A Bayesian approach to probabilistic ecological risk assessment: risk comparison of nine toxic substances in Tokyo surface waters

Background, aim, and scope  

Quantitative risk comparison of toxic substances is necessary to decide which substances should be prioritized to achieve effective risk management. This study compared the ecological risk among nine major toxic substances (ammonia, bisphenol-A, chloroform, copper, hexavalent chromium, lead, manganese, nickel, and zinc) in Tokyo surface waters by adopting an integrated risk analysis procedure using Bayesian statistics.     

A tiered ecological risk assessment of three chlorophenols in Chinese surface waters

Introduction

The ecological risks posed by three chlorophenols (CPs), 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), and pentachlorophenol (PCP) in Chinese surface waters were assessed.

Materials and methods

This was achieved by applying a tiered ecological risk assessment (ERA) approach ranging from deterministic methods to probabilistic options to measured concentrations of CPs in surface water of seven major watersheds and three drainage regions in China and the chronic toxicity data for indigenous Chinese species.

Results and discussion

The results show that the risks of three chlorophenols are ranked PCP>2,4-DCP??2,4,6-TCP. PCP posed little ecological risk while 2,4-DCP and 2,4,6-TCP posed negligible or de minimis risk in Chinese surface water. However, the risks varied with different river basins, for example, PCP posed some ecological risk in the Yangtze, Huaihe, and Pearl Rivers. The magnitude of 2,4-DCP and 2,4,6-TCP pollution in North China was more serious than that in South China.

Conclusion

The probabilistic risk assessment approach, which can provide more information for risk managers and decision makers, was favored over the screening-level single-value estimate method. However, the results from all tiers of the ERA methods in the framework were consistent with each other.     

Modelling the fate of hydrophobic organic contaminants in a boreal forest catchment: A cross disciplinary approach to assessing diffuse pollution to surface waters

The fate of hydrophobic organic compounds (HOCs) in soils and waters in a northern boreal catchment was explored through the development of a chemical fate model in a well-characterised catchment system dominated by two land types: forest and mire. Input was based solely on atmospheric deposition, dominated by accumulation in the winter snowpack. Release from soils was governed by the HOC concentration in soil, the soil organic carbon fraction and soil-water DOC content. The modelled export of selected HOCs in surface waters ranged between 11 and 250 ng day⁻¹ during the snow covered period, compared to 200 and 9600 ng/d during snow-melt; highlighting the importance of the snow pack as a source of these chemicals. The predicted levels of HOCs in surface water were in reasonable agreement to a limited set of measured values, although the model tended to over predict concentrations of HOCs for the forested sub-catchment, by over an order of magnitude in the case of hexachlorobenzene and PCB 180. This possibly reflects both the heterogeneity of the forest soils and the complicated and changing hydrology experienced between the different seasons.     

Zoobenthos as indicators of ecological status in coastal brackish waters: a comparative study from the Baltic Sea

A new method for classifying soft-bottom zoobenthic assemblages along the Finnish coasts (northern Baltic Sea) is presented and tested against traditional physicochemical monitoring data in the complex Archipelago Sea. Although multivariate methods for assessing the state of the marine environment have become widely used, few numerical indices can operate over a wide salinity range. We compare indices currently in use and propose a new index, BBI (brackish water benthic index), for the low-saline and species-poor Baltic coastal waters. BBI offers a salinity-corrected tool for classification of the soft-bottom zoobenthos under the demands of the European Union Water Framework Directive.     

A model to assess the rate of evaporation of chemical compounds from surface waters

A model has been developed to assess the rate of evaporation of chemical compounds from surface waters. It is based on the two-boundary-layer model of Lewis and Whitman, on critically evaluated literature data and on specific experiments. The rate of evaporation is assessed as a function of the diffusion coefficient in air and water and of Henry's coefficient in water, being the physico-chemical parameters, and as a function of the wind speed, the water temperature and the water depth, being the environmental parameters.     

Field calibration of surface: A model of agricultural chemicals in surface waters

Abstract

Agricultural chemicals sporadically occur at detectable levels in the surface waters of intensively farmed watersheds. HSPF, a previously released model of agricultural chemicals in surface water, had been used to predict concentrations which were much higher (10 X) than those actually observed during monitoring studies. A new model, SURFACE, is described here which is much simpler than HSPF and gives better predictions of surface water concentrations. SURFACE uses PRZM, an EPA model, to calculate edge‐of‐field runoff losses and simple hydraulic routing algorithms to determine concentrations at the bottom of large river basins. In water systems sampled during 1985 and 1986, SURFACE predictions of annualized mean concentrations for alachlor, atrazine, cyanazine and metolachlor were within 0.09 ppb half of the time.     

Recovery from acidification in European surface waters: a view to the future

There is now overwhelming documentation of large-scale chemical recovery from surface water acidification in Europe, but to date there has been little documentation of biological recovery. Modelling studies based on current emission reduction plans in Europe indicate that there will be further chemical recovery. The uncertainties in these scenarios mainly relate to the future behavior of nitrogen in the ecosystem and the effects of climate change. Four major climate-related confounding factors that may influence the chemical and biological recovery process are: i) increased frequency and severity of sea-salt episodes; ii) increased frequency and severity of drought; iii) increased turnover of organic carbon; iv) increased mineralization of nitrogen. International cooperative work to abate acidification has so far been very successful, but there is still a long way to go, and many potential setbacks. It is essential that future development of water chemistry and aquatic biota in acidified waterbodies continue to be monitored in relation to further emission reductions of S and N and future effects of climate change.     

Organochlorine pesticides in the surface waters of Northern Greece

A survey undertaken in Northern Greece has shown that organochlorine pesticides are present in the surface waters. Surface water samples have been collected seasonally from four rivers and five lakes for a period of two years. Solid-phase extraction followed by gas chromatographic techniques with electron capture detection was used for the determination of the compounds. The most commonly encountered organochlorine pesticides in surface waters were the isomers of hexachlorocyclohexane, aldrin, dieldrin and endosulfan sulfate. In some cases the concentrations detected were higher than the qualitative target levels set by the European Union, especially for hexachlorocyclohexane and aldrin. The occurrence of these compounds in Greek surface waters can be attributed to intense agricultural activity as well as to transboundary pollution.     

Phosphorus-based metabolic pathway tracers in surface waters

Environmental Science and Pollution Research - Trophic status in surface waters has been mostly monitored by measuring soluble reactive phosphorus (SRP) and total phosphorus (TP). Additional to...     

Biological responses to the reversal of acidification in surface waters of the English Lake District

Declining sulphur deposition since the late 1970s has led to increases in pH in lakes and streams of the English Lake District (Cumbria, UK). To determine whether there have been biological responses to the chemical changes, we carried out surveys of stream macroinvertebrates and lake surface sediment diatoms, and compared the results with those from earlier surveys. Macroinvertebrate taxa in five streams (current average pH range 5.1-7.0) sampled in 1999 showed clear changes from those found during 1965/1966 and 1972. For three of the streams, more taxa were present in 1999 than recorded using comparable sampling methods in the 1960s and 1970s, despite lower numbers of individuals being recovered in 1999. Values of the Margalef diversity index could be calculated for both 1965-1972 and 1999 for four of the streams; the index was significantly greater in 1999 (P < 0.001) in three streams, and unchanged in one stream (the most acid). The 1999 survey revealed the presence of acid-sensitive taxa that had been absent in the earlier surveys, notably the three stoneflies Leuctra fusca, L. moselyi and Chloroperla tripunctata. Some taxa that had been present during 1965-1972 were absent in 1999, but few of these were acid-sensitive. Diatoms from the surface sediments of six lakes were classified according to their acid sensitivities. In three of the lakes sampled in 1999 there were more diatoms characteristic of circumneutral waters, and less acidophilic species than had been found in 1983-1985. In the remaining three lakes, no noticeable changes had occurred. Overall, the observed biological changes are qualitatively as expected for the observed increases in pH, and there have been no instances of biological change in the opposite direction. The results support the expectation that changes in freshwater ecological status can be reversed by decreasing the remote emissions of acidifying pollutants.     

Predicting diffuse-source transfers of surfactants to surface waters using SWAT

Chemicals present in domestic wastewater can adsorb to solid phase materials during sewage treatment. If biosolids (or sewage sludge) are applied to land, these chemicals can be transferred to soil. Under some circumstances they can also be transferred to surface waters during storm events either in solution or attached to sediment. In this paper we describe the utility of the SWAT 2000 model to estimate diffuse-source surface water exposure to "down-the-drain" chemicals. The model was applied hypothetically to predict the behaviour of linear alkylbenzene sulphonate (LAS), an anionic surfactant commonly used in household detergents, in a small catchment in Bedfordshire, UK, where it has previously been successfully validated for stream flow, sediments and pesticides. LAS transfers were estimated for two scenarios: (1) realistic and (2) reasonable worst case, based on assumptions on sludge application rates and the concentration of LAS in sludge. In addition, the sensitivity of the model output to the proportion of the catchment to which sludge is applied was established. Soil wetness and the total quantity of biosolids applied were the biggest determinants of chemical transport from the catchment. The potential of SWAT as a higher-tier tool in environmental risk assessments is discussed.     

Volatile organic compounds in the surface waters of northern Greece

An investigation into the occurrence of volatile organic compounds (VOCs) was conducted for a period of two years in the surface waters of Northern Greece. Samples from four rivers and five lakes were taken seasonally and analyzed for VOCs. The analysis has been performed by purge-and-trap (PAT) gas chromatographic-mass spectrometric (GC-MS) technique. The most commonly encountered VOCs in surface waters were chloroform, carbon tetrachloride, trichloroethylene, dichlorobromomethane, tetrachloroethylene, and chlorodibromomethane.     

The formation of singlet oxygen in surface waters

The photochemical formation of singlet oxygen in some Dutch surface waters has been investigated using the method developed by Zepp (1). However, when monitoring the consumption of oxygen beside that of 2,5-dimethylfuran (DMF), the compound added to chemically snare singlet oxygen, it was found that appreciable, but varying parts of DMF were used up by secondary reactions leading largely to the same products, viz. cis- and trans-diacetylethylene. When taking the oxygen consumption as a measure for the singlet oxygen production on the basis of the stoichiometry of the primary reaction, a fair correlation between the singlet oxygen production and the total organic carbon (TOC) content was found for this selection of Dutch surface water samples. The steady-state concentrations of singlet oxygen determined in this way were about one order of magnitude lower than those found by Zepp (1) and by Zafiriou (2).     

Atrazine removal by ozonation processes in surface waters

Abstract

Atrazine (6‐chloro‐N‐ethyl‐N'‐isopropyl‐1,3,5‐triazinedyl‐2,4‐diamine) was treated with ozone alone and in combination with hydrogen peroxide or UV radiation in three surface waters. Experiments were carried out in two bubble reactors operated continously. Variables investigated were the ozone partial pressure, temperature, pH, mass flow ratio of oxidants fed: hydrogen peroxide and ozone and the type of oxidation including UV radiation alone. Residence time for the aqueous phase was kept at 10 min. Concentrations of some intermediates, including deethylatrazine, deisopropylatrazine and deethyldeisopropylatrazine, were also followed. The nature of water, specifically the alkalinity and pH were found to be important variables that affected atrazine (ATZ) removal. Surface waters with low alkalinity and high pH allowed the highest removal of ATZ to be reached. There was an optimum hydrogen peroxide to ozone mass flow ratio that resulted in the highest ATZ removal in each surface water treated. This optimum was above the theoretical stoichiometry of the process. Therefore, to reach the maximum removal of ATZ in a O₃/H₂O₂ process, more hydrogen peroxide was needed in the surface waters treated than in ultrapure water under similar experimental conditions. In some cases, UV radiation alone resulted in the removal of ATZ higher than ozonation alone. This was likely due to the alkalinity of the surface water. Ozonation and UV radiation processes yield different amounts of hydrogen peroxide. Combined ozonations (O₃/H₂O₂ and O₃/UV) lead to ATZ removals higher than single ozonation or UV radiation but the formation of intermediates was higher.     

Atrazine removal by ozonation processes in surface waters

Atrazine (6-chloro-N-ethyl-N'-isopropyl-1,3,5-triazinedyl-2,4-diamine) was treated with ozone alone and in combination with hydrogen peroxide or UV radiation in three surface waters. Experiments were carried out in two bubble reactors operated continuously. Variables investigated were the ozone partial pressure, temperature, pH, mass flow ratio of oxidants fed: hydrogen peroxide and ozone and the type of oxidation including UV radiation alone. Residence time for the aqueous phase was kept at 10 min. Concentrations of some intermediates, including deethylatrazine, deisopropylatrazine and deethyldeisopropylatrazine, were also followed. The nature of water, specifically the alkalinity and pH were found to be important variables that affected atrazine (ATZ) removal. Surface waters with low alkalinity and high pH allowed the highest removal of ATZ to be reached. There was an optimum hydrogen peroxide to ozone mass flow ratio that resulted in the highest ATZ removal in each surface water treated. This optimum was above the theoretical stoichiometry of the process. Therefore, to reach the maximum removal of ATZ in a O3/H2O2 process, more hydrogen peroxide was needed in the surface waters treated than in ultrapure water under similar experimental conditions. In some cases, UV radiation alone resulted in the removal of ATZ higher than ozonation alone. This was likely due to the alkalinity of the surface water. Ozonation and UV radiation processes yield different amounts of hydrogen peroxide. Combined ozonations (O3/H2O2 and O3/UV) lead to ATZ removals higher than single ozonation or UV radiation but the formation of intermediates was higher.     

慧星试验对水体安全性分析研究

利用彗星试验检测苏南某湖泊湖心区、长江某取水口及其给水处理厂出水水样的遗传毒性,并对结果进行分析研究.结果表明,各水样均能引起DNA损伤,在丰水期致DNA损伤作用的大小顺序为给水厂出水水样＞湖泊水样＞长江取水口水样;在枯水期致DNA损伤作用的大小顺序为湖泊水样＞长江取水口水样＞给水厂出水水样.随着染毒剂量的加大,细胞损伤率增加,细胞受损的程度也在加重,并向3、4级损伤集中,呈明显的剂量-效应关系.     

Pesticides in the surface waters of the Camanducaia River watershed,Brazil

Abstract

Camanducaia River is part of the Piracicaba watershed responsible for pumping water into the Cantareira System, which is one of the main water sources for the metropolis of São Paulo and Campinas, Brazil. Intensive use of pesticides and hilly topography represents a situation of high risk for river water contamination. Therefore, water samples from 12 locations were collected along the Camanducaia River and its tributaries, over a period of 4?mo during the rainy season, and analyzed by GC-MS/MS or UPLC- MS/MS for the presence of 46 pesticides. Seven pesticides (fipronil, methyl parathion, metolachlor, atrazine, carbofuran, diuron, and simazine) were positively detected. Only atrazine (the most frequently detected) and diuron were present at concentrations above the limit of quantification of the analytical method (0.32 and 0.57?μg L^?1 for atrazine and diuron, respectively). Pesticides detection frequency was higher than expected for a river system where only 11.8% of the land area is under agriculture. The vulnerability of the Camanducaia basin to pesticide contamination is attributed to the high annual precipitation (> 1.5?m y^?1 in the headwaters), associated with topographical features (steep terrain) and soil types that favor surface runoff, which has been exacerbated by poor soil management practices.     

Field calibration of surface: a model of agricultural chemicals in surface waters

Agricultural chemicals sporadically occur at detectable levels in the surface waters of intensively farmed watersheds. HSPF, a previously released model of agricultural chemicals in surface water, had been used to predict concentrations which were much higher (10 X) than those actually observed during monitoring studies. A new model, SURFACE, is described here which is much simpler than HSPF and gives better predictions of surface water concentrations. SURFACE uses PRZM, an EPA model, to calculate edge-of-field runoff losses and simple hydraulic routing algorithms to determine concentrations at the bottom of large river basins. In water systems sampled during 1985 and 1986, SURFACE predictions of annualized mean concentrations for alachlor, atrazine, cyanazine and metolachlor were within 0.09 ppb half of the time.