Antagonism and synergism between lead and zinc in amphibian larvae

Lead and zinc effects on Bufo arenarum larval survival were studied in single and combined treatments. On a weight basis, lead is about twice as toxic as zinc. The antagonism or synergism between these heavy metals is dose-dependent.     

Disappearance of bromopropylate residues in artichokes, strawberries and beans

Residues of Bromopropylate were determine in artichokes, strawberries and beans after foliar spray of acaricide at two rates. The rates used were 1 g/l formulated product (normal recommended) and 1.5 g/l. The residue levels of bromopropylate in the three crops after 14 days were lower than 0.7 ppm and did not exceed the Maximum Residual Level (MRL) recommended by FAO. In the artichokes and strawberries, the total concentration of residues decreased by 50% of the initial level after 2-3 days. Only trace levels of the bromopropylate residues (less than 0.01 ppm) were detected in the "hearts" of the artichokes. Bromopropylate residues in the green beans were also less than 0.8 ppm after the first day of foliar spraying. The kinetic of degradation occurred in two different steps. In the first step (4-6 days) the dissipation of bromopropylate was faster whereas in the second step (7-14 days) the loss of residues was much slower.     

Effect of methyl mercuric chloride treatment on haematological characteristics and erythrocyte morphology of Swiss mice

Effects of methyl mercuric chloride (MMC) on the blood parameters of Swiss mice (Mus musculus) were studied. The mice received an initial dose of MMC (24 mg kg(-1) body wt) as intraperitoneal injection followed by a second similar dose on the 14th day of the first dose administration. Significant (p < or = 0.001) decreases in haemoglobin content, red blood cell (RBC) count and haematocrit value were observed in the MMC injected mice when compared to the control mice. The effect of the second dose was severe, after which no significant recovery in the values of these parameters was observed. The result also showed a high degree of mercury accumulation in the blood of the MMC exposed mice. Interesting features were marked in the erythrocyte morphology of the exposed mice. An initial shrinkage followed by swelling of the cells was observed after each injection. The outline of the exposed cells was irregular with beak like or small finger like projections. Rupturing and disintegration of the erythrocyte membrane, leading to erythrolysis, were also noticed.     

The influence of pH on cadmium toxicity to the green alga Stichococcus bacillaris and on the cadmium forms present in the culture medium

Cadmium toxicity to the green alga Stichococcus bacillaris was investigated in media of pH 3-9. A significant decrease of cadmium toxicity occurred in both the acidic and alkaline ranges of pH. In media of pH 3 and 9, cadmium did not affect the dry mass content substantially. Maximum toxicity of cadmium was noticed at pH 6-7. Voltametric investigations showed a significant effect of pH on electrochemically measured cadmium content in the culture media. Hydrolysis of the medium components and formation of cadmium complexes with OH(-) ions caused a considerable decrease in amounts of electrochemically measured cadmium in the alkaline range of pH.     

Air Pollution in Singapore: Its Multielemental Aspect as Measured by Nuclear Analytical Techniques

Aerosol samples were collected in 1994 in Singapore on two occasions: once in June during the normal meteorological conditions and later in October during a long haze period caused by the heavy forest fire in Indonesia. Filtration and impaction collection methods were used simultaneously so that detailed elemental analysis of bulk as well as of different size fractions could be performed. Accelerator based nuclear analytical techniques such as Particle Induced X-Ray Emission (PIXE), Rutherford Backscattering (RBS) and Nuclear Microscopy (NM) were used for analysis. These techniques are fast, truly multielemental and perfectly suited for routine analysis of a large number of aerosol samples. Typically all samples were analysed for the following 24 elements: Na, Mg, Al, Si, P, S, Cl, K, Ca, Ti, V, Mn, Cr, Fe, Co, Ni, Cu, Zn, Ga, As, Br, Rb, Sr and Pb. Detection limits for bulk analysis were generally below ng/m3 and for single particle analysis absolute detectable mass was approximately 10-17 g. Additionally, trace elements such as Cd, Sn, Sb and Ba whose characteristic X-ray lines were normally "obscured" by the lines of other more abundant elements, were detected when analysing by nuclear microscope in single particle mode.Judging by the average concentrations of lead and sulphur which are good indicators of industrial component of air pollution the situation in Singapore is satisfactory. Pb was typically found in concentrations of 5 to 50 ng/m3 and sulphur in concentrations of 1 to 2 µg/m3. These concentrations are well below limits set by the World Health Organisation (1500 ng/m3 and 40 µg/m3, respectively). On the other hand during the haze period the average concentrations of elements like S, K, Ti, V, Mn, Ni, As and Pb were found to be 3 to 6 times higher than usual. Results are presented and discussed.     

Laboratory and Field Assessment of Arsenic Testing Field Kits in Bangladesh and West Bengal, India

High concentrations of arsenic in ground waters in West Bengal and Bangladeshhave become a major cause for concern in recent years. Given the enormity and the severity of the problemof arsenic poisoning, a task of evaluating the commercially available arsenic detection field kits for their capabilities was undertaken. In the light of the findings, generic specificationswere recommended which could form the basis forindigenous manufacture of these kits in the arsenic affected countries. This article presents the results of the laboratory and fieldevaluation conducted in Bangladesh and West Bengalof five arsenic testing field kits. The salient features of the kits, their merits and limitationshave been brought out. Based on the criteria of kitdesign, quality of chemicals used, colourcomparator charts, detection range, time required for analysis, cost etc., a comparative ranking ofthe kits has been made to facilitate the choice of the kit to meet specific requirements.     

Reduction and avoidance of lubricant mist demands an integrated assessment approach

A case study to identify major factors for lubricant mist exposure covered 15 metal machining sites. The investigation included milling, turning, drilling and grinding applications. Systematic analysis considered all relevant data concerning the machine tool, the lubricant and the suction plant. The efficiency of the implemented maintenance program at the installed filter systems was checked by concentration measurements immediately before and after service. All performed measurements of lubricant aerosol and vapor loads upstream and downstream of the installed filter systems were carried out according to VDI 2066 and BIA 3110, respectively. The selection criteria for the sites to be investigated, the systematic nature of the data acquisition and the procedure of the analysis are demonstrated in detail by performing comparisons between selected applications using emulsions and those employing straight oil for lubrication. The results of the study identify recirculation of ventilated air as the major source of workplace exposure to airborne lubricant emissions. More than 60% of the demisters investigated emit air at total lubricant loads (aerosols and vapor) above the limit of 20 mg m-3 at any time of operation; which also means immediately after service. A common reason for exceeded aerosol loads in recirculated air is e.g. the fact that the type of filter system applied is often not suitable for the separation problem. Loads of lubricant vapor are usually higher at the processes which use water emulsions as lubricant. In a quarter of the cases the limits were exceeded solely due to high vapor loads even immediately after service. The exposure can be reduced by replacing the lubricant, installation of a vapor separation plant or avoiding air recirculation. Maintenance time of the demisting system and aerosol separation efficiency of state-of-the-art demisting systems can be expanded by implementation of enhanced preliminary filter stages. This study confirms that appropriate service measures lower both aerosol emissions and lubricant vapor concentrations due to the reduction of exposed oil-wetted surfaces. The performed measurements show no significant relationship between loads of airborne lubricants and the type of machining process. Therefore, investigations at a much more detailed level have to be performed. However, the individual assessment of any workplace due to the complex situation remains essential.     

Cumulative impact assessment in environmental planning: A coastal wetland watershed example

Several theoretical, analytical, and institutional difficulties have impeded the development and application of the assessment of cumulative environmental impacts. Watershed development on coastal wetlands offers an ideal context for evaluating the land disturbance target approach to cumulative impact assessment. A model land use planning system involving a time series approach was developed for Elkhorn Slough in California. The approach included four major components: evaluation of erosion susceptibility, measurement of land disturbance, establishment of a land disturbance target, and a comparison of existing and target land disturbance values. Further research is needed to test the transferability of the approach in a wide range of coastal watersheds and to verify the applicability of the methods to other cumulative impact problems.     

Speciation of arsenic using solid phase extraction cartridges

Various solid phase extraction (SPE) cartridges were investigated for speciation of arsenite [As(III)], arsenate [As(v)], monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA). Cartridges containing different types of sorbent materials were tested for arsenic retention and elution characteristics. Alumina cartridges were found to completely retain all the four target arsenic species, and are suitable for removal and preconcentration purposes. For speciation analysis, different arsenic species were separated on the basis of their selective retention on and elution from specific cartridges. DMA was retained on a resin-based strong cation exchange cartridge and eluted with 1.0 M HCl. MMA and As(v) were both retained on a silica-based strong anion exchange cartridge and sequentially eluted with 60 mM acetic acid (for MMA) and 1.0 M HCl [for As(v)]. As(III) was not retained on either cartridge and remained in solution. Arsenic species in solution and those eluted from the cartridges were subsequently quantified by using flow injection with hydride generation atomic fluorescence spectrometry (FI-HGAFS) and hydride generation atomic absorption spectrometry (FI-HGAAS). A detection limit of 0.05 microg L(-1) arsenic in water sample was achieved using HGAFS. An application of the method was demonstrated at a drinking water treatment facility. As(III) and As(v) species were determined in water at various stages of treatment. The method is suitable for routine determination of trace levels of arsenic in drinking water to comply with more stringent environmental regulations.     

Multi-objective, decision-based assessment of a water quality monitoring network in a river system

Water quality monitoring network design has historically tended to use experience, intuition and subjective judgement in locating monitoring stations. Better design procedures to optimize monitoring systems need to simultaneously identify significant planning objectives and consider a number of social, economic and environmental constraints. The consideration of multiple objectives may require further decision analysis to determine the preference weights associated with the objectives to aid in the decision-making process. This may require the application of an optimization study to extract such information from decision makers or experts and to evaluate the overall effectiveness of locating strategies. This paper assesses the optimal expansion and relocation strategies of a water quality monitoring network using a two-stage analysis. The first stage focuses on the information retrieval of preference weights with respect to the designated planning objectives. With the aid of a pre-emptive goal programming model, data analysis is applied to obtain the essential information from the questionnaire outputs. The second stage then utilizes a weighted multi-objective optimization approach to search for the optimal locating strategies of the monitoring stations in the river basin. Practical implementation is illustrated by a case study in the Kao-Ping River Basin, south Taiwan.