Leaching of seven pesticides currently used in cotton crop in Mato Grosso State—Brazil

This study aimed to evaluate the leaching of pesticides and the applicability of the Attenuation Factor (AF) Model to predict their leaching. The leaching of carbofuran, carbendazim, diuron, metolachlor, α and β endosulfan and chlorpyrifos was studied in an Oxisol using a field experiment lysimeter located in Dom Aquino – Mato Grosso. The samples of percolated water were collected by rain event and analyzed. Chemical and physical soil attributes were determined before pesticide application to the plots. The results showed that carbofuran was the pesticide that presented a higher leaching rate in the studied soil, so was the one representing the highest contamination potential. From the total carbofuran applied in the soil surface, around 6 % leached below 50 cm. The other pesticides showed lower mobility in the studied soil. The calculated values to AF were 7.06E-12 (carbendazim), 5.08E-03 (carbofuran), 3.12E-17 (diuron), 6.66E-345 (α-endosulfan), 1.47E-162 (β-endosulfan), 1.50E-06 (metolachlor), 3.51E-155 (chlorpyrifos). AF Model was useful to classify the pesticides' potential for contamination; however, that model underestimated pesticide leaching.     

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.     

Leachate formation and characteristics from gasification and grate incineration bottom ash under landfill conditions

Characteristics and formation of leachates from waste gasification and grate firing bottom ash were studied using continuous field measurements from 112 m³ lysimeters embedded into landfill body for three years. In addition, the total element concentrations of the fresh ash were analysed and laboratory batch tests were performed to study leachate composition. The three-year continuous flow measurement showed that about one fifth of the leachates were formed, when the flow rate was >200 l/d, covering <3.5% of the study time. After three years, the liquid/solid-ratio for the quenched grate ash was 1 (l/kg (d.m.)) and for the initially dry gasification ash 0.4 (l/kg (d.m.)). The low initial water and residual carbon content of the gasification ash kept the leachate pH at a high level (>13) major part of the study. In the grate ash leachate pH was lower (<8) due to the presence of organic carbon and biodegradation indicated by biological oxygen demand and redox potential measurements. In the gasification ash the high pH probably delayed leaching of major elements such as Ca, therefore, raising the need for a longer after-care period. The high pH also explains the higher leaching of As from the gasification ash compared to the grate ash both in the batch test and under landfill conditions.     

Simulation study on vertical transport of atrazine in soil column

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A NEW METHOD FOR SAMPLING SNOW MELT AND RAINFALL IN FORESTS1

ABSTRACT: Monitoring snow melt rates in high elevation, high snowfall forest stands is difficult mechanically and often impossible due to winter inaccessibility. A method for continuous unattended measurements of melt rate is described. With individual lysimeter pans connected to a common collector, any reasonable number of pans can be installed at each site.     

基于修正遗传算法的夏玉米作物系数及蒸散发估算

农田蒸散量是作物蒸腾量和土壤蒸发量的总和,准确估算农田蒸散量对制定合理的灌溉计划至关重要,进而对农作物的增产保收具有重要的意义。研究作物系数及蒸散量估算模型已成为一个热点科学问题。淮河流域是中国主要的农业生产基地,而夏玉米是淮河流域最主要的粮食作物之一。为研究夏玉米全生育期蒸散估算模型,反映夏玉米逐日作物系数及蒸散量的变化,为当地的农业生产活动提供指导,采用五道沟水文实验站称重式蒸渗仪及气象要素实测数据,应用遗传算法,构建夏玉米全生育期单作物系数蒸散模型,得到其4个生长阶段的作物系数估算值。其中,参考作物蒸散量采用FAO PenmanMonteith公式计算;对估算误差较大的发育期,利用叶面积指数和发育期天数构建调整模型,对发育期作物系数进行数值修正,取得了较好的效果,并进一步估算蒸散量,最终得到遗传算法与多项式回归相结合的夏玉米蒸散估算模型。结果表明:全生育期内,修正后作物系数计算值与实际值的平均绝对误差为0.09,均方根误差为0.12,准确率(绝对误差<0.3)为96.2%;蒸散量计算值与实际值的平均绝对误差为0.89 mm·d^-1,均方根误差为1.28 mm·d^-1,准确率(绝对误差<4 mm·d^-1)为100%;相比FAO推荐的作物系数模型,修正遗传算法模型作物系数和蒸散量的拟合准确率均明显提高,达到精度要求,该文修正遗传算法模型可用于夏玉米的蒸散估算。     

SOIL SOLUTION CONCENTRATIONS: EFFECT OF EXTRACTION TIME USING POROUS CERAMIC CUPS UNDER CONSTANT TENSION1

ABSTRACT: Porous ceramic cups under constant tension (0.45 bar) were used to extract solutions from undisturbed soil columns. Solution concentration changed with length of extraction time. Significant relationships were found between extraction time and concentrations of P, Ca, and K in soil solution for two sample depths in an Omega loamy sand soil column. At two extraction time classes and at two sample depths, combined data from 12 soil columns representing two soil series reinforce the relationship. As time to extract a sample increases, the sample probably represents solution held by soil at tensions approaching those applied to the ceramic cup. We recommend that the choice of an extraction tension be given consideration in studies using porous ceramic cups under constant tension for monitoring constituents of soil solution. In addition, care must be taken to attain good physical contact between the cups and the soil material.     

稻季施用不同尿素品种的氮素径流和淋溶损失

在太湖地区乌栅土上,利用大型原状土柱研究不同尿素品种、施肥量处理在稻季氮素径流和淋溶损失.结果表明,包膜尿素在基施情况下,田面水总氮浓度始终接近对照水平,通过径流损失的可能性很小.尿素处理施肥后2d内田面水氮浓度达最高值,随后急剧下降,施肥与径流产生时间的间隔是决定径流氮排放大小的关键因素,施肥5d后的降雨不易造成大的径流排放,氮径流损失与尿素施用量呈显著正相关.各处理间的氮素淋溶排放无显著差异,在2.66～3.25kgN/hm²之间;淋溶液中NO₃^--N浓度最高为0.83mgN/L,在正常施肥情况下,此类土壤氮的淋溶不会造成地下水NO₃--N的严重污染.     

麦季施用不同尿素的氮排水和渗漏损失

在太湖地区乌栅土的稻麦轮作条件下,利用大型原状土柱渗漏液采集器(monolithlysimeter),比较不同尿素品种和施肥量(普通尿素150、300kg·hm-2和包膜尿素100、150kg·hm-2)处理对麦季土壤氮随径流和渗漏损失的影响。结果表明:施用的包膜尿素当季氮不易随排水流失,但可能增加下季氮流失的风险。两麦季排水溶解氮均以NO-3 N为主,达76.7%以上,NH+4 N比例很小;麦季排水氮输出量年际差异明显,降雨产生排水与施肥时间间隔的不同是造成排水氮输出量差异的关键因素;施肥后20d内发生排水易产生较多的氮排放。渗漏液硝态氮浓度(最高为8.12mg·L-1)均未超过饮用水NO-3 N含量标准,但均已超过水体富营养化标准;对照处理麦季渗漏液量显著高于施肥处理;在150kg·hm-2的施N量水平下,普通尿素或包膜尿素均未显著增加氮的渗漏,但过量施用普通尿素则加大氮渗漏的风险。