Effects of light and temperature fluctuations on the growth of Myriophyllum spicatum in toxicity tests—a model-based analysis

Laboratory toxicity tests are a key component of the aquatic risk assessments of chemicals. Toxicity tests with Myriophyllum spicatum are conducted based on working procedures that provide detailed instructions on how to set up the experiment, e.g., which experimental design is necessary to get reproducible and thus comparable results. Approved working procedures are established by analyzing numerous toxicity tests to find a compromise between practical reasons (e.g., acceptable ranges of ambient conditions as they cannot be kept completely constant) and the ability for detecting growth alterations. However, the benefit of each step of a working procedure, e.g., the random repositioning of test beakers, cannot be exactly quantified, although this information might be useful to evaluate working procedures. In this paper, a growth model of M. spicatum was developed and used to assess the impact of temperature and light fluctuations within the standardized setup. It was analyzed how important it is to randomly reassign the location of each plant during laboratory tests to keep differences between the relative growth rates of individual plants low. Moreover, two examples are presented on how modeling can give insight into toxicity testing. Results showed that randomly repositioning of individual plants during an experiment can compensate for fluctuations of light and temperature. A method is presented on how models can be used to improve experimental designs and to quantify their benefits by predicting growth responses.     

Coagulant recovery from water treatment plant sludge and reuse in post-treatment of UASB reactor effluent treating municipal wastewater

In the present study, feasibility of recovering the coagulant from water treatment plant sludge with sulphuric acid and reusing it in post-treatment of upflow anaerobic sludge blanket (UASB) reactor effluent treating municipal wastewater were studied. The optimum conditions for coagulant recovery from water treatment plant sludge were investigated using response surface methodology (RSM). Sludge obtained from plants that use polyaluminium chloride (PACl) and alum coagulant was utilised for the study. Effect of three variables, pH, solid content and mixing time was studied using a Box–Behnken statistical experimental design. RSM model was developed based on the experimental aluminium recovery, and the response plots were developed. Results of the study showed significant effects of all the three variables and their interactions in the recovery process. The optimum aluminium recovery of 73.26 and 62.73 % from PACl sludge and alum sludge, respectively, was obtained at pH of 2.0, solid content of 0.5 % and mixing time of 30 min. The recovered coagulant solution had elevated concentrations of certain metals and chemical oxygen demand (COD) which raised concern about its reuse potential in water treatment. Hence, the coagulant recovered from PACl sludge was reused as coagulant for post-treatment of UASB reactor effluent treating municipal wastewater. The recovered coagulant gave 71 % COD, 80 % turbidity, 89 % phosphate, 77 % suspended solids and 99.5 % total coliform removal at 25 mg Al/L. Fresh PACl also gave similar performance but at higher dose of 40 mg Al/L. The results suggest that coagulant can be recovered from water treatment plant sludge and can be used to treat UASB reactor effluent treating municipal wastewater which can reduce the consumption of fresh coagulant in wastewater treatment.     

A new bioseed for determination of wastewater biodegradability: analysis of the experimental procedure

A new bioassay proposed in the patent P201300029 was applied to a pre-treated wastewater containing a mixture of commercial pesticides to simulate a recalcitrant industrial wastewater in order to determine its biodegradability. The test uses a mixture of standardized inoculum of the lyophilized bacteria Pseudomonas putida with the proper proportion of salts and minerals. The results highlight that biodegradation efficiency can be calculated using a gross parameter (chemical oxygen demand (COD)) which facilitates the biodegradability determination for routine water biodegradability analysis. The same trend was observed throughout the assay with the dehydrated and fresh inoculums, and only a difference of 5 % in biodegradation efficiency (E _f) was observed. The obtained results showed that the P. putida biodegradability assay can be used as a commercial test with a lyophilized inoculum in order to monitor the ready biodegradability of an organic pollutant or a WWTP influent. Moreover, a combination of the BOD₅/COD ratio and the P. putida biodegradability test is an attractive alternative in order to evaluate the biodegradability enhancement in water pre-treated with advanced oxidation processes (AOPs).     

Mechanical and toxicological evaluation of concrete artifacts containing waste foundry sand

The creation of metal parts via casting uses molds that are generally made from sand and phenolic resin. The waste generated after the casting process is called waste foundry sand (WFS). Depending on the mold composition and the casting process, WFS can contain substances that prevent its direct emission to the environment. In Brazil, this waste is classified according to the Standard ABNT NBR 10004:2004 as a waste Class II (Non-Inert). The recycling of this waste is limited because its characteristics change significantly after use. Although the use (or reuse) of this byproduct in civil construction is a technically feasible alternative, its effects must be evaluated, especially from mechanical and environmental points of view. Thus, the objective of this study is to investigate the effect of the use of WFS in the manufacture of cement artifacts, such as masonry blocks for walls, structural masonry blocks, and paving blocks. Blocks containing different concentrations of WFS (up to 75% by weight) were produced and evaluated using compressive strength tests (35 MPa at 28 days) and toxicity tests on Daphnia magna, Allium cepa (onion root), and Eisenia foetida (earthworm). The results showed that there was not a considerable reduction in the compressive strength, with values of 35 ± 2 MPa at 28 days. The toxicity study with the material obtained from leaching did not significantly interfere with the development of D. magna and E. foetida, but the growth of the A. cepa species was reduced. The study showed that the use of this waste in the production of concrete blocks is feasible from both mechanical and environmental points of view.     

Determination of specific gravity of municipal solid waste

This investigation was conducted to evaluate experimental determination of specific gravity (G_s) of municipal solid waste (MSW). Water pycnometry, typically used for testing soils was adapted for testing MSW using a large flask with 2000 mL capacity and specimens with 100–350 g masses. Tests were conducted on manufactured waste samples prepared using US waste constituent components; fresh wastes obtained prior and subsequent to compaction at an MSW landfill; and wastes obtained from various depths at the same landfill. Factors that influence specific gravity were investigated including waste particle size, compaction, and combined decomposition and stress history. The measured average specific gravities were 1.377 and 1.530 for as-prepared/uncompacted and compacted manufactured wastes, respectively; 1.072 and 1.258 for uncompacted and compacted fresh wastes, respectively; and 2.201 for old wastes. The average organic content and degree of decomposition were 77.2% and 0%, respectively for fresh wastes and 22.8% and 88.3%, respectively for old wastes. The G_s increased with decreasing particle size, compaction, and increasing waste age. For fresh wastes, reductions in particle size and compaction caused occluded intraparticle pores to be exposed and waste particles to be deformed resulting in increases in specific gravity. For old wastes, the high G_s resulted from loss of biodegradable components that have low G_s as well as potential access to previously occluded pores and deformation of particles due to both degradation processes and applied mechanical stresses. The G_s was correlated to the degree of decomposition with a linear relationship. Unlike soils, the G_s for MSW was not unique, but varied in a landfill environment due both to physical/mechanical processes and biochemical processes. Specific gravity testing is recommended to be conducted not only using representative waste composition, but also using representative compaction, stress, and degradation states.     

A two-generational reproductive toxicity study of zinc in rats

A two-generation reproductive toxicity study of zinc chloride (ZnCl₂) was conducted in rats. F_o male and female rats were administered 0.00 (control), 7.50 (low), 15.00 (mid) and 30.00 (high) mg/kg/day of ZnCl₂. Selected F₁ male and female rats were exposed to the same doses received by their parents (F_o). Exposure of F₀ parental rats to ZnCl₂ showed significant reduction in fertility, viability (days 0 and 4), and the body weight of F₁ pups from the high-dose group but caused no effects on litter size, weaning index, and sex ratio. Similarly, the continued exposure of F₁ parental rats to ZnCl₂ also reduced fertility, liter size, viability (day 0), and the body weight of F₂ pups within the high-dose group but caused no effects on weaning index and sex ratio. Exposure of ZnCl₂ to F₀ and F₁ parental males resulted in a significant reduction in their body weights, and the F₀ and F₁ parental females did not show any significant difference in their body weights compared to their control groups. However, the postpartum dam weights of both F₀ and F₁ female rats were significantly reduced compared to their controls. Exposure of ZnCl₂ to F_o and F₁ generation parental rats did not produce any significant change of their clinical signs as well as their clinical pathology parameters, except the alkaline phosphotase (ALK) level, which showed an upward trend in both sexes of both generations. Exposure of ZnCl₂ to F₀ rats resulted in a reduction of brain, liver, kidney, spleen and seminal vesicles weights of males and in the spleen and uterus of females. Similarly, exposure of F₁ rats to ZnCl₂ also resulted in reduction of brain, liver, kidney, adrenal, spleen, prostate and seminal vesicles weights of males and in spleen and uterus of females. ZnCl₂ exposure resulted in grossly observed gastro-intestianla (GI) tract, lymphoreticular/hematopoietic, and reproductive tract lesions in parental rats in both generations. Reduced body fat was also recorded in F₁ parental rats.     

Use of cholinesterase activity in monitoring chlorpyrifos exposure of steer cattle after topical administration

The aim of this work was to study the pharmacokinetic behavior and the inhibitory effect of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities of chlorpyrifos (CPF) in steer cattle after pour-on administration. Determination of cholinesterase activity in plasma and erythrocyte was carried out according to Ellman kinetic method. CPF was analyzed by gas chromatography. AChE was the predominant form of cholinesterase analyzed, with low levels of BChE in plasma. Following the treatment with CPF, the maximum inhibitory effect on AChE or BChE were 50.88 ± 11.57 and 42.66 ± 12.01%, respectively. The chlorpyrifos plasma concentrations observed were low and they presented a high variability. Chlorpyrifos peak plasma concentration (10.42 ± 4.76 μ g/L) was reached at 8.42 ± 13.97 h. The pesticide was not detected in plasma after 48 h post treatment. The values of area under the curve (AUC) were 118.48 ± 87.46 μ g· h/L and mean resistance time (MRT) were 13.38 ± 10.41 h. The pour-on exposure to the organophosphate chlorpyrifos significantly reduced AChE and BChE activity in steer cattle and the recovery was not reached on 50 days post-treatment.     

Chlortetracycline and tylosin runoff from soils treated with antimicrobial containing manure

This study assessed the runoff potential of tylosin and chlortetracycline (CTC) from soils treated with manure from swine fed rations containing the highest labeled rate of each chemical. Slurry manures from the swine contained either CTC at 108 μ g/g or tylosin at 0.3 μ g/g. These manures were surface applied to clay loam, silty clay loam, and silt loam soils at a rate of 0.22 Mg/ha. In one trial, tylosin was applied directly to the soil surface to examine runoff potential of water and chemical when manure was not present. Water was applied using a sprinkler infiltrometer 24-hr after manure application with runoff collected incrementally every 5 min for about 45 min. A biofilm crust formed on all manure-treated surfaces and infiltration was impeded with > 70% of the applied water collected as runoff. The total amount of CTC collected ranged from 0.9 to 3.5% of the amount applied whereas tylosin ranged from 8.4 to 12%. These data indicate that if surface-applied manure contains antimicrobials, runoff could lead to offsite contamination.     

Alterations in the rabbit lymphoid tissue after bendiocarb administration

Various pesticides have immuno-suppressive effects, and thus the organisms become responsive to viral, bacterial and parasitic diseases and neoplasm. The aim of the study was to observe the structure of the small intestine (height of enterocytes and crypts), mucosal lymphoid tissue (Payer's patches, lymphocytes in lamina propria) and a lymph node after administration of bendiocarb (2,2-dimethyl-1,3-benzodioxol-4-yl-methylcarbamate) on days 3, 10, 20, 30 and 60 of the experiment. The height of the observed enterocytes showed an increasing tendency. On days 20, 30 and 60 we also observed an increase in diameter of crypts located in intestinal epithelium. The number of cells in lamina propria mucosae was significantly reduced on days 20 and 30 after administration of bendiocarb. Observations of the lymph node showed that on days 10 and 20 there was a significant increase in relative volume of medulla at the expense of the relative volume of the cortex and a decrease in the number of lymphocytes. However, we recorded an increase in diameter of lymphocytes. The intracellular parasite Toxoplasma gondii (T. gondii) belongs to the most common pathogenic parasites in the world and it can cause serious health complications in pregnant and immunodeficient individuals. DNA isolation, standard polymerase chain reaction (PCR) and visualization in a 2.5 % agarose gel, the presence of DNA T. gondii was detected in no examined rabbit brain samples. Using real time PCR T. gondii DNA was detected and quantified in the three rabbit brain samples (10 %).     

Assessment of imidacloprid toxicity on reproductive organ system of adult male rats

In the current study it was aimed to investigate the toxicity of low doses of imidacloprid (IMI) on the reproductive organ systems of adult male rats. The treatment groups received 0.5 (IMI-0.5), 2 (IMI-2) or 8 mg IMI/kg body weight by oral gavage (IMI-8) for three months. The deterioration in sperm motility in IMI-8 group and epidydimal sperm concentration in IMI-2 and IMI-8 groups and abnormality in sperm morphology in IMI-8 were significant. The levels of testosterone (T) and GSH decreased significantly in group IMI-8 compared to the control group. Upon treatment with IMI, apoptotic index increased significantly only in germ cells of the seminiferous tubules of IMI-8 group when compared to control. Fragmentation was striking in the seminal DNA from the IMI-8 group, but it was much less obvious in the IMI-2 one. IMI exposure resulted in elevation of all fatty acids analyzed, but the increases were significant only in stearic, oleic, linoleic and arachidonic acids. The ratios of 20:4/20:3 and 20:4/18:2 were decreased and 16:1n-9/16:0 ratio was increased. In conclusion, the present animal experiments revealed that the treatment with IMI at NOAEL dose-levels caused deterioration in sperm parameters, decreased T level, increased apoptosis of germ cells, seminal DNA fragmentation, the depletion of antioxidants and change in disturbance of fatty acid composition. All these changes indicate the suppression of testicular function.