Study On Form Transformation Of Exogenetic Silver In Soil And Distribution Rule Of Silver In Rice

Commonly, the content of silver in soil is extremely low, and the mean content of the whole world is only 0.05 mg·kg^-1. As far as information goes now, the mean content of silver in soil in China reaches 0.35 mg·kg^-1, much higher than that of the whole world,and is 0.134-0.193 mg·kg^-1 in purple soil of southern areas.Most researchers consider that silver is not necessary element for plants and animals. Conversely, silver has exceeding toxicity and potential affections on fish, aquatic plants, wild plants and animals if the content of silver is high. However, many studies find that right amount silver is helpful to plant growth and human's health (especially colloidal silver). The wide use of jewelry and that silverware used as dishware have proved this.Under modern industrial and agricultural condition, due to the wide use of silver and its compounds, plenty of silver entered environment and soil and enriched obviously in soil. It is reported that silver in soil has exceeded as 3⁵0 times as background value owing to industrial and agricultural activities^[10,11]. But now, there are few studies on neither the speciation, transference, deposition nor transformation of silver in soil nor the biological behavior of silver in animal's and plant's body, and this cause lack of understanding of silver behavior. So it is essential to enhance the study on environmental and biological behaviors.The traditional mensuration of silver mainly are gravimetric method, titrimetry and spectrophotometry. But the sensitivity of these methods can't match demand of the determination of silver in soil and plant. Along with the occurrence of atomic spectrometery , its high sensitivity and detect limit make the determination for trace silver feasible. Now, different pretreatments and the existence of many interferences have affect on determination because of high complexity of soil and plant samples, though the sensitivity of atomic absorption spectrum or atomic emission spectrum can reach the demand for determination of silver in soil and plant. So it is extremely necessary to choose right pretreatment combined with atomic spectrum analysis with high sensitivity for study silver in soil, environment and plant.On the basis of comparison on several pretreatments, this paper compared the condition and feasibility of the flame atomic absorption spectrometry and flameless atomic absorption spectrometry on determination of silver in soil and plant, and used AgNO₃ as exogenetic silver by adopting inundation incubation experiment and pot culture experiment. The speciation and distribution of exogenetic silver in soil were studied, and the distribution of exogenetic silver in rice as well as the enrichment capability of rice on silver were discussed at the same time. Inundation incubation time and the effects of rice planting on transformation of silver speciation and the influences of silver existence on absorption of N, P, K, Ca, Mg, Zn, Fe, Mn and Cr by rice were all...