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Jia Z.,Southwest University | Jia Z.,Southeast Sichuan Geological Group | Wei H.,Southwest University | Sun X.,Southwest University | And 3 more authors.
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2011

Cadmium (Cd) is the most popular heavy metal element in the contaminated soil of Three Gorges Reservoir Region. Cadmium has significant negative effects on the health of soil-plant system in the research area due to its high concentration and biological activity. Thus, it is essential to study the tolerance and accumulative ability of plant species in cadmium contaminated soils in order to protect the ecological environment and plan the reasonable land use. Salix variegate and Pterocarya stenoptera are two native riparian plants which can be used widely in the vegetation restoration of the hydrofluctuation zone in Three Gorges Reservoir Region. In order to reveal the response of these two species to cadmium, five different kinds of cadmium treatment were applied to determine the growth, biomass and cadmium concentration in various parts of S. variegate and P. stenoptera seedlings. The cadmium treatments were 0(control), 10, 20, 50, and 100 mg/kg. The results showed that: (1) The root biomass, aerial biomass, changes of stem length and stem diameter of S. variegate and P. stenoptera seedlings decreased with Cd content raised. Tolerance index (Ti) based on the dry biomass and growth parameters of two species showed no significant difference in 10 mg/kg in contrast with a significant decrease in 20, 50, and 100 mg/kg (P < 0. 05), when compared to the control respectively. (2) The cadmium concentration reached up to 61.73, 163. 04, and 91. 05 mg/kg in stems, leaves, and roots of S. variegate in turn when treated with cadmium less than 20 mg/kg. However, in the same treated condition, the highest cadmium concentration was 7. 9,5. 25, and 190. 68 mg/kg in stems, leaves, and roots of P. stenoptera, respectively. (3) Cd accumulation in S. variegate was highest in leaves and lowest in stems except in the control, with the translocation factor (Tf) between 0. 789-1. 513. Very differently, Cd accumulation in P. stenoptera was highest in roots and lowest in stems also except in the control, with the translocation factor (Tf) between 0. 037- 0. 044. Thus, the translocation factor (Tf) o f P. stenoptera was far less than that of S. variegate. These characteristics indicated strategies of cadmium uptake and translocation by two plant species growing in Cdcontaminated soil were not totally different: Cd tended to be immobilised and held primarily in the roots of P. stenoptera, whereas it was more easily translocated to the aerial tissues of S. variegate. The tolerance of species to cadmium was demonstrated by these two strategies so that the plants were able to survive and had a high productivity. (4) The results indicated that S. variegate and P. stenoptera seedlings had a high capacity of growth adaptation and tolerance under 10 mg/ kg Cd stress, and also, the capacities of translocation and cadmium accumulation in aerial parts of S. variegate seedlings were higher than that of P. stenoptera seedlings, which verified that the differences in accumulation of cadmiumwere not correlated with tolerance ability of plants. Such a behavior in the seedlings of two species was further confirmed by the calculation of the bio-concentration factor (BCF). The study suggested that S. variegate had considerable potential application to those cadmium contaminated areas in the hydro-fluctuation zone of the Three Gorges Reservoir Region.

Yan M.-S.,Southeast Sichuan Geological Group | Yan M.-S.,Chengdu University of Technology | Li W.-B.,Southeast Sichuan Geological Group | Yang L.-C.,Southeast Sichuan Geological Group | And 2 more authors.
Research of Environmental Sciences | Year: 2014

Speciation characteristics, influencing factors and effectiveness of As, Cd, Cr and Pb in four main types of soils (purplish soil, limestone soil, yellow soil and paddy soil) were investigated through analyzing total contents and fractions of heavy metals in soils in Yubei District, Chongqing. The results showed that fractions of heavy metals significantly varied among different types of soils. Cr and Pb were the main components of the residual in all kinds of soils. Cd was mainly ion-exchangeable and residual speciated in yellow soils and purplish soils, which counted for 37.44% and 29.97% of the total Cd contents, respectively. The contents of available speciation of heavy metals in soils was as follows: w (available As) and w (available Cr) were 0.04 and 0.96 mg/kg in purplish soil respectively, w (available Cd) 0.13 and 0.09 mg/kg in paddy and purplish soil respectively, w (available Pb) was 1.94 mg/kg in yellow soil, which perhaps indicated a strong bio-effectiveness, when the bio-effectiveness of heavy metals in limestone-soil was lower. Available As and Cd significantly positively were correlated with total contents in main factors influencing on the chemical speciation and transformation process of heavy metals. However, there were significant negative correlations between available contents of Cd and Pb with pH, and between available Cr with soil organic matters. Available Cd, Cr, and Pb have a multivariate nonlinear logarithmic regressive relationship with total contents, pH and SOM in purplish soil. In conclusion, the equation can be used to effectively predict available contents of the heavy metals in the study area.

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