Heiko Langner

Diagnostic Analysis of Veterinary Dried Blood Spots for Toxic Heavy Metals Exposure

Dried blood spots (DBS) on filter paper have been used in human medicine since the 1960s, predominantly for screening in-borne metabolic disorders and more recently, for toxicology. Despite its 50-year existence, this technology has not been adopted by veterinarians for routine diagnoses and research. We have validated a novel DBS analytical procedure for the routine measurement of toxic heavy metals using 50 µL of whole blood on a single DBS by inductively coupled plasma mass spectrometry (ICP-MS). Targeted heavy metals are arsenic, cadmium, mercury, lead, selenium and thallium. The limits of quantitation (LOQ) on DBS are: arsenic 1.7 µg/L, cadmium 4.0 µg/L, mercury 13.7 µg/L, lead 13.3 µg/L, selenium 6.3 µg/L and thallium 1.5 µg/L. These LOQs suffice for routine diagnoses of heavy metal intoxication in domesticated and wildlife species as well as for basic, applied and epidemiological studies. The technique is ideal for population studies involving investigations of wildlife exposure to heavy metals and other environmental pollutants. The small blood volume involved (50 µL) makes it feasible to study small animals (birds, reptiles, amphibians and small mammals) that were previously excluded, or difficult to study due to the relatively large sample volumes required by current gold standard blood collection techniques.

Hydrological controls on chemical weathering rates at the soil-bedrock interface

Chemical weathering of bedrock is critical to maintaining terrestrial life, and climate, typically as manifested by precipitation, is often identified as having a first-order control on rates of chemical weathering. The ability of precipitation to dissolve rock, however, is modulated by the properties of the overlying soil that influence the contact time between water and minerals. Flume experiments were conducted to investigate the hydrological controls on rates of chemical weathering. Solute concentrations of runoff flowing across synthetic bedrock overlain by nonreactive pseudosoils of differing hydraulic conductivities were measured to examine the role of seepage velocity in influencing weathering rates on steep slopes. The results suggest that, where weathering is not limited by the supply of fresh minerals, weathering rates should increase with decreasing hydraulic conductivity. In addition, a mathematical relationship between hydraulic conductivity and chemical weathering on hillslopes is introduced to explore the hydrological controls on feldspar and calcite dissolution rates. The mathematical model supports the results from the experiments.