Phyto-remediation: Abrupt climate change and current water crises in agri-industry, has emerged a dreadful threat to Pakistan. Continuous squeezing and mismanagement of fresh water resources have urged the farmers of peri-urban to irrigate food crops/vegetable with raw sewage and industrial effluents. Despite the fact that these effluents are meet the farmer’s requirement but these are over loaded with variety of pollutants.
Due to intensified industrial process these effluents contain soluble heavy metals as major inorganic constituents which are easily stored in edible parts of plants. Generally, heavy metals are those elements which highly dense and toxic to living organisms.These heavy metals being dumped into soil are not only threat to crop productivity but also human health. Major publically concerned heavy metals are cadmium, lead,chromium, mercury and nickel.Presence of these metals in body leads to kidney, neurological, cardiovascular, bone diseases. Chronic exposure (e.g. through ingesting contaminated food) leads to cancer development in body. Current economic standing of Pakistan, can’t afford expensive remediation technologies for such vast contaminated sites. Therefore, Pakistan needs a future sustainable, effective, environment friend and cheaper technology to address this public issue. “Phytoremediation” seems an apt way to produce sustainable and safe food for public. Compared to other technologies, it is the cheapest and efficient but little slower.
Phyto-remediation is a technique which is used to restore contaminated soils by growing plants or using their metabolites that stabilize, extract, volatilize, or inactivate soil pollutants. Basically, Phyto-extraction strategy evolves metal removal from the soil through plant uptake and accumulates in above-ground aerial plant parts that easily can be later harvest. Plants used on polluted soils must be capable of tolerating and accumulating high levels of metals (more than 0.01% of shoot dry weight) in harvestable parts. In addition, an ideal hyper-accumulator should have tendency to grow rapidly and produce high biomass on metal contaminated sites. An ideal hyper-accumulator plant has following characteristics (1). It should not be a source of food for humans or herbivores (containing herbivore deterrent substances). (2). It should have capacity to uptake and tolerate high levels of metal in harvestable parts. (3). It should have ability to uptake metal from soil, and then translocate to aerial parts. (4). It should have potential to grow rapidly and produce high biomass. (5). Root density and rooting depth should be appropriate. Luckily, the native flora of Pakistan has numerous hyper-accumulating plants in list. Some of well-known hyper-accumulator plant species includes rapeseed, mako (Black nightshade), Ragweed, Indian mustard, Muskgrass and Chinese brake fern. Additionally, trees are also used as hyperaccumulater due to their high biomass, extensive root system, and high water uptake and storage ability in the form of timber e.g. willow, poplar and birch species.
The dire need is to demonstrate farmers to use this technology. Farmers can use hyper-accumulator plants in crop rotation and as inter-crop or can plant trees. The harvested biomass of hyper-accumulator can be use to produce cost-effective energy e.g. oil, electricity etc. Government should step forward to collect such kind of biomass for its utilization on commercial scale. In future, plant biologists must focus on identification of native hyper-accumulator or acclimatization of foreign plant species.
The authors are from 1Institue of Soil and Environmental Sciences, University of Agriculture Faisalabad.