is an emerging environmental threat all over the world. But its effect and distribution in the marine ecosystem is barely known. Microplastics abundance in the marine vegetated area is about 2 to 3 times higher than the bare site in the ocean. Although seagrass meadows trap huge amount of microplastics over the ocean floor, a considerable amount of microplastics are also sink incorporating with the marine aggregates from the epipelagic zone of the ocean. Scavenging of microplastics by diatom aggregation decreases the sinking rate of them rather than cryptophyte. As we know, marine snow is the leading carbon source for zoobenthos, but the ubiquitous presence of microplastics damages cell of different microalgae which may alter the food webs of marine ecosystems. Additionally, microplastics releases immense amount of dissolved organic carbons (DOC) in the surrounding seawater that stimulates the growth of heterotrophic microorganisms as well as their functional activity. Plastic debris result in outbreaks of disease in the marine environment and coral reefs are highly affected by it. When coral reef comes in contact with microplastics, the disease infestation rate of the reef increases massively. Three major disease viz., skeletal eroding band, white syndrome and black band of coral reef causes approximately 46% of reef mortality due to microplastics consumption. Due to complex structure and size, the corals accumulates huge amount of microplastics that increases growth of pathogens by hampering the coral immune system. Existing scientific evidence presents that exposure of microplastics in aquatic environments triggers a wide variety of toxic insult from feeding disruption to reproductive performance, disturbances in energy metabolism throughout the ocean. The present review focused on the ecotoxicological effect of microplastics on primary producers of ocean, its uptake, accumulation, and excretion, and its probable toxicity with risk assessment approaches.

Ecotoxicological Effect of Aged Wood Leachates to Aquatic Organisms

Wood is an important natural resource used for various human activities. Toxicity of wood leachate in aquatic organisms has been previously established, but whether storage over time has an impact on the quality of leachate has not been assessed. Hence, this research seeks to assess the toxicity of aged wood leachate in aquatic organisms. Five fresh wood samples were randomly selected from the Oboyow forest reserve in the eastern region of Ghana: Mahogany (Khaya ivorensis), Cedrela (Cedrela odorata), Emire (Terminalia ivorensis), Wawa (Triplochiton scleroxylon), and Ceiba (Ceiba pendandra) to assess their toxicity to aquatic organisms. Algal (Desmodesmus subspicatus) duckweed (Lemna minor) and daphnia (Daphnia magna) were carried out using exposures to concentrations of 20%, 30%, 45%, 67%, and 100% v/v of wood leachate with control media, because they represented various concentration rate levels of wood leachate toxicity in the test organisms. The toxicity of the various wood leachates might be due to high levels of biochemical oxygen demand (BOD), chemical oxygen demand (COD), and total organic carbon (TOC), i.e., metals and phenols. The % IC50 of the various wood leachate ranged from 21.51–66.77% with mahogany exhibiting the highest toxicity and wawa the lowest. It was also observed that toxicity of wood leachates decreased as the wood leachate aged. The % IC50 showed both confirmed and potential toxicity among the various wood leachates.

PLAGA-PEG-PLAGA Terpolymer-Based Carriers of Herbicides for Potential Application in Environment-Friendly, Controlled Release Systems of Agrochemicals

The present study aimed to develop and prepare new polymer/herbicide formulations for their potential application in environment-friendly, controlled release systems of agrochemicals. Selected biodegradable polymers, including L-Lactide/Glycolide/PEG/Terpolymer (PLAGA-PEG-PLAGA) as well as oligosaccharide-based polymers and their blend with terpolymer, were used to prepare microspheres loaded with two soil-applied herbicides. The degradation process of the obtained polymeric microspheres was evaluated based on (1) their weight loss and surface erosion and (2) the release rate of loaded metazachlor and pendimethalin. The herbicidal effectiveness of the herbicides released to the soil from microspheres was evaluated using the European Weed Research Council (EWRC) rating scale. Moreover, the ecotoxicological effect of herbicide-loaded microspheres buried in soil on the marine bacterial species A. fischeri was assessed. It was found that the gradual degradation rate of microparticles led to the prolonged release of both herbicides that lasted for a few months, i.e., for the entire crop season, which is crucial in terms of agrochemical and environmental protection. Maltodextrin- and dextrin-based microspheres showed higher susceptibility to degradation than terpolymer-based microspheres. The microencapsulation of herbicides protected them from decomposition and excessive leaching into soil and maintained their activity for a longer period than that for non-immobilized herbicides. The ecotoxicological assessment on A. fischeri demonstrated that the proposed microsphere-encapsulated herbicides were less toxic than non-immobilized herbicides.