PICT

Fmlaysoii-Picts, B. J., and Pitts, J. N., Jr. (2000). Chemistry of the Upper and Lower Atmosphere Theory, Experiments, and Applications. San Diego Academic Press. 

Pun on to bus i road without 00Wn9 to pict up a personal item. Z. Use a mobile phone. 

Grants from CONICET, Secyt UNC, Agenda Cdrdoba Ciencia, Program BID 1201/ OC-AR PICT No. 06-12485 are acknowledged. 

In maiK- applications, the spectral residuals will not behave in the ideal manner as picted here. Some nonrandom behavior may be tolerable depending on the performance requirements of the model. If the residuals are lai e and fire model performance is not acceptable, an inverse model approach sudias PLS or PCR (Section 5.3) can be considered. 

Measurement of PICT usually involves carrying out short-term (multispecies) toxicity tests on whole communities from clean and contaminated sites. Pollution tolerance is quantified by reduced sensitivity of the toxicant in these tests. The increased tolerance may result from replacement of sensitive species by less sensitive ones, development of heritable tolerance by one or more species, and/or short-term nonheritable acclimation. A significant increase in community tolerance compared to the baseline tolerance at reference sites suggests that the community has been adversely affected by toxicants. In this way, PICT can establish causal linkages between contaminants and effects in monitoring studies (Blanck 2002). 

PICT has received significant attention in the last decade, particularly when applied to communities of periphyton, phytoplankton, bacteria, nematodes, and insects. Overall, these organisms have short generation times that offer opportunities for rapid adaptations. To date, mainly metals, herbicides, and biocides have been evaluated in PICT studies (Blanck 2002). 

Sensitivity of populations and communities to toxic stress may be influenced by exposure history. Tolerance can be acquired by an individual due to physiological acclimation or by genetic adaptation. At the community level, PICT may result from... 

Our observations are similar to those of Blanck et al. (2003), who studied the variability in zinc tolerance in periphyton communities sampled from 15 European river stretches using the PICT concept. Due to differences in water chemistry, (history of) metal pollution, species composition, and other biotope characteristics, the regional uncertainty factor for Zn was estimated to range from 1.7 to 4.3, and the interregional uncertainty factor from 2.4 to 8.6, when extrapolating periphyton tolerances from river to river (Blanck et al. 2003). 

Blanck H. 2002. A critical review of procedures and approaches used for assessing pollution-induced community tolerance (PICT) in biotic communities. Human Ecol Risk Assess 8 1003-1034. 

Blanck H, Dahl B. 1996. Pollution-induced community tolerance (PICT) in marine periphyton in a gradient of tri-n-butyltin (TBT) contamination. Aquat Toxicol 35 59-77. 

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