天津市农用地膜残留状况调查及影响因素分析

典型种植制度下农田地膜残留系数及地膜残留状况调查,是制定清洁生产技术规范、保障农田环境安全的基础。按照第一次全国污染源普查《农业污染源产排污系数测算实施方案》的要求,在天津市共计安排各类地膜残留现状监测点6个。结果表明：全市各监测点当季地膜残留系数在4.44%~14.80%之间,平均值为10.30%;农田土壤中地膜残留量平均值为33.69±12.18 kg.hm-2,低于60 kg.hm-2的全国平均水平。在几个典型种植制中,露地蔬菜种植类型残留量最高,达到了52.92±1.36 kg.hm-2;其次是西瓜种植类型,为39.96±2.27 kg.hm-2;春玉米种植类型也较高,为37.63±0.54 kg.hm-2;保护地蔬菜类型较低,为25.55±8.04 kg.hm-2;棉花种植类型的2个监测点也较低,但2个点之间略有差异分别为26.55±0.99 kg.hm-2和19.57±1.96 kg.hm-2;地膜铺设年限、当季地膜铺设量均对地膜残留量产生影响,年限越长、铺设量越大,地膜残留量也越大。而地膜厚度、地膜的规格、揭膜时间和方式等由于监测太少而差异不明显。     

噻呋酰胺在马铃薯和土壤中检测方法及残留动态研究

建立了马铃薯果实、植株和土壤样品中噻呋酰胺的分析方法,并测定了噻呋酰胺在马铃薯田中的残留消解动态及最终残留量。样品采用丙酮提取,二氯甲烷萃取,气相色谱-电子捕获检测器（GC-ECD）检测。当样品中添加的质量分数为0.001～0.05 mg·kg^-1时,平均添加回收率为85.76%～93.53%,相对标准偏差（RSD）为1.44%～7.33%,噻呋酰胺的最低检出质量浓度（LOQ）为0.001 mg·kg^-1。2009—2010年在天津和南京两地的田间残留试验结果表明：噻呋酰胺在马铃薯植株和土壤中消解较快,半衰期分别为6.08～6.30 d和4.92～7.07 d,施药后21 d的消解率均在91%以上;240 g·L^-1噻呋酰胺悬浮剂按推荐剂量480 g·hm^-2和1.5倍推荐剂量720 g·hm^-2兑水喷雾1次,在马铃薯收获期时噻呋酰胺在马铃薯果实和土壤中的最终残留量分别为质量浓度0.076 2～0.649 6 mg·kg^-1和0.020 7～0.305 0 mg·kg^-1。根据大田试验结果,建议噻呋酰胺在马铃薯中的最大残留限量标准为1.0 mg·kg^-1。     

秸秆还田下氮肥用量对玉米产量及土壤无机氮的影响

研究连续2年秸秆还田下氮肥用量对玉米产量、氮肥利用率及土壤硝态氮的影响,结果表明,玉米产量随着施氮量的增加逐渐增加,施氮量达到216 kg·hm^-2时,产量最高,施氮量超过216 kg·hm^-2时产量有降低的趋势。相同施氮处理玉米产量年际变化明显,2010年较2009年产量提高0.69％~4.75％。氮肥利用率、氮肥农学利用率和氮收获指数随着秸秆还田年限的增加,均有不同程度的增加。2年0~100 cm土层土壤硝态氮含量均以施氮240 kg·hm^-2最高,且有向土壤深层迁移的趋势,对浅层地下水构成潜在的威胁。与施氮240 kg·hm^-2相比,施氮168、192 kg·hm^-2和216 kg·hm^-2处理0~100 cm土壤无机氮残留量2年平均减少39.87％、35.84％和29.38％。相同施氮处理,0~100 cm土壤无机氮累积量2010年较2009年略有降低。综合考虑玉米产量、氮肥利用率与生态环境效益,该地区最适施氮量200 kg·hm^-2左右。     

我国地膜覆盖和残留污染特点与防控技术

地膜覆盖技术已成为我国农业应用最为广泛的农艺技术之一,但同时地膜残留污染也成为影响农业可持续发展的一个重大问题,系统分析梳理地膜覆盖种植技术、地膜残留污染的特点及防控技术对于该技术合理利用具有重要意义。本文在已有工作基础上,系统分析了我国地膜覆盖种植技术应用情况、地膜残留污染特点和防治技术。结果表明,20世纪80年代以来,我国地膜用量及覆盖面积一直呈大幅度上升态势,年增长率在8％左右,1991—2011年20年间,地膜使用强度增加了3～10倍,但存在明显区域差异。总体上,北方省区的地膜使用强度大,增长幅度快。地膜覆盖应用作物也从经济作物扩大到粮食作物,应用面积最大作物依次为玉米、蔬菜、棉花、烟草和花生等。地膜覆盖技术的应用产生了巨大效益,但同时也带来了一系列污染危害。长期覆膜农田土壤中都存在程度不同的残膜污染,残留量一般在71．9-259．1kg·hm-2。西北地区是残膜污染最严重的地区,土壤中残膜量远远高于华北和西南地区。残留地膜大小和形态多种多样,主要有片状、蜷缩圆筒状和球状等,在土壤中呈水平、垂直和倾斜状分布。目前,我国地膜残留污染防治技术滞后,人工回收是普遍和主要的回收形式,其他防治技术如机械回收、节约型地膜应用、生物降解地膜尚未较大规模应用。当前,为防止地膜残留污染进一步加剧,急需修订完善地膜标准和加强质量监管,提高可回收性;推广节约型地膜使用技术和残膜回收技术;开展地膜覆盖技术适应性研究,促进技术合理利用。     

盘锦地区稻田田面水氮素动态变化及化学氮肥投入阈值研究

以水稻为供试作物,水稻土为供试土壤,采用田间定位试验的方法,以施肥后田面水中的总氮（TN）、NH4^＋-N和NO3^--N浓度为指标,进行了施氮后田面水中氮素释放规律研究。结果表明,施肥后田面水中的总氮（TN）、NH4＋-N和NO3--N浓度随着施肥量的增加而增加,随着时间的推移三者的浓度呈先上升后下降的趋势,一周后趋于稳定;以氮素表观盈余率和植株吸氮量为指标,从环境安全角度研究水稻生产化学氮肥投入阈值,初步确定试验区环境安全化学氮肥投入阈值为189.22～218.98 kg·hm^-2;以水稻产量为指标,进行了粮食安全氮肥投入阈值研究,初步确定试验区水稻生产粮食安全化学氮肥投入阈值为202.24～288.89 kg·hm^-2。综合考虑粮食安全和环境安全,试验区化学氮肥投入阈值为202.24～218.98 kg·hm^-2。     

施入城市生活垃圾堆肥对玉米植株重金属分布及土壤养分的影响

以玉米为供试作物,研究施入生活垃圾堆肥对土壤和玉米各器官重金属分布规律及对土壤养分的影响。结果表明：连续3年施肥,土壤速效养分的含量明显增加;土壤重金属呈现累积,但含量远远低于二级土壤标准（GB 15618—1995）;植株中重金属含量表现为根部〉茎秆〉叶片〉籽粒,Cd在植株根部富集,但未大量向其他部位转移,玉米植株地上部分重金属含量明显低于饲料卫生标准（GB 13078—2001）。由此推断,在短期内（3年）,年施入60 000 kg·hm^-2的垃圾堆肥能提高土壤肥力,且暂时不会引起土壤重金属污染,也不影响玉米植株的饲用;使用多年后应及时监测,以保证安全性。     

缙云县农作物施肥现状调查与对策

通过对825个典型户地块、面积134．84hm。农作物施肥现状调查，结果显示，各类种植模式地块投入肥料（折纯）平均为600kg·hm^-2，其中化肥投入526．5kg·hm^-2，有机肥投入73．5kg·hm^-2，分别占总施肥量的87．8％和12．2％；农作物过量使用化肥，有机肥投入偏少，且化肥投入N、P、K结构比例不合理，典型户地块施肥水平不平衡；针对调查结果提出了对策措施。     

杭州城区蔬菜地农药残留现状与评价

采用加速溶剂萃取,气相色谱-质谱法测定了杭州市城区蔬菜地中农药残留量,并进行了评价。结果表明：杭州市城区蔬菜地中有机氯类、有机磷类、拟除虫菊酯类农药残留量为ND～0.19mg·kg^-1、ND～0.238mg·kg^-1、ND～0.013mg·kg^-1,检出率为52.4%、33.3%和28.6%。其中有机氯类农药达到国家土壤环境质量标准（GB15618—1995）二级以上,符合无公害蔬菜产地环境要求;根据加拿大残留限量标准评价有机磷类农药,超标率为14.3%;拟除虫菊酯类农药对土壤造成的污染不论是残留量还是检出率都小于前2类农药。     

嘉兴市农业面源污染源和农田氮磷平衡的历史变化特点

应用1990--2005年的统计数据，研究了嘉兴市农业面源污染源的历史变化特点及农田N和P的平衡状况。结果表明，1990--2005年的16年间，嘉兴市主要农业面源污染源发生了显著的变化，化肥施用对农业面源污染物N、P的贡献相对下降，而畜禽粪便排放对农业面源污染物中N、P的贡献却明显增加。全市单位面积农田N的盈余值1991--1997年间达到较高水平，在100kg·hm^-2以上；1998年以后明显下降，在53．87～100．73kg·hm^-2之间变化。而单位面积农田P的盈余值则随时间呈增加的趋势，1997年前在37．23～70．88kg·hm^-2之间；而1998年后在68．35~101．29kg·hm^-2之间；P已成为农田养分潜在流失的重要因子。总体上，2000年以来嘉兴市单位面积农田N和P的盈余值均低于浙江省的平均水平。在嘉兴市农田养分管理中，应加强人畜粪便的资源化利用，重视N肥的减量化施用和P肥的高效利用。     

土壤As动态影响下枸杞质量评价及环境风险预测

选择柴达木盆地诺木洪农场3种类型农田进行20 cm表层土壤砷（As）含量检测。第1种为新开垦原生地,第2种为20年耕种地,第3种为50年耕种地,检测As含量分别为16.29、14.90、14.04 mg·kg^-1。3种土壤As含量均达到无公害食品标准（25 mg· kg^-1）和绿色食品标准（20 mg·kg^-1）。多年耕种并没有造成农田表层土壤As积累。农田灌溉用河水中未检出As。生产中使用的22种农药、肥料均检测到As,其中15种杀虫剂、杀真菌剂、除草剂、植物激素等,每年输入土壤As 4513.59 mg·hm^-2;7种肥料每年输入土壤As 258015.24 mg·hm^-2。施肥是土壤中As输入的重要来源,最主要的输入源是磷酸二铵,占到50％;其次为复合肥、鸡粪和有机肥。每年随作物输出As总量为4380 mg·hm^-2。模拟田间灌溉,进行土壤柱淋漓试验,农田20 cm表层土壤每年随灌溉淋漓输出As为245230.65 mg·hm^-2,这与随着肥料、农药输入量几乎相等。表层土壤As处在一个输入、输出相对稳定的动态平衡状态。从土壤中输出的As,随灌溉水输入到水系统中,继而造成水系统As的积累,最终将影响到地区农业的可持续发展。     

论地膜污染与防治对策

随着地膜覆盖栽培年限的延长，由于残膜回收率低，土壤中残膜量逐步增加，造成地膜污染。通过分析地膜污染对环境和农作物产生的危害，对回收残膜存在的问题，总结出了防治地膜污染的对策与措施。     

液质联用测定番茄中甲基硫菌灵残留量

为了评价70％甲基硫菌灵可湿性粉剂在番茄中的使用安全性,开展甲基硫菌灵在番茄中的残留量研究。本文建立了分散固相萃取前处理,高效液相色谱/质谱联用法测定甲基硫菌灵在番茄中残留量的方法。样品经乙腈提取,乙二胺-N-丙基甲硅烷（PSA）和无水硫酸镁混合振荡离心除去杂质和水分,上清液用配有电喷雾（ESI）源的高效液相色谱/质谱联用仪测定。田间试验结果建议在番茄上喷施70％甲基硫菌灵可湿性粉剂562.5 g ai·hm^-2,3次施药,推荐安全间隔期为3 d;市场抽检样品检测表明番茄中甲基硫菌灵的残留量均小于0.05 mg·kg^-1,低于最大残留限量3 mg·kg^-1。     

Tillage, cropping systems, and nitrogen fertilizer source effects on soil carbon sequestration and fractions

Quantification of soil carbon (C) cycling as influenced by management practices is needed for C sequestration and soil quality improvement. We evaluated the 10-yr effects of tillage, cropping system, and N source on crop residue and soil C fractions at 0- to 20-cm depth in Decatur silt loam (clayey, kaolinitic, thermic, Typic Paleudults) in northern Alabama, USA. Treatments were incomplete factorial combinations of three tillage practices (no-till [NT], mulch till [MT], and conventional till [CT]), two cropping systems (cotton [Gossypium hirsutum L.]-cotton-corn [Zea mays L.] and rye [Secale cereale L.]/cotton-rye/cotton-corn), and two N fertilization sources and rates (0 and 100 kg N ha(-1) from NH(4)NO(3) and 100 and 200 kg N ha(-1) from poultry litter). Carbon fractions were soil organic C (SOC), particulate organic C (POC), microbial biomass C (MBC), and potential C mineralization (PCM). Crop residue varied among treatments and years and total residue from 1997 to 2005 was greater in rye/cotton-rye/cotton-corn than in cotton-cotton-corn and greater with NH(4)NO(3) than with poultry litter at 100 kg N ha(-1). The SOC content at 0 to 20 cm after 10 yr was greater with poultry litter than with NH(4)NO(3) in NT and CT, resulting in a C sequestration rate of 510 kg C ha(-1) yr(-1) with poultry litter compared with -120 to 147 kg C ha(-1) yr(-1) with NH(4)NO(3). Poultry litter also increased PCM and MBC compared with NH(4)NO(3). Cropping increased SOC, POC, and PCM compared with fallow in NT. Long-term poultry litter application or continuous cropping increased soil C storage and microbial biomass and activity compared with inorganic N fertilization or fallow, indicating that these management practices can sequester C, offset atmospheric CO(2) levels, and improve soil and environmental quality.     

Runoff loss of pesticides and soil: a comparison between vegetative mulch and plastic mulch in vegetable production systems

Current vegetable production systems use polyethylene (plastic) mulch and require multiple applications of agrochemicals. During rain events, runoff from vegetable production is enhanced because 50 to 75% of the field is covered with an impervious surface. This study was conducted to quantify off-site movement of soil and pesticides with runoff from tomato (Lycopersicon esculentum Mill.) plots containing polyethylene mulch and a vegetative mulch, hairy vetch (Vicia villosa Roth). Side-by-side field plots were instrumented with automated flow meters and samplers to measure and collect runoff, which was filtered, extracted, and analyzed to determine soil and pesticide loss. Seasonal losses of two to four times more water and at least three times as much sediment were observed from plots with polyethvlene mulch (55.4 to 146 L m(-2) and 247 to 535 g m(-2), respectively) versus plots with hairy vetch residue (13.7 to 75.7 L m(-2) and 32.8 to 118 g m(-2), respectively). Geometric means (+/-standard deviation) of total pesticide loads for chlorothalonil (tetrachloroisophthalonitrile) and alpha-and beta-endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro6,9-methano-2,4,3-benzodioxathiepin 3-oxide) for a runoff event were 19, 6, and 9 times greater from polyethylene (800+/-4.6, 17.6+/-3.9, and 39.1+/-4.9 microg m(-2), respectively) than from hairy vetch mulch plots (42+/-6.0, 2.8+/-5.0, and 4.3+/-4.6 microg m(-2), respectively) due to greater concentrations and larger runoff volumes. The increased runoff volume, soil loss, and off-site loading of pesticides measured in runoff from the polyethylene mulch suggests that this management practice is less sustainable and may have a harmful effect on the environment.     

Soil fate of agricultural fumigants in raised-bed, plasticulture systems in the southeastern United States

Soil concentrations and degradation rates of methyl isothio-cyanate (MITC), chloropicrin (CP), 1,3-dichloropropene (1,3-D), and dimethyl disulfide (DMDS) were determined under fumigant application scenarios representative of commercial raised bed, plastic mulched vegetable production systems. Five days after application, 1,3-D, MITC, and CP were detected at concentrations up to 3.52, 0.72, and 2.45 μg cm, respectively, in the soil atmosphere when applications were made in uniformly compacted soils with a water content >200% of field capacity and covered by a virtually impermeable or metalized film. By contrast, DMDS, MITC, and CP concentrations in the soil atmosphere were 0.81, 0.02, and 0.05 μg cm, respectively, 5 d after application in soil containing undecomposed plant residue, numerous large (>3 mm) clods, and water content below field capacity and covered by low-density polyethylene. Ranked in order of impact on the persistence of fumigants in soil were soil water content (moisture), soil tilth (the physical condition of soil as related to its fitness as a planting bed), the type of plastic film used to cover fumigated beds, and soil texture. Fumigants were readily detected 13 d after application when applied in uniformly compacted soils with water contents >200% of capacity and covered by a virtually impermeable or metalized film. By contrast, 1,3-D and MITC had dissipated 5 d after application in soils with numerous large (>3 mm) clods and water contents below field capacity that were covered by low-density polyethylene. Soil degradation of CP, DMDS, and MITC were primarily attributed to biological mechanisms, whereas degradation of 1,3-D was attributed principally to abiotic factors. This study demonstrates improved soil retention of agricultural fumigants in application scenarios representative of good agricultural practices.