Rapid assessment of metabolic activity in marine microalgae: application in ecotoxicological tests and evaluation of water quality

A new method for the assessment of the effects of several contaminants on marine microalgae,Tetraselmis suecica (Kyling) Butcher,Skeletonema costatum (Grev.) Cleve, andProrocentrum lima (Ehrenberg) Dodge was developed in 1990. The method is based on the measurement of cell esterase activity using a fluorimetric stain, fluorescein diacetate (FDA), selected from amongst three stains (FDA, Neutral Red, thiazolyl tetrazolium bromure) for its higher sensitivity. Biochemical (K _m,V _max) and physiological (growth, specific activity) aspects of the enzymatic activity as revealed by the FDA method are discussed. Different categories of compounds (weed-killers, insecticides, metals) and some water samples from Seine Bay were tested for their toxic effects on microalgae. Experiments were performed on microplates using a fluorimetric microplate reader. The various steps of the experiments and data-processing were controlled by software. Applications of the system to rapid ecotoxicological tests (determination of the IC₅₀, i.e., the concentration at which 50% inhibition of growth occurs) and to the assessment of environment quality by studying the toxic effect of water samples on microalgae are proposed.     

Thermochemical studies of the toxic actions of heavy metal ions on Rhizopus nigricans

By using a LKB2277 BioActivity Monitor (heat conduction microcalorimeter), stopped-flow method, the thermogenetic curves of Rhizopus nigricans growth at 25 degrees C inhibited by four kinds of heavy metal ions are determined, parameters such as growth rate constants k, inhibitory ratio I, half inhibitory concentration IC50 et al. are obtained. The experimental results show that heavy metal ions can inhibit Rhizopus nigricans growth obviously, low concentration of Cu2+ has promoting action. The inhibitory sequence is Cd2+ > Hg2+ > Pb2+ > Cu2+, half inhibitory concentration of them are Cd+ 0.8 micro g x ml(-1), Hg2+ 1.7 micro g x ml(-1), Pb2+ 48.0 micro g x ml(-1), Cu2+ 110 micro g x ml(-1). This microclorimetric bioassay for acute cellular toxicity is based on metabolic heat evolution from cultured cells. The assay is quantitative, inexpensive, and versatile; moreover, toxicological information can be obtained with cell from other species of interest.     

A new enzyme immunoassay for PCDD/F TEQ screening in environmental samples: comparison to micro-EROD assay and to chemical analysis.

A new Enzyme ImmunoAssay (EIA) for PCDD/F TEQ measurement in extracts of environmental samples was described. The bioassay TEQ which derived from EIA and EROD were compared with each other and with results from chemical analysis. For all environmental samples, the EROD-TEQ is higher than the value from chemical analysis. However, the EIA-TEQ is much more identical with the value from chemical analysis. Our results indicate that the EIA assay is a complementary method to the EROD assay and should be useful as a rapid and sensitive screening tool for environmental samples in many situations.     

Possible use of constructed wetland to remove selenocyanate,arsenic, and boron from electric utility wastewater

Wetland microcosms were used to evaluate the ability of constructed wetlands to remove extremely high concentrations of selenocyanate (SeCN-), arsenic (As), and boron (B) from wastewater generated by a coal gasification plant in Indiana. The wetland microcosms significantly reduced the concentrations of selenium (Se), As, B, and cyanide (CN) in the wastewater by 64%, 47%, 31%, and 30%, respectively. In terms of the mass of each contaminant, 79%, 67%, 57%, and 54% of the Se, As, B, and CN, respectively, loaded into the microcosms were removed from the wastewater. The primary sink for the retention of contaminants within the microcosms was the sediment, which accounted for 63%, 51%, and 36% of the Se, As, and B, respectively. Accumulation in plant tissues accounted for only 2-4%, while 3% of the Se was removed by biological volatilization to the atmosphere. Of the 14 plant species tested, cattail, Thalia, and rabbitfoot grass were highly tolerant of the contaminants and exhibited no growth retardation. Environmental toxicity testing with fathead minnow (Pimephales promelas) larvae confirmed that the water treated by the wetland microcosms was less toxic than untreated water. The data from the wetland microcosms support the view that constructed wetlands could be used to successfully reduce the toxicity of aqueous effluent contaminated with extremely high concentrations of SeCN-, As, and B, and that a pilot-scale wetland should therefore be constructed to test this in the field. Cattail, Thalia, and rabbitfoot grass would be suitable plant species to establish in such wetlands.     

On the selection of primary variables in numerical formulation for modeling multiphase flow in porous media

Selecting the proper primary variables is a critical step in efficiently modeling the highly nonlinear problem of multiphase subsurface flow in a heterogeneous porous-fractured media. Current simulation and ground modeling techniques consist of (1) spatial discretization of mass and/or heat conservation equations using finite difference or finite element methods; (2) fully implicit time discretization; (3) solving the nonlinear, discrete algebraic equations using a Newton iterative scheme. Previous modeling efforts indicate that the choice of primary variables for a Newton iteration not only impacts computational performance of a numerical code, but may also determine the feasibility of a numerical modeling study in many field applications. This paper presents an analysis and general recommendations for selecting primary variables in simulating multiphase, subsurface flow for one-active phase (Richards' equation), two-phase (gas and liquid) and three-phase (gas, water and nonaqueous phase liquid or NAPL) conditions. In many cases, a dynamic variable switching or variable substitution scheme may have to be used in order to achieve optimal numerical performance and robustness. The selection of primary variables depends in general on the sensitivity of the system of equations to the variables selected at given phase and flow conditions. We will present a series of numerical tests and large-scale field simulation examples, including modeling one (active)-phase, two-phase and three-phase flow problems in multi-dimensional, porous-fractured subsurface systems.     

Contaminated site remedial investigation and feasibility removal of chlorinated volatile organic compounds from groundwater by activated carbon fiber adsorption

Groundwater contaminated by dense, non-aqueous phase liquids (DNAPLs) such as chlorinated solvents has become a serious problem in some regions of Taiwan. The sources of these contaminants are due to industrial discharges. These chlorinated volatile organic compounds (VOCs) have been proven to be carcinogenic to humans. The groundwater is used for domestic drinking water supply in some cities of Taiwan and the severely contaminated groundwater has to be treated in order to meet the requirement of drinking water standards. This study covers two areas of work. In the first part, polluted groundwater samples were collected from the contaminated site and analytical results indicated measurable concentrations of 12 representative chlorinated VOCs in water samples. The primary VOCs detected included trichloroethene (TCE), tetrachloroethene (PCE), 1,1,2-trichloroethane (1,1,2-TCA), and 1,1-dichloroethene (1,1-DCE). Second, to remove VOCs groundwater was treated using adsorption on activated carbon fiber (ACF). This involved pumping groundwater through vessels containing ACF. Most VOCs, including TCE, PCE, 1,1,2-TCA, and DCE, were readily adsorbed onto ACF and are removed from the water stream. Our study showed that the technology was able to significantly reduce chlorinated VOCs concentrations in groundwater.     

Natural pollution caused by the extremely acidic crater lake Kawah Ijen, East Java, Indonesia

Background. Aims and Scope Lakes developing in volcano craters can become highly acidic through the influx of volcanic gases, yielding one of the chemically most extreme natural environments on earth. The Kawah Ijen crater lake in East Java (Indonesia) has a pH 〈 0.3. It is the source of the extremely acid and metal-polluted river Banyupahit (45 km). The lake has a significant impact on the river ecosystem as well as on a densely populated area downstream, where agricultural fields are irrigated with water with a pH between 2.5 and 3.5. The chemistry of the river water seemed to have changed over the past decade and the negative effect in the irrigation area increased. A multidisciplinary approach was used to investigate the altered situation and to get insight in the water chemistry and the hydrological processes influencing these alterations. Moreover, a first investigation of the effects of the low pH on ecosystem health and human health was performed. Methods Water samples were taken at different sites along the river and in the irrigation area. Sampling for macroinvertebrates was performed at the same sites. Samples of soil and crop were taken in the irrigation area. All samples were analysed for metals (using ICP-AES) and other elements, and concentrations were compared to local and international standards. Results and Discussion The river carries a very high load of SO4, NH4, PO4, Cl, F, Fe, Cu, Pb, Zn, Al and other potentially toxic elements. Precipitation and discharge data over the period of 1980 – 2000 clearly show that the precipitation on the Ijen plateau influences water chemistry of the downstream river. Metal concentrations in the river water exceed the concentrations mentioned in Indonesian and international quality guidelines, even in the downstream river and the irrigation area. Some metal concentrations are extremely high, especially iron (up to 1600 mg/l) and aluminium (up to 3000 mg/l). The food-webs in the acidic parts of the river are highly underdeveloped. No invertebrates were present in the extremely acid water and, at pH 2.3, only chironomids were found. This also holds true for the river water with pH 3.3 in the downstream area. Agricultural soils in the irrigation area have a pH of 3.9 compared to a pH of 7.0 for soils irrigated with neutral water. Decreased yields of cultivated crops are probably caused by the use of Al containing acid irrigation water. Increased levels of metals (especially Cd, Co, Ni and Mn) are found in different foodstuffs, but still remain within acceptable ranges. Considering local residents” diets, Cd levels may lead to an increased risk for the human health. Fluoride exposure is of highest concern, with levels in drinking water exceeding guideline values and a lot of local residents suffering from dental fluorosis. Conclusions, Recommendations and Outlook In short, our data indicate that the Ijen crater lake presents a serious threat to the environment as well as human health and agricultural production.     

Enhanced degradation of chlorinated ethylenes in groundwater from a paint contaminated site by two-stage fluidized-bed reactor

Groundwater, used in this study, contaminated predominantly with aromatic compounds, was biologically treated in a fluidized-bed reactor (FBR) with immobilized cells. The aromatics were completely decomposed, while cis-1,2-dichloroethylene (cis-DCE) and trichloroethylene (TCE) were decomposed only approximately 20% and 5%, respectively. In these studies a significant improvement of the decomposition efficiency for chlorinated ethylenes was achieved by utilizing cometabolism. Methanol (MeOH) and toluene were used as the substrate in the case of one-stage reactor (Single Reactor). MeOH (187 mg l(-1)) increased the decomposition efficiency up to 40% and 60% for cis-DCE and TCE, respectively, while toluene (20 mg l(-1)) increased the decomposition efficiency of cis-DCE to 92% and the decomposition efficiency of TCE to 76%. In the case of two-stage reactor system (Reactor 1 and Reactor 2), MeOH and methane (CH4) were used as the substrate. In this system, cells grown on MeOH or CH4 in the Reactor 1 were continuously fed into Reactor 2 and groundwater was fed into Reactor 2 only. When MeOH (384 mg l(-1) d(-1)) was used as substrate the decomposition efficiency of cis-DCE and TCE were 60% and 70%, respectively. Similar decomposition efficiency was observed for a small amount of CH4 (19.3 mg l(-1) d(-1)).     

Investigating the sources of the mutagenic activity found in a river using the Salmonella assay and different water extraction procedures

In the routine São Paulo state (Brazil) surface water quality-monitoring program, which includes the Salmonella microsome mutagenicity assay as one of its parameters, a river where water is taken and treated for drinking water purposes has repeatedly shown mutagenic activity. A textile dyeing facility employing azo-type dyes was the only identifiable source of mutagenic compounds. We extracted the river and drinking water samples with XAD4 at neutral and acidic pH and with blue rayon, which selectively adsorbs polycyclic compounds. We tested the industrial effluent, raw, and treated water and sediment samples with YG1041 and YG1042 and compared the results with the TA98 and TA100 strains. The elevated mutagenicity detected with YG-strains suggested that nitroaromatics and/or aromatic amines were causing the mutagenicity detected in the samples analyzed. Positive responses for the blue rayon extracts indicated that mutagenic polycyclic compounds were present in the water samples analyzed. The mutagen or mixture of mutagens present in the effluent and water samples cause mainly frameshift mutations and are positive with and without metabolic activation. The Salmonella assay combined with different extraction procedures proved to be very useful in the identification of the origin of the pollution and in the identification of the classes of chemical compounds causing the mutagenic activity in the river analyzed.     

Use of naturally growing aquatic plants for wastewater purification.

This paper examines potential uses of naturally growing aquatic plants for wastewater purification. These plants enhance the removal of pollutants by consuming part of them in the form of plant nutrients. This applies to urban and agricultural wastewater, in particular, where treatment units of different sizes can be applied at the pollution source. The effectiveness of wastewater purification by different plants was tested on laboratory and pilot scales. The growth rate of the plants was related to the wastewater content in the water. Batch and semicontinuous experiments verified that the plants are capable of decreasing all tested indicators for water quality to levels that permit the use of the purified water for irrigation. This applies to biochemical oxygen demand (BOD), chemical oxygen demand, total suspended solids. pH, and turbidity. In specific cases, the turbidity reached the level of drinking water. Comparison of BOD concentrations with typical levels in water treatment facilities across the country indicates the effectiveness of water purification with plants. A major effect of treatment with plants was elimination of the disturbing smell from the wastewater. It is shown that mixtures of wastewater and polluted water from the Kishon River are amenable in varying degrees to treatment by the plants. The higher the wastewater content in the mixture, the more effective the treatment by the plants. In this context, a scheme for rehabilitation and restoration of the Kishon River is presented and technical and economical aspects of the purification technology are considered.