| The enhancement of human activities intensified the soil disturbance, which caused serious land issues. Chongming Ecological Island Project is the largest and the most difficult ecological construction system in the world at present. The project was based on the agriculture and aimed to realize the transformation from traditional to ecological agriculture and to achieve ecological industries finally. However, some agricultural soil in Chongming Island was polluted by heavy metals or pesticide and fertilizers, and underwent salinification, which would seriously impede the development of Chongming ecological agriculture and affect the marketing of vegetable crops.This paper was supported by the project of the Development and Application Demonstration of Health Diagnosis and Decision-making Support System of Agricultural Soils in Chongming Ecological Island, which was the sub-topic of the Development and Utilization of Decision-making Support System in the Digital Ecological Construction of Chongming Island, belonging to key scientific and technological projects in the eleventh five-year term of Shanghai. Agricultural soils in Chongming Island were selected as the research object and multi-disciplinary synthetic study methods were used in this study, including environmental geo-science, the geography, the environmental geochemistry, the environmental ecology, the geographic information system and so on. This paper was aimed to establish a scientific acute toxicity diagnosis system of soils based on data inquiry, onsite investigation, field sampling, laboratory analysis, land survey in the grid-based scale, and experiments in typical demonstration areas. Then soil quality assessment basing on minimal dataset (MDS) was used to verify the reliability and accuracy of the acute toxicity diagnosis system of soils. Main conclusions were as followings.(1) The rice soils in Chongming Island were lack of available phosphorus (AP), while vegetable soils had an AP concentrations varying in a large range. Available kalium (AK) and nitrate concentrations in Chongming soils exceeded the standard seriously. Vegetable soils were also polluted by Cr, Hg and As, which might originate from the transportation and fertilization activities. Hg content in watermelon soils was higher than rice soils and vegetable soils. In addition, agricultural soils in Chongming Island had been not polluted by organic pesticides, which were residuals of early accumulated pesticides in the soils or came from atmospheric long-distance migration, but most of them had already been degraded. Watermelon soils showed better biological quality, but rice soils were suffering more environmental stress. (2) Concentrations of soil solution extracted by nitric acid had better linear relationship with relative luminosity of freshwater luminescent bacteria. In addition, freshwater luminescent bacteria are sensitive to salinity, especially concentration of chlorine ion, and nitric acid is a better extraction agent for heavy metals. Therefore, nitric acid was selected as the optimal extractant. In order to deduct the extractant's influence on Vibrio Qinghaiensis sp.nov, relatively clean soil was acquired, the inhibiting rate of Vibrio Qinghaiensis sp.nov was 9.7%. This value could be utilized as soil background. Moreover,50% Effect Concentration (EC50) of reference poison phenol was 256 mg/L.(3) The average inhibiting rate of luminescent bacteria of Chongming agricultural soils was 25.3%, which belongs to. low-toxicity level. The inhibiting rates of luminescent bacteria of rice soils, vegetable soils and watermelon soils were 25.4%,26.4% and 24.4% respectively. Toxicity level of the soils in Chongbei subarea exceeded other four subareas because of relative high inhibiting rates of luminescent bacteria influenced by high sanility in the widely distributed coastal saline soil. Secondly is Chongnan subarea influenced by more intensive human activities. In rice soils, the inhibiting rates of luminescent bacteria of coastal saline soils were hither than those of gray alluvial soils and paddy soils, which were related to the high contents of soluble salt (EC), Cd and chlorine ion. Results of acute toxicity diagnosis of vegetable soils showed that the inhibiting rate of luminescent bacteria of asparagus soils was 47.02%, being the highest value. The order of other vegetable-soils according to the inhibiting rate of luminescent bacteria was as followings:cabbage soils-≈cucumber soils> eggplant soils≈bean soils≈tomato soils. High EC and nitrate concentration would increase the osmotic pressure in soil, which was the main reason for the strong inhibination of Vibrio Qinghaiensis sp.nov. in asparagus soils. Also, biological indicator (biomass carbon) showed a poor soil quality of asparagus soil. The inhibiting rate of luminescent bacteria of watermelon soil was 24.42%, with the relatively high values distributed in the Dongtan area. Hg content exerted an important impact on it.(4) Seven soil indicators were selected from 19 indicators using principal component analysis (PCA) and entered MDS, including pH, EC,nitrate, Cmic, Cd, Hg, DDTs. Then fuzzy comprehensive Index (FCI) was calculated using fuzzy comprehensive assessment method based on the 7 indicators. Comparing the results of soil quality assessment with acute toxicity diagnosis, FCI values and inhibiting rate of luminescent bacteria of coastal saline soils were both the highest in rice soils. Moreover, both the FCI values and inhibiting rate of luminescent bacteria of cucumber soils were relatively lower than the values of other vegetable soils, while both the values of asparagus soils were higher than those of other soils. Results of the counter-distance interpolation analysis using the software of ArcGIS showed that the majority of Chongming agricultural soils belonged to low-toxicity level and the soils in middle-toxicity level were mainly located in Dongtan area, Jianshe Town, Gangxi Town andXincun Town. Most of the FCI values ranged between 1.5～1.7. Soils with the FCI value being larger than 1.7 were distributed in Sanxing town, Xincun town, Gangxi town, Chengqiao town, Jianshe town, Shuxin town, Chenjia town and Dongtan area. Both of the methods concluded that Jianshe Town and Dongtan area were characterized with poor soil quality. Most soils in Dongtan area are at the immature stage and have a relatively strong biological toxicity, so that the soils are not suitable for planting vegetables.(5) FCI values were positively related with the inhibiting rate of luminescent bacteria of Chongming agricultural soils, which verified the reliability and practicality of acute toxicity diagnosis method of soils. However, limitations of the method also exist. For instance, bioassay toxicity diagnosis can detect the synthesis toxicity of soils, which is greatly affected by pH. Whileas soil quality assessment is a kind of systematic and scientific evaluation method with complicated processes and larger workload. Therefore, biological acute toxicity diagnosis is suitable for the fast and quantitative assessment of large-scale soils.(6) Values of pH, nitrate and soluble salt in the cabbage and rice soils in demonstration areas were suitable for plant growth, but there also existed some questions, such as excessive nitrate accumulation in the upper layer of soils, lack of phosphorus in soils and so on. The asparagus soils were acidified and became seriously with the planting ages. In-addition, all of the nitrate, AP and EC contents in greenhouse asparagus soils exceeded the values in cabbage soils and rice-wheat rotation soils in the demonstration zone, reflecting the questions of salinization, excessive and uneven fertilization in greenhouse soils. The soils in the demonstration zone were mainly polluted by As, Hg and Cd, while concentrations of Pb, Cr and DDTs had not exceed the standard.(7) The inhibiting rate of luminescent bacteria of cabbage soils in October was obviously higher than the values in other months, which was related to the tillage and fertilization. The inhibiting rate of luminescent bacteria of cabbage soils varied little in the profile, with a fluctuation in the depth of 15-25cm, which mainly affected by root distribution, soil hardness and pollutant concentrations. In October, the inhibiting rate of luminescent bacteria of soils in 07 asparagus greenhouse was the highest, secondly is the 04 asparagus greenhouse. The inhibiting rate of luminescent bacteria of soils in 98 and 04 asparagus greenhouses in November, January and February were higher than the values in 07 asparagus greenhouse and the inhibiting rate in 98 and 04 asparagus greenhouses reached the highest in November and January, which was depended on the activities of winter harvesting and fertilization. However, the inhibiting rate of luminescent bacteria of soils in 07 asparagus greenhouse reached the lowest in November because of short planting age, small asparagus plants and different farming systems. Generally speaking, the inhibiting rate of luminescent bacteria of the three asparagus soils decreased with depth, which suggested that the pollutants in surface layer were not transported or leaked to the deeper layer yet and asparagus roots might absorb some pollutants. Correlation analysis result indicated that the concentrations of nitrate, AP, EC, Cr, Cd and Cmic had a large contribution to the inhibiting rate of asparagus soils. The inhibiting rate of luminescent bacteria of rice soils in demonstration zone in November and February belonged to the low-toxicity level, while the inhibiting rate belonged to no-toxicity level in October and January.(8) The distribution factor of Hg (Lg (Kd)) in soil solution in demonstration areas was the lowest, indicating relatively strong migration ability. The order of the Lg (Kd) values of other heavy metals were as followings:Cd |
PDF Full Text Request