反硝化生物滤池深度脱氮机理

研究了反硝化生物滤池对污水中硝酸盐氮的脱氮机制及其影响因素。结果表明,在实验室小试条件下,反硝化生物滤池启动14 d后出水基本达到稳定,NO3--N和TN的去除率分别为80%～88%和76%～80%,COD的去除率达到80%以上。稳定运行期,在室温20～29℃、水力负荷为1.5～2 m3/(m2.h)、COD/TN为3.7～4.5的条件下,反应器对NO3--N和TN的去除率分别为70%～85%和47%～64%,且在运行过程中出现了少量NO2--N的积累。分析反硝化生物滤池沿水流方向有机物浓度及氮形态分布发现,沿水流方向NH4+-N浓度基本保持不变;NO2--N浓度在滤层底部至40 cm高处积累较为明显,其后浓度基本不变。     

天津津南污泥处理厂两段式PN/A工艺处理污泥脱水液的成功启动与运行分析

污泥脱水液的经济高效脱氮处理已成为污水处理中的重要环节.依托天津津南污泥处理厂采用两段式部分亚硝化/厌氧氨氧化(PN/A)脱氮工艺处理污泥脱水液,在35℃下,对工程规模的工艺启动和稳定运行特性进行了研究.结果表明:接种活性污泥可成功启动部分亚硝化(PN)反应器,PN反应器出水NO2--N/NH4+-N为1.1时,可实现...     

ASBR厌氧氨氧化反应器的快速启动及脱氮原理分析

以城市生活污水为基本水质进行配水,采用ASBR研究了厌氧氨氧化反应器的快速启动过程及脱氮性能。实验条件如下:T为(35±1)℃、HRT为24 h、pH为7.2～7.5,进水NH4+-N、NO2--N浓度为40～160 mg/L,TN负荷为0.08～0.34 kg TN/(m3.d),按2∶1比例混合接种好氧短程硝化污泥和厌氧氨氧化污泥,经49 d运行成功启动厌氧氨氧化反应器,并实现稳定运行。实验结果表明:稳定运行期NH4+-N、NO2--N去除率分别达96%和98%;NH4+-N、NO2--N去除量与NO3--N生成量比值为1∶1.05∶0.29,较为接近理论值;成功启动的反应器出水pH高于进水;系统TN去除率平均值为79.7%;反应器内存在反硝化与厌氧氨氧化的协同作用,实现了部分COD去除;污泥由深棕色絮状变成红褐色颗粒状,经SEM扫描电镜观察污泥菌群种类单一,多为球状菌,有漏斗状缺口,具有典型氨氧化菌形态特征。     

城市污水条件下ASBR厌氧氨氧化的启动与脱氮性能

采用ASBR在城市污水条件下进行厌氧氨氧化的启动与脱氮性能研究。实验接种好氧硝化污泥,在温度为(35±1)℃、HRT为24 h、pH为7.3～8.5的条件下经过130 d的培养,成功启动了厌氧氨氧化反应。实验结果表明,厌氧氨氧化反应稳定运行时,TN容积负荷平均为0.179 kg/(m3.d),NH4+-N、NO2--N和TN去除率分别达到了95.30%、91.30%和76.28%。启动期和稳定运行期NH4+-N、NO2--N去除量和NO3--N生成量的比值分别达到1∶1.54∶0.25和1∶1.27∶0.27;稳定运行期进出水pH差值由启动时的0.85下降到0.24。启动期反硝化和厌氧氨氧化反应同时存在而在稳定运行期厌氧氨氧化发展成为主导反应。MLSS和MLVSS/MLSS先减少后增加,反映了启动过程中硝化细菌、反硝化细菌的衰亡和厌氧氨氧化菌逐渐富集的过程,这与反应器的宏观运行效果相一致。     

琼脂碳源生物反硝化去除水源水中硝酸盐

针对受硝酸盐污染的水源水,以琼脂为反硝化细菌的碳源和微生物载体,通过生物反硝化作用脱除水源水中的硝酸盐,并利用曝气生物滤池(BAF)去除琼脂反应器出水中残留的少量CODMn和NO2--N等污染物。实验结果表明,水源水自然接种的条件下,可以顺利启动琼脂反应器;在温度为25℃左右,琼脂反应器在进水NO3--N约25 mg/L、水力停留时间1.5 h时,能获得70%的硝酸盐氮去除率;曝气生物滤池在水力停留时间0.5 h、气水比2.8时,可控制最终出水的CODMn和NO2--N分别在5.0 mg/L和0.10 mg/L以下;琼脂反应器的脱氮效果与温度、进水NO3--N浓度及水力停留时间等有关。研究指出,琼脂反应器与曝气生物滤池构成的组合系统能较好地脱除水源水中的硝酸盐并且能控制最终出水水质,不会导致二次污染,从而获得合格的饮用水源水。     

接种物对厌氧同步脱硫反硝化特性的影响实验研究

分别以厌氧污泥、脱氮硫杆菌菌悬液和厌氧污泥并添加脱氮硫杆菌菌悬液为接种物,以硫化物和硝酸盐为进水基质,考察不同接种物条件下,各反应器的硫化物氧化特性、反硝化特性、生化反应机理及微生物特性。结果表明,在无菌条件下,硫化物不能被硝酸盐化学氧化。接种脱氮硫杆菌菌悬液的2#反应器的硫氧化速率为1.98 g S/(m3.h),停留24 h硫化物的去除率高达97%,脱硫能力最强,该接种条件下以硝酸盐氧化硫化物为主反应,优势菌为杆菌,进水的NO3--N/S应控制在0.4以下,可以实现高效生物脱硫。接种厌氧污泥的1#和3#反应器的脱氮效果比2#反应器好,停留时间为24 h时,硝酸盐的平均去除率为96%。单独接种厌氧污泥的1#反应器的硫氧化速率为1.78 g S/(m3.h),其优势菌为球菌,该接种条件下以硝酸盐氧化硫化物和硝酸盐氧化单质硫为主反应,进水的NO3--N/S应控制在0.8左右。以厌氧污泥联合脱氮硫杆菌为接种物时,硫氧化速率为1.71 g S/(m3.h),反应器以硝酸盐氧化硫化物、硝酸盐氧化单质硫以及异养反硝化为主反应,驯化后优势菌为球形、卵圆形和短杆状,应控制进水NO3--N/S为1.2,可以实现同步脱硫反硝化,该工艺既可以用于含硫废水的处理,也可以用于C/N低的硝酸盐废水的处理。     

电极-生物复合反应器处理城市污水的初步研究

微生物固定在电极表面，电解水产氢与氧所营造的微环境在一定条件下对生物硝化／反硝化及吸／放磷产生了促进作用，使电极-生物复合反应器在脱除有机污染物的同时强化了生物的脱氮及除磷效果。本试验采用了2套结构与尺寸完全相同的单槽内循环反应器，1套通电，1套不通电，在不同电流强度下比较了2套反应器对污染物的去除效果。反应器中以石墨为阳极，活性炭纤维为阴极，电极-生物复合反应器的总氮去除率可比未通电流的反应器高出30％左右，总磷去除率增加11．5％，而氨氮、COD的去除率都维持在100％和95％左右。试验表明，电流的引入在一定条件下能明显强化生物反应器脱氮除磷效果。     

厌氧流化床微生物燃料电池同步除碳脱氮产电性能影响因素

研究了厌氧流化床微生物燃料电池(AFB-MFC)除碳脱氮产电性能的影响因素。结果表明:(1)AFB-MFC对NH4+-N的去除不起作用。电压下降主要是由于进水有机基质浓度下降造成。(2)不添加NO3--N时,在满足AFB-MFC脱氮所需的电子供体条件下增加进水COD/TN有利于AFB-MFC产电。(3)3种无机氮共存下,AFB-MFC在进水有机碳与无机氮质量比(C/N)不低于1.37时,对COD、NO2--N和NO3--N具有理想的去除效果。AFB-MFB在一定进水C/N范围内(1.37～2.50),能得到稳定的输出电压及功率密度。(4)固定进水C/N时,AFB-MFC在高碳氮负荷下仍能得到较理想的NO2--N、NO3--N、COD去除效果,AFB-MFC对NH4+-N去除效果不明显;增加碳氮负荷,AFB-MFC输出电压及功率密度没有明显的改变。(5)有机基质浓度不变下,AFB-MFC中充足的电子供体可保证较高的NO3--N、COD去除率。AFB-MFC输出电压及功率密度随着时间延长而先增加至稳定值后下降。     

厌氧氨氧化耦合部分反硝化处理低浓度氨氮废水

通过接种厌氧氨氧化菌(Candidatus Brocadia)与部分反硝化菌(Thauera)形成厌氧氨氧化与部分反硝化耦合处理模拟城镇污水中的氨氮(NH_4~+-N)与硝氮(NO3--N),考察不同NO3--N/NH_4~+-N比对耦合系统脱氮性能的影响及最佳NO3--N/NH_4~+-N比下耦合系统的稳定性和脱氮的途径。结果表明:在COD/NO3--N为2.5、NH_4~+-N浓度为20~40 mg·L~(-1)的条件下,NO3--N/NH_4~+-N比在0.8~1.6的范围内均可实现部分反硝化与厌氧氨氧化协同脱氮,且当NO3--N/NH_4~+-N比为1.2时,耦合效果最佳,对应的NH_4~+-N、NO3--N及总氮(TN)去除率分别为92.85%、99.68%和96.42%;厌氧氨氧化菌在耦合系统中的活性稳定在(4.62±0.44)mg·(g·h)-1(以VSS计),且与反硝化菌存在协同竞争关系,进水NO3--N的84.3%由厌氧氨氧化途径去除,15.7%由异养反硝化途径去除。     

一株施氏假单胞菌Pseudomonas stutzeri DN-LWX19的脱氮性能

从缺氧生物滤池筛选纯化得到一株具有高效反硝化能力的异养菌DN-LWX19,通过形态观察、生理生化特性及16S rDNA同源性分析,确定该菌株为施氏假单胞菌(Pseudomonas stutzeri).脱氮性能研究结果表明,菌株DN-LWX19在NO3--N初始浓度为120.43 mg/L的试管培养基中,60 h对NO3--N去除率达90％,NO2--N积累浓度仅0.05 mg/L.以添加适量乙酸钠的实际污水处理二级出水为液体培养基,研究DN-LWX19在初始NO3--N浓度约为30.00 mg/L时的脱氮效果,当碳氮比(COD/NO3--N)为5∶1时,菌株DN-LWX19在32 h对NO3--N去除率为100％,但是有NO2--N的积累(7.00 mg/L),且至72 h无明显变化;当碳氮比为9∶1时,菌株DN-LWX19在32h对NO3--N的去除率为100％,且无NO2-N的积累.     

Patterns of volatile metabolites and nonvolatile trichothecenes produced by isolates of <Emphasis Type="Italic">Stachybotrys,Fusarium, Trichoderma,Trichothecium</Emphasis> and <Emphasis Type="Italic">Memnoniella</Emphasis>

We reported previously that trichodiene, a volatile trichothecene derivative, was produced by a Stachybotrys isolate, also known to produce highly cytotoxic, non-volatile, macrocyclic trichothecenes (satrotoxins). We investigated the relationship between the production of trichodiene and various non-volatile trichothecenes for several molds. Volatile metabolites were concentrated by adsorption on Tenax TA and analyzed by GC/MS, while non-volatile metabolites were separated by HPLC, derivatized and analyzed by GC/MS. Stachybotrys chartarum isolates producing macrocyclic trichothecenes secreted significantly larger amounts of trichodiene and other sesquiterpenes than isolates which only produced simple trichothecenes. The amounts of secreted trichodiene were relatively small in all cases. With the exception of Memnoniella, which excreted small amounts of sesquiterpenes, the other isolates produced varying amounts of sesquiterpenes, including trichodiene, as well as simple tricothecenes, no detectable trichodiene, but large amounts of griseofulvin derivatives. In Stachybotrys there is apparently a correlation between trichodiene and macrocyclic trichothecene production. In the remaining isolates, there was no simple relationship between trichodiene and non-volatile trichothecene synthesis. Trichodiene is produced in larger amounts by Stachybotrys isolates, which also produce satratoxins, but it will be difficult to utilize this metabolite to detect toxic isolates in buildings due to the relatively small amounts excreted.     

Radionuclides and trace elements in fish collected upstream and downstream of Los Alamos national laboratory and the doses to humans from the consumption of muscle and bone

Abstract

The purpose of this study was to determine radionuclide and trace element concentrations in bottom‐feeding fish (catfish, carp, and suckers) collected from the confluences of some of the major canyons that cross Los Alamos National Laboratory (LANL) lands with the Rio Grande (RG) and the potential radiological doses from the ingestion of these fish. Samples of muscle and bone (and viscera in some cases) were analyzed for ³H, ⁹⁰Sr, ¹³⁷Cs, ^totU, ²³⁸Pu, ^239,240Pu, and ²⁴¹Am and Ag, As, Ba, Be, Cr, Cd, Cu, Hg, Ni, Pb, Sb, Se, and Tl. Most radionuclides, with the exception of ⁹⁰Sr, in the muscle plus bone portions of fish collected from LANL canyons/RG were not significantly (p<0.05) higher from fish collected upstream (San Ildefonso/background) of LANL. Strontium‐90 in fish muscle plus bone tissue significantly (p<0.05) increases in concentration starting from Los Alamos Canyon, the most upstream confluence (fish contained 3.4E‐02 pCi g^‐1 [126E‐02 Bq kg^‐1]), to Frijoles Canyon, the most downstream confluence (fish contained 14E‐02 pCi g^‐1 [518E‐02 Bq kg^‐1]). The differences in ⁹⁰Sr concentrations in fish collected downstream and upstream (background) of LANL, however, were very small. Based on the average concentrations (±2SD) of radionuclides in fish tissue from the four LANL confluences, the committed effective dose equivalent from the ingestion of 46 lb (21 kg) (maximum ingestion rate per person per year) of fish muscle plus bone, after the subtraction of background, was 0.1 ± 0.1 mrem y^‐1 (1.0 ± 1.0 μSv y^‐1), and was far below the International Commission on Radiological Protection (all pathway) permissible dose limit of 100 mrem y^‐1 (1000 μSv y^‐1). Of the trace elements that were found above the limits of detection (Ba, Cu, and Hg) in fish muscle collected from the confluences of canyons that cross LANL and the RG, none were in significantly higher (p<0.05) concentrations than in muscle of fish collected from background locations.     

A History of Dry Cleaners and Sources of Solvent Releases from Dry Cleaning Equipment

Approximately 25, 000-35, 000 dry cleaning facilities currently operate in the U.S. The release of perchloroethylene and other solvents from these establishments represents a major source of soil and groundwater contamination. The manner in which dry cleaning solvents escape from dry cleaning plants is, for all practical purposes, identical for chlorinated and petroleum hydrocarbon solvents and is related to one of the following events: the catastrophic failure of a component of the dry cleaning system, the improper installation, operation or maintenance of the dry cleaning equipment or a combination of all of these causes. Acceptable customs, codes and regulations can also dictate what is authorized for operation of a dry cleaning facility in a particular community, geographic area during a particular time frame. Environmental litigation dealing with the origin of a solvent release from dry cleaners tends to focus on the design and manufacture of dry cleaning industry machines such as washers, washer extractors, tumblers, solvent filters, water separators, stills and spotting boards. A thorough analysis of the daily operations of dry cleaners often reveals that poor maintenance, failure to follow the manufacturer's instructions and the actions of the operator are the most likely causes of soil and groundwater pollution. In order to forensically evaluate the most probable origins of a solvent release and to examine issues regarding liability, a thorough understanding of the history of dry cleaning and a detailed analysis of the operation and maintenance of the dry cleaning equipment are necessary. The discovery of solvent plumes in the vicinity of dry cleaning plants may suggest that the solvent source is the dry cleaning plant; however, the presence of these plumes does not necessarily indicate that the dry cleaning equipment was defectively designed or manufactured. A thorough review of the type of equipment used over the life of the dry cleaning plant and verifiable solvent mileage records frequently indicates that operators of the plant have disposed of solvent and contaminated solids into the municipal sewer or on ground surfaces.     

Radionuclides in deer and elk from Los Alamos national laboratory and the doses to humans from the ingestion of muscle and bone

Abstract

This paper summarizes radionuclide concentrations (³H, ⁹⁰Sr, ¹³⁷Cs, ²³⁸Pu, ^239,240Pu, ²⁴¹Am, and ^totU) in muscle and bone tissue of mule deer (Odocoileus hemionus) and Rocky Mountain elk (Cervus elaphus) collected from Los Alamos National Laboratory (LANL), Los Alamos, New Mexico, lands from 1991 through 1998. Also, the committed effective dose equivalent (CEDE) and the risk of excess cancer fatalities (RECF) to people who ingest muscle and bone from deer and elk collected from LANL lands were estimated. Most radionuclide concentrations in muscle and bone from individual deer (n = 11) and elk (n = 22) collected from LANL lands were either at less than detectable quantities (where the analytical result was smaller than two counting uncertainties) and/or within upper (95%) level background (BG) concentrations. As a group, most radionuclides in muscle and bone of deer and elk from LANL lands were not significantly higher (p<0.10) than in similar tissues from deer (n = 3) and elk (n = 7) collected from BG locations. Also, elk that had been radio collared and tracked for two years and spent an average time of 50% on LANL lands were not significantly different in most radionuclides from road kill elk that have been collected as part of the environmental surveillance program. Overall, the upper (95%) level net CEDEs (the CEDE plus two sigma for each radioisotope minus background) at the most conservative ingestion rate (50 lbs of muscle and 13 lbs of bone) were as follows: deer muscle = 0.22 mrem y^‐1 (2.2 μSv y^‐1), deer bone = 3.8 mrem y^‐1 (38 μSv y^‐1), elk muscle = 0.12 mrem y^‐1 (1.2 μSv y^‐1), and elk bone = 1.7 mrem y^‐1 (17 μSv y^‐1). All CEDEs were far below the International Commission on Radiological Protection guideline of 100 mrem y^‐1 (1000 μSv y^‐1), and the highest muscle plus bone net CEDE corresponded to a RECF of 2E‐06, which is far below the Environmental Protection Agency upper level guideline of 1E‐04.     

Leaching of seven pesticides currently used in cotton crop in Mato Grosso State—Brazil

This study aimed to evaluate the leaching of pesticides and the applicability of the Attenuation Factor (AF) Model to predict their leaching. The leaching of carbofuran, carbendazim, diuron, metolachlor, α and β endosulfan and chlorpyrifos was studied in an Oxisol using a field experiment lysimeter located in Dom Aquino – Mato Grosso. The samples of percolated water were collected by rain event and analyzed. Chemical and physical soil attributes were determined before pesticide application to the plots. The results showed that carbofuran was the pesticide that presented a higher leaching rate in the studied soil, so was the one representing the highest contamination potential. From the total carbofuran applied in the soil surface, around 6 % leached below 50 cm. The other pesticides showed lower mobility in the studied soil. The calculated values to AF were 7.06E-12 (carbendazim), 5.08E-03 (carbofuran), 3.12E-17 (diuron), 6.66E-345 (α-endosulfan), 1.47E-162 (β-endosulfan), 1.50E-06 (metolachlor), 3.51E-155 (chlorpyrifos). AF Model was useful to classify the pesticides' potential for contamination; however, that model underestimated pesticide leaching.     

Endosulfan in China 2—emissions and residues

Background, aim, and scope  Endosulfan is one of the organochlorine pesticides (OCPs) and also a candidate to be included in a group of new persistent organic pollutants (UNEP 2007). The first national endosulfan usage inventories in China with 1/4° longitude by 1/6° latitude resolution has been reported in an accompanying paper. In the second part of the paper, we compiled the gridded historical emissions and soil residues of endosulfan in China from the usage inventories. Based on the residue/emission data, gridded concentrations of endosulfan in Chinese soil and air have been calculated. These inventories will provide valuable data for the further study of endosulfan. Methods  Emission and residue of endosulfan were calculated from endosulfan usage by using a simplified gridded pesticide emission and residue model—SGPERM, which is an integrated modeling system combining mathematical model, database management system, and geographic information system. By using the emission and residue inventories, annual air and soil concentrations of endosulfan in each cell were determined. Results and discussion  Historical gridded emission and residue inventories of α- and β-endosulfan in agricultural soil in China with 1/4° longitude by 1/6° latitude resolution have been created. Total emissions were around 10,800 t, with α-endosulfan at 7,400 t and β-endosulfan at 3,400 t from 1994 to 2004. The highest residues were 140 t for α-endosulfan and 390 t for β-endosulfan, and the lowest residues were 0.7 t for α-endosulfan and 170 t for β-endosulfan in 2004 in Chinese agricultural soil where endosulfan was applied. Based on the emission and residue inventories, concentrations of α- and β-endosulfan in Chinese air and agricultural surface soil were also calculated for each grid cell. We have estimated annual averaged air concentrations and the annual minimum and maximum soil concentrations across China. The real concentrations will be different from season to season. Although our model does not consider the transport of the insecticide in the atmosphere, which could be very important in some areas during some special time, the estimated concentrations of endosulfan in Chinese air and soil derived from the endosulfan emission and residue inventories are in general consistent with the published monitoring data. Conclusions  To our knowledge, this work is the first inventory of this kind for endosulfan published on a national scale. Concentrations of the chemical in Chinese air and agricultural surface soil were calculated for each grid cell. Results show that the estimated concentrations of endosulfan in Chinese air and soil agree reasonably well with the monitoring data in general. Recommendations and perspectives  The gridded endosulfan emission/residue inventories and also the air and soil concentration inventories created in this study will be updated upon availability of new information, including usage and monitoring data. The establishment of these inventories for the OCP is important for both scientific communities and policy makers.     

Impact of spiked concentrations of Cd,Pb, As and Zn in growth medium on elemental uptake of Nasturtium officinale (Watercress)

This study is aimed at investigating the impact of water quality on the uptake and distribution of three non-essential and toxic elements, namely, As, Cd and Pb in the watercress plant to assess for metal toxicity. The plant was hydroponically cultivated under greenhouse conditions, with the growth medium being spiked with varying concentrations of As, Cd and Pb. Plants that were harvested weekly for elemental analysis showed physiological and morphological symptoms of toxicity on exposure to high concentrations of Cd and Pb. Plants exposed to high concentrations of As did not survive and the threshold for As uptake in watercress was established at 5 ppm. Translocation factors were low in all cases as the toxic elements accumulated more in the roots of the plant than the edible leaves. The impact of Zn on the uptake of toxic elements was also evaluated and Zn was found to have an antagonistic effect on uptake of both Cd and Pb with no notable effect on uptake of As. The findings indicate that phytotoxicity or death of the watercress plant would prevent it from being a route of human exposure to high concentrations of As, Cd and Pb in the environment.     

Butyltin compounds in sediment and fish from the Polish Coast of the Baltic Sea

Concentrations of mono- (MBT), di- (DBT), and tri-(TBT) butyltin compounds were measured in eggs, liver, and muscle of nine species of fish from four regions of the Baltic Sea - the Firth of Vistula, the Gulf of Gdańsk, Puck Bay, and the mouth of the Vistula River. The overall concentration ranges among all the fish sampled from the four sites were: < 7 to 79 ng/g for MBT, 6 to 1100 ng/g for DBT, 7 to 3600 ng/g for TBT, and 16 to 4800 ng/g for total BTs, on a wet wt basis. The highest concentration of total BTs was found in herring liver from the Firth of Vistula (4800 ng/g, wet wt) and in roach muscle from Puck Bay (3300 ng/g, wet wt), while the least concentration was found in burbot eggs and liver from the Vistula River (39 and 32 ng/g, wet wt, respectively). TBT was the major form of BTs present in most samples analyzed. Sediment samples collected from shipyards in the Gulf of Gdańsk contained butyltin concentrations ranging from 1.2 to 46 μg/g (dry wt) for MBT, 2.0 to 42 μg/g for DBT, and 2.6 to 40 μg/g for TBT. As with the fish, the majority of the BTs in sediment were present as TBT, which suggested recent exposure of the aquatic environment of the region to TBT.     

Malathion-induced sublethal toxicity on the hematology of cricket frog (Fejervarya limnocharis)

The effect of malathion [diethyl(dimethoxythiophosphorylthio)succinate] at sublethal concentration (0.006 ppm) on hematological parameters of the cricket frog (Fejervarya limnocharis) was studied for 24 hrs to 240 hrs of exposure and remarkable hematological alterations were observed. The study on hematological parameters revealed a highly significant decrease (P < 0.01) in the total erythrocytes count in malathion-exposed animals from 24 hours to 96 hrs of exposure as compared to control. Significant decreases (P < 0.01) of hemoglobin and packed cell volume were also observed from 48 hrs to 240 hrs. A significant increase (P < 0.01) in leucocytes count was noted throughout the exposure period. Elevated numbers of lymphocytes and eosinophils as found in the present study revealed lymphocytosis as well as eosinophilia, suggesting that this was a result of direct stimulation of the immunological defense due to the presence of a toxic substance or may be associated with tissue damage. The cytomorphological and cytopathological study of erythrocytes and leucocytes in malathion-exposed frogs at 0.006 ppm concentration revealed various cytotoxic effects at different exposure times. It was noted that the size and the shape of the erythrocytes were subjected to variation in different blood disorders.