In agricultural-intensive areas of the U.S., however, the density of NO emissions emanating from fertilized soils may even rival NO emission densities found in urban areas. There is concern that enclosure methods may cause local environmental perturbations to the area under study, resulting in inaccurate or misleading flux estimates. Given the abundance of data derived with enclosure techniques, it is imperative that the validity of such measurements be assessed. The primary goal of NOVA was the intercomparison and assessment of methodologies used to derive NO flux estimates. The eddy correlation technique provides an undisturbed direct measure of the flux and was selected to provide benchmark fluxes with which the results from chamber methods can be compared.
Atmospheric mercury is one of the most worrying of the airborne trace metal issues of today.
Recently, the experimental techniqes have been developed sufficiently that field testing has been conducted, with considerable success. Initial tests were conducted over soils contaminated with mercury and yielded consistent determinations of the rate of loss of mercury vapor from them. More recently, field studies have been conducted in southern Florida, where mercury originating from sugar farming practices is suspected to be affecting coastal ecosystem viability. The results indicate that it is indeed possible to measure the rate of gaseous transfer of atmospheric mercury to coastal ecosystems, and that questions concerning the relative importance of dry and wet delivery mechanisms can now be answered. In fact, the threat to the aquatic ecosystems is growing, not diminishing.