虾壳粉对水溶液中阴、阳离子型染料的吸附

采用废弃虾壳制备吸附剂处理含刚果红或亚甲基蓝的溶液。考察了温度、吸附时间、初始浓度、吸附剂投加量和初始溶液pH对吸附效果的影响并构建了去除率预测模型,并对吸附等温线、吸附动力学和吸附热力学进行系统研究。结果表明:虾壳粉对刚果红和亚甲基蓝的吸附分别在24 h和4 h时达到平衡,平衡吸附量随吸附时间、初始浓度及吸附剂投加量的增加而增大;刚果红平衡吸附量随pH升高而增大,亚甲基蓝平衡吸附量几乎不随pH变化。在15℃下,吸附剂投加量为1 g·L~(-1),刚果红吸附的最优条件为接触时间24 h、pH=4,在该条件下,虾壳粉对刚果红的饱和吸附量为276.64 mg·g~(-1);亚甲基蓝吸附的最优条件为接触时间4 h、pH=12,在该条件下,虾壳粉对刚果红的饱和吸附量为1.44 mg·g~(-1);虾壳粉对2种染料的吸附过程以物理吸附为主,符合准二级动力学方程。虾壳粉对阴离子型染料的吸附效果较优,对阳离子型染料有一定吸附性能,是一种经济高效的染料废水吸附材料。     

麦秆对水中扑草净的吸附性能研究

农业秸秆富含纤维素、木质素等组分,是良好的吸附材料。采用麦秆作为吸附剂,其对浮油及溶解油具有良好吸附效果。选用麦秆为吸附剂,探究其对扑草净的吸附效果。主要考察麦秆粒径、投加量、振荡频率、扑草净初始质量浓度4种因素对吸附的影响,研究麦秆对扑草净的吸附等温线和吸附动力学过程,并采用正交实验对影响吸附的因素进行优化。结果表明:(1)麦秆可有效降低废水中扑草净浓度,在振荡频率150r/min、麦秆粒径250~500μm、投加量0.500 0g、吸附300min时,扑草净初始质量浓度由5.20mg/L降至3.22mg/L,去除率为38.08%。(2)单因素吸附平衡实验表明,随麦秆粒径增加(150~4 000μm),其比表面积减小,平衡吸附量随之减小,麦秆粒径150~250μm时平衡吸附量为0.192 0 mg/g,显著大于1 700~4 000μm时的平衡吸附量(0.059 3mg/g);随麦秆投加量增加(0.100 0~1.000 0g),去除率随之提高,平衡吸附量与之相反,0.100 0g投加量时平衡吸附量为0.222 0mg/g;随着振荡频率加剧,麦秆在水中扩散增强,与扑草净碰撞几率增加,振荡频率250r/min时平衡吸附量为0.191 0mg/g;随扑草净初始质量浓度增加(1.03~6.18mg/L),平衡吸附量随之增加,初始质量浓度为6.18mg/L,平衡吸附量为0.226 0mg/g。(3)分别以Henry型、Langmuir型、Freundlich型吸附等温式进行拟合,资料表明,以Henry型吸附等温式较适宜描述该吸附过程。(4)采用伪一级动力学方程、伪二级动力学方程、Elovich经验方程、颗粒内扩散方程分析吸附动力学过程,以伪二级动力学方程较符合。(5)在振荡频率为150r/min、初始质量浓度为2.00mg/L、麦秆粒径为250~500μm、投加量为0.700 0g时,扑草净最佳去除率为47.80%。     

褐煤对废水中酸性红B的吸附去除

选用褐煤作为廉价吸附剂,脱除模拟废水中染料酸性红B。研究了褐煤对废水中酸性红B的吸附动力学、等温吸附模式,考察了pH、褐煤投加量以及离子强度(NaCl)对吸附效果的影响。结果表明,吸附动力学较好地符合准二级速率方程(R2=1.000),并且以化学吸附为主;吸附等温式满足Langmuir方程(R2=0.986),最大单分子层吸附量为42 mg/g;废水中染料的去除率随溶液pH的减小而明显增加,在pH=1时,去除效果最好,证实吸附过程存在静电吸引及化学键合;在一定条件下,溶液中酸性红B的去除率随褐煤投加量增加而增加;吸附效果随溶液中离子强度(NaCl)的增加而增强。说明褐煤可以作为一种廉价吸附材料,用于处理含染料废水。     

分子筛对水中Pb2+的吸附行为及回收利用

以4A和13X分子筛为吸附材料,考察了分子筛投加量、废水pH值、Pb2+初始浓度和吸附时间对去除率的影响。结果表明,4A和13X分子筛投加量为0.16 g/L,废水pH为5,Pb2+初始浓度为30 mg/L时,吸附10 min后Pb2+去除率达到95%以上。通过吸附等温线和吸附动力学方程拟合,4A和13X分子筛对Pb2+的吸附过程均符合Langmuir吸附模型和Lagergren二级速率方程,计算出的饱和吸附容量Q0分别为714.3 mg/g和684.9 mg/g,二级反应速率常数k2分别为8.9×10-4g/(mg·s)和7.1×10-5g/(mg·s)。4A分子筛沉降性能较好,适宜回收;经过4次吸附-解吸仍保持88.7%的Pb2+去除率和493.2 mg/g的吸附容量,经解吸后的浓缩液中富含铅离子720.3 mg/L,富集倍数3.78,加入Na2S生成硫化物沉淀能够达到回收金属铅的目的。     

硫酸活化市政污泥对亚甲基蓝的吸附

采用市政剩余污泥作为原料,以硫酸作为活化剂制备吸附剂,并将其应用到含亚甲基蓝废水处理中。系统地研究了溶液初始pH值、亚甲基蓝初始浓度和吸附时间等因素对硫酸活化市政污泥吸附性能的影响。研究结果表明,在吸附剂投加量2 g/L,pH7.5,温度293 K条件下,硫酸活化市政污泥对亚甲基蓝的最大吸附量为38.4794 mg/g。吸附动力学和热力学研究结果表明,吸附剂对亚甲基蓝的吸附过程可用准二级动力学模型(R2=0.9910)、Freundlich吸附等温式(R2=0.9935)来描述。颗粒内扩散速率也是其吸附反应限制因素,但不是惟一限制因素。该研究表明,硫酸活化剩余污泥可以作为含亚甲基蓝染料废水的处理材料。     

凹凸棒土对腐殖酸的低温吸附性能研究

首次研究凹凸棒土对饮用水中腐殖酸的低温吸附性能,考察5℃条件下,吸附时间与腐殖酸初始浓度、吸附剂投加量、pH对凹凸棒土吸附腐殖酸的影响,确定吸附剂的吸附等温线、吸附动力学和热力学等相关理论参数,研究凹凸棒土对腐殖酸的吸附性能与机理。结果表明,江苏盱眙凹凸棒土在温度5℃、pH=4、水中腐殖酸初始浓度为5 mg/L,投加量为15 g/L的条件下,吸附180 min后对腐殖酸的去除率可达97.26%。凹凸棒土对腐殖酸的吸附符合二级吸附动力学方程与Freundlich吸附等温式,吸附过程由孔隙内扩散过程控制,吸附为自发的吸热过程,包括物理吸附与化学吸附。根据Fre-undlich吸附等温式拟合计算,5℃、pH=7时理论最大吸附量为9 mg/g,说明凹凸棒土对于低温饮用水中腐殖酸具有良好的吸附效果。     

生物膜细菌藻酸盐对Cu2+的吸附动力学研究

以生物膜中提取的细菌藻酸盐为原料制备藻酸钙为吸附剂,对水溶液中的Cu2+进行了吸附动力学研究.试验结果表明,吸附时间、溶液初始pH和吸附剂投加量对藻酸钙吸附Cu2+影响显著.当溶液初始pH为4.0、Cu2+初始质量浓度为100 mg/L、吸附剂投加量为0.7 g/L时,藻酸钙对Cu2+的平衡吸附量为56.15 mg/g.水溶液中Cu2+在藻酸钙上的吸附动力学过程可用准二级动力学方程来模拟.吸附等温线研究表明,藻酸钙吸附Cu2+的过程可用Langmuir和Freundlich模型来描述.100 mmol/L 乙二胺四乙酸(EDTA)可有效解吸95.6%的Cu2+,实现Cu2+的回收与吸附剂的重复利用.     

非活性原始铜藻对水中Cr(Ⅵ)的生物吸附

以非活性原始铜藻(Sargassum horneri)(以下简称铜藻)为生物吸附剂处理含Cr(Ⅵ)废水,考察了溶液pH、铜藻投加量、Cr(Ⅵ)初始浓度、反应时间及温度对Cr(Ⅵ)去除效果的影响。结果表明,当pH在1~9时,pH越低时铜藻对Cr(Ⅵ)的吸附效果越好;降低铜藻投加量或增加Cr(Ⅵ)初始浓度均能提高铜藻对Cr(Ⅵ)的吸附容量,但会降低溶液中Cr(Ⅵ)的去除率。铜藻对Cr(Ⅵ)的吸附过程更遵循准二级动力学模型,且颗粒内扩散并不是该吸附过程的唯一速率控制步骤。Langmuir和Freundlich等温吸附模型均能较好地描述铜藻对Cr(Ⅵ)的吸附,20、30、40、50℃下铜藻对Cr(Ⅵ)的最大吸附容量分别为19.14、18.79、20.96、23.62mg/g。热力学分析显示,铜藻对Cr(Ⅵ)的吸附为吸热反应,可自发进行,升温可促进铜藻对Cr(Ⅵ)的吸附。此外,铜藻对Cr(Ⅵ)的吸附过程中物理吸附和化学吸附并存。     

磁性壳聚糖改性硅藻土吸附去除水中的铅离子

采用壳聚糖与Fe_3O_4对硅藻土进行混合改性,制备出一种吸附效果好、且能从液相中磁分离的新型复合吸附剂。通过SEM、XRD、VSM和FTIR等手段对其进行表征,并探究溶液pH、吸附剂投加量以及吸附温度等条件对水溶液中Pb~(2+)吸附效果的影响。结果表明:壳聚糖和Fe_3O_4都能够负载到硅藻土上面。当溶液pH为5、吸附剂投加量为10 g·L~(-1)、初始浓度为10 mg·L~(-1)时,Pb~(2+)去除率可以达到96.4%。吸附过程较好地符合假二级动力学模型和Langmuir吸附等温模型,热力学数据说明该吸附是吸热、自发的过程。     

改性玉米秸秆吸附Cu2+的动力学和热力学

本研究用ZnCl2作为活化剂,使用功率640 W的微波照射4 min的方法制备改性玉米秸秆。考察投加量、pH、吸附时间对吸附性能的影响,并对等温吸附特征、吸附动力学和热力学进行了系统研究。结果表明:投加量为0.2 g,pH为6,改性玉米秸秆对Cu2+具有很好的吸附效果,吸附在8 h后达到平衡。该吸附过程符合Langmuir及Freundlich等温吸附模型和准二级动力学方程,其反应的吉布斯自由能△G<0,为自发反应过程。     

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.