Evgeni Eltzov, Vladimir Slobodnik, Rodica E. Ionescu, Robert S. Marks. On-line biosensor for the detection of putative toxicity in water contaminants. Talanta 2015-01-15 132:583-590
Potential threat on drinking water requires monitoring solutions, such as the one proposed herein, as a real-time, wide ranged, water monitoring system to detect the presence of toxicants in water. We studied the role of a selected number of parameters affecting performance and, thus, improved the prototype into an optimized next-generation device, resulting in enabling increased measurement duration, coupled with increased sensitivity. The chosen parameters in question were the peristaltic flow system, the fiber probe matrix stability through a re-design of the fiber probe holder and flow unit cell, as well as the modulation of bacterial medium concentration to increase bioreporter performance while keeping biofouling in check. Measurements were made with spiked samples and validated with polluted field-collected samples.
The assumption is made in dendochronology that tree-rings accurately reconstruct temperature variations. But this study in California shows that growth of bristlecone pines varies significantly depending on altitude, and where the trees are located (e.g. North or South side of a mountain). Further, the authors note that such differences are often not temperature-related. For this and other reasons I am not a fan of using tree ring studies to reconstruct atmospheric temperatures because the initial assumption (that tree-rings accurately reconstruct temperature variations) is false. Tree rings are certainly affected by temperatures, but to go the other way (reconstruct temperatures from tree rings) is inappropriate as well as inaccurate.
Matthew W Salzer, Evan R Larson, Andrew G Bunn and Malcolm K Hughes. Changing climate response in near-treeline bristlecone pine with elevation and aspect 2014 Environ. Res. Lett. 9 114007 doi:10.1088/1748-9326/9/11/114007
In the White Mountains of California, eight bristlecone pine (Pinus longaeva) tree-ring width chronologies were developed from trees at upper treeline and just below upper treeline along North- and South-facing elevational transects from treeline to ~90 m below. There is evidence for a climate-response threshold between approximately 60–80 vertical m below treeline, above which trees have shown a positive growth-response to temperature and below which they do not. Chronologies from 80 m or more below treeline show a change in climate response and do not correlate strongly with temperature-sensitive chronologies developed from trees growing at upper treeline. Rather, they more closely resemble lower elevation precipitation-sensitive chronologies. At the highest sites, trees on South-facing slopes grow faster than trees on North-facing slopes. High growth rates in the treeline South-facing trees have declined since the mid-1990s. This suggests the possibility that the climate-response of the highest South-facing trees may have changed and that temperature may no longer be the main limiting factor for growth on the South aspect. These results indicate that increasing warmth may lead to a divergence between tree growth and temperature at previously temperature-limited sites.
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