bluuebunny/crossref_metadata_2025_split huggingface dataset:
Soil Chemical Changes under Irrigated Mango Production in the Central São Francisco River Valley, Brazil
Authors: Heck R. J. , Tiessen H. , Salcedo I. H. , Santos M. C. 
Published: June 2010

ABSTRACTIrrigated areas in Brazil's Central São Francisco River Valley have experienced declines in productivity, which may be a reflection of changes in soil chemical properties due to management. This study was conducted to compare the chemical composition of soil solutions and cation exchange complexes in a five‐year‐old grove of irrigated mango (Mangifera indica L. cv. Tommy Atkins) with that of an adjacent clearing in the native caatinga vegetation. A detailed physiographic characterization of the area revealed a subsurface rock layer, which was more undulating than the current land surface, and identified the presence of a very saline and sodic (1045 μS cm−1, sodium adsorption ratio [SAR] = 5.19) ground water table. While changes in concentrations of Ca, Mg, and K could be attributed to direct management inputs (fertilization and liming with dolomite), increases in Na suggested average annual capillary rise from the ground water table of 28 L m−2 Accordingly, soil salinity levels appeared to be more dependent on surface elevation than the elevation of the rock layer or sediment thickness. The apparent influence of land surface curvature on water redistribution and the solution chemistry was more pronounced under irrigated mango production. In general, salinity levels had doubled in the mango grove and nearly tripled under the canopies, after only five years of irrigation. Though critical saline or sodic conditions were not encountered, the changes observed indicate a need for more adequate monitoring and management of water and salt inputs despite the excellent water quality of the São Francisco River.
Electron Affinity Coefficients of Nitrogen Oxides and Biodegradation Kinetics in Denitrification of Contaminated Stream Water
Authors: Kim Seung‐Hyun , Chung Jong‐Bae , Jeong Byeong‐Ryong , Lee Young‐Deuk , Prasher Shiv O. 
Published: June 2010

ABSTRACTDuring the dry season in Korea, rivers become more vulnerable to contamination by biochemical oxygen demand (BOD) and nitrogen. It is hypothesized that the natural characteristics of the streams in Korea allow the contaminated water to be treated at the tributaries. Downstream river water quality in Korea may be improved by spraying the contaminated stream water from the tributaries over the surrounding floodplains. The consequent water filtration through the soil could remove the contaminants through aerobic and denitrifying reactions. In this study, the kinetics parameters of the denitrifying reaction in floodplain filtration were determined using contaminated stream water. For the electron donor the Monod kinetics was used, while the competitive Michaelis–Menten model was employed for the electron acceptors. The parameters to the competitive Michaelis–Menten model were found using continuous denitrifying reactions, instead of the batch reactions employed in previous studies, to match the conditions needed to apply the competitive Michaelis–Menten kinetics. From the result, it was found that continuous reactions as well as batch reactions could be used to determine the affinity coefficients in denitrification. The results of this study also showed that the affinity coefficient of NO−2, using continuous reactions, was similar to that of other studies in the literature found via batch reactions, whereas the affinity coefficient of N2O was much larger than that acquired with batch reactions. The parameters obtained in this study will be used in future work to simulate the contaminant behaviors during floodplain filtration using a mathematical model.
Phytase, High‐Available‐Phosphorus Corn, and Storage Effects on Phosphorus Levels in Pig Excreta
Authors: Baxter Christopher A. , Joern Brad C. , Ragland Darryl , Sands Jason S. , Adeola Olayiwola 
Published: June 2010

ABSTRACTPhosphorus‐based land application limits for manure have increased the importance of optimizing diet P management and accurately characterizing the bioavailability of manure P. We examined the effects of pig (Sus scrofa) diets formulated with high‐available‐P corn and phytase on P levels in excreta and slurry stored for 30, 60, 90, 120, and 150 d. Twenty‐four pigs (approximately 14 kg each) were fed one of four low‐P diets: (i) normal corn, no phytase (control); (ii) normal corn with 600 phytase units kg−1 (PHY); (iii) high‐available‐P corn, no phytase (HAP); and (iv) high‐available‐P corn with 600 phytase units kg−1 (HAP + PHY). Fresh fecal and stored slurry dry matter (DM) was analyzed for total phosphorus (TP), dissolved molybdate‐reactive phosphorus (DRP), dissolved organic phosphorus (DOP), acid‐soluble reactive phosphorus (ASRP), acid‐soluble organic phosphorus (ASOP), and phytate phosphorus (PAP). The PHY, HAP, and HAP + PHY diets significantly (α = 0.05) decreased fecal TP 19, 17, and 40%, respectively, compared with the control. Dissolved reactive P was 36% lower in the HAP + PHY diet compared with the other diets. Relative fractions (percent of TP) of DRP, DOP, ASOP, and PAP in slurry generally decreased with storage time up to 150 d, with the largest decreases occurring within 60 to 90 d. Diet‐induced differences in relative fractions of DRP, DOP, ASRP, and PAP were significant when averaged across storage times, simulating a mixed‐age slurry. Relative fractions of DRP in simulated mixed‐age slurries were higher in HAP and HAP + PHY diets, indicating that diet may affect P losses under certain P‐based application scenarios.
Decomposition and Plant‐Available Nitrogen in Biosolids
Authors: Gilmour John T. , Cogger Craig G. , Jacobs Lee W. , Evanylo Gregory K. , Sullivan Dan M. 
Published: June 2010

ABSTRACTThis research combines laboratory and field studies with computer simulation to characterize the amount of plant‐available nitrogen (PAN) released when municipal biosolids are land‐applied to agronomic crops. In the laboratory studies, biosolids were incubated in or on soil from the land application sites. Mean biosolids total C, organic N, and C to N ratio were 292 g kg−1, 41.7 g kg−1, and 7.5, respectively. Based on CO2 evolution at 25°C and optimum soil moisture, 27 of the 37 biosolids–soil combinations had two decomposition phases. The mean rapid and slow fraction rate constants were 0.021 and 0.0015 d−1, respectively, and the rapid fraction contained 23% of the total C assuming sequential decomposition. Where only one decomposition phase existed, the mean first order rate constant was 0.0046 d−1 The mean rate constant for biosolids stored in lagoons for an extended time was 0.00097 d−1 The only treatment process that was related to biosolids treatment was stabilization by storage in a lagoon. Biosolids addition rates (dry basis) ranged from 1.3 to 33.8 Mg ha−1 with a mean value of 10.6 Mg ha−1 A relationship between fertilizer N rate and crop response was used to estimate observed PAN at each site. Mean observed PAN during the growing season was 18.9 kg N Mg−1 or 37% of the biosolids total N. Observed PAN was linearly related to biosolids total N. Predicted PAN using the computer model Decomposition, actual growing‐season weather, actual analytical data, and laboratory decomposition kinetics compared well with observed PAN. The mean computer model prediction of growing‐season PAN was 19.2 kg N Mg−1 and the slope of the regression between predicted and observed PAN was not significantly different from unity. Predicted PAN obtained using mean decomposition kinetics was related to predicted PAN using actual decomposition kinetics suggesting that mean rate constants, actual weather, and actual analytical data could be used in estimation of PAN. There was a linear relationship between predicted N mineralization for the growing season and for the first year. For this study, the mean values for the growing season and year were 27 and 37% of the organic N, respectively.
Characterization of Sewage Sludge Organic Matter Using Solid‐State Carbon‐13 Nuclear Magnetic Resonance Spectroscopy
Authors: Smernik Ronald J. , Oliver Ian W. , Merrington Graham 
Published: June 2010

ABSTRACTSix sewage sludges from five sewage treatment plants in Australia were characterized using solid‐state 13C nuclear magnetic resonance (NMR) spectroscopy. Spectra were acquired both before and after removal of mineral components through treatment with hydrofluoric acid (HF). Carbon mass balance indicated that little organic matter was lost on HF treatment, which significantly improved NMR sensitivity and spectral resolution, and decreased acquisition time and hence cost of NMR analysis. Two NMR techniques were used, the standard cross polarization (CP) technique and Bloch decay (BD). The BD technique had not been applied previously to the analysis of sewage sludge. For each sludge sample, both before and after HF treatment, the BD spectrum contained significantly more alkyl carbon. Spin counting, another technique applied to sewage sludge here for the first time, showed that the BD spectra of the HF‐treated sludges were quantitative, while approximately 30% of the CP NMR signal went undetected. The discrepancy between CP and BD spectra was attributed to the presence of alkyl carbon with such high molecular mobility that the efficiency of cross polarization is affected. This study shows that sewage sludge organic matter is significantly different in chemistry to soil organic matter and has implications for the application of sewage sludge to agricultural land.
Pesticide Removal from Container Nursery Runoff in Constructed Wetland Cells
Authors: Stearman G. Kim , George Dennis B. , Carlson Kris , Lansford Stacey 
Published: June 2010

ABSTRACTThe increased use of pesticides by container nurseries demands that practices for removal of these potential contaminants from runoff water be examined. Constructed wetlands may be designed to clean runoff water from agricultural production sites, including container nurseries. This study evaluated 14 constructed wetlands cells (1.2 by 4.9 m or 2.4 by 4.9 m, and 30 or 45 cm deep) that collected pesticide runoff from a 465‐m2 gravel bed containerized nursery in Baxter, TN. One‐half of the cells were vegetated with bulrush, Scirpus validus The cells were loaded at three rates or flows of 0.240, 0.120, and 0.060 m3 d−1 Herbicides—simazine (Princep) [2‐chloro‐4,6‐bis(ethylamino)‐s‐triazine] and metolachlor (Pennant) [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐2‐methoxy‐1‐methylethyl‐acetamide]—were applied to the gravel portion of the container nursery at rates of 4.78 and 2.39 kg ha−1, respectively, 9 July 1998, and at rates of 2.39 and 1.19 kg ha−1, respectively, 17 May 1999. Pesticides entering the wetland and wetland cell water samples were analyzed daily to determine pesticide removal. At the slower flow rate, which corresponds to lower mass loading and greater hydraulic retention times (HRTs), a greater percentage of pesticides was removed. During the 2‐yr period, cells with plants removed 82.4% metolachlor and 77.1% simazine compared with cells without plants, which removed 63.2% metolachlor and 64.3% simazine. At the lowest flow rate and mass loading, wetland cells removed 90.2% metolachlor and 83% simazine. Gravel subsurface flow constructed wetlands removed most of the pesticides in runoff water with the greatest removal occurring at lower flow rates in vegetated cells.
Selenium Removal and Mass Balance in a Constructed Flow‐Through Wetland System
Authors: Gao S. , Tanji K. K. , Lin Z. Q. , Terry N. , Peters D. W. 
Published: June 2010

ABSTRACTA field study on the removal of Se from agricultural subsurface drainage was conducted from May 1997 to February 2001 in the Tulare Lake Drainage District (TLDD) of San Joaquin Valley, California. A flow‐through wetland system was constructed consisting of ten 15‐ × 76‐m unlined cells that were continuously flooded and planted with either a monotype or combination of plants, including sturdy bulrush [Schoenoplectus robustus(Pursh) M.T. Strong], baltic rush (Juncus balticusWilld.), smooth cordgrass (Spartina alternifloraLoisel.), rabbitsfoot grass [Polypogon monspeliensis(L.) Desf.], saltgrass [Distichlis spicata(L.) Greene], cattail (Typha latifoliaL.), tule [Schoenoplectus acutus(Muhl. ex Bigelow) Á. Löve & D. Löve], and widgeon grass (Ruppia maritimaL.). One cell had no vegetation planted. The objectives of this research were to evaluate Se removal efficiency of each wetland cell and to carry out a mass balance on Se. The inflow drainage water to the cells had average annual Se concentrations of 19 to 22 μg L−1dominated by selenate [Se(VI), 95%]. Average weekly water residence time varied from about 3 to 15 d for Cells 1 through 7 (target 7 d), 19 to 33 d for Cells 8 and 9 (target 21 d), and 13 to 18 d for Cell 10 (target 14 d). Average weekly Se concentration ratios of outflow to inflow ranged from 0.45 to 0.79 and mass ratio (concentration × water volume) from 0.24 to 0.52 for year 2000, that is, 21 to 55% reduction in Se concentration and 48 to 76% Se removal in mass by the wetland, respectively. The nonvegetated cell showed the least Se removal both in concentration and in mass. The global mass balance showed that on the average about 59% of the total inflow Se was retained within the cells and Se outputs were outflow (35%), seepage (4%), and volatilization (2%). Independent measurements of the Se retained in the cells totaled 53% of the total Se inflow: 33% in the surface (0–20 cm) sediment, 18% in the organic detrital layer above the sediment, 2% in the fallen litter, <1% in the standing plants, and <1% in the surface water. Thus, about 6% of the total Se inflow was unaccounted for in the internal compartments.
The Capacity of Duckweed to Treat Wastewater
Authors: Körner Sabine , Vermaat Jan E. , Veenstra Siemen 
Published: June 2010

ABSTRACTDuckweed species are promising macrophytes for use in sustainable wastewater treatment due to their rapid growth, ease of harvest, and feed potential as a protein source. This paper reviews growth rates of different duckweed species on wastewater and ammonia toxicity to duckweed and summarizes insights into the mechanism of organic matter and nutrient removal. Results were gained from laboratory experiments in small, shallow, duckweed‐covered semicontinuous batch systems. Growth rates on different types of wastewater vary considerably among different species. Ammonia is toxic for duckweed in both the ionized and un‐ionized forms. Duckweed, however, can be used to treat wastewater containing very high total ammonia concentrations as long as certain pH levels are not exceeded. The degradation of organic material is enhanced by duckweed through both additional oxygen supply and additional surface for bacterial growth. The duckweed mat with attached bacteria and algae is, independent of the loading rates, responsible for three‐quarters of the total nitrogen (N) and phosphorus (P) loss in very shallow systems. Based on our results we suggest that full‐scale pilot plants with duckweed should be shallower than the range encountered in the literature. A harvesting schedule that allows doubling times of 2 to 3.5 d, maintenance of a full coverage, and plug flow conditions are recommended.
Atmospheric Deposition of Pesticides to an Agricultural Watershed of the Chesapeake Bay
Authors: Kuang Zhihua , McConnell Laura L. , Torrents Alba , Meritt Donald , Tobash Stephanie 
Published: June 2010

ABSTRACTThe Choptank River watershed, located on the Delmarva Peninsula of the Chesapeake Bay, is dominated by agricultural land use, which makes it vulnerable to runoff and atmospheric deposition of pesticides. Agricultural and wildlife areas are in close proximity and off‐site losses of pesticides may contribute to toxic effects on sensitive species of plants and animals. High‐volume air samples (n = 31) and event‐based rain samples (n = 71) were collected from a single location in the watershed representing regional background conditions. Surface water samples were collected from eight stations in the tidal portion of the river on five occasions during 2000. Chlorothalonil, metolachlor, atrazine, simazine, endosulfan, and chlorpyrifos were frequently detected in the air and rain, with maximal concentrations during the period when local or regional crops were planted. The wet deposition load to the watershed was estimated at 150 ± 16, 61 ± 7, and 51 ± 6 kg yr−1 for chlorothalonil, metolachlor, and atrazine, respectively. The high wet deposition load compared with the estimated annual usage for chlorothalonil (13%) and endosulfan (14–90%) suggests an atmospheric source from outside the watershed. Net air–water gas exchange fluxes for metolachlor varied from −44 ± 19 to 9.3 ± 4.1 ng m−2 d−1 with negative values indicating net deposition. Wet deposition accounted for 3 to 20% of the total metolachlor mass in the Choptank River and was a more important source to the river than gas exchange. Estimates of herbicide flux presented here are probably a low estimate and actual rates may be significantly higher in areas closer to pesticide application.
Spatial Distribution of DDT in Sediments from Estuarine Rivers of Central Florida
Authors: Ouyang Ying , Nkedi‐Kizza Peter , Mansell Robert S. , Ren Jim Y. 
Published: June 2010

ABSTRACTSediments may act as both a carrier for and a potential source of contaminants such as toxic organics in aquatic environments. This study investigated the spatial distribution of the pesticide DDT [1,1,1‐trichloro‐2,2‐bis(p‐chlorophenyl)ethane] in sediments from the Cedar and Ortega Rivers located in the lower St. Johns River basin, Florida, USA, using field measurements and three‐dimensional kriging analysis. High DDT concentrations were found near the junction of the Cedar and Ortega Rivers and at the north end of the Ortega River in the upper 0.5 m of the sediments, indicating that the sediment was enriched with DDT in the top layer although use of this chlorinated compound was banned in 1972. Further study revealed that the influence of sediment grain size or texture on DDT contamination was negligible in this river system and no linear correlations existed among DDT and its metabolites such as DDD [1,1‐dichloro‐2,2‐bis(p‐chlorophenyl)ethane] and DDE [1,1‐dichloro‐2,2‐bis(p‐chlorophenyl)ethylene]. Comparison of three‐dimensional distribution of DDT content to the Florida sediment quality assessment guideline or probable effect level (PEL) showed several “hot spots” in the Ortega River sediments, where DDT contents exceeded the PEL value of 4.78 μg kg−1 Such contamination may pose a significant hazard to aquatic life.
Competitive Degradation between the Fumigants Chloropicrin and 1,3‐Dichloropropene in Unamended and Amended Soils
Authors: Zheng Wei , Papiernik Sharon K. , Guo Minxing , Yates Scott R. 
Published: June 2010

ABSTRACTThe mixture of 1,3‐dichloropropene (1,3‐D) and chloropicrin (CP) is used as a preplant soil fumigant. In comparison with individual fumigants, application of a mixture may affect the environmental dissipation and fate of each chemical, such as emission and degradation. We investigated the degradation of CP, 1,3‐D, and their mixture in fresh soils and sterile soils, and evaluated the competitive characteristic of fumigants in the mixture. The degradation of low concentrations of CP in fresh soil was accelerated at early times in the presence of 1,3‐D, whereas the addition of CP reduced the degradation rate of trans‐1,3‐D, possibly by inhibiting the activity of trans‐1,3‐D degrading microorganisms. The potential of applying amendments to the soil to increase the rate of CP and 1,3‐D degradation was also illustrated. The degradation of both fumigants was significantly enhanced in soils amended with ammonium thiosulfate (ATS) and sodium diethyldithiocarbamate (Na‐DEDTC) compared with unamended soil. Competitive degradation was observed for CP in amended soils in the presence of 1,3‐D. The degradation of cis‐1,3‐D in amended soils spiked as a mixture of 1,3‐D and CP was repressed compared with the rate of degradation in samples spiked with 1,3‐D only. This implied that in abiotic degradation, CP and cis‐1,3‐D competed for a limited number of reaction sites in amended soil, resulting in decreased degradation rates. No significant influence of fumigant mixtures was observed for trans‐1,3‐D in amended soil.
Organic Manure and Urea Effect on Metolachlor Transport through Packed Soil Columns
Authors: Singh Neera 
Published: June 2010

ABSTRACTApplication of organic manure (OM) amendments and nitrogen fertilizers can affect the sorption and movement of pesticides in soil. This study summarizes the sorption and leaching of metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(2‐methoxy‐1‐methylphenyl)acetamide] in soils after cow (Bos taurus) manure (2.5 and 5.0%) and urea (60 and 120 kg N ha−1) amendments in batch and column experiments. Both cow manure and urea applications increased metolachlor sorption in soils. The values of the Freundlich adsorption parameter Kf(1/n) for treatments T0, T1 (OM), and T2 (OM) were 2.31, 3.32, and 3.96 in Soil 1; 2.02, 2.77, and 3.32 in Soil 2; and 1.10, 1.46, and 2.02 in Soil 3, respectively. Similarly, Kf(1/n) values for treatment T1 (urea) and T2 (urea) were 2.37 and 2.84 in Soil 1; 2.16 and 2.83 in Soil 2; and 1.50 and 1.70 in Soil 3, respectively. Column leaching studies using Soil 1 indicated that OM application drastically reduced the metolachlor leaching losses from 50% (natural soil) to <1.0% (5.0% OM amendment). Likewise, urea application also decreased metolachlor mobility and leaching losses in columns treated with 60 and 120 kg N ha−1 urea were 33 and 20%, respectively. The reduction in the metolachlor leaching losses was achieved through the increase in the sorption capability of the OM‐ and urea‐amended soil. Therefore, coapplication of metolachlor with cow manure or urea fertilizers will not enhance metolachlor mobility and reduces metolachlor leaching losses in low‐organic‐matter soil.
Stream Transport of Herbicides and Metabolites in a Tile‐Drained, Agricultural Watershed
Authors: David Mark B. , Gentry Lowell E. , Starks Karen M. , Cooke Richard A. 
Published: June 2010

ABSTRACTThe occurrence of metabolites of many commonly used herbicides in streams has not been studied extensively in tile‐drained watersheds. We collected water samples throughout the Upper Embarras River watershed [92% corn, Zea mays L., and soybean, Glycine max (L.) Merr.] in east‐central Illinois from March 1999 through September 2000 to study the occurrence of atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine), metolachlor [2‐chloro‐N‐(2‐ethyl‐6‐methylphenyl)‐N‐(methoxy‐1‐methylethyl) acetamide], alachlor [2‐chloro‐N‐(2,6‐diethylphenyl)‐N‐(methoxymethyl) acetamide], acetochlor [2‐chloro‐N‐(ethoxymethyl)‐N‐(2‐ethyl‐6‐methylphenyl) acetamide], and their metabolites. River water samples were collected from three subwatersheds of varying tile density (2.8–5.3 km tile km−2) and from the outlet (United States Geological Survey [USGS] gage site). Near‐record‐low totals for stream flow occurred during the study, and nearly all flow was from tiles. Concentrations of atrazine at the USGS gage site peaked at 15 and 17 μg L−1 in 1999 and 2000, respectively, and metolachlor at 2.7 and 3.2 μg L−1; this was during the first significant flow event following herbicide applications. Metabolites of the chloroacetanilide herbicides were detected more often than the parent compounds (evaluated during May to July each year, when tiles were flowing), with metolachlor ethanesulfonic acid [2‐[(2‐ethyl‐6‐methylphenyl)(2‐methoxy‐1‐methylethyl)amino]‐2‐oxoethanesulfonic acid] detected most often (>90% from all sites), and metolachlor oxanilic acid [2‐[(2‐ethyl‐6‐methylphenyl)(2‐methoxy‐1‐methylethyl)amino]‐2‐oxoacetic acid] second (40–100% of samples at the four sites). When summed, the median concentration of the three chloroacetanilide parent compounds (acetochlor, alachlor, and metolachlor) at the USGS gage site was 3.4 μg L−1, whereas it was 4.3 μg L−1 for the six metabolites. These data confirm the importance of studying chloroacetanilide metabolites, along with parent compounds, in tile‐drained watersheds.