Among-site variability in environmental and management characteristics: Effect on nutrient loss in agricultural tile drainage

Water quality issues, including harmful and nuisance algal blooms (HNABs), related to nitrogen (N) and phosphorus (P) exported from agricultural lands persist in the Great Lakes region. Previous work examining N and P loss from agricultural fields in portions of the United States (US) and Canada (CA) that drain into Lake Erie, consistently indicate significant nutrient loss from fields in Indiana and Ohio, US compared with those in southwestern Ontario, CA. The primary objective of this study was to examine variation in environmental and management characteristics from 30 sites (US: n = 28, CA: n = 2) located within the Lake Erie Basin and subsequently determine the influence of among-site variation on edge-of-field N and P losses. Using principal component analyses (PCA), we found that among-site variation was predominantly controlled by broad-scale patterns in fertilizer management practices and soil properties; however, N and P loss metrics were largely unexplained by these gradients. As such, fine-scale variability and the interaction of environmental and management characteristics at individual sites more strongly influenced N and P loss. Ultimately, these results further emphasize the importance of site- and nutrient-specific management plans that are needed to mitigate N and P losses from agricultural fields.     

日本污水处理厂设计运行及多因素影响分析

日本的污水处理起步较早,经过多年发展已经建设完善,并在其精细管理下编撰为《下水道統計》.对日本污水处理和污泥处置情况进行全面统计和深入分析,期望对我国污水处理厂的建设和运行具有借鉴意义.污水处理环节分析包括水质水量、处理要求、工艺和处理规模分布、深度处理方法、运行和设计参数、出水回用等;污泥处理环节分析包括污泥产量、处...     

Groundwater-surface water interactions and agricultural nutrient transport in a Great Lakes clay plain system

Nutrient export from agricultural land to surface waters is a significant environmental concern within the Great Lakes Basin (GLB). A field-based watershed-scale study was completed to investigate spatial and temporal variations of phosphorus and nitrate to assess nutrient transport pathways and groundwater-surface water interactions in an agriculturally dominated clay plain system. This was conducted in the 127 km² Upper Parkhill Watershed, near Lake Huron in southwestern Ontario, Canada. Data collection occurred from June 2018 to May 2019 via continuous sensor deployment and discrete sampling of stream water, groundwater, hyporheic zone, and tile drainage water. Samples were analyzed for various nutrient species (total, total dissolved, soluble reactive, and particulate phosphorus, and nitrate-N) to examine the hydrological dynamics of principal transport pathways of agriculturally-derived nutrients. Total phosphorus and nitrate concentrations in stream water ranged from 0.007 to 0.324 mg/L and 0.32 to 13.13 mg NO₃^?-N/L, respectively. Tile drainage water total phosphorous concentrations varied from 0.006 to 0.066 mg/L. Groundwater total dissolved phosphorus concentrations ranged from <0.003 to 0.085 mg/L. Transport of phosphorus through tile drainage was observed to be greater than through groundwater over the study period. No distinct relationship was observed between nutrient concentrations in the hyporheic zone and the vertical hydraulic gradient within this zone in the studied stream reach. Preliminary correlations were discerned between water quality observations and recognized land management practices. Given the elevated stream nutrient concentrations, these results are consequential for the continual improvement of strategies and programs devised to conserve water resources within the GLB.     

Nitrogen requirement for the mesophilic and thermophilic upflow anaerobic filters of a simulated papermill wastewater

This study determined the minimum nitrogen concentration at which the mesophilic and thermophilic upflow anaerobic filters treating a simulated papermill wastewater could operate efficiently. For this purpose, the chemical oxygen demand (COD) to nitrogen ratio in both digesters was increased in five consecutive steps, from 94: 5 to 363: 5. The maximum COD to nitrogen ratios that provided satisfactory operation were 283: 5 (30mg N/L) and 363: 5 (23 mg N/L) for the mesophilic and thermophilic reactors, respectively. The nitrogen consumption of bacteria in the thermophilic digester was lower than that in the mesophilic digester. The operational efficiency of the thermophilic digester was higher than that of the mesophilic one regardless of the COD to nitrogen ratio.     

Nutrient issues on Irish farms and solutions to lower losses

Agriculture in Ireland utilizes 63% of total land area and has a big environmental impact accounting for 70% of phosphorus and 82% of nitrogen in surface waters, and for 97% of ammonia, 81% of nitrous oxide and 86% of methane emissions to air. Phosphorus loss to water is Ireland's most serious pollution problem. The deterioration of water quality that has been evident since the 1970s has been halted and reduction targets for ammonia and greenhouse gas emissions from agriculture are being achieved. These achievements are largely attributable to declining ruminant livestock populations and declining inputs of manufactured fertilizers as a result of increasing emphasis on extensification of production practices in the Common Agricultural Policy during the past decade. Nevertheless, substantial improvements in water quality are needed by 2015 to meet the requirements of the Water Framework Directive. To meet this and a broad range of environmental targets and to comply with the Nitrates Directive, a wide ranging set of regulations governing agricultural practices was implemented into law in 2006. These include general limits on stocking rates on farms of no greater than 170 kg/ha of N in livestock manures applied mechanically or deposited by grazing livestock. There are periods between September and January when the application of fertilizers and manures is prohibited and minimum winter storage requirements apply for manures generated on farms of between 16 and 26 weeks depending on location and agricultural enterprise. The use of phosphorous is stringently curtailed; there are limits on phosphorous concentrations in soil as determined by a soil test and limits on imports of phosphorus onto farms, which generally cannot exceed exports. These regulations are likely to make an important contribution to achieving environmental targets in Ireland, particularly the improvement in water quality required by the Water Framework Directive.     

Photoluminescence of nitrogen-doped anatase

Photoluminescence depending on nitrogen concentration was investigated using anatase-type TiO₂ prepared by the calcination of a mixture of titanyl sulfate hydrate and urea. The substitutional ratio (x) of nitrogen in TiO₂ was successfully varied from 0.004 to 0.022 by changing the molar ratio of the mixture. The absorbance at 380–560 nm due to the formation of mid-gap states was proportional to the substitutional ratio of nitrogen controlled by the preparation conditions. In contrast, the fluorescent intensity at 382 nm originating from the band-to-band transition monotonically decreased with an increase in the substitutional ratio with an expansion of the anatase lattice. On the other hand, the maximum intensity of photoluminescence at 560 nm excited at 350 nm, which could be associated with the transition from the conduction band to the mid-gap states, was observed at x = 0.01. The optimal substitutional ratio for the emission was almost agreed with that for the photocatalytic decomposition of methylene blue and acetaldehyde under visible-light illumination. The photoluminescence was fundamentally determined by the balance between photoexcitation originating from a sufficient number of mid-gap states and deactivation of excited electrons and holes due to lattice distortion or defective states induced with the nitrogen doping.     

Five year water and nitrogen balance for a constructed surface flow wetland treating agricultural drainage waters

The performance of a constructed surface flow wetland in reducing diffuse N pollution coming from croplands is being investigated in an ongoing experiment, begun in 1998 in NE Italy. The 0.32 ha wetland is vegetated with Phragmites australis (Cav.) Trin. and Typha latifolia (L.). It receives drainage water from 6 ha of land managed for an experiment on drainage systems, where maize, sugarbeet, winter wheat and soybean are cultivated. During the period 1998-2002, the wetland received from 4698 to 8412 mm of water per year (on average, about 9 times the environmental rainfall); its water regimen was discontinuous and flooding occurred on a variable number of days per year (from 13 to 126). Nitric nitrogen was the most important form of element load. Its concentration in the inflow water over time was rather discontinuous, with median values ranging from 0.2 (in 2001) to 4.5 (in 2000) mg L(-1). Inflow nitric N concentrations were occasionally in the 5-15 mg L(-1) range. Concentrations reduced passing through the wetland, with a more evident effect in the last year. Over 5 years, the wetland received slightly more than 2000 kg ha(-1) of nitrogen, 87% in nitric form mostly from farmland drainage. The remaining 13% of N was applied as organic slurry directly onto the wetland, with 5 distributions during 1998 to assess wetland performance in treating occasional organic loads. Field drainage loads had a discontinuous time pattern and occurred mostly during autumn-winter, with the exception of the 2001-2002 season which was a very dry. The wetland discharged 206 kg ha(-1) of N, over the 5-year period, with an apparent removal efficiency of about 90%. The disappearance was mostly due to plant uptake (1110 kg ha(-1)) and soil accumulation (570 kg ha(-1)), with the contribution of denitrification being estimated at around 7%.     

On the issue of limiting nutrient and predictions of cyanobacteria in aquatic systems

This study aims at bridging the gap between freshwater and marine eutrophication studies by presenting (1) a cross-system analysis of the relationship between chlorophyll and the total nitrogen (TN) to total phosphorus (TP) ratio (2) a general model to predict concentrations of cyanobacteria from data on TP, the TN/TP ratio, salinity and temperature, and (3) a general trophic level classification for aquatic systems based on chlorophyll classes (for oligo-, meso-, eu- and hypertrophic systems). The data compiled in this study concerns more than 500 lakes and coastal areas covering a very wide domain in terms of nutrient concentrations and salinity. There was no simple relationship between the TN/TP ratio and empirical chlorophyll concentrations or concentrations of cyanobacteria. Variations in TP rather than TN generally seem to be more important to predict variations among systems in chlorophyll-a and cyanobacteria. Different bioavailable forms of the nutrients (DIN, DIP, phosphate, nitrate, etc.) have been shown to have very high coefficients of variation (CV), which means that many samples are needed to obtain reliable empirical data which are necessary in models aiming for high predictive power and practical usefulness.     

硅藻精土在污水处理中的应用与分析

对硅藻精土水处理技术的原理特点和应用情况做了分析和总结.工程实践表明硅藻精土能够提高生化系统的效率,与A/O工艺相结合出水所有指标均稳定达到<城镇污水处理厂污染物排放标准>(GB 18918-2002)一级A标准,具有投资省、运行费用低、占地少、出水水质优等特点,尤其适合于中小城镇的污水处理工程.     

井下作业注氮气排液技术

试油测试过程中,为落实地层产能及地层液性,液氮注排技术越来越受到关注。通过介绍液氮注排的工艺技术、安全防护,总结了其技术特点及与其它工艺的联作技术。经现场应用,该技术施工安全,工艺简单、排液速度快,可控制排液深度,特别对含天然气井有一定参考借鉴价值。