A section of fairway is irrigated with recycled water during the winter months at Desert Lakes Golf Course in Alamogordo, N.M. A recent study showed that heavy metals may not build up in turf areas irrigated by recycled water for years, though the study focused only on turfgrass areas in Denver-area parks. Photo by Darrell J. Pehr
When we think “heavy metal,” our thoughts may go to a Metallica concert we once attended, or maybe one this year we hope to attend, or we may think about the first time we heard Ozzy Osbourne sing “Crazy Train.”
No matter what comes to mind when we think heavy metal, these thoughts probably seem a bit distant. But a university researcher has done a study that involves heavy metals that may be as close as the fairway of a golf course.
Of course, these would be actual heavy metals, like zinc, lead and nickel, which can be a concern for turfgrass areas that have been irrigated by recycled water for years or even decades.
“The potential for heavy metal accumulation in soils receiving recycled water irrigation has been a concern in recent years,” says the study, titled “Soil heavy metal concentrations in public parks before and 11 years following conversion to recycled water irrigation.” The study’s author is Yaling Qian, Ph.D., in the Department of Horticulture and Landscape Architecture at Colorado State University, Fort Collins.
Qian notes that recycled water irrigation has many positive effects. It allows fresh water to be used for other needs and can reduce pollutant discharge to watersheds.
“In the meantime, there are concerns regarding pollutants (such as heavy metals, disinfection byproducts and pharmaceuticals) building up in soil,” the study says. “Long-term irrigation with wastewater leads to human health and environmental concerns, mainly related to the buildup of some specific pollutants.”
Qian and her co-authors also note that the assessment of soil concentrations of heavy metals after long-term recycled water irrigation, in a semi-arid climate, is not yet well documented.
“To determine if there is any heavy metal accumulation in soil after 11 years of recycled water irrigation, we tested the heavy metal concentrations of archived soil samples (0-7.87 and 7.87-15.75 inches/0-20 and 20-40 centimeters),” says the study, which was published in January in the International Turfgrass Society Research Journal.
Samples were collected at the start of recycled water irrigation and 11 years later, after recycled water irrigation had taken place for more than a decade. The samples were collected from turfgrass areas in five parks in Denver.
Qian and her team extracted heavy metals including arsenic, cobalt, cadmium, nickel, chromium, copper, lead and zinc from soil samples and measured them with a spectrophotometer.
They found that arsenic and cobalt concentrations in the soil decreased by 50%-83% and 66%-83%, respectively, after 11 years of recycled water irrigation. Levels of nickel decreased at three of the five parks, and cadmium, chromium, copper, lead and zinc did not show significant change.
They theorize that the increased soil pH under recycled water irrigation likely enhanced precipitation and adsorption of arsenic, cobalt and nickel, thus reducing their plant availability.
“Soil heavy metal accumulation was not an environmental concern on turfgrass areas in Denver parks irrigated with the recycled water used in this experiment,” the researchers concluded.
Of course, this is just one study measuring the impact of using recycled water in one geographic area. Other studies, some perhaps on golf courses, are sure to follow. But these results are encouraging.
So, now that we are not “going off the rails on a crazy train” worrying about heavy metals in the soil of our recycled water irrigated areas, maybe we can take a little time off and get to that Metallica concert after all.
Darrell J. Pehr is GCM’s science editor.