In the Laurentian Great Lakes region, the double-crested cormorant (Phalacrocorax auritus) has seen a thousand-fold population increase in recent decades. These large colonies of birds now often conflict with socioeconomic interests, particularly due to perceived competition with fisheries and the destruction of terrestrial vegetation in nesting habitats. Here we use dated sediment cores from p...

Identifying the sources and impacts of organic and inorganic contaminants at the watershed scale is a complex challenge because of the multitude of processes occurring in time and space. Investigation of geochemical transformations requires a systematic evaluation of hydrologic, landscape, and anthropogenic factors. The 1160 km2 Boulder Creek Watershed in the Colorado Front Range encompasses a ...

The characterization of the transfer of pesticides to and in groundwater is essential for effective water resource management. Intensive monitoring, from October 1989 to May 2006, of a weakly karstified chalk aquifer system in a 50 km agricultural catchment, enabled the characterization of the temporal variability of pesticide concentrations in the groundwater of the main outlet. Atrazine and i...

The frequent formation of large igneous provinces during the opening of the Atlantic Ocean is a surface manifestation of the thermal and chemical state of convecting mantle beneath the supercontinent Pangea. Recent geochemical and geophysical findings from the North Atlantic igneous province all point to the significant role of incomplete mantle mixing in igneous petrogenesis. On the basis of a...

In this study, we show that the rate of shell precipitation in the extant planktic foraminifer Orbulina universa is sufficiently rapid that 12 h calcification periods in O-labeled seawater can be resolved and accurately measured using secondary ion mass spectrometry (SIMS) for in situ dO analyses. Calcifying O. universa held at constant temperature (22 C) were transferred every 12 h between amb...

The Crozet Archipelago, in the Indian sector of the Southern Ocean, constitutes one of the few physical barriers to the Antarctic Circumpolar Current. Interaction of the currents with the sediments deposited on the margins of these islands contributes to the supply of chemical elements—including iron and other micro-nutrients—to offshore high-nutrient, low-chlorophyll (HNLC) waters. This natura...

Pathways of streamflow were investigated using geochemical tracers in ungauged headwater and higher-order streams in the semi-arid, forested, Valles Caldera, New Mexico. Combining diagnostic tools of mixing models and endmember mixing analysis (EMMA) shows that streamflow at East Fork Jemez River and San Antonio West (both > 120 km2) was controlled by mixing of three endmembers: near-surface ru...

Information about the times of thermal breakthrough and subsequent rates of thermal drawdown in enhanced geothermal systems (EGS) is necessary for reservoir management, designing fracture stimulation and well drilling programs, and forecasting economic return. Thermal breakthrough in heterogeneous porous media can be estimated using conservative tracers and assumptions about heat transfer rates...

The Jacuí Delta drains into Lake Guaíba which is the main source of water for more than two million people in South Brazil and has suffered from pollution with heavy metals phosphorus. objective current research to demonstrate how use sediment tracing techniques, combination flux monitoring, can improve understanding contributions one largest lakes America. monitoring results were based on data...