These questions were synthesized and posed to the class following Dr. Barne’s talk.

 1. Why is it important to study the impact of urban areas on the environment?

To quote Rebecca Barnes talk, “Why should we care about urban areas impact on the environment? We should care because we live in them”. 80% of people that live in the United States reside in urban areas and as the developing world continues to industrialize similar levels of urbanization will be reached worldwide. Further, although urban areas have smaller physical footprints then rural areas their, ecological footprints can be tens to hundreds of times greater (Grimm et al. 2008). This environmental footprint includes effects such as, “changes in land use and cover, biogeochemical cycles, climate, hydrosystems, and biodiversity” (Grimm et al. 2008).

 2. How do urban areas impact the hydrology of a system?

Within urban areas infiltration rates decrease and runoff volumes increase. Urban areas have increased levels of impervious surfaces, which contribute to increased runoff volumes and decreased infiltration rates.

 3.     What makes the study of carbon and nitrogen cycling a useful endeavor?

The chemical species of carbon and nitrogen serve crucial roles in biological and physical processes. However, excess levels of either one can have detrimental effects. The emission of NOx into the atmosphere can result in the production of photochemical smog. Excess nitrogen in aquatic systems can be a groundwater contaminate or create harmful algal blooms. Increasing levels of carbon in aquatic systems can lead to higher atmospheric carbon dioxide levels and thus contribute to climate change and ocean acidification.

4.     What percentage of nitrogen output makes it to the ocean and where does the rest go?

25% of nitrogen output makes it to the ocean. The fate of the other 75% is not well understood.

5.     What is the global impact of increased DIC in streams and how important are human activities to creating this problem?

CO2 is emitted from streams to the atmosphere at a rate of 0.9 Tg per year. This is a greater source of CO2 then emissions from all the cars in America. One quarter of all carbon inputs are due to human activity. This is probably an underestimate due to recent studies.

 6.     What conditions make the southern portion of the Connecticut River watershed a useful area in which to nitrogen and carbon biogeochemical cycling?

The region is dominated by quartz bedrock, and “carbonate lithologies are not present” (Barnes 2009). This effectively eliminates contributions of DIC from weathering of bedrock making analysis of DIC levels due to land use and human input easier to quantify.

 7.     Why is the study of watersheds important?

Watersheds are excellent indicators of the health of an entire ecosystem.

8.     How does Dr. Barnes utilize isotopic analysis to determine sources of carbon and nitrogen?

Atoms exist in a variety of different stable isotopes. Different biological, chemical and physical mechanisms create systems enriched in a specific stable isotope. Microbial denitrification enriches nitrate with 15N. “Nitrification, in contrast, results in the preferential incorporation of the lighter isotopes into NO3– and often leads to a decrease in d15N-NO3– (Barnes 2010). Therefore, by analyzing the ratio of specific stable isotopes the source of nitrogen containing chemical species can be determined.

 9.     Why was there little denitrification occurring in the soils and groundwater within Dr. Barnes’s study region?

The region that Dr. Barnes worked in is characterized by as a shallow sandy aquifer. This type of sediment allows for high levels of oxygenation. When oxygen is present denitrification does not readily occur, because oxygen is a much better electron acceptor then Nitrate.

 10.  From a policy standpoint what makes problems associated with nitrogen different?

The problems associated with Nitrogen are not given the same level of concern as other pollutants. There is less accountability due largely to the fact that small point sources contribute immensely to the problem.

 11.  Where is Dr. Barnes’s working now?

 At Bard College Center for Environmental Policy. The center is based on an integrated approach to environmental policy. Includes scientific, economic, legal and political training. The program includes a 4-6 month internship.