Several inland water bodies in the St. Louis Bay watershed have been identified as being potentially impaired due to low level of dissolved oxygen (DO). In order to calculate the total maximum daily ...loads (TMDL), a standard watershed model supported by U.S. Environmental Protection Agency, Hydrological Simulation Program Fortran (HSPF), was used to simulate water temperature, DO, and bio-chemical oxygen demand (BOD). Both point and non-point sources of BOD were included in watershed modeling. The developed model was calibrated at two time periods: 1978 to 1986 and 2000 to 2001 with simulated DO closely matched the observed data and captured the seasonal variations. The model represented the general trend and average condition of observed BOD. Water temperature and BOD decay are the major factors that affect DO simulation, whereas nutrient processes, including nitrification, denitrification, and phytoplankton cycle, have slight impacts. The calibrated water quality model provides a representative linkage between the sources of BOD and in-stream DO\BOD concentrations. The developed input parameters in this research could be extended to similar coastal watersheds for TMDL determination and Best Management Practice (BMP) evaluation.
Understanding pollutant sorption, bioremediation of these pollutants, and their interactions with humic substances requires knowledge of molecular-level processes. New developments with nuclear ...magnetic resonance (NMR) experiments and labeled compounds have improved the overall understanding of these mechanisms. The advancements made with two-dimensional NMR show great promise, as structural information and hydrogen-carbon bond connectivity can be discerned. This communication presents the application of improved two-dimensional NMR methods, the double quantum filtered (DQF) correlation spectroscopy (COSY) and echo/anti-echo heteronuclear single quantum coherence (HSQC) experiments, for use in structural studies of humic substances. Both experiments were found to produce significant improvements over the conventional COSY and heteronuclear multiple quantum coherence (HMQC) experiments that have been previously employed in similar studies. The more sensitive echo/anti-echo HSQC experiment produced more cross-peaks with higher resolution when compared with the HMQC spectra. The DQF-COSY significantly suppressed the diagonal signals and allowed numerous signals previously hidden in the standard COSY experiment to be observed. These improvements will aid current characterization strategies of humic substances from soils, sediments, and water and their subsequent reactions with pollutants and microorganisms.
In 1998 and 1999, two soil series representative of a large percentage of rice (Oryza sativa L.) growing hectarage in the Mississippi Delta were sampled in increments to a depth of 120 cm. ...Measurements were made to determine how extractable levels of Ca, K, Mg, Na, P, and Zn as well as the total N content and soil pH varied with respect to soil profile depth. Total N, extractable P, Zn, Ca, and pH all tended to decrease with depth while Na tended to increase. Only small differences were seen in Mg and K concentrations. An on-farm study was conducted in 2000 and 2001 to further investigate the effects of precision land leveling on pH and concentrations of organic matter and extractable nutrients. This study was conducted on seven farms, all of which possessed yield monitor-equipped combines. Field elevation sheets and GPS/GIS technologies were utilized to investigate soil nutrient and yield data for areas of cut and fill at each location. Yields were lower in the cut areas than the fill areas on five of the seven fields. Results from the soil nutrient data were similar to those findings in 1998 and 1999. A nutrient deficiency was apparent in only one of the five fields where yields were reduced. However, the percentage yield loss in the cut areas compared with the fill areas was directly proportional to the volume of soil moved per hectare during the precision land-leveling process (r2 = 0.78). This research indicates that yields can be reduced after precision land leveling in many soil types, but the reduction may or may not be nutrient related.
Nuclear magnetic resonance (NMR) microimaging is a noninvasive and nondestructive technique that has great potential for the study of soil processes. Hydrogen‐1 NMR microimaging techniques were used ...to examine the distribution of water in four different soil cores. Fluorine‐19 NMR microimaging is also used to study the transport of three model contaminants (hexafluorobenzene, sodium fluoride, and trifluralin) in soil columns. The 1H water distribution studies demonstrate that NMR microimaging can provide unique detail regarding the nature and location of water in soils. Image distortion (magnetic susceptibility) was observed for soil samples low in water (20–28% by weight) and that contained an iron content of 0.73 to 0.99%. Highly resolved images were obtained for the organic‐rich soil (Croatan sample) and also facilitated the analysis of bound and unbound soil water through varying spin echo times. The contaminant studies with 19F NMR demonstrated that preferential flow processes can be observed in soil cores in as little as 16 h. Studies with hexafluorobenzene produced the highest quality images whereas the definition decreased over time with both trifluralin and sodium fluoride as the compounds penetrated the soil. Nonetheless, both 1H and 19F NMR microimaging techniques demonstrate great promise for studying soil processes.
The objective of this research is to investigate the effects of long-term broiler litter application on soil phosphorus (P) and water quality and examine the spatial variations of soil P at a private ...poultry farm in Mississippi. Results indicated that the littered soil had 86 times more Mehlich III-extractable P in the surface horizon compared to the nonlittered soil. When compared to the runoff from nonlittered soil, mean soluble phosphate (PO4)-P concentrations in the littered soil's runoff were 85 times greater throughout the study. Mass loss of P from the littered field was significantly greater than from the nonlittered field, and it decreased with each sequential runoff event. There were no linear relationships between the spatial variations of litter application rates and the P spatial variability in the littered soil; however, the variations in soil P levels could be a result of the cumulative effects of more than 20 years of litter application.
This study performs a comparison of two nutrient algorithms of Hydrological Simulation Program Fortran, PQUAL/IQUAL and AGCHEM. Watershed nutrient models with, PQUAL/IQUAL and AGCHEM, were developed ...and calibrated separately with observed data in the Wolf River watershed. Compared to AGCHEM modules, the PQUAL/IQUAL algorithm was found to have several disadvantages. Examples are: (i) it is a simple loading estimation algorithm, and cannot represent the soil nutrient processes; and (ii) the interactions of modeled nutrient species in the soil cannot be simulated. The AGCHEM modules are capable of explicitly representing the comprehensive nutrient processes in the soil such as fertilization, atmospheric deposition, manure application, plant uptake process, and the transformation processes. Therefore, AGCHEM modules afford the ability to evaluate the alternative management practice and model the interactions between nutrient species. However, our modeling results indicated that the inclusion of AGCHEM modules do not significantly improve the nutrient modeling performance but rather take much more time in model development. The nutrient algorithms selection for total maximum daily loads development depends on the data availability, required modeling accuracy, and available time for model development.
Assessment of water quality conditions in the St. Louis Bay watershed Liu, Zhijun; Kingery, William L.; Huddleston, David H. ...
Journal of environmental science and health. Part A, Toxic/hazardous substances & environmental engineering,
04/2008, Volume:
43, Issue:
5
Journal Article
Peer reviewed
The water quality data from 14 sampling stations in the St. Louis Bay watershed were analyzed to evaluate the water quality conditions. The differences in water quality parameters between base and ...storm flow events were compared to identify the pollutant sources. The results indicated that fecal coliform was the primary cause for water quality impairment of the study area. The overall water quality conditions were good in terms of dissolved oxygen, eutrophication, and total suspended solid (TSS). The dominant sources of bio-chemical oxygen demand (BOD) could be from the failing septic system; the majority of the water samples exceeding Mississippi Department of Environmental Quality (MDEQ) target levels were from base flow events. Different from BOD, the majority of the water samples exceeding the water quality criteria and MDEQ target levels were from the storm events for fecal coliform, chemical oxygen demand, total organic carbon, TKN, NO
3
, NH
3
, chlorophyll a, and TSS. Based on cluster analysis, the sampling stations were classified into two major categories: upstream and near-coast stations. The major differences between upstream and near-coast stations are elevation, soil texture, and impacts of human activity. The results from this research would provide useful information for total maximum daily load calculation, development of a computational watershed model, and development of best management practices for the St. Louis Bay watershed and similar study area.
Site 22LI504 is a predominantly Archaic period site in Lincoln County, Mississippi. One of its primary elements of interest is a single conical mound from which small-diameter cores revealed evidence ...of advanced pedogenesis. A radiocarbon sample from one soil core produced a date suggesting that the mound was Archaic in age (Fulmer 2001); however, it was unclear whether the sample came from within the mound or an underlying midden. In the spring of 2006, we excavated a 1-x-1-m unit in the mound to investigate this question. Diagnostic lithic artifacts, an advanced state of soil horizonation, and a lack of ceramics indicate that the mound is of Archaic period construction, with as many as five construction stages and artifact-rich features. We describe the soil profiles, features, and artifacts recovered from the mound, with comparisons to excavation units in an adjacent Archaic midden to show that there is no clear evidence for the mound being a functionally specific locus. We also present radiocarbon dates that indicate the earthwork is over 5,000 years old. These results are evaluated within the broader context of Archaic mound building, focusing in particular on environmental parameters underlying bet-hedging behavior.
Previous research results indicated that dry weather condition has complicated impacts on nitrogen dynamics; monitored and modeling data showed both increased and decreased levels. In order to ...facilitate the total maximum daily loads (TMDLs) development at three tributaries of St. Louis Bay estuary, the nitrogen dynamics were investigated for two designed critical flow conditions by integrating Hydrological Simulation Program Fortran (HSPF), Environmental Fluid Dynamics Code (EFDC), and Water Quality Analysis Simulation Program (WASP). The total amount of precipitation during the dry year corresponded to a flow condition with return period of 50 years, and 10-year return period for wet year. The dry year contributed more total nitrogen (TN) loads per unit flow volume. At the upstream tributaries, the computed peak reach-averaged TN concentrations were significantly higher for dry weather simulation than wet conditions, whereas at the near-bay tributary, there were no significant differences in the peak TN concentrations. Hence, for the upstream tributaries, the nitrogen TMDL calculation should be based on dry weather condition since the decision-makers are more concerned about the worse scenario.
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