What are the most hazardous heavy metals found in plants? or another way, what are those heavy metals that can be easily removed by plants? Do heavy metals affect the soil chemistry and physiology of plants that are grown in metal-contaminated soil?
Please also mention the simplest, cheapest, and acceptable protocol of quantification of those heavy metals from soils and plants.
With regards.
Hi you can take a look at this RG link
https://www.researchgate.net/post/Which_plants_I_can_choose_when_cleaning_the_soil_in_heavy_metals
I have researched the phytoextraction of the heavy metals (lead and cadmium ) by the halophyte plant species. After years of research, I know that many saline plant species have the ability to refine heavy metals, but I must mention a few important points: 1. phytoremediation (phytoextraction) of heavy metals by plants is highly dependent on soil acidity. If the soil acidity is more than 7.5 or 8, due to the stabilization (fixation) of heavy metal in the soil, the heavy metal plant can not move the in the aqueous phase of the soil and metal availability is reduced. 2. hyperaccumulators can tolerate only moderate concentrations of heavy metal toxicity in the aqueous phase of the soil . As the concentration of heavy metal increases, the amount of dry or wet matter of the plant decreases sharply, so the multiplication of these two factor, decreases sharply.
3- In plant physiology, the crown part of the plant (where the root system ends and the shoot system begins) is an area that prevents the movement of heavy metal to the shoot of the plant (the main purpose of phytoextraction is to absorb heavy metal to the shoot to be able to remove aerial mass in this method to later destroy it or concentrate its heavy metal). Therefore, our research showed that the amount of heavy metal accumulation in the roots of halophyte plants is tens of times higher than the shoot of that plant.
The heavy metal content of the soil is relatively secondary data except for determining the overall danger (maximum concentration that can be mobilized). The important thing is to determine the bioavailable fraction, i.e. the part accessible to the plant or to the mobilization towards water resources. Bioavailability is the ability of a trace element to be transferred to the plant.
Plants, like invertebrates, react differently depending on the variety. Some are little or not tolerant and die in contact with heavy metals. Others have defence reactions and slow down absorption by secreting acids which will increase the pH and consequently reduce the mobility of trace elements. Others, finally, are tolerant to metals, and even accumulate them, and concentrate them. These plants are called “hyperaccumulators” and metallophiles.
Trace elements are taken up by the roots, and most often remain there. The passage in the aerial parts (stems, leaves) varies according to the metals and are the signs of an increase in the concentration of metals in the soil, the lead remains in the roots. Cadmium passes more easily into the aerial parts.
Plants can have a stabilizing or even curative role. Without neglecting the aesthetic advantage, the plants above all avoid dust flying and can be used to vegetate polluted sites, provided that the pollution is not excessive, and concerns certain metals (zinc, cadmium for example. We do not know of any plant accumulating lead or mercury...). This type of action is called “phytoremediation”.
On the other hand, scientists manage to develop the cultivation of certain plants in soils loaded with heavy metals in order to depollute them. We can even reuse their leaves to extract useful molecules in chemistry. These include two plants with the incredible ability to not only grow but extract metals from the soil to store them in their leaves. One, the wood stork (Noccaea caerulescens) concentrates zinc and cadmium; the other, the anthyllid vulneraria, does the same by adding lead to its menu. In addition, being from the legume family, it captures nitrogen from the air to transform it into ammonium in its roots, which thus enrich the soil, through a hitherto unknown bacterium.
These amazing plants are even capable of concentrating metals whose rarity is beginning to worry the industry, such as palladium, zinc, or rare-earth. Of course, there is no question of letting this vegetation rot on the spot and releasing into the ground the metals that it has contrived to extract.
What happens to metals in the soil? Their fate depends on the metal and soil studied. A part is volatilized (mercury). Part leaves with runoff. Part goes into the ground. Soil is a complex whole, made up of several fractions or “phases”. The solid phase represents only half of the volume, the rest being made up of water and gas.
Regards
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