scholarly journals A Bayesian Approach to Infer Nitrogen Loading Rates from Crop and Landuse Types Surrounding Private Wells in the Central Valley, California

2017 ◽  
Author(s):  
Katherine M. Ransom ◽  
Andrew M. Bell ◽  
Quinn E. Barber ◽  
George Kourakos ◽  
Thomas Harter
Keyword(s):  
Loading Rate ◽  
Probability Distributions ◽  
Central Valley ◽  
Nitrogen Loading ◽  
Bayesian Regression ◽  
Nitrate Contamination ◽  
Agricultural Crop ◽  
Loading Rates ◽  
The Impact ◽  
Private Wells

Abstract. Nitrate contamination of alluvial aquifers in agricultural areas is a typical and major problem around the world. Nitrogen applied to crops, in the form of synthetic fertilizers or manure, in excess of plant uptake, largely leaches to groundwater in the form of nitrate, which is stable and highly mobile in oxygen-rich groundwaters. Increased awareness of the impact that excess nitrogen has had on groundwater and major health concerns about nitrate are prompting new regulations for farmers, e.g., in Europe and California, USA. This study is focused in the Central Valley, California, USA, an intensively farmed region with high agricultural crop diversity. Though nitrogen loading rates for several crop and landuse types in the Central Valley have been estimated or measured in a handful of studies, nitrogen loading rates for specific crop or landuse types and their impact to groundwater quality remain largely unknown. Knowledge of crop or other landuse specific groundwater nitrate impact may aid future regulatory decisions. Nitrogen loading rates for specific crop or landuse types are expected to vary depending on individual landuse practices; and interactions with hydrogeologic parameters that may promote or inhibit nitrate leaching. In this study, we developed a novel Bayesian regression model that allowed us to estimate crop or other landuse-specific groundwater nitrogen loading rate probability distributions from surveys of private wells, each of which is likely impacted by more than one landuse. We used recent nitrate measurements from 2149 wells in the Central Valley. We estimated nitrogen loading rate distributions for 15 crop and landuse groups. These were shown to compare favorably with prior mass-balance estimates of loading rates based on agronomic estimates of nitrogen loading.

scholarly journals A Bayesian approach to infer nitrogen loading rates from crop and land-use types surrounding private wells in the Central Valley, California

2018 ◽  
Vol 22 (5) ◽  
pp. 2739-2758 ◽  
Author(s):  
Katherine M. Ransom ◽  
Andrew M. Bell ◽  
Quinn E. Barber ◽  
George Kourakos ◽  
Thomas Harter
Keyword(s):  
Land Use ◽  
Mass Balance ◽  
Groundwater Age ◽  
Central Valley ◽  
Nitrogen Loading ◽  
Bayesian Regression ◽  
Agricultural Crop ◽  
Loading Rates ◽  
Land Use Types ◽  
Private Wells

Abstract. This study is focused on nitrogen loading from a wide variety of crop and land-use types in the Central Valley, California, USA, an intensively farmed region with high agricultural crop diversity. Nitrogen loading rates for several crop types have been measured based on field-scale experiments, and recent research has calculated nitrogen loading rates for crops throughout the Central Valley based on a mass balance approach. However, research is lacking to infer nitrogen loading rates for the broad diversity of crop and land-use types directly from groundwater nitrate measurements. Relating groundwater nitrate measurements to specific crops must account for the uncertainty about and multiplicity in contributing crops (and other land uses) to individual well measurements, and for the variability of nitrogen loading within farms and from farm to farm for the same crop type. In this study, we developed a Bayesian regression model that allowed us to estimate land-use-specific groundwater nitrogen loading rate probability distributions for 15 crop and land-use groups based on a database of recent nitrate measurements from 2149 private wells in the Central Valley. The water and natural, rice, and alfalfa and pasture groups had the lowest median estimated nitrogen loading rates, each with a median estimate below 5 kg N ha−1 yr−1. Confined animal feeding operations (dairies) and citrus and subtropical crops had the greatest median estimated nitrogen loading rates at approximately 269 and 65 kg N ha−1 yr−1, respectively. In general, our probability-based estimates compare favorably with previous direct measurements and with mass-balance-based estimates of nitrogen loading. Nitrogen mass-balance-based estimates are larger than our groundwater nitrate derived estimates for manured and nonmanured forage, nuts, cotton, tree fruit, and rice crops. These discrepancies are thought to be due to groundwater age mixing, dilution from infiltrating river water, or denitrification between the time when nitrogen leaves the root zone (point of reference for mass-balance-derived loading) and the time and location of groundwater measurement.

scholarly journals A Bayesian Approach to Infer Nitrogen Loading Rates from Crop and Landuse Types Surrounding Private Wells in the Central Valley, California

2018 ◽  
Author(s):  
Katherine M. Ransom ◽  
Andrew M. Bell ◽  
Quinn E. Barber ◽  
George Kourakos ◽  
Thomas Harter
Keyword(s):  
Mass Balance ◽  
Root Zone ◽  
Groundwater Age ◽  
Central Valley ◽  
Nitrogen Loading ◽  
Bayesian Regression ◽  
Agricultural Crop ◽  
Forage Crops ◽  
Loading Rates ◽  
Private Wells

Abstract. This study is focused on nitrogen loading from a wide variety of crop and landuse types in the Central Valley, California, USA, an intensively farmed region with high agricultural crop diversity. Nitrogen loading rates for several crop types have been measured based on field scale experiments and recent research has calculated nitrogen loading rates for crops throughout the Central Valley based on a mass balance approach. However, research is lacking to infer nitrogen loading rates for the broad diversity of crop and landuse types directly from groundwater nitrate measurements. Relating groundwater nitrate measurements to specific crops must account for the uncertainty about and multiplicity in contributing crops (and other landuses) to individual well measurements, and also for the variability of nitrogen loading within farms and from farm to farm for the same crop. In this study, we developed a Bayesian regression model that allowed us to estimate crop or other landuse-specific groundwater nitrogen loading rate probability distributions for 15 crop and landuse groups based on a database of recent nitrate measurements from 2149 private wells in the Central Valley. The water & natural, rice, and alfalfa & pasture groups had the lowest median estimated nitrogen loading rates, each with a median estimate below 5 kg N ha−1 yr−1. Confined animal feeding operations (dairies) and citrus & subtropical crops had the greatest median estimated nitrogen loading rates at approximately 269 and 65 kg N ha−1 yr−1, respectively. In general, our probability based estimates compare favorably with previous direct measurements and with mass balance based estimates of nitrogen loading. Nitrogen mass balance based estimates are larger than our groundwater nitrate derived estimates for manured forage crops, nuts, cotton, tree fruit, and rice crops. These discrepancies are thought to be due to groundwater age mixing, dilution from infiltrating river water, or denitrification between the time when nitrogen leaves the root zone (point of reference for mass balance derived loading) and the time and location of groundwater measurement.

EFFECT OF LOADING RATE ON FRACTURE BEHAVIOUR OF Mg-Al-Zn ALLOYS

2016 ◽  
Vol 78 (6-9) ◽  
Author(s):  
Noradila Abdul Latif ◽  
Zainuddin Sajuri ◽  
Junaidi Syarif ◽  
Yukio Miyashita
Keyword(s):  
Magnesium Alloys ◽  
Large Scale ◽  
Loading Rate ◽  
Fracture Behaviour ◽  
Maximum Load ◽  
Loading Rates ◽  
Specific Strength ◽  
Scale Yielding ◽  
The Impact ◽  
Zn Alloys

In recent years, magnesium alloys are widely used for automotive applications as structural components due to its lightweight property and high specific strength. In this regards, magnesium alloys are subjected to high velocity and impact loads during accident. Hence, understanding the impact and dynamic behaviours of magnesium alloys are essential. In this study, the effect of loading rates on the fracture behaviour of Mg-Al-Zn alloys was investigated using pre-cracked single-edge notched bending (SENB) specimens. Three-point bending tests were conducted at different loading rates of 5, 50 and 500 mm/min. The Mg-Al-Zn alloys that used in the present study were extruded AZ31 and AZ61 magnesium alloys. From the load-load line displacement results, both alloys exhibited nonlinear fracture behaviour. The maximum load (Pmax) of these two alloys increased with increasing loading rate. Comparing both alloys, AZ61 exhibited higher Pmax than that of AZ31 due to the higher volume of b-phase and smaller grain size in AZ61. Fracture surface observation revealed that both alloys fractured in ductile manner with large scale yielding and high shear lips ratio at all loading rates.

Loading Rate Effect Investigation of Through-Hole-Mounted Solder Joints

2005 ◽  
Author(s):  
Frank Z. Liang ◽  
Larry M. Palanuk ◽  
Mike Gabriel
Keyword(s):  
Solder Joint ◽  
High Speed ◽  
Loading Rate ◽  
High Loading ◽  
Static Tests ◽  
Loading Rates ◽  
Wide Range ◽  
Load To Failure ◽  
The Impact ◽  
Through Hole

This paper presents two simple and unique tests to extract shock-level loading limits for eutectic and lead free solders. A wide range of loading rates, from quasi-static to high speed, was applied to a through-hole-mounted anchor assembly test coupon. The high speed shock tests were conducted on a drop shock table where the impacting velocities were derived through table input adjustments. The quasi-static tests were done using controlled hydraulic linear actuator with a load cell. As would be assumed, the dynamic load to cause solder joint failure was found to increase with higher loading rate. However, at such a high loading rate range, the impact velocity did not change the load to failure. This study leads to an interesting hypothesis that at high loading rates, the solder joint strain rate may not see a significant change as observed at low rates.

scholarly journals High resolution modeling of agricultural nitrogen to identify private wells susceptible to nitrate contamination

2014 ◽  
Vol 12 (4) ◽  
pp. 702-714 ◽  
Author(s):  
Brendalynn Hoppe ◽  
Denis White ◽  
Anna Harding ◽  
George Mueller-Warrant ◽  
Bruce Hope ◽  
...  
Keyword(s):  
High Resolution ◽  
Rural Areas ◽  
Nutrient Loading ◽  
Nitrogen Loading ◽  
Nitrate Contamination ◽  
Water Safety ◽  
Animal Feeding Operations ◽  
Agricultural Enterprise ◽  
Nitrogen Inputs ◽  
Private Wells

Given the lack of data on private wells, public health and water quality specialists must explore alternative datasets for understanding associated exposures and health risks. Characterizing agricultural nitrogen inputs would be valuable for identifying areas where well water safety may be compromised. This study incorporated existing methods for estimating nutrient loading at the county level with datasets derived from a state permitting program for confined animal feeding operations and agricultural enterprise budget worksheets to produce a high resolution agricultural nitrogen raster map. This map was combined with data on soil leachability and new well locations. An algorithm was developed to calculate nitrogen loading and leachability within 1,000 meters of each well. Wells with a nonzero nitrogen total linked to soils with high leachability were categorized and displayed on maps communicating well susceptibility across the state of Oregon. Results suggest that 4% of recently drilled wells may be susceptible to nitrate contamination, while areas identified for mitigation are too restrictive to include all susceptible wells. Predicted increases in population density and the steady addition of approximately 3,800 new wells annually may lead to a large number of residents, especially those in rural areas, experiencing long-term exposures to nitrate in drinking water.

Evaluating the effects of nitrogen loading rate and substrate inhibitions on partial nitrification with FISH analysis

2012 ◽  
Vol 65 (3) ◽  
pp. 513-518 ◽  
Author(s):  
Liang Zhang ◽  
Shujun Zhang ◽  
Xiaoyu Han ◽  
Yiping Gan ◽  
Chengcheng Wu ◽  
...  
Keyword(s):  
Loading Rate ◽  
Substrate Inhibition ◽  
Nitrogen Loading ◽  
Partial Nitrification ◽  
Fish Analysis ◽  
Free Nitrous Acid ◽  
Reject Water ◽  
Denitrification Reactor ◽  
The Stability ◽  
The Impact

The effects of free ammonia (FA) or free nitrous acid (FNA) on partial nitrification (PN) has been well investigated. Nevertheless, little information was known about the combined effects of nitrogen loading rate (NLR) and substrate inhibition, as well as the impact on the community structure of nitrifiers. In this work, real reject water was treated in a pre-denitrification reactor. PN was achieved by gradually increasing NLR, and it was successfully maintained when average FA and FNA were within 0.8–3.2 mg NH3-N/L and 0.003–0.067 mg HNO2-N/L, respectively. When NLR was reduced, PN was slightly affected due to the FA declination. As FNA inhibition was also eliminated by adding alkalinity into the influent, PN was completely destroyed quickly. FISH results indicated the deterioration of the PN was mainly attributed to the recovery of NOB when inhibition effects were limited. It concluded the increase of NLR benefited the partial nitrification. However, the stability of the nitrite path way was more dependent on selective substrate inhibition effects, especially the FNA inhibition. These findings would be important for further treatment of actual reject water.

Asteroid and Comet Impact Speeds upon Mars: Significance for Panspermia and the Supply of Organics

1997 ◽  
Vol 161 ◽  
pp. 197-201 ◽  
Author(s):  
Duncan Steel
Keyword(s):  
Probability Distributions ◽  
Regions Of Interest ◽  
Significant Fraction ◽  
Organic Chemicals ◽  
Impact Speed ◽  
The Mean ◽  
The Impact

AbstractWhilst lithopanspermia depends upon massive impacts occurring at a speed above some limit, the intact delivery of organic chemicals or other volatiles to a planet requires the impact speed to be below some other limit such that a significant fraction of that material escapes destruction. Thus the two opposite ends of the impact speed distributions are the regions of interest in the bioastronomical context, whereas much modelling work on impacts delivers, or makes use of, only the mean speed. Here the probability distributions of impact speeds upon Mars are calculated for (i) the orbital distribution of known asteroids; and (ii) the expected distribution of near-parabolic cometary orbits. It is found that cometary impacts are far more likely to eject rocks from Mars (over 99 percent of the cometary impacts are at speeds above 20 km/sec, but at most 5 percent of the asteroidal impacts); paradoxically, the objects impacting at speeds low enough to make organic/volatile survival possible (the asteroids) are those which are depleted in such species.

Factors affecting phosphorus removal in two biofilter system treating wastewater from car-washing facility

2000 ◽  
Vol 41 (4-5) ◽  
pp. 487-492 ◽  
Author(s):  
D. Pak ◽  
W. Chang
Keyword(s):  
Phosphorus Removal ◽  
Phosphorus Content ◽  
Hydraulic Retention Time ◽  
Loading Rate ◽  
Aerobic Condition ◽  
Suspended Solid ◽  
Nitrogen Loading ◽  
Operational Parameters ◽  
Factors Affecting ◽  
Biological Filter

A two-biofilter system operated under alternating anaerobic/aerobic conditions was tested to remove nutrient as well as organics from wastewater generated from car-washing facility. The wastewater was characterized by relatively low organic and high phosphorus content. The factors affecting phosphorus removal in the two-biofilter system were investigated. Operational parameters examined in this study were hydraulic retention time, organic, suspended solid and nitrogen loading rate. The factors affecting phosphorus removal in biological filter appeared to be influent COD, COD/T–P, BOD/COD, nitrogen, and SS/T–P. Nitrite and nitrate produced in the biofilter in aerobic condition affected phosphorus removal by the two-biofilter system. The biomass wasted during backwash procedure also affected total phosphorus removal by the system.

scholarly journals Evaluating Forest Cover and Fragmentation in Costa Rica with a Corrected Global Tree Cover Map

2020 ◽  
Vol 12 (19) ◽  
pp. 3226
Author(s):  
Daniel Cunningham ◽  
Paul Cunningham ◽  
Matthew E. Fagan
Keyword(s):  
Costa Rica ◽  
Forest Cover ◽  
Agricultural Land ◽  
Forest Area ◽  
Tree Cover ◽  
Agricultural Crop ◽  
Forest Change ◽  
Alos Palsar ◽  
Tropical Regions ◽  
The Impact

Global tree cover products face challenges in accurately predicting tree cover across biophysical gradients, such as precipitation or agricultural cover. To generate a natural forest cover map for Costa Rica, biases in tree cover estimation in the most widely used tree cover product (the Global Forest Change product (GFC) were quantified and corrected, and the impact of map biases on estimates of forest cover and fragmentation was examined. First, a forest reference dataset was developed to examine how the difference between reference and GFC-predicted tree cover estimates varied along gradients of precipitation and elevation, and nonlinear statistical models were fit to predict the bias. Next, an agricultural land cover map was generated by classifying Landsat and ALOS PalSAR imagery (overall accuracy of 97%) to allow removing six common agricultural crops from estimates of tree cover. Finally, the GFC product was corrected through an integrated process using the nonlinear predictions of precipitation and elevation biases and the agricultural crop map as inputs. The accuracy of tree cover prediction increased by ≈29% over the original global forest change product (the R2 rose from 0.416 to 0.538). Using an optimized 89% tree cover threshold to create a forest/nonforest map, we found that fragmentation declined and core forest area and connectivity increased in the corrected forest cover map, especially in dry tropical forests, protected areas, and designated habitat corridors. By contrast, the core forest area decreased locally where agricultural fields were removed from estimates of natural tree cover. This research demonstrates a simple, transferable methodology to correct for observed biases in the Global Forest Change product. The use of uncorrected tree cover products may markedly over- or underestimate forest cover and fragmentation, especially in tropical regions with low precipitation, significant topography, and/or perennial agricultural production.

scholarly journals Does Resisted Sled Towing Improve the Physical Qualities of Elite Youth Soccer Players of Differing Maturity Status?

2021 ◽  
Author(s):  
Rhys Morris ◽  
Tony Myers ◽  
Stacey Emmonds ◽  
Dave Singleton ◽  
Kevin Till
Keyword(s):  
Body Mass ◽  
Bayesian Regression ◽  
Soccer Players ◽  
Height Velocity ◽  
Regression To The Mean ◽  
Peak Height Velocity ◽  
Maturity Group ◽  
Youth Soccer ◽  
Professional Soccer ◽  
The Impact

Abstract Purpose Sled towing has been shown to be an effective method to enhance the physical qualities in youth athletes. The aim of this study was to evaluate the impact of a 6-week sled towing intervention on muscular strength, speed and power in elite youth soccer players of differing maturity status. Method Seventy-three male elite youth soccer players aged 12–18 years (Pre-Peak Height Velocity [PHV] n = 25; Circa-PHV n = 24; Post-PHV n = 24) from one professional soccer academy participated in this study. Sprint assessments (10 m and 30 m), countermovement jump and isometric mid-thigh pull were undertaken before (T1) and after (T2) a 6-week intervention. The training intervention consisted of 6 weeks (2 × per week, 10 sprints over 20 m distance) of resisted sled towing (linear progression 10%–30% of body mass) during the competitive season. Bayesian regression models analysed differences between T1 and T2 within each maturity group. Results There were minimal changes in strength, speed and power (P = 0.35–0.80) for each maturity group across the 6-week intervention. Where there were changes with greater certainty, they are unlikely to represent real effect due to higher regression to the mean (RTM). Conclusion It appears that a 6-week sled towing training programme with loadings of 10%–30% body mass only maintains physical qualities in elite youth soccer players pre-, circa-, and post-PHV. Further research is required to determine the effectiveness of this training method in long-term athletic development programmes.

Sign in / Sign up

Export Citation Format

Share Document