Soil contamination is caused by the presence of man made chemical alterations in naked ground. This type of contamination typically results from the rupture of underground storage tanks, application of pesticides, percolation of contaminated surface water, oil and fuel dumping, leaching of wastes from landfills or direct discharge of industrial wastes to the soil. The most common chemicals involved are petroleum hydrocarbons, solvents, pesticides, lead and other heavy metals.
It is almost always directly correlated with the degree of industrialization and intensities of chemical usage. Large urbanized, heavily populated areas are also a source of contaminated biosolids or treated sewage sludge which contain not only human fecal matter but many of these same chemical contaminants washed through the system over the years. Philadelphia has a single sewer system which means everything from rainwater to toilet flushes to industrial residue all goes to the same place. Yuck.
Given Philadelphia’s rich industrial past it is an issue that takes on a particular importance for us, more so those, such as our own communities, who live in some of the most heavily post industrial sections of Philadelphia. The past has unfortunately left behind many chemical remnants, the very ingredients in fact, that went into the light to heavy industry-the heavy metals that forged the locomotives, petroleums that drove the freight lines, ships and base materials metal such as lead cadmium and zinc -that formed the nucleus of Philadelphia’s once thriving business past.
The concern over soil contamination stems primarily from health risks, from direct contact with the contaminated soil, vapors from the contaminants, and from secondary contamination of water supplies within and underlying the soil. Many local residents have been witness to the level of activity involved in the clean up of contaminated sites. Mapping of contaminated soil sites and the resulting cleanup are time consuming and expensive tasks, requiring extensive amounts of geology, hydrology, chemistry and computer modeling skills.
How does this relate to our common gardening experience. Does this mean it is unsafe to grow tomatoes in your side yard? Bring cut flowers into the house that came from Grandma’s in Port Richmond? By no means! First, let’s point out that there are resources for getting your soil tested regardless of where you live. Penn State Extension Offices (get to them while they still have funding!) is one place and almost every state offers a variety of testing some of which may make more sense for your situation. For example we tend toward the testing done at University of Massachusetts which always looks at lead levels given Greensgrow’s location. You might want to have a test run for salinity or organic matter if you feel confident in your soil’s safe but feel the garden is not delivering the punch it once did to your basil.
If you have issues with your soil, growing above ground in raised beds is always an option as is growing in an assortment of everything from old sneakers (talk about contaminated) to unused kiddie pools. Don’t try to take on remediation yourself unless you have a strong back, deep scientific and financial resources and a way of removing the soil that is there. Moving your problem to someone else’s yard is not the answer. Leave that to the professionals who have multiple technologies available to them-including phytoremediation -ironically the use of plants to pull the contaminants out of the soil, restructure them and release them into the air.
Cleanup or remediation is analyzed by environmental scientists who utilize field measurement of soil chemicals and also apply computer models for analyzing transport and fate of soil chemicals. There are several principal strategies for remediation: