摘要
一般情况下，土壤中银含量水平极低，全球平均值仅为0.05mg·kg~(-1)。从已有的资料，中国土壤中银的平均水平远高于全球平均值，达0.35mg·kg~(-1)；而中国南方紫色土壤含银水平在0.134～0.193mg·kg~(-1)。
多数研究者认为银并不是动植物生长必须元素。反之，高水平的银对鱼类、水生植物、野生植物和动物体具有极强的毒性和潜在影响。但研究认为，适量银不但对植物生长有益，也有益于人体健康(特别是胶态银)。人们大量使用银首饰以及用银器作为餐具也证明了这一点。
在现代工农业条件下，由于银及含银化合物的广泛使用，大量的银进入环境和土壤，银在土壤中富集明显。国外报道，由于工业和农业行为，土壤中银含量超过背景值3～50倍。但目前，无论是银在土壤及环境中的形态、迁移、沉淀、转化，以及银在动植物体内的生物学行为均研究不多，这也导致对银的行为认识不足，因此，加强银的环境和生物学行为的研究，将具有重要的意义。
银的常规测定方法以重量法、容量法、分光光度法等为主，这些方法的灵敏度均达不到土壤和植物中痕量银的测定要求。随着原子光谱分析方法的出现，其极高的灵敏度和检出限使痕量银的测定成为可能，目前，无论是原子吸收光谱或原子发射光谱(如ICP)，虽然灵敏度均能达到土壤或植物样品含量水平，但由于土壤和植物样品复杂程度极高，不同前处理条件下，各种干扰物质的存在导致测定可靠程度受到影响，因此，选择恰当的前处理方法，配合高灵敏度的原子光谱分析，对土壤、环境和植物中银的研究极其必要。
本文在对几种前处理方法对比的基础上，比较了火焰原子吸收和无火焰原子吸收法对土壤和植株样品中银测定的条件和可靠性；并以硝酸银为外源银，通过淹水培养实验及盆栽实验，研究银在土壤中的存在形态和含量分布；同时探讨了外源银在水稻体中分布规律及水稻对银的富集能力，分析了淹水培养时间和种植水稻行为对银形态转化的影响，以及银存在对水稻吸收氮、磷、钾、钠、钙、镁、铜、锌、铁、锰、铬的影响，旨在能为土壤和植物体中痕量银的研究提供可行测定方法，为了解银在土壤中分散和富集过程与机制，了解土壤中银元素对植物的有效性，为银在环境中的归宿的预测以及寻求控制银污染的决策等提供科学依据。主要实验结果如下：
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 3~50 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 AgNO_3 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
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