Concentrations Of Several Contaminants Research Articles

Chemical and Thermal Exposure Risks in a Multi Compartment Training Structure

AbstractProviding NFPA 1403 compliant live-fire training can present thermal and chemical exposure risk to instructors and students. To reduce risk, training academies, fire departments, instructors, and standards setting technical committees need more information on how different training fuels used in common training structures can impact the environment in which firefighter training occurs. This study utilized a traditional concrete training structure with multiple compartments to characterize training environments with three different fuel package materials [i.e., low density wood fiberboard, oriented strand board (OSB), and wood pallets]. Exposure risks for a fire instructor located on either the first or second floor were characterized using measurements of heat flux, air temperature and airborne concentrations of several contaminants including known, probable, or possible carcinogens. It was hypothesized that utilizing a training fuel package with solid wood pallets would result in lower concentrations of these airborne contaminants [aldehydes, polycyclic aromatic hydrocarbons (PAHs) and volatile organic compounds (VOCs)] than wood-based sheet goods containing additional resins and/or waxes. Additionally, it was hypothesized that these concentrations would be lower than in the single compartment Fire Behavior Lab presented in a companion manuscript. For all measured compounds other than hydrochloric acid, airborne concentrations were 10 to 100 times lower than in the Fire Behavior Lab. OSB-fueled fires produced the highest median concentrations of total PAHs and VOCs such as benzene, while the pallet fuel package produced the lowest median concentrations of these compounds. These trends generally followed the qualitative visual obscuration created by each fuel. Additional tests were conducted on the OSB-fueled fires with increased ventilation and an alternate means of reducing visibility through smoldering smoke barrels. This OSB experiment with increased ventilation resulted in the highest temperatures in the fire room but the lowest impact on visibility throughout the structure, as well as the lowest overall concentrations of contaminants in this study. In contrast, the smoldering straw-filled smoke barrel created a highly obscured environment (with minimal impact on thermal environment) and some of the highest concentrations of the targeted contaminants of any test. These data may be useful in balancing obscuration for training with potential exposure to thermal stressors and contaminants.

Contaminant risks in consuming fish from the Area of Concern in the Upper Niagara River

The lack of contemporary data on contaminants in resident fish prevents an analysis of temporal trends in contaminant concentrations and the present-day status of the “Restrictions on Fish and Wildlife Consumption” Beneficial Use Impairment (BUI) in the Niagara River Area of Concern (AOC). During 2018, concentrations of 260 contaminants in four groups of fish species from five areas in or near the upper Niagara River AOC were analyzed to determine the potential risks from fish consumption, responses to remediation in an adjacent AOC, and whether additional remedial actions were warranted in this AOC. The concentrations of most contaminants were generally undetectable or did not exceed established Federal, State, or European Union fish-consumption limits. Several contaminants without State or Federal limits exceeded European Union fish-consumption guidelines in some species and areas. High PCB residues in many bullhead from Scajaquada Creek, some bass from Hoyt Lake, and most common carp from all areas surpassed certain New York and Federal fish-consumption limits and indicate PCBs continue to restrict fish consumption at most study areas. High concentrations of several contaminants in resident fish, especially dioxins and furans in carp, from Cayuga Creek indicate that additional scrutiny of consumption advisories is warranted in this area. Because this study provides a snapshot in time of fish-contaminant data from five areas, additional data from other areas and times, and more detailed information on present-day pollutant sources may be needed before determining the status of the fish-consumption BUI in this AOC.

Health impact assessment of pet cats caused by organohalogen contaminants by serum metabolomics and thyroid hormone analysis

Companion animals are in close contact with the human surroundings, and there is growing concern about the effects of harmful substances on the health of pet cats. In this study, we investigated the potential health effects of organohalogen compounds (OHCs) on thyroid hormone (TH) homeostasis and metabolomics in Japanese pet cats. There was a significant negative correlation between concentrations of several contaminants, such as polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), hydroxylated PCBs (OH-PCBs), hydroxylated PBDEs (OH-PBDEs), and THs in cat serum samples. These results suggested that exposure to OHCs causes a decrease in serum TH levels in pet cats.In this metabolomics study, each exposure level of parent compounds (PCBs and PBDEs) and their hydroxylated compounds (OH-PCBs and OH-PBDEs) were associated with their own unique primary metabolic pathways, suggesting that parent and phenolic compounds exhibit different mechanisms of action and biological effects. PCBs were associated with many metabolic pathways, including glutathione and purine metabolism, and the effects were replicated in in-vivo cat PCB administration studies. These results demonstrated that OHC exposure causes chronic oxidative stress in pet cats. PBDEs were positively associated with alanine, aspartate, and glutamate metabolism. Due to the chronic exposure of cats to mixtures of these contaminants, the combination of their respective metabolic pathways may have a synergistic effect.

Laboratory Simulation of Groundwater Along Uranium-Mining-Affected Flow Paths Near the Grand Canyon, Arizona, USA

Mining of volumetrically small, but relatively enriched (average 0.6% U3O8) breccia pipe uranium (BPU) deposits near the Grand Canyon, Arizona, USA has the potential to affect groundwater and springs in the area. Such deposits also contain base metal sulfides that can oxidize to generate acid mine drainage and release trace metals. In this study, sequential batch experiments were conducted to simulate the geochemistry of local shallow groundwater that contacts BPU ore and then moves downgradient through sedimentary strata. The experiments simulated shallow groundwater in a carbonate aquifer followed by contact with BPU ore. The experiments subsequently simulated contact with sedimentary rocks and changing oxygen availability. Concentrations of several contaminants of potential concern became substantially elevated in the waters exposed to BPU ore, including As, Co, Ni, U, and Zn, and to a lesser extent, Mo. Of these, Co, Mo, Ni, and U were minimally attenuated by downgradient processes, whereas Zn was partially attenuated. Sb and Tl concentrations were more moderately elevated but also generally minimally attenuated. Although the mixture of elements is particular to these BPU ore deposits, sulfide oxidation in the ore and carbonate buffering of pH by sedimentary rocks generates patterns of water chemistry common in acid mine drainage settings. Ultimately, downgradient concentrations of elements sourced from BPU ore will also be strongly influenced by non-geochemical factors such as the quantities of water contacting BPU materials, heterogeneity of materials along flow paths, and mixing with waters that have not contacted BPU materials.

Phycoremediation of fish farm wastewater by Chlorella sorokiniana and autochthonous microalgae

With the disorderly increase in global environmental problems, the cultivation of aquatic organisms is a promising path for sustainable food production. The quality of water, both at the entrance and exit of the production of aquatic animals, needs to be maintained following the parameters specified by local legislation. This study aimed to investigate the removal of contaminants from fish farming wastewater associated with the production of freshwater microalgae biomass. Six completely randomized treatments were used in triplicate: with the addition of microalgae C. sorokiniana in fish farm wastewater (W+Cs), the addition of C. sorokiniana in wastewater enriched with NPK fertilizing (W+F+Cs) or sugarcane vinasse (W+V+Cs), only wastewater (W), wastewater supplemented with fertilizer (W+F) or vinasse (W+V). The wastewater was used in natura to allow the development of autochthonous microalgae. The microalgae C. sorokiniana grew rapidly in effluents enriched with NPK and vinasse. After 28 days of bioassay, the concentrations of several contaminants in the water were reduced: zinc (20 to 88%), lead (5 to 83%), aluminum (56 to 75%), manganese (56 to 72%), cadmium (9 to 52%), calcium (16 to 24%) and magnesium (12 to 33%). Our results indicated that the production of microalgae biomass can be integrated with the treatment of fish farming effluents to reduce the environmental burden and increase the economic bonus for adopting a sustainable production method. However, our results also indicated the importance of introducing a microalgae strain with high productive performance and supplementing the wastewater to obtain rapid biomass.

Production of contaminant-depleted solid recovered fuel from mixed commercial waste for co-processing in the cement industry

Solid recovered fuels (SRF) have increasingly substituted primary fuels in the cement industry, even up to 100%. However, contaminants originating from the discarded consumer products are transferred into waste and SRF. With increasing amounts of SRF being utilized, closely monitoring contaminant concentrations – as is already state of the art in several countries and the cement industry – is gaining importance. SRF producers may need to take measures assuring that quality criteria are met, contaminant concentrations are kept at a low level, or to produce contaminant-depleted SRF. This work investigates and discusses the potential measures to reduce contaminant concentrations: removing the fine fractions, polyethylene terephthalate (PET), polyvinyl chloride (PVC), and black&grey materials. Five streams of mixed commercial waste were coarsely comminuted, screened, PET and PVC were removed using an industrial near-infrared sorter, and black&grey materials were manually removed and further sorted by fourier-transform infrared spectroscopy. Concentrations of Ag, Al, As, Ba, Ca, Cd, Cl, Co, Cr, Cu, Fe, Hg, K, Li, Mg, Mn, Mo, Na, Ni, P, Pb, Sb, Si, Sn, Sr, Ti, V, W, and Zn in the fractions are reported, and the effect of single and combined measures is presented. Results show that black&grey materials contain significant shares of the total Sb, Cl, and Co in the waste stream. Furthermore, the concentration of several contaminants is increased when only PET and PVC is removed. Removing the fine fraction together with PVC can lead to a concentration decrease of all investigated analytes, enabling the production of a contaminant-depleted SRF.

Contaminant screening and tissue distribution in the critically endangered Brazilian guitarfish Pseudobatos horkelii

Elasmobranchs are particularly prone to accumulating contaminants due to their life history patterns and relatively high trophic position. However, several compounds, especially contaminants of emerging concern, have still not been well studied in this group. Here, we aimed to determine the occurrence and concentrations of several inorganic and organic contaminants in different tissues of the Brazilian guitarfish Pseudobatos horkelii. This species is a critically endangered species, endemic from the Southwest Atlantic which uses southern Brazilian waters as a nursery habitat. Polycyclic aromatic hydrocarbons (PAHs), emerging pesticides, pharmaceutical and personal care products (PPCPs) and trace metals were determined in five biological tissues in order to assess the accumulation and organotropism of these compounds. Except for chlorothalonil and triclosan, all compounds were detected in, at least, one tissue, mostly in liver samples. All compounds differed among tissues, with liver presenting the higher concentrations of several contaminants, followed by muscle and gills. PAHs and PPCPs were the most detected analytes and presented the highest concentrations among tissues. Diclofenac levels were determined, for the first time in elasmobranchs, and were relatively high, when compared to other fishes. Finally, relatively high concentrations of PAHs, dichlofluanid and octocrylene in muscle might be suggestive of chronic exposure, presenting also human health implications. Regarding trace metals, contrary to most elasmobranch studies, Hg levels were low in all tissues, whereas Cd and Pb here higher in liver, and gills and blood samples, respectively. Our results indicate that P. horkelii is exposed to several organic and inorganic which might affect this species in a long-term scale. Concerning the determination of emerging contaminants, it is likely that other elasmobranchs are also exposed to these compounds and special attention should be given to this issue in order to predict future effects on this group.

Cytotoxic and genotoxic activities of waters and sediments from highway and parking lot runoffs.

The genotoxicity of water and sediment samples from stormwater treatment systems and water from urban highway runoff was tested in the Salmonella/microsome assays with Salmonella typhimurium, micronucleus assay (Trad-MN) with plants and with human-derived liver cells (HepG2), or comet assay with HepG2. Cytotoxicity of water samples was studied using either reactive oxygen species (ROS) generation, cell proliferation or dye exclusion assay in HepG2. Concentrations of several contaminants in the tested samples were also measured. Results suggested that urban highway runoff exposed to severe vehicle traffic emissions caused genotoxic effects in comet assay and in Trad-MN assays. Sediments induced either mutagenic effects in strain YG1024 or genotoxic effects in Trad-MN assay. These effects could be due to the presence of nitro-polycyclic aromatic hydrocarbons (NPAHs) which possess carcinogenic and mutagenic properties. Influent and effluents of stormwater treatment systems did not induce genotoxic activity or effects on HepG2 cell viability; however, the influents were able to induce ROS generation and cell proliferation in HepG2 cells. As the methods require a sterile filtration of the water samples, this could have also removed particulate-associated polycyclic aromatic hydrocarbons (PAHs) and resulted in a less pronounced induction of genotoxicity, as would be expected by PAH contamination.

Ecotoxicological assessment of diamondback terrapin (Malaclemys terrapin) pond habitat, prey and eggs in Bermuda

Total petroleum hydrocarbons, PAH and various trace metal residues were extracted and analyzed from fresh whole diamondback terrapin (Malaclemys terrapin) eggs, whole brackish-water gastropods (terrapin prey) and benthic sediment from anchialine pond environments in Bermuda inhabited by terrapins. Gastropods and terrapin eggs showed higher concentrations of trace metals and organic contaminants than sediments. Conversely, PAHs were mostly found within the sediment and smaller amounts detected in gastropods and terrapin eggs. Results indicated that contaminants in prey were transferred to terrapin eggs, and that concentrations of several contaminants exceeded potentially toxic concentrations for aquatic vertebrates. Necropsy of unhatched eggs from nests that had yielded viable hatchlings showed significantly compromised embryonic development. Bermudian diamondback terrapins reside and feed in brackish wetland habitats characterized by widespread, multifactorial contamination. This study suggests that environmental contamination plays a role in the recorded low hatching success in terrapin eggs in Bermuda.

Statistical Assessment of Unidirectional Propagation of a Leachate Contamination Plume

The leachate produced by the Municipal Solid Waste Landfill of Sao Pedro da Aldeia (State of Rio de Janeiro, Brazil) flows almost entirely in one direction guided by a natural ditch in the bottom of a gentle valley. This landfill has been in operation with no concern to environmental protection, such as containment systems or leachate drainage and treatment. This inadequate operation causes severe damage to flora, wildlife and local farmers, due to continuous propagation of contaminants in the groundwater. Field and laboratory measurements of ionic concentrations of several contaminants found in the groundwater adjacent the landfill are presented and interpreted in this paper. Several farms are located adjacent to the landfill, comprising about 1,000 inhabitants that use the ground water for personal use and land farming activities. The main purpose of this paper is to assess the environmental hazard to the surrounding properties as the landfill is still in operation. This is accomplished by estimating the maximum distance travelled by the leachate plume based on the statistical interpretation of the measured ionic concentration of several contaminants found commonly in landfills. The main recommendation coming from the statistical assessment is that safe groundwater consumption should be limited to a minimum distance of 400 m from the contamination source, provided that the quality of ground water is continuously monitored while the MSW landfill is still in operation.

Spatial Distributions and Temporal Trends in Sediment Contamination in Lake St. Clair

The sediments of Lake St. Clair were surveyed in 2001 for a range of compound classes including metals (such as total mercury and lead), polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins and dibenzofurans, organochlorine pesticides, polycyclic aromatic hydrocarbons, and short- and medium- chain chlorinated paraffins, in order to evaluate the spatial distribution and temporal trends of contamination. Concentrations of contaminants were generally low compared to the lower Great Lakes (Erie and Ontario), and were typically below the Canadian Sediment Quality Probable Effect Level (PEL) guidelines. The only exceptions were for mercury and DDE, where concentrations exceeded their respective PEL at one of the thirty-four sites sampled. With the exception of mercury, it was difficult to interpret spatial trends in contaminant concentrations due to these low levels, although relatively elevated concentrations of several contaminants were found in L’Anse Creuse Bay and at the outflow of the Thames River. In the case of mercury, historically-contaminated sediments in the St. Clair River associated with chlor-alkali production appeared to contribute to loadings to Lake St. Clair. There have been substantial reductions in sediment contamination in Lake St. Clair over the past three decades, as determined through sediment core profiles as well as through comparison of current data to those from historical surveys conducted in the early 1970s. These results indicate that management actions to reduce contaminant loadings to Lake St. Clair have been generally successful.

Contaminant residues in snapping turtle (Chelydra s. serpentina) eggs from the Great Lakes-St. Lawrence River basin (1999 to 2000).

To determine temporal and geographic variations of environmentally persistent pollutants, the concentrations of several contaminants were measured in snapping turtle eggs in 1999 and 2000. Contaminants included polychlorinated biphenyls (PCBs), non- ortho PCBs, polychlorinated dibenzodioxins and furans, organochlorine pesticides, and total mercury. Egg collection sites within the St. Lawrence Area of Concern (AOC) and the Territory of Akwesasne included Turtle Creek, Snye Marsh, and Raquette River. Additional contaminated sites were Gray's Creek (within the St. Lawrence AOC boundary), Coote's Paradise (Hamilton Harbour AOC), and the Territory of Walpole Island (St. Clair AOC). Reference sites were Lake Sasajewun, Algonquin Provincial Park in central Ontario, and in close proximity to the St. Lawrence Area AOC, Hoasic Creek and Cooper Marsh. Eggs from clutches collected from Akwesasne contained the highest concentrations of contaminants. Mean total PCB concentrations for Akwesasne clutches ranged from 1,900 to 61,000 ng/g wet weight (w.w.), which was 360 to 3,100 times higher than the mean concentrations at the reference sites. The high levels of contaminants in eggs, from sites within Akwesasne, were consistent with trends reported in the past and reflect the influence of the proximity of heavy industry. Current contaminant concentrations in clutches from Coote's Paradise are comparable with those recorded in 1989 and 1990 but are 200 to 800 times lower than concentrations reported in 1984 and 1988. Eggs from Lake Sasajewun contained relatively low contaminant levels, which is consistent with atmospheric deposition. Our results support that snapping turtles are good indicators of temporal and geographic contaminant trends.

Chemical Contamination of Aquatic Organisms from an Urbanized River in the New York/New Jersey Harbor Estuary

ABSTRACT The lower 6 miles of the tidal Passaic River, part of the New York/New Jersey (NY/NJ) Harbor Estuary system, are contaminated with a variety of organic and inorganic chemicals as a result of more than 150 years of heavy industrialization and urbanization. The River's ecology is substantially degraded due to habitat removal/alteration, and the organisms that reside in or utilize the River are exposed to and bioaccumulate chemicals from sediments and food web interactions. We quantify in this study the extent and magnitude of chemical contamination in several fish species (representing a range of trophic levels) and blue crab (Callinectes sapidus). In addition, the concentration of several contaminants of concern are compared to concentrations in similar organisms from other areas of the NY/NJ Harbor Estuary, as well as available tissue-based toxicological effects benchmarks that are reported in the literature. The results suggest that a variety of contaminants are present at elevated levels in each of the species collected from the River. Several contaminants, including 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD), total DDT (2,2-bis[4-chlorophenyl]1,1-dichloroethene), copper, and mercury are present at average concentrations that exceed those from other waterways in the NY/NJ Harbor Estuary. However, the concentrations of contaminants in the River, with few exceptions do not exceed available toxic effects levels as reported in the literature for these or similar fish and crustaceans. This suggests that toxicological risks from bioaccumulative contaminants in the lower Passaic River are limited to select contaminants and species.

Relationships between sediment contamination and toxicity in San Francisco Bay

Sediment contamination and toxicity were monitored at 14 sites in San Francisco Bay between 1991 and 1996. Sediment contamination patterns were different in the major reaches of the Bay, and at each site. Several contaminants were consistently above concentrations previously associated with toxicity at most sites. Bulk sediment bioassays using the amphipod Eohaustorius estuarius and sediment elutriate bioassays using larval bivalves ( Mytilus spp., Crassostrea gigas) also indicated different patterns of sediment toxicity in space and time. Sediments were most toxic to the amphipods at Redwood Creek (90% of the tests), and were toxic in at least half the tests conducted at five other sites. Sediment elutriates severely reduced normal bivalve larval development at the San Joaquin and Sacramento Rivers in all samples, but toxicity occurred in less than a third of the tests in the Central and South Bays. Toxicity could not be statistically related to seasonal freshwater flow or rainfall in the Bay, but seasonal variation in contaminant concentrations and toxicity was observed. Amphipod toxicity was inversely and significantly related to the mean effects range-median quotient, suggesting that cumulative concentrations of several contaminants were related to toxicity. Further analysis identified suites of specific contaminants at each site that were variably related to amphipod toxicity at each site. Chlordanes, cadmium, and silver were significantly related to amphipod survival in the North Bay. Seasonal patterns in low, and high molecular weight polycyclic aromatic hydrocarbons (PAHs) were related to toxicity at Alameda, and metals and PAHs were related to toxicity at Castro Cove. Larval bivalve toxicity was associated with metals in bulk sediments, but elutriate chemistry was not measured, and relationships with toxicity could not be examined. Hypotheses about effective concentrations of several individual contaminants and mixtures of contaminants were posed.

Optimization strategies for the design and synthesis of distributed wastewater treatment networks

This paper applies an optimization strategy for the design of a distributed wastewater network where multicomponent streams are considered. The streams are to be processed by different technologies for reducing the concentration of several contaminants to meet environmental regulations. The model gives rise to a nonconvex nonlinear and a heuristic search procedure is applied to find the global optimum or a good upper bound of the global optimum. The procedure is based on the successive solution of a relaxed linear model and the original nonconvex nonlinear problem and on the use of several objective functions in the relaxed model. Two examples are presented to illustrate that method.

An investigation of the application of the Canadian water quality guidelines

AbstractThe Canadian water quality guidelines for the protection of aquatic life assume that (1) the external water concentration is an effective measure of the concentration at the active site in organisms, which is ultimately responsible for a toxic response, and that (2) the safety factor accounts for any differences between laboratory and field conditions as well as the extrapolation from the effect concentration to a long‐term no‐effect concentration. This study examines these assumptions and assesses potential errors that environmental managers can make when applying the guidelines. The methodology is based on assessing the probability that internal concentrations of several contaminants are greater than or less than the “safe” concentration, assumed by the guideline, when the water concentration is at the water quality guideline. Results derived from empirical observations and a food‐web bioaccumulation model show that a high probability (62–100%) exists that safe internal concentrations are exceeded for polychlorinated biphenyls, 1,2,4,5‐tetrachlorobenzene, and hexachlorobenzene in Lake Ontario when the aqueous concentrations are at the water quality guideline values. This is due to field bioaccumulation factors being greater than the bioaccumulation factors in laboratory toxicity tests used for the water quality guideline development. Factors contributing to the exceedence of safe internal concentrations at the water quality guideline values are identified. Recommendations for improvement of the water quality guideline process are provided.

Ecological and ecotoxicological surveys of moderately contaminated floodplain ecosystems in The Netherlands

Floodplains of the rivers Rhine and Meuse in the Netherlands are moderately polluted with heavy metals and toxic compounds. In these floodplain areas a number of nature rehabilitation programmes are being planned and executed. The question arises whether or not the contaminants of concern pose a risk to organisms exposed, and, if so, whether this will hinder the expected ecosystem recovery. This study focuses on the effects of contaminants on aquatic and terrestrial macro-invertebrates in the field situation. In three shallow lakes in the floodplains of the river Rhine, showing different degrees of contamination, chemical analyses and laboratory bioassays have been carried out on sediment samples together with intensive biological field surveys (a so called TRIAD-approach). A nearly identical set-up was chosen to assess 18 terrestrial floodplain sites. The concentrations of several contaminants exceed generic critical risk levels. Risk assessment models show that actual effects on top predators cannot be excluded. Species of lower trophic status might be at risk as well. In the aquatic compartments chemical, ecotoxicological and ecological results point in the same direction. They can be summarised as moderate biological effects, which can mainly be attributed to the elevated levels of a mixture of priority pollutants (metals and polyaromatic hydrocarbons). No large differences were found among the three lakes. At terrestrial sites, however, fewer effects were found in field surveys and bioassays, while the chemical analyses revealed the same levels of pollution as in the lakes study. This suggests a lower bioavailability of the contaminants than expected. In conclusion, no extreme effects have been found. This conclusion only partly supports the predictions made by present day-risk assessment models. The advantages of nature rehabilitation, that is, improvement of ecological quality through habitat diversity, seem to be larger than the disadvantages of increasing toxic stress by exposing a larger diversity of species to floodplain contaminants. To confirm this statement rehabilitation programmes should include overall as well as in-depth monitoring studies.

Ecological and ecotoxicological surveys of moderately contaminated floodplain ecosystems in The Netherlands

Abstract Floodplains of the rivers Rhine and Meuse in the Netherlands are moderately polluted with heavy metals and toxic compounds. In these floodplain areas a number of nature rehabilitation programmes are being planned and executed. The question arises whether or not the contaminants of concern pose a risk to organisms exposed, and, if so, whether this will hinder the expected ecosystem recovery. This study focuses on the effects of contaminants on aquatic and terrestrial macro-invertebrates in the field situation. In three shallow lakes in the floodplains of the river Rhine, showing different degrees of contamination, chemical analyses and laboratory bioassays have been carried out on sediment samples together with intensive biological field surveys (a so called TRIAD-approach). A nearly identical set-up was chosen to assess 18 terrestrial floodplain sites. The concentrations of several contaminants exceed generic critical risk levels. Risk assessment models show that actual effects on top predators cannot be excluded. Species of lower trophic status might be at risk as well. In the aquatic compartments chemical, ecotoxicological and ecological results point in the same direction. They can be summarised as moderate biological effects, which can mainly be attributed to the elevated levels of a mixture of priority pollutants (metals and polyaromatic hydrocarbons). No large differences were found among the three lakes. At terrestrial sites, however, fewer effects were found in field surveys and bioassays, while the chemical analyses revealed the same levels of pollution as in the lakes study. This suggests a lower bioavailability of the contaminants than expected. In conclusion, no extreme effects have been found. This conclusion only partly supports the predictions made by present day-risk assessment models. The advantages of nature rehabilitation, that is, improvement of ecological quality through habitat diversity, seem to be larger than the disadvantages of increasing toxic stress by exposing a larger diversity of species to floodplain contaminants. To confirm this statement rehabilitation programmes should include overall as well as in-depth monitoring studies.

Volatile halocarbons in a drinking water supply system: Forecasting contamination values and estimating health risk

The network, which supplies drinking water to the city of Milan, has a number of sampling points, where the concentrations of several contaminants are periodically measured. From the time series of total volatile halocarbon (VHC) concentration values (in the ppb range) autoregressive models can be obtained for each sampling point. A suitable figure of merit is minimized, which depends on the backcast error and on the model order. The best model is then applied to predicting concentration one time step e.g., one year, forward. The experimental data pertain to the years 1981 to 1992. Predicted values are compared with the measured ones. The results obtained in 1991 contributed to avert a major emergency situation in Milan. Population exposure and the related health risk, based on the proportional dosage-response model, were also estimated. The excess casualty figure for Milan was computed. The method and the procedures described herewith may be used by public authorities to manage drinking water resources, whenever detailed models of the aquifer and of the network are not applicable.

Optimal Design of Distributed Wastewater Treatment Networks

This paper deals with the optimum design of a distributed wastewater network where multicomponent streams are considered that are to be processed by units for reducing the concentration of several contaminants. The proposed model gives rise to a nonconvex nonlinear problem which often exhibits local minima and causes convergence difficulties. A search procedure is proposed in this paper that is based on the successive solution of a relaxed linear model and the original nonconvex nonlinear problem. Several examples are presented to illustrate that the proposed method often yields global or near global optimum solutions. The model is also extended for selecting different treatment technologies and for handling membrane separation modules.