AUGUST 2016 RESEARCH SUMMARY

AUGUST 2016 RESEARCH SUMMARY

Chaney’s Cadmium Rufus Chaney was scheduled to retire at the end of July. We can all give thanks that, due to USDA bureaucracy and some unfinished report,s his retirement has now been postponed to March 2017, at the earliest. This library and the Research Story about Rufus were planned before the reprieve was granted. But why wait? The information is as valuable now as it would be in March. It also doesn’t hurt to give Dr. Chaney some kudos well in advance of his retirement. They are certainly well deserved!

Rufus is known and appreciated for his research on metal availability in biosolids and compost-amended soils, as well as in contaminated systems. He is also recognized as a true believer in the value of good science. He has consistently been willing to go to bat for a cause if he has the science behind him. He is also known for his mastery of the literature and his ability to recall just about every paper that has ever been published on topics related to his work. That includes author, journal, year and potentially volume number.

One of the central areas of his work has been on cadmium in soil/plant systems. That work is also the focus of this library. Cadmium is the metal that was of greatest concern in biosolids because it is the one metal that had been shown to cause both disease and fatalities for people who ate foods high in Cd as a result of being grown on Cd-enriched soils. The most famous of these is the case of the subsistence rice farmers in Japan after WWII. Smelter contamination resulted in elevated paddy soil Cd. The farmers were poor and ate nutrient-deficient diets, high in Cd from the polished rice grown in the paddies. Multiple cases of fragile bones as well as kidney and liver damage resulted from this high Cd diet. While there are instances of naturally occurring high Cd soils (just ask Rufus about soils in the Salinas valley), municipal biosolids was a concern because of elevated Cd prior to the implementation of the pre-treatment regulations.

The library is done in chronological order with papers on basic research and risk assessment. We start the library with a book chapter that Chaney co-authored in 1977. This chapter shows how long Rufus has been working on this topic and it also shows how far we have come. If you look at the metal concentrations in the sludges he sampled, you will shudder at some of those numbers. The only place you will find material with comparable metal concentrations these days is in an archive at a utility or a scientist’s lab. Many of the central themes of Rufus’ research are here in this paper: the importance of pH in controlling metal availability, the absence of phytotoxicity despite high metal sludges, the importance of the Cd:Zn ratio, the need for long-term research, and different uptake patterns by different crops. For biosolids history buffs, the chapter is also sprinkled with anecdotal information on how farmers got sludge long before permitting and testing were required.

From here we go to a long paper/book about the risk assessment process. This was required reading for me as a graduate student. It goes into detail on the way that Cd in soils (and also lead (Pb) and arsenic (As)) has the potential to cause harm. One of the critical factors of the biosolids rule was the consideration of bioavailability. Just because something is present in soil or food doesn’t mean it can or will hurt you. The pathways, the different roads to harm, are outlined and evaluated here. In fact, the 4th paper (remember, chronological order) is also about factors that may increase risks posed by elevated soil Cd. Rufus has always argued that the Cd problems in Japan were largely the result of poor diets. In the absence of sufficient nutrients such as Zn, Ca, Mg, and Fe, the body will absorb excess Cd.

The 4th paper demonstrates the role of dietary deficiency by summarizing the results of a range of animal feeding trials. Rats were fed differing amounts of Cd with and without the other nutrients. Results confirmed Rufus’ contention that, with sufficient nutrients, ingested Cd is only poorly absorbed. If you ever have the chance, just ask him about the New Zealand oyster eaters. Same deal as in this paper, but with people who ate a lot of oysters (oysters can have elevated Cd).

The other two papers in the library are research papers from long-term biosolids amended soils. The first one was part of my PhD work. We went back to plots that Rufus had established in the 1970s and grew lettuce. The field included biosolids from Chicago, back in the day when biosolids were high in Cd. You would only be able to find those materials now in the archives. There were also equivalent plots set up where the same amount of Cd was added as a metal salt, with no biosolids matrix. There were also plots included that had what we would now consider “nothing special” biosolids, also a little on the high side. We grew lettuce because it is one of the plants that takes up a lot of metals. We also used the same type of lettuce that had been grown on those plots when they were first established.

Results here are similar to what others have found: The metals in the biosolidsamended soils remain lower than in equivalent salt-treated plots for the long term. And, in fact, the Cd in the low metal biosolids soils was the same as in the control plots.

The final paper in the library also looked at Cd uptake. Here isotopes were used to add Cd to the soils, allowing for the measurement of the specific Cd added rather than the bulk Cd. Similar results occurred here. The plant uptake slope from the biosolids-amended soils was linear and lower than the same soils, same Cd, but without the biosolids. This work, showing that the biosolids can reduce metal availability, has been critical to understanding that we can use biosolids to heal metal-contaminated soils. It is just one of the areas where Rufus’ insights have helped bring us to a clearer understanding and more informed policies.

Sally Brown, University of Washington