Effects Of Water Quality Parameters Research Articles

Genotype by environment interaction across time for Nile tilapia, from juvenile to finishing stages, reared in different production systems

Nile tilapia is one of the most important fish for aquaculture worldwide and it is produced under many different environmental and system conditions. Even though genotype by environment interaction (GEI) can arise due to many factors, most studies with Nile tilapia have focused more on the effects of water quality parameters and pound or cage systems. There is also lack of knowledge on GEI between fish at different ages, as before and after reaching sexual maturity. Therefore, the objective of the current work was to evaluate the magnitude of GEI on body weight in Nile tilapia raised in biofloc technology (BFT), cage and recirculation aquaculture systems (RAS) from 100 to 350 days of age. To evaluate the temporal trend of GEI a multi-trait random regression model (MTRRM) with age as random regression covariable was employed. Higher values of heritability estimates were found around 225 days, with a maximum of 0.4 for BW at RAS. Estimated genetic correlations between BFT and RAS were above 0.7 for almost any combination of ages evaluated. On the other hand, genetic correlations between Cage at ages below 150 days and either BFT or RAS at any other age were positive but lower than 0.6. Results for the estimated ratio of the indirect by direct response to selection were lower for selection performed at very younger ages whereas the desired response is for older ages. However, if the selection is performed around 225 days for either BTF or RAS this ratio is above 0.8 for most of the situations considered. In conclusion, MTRRM is shown to be a powerful statistical tool to assess changes across the time for genetic parameters of interest, such as covariance, correlations, and heritability. Also, the GEI across the three production systems considered was found to be dynamic across the ages evaluated, with stronger effects between Cage and both BFT and RAS if the selection is performed prior to 150 days of age.

Photocatalytic degradation of phenanthrene by graphite oxide-TiO2-Sr(OH)2/SrCO3 nanocomposite under solar irradiation: Effects of water quality parameters and predictive modeling

Polycyclic aromatic hydrocarbons (PAHs) are persistent and harmful pollutants with high priority concern in the environment. To efficiently and energy-savingly remove PAHs from water, this work prepared a novel graphite oxide-TiO2-Sr(OH)2/SrCO3 nanocomposite and evaluated its photocatalytic activity for degradation of phenanthrene (a model PAH) under simulated solar irradiation. The presence of 50 mg/L of the photocatalyst enhanced the pseudo-first-order photodegradation rate constant of phenanthrene by 11.6 times from 0.0005 ± 0.0000 min−1 (control) to 0.0058 ± 0.0004 min−1. Superoxide radicals (O2−) and hydroxyl radicals (OH) were found to be the key reactive species in the photocatalytic process. Based on analysis of intermediates and established photocatalysis chemistry, the degradation pathway was elucidated. The effects of various water quality parameters were investigated, including temperature, pH, ionic strength, humic acid and two surfactants (Tween 80 and sodium dodecyl sulfate (SDS)), and the underlying mechanisms were illustrated. Based on the effects of individual water quality parameters, two predictive models were established by addition or multiplication to predict the photocatalytic degradation rate under complex water matrices. Based on experimental results with seawater and in the presence of three model oil dispersants, the multiplicative model was shown to present a robust and accurate prediction of the phenanthrene photodegradation rate with a predicted correlation coefficient (r2pred.) of 0.9483. This study not only developed a new photocatalyst of high activity under solar light, but also provided useful information for its practical application under various water quality conditions.

Characterization of the effects of binary metal mixtures on short-term uptake of Cd, Pb, and Zn by rainbow trout (Oncorhynchus mykiss)

Biotic Ligand Models (BLMs) for individual metals improve our ability to regulate metals in the aquatic environment by considering the effects of water quality parameters (ionic composition, pH, DOC) on metal bioavailability. However, in natural aquatic systems, organisms are often simultaneously exposed to multiple metals and these interactions are not currently considered in BLMs or most environmental regulations. Recently, several different mixture BLMs (mBLMs) have been developed to begin assessing this issue. Some of these models assume competitive interactions between all metals, while others assume only metals with similar modes of action (e.g., Na+ or Ca2+ antagonists) will competitively interact. In this study, we used standard in vivo 3-h gill metal binding assays to characterize the uptake of Cd, Pb, and Zn individually and in binary mixtures with Ag, Cd, Cu, Pb, Ni, and Zn across a range of concentrations that encompassed the 96-h LC50 for each metal. Inhibition of Cd, Pb, and Zn uptake at the gill by introduction of a second metal was consistent with mode of action in some cases, but not others. Further, contrary to expectations, inhibition was always either non-competitive or could not be defined statistically. We also observed one example of stimulated metal uptake (Ni stimulated Zn uptake). Consistent with our previous experiments on Ag, Cu, and Ni, these studies suggest that current mBLM frameworks will need revision to better reflect the mechanisms underlying metal mixture interactions.

A linear and non-linear polynomial neural network modeling of dissolved oxygen content in surface water: Inter- and extrapolation performance with inputs' significance analysis

Accurate prediction of water quality parameters (WQPs) is an important task in the management of water resources. Artificial neural networks (ANNs) are frequently applied for dissolved oxygen (DO) prediction, but often only their interpolation performance is checked. The aims of this research, beside interpolation, were the determination of extrapolation performance of ANN model, which was developed for the prediction of DO content in the Danube River, and the assessment of relationship between the significance of inputs and prediction error in the presence of values which were of out of the range of training. The applied ANN is a polynomial neural network (PNN) which performs embedded selection of most important inputs during learning, and provides a model in the form of linear and non-linear polynomial functions, which can then be used for a detailed analysis of the significance of inputs. Available dataset that contained 1912 monitoring records for 17 water quality parameters was split into a “regular” subset that contains normally distributed and low variability data, and an “extreme” subset that contains monitoring records with outlier values. The results revealed that the non-linear PNN model has good interpolation performance (R2=0.82), but it was not robust in extrapolation (R2=0.63). The analysis of extrapolation results has shown that the prediction errors are correlated with the significance of inputs. Namely, the out-of-training range values of the inputs with low importance do not affect significantly the PNN model performance, but their influence can be biased by the presence of multi-outlier monitoring records. Subsequently, linear PNN models were successfully applied to study the effect of water quality parameters on DO content. It was observed that DO level is mostly affected by temperature, pH, biological oxygen demand (BOD) and phosphorus concentration, while in extreme conditions the importance of alkalinity and bicarbonates rises over pH and BOD.

Analisis Hubungan Kondisi Perairan dengan Terumbu Karang di Desa Pemuteran Buleleng Bali

Coral reefs in the village of Pemuteran used for tourism activities. In the process of growth, the coral reef is strongly influenced by the water conditions both physical and chemical factors. This study aims to determine the characteristics of the water based physical and chemical factors, determine the percentage of coral cover, determine the relationship and influence the quality of the waters with coral reefs. Research carried out at Pemuteran Village in Mey 2016. The method used is linear transects and transect quadrant, principal component analysis to determine the effect of water quality parameters and relationships with coral reef. The results of the characteristics of the waters on physical factors, namely temperature 30 – 31°C, depth 4– 75 m, brightness 13 m, turbidity 1,2 –5,4 NTU, current velocity 0,1 – 0,4 m/s, and the substrate of sand. Based on chemical factors, namely salinity 31,25 – 31,55 ‰, pH 6,9–7,5, DO 5,5 – 6,4 mg/l, BOD5 0,57 – 0,76 mg/l, TSS 248–504 mg/l, nitrate 0,021 - 0,908 mg/l, and phosphate 0,065-0,95 mg/l. Coral cover percentage point 1 at 50,67%, points 2 at 65%, points 3 at 35%,points 4 at 85,33% and points 5 at 16,67%. While the point 6 - 10 there are no coral reefs. The main components of water quality that affect to the coral reef are the turbidity and substrate. The results show that the correlation of temperature and nitrate correlated very weakly. pH, DO, BOD5 and phosphate correlated enough. Salinity, current, and TSS strongly correlated. Depth, brightness, turbidity and substrate strongly correlate.

Oxidation of geosmin and 2-methylisoborneol by the photo-Fenton process: Kinetics, degradation intermediates, and the removal of microcystin-LR and trihalomethane from Nak-Dong River water, South Korea

Due to the increased intensity and frequency of cyanobacterial blooms, taste and odor (T&O) causing compounds, geosmin (GSM) and 2-methylisoborneol (MIB), have become a cause for great concern in drinking water treatment plants (DWTPs). Advanced oxidation processes (AOPs) have been studied for the removal of GSM and MIB. However, in this work, a photo-Fenton treatment was investigated for the first time for the degradation of GSM and MIB in both synthetic and Nak-Dong River water from DWTPs. Synthetic water-based experiments were performed to investigate the optimal operation conditions for the removal of GSM and MIB, and the effects of water quality parameters of the photo-Fenton process, including the Fe(II)/H2O2 concentration, reaction time, pH, organic matter, and initial concentration of GSM and MIB. Degradation intermediates of dehydration and ring-opening were observed during the photo-Fenton process. The optimal conditions were determined to be 2mg/L Fe(II) and 20mg/L H2O2 at pH 5 considering both efficiency and cost. The degradation efficiency was lower than that of DI water, mainly because of the pH (7.2–7.6). Nevertheless, the photo-Fenton process meets the guideline levels (20ng/L) in South Korea when the initial concentration in the river water is below 50ng/L. In addition, trihalomethanes (THMs) and microcystin-LR (MC-LR), derived from cyanobacterial blooms and another cause for concern, were degraded effectively using the photo-Fenton process on the river water.

Changes in aquatic toxicity of potassium dichromate as a function of water quality parameters

Potassium dichromate (K2Cr2O7) is used as a general reference toxicant in aquatic toxicity testing, but relatively little is known regarding the effects of water quality parameters on K2Cr2O7 toxicity to Daphnia magna. The acute toxicity of K2Cr2O7 to D. magna was comparatively examined in one very hard (M4 medium for D. magna assay), four hard, one moderately hard and one soft dilution water samples. The 48-h EC50 (50% effective concentration) of K2Cr2O7 to D. magna was reproducible (coefficient of variation [CV]: 13%) in tests using the same dilution water sample, but reproducibility was poor (CV: 62%) in tests using seven different dilution water samples. The observed 48-h EC50 value increased with increasing water hardness (28–250 mg CaCO3/L) and Na+ concentration (4.3–19.7 mg Na/L). The effect of Ca2+ and Mg2+ on K2Cr2O7 toxicity was equivalent in terms of molar concentration. The 48-h EC50 for K2Cr2O7 was determined according to OECD TG 202 by six contract laboratories using M4 medium and were shown to be reproducible (CV: 15%), indicating that the toxicity level can be determined with high accuracy if holding and dilution water samples are standardized. Multiple regression analysis revealed that the 48-h EC50 was strongly correlated (r2 = 0.927) with the Ca2+, Mg2+, Na+ concentration, and alkalinity of the dilution water samples. Detailed monitoring of water quality characteristics thus facilitates intra- and inter-laboratory comparisons of toxicity data and enables predictions of changes in the susceptibility of test animals.

Effects of Water Quality Parameters on Abundance and Biomass of Zooplankton in Merbok Estuary Malaysia

Influence of water quality parameters on zooplankton abundance and biomass in the Merbok estuary Malaysia were investigated. Twenty four hours sampling were conducted at station 1, 3 and 5 from 12th November (spring tide) to 3rd December (neap tide) 2011 on weekly interval. Results showed that water quality parameters varied with the following ranges: conductivity (10.00-315.00?S-1cm), transparency (25.50-154.00 cm), light intensity (53.5-1959.00 lux), TSS (20-70 mg-1L), BOD (0.25-3.46 mg-1L) and chl a (0.1-1.46 ?g-1L). The highest zooplankton abundance was found at Station 5 (176×103) and (230×103) ind-3m and the lowest was at station 1(5.3×103) and (3.4 ×103) ind-3m during spring and neap tide. Zooplankton biomass varied from 0.04 to 0.096 gm-3m. Spearman’s rank correlation analysis results showed that there was a correlation among zooplankton abundance and conductivity, transparency, TSS, BOD, and biomass except chl and light intensity. Mann-Whitney U test result showed that water quality parameters, zooplankton abundance and zooplankton biomass were significantly different between spring and neap tides.J. Environ. Sci. & Natural Resources, 9(1): 117-122 2016

A novel advanced oxidation process using iron electrodes and ozone in atrazine degradation: Performance and mechanism

In this work, iron electrode was employed to enhance the reactivity of ozone (EC/O3) in atrazine degradation. Compared to ozonation and Fe2+-catalyzed ozonation, the elimination rate of atrazine by the EC/O3 process increased significantly with increasing applied currents. The simultaneous formation of hydroxyl radical (OH) and ferryl ion (Fe(IV)) from the reaction between ozone and in-situ formed Fe2+ was proposed and experimentally confirmed. The second order rate constant for atrazine reacting with Fe(IV) was estimated to be 125M−1s−1 using a relative rate method. The individual roles of the reactive species (OH, Fe(IV), and O3) in atrazine degradation were modeled using a kinetic model and OH was the predominant reactive species in the EC/O3 system. Furthermore, the effects of water quality parameters, such as initial pH and natural organic matters (NOM), on the performance of EC/O3 process were also evaluated. The results demonstrated that higher initial pH is favorable for ozone consumption and atrazine degradation. The presence of NOM appreciably inhibited the degradation of atrazine, which may be attributed to the competition of NOM for OH. This study provides a new approach to enhance ozonation, and broadens the knowledge of ozonation in removing organic contaminants from water.

Studying Effect of Water Quality Parameters on Coagulation Efficiency by Moringa Oleifera Seeds

The purpose of this study is to investigate the performance and efficiency of Moringa seeds from different sources on turbidity. A protein analysis test was done for each source; then two different methods of extraction were compared to examine the coagulation activity for the Moringa's active ingredient. The results of sodium chloride (NaCI) extraction in comparison to distilled water extraction of the Moringa olifera seeds showed that the salt solution extraction technique was more efficient than the distilled water for extracting the active coagulant ingredient. The above mentioned findings were used to examine the effects of other parameters such as pH, calcium and magnesium hardness, bicarbonate-alkalinity, and salinity independently on turbidity removal with an optimum dosage of 1% NaCI extract of dry shelled Moringa seeds. The obtained results showed that the water quality parameters had no significant effect on the coagulation potential of the NaCI extract of the shelled Moringa seeds and was almost amenable to a wide range of water environment condition.

Effects of water quality parameters on agglomeration and dissolution of copper oxide nanoparticles (CuO-NPs) using a central composite circumscribed design

Once released into the aquatic environment, nanoparticles (NPs) are expected to interact (e.g., dissolve, agglomerate, settle), with important consequences for particle fate and toxicity. However, a clear understanding of how environmental factors influence the toxicity and fate of NPs in the environment is still in its infancy. In this study, a second order central composite circumscribed design (CCCD) was employed to systematically explore how different combinations of pH, hardness, and natural organic matter (NOM) in receiving water affect the hydrodynamic diameter, surface charge (zeta potential), and release of free Cu2+ from CuO-NPs under a range of environmentally realistic conditions. The results clearly showed that all three CuO-NP properties varied markedly as functions of pH, hardness and dissolved NOM, confirming that agglomeration and the extent of release of free Cu2+ largely depend on the surrounding environmental conditions. The response of hydrodynamic diameter, but not zeta potential, to water quality parameters was highly time dependent, showing very different patterns on day 2 and day 10. The approach used in this study can contribute to improving understanding of how, and to what extent, environmental factors affect the physicochemical properties of CuO-NPs once they enter aquatic environments. This understanding can help to predict the conditions under which CuO-NPs are likely to become problematic, which can inform management and mitigation actions.

Effect of water quality parameters on solar water disinfection: a statistical experiment design approach

With a view to evaluating the effects and interactions of three influential factors, turbidity, pH and dissolved oxygen (DO), on the efficiency of solar water disinfection process, response surface methodology (RSM) based on Box–Behnken design was employed. Total coliform (TC) removal and heterotrophic plate count (HPC) removal were used as response factors. The RSM models were developed based on the experimental results of four-hour solar exposure in polyethylene terephthalate bottles. The measured and predicted removals were close to each other. Though the HPC removal and TC removal showed similar trends, the HPC removal was much lower (40–66%) compared to TC removal (68–97%) for the conditions studied. The results showed that turbidity up to certain levels (10–20 NTU) did not adversely impact the bacterial removal. In the range studied (6.0–9.5), pH showed little influence on the removals. While bacterial inactivation showed significant reduction at low DO levels, increasing DO beyond a certain level (5–6 mg/L) did not show any beneficial effect on bacterial inactivation. The study thus demonstrated the usefulness of RSM in modelling and analysing solar disinfection process.

Development of biotic ligand models for chronic manganese toxicity to fish, invertebrates, and algae

Ecotoxicity tests were performed with fish, invertebrates, and algae to investigate the effect of water quality parameters on Mn toxicity. Models were developed to describe the effects of Mn as a function of water quality. Calcium (Ca) has a protective effect on Mn toxicity for both fish and invertebrates, and magnesium (Mg) also provides a protective effect for invertebrates. Protons have a protective effect on Mn toxicity to algae. The models derived are consistent with models of the toxicity of other metals to aquatic organisms in that divalent cations can act as competitors to Mn toxicity in fish and invertebrates, and protons act as competitors to Mn toxicity in algae. The selected models are able to predict Mn toxicity to the test organisms to within a factor of 2 in most cases. Under low-pH conditions invertebrates are the most sensitive taxa, and under high-pH conditions algae are most sensitive. The point at which algae become more sensitive than invertebrates depends on the Ca concentration and occurs at higher pH when Ca concentrations are low, because of the sensitivity of invertebrates under these conditions. Dissolved organic carbon concentrations have very little effect on the toxicity of Mn to aquatic organisms.

Response to the comments of Y. S. Ho to the paper ‘‘Sorption of radionickel to goethite: effect of water quality parameters and temperature’’

In our published paper entitled ‘‘Sorption of radionickel to goethite: effect of water quality parameters and temperature’’ published in JRNC 285 (2010) 389–398 [1], the sorption of radionickel to goethite as affected by various environmental conditions such as pH, humic substances, ionic strength and temperature on radionickel sorption has been investigated by using batch technique. The sorption mechanism of radionickel on goethite was discussed according to the experimental data and the fitting results of sorption isotherms by Langmuir, Freundlich and D-R models. Kinetic sorption data was fitted by a pseudo-second-order rate equation. Ho et al. firstly reported the pseudo-second-order rate equation [2, 3], and then further developed this frame work in their following works [4, 5]. In our previous research, we had ever cited the original paper about the sorption isotherms such as Langmuir or Freundlich models. However, the reviewers gave the comments that the models had been widely used and it was not necessary for us to cite the original paper about the sorption isotherm. Similar condition can be also observed for carbon nanotubes that there are a lot of papers about carbon nanotubes not citing the original paper reported by Iijima [6]. In our published paper [1], we think that the pseudo-second-order rate equation has been widely applied and the equation is now a famous model to fit the sorption kinetic data. However, it is essential for us to cite all the relative references accurately so as to transmit scientific knowledge more effectively. We are so sorry to the fact that the original papers [2, 3] were not cited in our published paper [1], but it is not meant to show the disrespect to the author Ho [2]. In our future work, we wish to cite the papers published by Ho whose work are interesting and useful to simulate the sorption kinetic data of metal ions at solid–water interfaces. The physicochemical behavior of radionickel in environment is quite important to understand the potential pollution of radionickel in natural environment. In our published paper [1], the macroscopic data is helpful to understand the sorption mechanism of radionickel at solid– water interfaces. However, the information at microscopic level such as microstructures and chemical species of radionickel can be more accurate to assess the potential physicochemical behavior of radionickel in the environment. This information can be obtained from spectroscopy studies such as XPS, TRLFS and EXAFS.

Comments on the paper “Sorption of radionickel to goethite: effect of water quality parameters and temperature” by Hu et al.

Recently, Hu et al. [1]. published a paper with the abovetitle. In section ‘‘Effect of contact time’’, the authors stated,‘‘In order to study the sorption rate constant of Ni(II) togoethite, the pseudo-second-order rate equation was usedto fit the kinetic sorption of Ni(II) to goethite:’’ and referredto two self-citations published in 2008 and 2010 respec-tively [2, 3]. In fact, this kinetic model has already beenpublished first in 1996 [4], and a modified model waspresented in the following years to correct a mistake in the1996 paper [5–7]. However the mistake in the model wasduplicated by other researchers [8, 9]. In order to stop theproliferation of the mistake a comment has been made [10].This type of error could be avoided if authors have had paidmore attentions to details about the model from the originalpaper [11].Accuracy in citing references is very important for thetransmission of scientific knowledge. Citation errors reflectpoorly on authors who republish original ideas that werealready published. Hopefully, the identification of this typeof problems will lead to improved accuracy in referencing[12]. Authors should make serious efforts to check theaccuracy of references cited in their manuscripts as well asto read the original article before quoting it rather thanciting from abstracts or cross-references [13]. It isrecommended that more attention should be paid in pre-paring bibliographies and in checking quoted references[14].References

Combined effects of water quality parameters on mixture toxicity of copper and chromium toward Daphnia magna

In this study, a central composite design (CCD) was employed to evaluate the combined effects of pH, hardness and dissolved organic carbon (DOC) on the toxicity of a mixture of Cu(II) and Cr(VI) toward Daphnia magna. Overall, the results showed that increases in pH, hardness and DOC concentration led to decreased mixture toxicity of Cu(II) and Cr(VI) by reducing the concentrations of toxic species such as Cu 2+ and HCrO 4 - . In addition, empirical models for the prediction of 24-h and 48-h mortalities of D. magna were developed and validated by using three different sources of dissolved organic matter (DOM). Because the DOMs had different Cu(II)-binding capacities, the empirical models were revised using the ligand concentration of DOMs instead of the DOC concentration; however, the prediction capability of these models did not differ significantly. These results suggest that it is not likely that the chemical property of DOM is important for prediction of the mixture toxicity of Cu(II) and Cr(VI) toward D. magna when the ligand concentration of DOMs greatly exceed the Cu(II) concentration.

Modeling the formation and assessing the risk of disinfection by-products in water distribution systems

The effect of water quality parameters and operation conditions of water treatment on the formation of trihalomethanes (THM) and haloacetic acids (HAA) in pilot-scale reactor and water distribution system were investigated. Results indicated that dissolved organic carbon and THM formation increased while the concentration of free chlorine decreased along the length of pipeline from the water treatment plant; but HAA formation showed no relationship with the pipeline length. THM concentration was predicted with hydraulic analytic software, namely WaterCAD. The predicted THM data were within ±10% of measurements; HAA had a relatively high error of ±16% due to complex bio-decomposition reactions occurred in the distribution system. Both the hazardous quotient and cancer risk of THM in the water distribution system of an advanced water treatment plant were much lower than those of a conventional water treatment plant; there was no significant difference in hazard quotient and cancer risk of HAA in the above two water distribution systems.

Sorption of radionickel to goethite: Effect of water quality parameters and temperature

In this work, sorption of Ni(II) from aqueous solution to goethite as a function of various water quality parameters and temperature was investigated. The results indicated that the pseudo-second-order rate equation fitted the kinetic sorption well. The sorption of Ni(II) to goethite was strongly dependent on pH and ionic strength. A positive effect of HA/FA on Ni(II) sorption was found at pH 8.0. The Langmuir, Freundlich, and D-R models were applied to simulate the sorption isotherms at three different temperatures of 293.15 K, 313.15 K and 333.15 K. The thermodynamic parameters (ΔH0, ΔS0 and ΔG0) were calculated from the temperature dependent sorption, and the results indicated that the sorption was endothermic and spontaneous. At low pH, the sorption of Ni(II) was dominated by outer-sphere surface complexation or ion exchange with Na+/H+ on goethite surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH.

Factors influencing the formation of chlorination brominated trihalomethanes in drinking water

The formation of brominated trihalomethanes (THMs-Br) which is proved more carcinogenic than their chlorinated analogues reported was very different at various water qualities. This study was performed to assess the effects of water quality parameters (bromide concentration, pH value and ammonia concentration), chlorination conditions (chlorine dose, reaction time) and ratios of Br − /DOC and Br − /Cl2 consumption on the formation and distribution of THMs-Br in chlorination. The results showed good correlation between the bromine incorporation factor (BIF) n(Br) and Br − /Cl2 consumption ratio. The formation of total THM (TTHM) was found to decrease with increasing ammonia concentration but to increase with bromide concentration and pH value. The n(Br) trends were significantly affected by the presence of bromide concentration. The effects on the molar yields of THMs were more strongly influenced by bromide concentration and dissolved organic carbon (DOC) concentration than pH value and natural organic matter (NOM) source. High Br − /DOC and Br − /Cl2 favor the formation of THMs-Br over chlorinated THMs (THMs-Cl). The experimental data including the main parameters such as bromide, DOC, ammonia, pH and reaction time were used for developing the predictive model for THMs-Br.

Acute and chronic toxicity of nano-scale TiO2 particles to freshwater fish, cladocerans, and green algae, and effects of organic and inorganic substrate on TiO2 toxicity

This research evaluated the toxicity of TiO2 nanoparticles to freshwater aquatic organisms and the effects of organic and inorganic material on TiO2 toxicity. The fathead minnow was much less acutely sensitive to TiO2 (LC50 500 mg/l and higher) than Ceriodaphnia dubia and Daphnia pulex (mean LC50 values 7.6 and 9.2 mg/l, respectively). Total organic carbon levels of 1.5 mg/l decreased TiO2 acute toxicity to C. dubia (LC50 > 100 mg/l), but kaolinite clay decreased TiO2 toxicity to a lesser extent. In chronic toxicity tests, the green algae Pseudokirchneriella subcapitata was more sensitive to TiO2 (IC25 1–2 mg/l) than C. dubia (IC25 9.4–26.4 mg/l) and the fathead minnow (IC25 values over 340 mg/l). Study results indicate that the specific organisms exposed and the effects of water quality parameters on TiO2 toxicity should be considered in hazard evaluations of this nanoparticle.