Preliminary Research On Source Tracing, Risk Assessment, And Phytoremediation Of Heavy Metal In Xiangxi River Zone, Three Gorges Reservoir Area

Since impoundment of the Three Gorges Reservoir, the Ecological Environment of thebank area is fragile, and the state started the construction of ecological barrier in the ThreeGorges Reservoir Area. This study researched on the heavy metals in Xiangxi River areafocusing on the source, migration, biotransformation, biological indicator and environmentalhealth risk assessment from heavy metal. The purpose is to provide reference for theprevention and control of heavy metal pollution in the process of ecological barrierconstruction in Xiangxi Bay, Three Gorges reservoir area. The following were found:1. Transfer Characteristic and Source Identification of Soil Heavy Metals from Xiangxi Riverzone, Three-Gorge ReservoirAreaTransfer characteristics of heavy metals and their evaluation of potential risk were studiedbased on determining concentration of heavy metal in soils from water-level-fluctuating zone(altitude:145-175m) and bank (altitude:175-185m) along Xiangxi River, Three GorgesReservoir area. Factor analysis-multiple linear regression (FA-MLR) was employed for heavymetal source identification and source apportionment. Results demonstrate that, duringexposing season, the concentrations of soil heavy metals in water-level-fluctuation zone andbank showed variation, and the concentration of soil heavy metals reduced in shallow soil, butincreased in deep soil at water-level-fluctuation zone. However, the concentration of soilheavy metals reduced in both shallow and deep soil at bank during the same period.According to the geoaccumulation index, the pollution extent of the heavy metals followedthe order: Cd>Pb>Cu>Cr, Cd is the primary pollutant. FA and FA-MLR reveal that in soilsfrom water-level-fluctuation zone,75.60%of Pb originates from traffic,62.03%of Cd fromagriculture,64.71%of Cu from natural rock and75.36%of Cr from natural rock too. In soilsfrom bank,82.26%of Pb originates from traffic,68.63%of Cd from agriculture,65.72%of Cu from natural rock and69.33%of Cr from natural rock. In conclusion, FA-MLR cansuccessfully identify source of heavy metal and compute source apportionment of heavymetals, meanwhile the transfer characteristic is revealed. All these information can be areference for heavy metal pollution control.2. Accumulation Characteristics of Cd in Bermudagrass on Water-Level-Fluctuating Zonealong Xiangxi RiverThis research is about accumulation characteristics of Cd in bermudagrass, which is theDominant species on Water-Level-Fluctuating Zone along Xiangxi River. This is shown thatthe range of Cd content in bermudagrass is from0.066to0.130mg/kg, within the limit ofChinese national standard of feed hygiene (0.5mg/kg). Positive correlation was foundbetween total P concentration or M3-P in soil and Cd content in bermudagrass. However, nocorrelation was found between total Cd concentration or M3-Cd in soil and Cd content inbermudagrass. A model containing soil characteristics (Organic matter, Cosmid, P, S, K, Fe,Al, Mn, B, Ca, Cu, Cd, Zn and pH) can predict the Cd content in bermudagrass.3. Metal Distribution in the Tissues of Two Benthic Fish from Stream along the Xingxi RiverMetal content was determined in two fish species (Misgurnus anguillicaudatus andMonopterus albus) inhabiting rice Stream along the Xingxi River. Both are important foodfish in East Asia. The levels of eight metals (Fe, Mn, Zn, Cu, Cr, As, Cd and Pb) in skin,muscle and intestinal tissues were measured and correlated with fish size. Metal distributionamong the tissues was examined and the potential risk of fish consumption was evaluated.Correlations between metal concentration and fish size were not significant. Concentrations ofessential metals varied significantly among tissues, but the differences were not significant fornon-essential metals. Correlations among metals in skin tissue were stronger than in intestinaland muscle tissues. Metal concentrations in the edible tissues of both fish met permissiblelevels for consumption, except Pb in loach skin. Potential risk caused by Pb from loach skinconsumption should be concerned.4. Influence of Traffic-Related Elements on the Lichens and Health Risk Assessments forGolden Monkey Consuming LichensTwo lichen species were used as ecological indicators to assess the deposition oftraffic-related metals and their influence on Sichuan snub-nosed monkeys (Rhinopithecusroxellana) in Shennongjia National Nature Reserve. The lichen samples were collected fromthree localities with different traffic intensity in the core area of the Nature Reserve, and onesite being from the relatively non-polluted area. The results showed that lichens from thetraffic sites have significantly higher concentrations of Fe, Cd, Pb Zn, and Cr compared tothose collected from the control site. Factor analysis pinpointed lichen accurately record the main source of pollution--vehicular traffic. Chlorophyll fluorescence (Fv/Fm) of lichen U.lexhibited stress symptoms from the traffic sites decreased the Fv/Fm indicating lessphotosynthetic efficiency. Modified THQ (target hazard quotients) was used to evaluate thepotential health risk posed by lichen consumption via heavy metals, showing the trafficactivity in Shennongjia National Nature Reserve may influence golden monkey health.5. Remediation of Cadmium Contaminated Soil Uing Alternanthera philoxeroidesA. philoxeroides was choose as study object, and was put in Small-scale heterogeneity insoi to survey whether clonal plants are physiologically integrated if connections amongramets allow transport of resources or ramets in favourable habitats may provide support todeveloping or stressed ramets. The following was found. Integration decreaced the objectiveeffects of Contaminated Soil on the offspring ramets. Clonal integration characteristics isbeneficial to withstand heavy metal stress in A. philoxeroides. Connected offspring rametssignificantly increased their biomass, Cd concentration in tissues and total amount of Cdaccumulation in biomass when it was supported by the favourable soil with increasing Pcontent. However the transfer coefficient of Cd in A. philoxeroides reduced with the P contentincreasing. Therefore the clonal integration being assisted with special way of P supplying ispotential to Cd accumulation.Preliminary study on pollution survey, pollution risk assessment and remediationtechnology for heavy metal in Xiangxi River region can provide reference for the preventionand control of heavy metal in this area and the construction of ecological barrier.