History of nutrient inputs to the northeastern United States, 1930–2000

Humans have dramatically altered nutrient cycles at local to global scales. We examined changes in anthropogenic nutrient inputs to the northeastern United States (NE) from 1930 to 2000. We created a comprehensive time series of anthropogenic N and P inputs to 437 counties in the NE at 5 year intervals. Inputs included atmospheric N deposition, biological N2 fixation, fertilizer, detergent P, livestock feed, and human food. Exports included exports of feed and food and volatilization of ammonia. N inputs to the NE increased throughout the study period, primarily due to increases in atmospheric deposition and fertilizer. P inputs increased until 1970 and then declined due to decreased fertilizer and detergent inputs. Livestock consistently consumed the majority of nutrient inputs over time and space. The area of crop agriculture declined during the study period but consumed more nutrients as fertilizer. We found that stoichiometry (N:P) of inputs and absolute amounts of N matched nutritional needs (livestock, humans, crops) when atmospheric components (N deposition, N2 fixation) were not included. Differences between N and P led to major changes in N:P stoichiometry over time, consistent with global trends. N:P decreased from 1930 to 1970 due to increased inputs of P, and increased from 1970 to 2000 due to increased N deposition and fertilizer and decreases in P fertilizer and detergent use. We found that nutrient use is a dynamic product of social, economic, political, and environmental interactions. Therefore, future nutrient management must take into account these factors to design successful and effective nutrient reduction measures

Vector Reflectometry in a Beam Waveguide

We present a one-port calibration technique for characterization of beam waveguide components with a vector network analyzer. This technique involves using a set of known delays to separate the responses of the instrument and the device under test. We demonstrate this technique by measuring the reflected performance of a millimeter-wave variable-delay polarization modulator

Low Mass Dimuons Produced in Relativistic Nuclear Collisions

The NA60 experiment has measured low-mass muon pair production in In-In collisions at 158 A GeV with unprecedented precision. We show that this data is reproduced very well by a dynamical model with parameters scaled from fits to measurements of hadronic transverse mass spectra and Hanbury-Brown and Twiss correlations in Pb-Pb and Pb-Au collisions at the same energy. The data is consistent with in-medium properties of $\rho$ and $\omega$-mesons at finite temperature and density as deduced from empirical forward-scattering amplitudes. Inclusion of the vacuum decay of the $\rho$-meson after freeze-out is necessary for an understanding of the mass and transverse momentum spectrum of dimuons with M \apprle 0.9 {\rm GeV}/c^2.Comment: 4 pages, 3 figures, updated hadronic analysi

Effects of Zebra, Mussel, Dreissena Polymorpha Infestation on Lake Dardanelle Water Quality

Zebra mussels recently invaded southern waterways including the Arkansas River. Large-scale filtration of suspended particulate matter by dense populations could alter reservoir ecosystem function. Furthermore, they attach to hard surfaces, thereby threatening normal operations of artificial structures. We designed this study to provide baseline data prior to establishment of high population levels of zebra mussels in Lake Dardanelle. The characterization of spatial and temporal variability in water quality, zooplankton, phytoplankton, and macrophytes will allow testing of several hypotheses. We sampled zebra mussel veliger and settling juvenile densities and zooplankton densities at four fixed sites and the key water quality variables at three of the sites biweekly from July 1995 through June 1996. Data from previous years regarding the above parameters is contained in other reports. Production of zebra mussel veligers was approximately the same between the 1994-1995 and 1995-1996 sample seasons, but the number of adults increased dramatically. Veliger density frequently exceeded 20/L and the mean density of adults was \u3e 4,000 m2 during the 1995-1996 sample season. We observed substantial increases in ion concentrations, phosphate, conductivity, and Secchi disk visibility this sample season compared to the 1994-1995 sample season. Mean concentrations for calcium, magnesium, sulfate, chloride, and phosphate increased 43%, 42%, 42%, 48%, and 50%, respectively. Mean conductivity increased 44%, and four of the five highest Secchi disk readings taken the past three years were recorded in 1996. We observed substantial decreases in turbidity (31%), total dissolved solids (23%), and total phosphorous (13%). Densities of major zooplankton taxa were not substantially different this season compared with the 1994-1995 sample season. We observed slight increases in mean concentrations of chlorophylls a, b, and c, and a slight decrease in the mean percent coverage of rooted marcrophytes, but the values were not substantially different than those that we observed during the 1994-1995 sample season

The biogeochemical influence of nitrate, dissolved oxygen, and dissolved organic carbon on stream nitrate uptake

Streams are potential hotspots for retention and removal of NO3−, and understanding the mechanisms that enhance NO3− reactivity in stream systems is critical for predicting and preventing eutrophication. Both dissolved organic C (DOC) and dissolved O2 (DO) influence NO3− removal processes. Assessing the individual impacts of NO3−, DO, and DOC concentrations on stream NO3− removal is difficult because these factors covary and are coupled through the C and N cycles. We used an experimental approach to quantify the influences of NO3−, DOC, and DO on NO3− transport in headwater streams of the Ipswich and Parker River watersheds (Massachusetts, USA) with contrasting levels of DOC and DO. In a 1st set of experiments, we added NO3− to address how uptake kinetics differed between a low-DO/high-DOC stream (Cedar Swamp Creek) and a high-DO/low-DOC stream (Cart Creek). In a 2nd set of experiments, we manipulated, for the first time at the reach scale, both DO and DOC in a factorial experiment. DO was added to the low-DO stream by injecting O2 and was removed from the high-DO stream by adding sodium sulfite. DOC was added both alone and in combination with the DO manipulations. NO3− concentration was an important control of NO3− uptake velocity in our study streams, consistent with previous findings. The results of the DOC and DO manipulations suggested that DO determines whether a stream has net NO3− uptake or production and that the presence of DOC magnifies the DO response processes. Addition of DOC by itself did not lead to increased NO3− uptake. In addition, we observed organic matter priming effects, wherein the addition of labile organic matter resulted in accelerated metabolism of naturally occurring DOC in the water column. Priming effects have not been reported previously in stream systems. Results from our experiments suggest that NO3− uptake in streams might arise from complex interactions among DOC, DO, and NO3−, and ultimately, from the influence of DO on dominant stream processes

A geotechnical Study on the Characteristics of Swell-Shrink Soils in Kibaha, Tanzania

The properties of Swell-shrink of the soils in Kibaha were studied. Geotechnical and mineralogical tests were carried out on disturbed and undisturbed samples recovered from trial pits at different locations. Using empirical relationships, the swelling potential of the soil was established in correlation with the soil plasticity limits and grain size analysis (claycontents). The average values for the plastic, liquid and linear shrinkage limits for soils were 22.2%, 60.7% and 14.5% respectively. The plasticity Index (PI) which is the difference between liquid limits and plastic limits ranges from 27% to 47.4% with an average of 38.5%. The natural water content is very small ranging from 7% to 11% with an average of9.6% which is smaller than the corresponding shrinkage limit. Furthermore, the samples were tested for percentage of volume change in free swell tests and swelling pressure in one-dimensional swell tests. The free swell and upward pressure were in the excess of 100% to 150% and 50 kPa respectively. In addition, the coefficient of linear extensibility ranged from 0.09 to 0.14 signifying high to very high swell-shrink potential. Finally, the main clay mineral present in the sample was determined by running the X-ray diffraction (XRD) test. The x-ray diffraction scan indicated the presence of high proportion of clay minerals (smectite) in the soils

Racial and Ethnic Disparities in COVID-19: Evidence from Six Large Cities

As of June 2020, the coronavirus pandemic has led to more than 2.3 million confirmed infections and 121 thousand fatalities in the United States, with starkly different incidence by race and ethnicity. Our study examines racial and ethnic disparities in confirmed COVID-19 cases across six diverse cities – Atlanta, Baltimore, Chicago, New York City, San Diego, and St. Louis – at the ZIP code level (covering 436 “neighborhoods” with a population of 17.7 million). Our analysis links these outcomes to six separate data sources to control for demographics; housing; socioeconomic status; occupation; transportation modes; health care access; long-run opportunity, as measured by income mobility and incarceration rates; human mobility; and underlying population health. We find that the proportions of black and Hispanic residents in a ZIP code are both positively and statistically significantly associated with COVID-19 cases per capita. The magnitudes are sizeable for both black and Hispanic, but even larger for Hispanic. Although some of these disparities can be explained by differences in long-run opportunity, human mobility, and demographics, most of the disparities remain unexplained even after including an extensive list of covariates related to possible mechanisms. For two cities – Chicago and New York – we also examine COVID-19 fatalities, finding that differences in confirmed COVID-19 cases explain the majority of the observed disparities in fatalities. In other words, the higher death toll of COVID-19 in predominantly black and Hispanic communities mostly reflects higher case rates, rather than higher fatality rates for confirmed cases