Preliminary toxicity evaluation of water from rice fields using cost‐effective microbiotests

A study was performed in a Protected Area (Natural Reserve of Sado Estuary) in 1996, to evaluate the acute toxicity for aquatic life of surface water from rice fields treated with pesticides, particularly with molinate and quinclorac. As a preliminary assessment, the following rapid toxicity tests were used: “Rotoxkit F”;, “Thamnotoxkit F”; and the recently introduced “Daphtoxkit F magna”; and “Algaltoxkit F”;. Water samples were collected from: a water source for irrigating the rice fields, two rice plots, a drainage channel and from Sado river in which the water is discharged. The results showed that samples from the rice plot treated with molinate were more toxic than those obtained from rice plot treated with quinclorac. Water samples from the river were the most toxic, causing 100% of immobility in all organisms and a substantial inhibition in the algal growth. Water collected from the drainage channel in late July, was also found to be quite toxic. The results obtained until now indicate that some characteristics of these microbiotests, like their rapidity, simplicity and relatively low cost, make them a practical tool to evaluate acute effects of pesticides in freshwater ecosystems. They may also contribute to suggest some changes in pesticides use to promote agricultural practices with lower impact to aquatic life.     

Effect of agrochemicals on earthworms

This review describes the toxic effects of agrochemicals on earthworms. Carbamates are described as extremely toxic to earthworms in comparison to organophosphorus insecticides. Some pesticides have drastic effect on the nervous system of the earthworm. Earthworm can accumulate heavy metals from the soil in higher levels than any other animal. Mercury is twenty times more toxic than chromium.     

Comparative Toxicities of Polar and Non-Polar Organic Fractions From Sediments Affected By the Exxon Valdez Oil Spill in Prince William Sound,Alaska

Abstract

Standardized tests were applied to aromatic and polar fractions of sediment extracts to determine whether polar constituents or oxidative degradation products contributed significantly to the toxicity of sediments oiled by the Exxon Valdez spill. Intertidal sediment and pore-water samples were collected in September 1990 from two heavily oiled sites and an unoiled site in Prince William Sound (PWS). Methylene chloride extracts from these samples were fractionated by liquid chromatography into aliphatic, aromatic and polar fractions, and the aromatic and polar fractions were tested for toxicity using the Microtox^R test, bivalve larval mortality and development (Mytilus); several measures of genotoxicity in Mytilus, including SOS Chromotest^R, anaphase aberrations and sister chromatid exchange; and survival, anaphase aberrations and teratogenicity in coho salmon (Onchorhynchus kisutch). Microtox^R and SOS Chromotest^R protocols were applied in a screening mode to all samples, whereas other tests were applied only to selected fractions from two sites. Samples from Bay of Isles (oiled) were consistently more toxic (usually only 2 to 5-fold) than the Mooselips Bay (unoiled) samples, which gave very low responses in all tests. for both sites, however, responses to polar and aromatic fractions were about the same in most tests, suggesting that while the overall toxicity of the oil was low in these samples, at least part of that toxicity was derived from polar constituents. Compared to the parent hydrocarbons, polar oxidation products partition preferentially into pore-water and are more rapidly diluted and dispersed in the water column. These results suggest that polar oxidation products of petroleum hydrocarbons pose little risk to marine organisms, except possibly for infauna continuously exposed to pore-water in heavily oiled sediments. Independent surveys showed that sediment toxicity in PWS declined during 1989–1991 to near background levels, in accord with previous understanding of oil weathering and toxicity.     

Biodegradation kinetics of cymoxanil in aquatic system

A potential method to detoxify pesticides in aquatic system is using bioremediation. In this study, four microorganisms (Pseudomonas sp (EB11), Streptomyces sp. (EB12), Aspergillus niger (EB13) and Trichoderma viride (EB14) were isolated from cucumber leaves previously treated with cymoxanil using enrichment technique. These strains were evaluated for their potential to detoxify cymoxanil in aquatic system at the concentration level of 5×10^?4M. The effect of pH and temperature on the growth ability of the tested strains was also investigated by measuring the intracellular protein and mycelia dry weight for bacterial and fungal strains, respectively. Moreover, the remaining toxicity of cymoxanil after 28 days of incubation with tested strains was evaluated to confirm the complete removal of any toxic materials (cymoxanil and its metabolites). The results showed that the optimum pH for the growth of cymoxanil degrading strains (bacteria and fungi) was 7. A temperature of 30°C appears to be the optimum for the growth of either fungal or bacterial strains. Pseudomonas sp. (EB11) was the most effective strain in cymoxanil degradation followed Streptomyces sp (EB12), Trichoderma viride (EB14) and Aspergillus niger (EB13), with half-lives of 4.33, 9.5, 17.3 and 24.7 days, respectively. The degradation of cymoxanil by bacterial strains was much faster than fungal one. There is no remaining toxicity of cymoxanil detected in aqueous media previously treated with Pseudomonas sp. (EB11) for 28 days. The results suggest that bioremediation by Pseudomonas sp. (EB11) are promising for the detoxification of cymoxanil in aqueous media.     

Bioaccumulation and toxic effects of copper on growth and oxygen consumption by the postlarvae of Penaeus indicus

The aim of this study was to assess the toxic impact of copper on postlarvae (PL) of the penaeid shrimp Penaeus indicus. Tolerance, growth, oxygen consumption and metal accumulation were investigated in these PL on exposure to copper. Tolerance studies were conducted for 96 h to assess the tolerance limits of P. indicus PL exposed to different concentrations of copper using static renewal bioassay tests. Using the Probit method, the regression equation was calculated as Y=0.4899+2.3562 X, with a correlation coefficient of 0.9707. The 96 h LC₅₀ was 0.8204 ppm. The effect of sublethal (one-fifth of 96 h LC₅₀) copper on PL for short- and long-term exposures revealed a significant (p<0.05) decrease in the rate of oxygen consumption, metabolic rate, mean length, wet and dry weight of the exposed PL over their respective controls which can be attributed to a gradual and time-dependent accumulation of the metal, as noticed in the exposed PL through accumulation studies. Overall, the data suggest that on chronic exposure even sublethal concentrations of copper can reduce the metabolic rate and growth in P. indicus PL. This is perhaps the first attempt to use the wild P. indicus PL as a bioindicator of copper toxicity.     

Protein Metabolic Response to Carbon Tetrachloride in A Freshwater Fish,Sarotherodon Mossambicus

Exposure of a freshwater teleost, Sarotherodon mossambicus, to a sublethal concentration (26 ppm) of carbon tetrachloride for periods up to 30 days led to significant changes in the soluble protein fractions (albumin and globulins) and free amino acid content. the decrease in total protein content was greater in liver than in muscle. the protein loss was expected due to the impairement of protein synthetic activity during stress conditions.     

微囊藻毒素-LR对雄性黑斑蛙精巢中CYP46A1,CYP2H2和CYP2G1 mRNA表达的影响

微囊藻毒素-LR(microcystin-LR,MC-LR)是分布最广泛和毒性最强的一种微囊藻毒素,对水生动物造成潜在的健康威胁。大量科学研究证实,动物体中的细胞色素P450酶(CYP)参与内源性物质及外源毒性物质的代谢过程。为探究两栖动物生殖器官中的CYP酶对低剂量MC-LR生殖毒效应的调节作用,选择雄性黑斑蛙(Rana nigromaculata)为受试动物,采用静态置换法和体内暴露方法,分别暴露于0、0.1、1和10μg·L~(-1)MC-LR溶液0、7和14 d;用实时荧光定量PCR方法检测精巢中CYP46A1、CYP2H2和CYP2G1的mRNA表达水平。结果表明,暴露于0.1、1和10μg·L~(-1)MC-LR 14 d后,CYP46A1在mRNA水平分别上调了1.86、1.65和1.22倍,CYP2H2在mRNA水平分别上调了4.62、1.80和1.04倍,CYP2G1的mRNA水平分别上调了2.63、2.16和1.56倍。MC-LR在1μg·L~(-1)剂量下暴露7 d后,CYP46A1、CYP2H2和CYP2G1 mRNA水平均出现显著上调。上述研究表明,微囊藻毒素对黑斑蛙精巢3种CYP基因在mRNA水平上都存在低剂量刺激效应。低剂量MC-LR能诱导黑斑蛙精巢中CYP46A1转录水平变化,促进胆固醇转化为24S-羟化胆固醇,潜在破坏雄性黑斑蛙精巢中胆固醇水平的平衡; MC-LR也能够诱导精巢中CYP2H2和CYP2G1转录水平的变化,潜在调节CYP2H2和CYP2G1转录水平,进而影响MC-LR的代谢作用。     

家用洗衣粉中磷对斜生栅藻生长的影响

以洗衣粉中的有机磷为磷源,通过室内模拟的方法研究在不同磷浓度的水体条件下斜生栅藻的生长情况,以及磷对斜生栅藻的生长是否有毒害作用.通过显微计数测定藻细胞数目来探讨洗衣粉中磷对斜生栅藻生长的影响;同时分析了洗衣粉中磷对斜生栅藻96 h生长期中光合色素的影响.结果表明,洗衣粉中的磷除了促进藻生长外,其浓度过低或过高都会抑制藻的生长.由实验结果可得,磷对藻生长的富营养化作用和毒性作用取决于磷浓度的高低.     

Environmental fate and ecotoxicology of propanil: a review

The herbicide propanil, a synthetic anilide, was discovered in 1957 to control grasses and broad-leaf weeds in rice fields. It has been found to disrupt the electron transport chain by inhibiting the photosystem II, thus impacting plant growth. In the environment, photolysis represents a major degradation pathway, whereas volatilization is not a major route of dissipation from either water or moist soils. Propanil is rapidly degraded by microbes into the major degradation product 3,4-dichloroaniline. This degradation product has been highly detected in both groundwater and surface waters throughout the world. Propanil has been found to adversely impact many non-target organisms. It is toxic to some early life-stage aquatic organisms, in addition to being moderately toxic to the water flea (Ceriodaphnia dubia) and rainbow trout. In addition, it has been reported to pose a high acute and long-term risk to birds. In plants, growth rates are highly impacted; however, some plant species are becoming resistant to propanil.