Instituto de Geología Aplicada, Escuela de Ingeniería Minera e Industrial de Almadén (EIMIA), Universidad de Castilla-La Mancha, Plaza Manuel Meca, 1, 13400, Almadén, Ciudad Real, Spain.
Instituto de Geología Aplicada, Escuela Técnica Superior de Ingenieros Agrónomos de Ciudad Real, Universidad de Castilla-La Mancha, Ciudad Real, Ciudad Real, Spain.
Environ Geochem Health. 2020 Oct;42(10):3185-3198. doi: 10.1007/s10653-020-00557-8. Epub 2020 Apr 18.
Mercury (Hg) exchange at the plant leaf-atmosphere interface is an important issue when considering vegetation as a sink or source of this global pollutant. The aim of the study described here was to clarify this process by studying Hg exchange under laboratory conditions with a plant model, namely Epipremnum aureum. The desorption and absorption processes were studied under similar conditions in natural daylight. Hg exchange was measured at the foliar surface, and micrometeorological parameters and stomatal conductance were assessed. The results of the Hg exchange study showed different rhythms for the two processes, i.e. desorption (14-196 ng m day) was slower than absorption (170-1341 ng m day). The daily cycle was more complex in the desorption process, with a maximum when stomatal conductance was high but also with high values during nocturnal hours and a trend to absorption in the mornings. The daily absorption cycles were relatively simple, with values that coincided with positive stomatal conductance values and null values during nocturnal hours. The main factors involved in desorption were stomatal conductance and temperature, but other factors may need to be considered. The absorption process only involved total gaseous Hg, stomatal conductance and relative humidity. A net balance of the two experiments provided data on the amount of Hg transferred per unit leaf area (167 ng m for desorption and 9213 ng m for absorption), which implies total amounts of 23 ng of Hg desorbed and 1280 ng absorbed during the whole experiment. Finally, the reversible/non-reversible nature of the Hg exchange process must be reconsidered bearing in mind that Hg within the leaf can be emitted if changes in ambient conditions are appropriate to favour this process.
汞（Hg）在植物叶片-大气界面的交换是考虑植被作为这种全球性污染物的汇或源时的一个重要问题。本研究旨在通过使用植物模型（即绿萝）在实验室条件下研究 Hg 交换来阐明这一过程。在自然光下相似条件下研究了解吸和吸收过程。在叶表面测量 Hg 交换，并评估了微气象参数和气孔导度。Hg 交换研究的结果表明两个过程的节奏不同，即解吸（14-196ng m 天）比吸收（170-1341ng m 天）慢。解吸过程的日周期更为复杂，当气孔导度高时达到最大值，但在夜间也有高值，并且有向吸收转变的趋势。吸收过程的日循环相对简单，值与正值气孔导度值和夜间的零值相吻合。解吸的主要因素是气孔导度和温度，但可能需要考虑其他因素。吸收过程仅涉及总气态 Hg、气孔导度和相对湿度。两个实验的净平衡提供了单位叶面积转移的 Hg 量的数据（解吸 167ng m，吸收 9213ng m），这意味着在整个实验期间解吸了 23ng Hg 和吸收了 1280ng Hg。最后，必须重新考虑 Hg 交换过程的可逆/不可逆性质，因为如果环境条件的变化有利于这一过程，叶片内的 Hg 可能会被排放出来。
