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Environmental risk assessment of pesticides on aquatic life in Xiamen, China
Toxicology Letters 128 (2002) 45 – 53 www.elsevier.com/locate/toxlet
Review article
Environmental risk assessment of pesticides on aquatic life in Xiamen, China Davide Calamari a,*, Luoping Zhang b a
Department of Structural and Functional Biology, Uni6ersity of Insubria, Via J.H. Dunant, 21100 Varese, Italy b En6ironmental Science Research Center, Xiamen Uni6ersity, Xiamen, Fujian, China
Abstract This paper describes the results of the environmental risk assessment of the pesticides used in agriculture in Xiamen, China. The goal was to assess the impact on water resources, particularly on fisheries and mariculture. Data on ecotoxicological properties of the pesticides and their physico-chemical profile were collected. The simulation of the environmental behaviour of the pesticides in relation to the load applied onto the agricultural areas was done using the SoilFug model. Risk assessment was performed, pesticides approximate concentrations have been calculated, chemicals at highest risk were identified, and risk management measures were indicated. This study could represent a cost-effective method that may be used before engaging in expensive monitoring programs for pesticide use in developing countries, where analytical facilities are lacking. © 2002 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Risk assessment; Ecotoxicology; Pesticides effects; Aquatic toxicology
1. Introduction For the last few years the relevance of modelling environmental distribution and fate of chemical substances has increased exponentially in the scientific community and a number of models and modelling strategies have been proposed. In the meantime, in the regulatory community, evaluation and control of chemical substances has evolved from acceptable limits in effluents and/or quality criteria in various environmental media toward risk assessment proce* Corresponding author. E-mail addresses: [email protected] (D. Calamari), [email protected] (L. Zhang).
dures. Risk assessment is a process which involves hazard identification, effects assessment, exposure assessment and risk characterisation (Van Leeuwen and Hermens, 1995). This paper describes a practical application of models and modelling strategies in a process of risk assessment of pesticides. The Global Environmental Facility/United Nations Development Programme/International Maritime Organization (GEF/UNDP/IMO, 1995) has established a Regional Programme for the Prevention and Management of Marine Pollution in the East Asian Seas (MPP-EAS); three demonstration projects are located at Batangas Bay, Philippines, Xiamen, China and Malacca Strait. This paper describes the results of the environ-
0378-4274/02/$ - see front matter © 2002 Elsevier Science Ireland Ltd. All rights reserved. PII: S 0 3 7 8 - 4 2 7 4 ( 0 1 ) 0 0 5 3 2 - X
D. Calamari, L. Zhang / Toxicology Letters 128 (2002) 45–53
46
mental risk assessment of pesticides used in the Xiamen Area, China (GEF/UNDP/IMO MPPEAS and FAO, 1998). The objectives were: (1) to assess the impact of agricultural pesticides on fisheries and aquaculture; (2) to evaluate the ecotoxicological information on the different types of pesticides, including the quantity and frequency of application by type of agricultural crop on an annual basis; and (3) to recommend appropriate measures or actions to be taken to address the potential impacts.
2. Materials and methods The document produced by the MPP-EAS ‘Coastal Environmental Profile of Xiamen’ (GEF/ UNDP/IMO, 1995) was the major source of data for geographic features, climate and rainfall, agricultural land uses, and soil characteristics. Pesticide loads data for the year 1996 have been obtained from the Supply Company for Agricultural Manufacture Material of Xiamen City. Data on ecotoxicological effects and physicochemical profiles of the pesticides were taken from Tomlin (1994) and Howard (1991a,b). Halflife figures were selected, taking into account the high annual average temperatures of Xiamen Area. The modelling strategy has been suggested in a series of papers by Mackay et al. (1996a,b,c). The model utilised for the calculation of predicted
environmental concentration (PEC) was the SoilFug (Di Guardo et al., 1994a,b).
2.1. Geographic features, climate and rainfall distribution The total land area of the Xiamen Municipality’s administrative jurisdiction, including islands, is 1516 km2; it is located in the southern coast of the Fujian province. The bay has a complex structure with several islands and different seas, i.e. the West Harbour, Maulan Bay Tong’an Bay Jiulongjiang River Estuary, the Southern Seas and the Eastern Seas. The pesticide loads from Xiamen drainage basin are directly influencing Western Seas, Tong’an Bay and the Eastern Seas, where aquaculture facilities are located. The average annual temperature is 20.9 °C; the warmest month is July with 28.4 °C and the coldest period is January/February with an average 12.6 °C. The rainfall has an annual average of 1143 mm. Annual rainfall distribution for 1996, obtained by local meteorological services, is given, appropriately subdivided for the use in the SoilFug model, in Table 1.
2.2. Agricultural land uses, soil characteristics and quantification of pesticides loads In the last years Xiamen has undergone rapid socioeconomic development, with the construction of a port, development of mariculture, indus-
Table 1 Rainfall data from late April to December in 1996 Rain event
Day to rain (days)
Duration (days)
Amount of rainfall (mm in)
Amount of runoff (mm out)
1 2 3 4 5 6 7 8 9
1 9 14 19 31 12 3 19 44
2 11 7 5 15 3 9 3 3
75 35 139 56 453 22 80 22 30
37.5 17.5 69.5 28.0 226.5 11.0 40.0 11.0 15.0
D. Calamari, L. Zhang / Toxicology Letters 128 (2002) 45–53
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Table 2 Pesticides consumption in Xiamen Pesticides
Quantity (t/y)
Fungicides total Carbendazim Copper sulfate Thiophanate–methyl
50 15 10 15
% a.i.
Quantity a.i. (t/y)
Application (kg/ha)
Application a.i. (kg/ha)
50 96 70
7.5 9.6 10.5
1.5 0.75–1.125 1.5
0.75 0.72–1.08 1.05
12.0 6
1.5–1.85 15.0
0.9–1.11 1.5
Herbicides total Butachlor Glyphosate Insecticides total
100 20 60 1000
60 10
Organochlorines Dicofol
20
20
4
1.5
0.3
180 34.0 50 16 0.6
3.0 1.5–3.0 1.5 1.5–3.0 22.5–37.5
2.4*8 0.6–1.2 0.75 0.6–1.2 0.34–0.56
3.0–4.5
0.09–0.135
Organophosphates Dichlorvos Dimethoate Methamidophos Omethoate Parathion–methyl
225 85 100 40 40
80 40 50 40 1.5
Carbamates Carbofuran
215
3
6.5
trialisation and increased trading. The cultivated soil in the Municipality of the Xiamen area was 427 km2. Pesticides are applied only on major crops: rice (29.8 km2), peanuts (12.6 km2), vegetable (22.2 km2) and fruits (32 km2); other cultures are utilising only limited quantities of pesticides. The average soil characteristics that were used for the simulation are: soil depth 0.3 m, field capacity 0.3, porosity 0.5, organic carbon content 0.02%, total basin area 1405 km2 (GEF/ UNDP/IMO, 1995). Herbicides are applied only to rice, fungicides and carbamates to any crops, organophosphates mainly to rice, and organochlorines on fruit and vegetables. The application rates reflect the standard agrochemical use of the different products. Table 2 lists the most important pesticides used in Xiamen, by quantity, % of active ingredient, active ingredient sold per year in tons, application rate in kg/ha for the product and active ingredient in kg/ha. Dichlorvos has a very high consumption being applied up to eight times per year at a rate of 2.4 kg/ha.
3. Results
3.1. Simulated treatments and loads of pesticides It has been decided to simulate only the most relevant chemicals, as few of the pesticides reported in Table 2 were applied in significant quantities. A further consideration has been that chemicals belonging to the same group have the same mode of action and could be considered to be toxicologically additive to aquatic life when present in mixtures (Vighi and Calamari, 1996). Therefore, a single substance in this context could represent a chemical group, despite differences in the level of acute toxicity. Among the fungicides, thiophanate– methyl is the one most used (10.5 t/year). However, for the simulation it was decided to include carbendazim (7.5 t/year) because of its high toxicity for fish and Daphnia. Copper sulphate was excluded from the evaluation as if it is not applied directly to water it has limited risk due to metal absorption onto soil.
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Butachlor used in 12 t/year was taken as representative for herbicides. Glyphosate was not considered despite its high toxicity on many plants, as it is a short living molecule and has very low mobility due to its dissociation (Grossbard and Atkinson, 1985). The acaricide dicofol has been included in the simulation as the only representative of organochlorine compounds and due to its similarity to DDT, from which it is prepared. It has to be noticed that its half-life is shorter than that of DDT. Dichlorvos has been taken as the most commonly used organophosphate, 180 t/year of active ingredient and associated with the very similar methamidophos (50 t/year), thereby leading to a total organophosphate load of 230 t/year. Types of crops, quantities applied per hectare, number of treatments and treated areas were summarised in Table 3. Rainfall simulations have been made considering the data from late April to December 1996 (Table 1). Table 4 summarises physico-chemical properties of the pesticides utilised for risk assessment modelling in the Xiamen area with the SoilFug model. An initial generic evaluation of a chemical substance is suggested in the Equilibrium Criteria series of papers (Mackay et al., 1996a,b,c). The following stage of the evaluation requires highly site-specific models, like SoilFug, where local conditions are taken into account. It is, however, to be stated that exact scenarios for simulation could be built in only with extreme difficulty, as the number of variables inherent with the model do not allow precise scenarios (e.g. a farmer is treating one day, another a few days after, local soil differences etc.).
3.2. The SoilFug model and its application for estimating pesticide runoff SoilFug is a model for the prediction of potential surface water contamination derived from pesticide use on agricultural fields. In a number of cases this model has been validated for research purposes, see the papers of Di Guardo et al. (1994a,b) and Barra et al. (1995). The model is simulating at the scale of a drainage basin and calculates the partition of the chemical applied to the soil phases and its possible contamination of surface water during the rain events. A rain event is defined as a period of time starting with a rainfall and ending with the return to the background water level in the adjacent stream. The model requires a limited amount of chemical and environmental data, and it furnishes an average concentration of pesticide in outflowing waters. SoilFug is essentially an unsteady-state but equilibrium event model. This is because it takes into account the disappearance of the chemicals according to different phenomena (degradation, volatilisation, runoff), but then calculates the partition among the different phases of the soil, according to a level 1 fugacity calculation (Mackay, 1991) in the rain event period. Briefly, the model considers the four different compartments in the soil: soil air, soil water, organic matter and mineral matter. For each of these compartments a capacity (Z) can be calculated and therefore the fugacity can be worked out, once the volume and the chemical input are known. From the fugacity, chemical amounts and concentrations in each compartment can be calculated.
Table 3 Simulated treatments and loads of pesticides Pesticides
Total (a.i./y)
Fungicides 18 Herbicides 12 Organochlorines 4 Organophosphate 230 s Carbamates 6.5
Types of crop
Application (kg/ha)
Number of treatments
Treated area (ha)
Simulated treatments
Any Rice Fruit, vegetable Mainly rice
1.0 1.0 0.3 2.4
1 1 1 8
18 000 12 000 12 000 12 000
1 1 0.3 2.4*8
Any
0.1
2
30 000
0.2
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Table 4 Properties of pesticides Pesticides
MW (g/mol)
Water solubility (mg/l)
Vapour pressure (Pa)
Bioaccumulation (log Kow)
Soil persistence (t/2)
Carbendazim Butachlor Dicofol Dichlorvos Carbofuran
191.2 311.9 370.5 221.0 221.3
8 20 0.8 8e3 320
0.09×10−3 0.6×10−3 0.53×10−3 2.1 7.2×10−5
1.5 2.5 4.28 1.9 1.52
8–32 42–70 60–80 7 30–60
The input data required for the soil scenario description of the model were temperature, depth, volume fractions of air in soil and of water in soil at field capacity, organic carbon content, area of the basin, and the number of simulations, i.e. the number of rain events. The mass balance of the water was calculated on the basis of rain events and outflow. The basic data for the water input calculation were the number of rain events, the duration of the rain events and the quantity of rain. Each rain event had to be sufficient to produce a measurable outflow, since the model was required to estimate the quantity of pesticides in advective water moving out of the basin. The evaporation rates of 50% were estimated to be reasonably representative of the basin. Other parameters required for running the model were the periods of and numbers of pesticides applications, pesticides dosage, days between pesticide applications and rain events, area treated, and half-life of the pesticides. In assembling these values for the SoilFug model, it was assumed to simulate the worst case, therefore, all the treatments done in the rainy season, with the maximum runoff and maximum pesticide loads. For the particular case of dichlorvos (up to eight treatments for a year in normal conditions) a special simulation was run considering three treatments in about 2 weeks. From the sets of data described above, the model was able to calculate the average concentrations of the different pesticides in water during each rain event, taking into account not only the partitioning phenomena between soil and water, but also the estimated persistence of each molecule (i.e. its half-life). The final output was a series of graphs showing the predicted concentration of the differ-
ent pesticides at the basin outlet which, in this case, was represented by the contact point between fresh and saline waters of the Xiamen Seas. These graphs are presented in Figs. 1–3 and are discussed below, together with the ecotoxicological significance of the estimated concentrations. For the exact timing of each rain event make reference to days indicated in Table 1.
3.3. Risk assessment for aquatic life The results of the SoilFug model calculations demonstrated that certain quantities of the most commonly used pesticides could have been present in the estuaries of the main rivers entering Xiamen Seas at analytically detectable levels. The substances under study have limited bioaccumulation potential, according to their Kow values, except dicofol. The ecotoxicological significance of the calculated concentration is discussed separately for the five representative chemicals. The fungicide carbendazim has a calculated concentration in river water at the outlet of about 45 mg/l, acute toxicity for Daphnia being 130 mg/l; the substance is dissipated from soil mainly by degradation and partially by runoff. Butachlor has a calculated concentration of 8 mg/l while acute toxicity to aquatic organisms is of the order of hundreds mg/l. Dicofol is persistent for about 1 year in soil but due to its affinity for soil the leaching is limited; water concentration was 0.04 mg/l, much lower then toxic levels. A certain amount of bioaccumulation could be expected (Log Kow 4.3), but it has been demonstrated that it can be metabolised by mammals and birds; no data have been found on fish.
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Carbofuran is dissipated via degradation and runoff. Calculated water concentration has a peak of 15 mg/l that is equal to acute toxicity to Daphnia. In this condition, the risk ratio for danger to aquatic organisms is high. If risk assessment is made simply by examining
the ratio between PEC and acute toxicity data for the four molecules studied, only carbofuran shows a direct risk for the aquatic fauna, the result not being a cause of concern for the other compounds. If, however, a more severe criterion is used to evaluate the model predictions, e.g. by
Fig. 1. Concentration trends of carbendazim and butachlor in soil, water and losses calculated by SoilFug model.
D. Calamari, L. Zhang / Toxicology Letters 128 (2002) 45–53
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Fig. 2. Concentration trends of dicofol and carbofuran in soil, water and losses calculated by SoilFug model.
applying the non-observed effect level, simply calculated assuming a factor of 10 in respect to acute toxicity, a risk factor can be expected for carbendazi. It can therefore be concluded that, on the basis of acute toxicity criteria effect carbofuran is
at risk of causing acute damage. On the basis of an assumed no effect level of a factor of 0.1 applied to acute toxicity data, carbendazim also falls into the group of compounds that could provoke risk on the aquatic fauna. In the Xiamen
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D. Calamari, L. Zhang / Toxicology Letters 128 (2002) 45–53
area, rivers are short and quickly enter the sea where mariculture is practised; risk of mass mortality, particularly of larvae of molluscs, could therefore be envisaged, as larvae has similar sensitivity to Daphnia to pesticides. A special case is that of dichlorvos where several applications are made according to normal agricultural practices. The simulation of three sequential applications has been made. The results of the sum of the three treatments are shown in Fig. 3. Dichlorvos, despite its short half-life, could be present in water at peaks of 40– 20 mg/l; for a period of several days (integrating the various runoff contributions). Considering the higher total quantity applied (230 t/year), the application rate of 2.4 kg/ha and that treatments are repeated up to eight times per year, this substance has probably caused and will continue to cause massive aquatic organism mortality. Its acute toxicity reported by Tomlin (1994) is 0.19 mg/l for Daphnia. Because this figure was very low, a literature survey was made and the low value was confirmed. In fact, Vighi et al. (1991) reported 0.22 mg/l while older data referred to 0.05 mg/l (Mayer and Ellersieck, 1986).
4. Conclusions Through the present investigation, an initial risk assessment of the impact of agricultural pesticides has been made. This study could represent a cost-effective method that may be used before
Fig. 3. Concentration trends of water for three repeated treatments of dichlorvos calculated by SoilFug model.
engaging in many expensive monitoring programs. The findings could be useful to sustainable development of agriculture and risk assessment for pesticide use in developing countries, where analytical facilities are lacking. Up to now, exact ratios of Predicted Environmental Distribution/No Observed Effect Level or Water Quality Objective have not been calculated. In our opinion, this ratio should be calculated only when the margin of uncertainty is reduced as low as possible. In the described procedure, several factors of uncertainty were present. The estimation of loads of pesticides, the timing of the application in the field, the water balance (input/ output), the variability of soils etc., are just a few examples of the environmental variable influence on the model. The environmental persistence, the correctness and precision of physico-chemical data, as well as the limited availability and the selection of the ecotoxicological data are examples of uncertainty regarding the molecular characteristics. It is to be stated however that even if precision were lacking, pesticides at highest risk have been certainly identified as well as trends and approximate concentrations, therefore risk management measures could be indicated. The situation with respect to the pesticides use in the Xiamen agricultural area is of major concern. The total load of pesticides on agricultural soil is 27 kg/ha on average. If the calculation is made on the overall catchment area, the load is still very high, 7.6 kg/ha. These data are very high even if compared with intensively exploited agricultural areas. The pesticide market is dominated by organophosphate insecticides, which are very toxic to aquatic fauna and very mobile (although short living). Fish and aquatic organism kills have been reported (GEF/UNDP/IMO, 1995), even if their causes have not been established. Some of these chemicals are volatile and therefore there is a potential risk to human health. A master plan to improve and change the actual agricultural practices should therefore be prepared. Major points could be the rotation of insecticide treatments (e.g. organophosphates alternated with pyrethroids), the selection of less
D. Calamari, L. Zhang / Toxicology Letters 128 (2002) 45–53
impacting and less mobile products (e.g. other organophosphates, synthetic pyrethroids, pseudopyrethroids), and the introduction of crop rotation systems and integrated pest management practices. In conclusion, the present state of pesticide use in the Xiamen area is a very high risk for the aquatic environment and is in conflict with aquatic resources utilisation. For sustainable development of the area, relevant remedial measures should be quickly undertaken.
Acknowledgements The authors wish to thank the Food and Agriculture Organization of the United Nations (FAO), and the GEF/UNDP/IMO Regional Programme for the Prevention and Management of Marine Pollution in East Asian Seas and its Programme Manager Chua Thia-Eng for the support of this investigation and for the permission to use material from a project report compiled by the first author (GEF/UNDP/IMO MPP-EAS and FAO, 1998).
References Barra, R., Vighi, M., Di Guardo, A., 1995. Prediction of runoff of chloridazon and chlorpyrifos in an agricultural watershed in Chile. Chemosphere 30, 485 –500. Di Guardo, A., Calamari, D., Zanin, G., Consalter, A., Mackay, D., 1994a. A fugacity model of pesticide runoff to surface water: development and validation. Chemosphere 28, 511 – 531. Di Guardo, A., Williams, R.J., Matthiessen, P., Brooke, N., Calamari, D., 1994b. Simulation of pesticide runoff at Rosemaund Farm (UK) using the soil fug model. Environ. Sci. Pollut. Res. 1, 151 –160.
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GEF/UNDP/IMO, 1995. Coastal Environmental Profile of Xiamen. Regional Programme for the Prevention and Management of East Asian Seas, Manila, Philippines. GEF/UNDP/IMO MPP-EAS and FAO, 1998. Initial Environmental Risk Assessment of Pesticides in the Batangas Bay Region, Philippines and the Xiamen Seas, China. Technical Report No. 16. Regional Programme for the Prevention and Management of East Asian Seas, Manila, Philippines. Grossbard, E., Atkinson, D. (Eds.), 1985. The Herbicide Glyphosate, Butterworths, London. Howard, P.H., 1991a. Handbook of Environmental Fate and Exposure Data for Organic Chemicals, vol. 3. Pesticides. Lewis, Chelsea, MI. Howard, P.H., 1991b. Handbook of Environmental Degradation Rates. Lewis, Chelsea, MI. Mackay, D., 1991. Multimedia Environmental Models. The Fugacity Approach. Lewis, Chelsea, MI. Mackay, D., Di Guardo, A., Paterson, S., Kicsi, G., Cowan, C.E., 1996a. Assessing the fate of new and existing chemicals: A five-stage process. Environ. Toxicol. Chem. 15, 1618 – 1626. Mackay, D., Di Guardo, A., Paterson, S., Kicsi, G., Cowan, C.E., 1996b. Evaluating the environmental fate of a variety of types of chemicals using the EQC model. Environ. Toxicol. Chem. 15, 1627 – 1637. Mackay, D., Di Guardo, A., Paterson, S., Kicsi, G., Cowan, C.E., Kane, D.M., 1996c. Assessment of chemical fate in the environment using evaluative, regional and local-scale models: illustrative application to chlorobenzene and linear alkylbenzene sulfonates. Environ. Toxicol. Chem. 15, 1638 – 1648. Mayer, F.L., Ellersieck, M.R., 1986. Manual of Acute Toxicity: Interpretation and Data Base for 410 Chemicals and 66 Species of Freshwater Animals, Research Publication of the US Department of the Interior, No. 160. Tomlin, C. (Ed.), 1994. The Pesticide Manual, 10th Ed., British Crop Protection Council, Farnham, Surrey/UK. Van Leeuwen, C.J., Hermens, J.L.M., 1995. Risk Assessment of Chemicals. Kluwer Academic Publishers, Dordrecht, The Netherlands. Vighi, M., Calamari, D., 1996. Quality objectives for aquatic life: the problem of mixtures of chemical substances. Hum. Ecol. Risk Assess. 2, 412 – 418. Vighi, M., Masoero, M., Calamari, D., 1991. QSARs for toxicity of organophosphorus pesticides to Daphnia and honeybees. Sci. Total Environ. 109/110, 605 – 622.
Review article
Environmental risk assessment of pesticides on aquatic life in Xiamen, China Davide Calamari a,*, Luoping Zhang b a
Department of Structural and Functional Biology, Uni6ersity of Insubria, Via J.H. Dunant, 21100 Varese, Italy b En6ironmental Science Research Center, Xiamen Uni6ersity, Xiamen, Fujian, China
Abstract This paper describes the results of the environmental risk assessment of the pesticides used in agriculture in Xiamen, China. The goal was to assess the impact on water resources, particularly on fisheries and mariculture. Data on ecotoxicological properties of the pesticides and their physico-chemical profile were collected. The simulation of the environmental behaviour of the pesticides in relation to the load applied onto the agricultural areas was done using the SoilFug model. Risk assessment was performed, pesticides approximate concentrations have been calculated, chemicals at highest risk were identified, and risk management measures were indicated. This study could represent a cost-effective method that may be used before engaging in expensive monitoring programs for pesticide use in developing countries, where analytical facilities are lacking. © 2002 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Risk assessment; Ecotoxicology; Pesticides effects; Aquatic toxicology
1. Introduction For the last few years the relevance of modelling environmental distribution and fate of chemical substances has increased exponentially in the scientific community and a number of models and modelling strategies have been proposed. In the meantime, in the regulatory community, evaluation and control of chemical substances has evolved from acceptable limits in effluents and/or quality criteria in various environmental media toward risk assessment proce* Corresponding author. E-mail addresses: [email protected] (D. Calamari), [email protected] (L. Zhang).
dures. Risk assessment is a process which involves hazard identification, effects assessment, exposure assessment and risk characterisation (Van Leeuwen and Hermens, 1995). This paper describes a practical application of models and modelling strategies in a process of risk assessment of pesticides. The Global Environmental Facility/United Nations Development Programme/International Maritime Organization (GEF/UNDP/IMO, 1995) has established a Regional Programme for the Prevention and Management of Marine Pollution in the East Asian Seas (MPP-EAS); three demonstration projects are located at Batangas Bay, Philippines, Xiamen, China and Malacca Strait. This paper describes the results of the environ-
0378-4274/02/$ - see front matter © 2002 Elsevier Science Ireland Ltd. All rights reserved. PII: S 0 3 7 8 - 4 2 7 4 ( 0 1 ) 0 0 5 3 2 - X
D. Calamari, L. Zhang / Toxicology Letters 128 (2002) 45–53
46
mental risk assessment of pesticides used in the Xiamen Area, China (GEF/UNDP/IMO MPPEAS and FAO, 1998). The objectives were: (1) to assess the impact of agricultural pesticides on fisheries and aquaculture; (2) to evaluate the ecotoxicological information on the different types of pesticides, including the quantity and frequency of application by type of agricultural crop on an annual basis; and (3) to recommend appropriate measures or actions to be taken to address the potential impacts.
2. Materials and methods The document produced by the MPP-EAS ‘Coastal Environmental Profile of Xiamen’ (GEF/ UNDP/IMO, 1995) was the major source of data for geographic features, climate and rainfall, agricultural land uses, and soil characteristics. Pesticide loads data for the year 1996 have been obtained from the Supply Company for Agricultural Manufacture Material of Xiamen City. Data on ecotoxicological effects and physicochemical profiles of the pesticides were taken from Tomlin (1994) and Howard (1991a,b). Halflife figures were selected, taking into account the high annual average temperatures of Xiamen Area. The modelling strategy has been suggested in a series of papers by Mackay et al. (1996a,b,c). The model utilised for the calculation of predicted
environmental concentration (PEC) was the SoilFug (Di Guardo et al., 1994a,b).
2.1. Geographic features, climate and rainfall distribution The total land area of the Xiamen Municipality’s administrative jurisdiction, including islands, is 1516 km2; it is located in the southern coast of the Fujian province. The bay has a complex structure with several islands and different seas, i.e. the West Harbour, Maulan Bay Tong’an Bay Jiulongjiang River Estuary, the Southern Seas and the Eastern Seas. The pesticide loads from Xiamen drainage basin are directly influencing Western Seas, Tong’an Bay and the Eastern Seas, where aquaculture facilities are located. The average annual temperature is 20.9 °C; the warmest month is July with 28.4 °C and the coldest period is January/February with an average 12.6 °C. The rainfall has an annual average of 1143 mm. Annual rainfall distribution for 1996, obtained by local meteorological services, is given, appropriately subdivided for the use in the SoilFug model, in Table 1.
2.2. Agricultural land uses, soil characteristics and quantification of pesticides loads In the last years Xiamen has undergone rapid socioeconomic development, with the construction of a port, development of mariculture, indus-
Table 1 Rainfall data from late April to December in 1996 Rain event
Day to rain (days)
Duration (days)
Amount of rainfall (mm in)
Amount of runoff (mm out)
1 2 3 4 5 6 7 8 9
1 9 14 19 31 12 3 19 44
2 11 7 5 15 3 9 3 3
75 35 139 56 453 22 80 22 30
37.5 17.5 69.5 28.0 226.5 11.0 40.0 11.0 15.0
D. Calamari, L. Zhang / Toxicology Letters 128 (2002) 45–53
47
Table 2 Pesticides consumption in Xiamen Pesticides
Quantity (t/y)
Fungicides total Carbendazim Copper sulfate Thiophanate–methyl
50 15 10 15
% a.i.
Quantity a.i. (t/y)
Application (kg/ha)
Application a.i. (kg/ha)
50 96 70
7.5 9.6 10.5
1.5 0.75–1.125 1.5
0.75 0.72–1.08 1.05
12.0 6
1.5–1.85 15.0
0.9–1.11 1.5
Herbicides total Butachlor Glyphosate Insecticides total
100 20 60 1000
60 10
Organochlorines Dicofol
20
20
4
1.5
0.3
180 34.0 50 16 0.6
3.0 1.5–3.0 1.5 1.5–3.0 22.5–37.5
2.4*8 0.6–1.2 0.75 0.6–1.2 0.34–0.56
3.0–4.5
0.09–0.135
Organophosphates Dichlorvos Dimethoate Methamidophos Omethoate Parathion–methyl
225 85 100 40 40
80 40 50 40 1.5
Carbamates Carbofuran
215
3
6.5
trialisation and increased trading. The cultivated soil in the Municipality of the Xiamen area was 427 km2. Pesticides are applied only on major crops: rice (29.8 km2), peanuts (12.6 km2), vegetable (22.2 km2) and fruits (32 km2); other cultures are utilising only limited quantities of pesticides. The average soil characteristics that were used for the simulation are: soil depth 0.3 m, field capacity 0.3, porosity 0.5, organic carbon content 0.02%, total basin area 1405 km2 (GEF/ UNDP/IMO, 1995). Herbicides are applied only to rice, fungicides and carbamates to any crops, organophosphates mainly to rice, and organochlorines on fruit and vegetables. The application rates reflect the standard agrochemical use of the different products. Table 2 lists the most important pesticides used in Xiamen, by quantity, % of active ingredient, active ingredient sold per year in tons, application rate in kg/ha for the product and active ingredient in kg/ha. Dichlorvos has a very high consumption being applied up to eight times per year at a rate of 2.4 kg/ha.
3. Results
3.1. Simulated treatments and loads of pesticides It has been decided to simulate only the most relevant chemicals, as few of the pesticides reported in Table 2 were applied in significant quantities. A further consideration has been that chemicals belonging to the same group have the same mode of action and could be considered to be toxicologically additive to aquatic life when present in mixtures (Vighi and Calamari, 1996). Therefore, a single substance in this context could represent a chemical group, despite differences in the level of acute toxicity. Among the fungicides, thiophanate– methyl is the one most used (10.5 t/year). However, for the simulation it was decided to include carbendazim (7.5 t/year) because of its high toxicity for fish and Daphnia. Copper sulphate was excluded from the evaluation as if it is not applied directly to water it has limited risk due to metal absorption onto soil.
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Butachlor used in 12 t/year was taken as representative for herbicides. Glyphosate was not considered despite its high toxicity on many plants, as it is a short living molecule and has very low mobility due to its dissociation (Grossbard and Atkinson, 1985). The acaricide dicofol has been included in the simulation as the only representative of organochlorine compounds and due to its similarity to DDT, from which it is prepared. It has to be noticed that its half-life is shorter than that of DDT. Dichlorvos has been taken as the most commonly used organophosphate, 180 t/year of active ingredient and associated with the very similar methamidophos (50 t/year), thereby leading to a total organophosphate load of 230 t/year. Types of crops, quantities applied per hectare, number of treatments and treated areas were summarised in Table 3. Rainfall simulations have been made considering the data from late April to December 1996 (Table 1). Table 4 summarises physico-chemical properties of the pesticides utilised for risk assessment modelling in the Xiamen area with the SoilFug model. An initial generic evaluation of a chemical substance is suggested in the Equilibrium Criteria series of papers (Mackay et al., 1996a,b,c). The following stage of the evaluation requires highly site-specific models, like SoilFug, where local conditions are taken into account. It is, however, to be stated that exact scenarios for simulation could be built in only with extreme difficulty, as the number of variables inherent with the model do not allow precise scenarios (e.g. a farmer is treating one day, another a few days after, local soil differences etc.).
3.2. The SoilFug model and its application for estimating pesticide runoff SoilFug is a model for the prediction of potential surface water contamination derived from pesticide use on agricultural fields. In a number of cases this model has been validated for research purposes, see the papers of Di Guardo et al. (1994a,b) and Barra et al. (1995). The model is simulating at the scale of a drainage basin and calculates the partition of the chemical applied to the soil phases and its possible contamination of surface water during the rain events. A rain event is defined as a period of time starting with a rainfall and ending with the return to the background water level in the adjacent stream. The model requires a limited amount of chemical and environmental data, and it furnishes an average concentration of pesticide in outflowing waters. SoilFug is essentially an unsteady-state but equilibrium event model. This is because it takes into account the disappearance of the chemicals according to different phenomena (degradation, volatilisation, runoff), but then calculates the partition among the different phases of the soil, according to a level 1 fugacity calculation (Mackay, 1991) in the rain event period. Briefly, the model considers the four different compartments in the soil: soil air, soil water, organic matter and mineral matter. For each of these compartments a capacity (Z) can be calculated and therefore the fugacity can be worked out, once the volume and the chemical input are known. From the fugacity, chemical amounts and concentrations in each compartment can be calculated.
Table 3 Simulated treatments and loads of pesticides Pesticides
Total (a.i./y)
Fungicides 18 Herbicides 12 Organochlorines 4 Organophosphate 230 s Carbamates 6.5
Types of crop
Application (kg/ha)
Number of treatments
Treated area (ha)
Simulated treatments
Any Rice Fruit, vegetable Mainly rice
1.0 1.0 0.3 2.4
1 1 1 8
18 000 12 000 12 000 12 000
1 1 0.3 2.4*8
Any
0.1
2
30 000
0.2
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Table 4 Properties of pesticides Pesticides
MW (g/mol)
Water solubility (mg/l)
Vapour pressure (Pa)
Bioaccumulation (log Kow)
Soil persistence (t/2)
Carbendazim Butachlor Dicofol Dichlorvos Carbofuran
191.2 311.9 370.5 221.0 221.3
8 20 0.8 8e3 320
0.09×10−3 0.6×10−3 0.53×10−3 2.1 7.2×10−5
1.5 2.5 4.28 1.9 1.52
8–32 42–70 60–80 7 30–60
The input data required for the soil scenario description of the model were temperature, depth, volume fractions of air in soil and of water in soil at field capacity, organic carbon content, area of the basin, and the number of simulations, i.e. the number of rain events. The mass balance of the water was calculated on the basis of rain events and outflow. The basic data for the water input calculation were the number of rain events, the duration of the rain events and the quantity of rain. Each rain event had to be sufficient to produce a measurable outflow, since the model was required to estimate the quantity of pesticides in advective water moving out of the basin. The evaporation rates of 50% were estimated to be reasonably representative of the basin. Other parameters required for running the model were the periods of and numbers of pesticides applications, pesticides dosage, days between pesticide applications and rain events, area treated, and half-life of the pesticides. In assembling these values for the SoilFug model, it was assumed to simulate the worst case, therefore, all the treatments done in the rainy season, with the maximum runoff and maximum pesticide loads. For the particular case of dichlorvos (up to eight treatments for a year in normal conditions) a special simulation was run considering three treatments in about 2 weeks. From the sets of data described above, the model was able to calculate the average concentrations of the different pesticides in water during each rain event, taking into account not only the partitioning phenomena between soil and water, but also the estimated persistence of each molecule (i.e. its half-life). The final output was a series of graphs showing the predicted concentration of the differ-
ent pesticides at the basin outlet which, in this case, was represented by the contact point between fresh and saline waters of the Xiamen Seas. These graphs are presented in Figs. 1–3 and are discussed below, together with the ecotoxicological significance of the estimated concentrations. For the exact timing of each rain event make reference to days indicated in Table 1.
3.3. Risk assessment for aquatic life The results of the SoilFug model calculations demonstrated that certain quantities of the most commonly used pesticides could have been present in the estuaries of the main rivers entering Xiamen Seas at analytically detectable levels. The substances under study have limited bioaccumulation potential, according to their Kow values, except dicofol. The ecotoxicological significance of the calculated concentration is discussed separately for the five representative chemicals. The fungicide carbendazim has a calculated concentration in river water at the outlet of about 45 mg/l, acute toxicity for Daphnia being 130 mg/l; the substance is dissipated from soil mainly by degradation and partially by runoff. Butachlor has a calculated concentration of 8 mg/l while acute toxicity to aquatic organisms is of the order of hundreds mg/l. Dicofol is persistent for about 1 year in soil but due to its affinity for soil the leaching is limited; water concentration was 0.04 mg/l, much lower then toxic levels. A certain amount of bioaccumulation could be expected (Log Kow 4.3), but it has been demonstrated that it can be metabolised by mammals and birds; no data have been found on fish.
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Carbofuran is dissipated via degradation and runoff. Calculated water concentration has a peak of 15 mg/l that is equal to acute toxicity to Daphnia. In this condition, the risk ratio for danger to aquatic organisms is high. If risk assessment is made simply by examining
the ratio between PEC and acute toxicity data for the four molecules studied, only carbofuran shows a direct risk for the aquatic fauna, the result not being a cause of concern for the other compounds. If, however, a more severe criterion is used to evaluate the model predictions, e.g. by
Fig. 1. Concentration trends of carbendazim and butachlor in soil, water and losses calculated by SoilFug model.
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Fig. 2. Concentration trends of dicofol and carbofuran in soil, water and losses calculated by SoilFug model.
applying the non-observed effect level, simply calculated assuming a factor of 10 in respect to acute toxicity, a risk factor can be expected for carbendazi. It can therefore be concluded that, on the basis of acute toxicity criteria effect carbofuran is
at risk of causing acute damage. On the basis of an assumed no effect level of a factor of 0.1 applied to acute toxicity data, carbendazim also falls into the group of compounds that could provoke risk on the aquatic fauna. In the Xiamen
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area, rivers are short and quickly enter the sea where mariculture is practised; risk of mass mortality, particularly of larvae of molluscs, could therefore be envisaged, as larvae has similar sensitivity to Daphnia to pesticides. A special case is that of dichlorvos where several applications are made according to normal agricultural practices. The simulation of three sequential applications has been made. The results of the sum of the three treatments are shown in Fig. 3. Dichlorvos, despite its short half-life, could be present in water at peaks of 40– 20 mg/l; for a period of several days (integrating the various runoff contributions). Considering the higher total quantity applied (230 t/year), the application rate of 2.4 kg/ha and that treatments are repeated up to eight times per year, this substance has probably caused and will continue to cause massive aquatic organism mortality. Its acute toxicity reported by Tomlin (1994) is 0.19 mg/l for Daphnia. Because this figure was very low, a literature survey was made and the low value was confirmed. In fact, Vighi et al. (1991) reported 0.22 mg/l while older data referred to 0.05 mg/l (Mayer and Ellersieck, 1986).
4. Conclusions Through the present investigation, an initial risk assessment of the impact of agricultural pesticides has been made. This study could represent a cost-effective method that may be used before
Fig. 3. Concentration trends of water for three repeated treatments of dichlorvos calculated by SoilFug model.
engaging in many expensive monitoring programs. The findings could be useful to sustainable development of agriculture and risk assessment for pesticide use in developing countries, where analytical facilities are lacking. Up to now, exact ratios of Predicted Environmental Distribution/No Observed Effect Level or Water Quality Objective have not been calculated. In our opinion, this ratio should be calculated only when the margin of uncertainty is reduced as low as possible. In the described procedure, several factors of uncertainty were present. The estimation of loads of pesticides, the timing of the application in the field, the water balance (input/ output), the variability of soils etc., are just a few examples of the environmental variable influence on the model. The environmental persistence, the correctness and precision of physico-chemical data, as well as the limited availability and the selection of the ecotoxicological data are examples of uncertainty regarding the molecular characteristics. It is to be stated however that even if precision were lacking, pesticides at highest risk have been certainly identified as well as trends and approximate concentrations, therefore risk management measures could be indicated. The situation with respect to the pesticides use in the Xiamen agricultural area is of major concern. The total load of pesticides on agricultural soil is 27 kg/ha on average. If the calculation is made on the overall catchment area, the load is still very high, 7.6 kg/ha. These data are very high even if compared with intensively exploited agricultural areas. The pesticide market is dominated by organophosphate insecticides, which are very toxic to aquatic fauna and very mobile (although short living). Fish and aquatic organism kills have been reported (GEF/UNDP/IMO, 1995), even if their causes have not been established. Some of these chemicals are volatile and therefore there is a potential risk to human health. A master plan to improve and change the actual agricultural practices should therefore be prepared. Major points could be the rotation of insecticide treatments (e.g. organophosphates alternated with pyrethroids), the selection of less
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impacting and less mobile products (e.g. other organophosphates, synthetic pyrethroids, pseudopyrethroids), and the introduction of crop rotation systems and integrated pest management practices. In conclusion, the present state of pesticide use in the Xiamen area is a very high risk for the aquatic environment and is in conflict with aquatic resources utilisation. For sustainable development of the area, relevant remedial measures should be quickly undertaken.
Acknowledgements The authors wish to thank the Food and Agriculture Organization of the United Nations (FAO), and the GEF/UNDP/IMO Regional Programme for the Prevention and Management of Marine Pollution in East Asian Seas and its Programme Manager Chua Thia-Eng for the support of this investigation and for the permission to use material from a project report compiled by the first author (GEF/UNDP/IMO MPP-EAS and FAO, 1998).
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