Influence of Stand-Alone Vertical Gas Vents on Aeration and Denitrification of Organic Municipal Waste Assessed by Two-Dimensional (2D) Lysimeters

Landfilled organic waste, in the presence of oxygen, can undergo aerobic decomposition facilitated by heterotrophic microorganisms. Aerobic degradation of solid waste can quickly consume available oxygen thus curtailing further degradation. The aim of this study was the investigation of a low-cost method of replenishing oxygen consumed in landfilled waste. Three 2D lysimeters were established to investigate the effectiveness of stand-alone, vertical ventilation pipes inserted into waste masses. Two different configurations of ventilation were tested with the third lysimeter acting as an unventilated control. Lysimeters were left uninsulated and observed over the course of 6 months with regular collection of gas and leachate samples. Lysimeters were then simulated for Oxygen (O2) and Nitrous oxide (N2O) to analyze the denitrification contributions of each. The experiment revealed that a single ventilation pipe can increase the mean oxygen level of a 1.7 m × 1.0 m area by up to 13.5%. It also identified that while increasing the density of ventilation pipes led to increased O2 levels, this increase was not significant at the 0.05 probability level. A single vent averaged 13.67% O2 while inclusion of an additional vent in the same area only increased the average to 14.59%, a 6.7% increase. Simulation helped to verify that lower ventilation pipe placement density may be more efficient as in addition to the effect on oxygenation, denitrification efficiency may increase. Simulations of N2O production estimated between 8% - 20% more N2O being generated with lower venting density configurations.

野外Lysimeter试验^(14)C同位素示踪研究土壤-小麦系统多环芳烃萘的环境归趋

采用14C同位素示踪技术和野外Lysimeter试验,进行了小麦种植条件下多环芳烃萘(naphthalene)的环境归趋的定量化研究。结果表明,气态损耗是土壤中外源萘含量减少的主要途径,其中矿化损失约占气态损耗的84.41%,作物的存在可显著促进萘的气态损耗,矿化速率和挥发速率可分别提高43.51%和190.32%,其原因可能与植物的根系分泌活动有关。经过一个小麦生长周期,土壤表层残留14C占施入量的1.73%;对土壤柱样的分层分析和土壤渗滤放射性强度测定发现,萘存在明显的纵向迁移现象并可能影响地下水水质,渗滤损失约占施入总量的0.043%;收获期萘在小麦体内含量仅占外源施入量的0.003%,但小麦籽粒已明显检测到14C的存在,浓度约为0.16mg·kg-1,因此农田环境中多环芳烃残留对食品安全的影响也应引起重视。

PELIMINARY ANALYSES FOR CROP WATER CONSUMPTION BY USING LYSIMETER

This paper deliberates on the issue of water consumption (evapotranspiration, ET) of three main crops in North China: wheat, corn and bean, which is mainly related to three factors as indicated by the definition of SPAC system. Water consumption was measured on daily and sometimes hourly basis by Lysimeter, which can be adjusted to have the same groundwater level as that in the field, thus the measurement could serve as representative of crop water consumption for adjacent area. The consumption period for three crops has been analyzed and cumulative deviation from the mean of daily evapotranspiration been used to divide the whole growing period into several parts, which are related to but different from the growing periods. The serial correlation coefficients for varied lag time have been calculated to verify that the process of daily ET is not random, and therefore the cumulative daily consumption has been simulated by polynomial method, which gives relative good results. Finally, the effort has been made to investigate the relation of crop yield and water consumption and water use efficiency based on a time series of seven years.

Nitrate leaching of winter wheat grown in lysimeters as affected by fertilizers and irrigation on the North China Plain

Proper application of nitrogen（N） fertilizers and irrigation management are important production practices that can reduce nitrate leaching into groundwater and improve the N use efficiency（NUE）. A lysimeter/rain shelter facility was used to study effects of the rate of N fertilization, type of N fertilizer, and irrigation level on key aspects of winter wheat production over three growing seasons（response variables were nitrate transport, N leaching, and NUE）. Results indicated that nitrate concentration in the soil profile and N leaching increased with the rate of N fertilization. At the end of the third season, nitrate concentration in the top 0–75 cm layer of soil was higher with manure treatment while urea treatments resulted in higher concentrations in the 100–200 cm layer. With normal irrigation, 3.4 to 15.3% of N from applied fertilizer was leached from the soil, yet no leaching occurred under a stress irrigation treatment. The manure treatment experienced less N leaching than the urea treatment in all cases except for the 180 kg N ha^-1 rate in 2011–2012（season 3）. In terms of grain yield（GY）, dry matter（DM） or NUE parameters, values for the manure treatment were lower than for the urea treatment in 2009–2010（season 1）, yet were otherwise higher for urea treatment in season 3. GY and crop nitrogen uptake（NU） were elevated when the rate of N fertilizer increased, while the NUE decreased; GY, DM, and NU increased with the amount of irrigation. Data indicated that reduced rates of N fertilization combined with increased manure application and proper irrigation management can lower nitrate levels in the subsoil and reduce potential N leaching into groundwater.

Estimation of evapotranspiration with drainage lysimeters in the Taihang Mountain area,China

In this research, the evapotranspiration （ET） of three native vegetation communities were measured using drainage lysime- ters in the Taihang Mountain area, China. They are a local grass, Themedajaponica, a local shrub, Vitex negundo var. heterophylla Rebd. and a mixture of both communities. The ET was measured using level lysimeters （with a slope of 0°） and slope lysimeters （with a slope of 25°）. In general, the measured ET was higher in the level lysimeters than in the slope lysimeters because of the water loss of surface runoff from the slope lysimeter. The total ETs over the growing season for the grass, shrub, and the mixture were 730.4, 742.0 and 790.7 mm, respectively in the level lysimeters, and 535.5, 504.1 and 540.1 mm, respectively in the slope lysimeters. In addition, the monthly ET peaked in August and had close linear relationship with leaf area index. The drainage lysimeter is an effective tool to estimate plant ET in mountain areas. The results from this research would provide scientific information for the vegetation recovery and sustainable development of forestry in the TM areas.

Conversion of organic carbon in the decomposable organic wastes in anaerobic lysimeters under different temperatures

The quantitative fractions of conversion of organic carbon in the decomposable organic wastes with initial moisture of 70% sorted from municipal solid wastes(MSW) in lysimeters into biogas, leachate and solid residue were characterized, under temperatures of 25, 30 and 41℃, respectively, and circulation of leachate generated within the lysimeters. It is found that 27% of organic carbon in the wastes are conversed into gases, 0.8% into leachate, and the other 72% remained in the decomposable solid residues, after 180 days' degradation at 41℃. Higher temperature will lead to more rapid degradation and result to higher conversion of the organic carbon to biogas and lower to both solid residues and leachate, while the pollutant concentrations in leachate will be lower at a higher temperature and the values of COD are quite consistent with TOC.

Combined Effect of Infiltration, Capillary Barrier and Sloping Layered Soil on Flow and Solute Transfer in a Heterogeneous Lysimeter

This aim of this paper is to describe a study of the combined effect of infiltration, capillary barrier and sloping layered soil on both flow and solute transport processes in a large, physical model (1 × 1 × 1.6 m3) called LUGH (Lysimeter for Urban Groundwater Hydrology) and a 3D numerical flow model. Sand and a soil composed of a bimodal sand-gravel mixture were placed in the lysimeter to simulate one of the basic structural and textural elements of the heterogeneity observed in the vadose zone under an infiltration basin of Lyon (France). Water and an inert tracer (KBr) were injected from the top of the lysimeter using a specific water sprinkler system and collected at 15 different outlets at the bottom. The outlet flows and the 15 breakthrough curves obtained presented high heterogeneity, emphasising the establishment of preferential flows resulting from both capillary barrier and soil layer dip effects. Numerical modelling led to better understanding of the mechanisms responsible for these heterogeneous transfers and it was also used to perform a sensitivity analysis of the effects of water velocity (water and solute flux fed by the sprinkler) and the slope interface. The results show that decreasing velocity and increasing the slope of the interface can lead to the development of preferential flows. In addition, the offset of the centre of gravity of the flow distribution at the output increases linearly as a function of the slope angle of the layered soil. This paper provides relevant information on the coupling between hydrodynamic processes and pollutant transfer in unsaturated heterogeneous soil and emphasizes the role of the geometry of the interfaces between materials and boundary conditions as key factors for preferential flow.

Lysimeter 法椰子作物系数研究

用溶积式Lysimeter确定椰子树的耗水量。在1986年11月到1987年5月对树令为6年、叶面积指数为2.4的椰子树进行了观测,其每日耗水量为2.7-4.1mm,平均耗水量是有规律的,为每日3.3mm。用Pen-man法、Blaney-Criddle法,辐射法和美国A级蒸发皿法分别得到作物系数值为0.54、0.73、0.60和0.65。

Lysimeter based crop coefficients for estimation of crop evapotranspiration of black gram (Vigna Mungo L.) in sub-humid region

Black gram is dominant pulse crop of the region.Crop coefficient is an important parameter,which needs to be determined for accurate estimates of the crop water requirement.Crop coefficient,the ratio of potential crop evapotranspiration to reference evapotranspiration,is an important parameter in irrigation planning and management.However,this information is not available for many important crops in the study region.A study was undertaken to develop crop coefficients for black gram crop,and a comparison is made of single and dual crop coefficient approaches to estimate actual crop evapotranspiration under the climatic conditions of Udaipur,India.Crop coefficient was developed from daily measured black gram evapotranspiration(ETBG)data by electronic weighing lysimeter and reference evapotranspiration calculated using standard Penman-Monteith method.The measured values of crop coefficient for the crop were 0.48,1.18 and 0.33 during initial,mid-season and late-season stages.The evaluation of different approaches showed that daily ETBG estimate based on dual crop coefficient method have been found best(SE=0.40,r=0.96).Furthermore,a quadratic curve(second-order polynomial)method were fitted well(SE=0.47,r=0.94)to predict crop coefficient values as function of days after sowing(DAS).These locally developed and evaluated values can be used for proper irrigation planning in water scarcity area of Udaipur and other areas with similar agro-ecological conditions.

Simple weighing lysimeters for measuring evapotranspiration and developing crop coefficients

Knowledge of cotton crop evapotranspiration(ET)is important in scheduling irrigations,optimizing crop production,and modeling ET and crop growth.The ability to measure,estimate,and predict ET and cotton crop water requirements can result in better satisfying the crop’s water needs and improving water use efficiency.Weighing lysimeters have been used for many years to measure and study water use,and to develop crop-coefficient functions necessary in estimating ET.Electronic weighing lysimeters,consisting of a steel outer tank and inner tank,electronic loadcell assemblies,and a PVC drain system,were designed,constructed,and installed.Each lysimeter cost approximately US$1700(in 2001)in materials,required two people and 40 hours of labor to construct,and were installed by two people using minimal excavation and hand tools.Daily ET data for cotton were collected from 2003 to 2006 to quantify cotton water-use and to develop crop coefficient functions.Seasonal water use ranged generally from 2 to 8 mm/d.Seasonal water-use patterns varied considerably among growing seasons due to variable environmental and crop-growth conditions,making determination of an“average”crop-coefficient function difficult.

Response of forestland soil water content to heavy rainfall on Beijing Mountain, northern China

Continuous recording of precipitation and soil water content（SWC）, especially during long periods of torrential rainfall, has proven challenging. Over a 16 h period spanning 21-22 July, 2012, Beijing experienced historic rainfall that totaled 164.4 mm. We used large lysimeter technology in four forested plots to record precipitation and variation in SWC at 10-min intervals to quantify the response of forestland SWC to heavy rainfall in a semi-arid area. Mean,maximum and minimum rainfall intensities were 23.4, 46.8and 12.0 mm/h, respectively. Rainfall was concentrated in 2-6 mm bursts that accounted for 67.32 % of the total rainfall event. Soil moisture conditions in this region are strongly dependent on patterns of precipitation. Water infiltration into 20, 40, 60, 80, 100, 120 and 160 cm soil layers required 1, 5,20, 37, 46, 52 and 61 mm of precipitation, respectively, and to fully saturate these soil layers required 80, 120, 140, 150, 180,200 and 220 mm of precipitation, respectively.

A proposed surface resistance model for the Penman-Monteith formula to estimate evapotranspiration in a solar greenhouse

Greenhousing is a technique to bridge season gap in vegetable production and has been widely used worldwide. Calculation of water requirement of crops grown in greenhouse and determination of their irrigation schedules in arid and semi-arid regions are essential for greenhouse maintenance and have thus attracted increased attention over the past decades. The most common method used in the literature to estimate crop evapotranspiration（ET） is the Penman-Monteith（PM） formula. When applied to greenhouse, however, it often uses canopy resistance instead of surface resistance. It is understood that the surface resistance in greenhouse is the result of a combined effect of canopy restriction and soil-surface restriction to water vapor flow, and the relative dominance of one restriction over another depends on crop canopy. In this paper, we developed a surface resistance model in a way similar to two parallel resistances in an electrical circuit to account for both restrictions. Also, considering that wind speed in greenhouse is normally rather small, we compared three methods available in the literature to calculate the aerodynamic resistance, which are the r_a^1 method proposed by Perrier（1975a, b）, the r_a^2 method proposed by Thom and Oliver（1977）, and the r_a^3 method proposed by Zhang and Lemeu（1992）. We validated the model against ET of tomatoes in a greenhouse measured from sap flow system combined with micro-lysimeter in 2015 and with weighing lysimeter in 2016. The results showed that the proposed surface resistance model improved the accuracy of the PM model, especially when the leaf area index was low and the greenhouse was being irrigated. We also found that the aerodynamic resistance calculated from the r_a^1 and r_a^3 methods is applicable to the greenhouse although the latter is slightly more accurate than the former. The proposed surface resistance model, together with the r_a^3 method for aerodynamic resistance, offers an improved approach to estimate ET in greenhouse using the PM formula.

Models and measurements of seven years of evapotranspiration on a high elevation site on the Central Tibetan Plateau

Evapotrantaspiration is a crucial part of the hydrological cycle but few ground observatories for the Tibetan Plateau exist.In this study,we present lysimeter measurements from the growing season during seven years at a remote field location on the Tibetan Plateau.The measurements show rates between 2.5 and 3 mm·d-1 during the warmer months from June to August,dropping to 2 to 2.5 mm·d-1 in September.This results in a total volume of evapotranspiration of approximately 300 mm·yr-1 for the months from June to September.The inter-daily variability is however large,and comparison to meteorological variables suggest that this is largely driven by radiation and humidity.Data for a single season from a nearby flux tower allows us to compare the two common measurement methods for evapotranspiration in the field,showing an overall good agreement between the approaches.We also tested commonly applied models used to estimate evapotranspiration rates,namely the FAO-PenmanMonteith(PM) and the Priestly-Taylor(PT) model,which both make use of radiation data as well as the simpler Hargreaves-Samani(HS) and Rohwer(R)models which only need air temperature and wind speed as input.The most data intensive model(PM)has the lowest root mean square error(RMSE)(1.36 mm·d-1) and the mean bias error(MBE)(-0.05 mm·d-1) and reproduces the daily variability generally well.The much simpler HS model performs slightly worse(1.38 and 0.35 mm·d-1),but fails to reproduce the variability,due to its lack of information of local radiation and humidity data.Our results are in line with large scale estimates of evapotranspiration for the cold and arid region,provide a first long time series of in-situ measurements from a high elevation site and suggest that both the PM and HS models are appropriate when no direct measurements are available.

Field Measurement of Cotton Seedling Evapotranspiration

Information on cotton evapotranspiration (ET) during the seedling growth stage and under field conditions is scarce because ET is a difficult parameter to measure. Our objective was to use weighable lysimeters to measure daily values of cotton seedling ET. We designed and built plastic weighable micro-lysimeters (ML) that were 0.35 m deep with a soil volume of 6300 cm3. The soil core was obtained in-situ by pushing the ML well casing into the soil using a commercial soil sampler. The soil core was weighed with tension and compression type load-cells, where a change in mass of 18 g·d-1 was equivalent to a water evaporation of 1 mm·d-1. We compared load-cell measurements of changes in mass to values measured with a portable field scale by linear regression analysis, and the slope was equal to 1, indicating no statistical difference (P = 0.05) between the two measurements. We measured and compared seedling height, root length and leaf area of cotton plants in the ML with cotton plants in the surrounding area and this comparison showed that the ML used was suitable to measure cotton seedling ET for the first 30 days after seed emergence. The root mean squared error for crop height was 0.09 cm, for leaf area index (LAI) was 0.03 m2·m-2 and 6.5 cm for root length. Also, soil temperature at a 0.1 m depth was statistically (P = 0.05) the same in and outside the ML’s. For two planting dates, we measured daily values of soil water evaporation (E) and cotton seedling ET. The day following an irrigation event, E was ~ 9 mm d-1 and quickly declined the following days. Results showed that ML’s provide an accurate tool to measure water losses from the soil and cotton plants with a LAI of ≤0.2.

Simulation study on vertical transport of atrazine in soil column

A simulation experiment on vertical transport of herbicide atrazine (2 chloro 4 ethylamino 6 isopropylamino s triazine) in soil column was conducted using lysimeter system. The atrazine concentrations in leaching water and soil samples in column at 8 layers with 10 cm thick of each layer were detected by high performance liquid chromatography. The results show total atrazine amount in leaching water increases nonlinearly with the leaching time and the herbicide application rate, and the atrazine concentrations in column soil decrease with the vertical depth after water leaching. The distribution of atrazine mass in the system after 154 days were that among the applied atrazine, 0.3% is out through leaching water, 1% is methanol extractable residues in soil, 46% is methanol nonextractable residues in soil, and 52% is other loss (including volatilization and degradation). The study indicates movement of atrazine in agriculture soil may not only have relation to the properties of herbicide, but also to the herbicide application history.

Estimation of Rice Evapotranspiration Using Reflective Images of Landsat Satellite in Sefidrood Irrigation and Drainage Network

More accurate estimation of crop evapotranspiration(ET_c)in a regional scale has always been one of the most important challenges.Temporal and spatial monitoring of ET_(c )using satellite images can help to enhance accuracy of estimations.In this study,the(ET_c)_(rice) maps were produced by using statistical/experimental methods based on crop coefficient(K_c)maps derived from vegetation index(Ⅵ).K_c was estimated using four methods,including linear relationship between K_c and Ⅵ(K_c-Ⅵ),calibrated model of K_c-Ⅵ,linear relationship between K_(cb)(the basal crop coefficient)and Ⅵ(K_(cb)-Ⅵ),and calibrated model of K_(cb)-Ⅵ.The results showed that calibrated model of K_c-Ⅵ had a better performance compared to the other methods,with normalized root mean square errors(NRMSE),mean absolute error and root mean square error being 5.7%,0.05 mm/d and 0.06mm/d,respectively.(ET_c)_(rice) maps were produced by using calibrated model of K_c-Ⅵ and reference evapotranspiration(ET_0)from FAO Penman-Monteith method.The NRMSE was 21.3%for using FAO Penman-Monteith method.Therefore,calibrated K_c-Ⅵ model in combining with ET_0 based on the Landsat 7 ETM+images could be provided a good estimation of(ET_c)_(rice) in regional scale,and can be applied to estimate water requirement due to the free and facilitate access.

Comparison of Machine Learning Regression Methods to Simulate NO₃Flux in Soil Solution under Potato Crops

Nitrate (NO3) leaching is a major issue in sandy soils intensively cropped to potato. Modelling could test the effect of management practices on nitrate leaching, particularly with regard to optimal N application rates. The NO3 concentration in the soil solution is well known for its local heterogeneity and hence represents a major challenge for modeling. The objective of this 2-year-study was to evaluate machine learning regression methods to simulate seasonal NO3 concentration dynamics in suction lysimeters in potato plots receiving different N application rates. Four machine learning function approximation methods were compared: multiple linear regressions, multivariate adaptive regression splines, multiple-layer perceptrons, and least squares support vector machines. Input candidates were chosen for known relationships with NO3 concentration. The best regression model was obtained with a 6-inputs least squares support vector machine combining cumulative rainfall, cumulative temperature, day of the year, N fertilisation rate, soil texture, and depth.

沙坡头生态水文学研究进展及水量平衡自动模拟监测系统

在中国科学院野外站网络重点科技基础设施建设项目的支持下,沙坡头沙漠研究试验站建成了以36台大型称重式蒸渗仪为主体的中国北方不同气候带沙区水量平衡自动模拟监测系统——Lysimeter群。概述了沙坡头生态水文学研究进展。介绍了Lysimeter群建设的科学目标、构建思路、建设内容和预期研究方向。Lysimeter群由大型称重式蒸渗仪、各类探头、移动大棚和降水模拟器等组成,具有集成性和唯一性。该平台可全自动模拟控制降水和地下水位,量化植物水分来源;自动监测蒸散发、植物蒸腾、土壤水渗漏、土壤水分、温度和电导率等。该平台的建成将提升在不同尺度上认知中国沙区生态和水文过程、植被重建的生态水文学和环境胁迫生理生态学机理等相关领域的研究能力,回答不同沙区土壤水分植被承载力和人工植被稳定性维持的生态水文阈值等国家在防沙治沙实践中所面临的核心科学问题。

Determination of crop and soil evaporation coefficients for estimating evapotranspiration in a paddy field

Accurate estimation of evapotranspiration is important in efficient water management for improving water use efficiency.In order to obtain evapotranspiration and evaporation beneath the canopy using the Food and Agriculture Organization(FAO)method,pan evaporation was used instead of reference evapotranspiration calculated by the Penman-Monteith equation with detailed meteorological data.The total crop coefficient and soil evaporation coefficient were determined using actual measured daytime evapotranspiration and evaporation by the Bowen ratio energy balance and lysimeter,respectively,in a rice paddy field in Japan.The average evapotranspiration was 5.3 mm/d,4.4 mm/d,7.4 mm/d and 6.3 mm/d and crop coefficient was 0.79,1.18,1.01 and 0.86 for the initial stage,development stage,middle-season stage and late-season stage,respectively.The evaporation was low and almost constant with an average value around 0.77 mm/d when the leaf area index(LAI)reached 3.The proposed average crop coefficients for different growing stages were applied to estimate daytime evapotranspiration and found suitable.A simple soil water evaporation coefficient model was developed using leaf area index for practical use and it was found that it could accurately estimate evaporation.