Ν EWS OF THE WEEK ARCHAEOLOGY
PROOF OF SALT Instrumental analysis gives evidence for salt production in ancient China
W
ITH THE HELP OF SOME
high-tech analytical instruments, an international team has found "unequivocal prooP of salt production by early societies that flourished in central China during the first millennium B.C. According to the researchers, the finding is China's oldest confirmed example ofpottery-based salt production and gives archaeologists new methods for evaluating other salt-producing sites (five Natl. Acad. Sci. USA 2005,102,12618). To chemists, salt is simply an ionic crystalline solid. But to anthropologists, salt is the hallmark of a complex society Because of salt's role as a dietary supplement and food preservative, anthro-
pologists argue that salt production enables increased trade, population growth, and regional expansion and is therefore critical to the development of a complex society Until now, the ancient Chinese civilization that developed in what today is ZhongXian County had perplexed anthropologists. Despite evidence of a complex society in this region, archeologists had been unable to find definitive evidence of salt production. At the archeological site known as Zhongba, a team led by Harvard University anthropologist Rowan Flad found the earthenware remains of a large-scale salt production facility Although the pottery was
similar to that of other ancient salt-producing sites, the researchers wanted to prove that the vessels had indeed been used to make salt and not some other material such as fish sauce. Using X-ray fluorescence and X-ray diffraction, they were able to link trace compounds from residue on the saltmaking tools to local brines that likely served as the salt's source, as well as to other ancient salt-production sites in China. The team also used scanning electron microscopy to identify traces of sodium chloride on the vessels' inner walls. "Archaeologists frequently struggle to find adequate methods for exploring this ephemeral product in ancient contexts," Flad writes. "This work shows that new approaches to archaeological remains may bear fruit in the search
SALT OF THE EARTHENWARE The remains of pottery-based salt production are concentrated on this small mound, an archaeological site in China along a tributary of the Yangzi River.
f o r salt."—BETHANY HALFORD
BIOGEOCHEMISTRY
ural abundance ofthe carbon iso tope in moss plants in a peat bog. Atmospheric C 0 2 was orig inally believed to be the main carbon source for peat mosses. But earlier work by the Netherlands team indicated that at mospheric c o 2 4 2 alone is not suffi ders and AshnaA. Raghoebarsing cient to account BACTERIUM LIVING ON and inside the cells of of Radboud University, in the for the growth of Sphagnum moss in peat Netherlands, and colleagues iden some peat mosses. bogs has been discovered to oxi- tified the bacterium as a relative Overall, the moss dize methane to carbon dioxide, of a Methylocetta species (feature uses the recycling mechanism to which the moss then uses as a car- 2005,436,1153). In lab studies, generate about 15% of its carbon bon source for photosynthesis. the researchers incubated moss intake. This efficient recycling is This symbiotic relationship helps plants with 13C-labeled methane important, because it reduces the to better explain the fate of CH 4 to show rapid in situ bacterial ox amount of methane—a potent produced by decaying plants in idation of 13CH4 to 13 C0 2 . greenhouse gas—that enters the wetland ecosystems, animportant Over several days, the moss atmosphere, Damsté notes. The part of Earth's carbon cycle that fixed the 1 3 C0 2 into carbohy team plans to study the pheaffects the concentration of green- drates, which was monitored by nomenon in other peat bogs. If house gases in the atmosphere. the recycling is a general phemeasuring the formation ofa 13CJaap S. Sinninghe Damsté of containing sitosterol. The team nomenon, it should have an imthe Royal Netherlands Institute confirmed the findings by com pact on the modeling of global for Sea Research, AlfbnsJ. Ρ Smol paring the lab results with the nat climate change.—STEVE RITTER
NEW WRINKLE IN CARBON CYCLING
Moss and bacteria team up to recycle CH into C 0 for photosynthesis
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WWW.CEN-0NLINE.ORG
HARD AT WORK Methanotrophic bacteria (fluorescently labeled yellow clusters) convert CH 4 toC0 2 for use by mosses in photosynthesis. (Chlorophyll is blue.)
C & E N / A U G U S T 2 9 , 2005
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