Behavioural Responses and Mortality of Clarias gariepinus Juveniles Exposed to Acute Concentrations of Paraquat

Paraquat is the most common contact and non- selective herbicide for exterminating vegetative pest. Fish are ideal sentinels for detecting aquatic pollutants and are largely used as bio indicators of environmental pollution. This study is aimed to determine the behavioural changes, lethal concentrations (LCs) and mean lethal time (MLT) of paraquat exposed to Clarias gariepinus. A 96 hours renewable bioassay was conducted with various paraquat concentrations 0.0, 0.25, 0.50, 0.75, 1.0 and 1.25 mg/l. Behavioural changes and cumulative mortality were observed and recorded at 12, 24, 48, 72 and 96 hour. Behavioural changes such as air gulping, erratic swimming, loss of balance, excessive mucus secretion, discolouration and death were observed with severity increasing as concentration and duration of exposure increases. The LC50 values were decreased from 0.191mg/l (0.171 – 0.222) in 12 hour to 0.107mg/l (0.065 – 0.150) in 96 hour, while relative toxicity factor (TF) was increased from 1 to 1.79 times respectively. The 96hr MLT values were decreased from 91.18 hours (54.09-105.64) at the lowest concentration to 16.22 hours (9.06 – 25.15) at the highest concentration with relative toxicity time (RTT) increasing from 1 to 5.62 times. Herbicide should be apply with caution and studies on the sub lethal effects of paraquat on the haematological, biochemical and histological parameters of C. gariepinus juveniles will be necessary.

Enhanced Hydrocarbons Biodegradation at Deep-Sea Hydrostatic Pressure with Microbial Electrochemical Snorkels

In anaerobic sediments, microbial degradation of petroleum hydrocarbons is limited by the rapid depletion of electron acceptors (e.g., ferric oxide, sulfate) and accumulation of toxic metabolites (e.g., sulfide, following sulfate reduction). Deep-sea sediments are increasingly impacted by oil contamination, and the elevated hydrostatic pressure (HP) they are subjected to represents an additional limitation for microbial metabolism. While the use of electrodes to support electrobioremediation in oil-contaminated sediments has been described, there is no evidence on their applicability for deep-sea sediments. Here, we tested a passive bioelectrochemical system named ”oil-spill snorkel” with two crude oils carrying different alkane contents (4 vs. 15%), at increased or ambient HP (10 vs. 0.1 MPa). Snorkels enhanced alkanes biodegradation at both 10 and 0.1 MPa within only seven weeks, as compared to nonconductive glass controls. Microprofiles in anaerobic, contaminated sediments indicated that snorkels kept sulfide concentration to low titers. Bulk-sediment analysis confirmed that sulfide oxidation by snorkels largely regenerated sulfate. Hence, the sole application of snorkels could eliminate a toxicity factor and replenish a spent electron acceptor at increased HP. Both aspects are crucial for petroleum decontamination of the deep sea, a remote environment featured by low metabolic activity.

Co-Toxicity Factor Analysis Reveals Numerous Plant Essential Oils Are Synergists of Natural Pyrethrins against Aedes aegypti Mosquitoes

With insecticide-resistant mosquito populations becoming an ever-growing concern, new vector control technologies are needed. With the lack of new chemical classes of insecticides to control mosquito populations, the development of novel synergists may improve the performance of available insecticides. We screened a set of 20 plant essential oils alone and in combination with natural pyrethrins against Aedes aegypti (Orlando) female adult mosquitoes to assess their ability to synergize this natural insecticide. A co-toxicity factor analysis was used to identify whether plant oils modulated the toxicity of natural pyrethrins antagonistically, additively, or synergistically. Both knockdown at 1 h and mortality at 24 h were monitored. A majority of oils increased the toxicity of natural pyrethrins, either via an additive or synergistic profile. Many oils produced synergism at 2 µg/insect, whereas others were synergistic only at the higher dose of 10 µg/insect. Amyris, cardamom, cedarwood, and nutmeg East Indies (E.I.) oils were the most active oils for increasing the mortality of natural pyrethrins at 24 h with co-toxicity factors greater than 50 at either or both doses. A number of oils also synergized the 1 h knockdown of natural pyrethrins. Of these, fir needle oil and cypress oils were the most successful at improving the speed-of-action of natural pyrethrins at both doses, with co-toxicity factors of 130 and 62, respectively. To further assess the co-toxicity factor method, we applied selected plant essential oils with variable doses of natural pyrethrins to calculate synergism ratios. Only the oils that produced synergistic co-toxicity factors produced statistically significant synergism ratios. This analysis demonstrated that the degree of co-toxicity factor correlated well with the degree of synergism ratio observed (Pearson correlation coefficient r = 0.94 at 2 µg/insect; r = 0.64 at 10 µg/insect) and that the co-toxicity factor is a useful tool in screening for synergistic activity.

Biodegradation of nitroaromatic compounds in Red Water by white rot fungi Pleurotus ostreatus and floridae

Pleurotus fungi are basidiomycetes that stand out in the degradation of recalcitrant organic compounds such as lignin derivatives and phenolic compounds. The aim of this study was to make a comparative evaluation of the capacity of the Pleurotus ostreatus POS 560 and Pleurotus floridae PSP1 fungi in the degradation of 2,4 and 2,6-dinitrotoluene (DNTs) in effluent from an explosive factory. The characterization of the effluent indicated 318 mg L-1 of DNTs, 246 mg L-1 of COD and toxicity factor for Daphnia magna corresponding to 8. The conduct of a multivariate study estimated the influence of the variables pH (5.0 and 6.0), co-substrate concentration (10 and 20 g L-1 of glucose) and species of the fungus Pleurotus (ostreatus and floridae) on the degradation of DNTs, indicating that the variables Fungus and [Glucose] were significant (p <0.05) presenting effects in the order of + 4.45 ± 0.26 and -1.14 ± 0.26, respectively. The reproduction of the best efficiency conditions (P. floridae; pH 6.0 and 10 g L-1 of glucose) in agitated flasks (100 rpm, 26oC) was able to carry out, within 14 days of treatment, the removal of organic matter and toxicity factor in levels on the order of 55 and 50%, respectively, in addition to the complete degradation of DNTs which occurred in the first 120 hours of treatment. In this period, the maximum activity of the peroxidase and Mn-peroxidase enzymes was also characterized, suggesting high potential of the bioprocess under study for remediation of effluents contaminated with nitroaromatic compounds.

Ozonation Pretreatment for Reduction of Landfill Leachate Fouling on Membranes: A Response Surface Methodology Analysis

Batch ozonation was performed to assess its efficacy as a pretreatment for reverse osmosis (RO) membranes for treating leachate with high concentrations of recalcitrant organic compounds. Leachate samples from two different landfills were collected and characterized. The modified fouling index (MFI) was used to estimate the fouling potential of raw and ozonized leachates. A response surface experimental design was applied to optimize operational pH and ozone dose. The results demonstrate that the best operational conditions are 1.5 g/L of O3 at pH 12.0 and 1.5 g/L of O3 at pH 9.0 for Landfills 1 and 2, which reduce MFI by 96.22% and 94.08%, respectively. Additionally, they show toxicity factor decays of 98.44% for Landfill 1 and 93.75% for Landfill 2. These results, along with the similar behavior shown by leachate samples from distinct landfills, suggest that ozonation is a promising technology to fit this kind of wastewater into the requirements of RO membranes, enabling their use in such treatment.

Analysis of optimal harvesting of a prey-predator fishery model with the limited sources of prey and presence of toxicity

A model of prey and predator species is discussed to study the effects of the limited prey density and presence of toxicity. The model is studied for sustainable optimal harvesting. The existence of equilibrium points is analyzed to find the stability of coexistence equilibrium, and use Pontryagin’s maximal method to obtain the sustainable optimal harvesting. The results show that the optimal harvesting is obtained from the solution of optimal equilibrium. The toxicity factor decreases the sustainable harvesting.

Association between Urine Fluoride and Dental Fluorosis as a Toxicity Factor in a Rural Community in the State of San Luis Potosi

Objective. The aim of this study is to investigate urine fluoride concentration as a toxicity factor in a rural community in the state of San Luis Potosi, Mexico.Materials and Methods. A sample of 111 children exposed to high concentrations of fluoride in drinking water (4.13 mg/L) was evaluated. Fluoride exposure was determined by measuring urine fluoride concentration using the potentiometric method with an ion selective electrode. The diagnosis of dental fluorosis was performed by clinical examination, and the severity of damage was determined using Dean’s index and the Thylstrup-Fejerskov (TF) index.Results. The range of exposure in the study population, evaluated through the fluoride content in urine, was 1.1 to 5.9 mg/L, with a mean of 3.14 ± 1.09 mg/L. Dental fluorosis was present in all subjects, of which 95% had severe cases. Higher urine fluoride levels and greater degrees of severity occurred in older children.Conclusions. The results show that dental fluorosis was determined by the presence of fluoride exposure finding a high positive correlation between the severity of fluorosis and urine fluoride concentration and the years of exposure suggested a cumulative effect.