U.S. Geological Survey Data Research Articles

Incidence of abdominal wall defects is related to surface water atrazine and nitrate levels

Background Gastroschisis and omphalocele are congenital abdominal wall defects (AWD). Atrazine and nitrates are common agricultural fertilizers. Methods The Centers for Disease Control and Prevention natality data set was used to collect data for patients with AWD born between January 1990 and December 2002. Similar data were obtained from the Indiana State Department of Health. An estimated date of conception was calculated by birth date and gestational age. Surface water nitrate and atrazine levels for Indiana were collected from US Geological Survey data. Midwest was defined as Indiana, Illinois, Iowa, Ohio, and Nebraska. Statistical analysis was performed by χ 2 test and Pearson correlation for P ≤ .05. Results The Centers for Disease Control and Prevention identified 9871 children with AWD in 1990 and in 1995-2001 of 35,876,519 live births (rate 2.75/10 5). In Indiana, 358 children from 1990-2001 had AWD of 1,013,286 live births (rate 3.53/10 5). The AWD rate in Indiana was significantly higher than the national rate in 1996 ( P = .0377), 1998 ( P = .0005), and 2001 ( P = .0365) and significantly higher than the Midwest rate in 1998 ( P = .0104). Monthly comparison demonstrated a positive correlation of AWD rate and mean atrazine levels ( P = .0125). Conclusion Indiana has significantly higher rates of AWD compared with national rates. Increased atrazine levels correlate with increased incidence of AWD.

Relative toxicity and occurrence patterns of pesticide mixtures in streams draining agricultural watersheds dominated by corn and soybean production

To evaluate the relative toxicity and the occurrence patterns of pesticide mixtures in streams draining agricultural watersheds, a 3-step approach was used. First, a landscape of interest was identified, defined, and isolated. Second, the relative toxicity of mixtures, on the basis of pesticide toxicity index scores, was compared with the relative toxicity of the highest individual pesticide, on the basis of highest toxicity quotient values. Third, occurrence patterns of pesticide mixtures were identified for use in follow-up mechanistic studies. The landscape of interest was identified as the corn and soybeans crop setting and concentrations of pesticides in streams within this crop setting were determined from US Geological Survey data. Pesticide toxicity index scores for individual samples were highest for the primary producers, Pseudokirchneriella subcapitata and Lemna gibba; with 95th percentile pesticide toxicity index scores of 4.7 and 1.9, respectively. The 95th percentile pesticide toxicity index score for Daphnia magna was 0.40 when a chronic sublethal endpoint was used. Pesticide toxicity index values were above the highest toxicity quotient values, indicating that consideration of mixtures does increase the estimated risk, but pesticide toxicity index scores were generally within a factor of 2 of highest toxicity quotient values, indicating that the increased risk is not large for most samples. Pesticide toxicity index scores tended to be dominated by individual pesticides and simple mixtures. Two different prioritization strategies were used to identify important mixtures for further study on the basis of potential effects on P. subcapitata. Both techniques decreased the complexity of the pesticide mixtures to consider by reducing the number of components within the identified mixtures as well as identifying a few specific combinations that constitute the majority of mixtures within the sample. Nearly all important pesticides for P. subcapitata were herbicides from 2 chemical classes: acetanilide and triazine herbicides.

Relative Toxicity and Occurrence Patterns of Pesticide Mixtures in Streams Draining Agricultural Watersheds Dominated by Corn and Soybean Production

To evaluate the relative toxicity and the occurrence patterns of pesticide mixtures in streams draining agricultural watersheds, a 3-step approach was used. First, a landscape of interest was identified, defined, and isolated. Second, the relative toxicity of mixtures, on the basis of pesticide toxicity index scores, was compared with the relative toxicity of the highest individual pesticide, on the basis of highest toxicity quotient values. Third, occurrence patterns of pesticide mixtures were identified for use in follow-up mechanistic studies. The landscape of interest was identified as the corn and soybeans crop setting and concentrations of pesticides in streams within this crop setting were determined from US Geological Survey data. Pesticide toxicity index scores for individual samples were highest for the primary producers, Pseudokirchneriella subcapitata and Lemna gibba; with 95th percentile pesticide toxicity index scores of 4.7 and 1.9, respectively. The 95th percentile pesticide toxicity index score for Daphnia magna was 0.40 when a chronic sublethal endpoint was used. Pesticide toxicity index values were above the highest toxicity quotient values, indicating that consideration of mixtures does increase the estimated risk, but pesticide toxicity index scores were generally within a factor of 2 of highest toxicity quotient values, indicating that the increased risk is not large for most samples. Pesticide toxicity index scores tended to be dominated by individual pesticides and simple mixtures. Two different prioritization strategies were used to identify important mixtures for further study on the basis of potential effects on P. subcapitata. Both techniques decreased the complexity of the pesticide mixtures to consider by reducing the number of components within the identified mixtures as well as identifying a few specific combinations that constitute the majority of mixtures within the sample. Nearly all important pesticides for P. subcapitata were herbicides from 2 chemical classes: Acetanilide and triazine herbicides.

A Comparison of Modeled Flood Characteristics to Measurements of the 2002 Flood on the Guadalupe River, Texas

There are a number of equations and models for calculating flood probabilities and associated peak discharges, and this paper compares a model and an empirical calculation. We calculated flood characteristics for the upper Guadalupe watershed in central Texas using the Weibull formula and data available from a local gauging station, to the result given by the National Flood Frequency (NFF) program, developed by the U.S. Geological Survey (USGS). During the summer of 2002, the upper Guadalupe watershed received a total of 89 cm (35 in.) of precipitation over a one-week period, producing record flooding. The results from both the NFF program and the calculation of return intervals using gauging station data are compared to the measured peak flows for the summer of 2002. The peak discharges predicted by both the NFF model and from the USGS gauging station data are much higher than the recorded discharge. There may be an increase of flow inputs to the Guadalupe River between the locations of the gauging station and where the flood estimate was made. Assuming an increase from tributaries into Canyon Lake, the estimate of peak discharge obtained from USGS data much more closely matches the recorded flow than the results from the NFF program.

Topographic analyses of K*lauea Volcano, Hawai'i, from interferometric airborne radar

We analyze digital topographic data collected in September 1993 over a ∼500-km2 portion of K*lauea Volcano, Hawai'i, by the C-band (5.6-cm wavelength) topographic synthetic aperture radar (TOPSAR) airborne interferometric radar. Field surveys covering an ∼1-km2 area of the summit caldera and the distal end of an ∼8-m-thick 'a'* flow indicate that the 10-m spatial resolution TOPSAR data have a vertical accuracy of 1–2 m over a variety of volcanic surfaces. After conversion to a common datum, TOPSAR data agree favorably with a digital elevation model (DEM) produced by the U.S. Geological Survey (USGS), with the important exception of the region of the ongoing eruption (which postdates the USGS DEM). This DEM comparison gives us confidence that subtracting the USGS data from TOPSAR data will produce a reasonable estimate of the erupted volume as of September 1993. This subtraction produces dense rock equivalent (DRE) volumes of 392, 439, and 90×106 m3 for the Pu'u '*'*, K*pa'ianah*, and episode 50–53 stages of the eruption, respectively. These are 124, 89, and 94% of the volumes calculated by staff of the Hawaiian Volcano Observatory (HVO) but do not include lava of K*pa'ianah* and episodes 50–53 that flowed into the ocean and are thus invisible to TOPSAR. Accounting for this lava increases the TOPSAR volumes to 124, 159, and 129% of the HVO volumes. Including the ±2-m uncertainty derived from the field surveys produces TOPSAR-derived volumes for the eruption as a whole that range between 81 and 125% of the USGS-derived values. The vesicularity- and ocean-corrected TOPSAR volumes yield volumetric eruption rates of 4.5, 4.5, and 2.7 m3/s for the three stages of the eruption, which compare with HVO-derived values of 3.6, 2.8, and 2.1 m3/s, respectively. Our analysis shows that care must be taken when vertically registering the TOPSAR and USGS DEMs to a common datum because C-band TOPSAR penetrates only partially into thick forest and therefore produces a DEM within the tree canopy, whereas the USGS DEM is adjusted for vegetation.

Numerical modelling and computer visualization of the storm surge in and around the Croatan-Albemarle-Pamlico estuary system produced by hurricane Emily of August 1993

Hurricane Emily unleashed its fury on the Outer Banks of North Carolina on 31 August 1993. Storm surge was a major cause of damage along the Outer Banks. The highest flood water (11-11.5ft) occurred in the Buxton area near Cape Hatteras, North Carolina. It was reported that this flood water was from storm surges along the sound side of the barrier islands. An experimental forecast was conducted for this event in real time using Croatan-Albemarle-Pamlico estuary systems (CAPES) storm surge prediction model developed at North Carolina State University (NCSU). It uses as input parameters the projected hurricane track, minimum center pressure, maximum sustained wind speed and radius of maximum wind speed provided by the National Hurricane Center (NHC). The forcing of the model also includes fresh water input from sound system rivers, and of coastal waters intruding into the sound via Ocracoke, Hatteras and Oregon inlets. The predicted maximum surge along the sound side of the Outer Banks was within 85-90% of the post-storm highwater-mark survey data provided by the U.S. Geological Survey (USGS). Albeit, an after the fact simulation using the post-storm analysis of the track of Emily provided by the NHC, the maximum storm surge along the sound side of the Outer Bancks predicted by the model was within 95-98% of the maximum highwater mark data. The location of the predicted maximum surge for both pre and first model runs was near Cape Hatteras, which agreed well with USGS's survey data. We conclude that the CAPES storm surge model is capable of providing accurate storm surge forecasts in and around the CAPES, but such forecasts are sensitive to not only the observed storm size and intensity but in particular, the projected storm track.

Horizontal strain across the Wasatch Front near Salt Lake City, Utah

Two adjacent geodetic networks span a 105‐km extent of the Wasatch fault zone in north‐central Utah. One of the networks, located in the vicinity of Salt Lake City, was observed by the National Ocean Service/National Geodetic Survey (NOS/NGS) in 1962–1963 (triangulation mode) and again in 1973–1974 (combined triangulation‐trilateration mode). To the north, in the vicinity of Ogden, the U.S. Geological Survey (USGS) performed five separate trilateration surveys of the second network during the 1972–1981 interval. When fit to a model assuming both temporal and spatial homogeneity for the strain rate, the two independent data sets yield mutually consistent strain rate tensors. Subsets of the NOS/NGS data, however, suggest spatial variation in the strain field, and a subset of the USGS data indicates a possible temporal variation in the strain rate. The quality of the data is such that we are uncertain whether or not these apparent variations represent actual tectonic signals. The strain rate tensors for the two complete data sets suggest an underlying deformational pattern characterized by east‐west (E‐W) maximum principal strain (extension positive). This pattern may also be inferred from regional seismicity and Quaternary geology. The suspected variations would imply that the area to the north of Salt Lake City experienced significant E‐W compression preceding 1978, in contradiction to the underlying strain pattern. This compression may be caused by the mountainous block, eastward adjacent to the fault zone, displacing westward along a shallow‐angle, west dipping detachment surface. We speculate on the existence of an E‐W trending zone of weakness, for example, secondary faults, located north of Salt Lake City to explain how the stress field to the north may be decoupled from that to the south where E‐W compression has not been detected. While seismic and geologic information contribute some plausibility to our speculations, the evidence for the existence of the suspected variations is inconclusive.