Soil Science Department, Universidade Federal de Lavras, Lavras, MG, 37200-000, Brazil.
Vale Institute of Technology, Belém, PA, 66055-090, Brazil.
Environ Sci Pollut Res Int. 2019 Jan;26(1):483-491. doi: 10.1007/s11356-018-3623-5. Epub 2018 Nov 7.
Mercury is a metal which is potentially toxic for the environment. Many factors control its retention in the soil, such as cation exchange capacity, pH, clay content, organic matter, and redox potential. It is important to know the phytotoxic effects of soil Hg to prevent environmental contamination and its entry into the food chain. Several analytical methods are used to measure metal phytoavailability in soils, but none has been reported for Hg in Oxisols, the most common soil class in Brazil and a very important soil class throughout the tropics. The aim of this study was to select the chemical extractor that best correlated the Hg levels in plants and the Oxisols. The soils used were classified as Dystrophic Red-Yellow Oxisol (LVAd) and Dystroferric Red Oxisol (LVdf), which were collected in the 0-0.2-m soil layer. The species selected for cultivation were a monocotyledon, oat (Avena sativa L. cv. São Carlos) and a eudicotyledon, common bean (Phaseolus vulgaris L. cv. Madrepérola). Each test plot was composed of a 500 cm pot filled with soil samples contaminated with HgCl. Treatments were arranged in a completely randomized design, with four replications. The experiment was conducted for 30 days. Mercury contents were separately extracted with the following extractors: USEPA 3051A, Mehlich-1, Mehlich-3, DTPA, and water. Mercury was determined by hydride generation atomic absorption spectroscopy. The extracted contents were correlated with the contents in the tissues of the plants' aerial part by the Pearson correlation. Although it is not considered a standard procedure to evaluate metal phytoavailable contents, the method that presented the best correlations between soil Hg and plant Hg was USEPA 3051A (r = 0.75*). As expected, the worst correlation was with water (r = 0.57* for common bean and r = 0,05 for oat).
汞是一种对环境具有潜在毒性的金属。许多因素控制着它在土壤中的保留，如阳离子交换容量、pH 值、粘土含量、有机质和氧化还原电位。了解土壤汞的植物毒性对于防止环境污染及其进入食物链非常重要。有几种分析方法用于测量土壤中金属的植物可利用性，但尚未有报道用于巴西最常见的土壤类型——氧化土中汞的情况，而氧化土在热带地区也是一种非常重要的土壤类型。本研究旨在选择与植物和氧化土中汞含量相关性最好的化学提取剂。所用土壤被分类为贫瘠红-黄氧化土（LVAd）和贫铁红氧化土（LVdf），这些土壤是在 0-0.2 米的土层中采集的。选择种植的物种为单子叶植物燕麦（Avena sativa L. cv. São Carlos）和双子叶植物普通菜豆（Phaseolus vulgaris L. cv. Madrepérola）。每个试验区由一个装满用 HgCl 污染的土壤样本的 500cm 盆组成。处理采用完全随机设计，设 4 个重复。实验进行了 30 天。采用 USEPA 3051A、Mehlich-1、Mehlich-3、DTPA 和水等提取剂分别提取汞。用氢化物发生原子吸收光谱法测定汞含量。用 Pearson 相关系数将提取的含量与植物地上部分组织中的含量进行关联。虽然 USEPA 3051A（r=0.75*）方法与植物汞的相关性最好，但它不被认为是评估金属植物可利用含量的标准方法。与水相比，这是意料之中的，因为水与土壤汞和植物汞的相关性最差（r=0.57*用于普通菜豆，r=0.05 用于燕麦）。
