Ecological Toxic Effects Of Typical Pollutants On Soil

Soil bears all things on earth. The maintain of the balance of the soil ecological system and its function plays a key role to the sustainable development of agriculture. The ecological risk assessment of pollutant soil concerns a lot to sustainable development of agricultural, as well as ecological and environment. As we gain deeper recognition on the issue of the quality of soil, ecological risk assessment of pollutant soil becomes a more and more urgent requirement.Folsomia candida is often used as receptor of Ecotoxicological tests in soil ecological risk assessment and soil ecological benchmark development. Ecotoxicity testing using soil organisms might be useful tools to determine toxicity threshold if they refer to ecologically relevant parameters like mortality, growth or reproduction. On the other side, using indigenous species, rather than the non-indigenous species, for ecotoxicological assessments will greatly increases the ecological relevance and reliability of bioindicator testing. Previous studies revealed that Onychiurus yodai (Yosii,1966), rather than the species mentioned above, is one of the most numerous and widely distributed species of Collembola in Chinese arable lands.The sublethal toxicity of cadmium, PCBs and B[a]P for the Collembola F.candia was studied by determining the effects of respectively increasing concentrations of cadmium, PCBs and B[a]P on growth of adult and juvenile, survival and reproduction in udic-ferrosols(UF) and aquic-cambosols(AC) to compare the different impact made by type and accumulate datas for developing soil ecological benchmarks. In addition, series studys were developped to screen the preference of O.yodai and explore the life-history of O. yodai, including changes of portrait features (sizes and weight), reproduction strategies, fecundity and the egg hatch process. Thus, the culture condition and procedure to develop the ecotoxicity test of chemical substances for the Collembola O.yodai were built.The UF and AC soils were spiked with CdCl22.5H2O(0.3、0.5、1、2、4、8、 12、25、50、100 and 200mg Cd/kg dry weight soils(d.w.s.)).The duration of exposure was 28 days. The reproduction rate, adult length, survival rate and juvenile length were all well fitted the dose-response relationship in UF and AC. The EC50 of survival rate, reproduction rate, adult length and juvenile length were 197.53,100.74, 108.53 and 195.99 mg kg-1 in UF and 37.45,7.18,35.05 and 31.14 mg kg-1 in AC, respectively. Besides juvenile length, The three indices followed an order of reproduction rate> adult length> survival rate in sensitivity both in UF and in AC. Difference in ecotoxicity of Cd to F. candida existed between the two soils since the value of NOEC> LOEC and EC50 in UF is lower than those in AC, which is likely attributed to the difference in soil physico-chemical property.The UF and AC soils were spiked with CdCl22.5H2O(0.0、25、0.5、1、5、10 and 50 mg PCBs/kg (d.w.s.)).The duration of exposure was 28 days. Results showed that survival rate was the least sensitive indexes to PCBs, because it just existed significance in UF with the EC50 of 39.39 mg kg-1. The reproduction rate, adult length and juvenile length were all well fitted the dose-response relationship in UF and AC. The EC50 of reproduction rate, adult length and juvenile length were 147.06,76.60 and 9.94 mg kg-1 in UF and 13.77,64.10 and 11.35 mg kg-1 in AC, respectively.The UF and AC soils were spiked with CdCl22.5H2O(0.0、1、1、10、100 �'� 1000 mg B[a]P/kg (dw.s.)).The duration of exposure was 28 days. Results show that the index of growth rate of their larva was the most sensitive and even responsive to a low concentration of B[a]P. It is, therefore, suggested that the index be cited as an indicator of the soil B[a]P toxicity. The four indices followed an order of juvenile length> adult length> reproduction rate> survival rate in sensitivity. Significant difference in ecotoxicity of B[a]P to F. candida existed between the two soils with LOEC value being 1 mgkg-1 in udic-ferrosols and 100 mgkg-1 in aquic-cambosols, which is likely attributed to the difference in soil physico-chemical property, especially content of organic matter and pH.According to the observation and recording, the favorite food of O.yodai was baker’s yeast. For the ecotoxicity test using O.yodai,10 males and 5 females,21-24 days old should be used per test-vessel. On day 35 collembolans are extracted from the soil and counted. For F. fimetaria the gender are discriminated by size in the synchronised animal batch used for the test. Females are distinctively larger than the males.