Muhammad Sanaullah

EDTA-Enhanced Phytoremediation of Heavy Metals: A Review

The increase in heavy metal terrestrial ecosystems’ contamination through anthropogenic activities is a widespread and serious global problem due to their various environmental and human implications. For these reasons, several techniques, including phytoremediation of heavy metals, have been extensively studied. In spite of significant recent advancement, ethylene diamine tetraacetic acid (EDTA)-enhanced heavy metal phytoextraction as well as related ecological risks are still topical and remain an important area of research. In fact, EDTA favors the solubilization of metals and metalloids in soils, and was therefore extensively studied during the last two decades in order to improve phytoextraction efficiency and reduce treatment duration. This review highlights the recent findings (2010–2012) and mechanisms behind EDTA-enhanced (1) solubilization of heavy metals in soil, (2) mobilization/transport of soluble metals towards plant root zone, and (3) metal absorption by plant roots and translocation towards aerial parts. The review also presents potential risks associated with EDTA-enhanced phytoextraction: (1) environmental persistence of EDTA and/or metal-EDTA complex; (2) potential toxicity of EDTA and/or metal-EDTA complex to plants; and (3) leaching and contamination of groundwater. Moreover, field-scale cost of EDTA-enhanced remediation and the role of EDTA in time required for heavy metal remediation is discussed.

Soil Carbon Sequestration in Dryland Agriculture

Drylands are the part of terrestrial ecosystem characterized by low water and spans over an area of about 6.15 billion hectares. About 57–65 % of this area is desertified or prone to desertification. In spite of low soil organic carbon (SOC), the total SOC stock in dryland soils is 241 Pg (1 Pg = petagram =1015 g) which is 15.5 % of the global SOC pool (1550 Pg). Significant C losses (~20–30 Pg) occur due to low C input as a result of desertification. About two third of this loss can be sequestered through better management practices in the period of next 50 years. In this chapter, our major focus is to discuss the biophysical aspects of soil C sequestration and their impact on global climate change and food security in dryland areas. Management and other land use practices for SOC sequestration to combat land degradation in drylands, such as afforestation using suitable species, management of pasture on grazing lands, management of cultivated lands, and restorative land use to reestablish the degraded soils and the ecosystems. In drylands, tree species suited for afforestation are Acacia, Mesquite and Neem etc. Grazing management practices such as controlled grazing at an optimal carrying capacity, fire management, and the cultivation of improved species. Suitable practices for soil management are application of biosolids (manure, sludge) to improve the macrofauna (termites) of the soil, water harvesting, use of vegetative mulches, and wise irrigation structures.