Preliminary Jamestown Conclusions

So, here I am. It is the last week of official summer research for 2012 and what have I accomplished? I managed to gather between 20 and 23 Jamestown groundwater samples each week for nine weeks, that amounts to roughly 200 samples! Half of the samples were analyzed for iron, arsenic and dissolved organic carbon to determine the concentrations of these species and the degree to which dissolved arsenic and iron in the early colonists’ drinking water caused or (at the very least) exacerbated illnesses recorded in historical documents. Only 2 of 119 samples analyzed for arsenic, came back with values exceeding the WHO and EPA drinking water standard of 10 parts-per-billion (ppb)  arsenic. And even still, these values were 12.2ppb and 14.5 ppb, certainly prolonged exposure to these levels of inorganic arsenic could cause skin and lung irritation, but the health affects were likely minimal for the early colonists. BUT, prolonged exposure to high levels of organic arsenic can cause nerve injury and stomachaches, and thus, there is work left to be finished. My next step is to run my samples through a UV-Digester which will liberate any organic  arsenic attached to organic compounds ( up to 90% of arsenic in waters can be attached to organic compounds), which can be potentially metabolized by the human body.

In terms of iron, the early colonists would have paused when they brought water up from their wells. Surely they would have noticed the dark orange solids characteristic of groundwater flowing near the Pitch and Tar swamp. Iron concentrations were elevated beyond the WHO and EPA drinking water limit of 0.3 parts-per-million (ppm), up to 82 ppm! Though iron concentrations are very high, iron in excess is not nearly as toxic to the human body. I expected to find a positive relationship between iron and arsenic where the more iron I found in a sample, the more arsenic. However, this does not seem to be the case indicating that controls on arsenic are primarily from physical processes (groundwater flow path, volume, velocity, precipitation) rather than chemical processes, such as co-precipitation of iron and arsenic. Thus my project has taken a new course, and I will now be investigating how precipitation and groundwater flow, flow direction and velocity affect the chemistry of each well at Jamestown.

Iron Analyses