There is a possibility that dredged sediments can be contaminated with heavy metals because of the recent industrial development and rapid population increase along the coastal regions of the world. Hence there is a need to examine the extent of contamination before disposal. In the present investigation, an attempt has been made to study the distribution of selected heavy metals in the dredged samples collected along such southern coastal regions of Singapore as Pasir Panjang Wharf, Marina Bay, and Empire Dock. The test results showed that heavy metals concentration in dredged spoil was low, and they can be categorized into uncontaminated/slightly contaminated levels. It is likely that the dredged spoil may be safely disposed of either for land reclamation or for geotechnical applications without further treatment.

A mathematical model based upon the diffusion concept was developed to study the leaching of metals from water treatment residuals. Laboratory leaching tests were conducted to study the factors affecting leaching and to obtain effective diffusion coefficients for the model proposed.

The objectives of this field study were to (1) remediate the contents of a pond containing petroleum refinery waste products, and 2) characterize the performance of the remediation effort in terms of changes in chemical concentration, toxicity of the waste material, and mobility of the remediated waste constituents. The study was conducted in a field land treatment unit (LTU) in two phases over 140 weeks. Site remediation and closure decisions should be based on criteria that indicate that protection of human health and the environment has been achieved. Thus, criteria used to determine performance should include measures of chemical loss as well as measures of mobility (leaching) and toxicity. In this field study, changes in both general (oil and grease, total petroleum hydrocarbons) and specific (benzene, toluene, ethylbenzene, and xylene compounds and polycyclic aromatic hydrocarbons) hydrocarbons were determined. Several measures of chemical mobility and LTU soil toxicity also were used. The data indicated that the land treatment of this waste material reduced the concentrations of general and specific hydrocarbons, reduced the toxicity of the material being treated, and contained the waste constituents, that is, little to no vertical migration of the chemicals measured occurred. At the end of both field phases of the study, considerable amounts of general hydrocarbons remained in the LTU soil, as indicated by total petroleum hydrocarbons, oil and grease, and total polycyclic aromatic hydrocarbon compound measurements. However, there were little chemical mobility and relative toxicity of the soil at the end of these phases.

The aim of this article is to present a probabilistic way of determining the cumulative effect of various elements in the air, such as NOx, SO₂, and respirable particulate matter (RPM), that affect the human health. In the past, mostly deterministic models were developed for this purpose, which would test the response of the subject to known amounts of increasing doses. This dose-response curve would reflect the response of the subject only for a particular contaminant like CO, RPM, or NOx. However, most industrial sites are contaminated with several of these pollutants, with some or all of them affecting the workers in a very complex manner. So a new dose-response curve must be constructed that would take into account the effects due to multiple contaminants, i.e., the effect of several contaminants acting at the same time. This dose-response curve has to be constructed for each different set of independently acting variable. With the development of high speed computers, simulation can be used to develop a comprehensive risk analysis model (RAM) for studying the effect of these contaminants. The RAM is developed for an open pit mine using the Monte Carlo simulation technique and tested against the data obtained. The guiding principle in this project is that the effect of various contaminants, acting independently, is the sum of the individual effects put together; i.e., the effects due to a contaminant are independent of the presence of other contaminants. While the writers suggest a change in the probabilistic risk due to changing ambient concentrations of various pollutants, they stop short of pinpointing any resulting disease or disease-related symptoms.

Batch experiments have been carried out to study lignin removal from pulp and paper mill effluent by adsorption onto blast furnace flue dust from a steel plant and slag generated in a chrome alloy plant. Removal efficiencies attained after 8 h were observed to be more than 80% and 60% for the blast furnace flue dust and slag, respectively. The adsorption processes for both adsorbents follow first-order kinetics and Freundlich adsorption isotherms, decreasing with the increasing pH and temperature. Intraparticle diffusion studies indicate that adsorption of the substrate takes place rapidly by external mass transfer, followed by intraparticle diffusion. Column experiments indicate that the absorbed amount of lignin decreased with increasing flow rate and decreasing bed height. The break through time and bed depth data showed the applicability of the bed-depth service time model.

A sample of lithium antimonide (Li₃Sb) was prepared in a radioactive helium-atmosphere glove box, some of which spread throughout the box. Because of the potential for stibine generation should the Li₃Sb contact water, some effort was devoted to assessing the extent of possible stibine formation and methods for removing the Li₃Sb from the box. This note summarizes our findings and the waste disposal procedures used.