A simple simulation of adsorption equilibrium of Pb(II) on Andosols in the presence of dissolved humic substances for monitoring soil contamination.

The adsorption equilibrium of Pb(II) on Andosols was investigated and described quantitatively in order to develop a simple method for the rapid monitoring of heavy metals in soils. The effect of solution pH on adsorption isotherms was investigated experimentally and in simulations. At pH 7, the considerable desorption of Pb(II) due to the extensive dissolution of humic substances (HS) from soils into aqueous phases is known to be an obstacle to carrying out simulations. In batch experiments, the total organic carbon (TOC) of the aqueous phases was shown to be enhanced by the addition of pre-extracted HS to soil suspensions. By combining the ion-exchange and Freundlich models, the adsorption equilibriums of free Pb(2+) ions and Pb(2+)-HS were simulated and were shown to be in good agreement with the experimental results. By estimating the concentrations and adsorption amounts of Pb(2+) and Pb(2+)-HS from measured CPb and TOC, it is possible to accurately simulate the soil contamination status even in in the presence of dissolved HS in the water in the solid-liquid extraction samples.

Application of biological safety index in two Japanese watersheds using a bioassay battery.

In order to integratedly evaluate the biological safety as a water quality index, an assessment method based on three toxicity tests (algae growth inhibition, daphnia immobilization and larval fish toxicity) was developed. In this study, the developed method was used to screen, evaluate and rank the biological safety of small rivers near agricultural, industrial and residential areas. Twenty-seven representative water samples were collected from the Kaname River watershed and the Hinata River watershed in Kanagawa Prefecture, Japan. The results indicated that (1) the biological safety of water from the Hinata River ranked much higher than those from the Suzu River and the Shibuta River due to less human activities, (2) the biological safety from outlets of paddy fields ranked much worse than those from point source discharges of toxic pollutants, (3) the use of pesticides significantly affected the water quality of nearby small rivers and ditches during the pesticide application season, (4) the effects of different kinds of pesticides could successfully be classified using one toxicity test component of the bioassay battery, and (5) there was no significant quantitative relationship between the toxicity and dissolved organic carbon (DOC) for the studied water samples. The toxicities of water samples in this study were in agreement with the concentrations of pesticides determined with chemical methods by other researchers, which demonstrated that the developed assessment method was reliable to screen site contaminated with organic chemicals for priority management.

Analysis of the toxicity-weighted release amount ranking of PRTR chemicals in Japan.

In this study, toxicity data were first collected for 184 chemicals from reliable information sources. After a validity check and analysis of these data, reference concentrations (RfC) were determined. The toxicity-weighted release amount (TWR) was then calculated for each chemical by dividing the release amounts by the RfC. Three types of TWR were derived, namely TWR(atm) for human health protection in the atmosphere, TWR(wat) for human health protection in water, and TWR(aq) for aquatic life protection. Thus, TWR could be proposed as a new index for environmental risk management considering both toxicity and release amount. Based on the TWR values, chemicals were ranked according to their potential risk upon release. The ranking results revealed that acrolein, formaldehyde, 1,3-butadiene, and arsenic are among the substances with the greatest risk to human health protection in the atmosphere; acrylonitrile, hydrazine, and pyridine are among those detrimental to human health protection in water; and polyoxyethylene alkyl ether (POAE), n-alkylbenzene sulfonic acid (LAS), and N,N-dimethyldodecylamine N-oxide are those identified as posing a risk to aquatic life protection. Moreover, for higher TWR chemicals, the contribution of each release source has been analyzed and discussed. For example, POAE and LAS are released mainly from households, and therefore efforts to reduce their concentration in the environment should focus on the sewage system. Formaldehyde and 1,3-butadiene are mainly emitted from mobile sources and, therefore, traffic should be evaluated as an important release source of toxic chemicals besides many stationary sources. Acrylonitrile and arsenic are released mainly by a few specific industries, placing the emphasis on the need for responsible care by the individual companies involved.

Environmental management of pesticidal POPs in China: past, present and future.

China, the largest developing country in the world, has been undergoing rapid economic growth in the past two decades. Synchronously, large quantities of persistent organic chlorinated pesticides have been used in agriculture and non-agriculture areas. Accompanying with incomplete management framework, the improper use and disposal of pesticides have caused serious pollution problems. In this study, we discussed: (1) ten persistent organochlorine pesticides in terms of historical production, consumption and number of manufacturers, import and export; (2) the current management framework of pesticidal persistent organic pollutants (POPs) with respect to legal system and government administrative system; (3) the existing problems in the management of pesticidal POPs; and proposed recommendations for countermeasures. Based on the available information, it can be concluded that records on the historical production and consumption quantities of pesticidal POPs are incomplete which makes a difficulty in the management. Although China has come a long way in developing a modern legal system, the current system is still considered weak and inefficient; and many challenges are ahead. The government administrative system has also been reformed and improved, but over-lapping jurisdictions still exist and are ineffective in managing pesticidal POPs program. To address these existing problems in pesticidal POPs management, it was suggested that more investigations should be conducted to collect information on pollution sources of pesticidal POPs, to evaluate their environmental risks, to identify new alternative chemicals and to complete management framework of pesticidal POPs in China. Furthermore, the public should be encouraged to participate in managing hazardous pesticidal POPs in China, and international cooperation and communication should be established and strengthened imperatively as well.

Evaluating the fish safety level of river water and wastewater with a larval medaka assay.

A larval medaka (Oryzias latipes) assay was proposed to evaluate the fish safety level of river waters and wastewaters. Organic toxicants were 10-100 times concentrated with adsorption cartridges from 4 l of river water or 1-10 times concentrated from 400 ml of wastewater. Toxicity of these concentrated solutions was determined by exposing 48-72 h post-hatch age larvae for 48 h. The method effectively revealed a variation of the median lethal concentration ratio (LCR50) from 13 to >100 in 125 river water samples, and from <1 to >10 in five typical wastewater samples. Ayase River, which takes water mostly from agricultural or household discharge, showed significantly (P<0.001) lower LCR50 than Sagami River that takes natural water as the source. Safety Levels in both Sagami River and Ayase River were influenced by the irrigation activity, LCR50 at some sites showing a seasonal-specific decrease in winter. Pollution from pulp and paper industries contributed to the low LCR50 in several tributaries of Ayase River. Required little manpower in sampling, pretreatment and testing, the proposed larval medaka assay was proved as an efficient tool for screening those high risk sites for priority management.

Application of a larval medaka assay to evaluate the fish safety level in Sagami River, Japan.

Despite of the increasing concern on aquatic life preservation from water pollution, few methods are available to evaluate the fish safety level of river water. In this study, a principal urban river of Japan, Sagami River, was investigated the geographical and seasonal changes in the fish safety level using an efficient larval medaka (Oryzias latipes) assay. Then combined with topography and land-use character of the catchment, the influence of human activity was discussed. The results revealed the highest fish safety levels and the lowest dissolved organic carbon (DOC) concentrations in the preserved region of the upstream. In the lower mainstream and the west tributaries, catchments of which were developed regions with high sewerage diffusion rates, the fish safety levels slightly decreased although the DOC concentrations were low. By comparison, the east tributaries, which were allocated in highly developed regions without sufficient sewerage service, showed not only high DOC concentrations but also greatly decreased fish safety levels. Two small east tributaries showed three to four times increase in the toxicity in winter, as influenced by the irrigation activity on the bank. The safety level did not closely depend on the common water quality indicator of DOC, although extremely high DOC concentrations tended to relate to low safety levels. The data is useful for better management of the river studied, and the approaches used in this paper will give a hint to the management of other rivers.

A method for measuring semi- and non-volatile organic halogens by combustion ion chromatography.

Recent studies have shown that various semi- and non-volatile organohalogen compounds are ubiquitous in the environment: these include halogenated dioxins including chlorinated dioxins, other persistent organic pollutants (POPs), brominated flame retardants (BFRs), and perfluorooctane sulfonate (PFOS). However, monitoring and assessment of these compounds by the analyses of individual compounds and their isomers is onerous because of their low environmental concentrations and large number of compounds. In this study, we have developed a new method that is capable of screening and monitoring an array of organohalogen compounds efficiently by combustion ion chromatography (CIC) - the new analyzer that serially connects combustion furnace and ion chromatograph. Analyzer performance was evaluated in terms of its applicability, reproducibility, and sensitivity as limit of detection (LOD). Recoveries of organochlorine, organobromine, and organoiodine compounds by the CIC were between 97 and 105%; those of organofluorine compounds were from 86 to 91%. In all cases, the relative standard deviation of five analyses was 4% or smaller. The analyzer would exhibit good sensitivity for various environmental matrices (e.g., 2.8-31ng-X/g-soil, 1.4-16ng-X/L-water, and 9.2-100ng-X/m3N-gas). The method is fast and can provide information regarding the occurrence of organohalogen compounds within 1 or 2 days after sampling. Applicability of the new method for the assessment of contamination in flue gas and fly ash was also demonstrated. Our results show that the method is efficient to investigate emission sources and areas contaminated by organohalogen compounds.

A new method for evaluating biological safety of environmental water with algae, daphnia and fish toxicity ranks.

In this study, an innovative approach to evaluate biological safety of environmental water with toxicity ranks was proposed. Widely used species, algae (Selenustrum capricornutum), daphnia (Daphnia magna) and fish (Oryzias latipes larvae) belonging to three trophic levels in aquatic ecosystem, were selected and combined as a test set to measure the bio-toxicity of water sample. Maximum exposure concentrations for algae, daphnia and fish test were respectively designed as 10-, 50- and 50-fold of river water based on a simplification of conventional toxicity extrapolation method EU Directive EEC/93/67. A novel assessment index "safety score" of 1, 2, 3 and 4 with 1 being the safest was established for normalizing the toxicity effects. Safety score was determined according to the highest exposure concentration where adverse ecotoxicological effects could not be observed, and a triangle figure was designed to visually describe the safety scores of three toxicity tests. Finally, in order to conveniently evaluate the biological safety of environmental water, an integrated assessment index "bio-safety rank" (BSR) was established and determined according to the safety scores of the three tests, and with the index BSR, water sample could be ranked as A, B, C or D with A being the safest. It was shown that the proposed new method was effective for screening and evaluating the biological safety of river water in case studies.

Analysis of adsorption equilibrium of volatile chlorinated organic compounds to dry soil.

Adsorption is one of the main mechanisms of soil contamination by hazardous volatile chlorinated organic compounds. The adsorption equilibriums of six volatile organic chlorinated compounds to three dry soils were investigated using batch adsorption experiments. The adsorption equilibriums for the dry soils could be expressed by the Dubinin-Astakhov equation. The equation's parameters were analyzed with the characteristic values of the soils and compounds. No correlation between the values of the affinity coefficients, beta, and the molecular volume, Mv, was found. W(0) could be expressed by the functions of a pore volume of less than 10 nm, V(<10 nm), or the specific surface area, S. The adsorbed amount could be estimated using equations relating E(0), V(<10 nm) (or S), and beta. The predicted amounts agreed well with the measured data.

Exchange characteristics of monocarboxylic acids and monosulfonic acids onto anion-exchange resins.

In the previous paper (N. Kanazawa, K. Urano, N. Kokado, Y. Urushigawa, J. Colloid Interface Sci. 238 (2001) 196), the equilibria of propionic acid and benzoic acid adsorption onto three anion-exchange resins were investigated, and an equation was proposed that summed of the physical adsorption of the carboxylic acid molecule and the ion exchange of the dissociated carboxylate ion. The ion exchange equation, including a selectivity coefficient to chloride ion for each combination between carboxylate ions and anion-exchange resins, could be used in wide ranges of concentration and pH. In this research, ion-exchange equilibria using 16 anion-exchange resins and 9 organic acids including monocarboxylic and monosulfonic acids were investigated. It could be confirmed that the proposed equation applied to the ion exchange with these monoorganic acids. Characteristics of ion exchange between the organic anions and anion exchange were also studied by the selectivity coefficients.

Estimation of adsorbed amounts of volatile chlorinated organic compounds to wet soil based on the properties of the compounds and soils.

The adsorption equilibriums of 7 volatile organic chlorinated compounds to 10 wet soils were investigated by continuous flow adsorption experiments. The adsorption equilibriums for the wet soils could be expressed by the Henry equation. The most part of the adsorbed amount existed on the organic substances in the soil, and the soil-water adsorption equilibrium constant could be estimated from the organic carbon content of the soil. The adsorption coefficient to the organic carbon of the chloroethylenes and chloroethanes could be expressed by the functions of the n-octanol/water partition coefficient, respectively. The adsorbed amounts could be estimated using equations relating the organic content and the water content of each soil, and the n-octanol/water partition coefficient and the Henry constant for the gas-water equilibrium of each compound. The estimated results agreed well with the measured data.

Adsorption Equilibrium Equation of Carboxylic Acids on Anion-Exchange Resins in Water.

The adsorption of propionic acid and benzoic acid on anion-exchange resins was analyzed, and an adsorption equilibrium equation of carboxylic acids was proposed. The adsorption of carboxylic acids on the anion-exchange resins was considered to be the sum of the physical adsorption of the molecule and the ion-exchange adsorption of the ion, which were independent of each other. For the physical adsorption of carboxylic acids, it was conformed to the Freundlich equation. For the ion-exchange adsorption of carboxylate ions, the equilibrium equation corresponded well with the experimental results for wide ranges of concentration and pH. The equation contains a selectivity coefficient S(A)(Cl) for the chloride ion versus the carboxylate ion, which was considered essentially a constant. The influent of the bicarbonate ion from carbon dioxide in air could also be expressed by the additional equilibrium equation with the selectivity coefficient S(HCO(3))(Cl) for the chloride ion versus the bicarbonate ion. Consequently, an adsorption equilibrium equation can estimate the equilibrium adsorption amounts. Even the effect of a coexisting bicarbonate ion is inconsequential when the parameters of the Freundlich isotherm equation and the selectivity coefficients of the carboxylate ion and the bicarbonate ion in each resin are determined in advance. Copyright 2001 Academic Press.