BSLA Fieldbook BSLA 2014 Fall Fieldbook | Page 77

TOOLBOX / BSLA m Inorganic pollutants are naturally occurring elements on the periodic table such as metals, including lead and arsenic. Human activities such as the burning of fossil fuels, industrial production and extraction mining create releases of inorganic pollutants into the environment, causing toxicity. These are elements, so they cannot be degraded and destroyed; in some instances, they can be taken up and extracted by plants (ITRC, 2009). However, despite what you may have read on the internet about metals, phytotextraction of inorganic contaminants on sites is quite difficult and usually not worth attempting (Rock 2013). If extraction is possible, the plants must be cut down and harvested to remove the pollutant from a site (Chaney et al 2010). Instead of extraction and removal, plants and their associated microbes may be used to stabilize or change the state of an inorganic contaminant to reduce exposure risk and danger to humans and the environment. Interestingly, sunflowers used for lead remediation continue to appear on the internet and in landscape architecture publications as a phytoremediation solution, even though this practice essentially failed in field trials in the late 90s (Ulam, 2013). There is a lot of outdated science that we landscape architects must be careful not to misinterpret and apply. Instead we should team with knowledgeable phytotechnology scientists. ABOVE Potential contaminants can be anticipated by site program and landscape systems can be designed to intercept contamination events before they occur. For pollutants found in soils, plant-based treatment technologies have been best utilized for the treatment of organic contaminants and nitrogen (Dickinson et al 2009). Inorganic contaminant phytoremediation for removal of pollutants from a site (other than nitrogen) has been less successful. This generalization refers to soil-based contamination and does not apply to remediation of pollutants within water, since inorganics in water can often be filtered out by various types of soil and plant interactions and held within the soil matrix (Kadlec and Wallace, 2009). Integrating Phyto and Design Phytotechnologies could play a larger role in landscape design practice and in transforming brownfields into developable parcels providing a more sustainable choice for land planning. Twenty percent of all real estate transfers in the United States are brownfield sites, (Sattler et al, 2010) with the current value of these lands in 2010 in the range of two trillion US dollars. More than 16% of global land areas, equivalent to about 52 million hectares, are impacted by soil pollution worldwide (Anjum, 2014). The majority of traditional remediation techniques are expensive and energy intensive in their approach to quickly correct an environmental Boston Society of Landscape Architects Fieldbook 75