填闲作物防治菜田土壤硝酸盐污染的研究进展

探讨了通过调整蔬菜生产的轮作结构，运用生物修复的原理，引入适宜的深根系填闲作物对深层土壤硝酸盐吸收利用，以避免硝酸盐进一步淋失，提高氮素的利用率的可行性。填闲作物应选择生长迅速、生物量大、氮素累积能力强的作物，在考虑填闲作物防治硝酸盐淋溶的同时，要兼顾其经济利用价值，并指出结合深根系的填闲作物进行合理轮作是蔬菜安全生产及可持续发展的途径之一。     

上海西郊麦期氮素淋溶定位研究

上海西郊水旱轮作地中麦期的淋失研究表明，氮肥淋失的基本形态为硝酸盐氮，施肥后10d左右，形成硝酸盐氮淋溶的高峰期，在整个生育期间，随深度增加，硝酸盐氮浓度峰值向深层推移，但其渗漏深度为80cm左右。氮素的淋失主要发生在11月到次年3月的作物幼苗期，当追肥超过150kg/hm^2后，渗漏量增加很快。     

上海市主要蔬菜中硝酸盐含量及加工处理后硝酸盐和亚硝酸盐含量

本文叙述了上海地区主要蔬菜硝酸盐含量水平,部份蔬菜经加工处理后硝酸盐和亚硝酸盐含量的变化状况。上海地区部份蔬菜硝酸盐含量较高,其中雪菜、芹菜、菠菜、青菜等叶菜类的硝酸盐含量达到数千ppm。但茄果类、瓜类蔬菜中的硝酸盐含量较低,一般为数百ppm。蔬菜经过烧煮后,硝酸盐和亚硝酸盐含量减少50％以上。但雪菜盐渍加工成咸菜后,硝酸盐和亚硝酸盐含量都剧烈增加,超过了50％。当发霉腐烂时,硝酸盐和亚硝酸盐含量增加更高,达到100％以上。通过试验、调查测定,提出几点蔬菜食用时的参考意见:人们应尽量少食一些叶菜类蔬菜而多食一些茄果、瓜类蔬菜。同时增加一些富含维生素C的水果,尽量避免生食蔬菜,少食成菜,严禁取食发霉腐烂的蔬菜。     

基于不同夏填闲作物及种植密度的设施土壤磷素吸收与淋失阻控研究

设施土壤磷素污染日益严重。选用两种夏填闲作物糯玉米和甜高粱,设计了不同种植密度的6个处理,分别为糯玉米常规密度(NYZ,4.95株/m~2)、糯玉米高等密度(NYG,7.50株/m~2)、糯玉米超高密度(NYC,9.90株/m~2)、甜高粱常规密度(TGZ,6.75株/m~2)、甜高粱高等密度(TGG,10.49株/m~2)和甜高粱超高密度(TGC,13.49株/m~2)。结果表明,糯玉米和甜高粱常规密度种植并没有达到饱和,两种填闲作物超高密度种植对其长势并不会有大的影响,甚至可促进作物因对光的竞争而长高,提高单位面积干生物量和品质。随种植密度的增大,两种填闲作物的根部的吸磷量显著减小,地上部位显著增大,TGC的总吸磷量最高。种植夏填闲作物对0～30cm的浅层设施土壤中有效磷和水溶性磷具有良好的淋失阻控效果,以TGC的效果最好。因此,TGC对设施土壤磷素吸收和淋失阻控的效果最好。     

中国蔬菜硝酸盐和亚硝酸盐污染因素及控制研究

本文综述了近十几年来我国城市蔬菜中硝酸盐和亚硝酸盐污染的研究结果,表明随着氮肥使用量的增大,蔬菜中硝酸盐污染较为严重而亚硝酸盐污染也不容忽视。探讨了蔬菜受硝酸盐和亚硝酸盐污染的影响因素及控制对策     

2种轮作模式对镉污染土壤修复潜力的比较

选取重金属Cd污染较严重的郴州矿区废弃农田土壤进行盆栽实验,以红叶甜菜-菊苣和菊苣-油葵作为研究对象,研究2种轮作模式对土壤重金属Cd的修复潜力。实验结果表明:3种作物在轮作期间生长状态良好且对重金属都表现出较强的耐性及吸收积累能力。在红叶甜菜-菊苣轮作模式中,甜菜和菊苣的地上部分对Cd的富集系数(BCF)分别为11.34和8.22;在菊苣-油葵轮作模式中,菊苣地下和地上部分对Cd的富集系数分别为14.14和16.32,成熟油葵各个部位的富集系数都大于1,其中,叶和果肉的富集系数分别为2.57和2.19。因此,对于重金属Cd轻、中度污染的土壤来说,甜菜-菊苣轮作模式对于Cd的富集效果要优于菊苣-油葵。总的来说,利用这3种作物两两轮作的轮作模式,能充分利用四季的气候特点,并能在不影响作物产量的前提下大大提高作物对重金属的提取总量。     

农田氮素淋溶损失影响因素及防治对策研究

农田氮素损失是造成农业非点源污染的主要原因之一,其中由于大量施用氮肥引起的土壤氮素淋溶损失又是农田氮素损失的重要途径.因此,农田氮素损失研究已成为国际土壤化学和环境科学领域研究的热点问题之一.根据近年来国内外在农田氮素运移领域的研究成果,从降雨和灌溉、施肥状况、土壤性质、耕作方式、作物种类和种植方式等方面分析了影响农田氮素淋溶损失的主要因素,提出了改进施肥方式、优化氮肥管理、推广缓释氮肥以及改善土地利用方式等提高氮肥利用率、减小氮素淋溶损失的防治对策.     

一种减少化肥污染的土壤微生物增肥剂的使用技术

进行了澳大利亚ＳＣ２７土壤微生物增肥剂在番茄、黄瓜、青椒等蔬菜上的田间小区和大田试验,结果表明,ＳＣ２７施用后可改善作物根系生长环境,调控土壤养分供应,改良作物品质,产量提高８％－２０％,减少化肥用量１００ｋｇ／ｈｍ＾２,并有减轻土传病害和生理障碍的作用。     

宁波市蔬菜中硝酸盐含量及控制途径探讨

在对宁波市郊基地蔬菜中有害物质系统调查检测的基础上，着重对９大类，１９种 主要蔬菜的硝酸盐积累程度及原因进行分析研究，根据有关食用卫生标准作出总体评价，并对蔬菜生产中存在的问题，提出相应的对策措施，为发展宁波市蔬菜生产，改善菜地生态环境条件，保障人体健康，提供了科学依据。     

杭州市蔬菜硝酸盐污染现状及防治对策

本文调查分析了1989—1990年间杭州市郊菜区7类14种主要蔬菜中硝酸盐及亚硝酸盐的含量。各类蔬菜硝酸盐平均含量范围为136～1847ppm,依次为绿叶菜类>白菜类>根菜类>豆类>甘蓝类>茄果类>瓜类;亚硝酸盐平均含量范围为0.09～3.78ppm。按有关标准对蔬菜硝酸盐含量进行了卫生学评价,分析了蔬菜硝酸盐的来源及积累规律,并提出了相应的防治对策和措施。     

Interception of residual nitrate from a calcareous alluvial soil profile on the North China Plain by deep-rooted crops: a 15N tracer study

15N-labeled nitrate was injected into different depths of an alluvial calcareous soil profile on the North China Plain. Subsequent movement of NO3- -N and its recovery by deep-rooted maize (Zea mays L.) and shallow-rooted eggplant (Solanum melongena L.) were studied. Under conventional water and nutrient management the mean recoveries of 15N-labeled nitrate from K(15)NO3 injected at depths 15, 45, and 75 cm were 22.4, 13.8, and 7.8% by maize and 7.9, 4.9, and 2.7% by eggplant. The recovery rate by maize at each soil depth was significantly higher than by eggplant. The deeper the injection of nitrate the smaller the distance of its downward movement and this corresponded with the movement of soil water during crop growth. Deeper rooting crops with high root length density and high water consumption may therefore be grown to utilize high concentrations of residual nitrate in the subsoil from previous intensive cropping and to protect the environment.     

Pesticide contamination of ground water in the United States--a review

Over 70 pesticides have been detected in ground water. Aldicarb and atrazine along with the soil fumigants EDB and DCP and DBCP have been the pesticides most frequently detected in ground water. Atrazine concentrations have been correlated with high nitrate concentrations. The triazine herbicides, simazine and cyanazine, have also been detected in ground water. The annual amount of recharge, soil type, depth of aquifer from the surface, nitrate contamination and soil pH are important field parameters in determining ground-water contamination potential by pesticides. Pesticide leaching is reduced by proper choice of crop rotation, increasing pesticide application efficiency, and integrated pest management.     

Water quality improvement through bioretention media: nitrogen and phosphorus removal.

High nutrient inputs and eutrophication continue to be one of the highest priority water quality problems. Bioretention is a low-impact development technology that has been advocated for use in urban and other developed areas. This work provides an in-depth analysis on removal of nutrients from a synthetic stormwater runoff by bioretention. Results have indicated good removal of phosphorus (70 to 85%) and total Kjeldahl nitrogen (55 to 65%). Nitrate reduction was poor (< 20%) and, in several cases, nitrate production was noted. Variations in flowrate (intensity) and duration had a moderate affect on nutrient removal. Mass balances demonstrate the importance of water attenuation in the facility in reducing mass nutrient loads. Captured nitrogen can be converted to nitrate between storm events and subsequently washed from the system. Analysis on the fate of nutrients in bioretention suggests that accumulation of phosphorus and nitrogen may be controlled by carefully managing growing and harvesting of vegetation.     

Field test of a cross-injection scheme for stimulating in situ denitrification near a municipal water supply well

A pilot-scale test of an in situ denitrification scheme was undertaken to assess an adaptation of the nutrient injection wall (NIW) technology for treating a deep (30-40 m) nitrate contamination problem (N-NO(-)(3) ~ 10-12 mg/L). The adaptation is called the Cross-Injection Scheme (CIS). It duplicates the NIW method without a wall; wells are installed and operated directly in the aquifer and high-flux zones of the aquifer are preferentially targeted for treatment. The test was conducted on the site of a municipal water supply well field, with the supply well pumping between 15-80 m(3)/h. Acetate was periodically injected into the aquifer between an injection-extraction well pair positioned across the normal direction of flow. The injected pulses were then permitted to move with the water toward the municipal wells, providing a carbon supply to drive the desired denitrification. The fate of nitrate, nitrite, acetate and sulphate were monitored at multilevel wells located between the injection location and the municipal wells. The acetate pulsing interval was approximately weekly (9 h injections), so that the system was operating passively 95% of the time. Previous work on the site has established that the highest solute fluxes were associated with a 1-3 m thick zone about 35 m below surface. This zone was found to respond to the acetate additions as a function of the municipal pumping rate and the carbon-to-nitrogen ratio (i.e., determined by the injected acetate concentration). Initially, acetate was injected just below the theoretical stoichiometric requirement for complete denitrification and nitrate disappearance was accompanied by nitrite production. Increasing the C:N ratio (doubling the acetate injection concentration) increased the removal of nitrate and diminished the occurrence of nitrite. Slowing the municipal pumping rate, with a C:N ratio of 1.2-1.6, resulted in complete nitrate attenuation with no nitrite production and no sulfate reduction. The experiment demonstrated that the CIS injection scheme is a viable option for the treatment of nitrate contamination in situ near high-capacity wells.     

Effect of soil-use on deep groundwater quality in Southern Chile

This study evaluated the effects of farming activities on the quality of deep well water in Southern Chile. In this area, the use of fertilisers is becoming more widespread and the accumulation and poor management of cattle slurry and silage sub-products increases the risk of contamination. The study was carried out in the province of Osorno, where rainfall occurs all year round (maximum in winter); total annual rainfall exceeds 1300 mm. The soil is of volcanic origin and this province includes areas used for intensive farming and cattle raising activities, residential and recreational purposes and extensive farming practices. Water quality was analysed over a 15 month period in deep wells in either intensive farming areas and residential/recreational zones or extensive farming land. Although levels of nitrate were higher in deep wells located in intensive farming areas, levels of phosphor and pH were lower than those of wells located in extensive farming areas. Nevertheless, the range of nutrient concentration (nitrite, iron, manganese and phosphor) revealed significant statistical differences between both types of farming land; nitrite dominated in well samples located in intensive farming areas, while iron and manganese dominated in extensive farming areas. Seasonal differences were registered in temperature, nitrate, total coliforms and Escherichia coli. Maximum levels of nitrate and bacteria were reached in spring and autumn, respectively. No significant relationships were established between nutrient and bacterial levels with meteorological factors such as temperature, rainfall and number of days when rainfall occurred. Variations in nutrients and bacteria, both temporal and between locations (spatial), are associated to soil use and proximity to septic well wastewaters. Iron and manganese concentrations exceeded permitted drinking-water standards in a considerable percentage of samples, which may be due to soil composition. Bacterial pollution occurred infrequently in autumn and winter. The quality of deep-well waters in Southern Chile is generally good. Nevertheless, evidence indicates that intensive farming practices, slurry, silage and poor management of rural residential areas, constitute a significant potential risk.     

Effects of harvest regime and water depth on nutrient recovery from swine wastewater by growing Spirodela oligorrhiza

Harvest regime and water depth were investigated to determine their effects on nutrient recovery from swine wastewater by a Spirodela oligorrhiza system. The results show that harvesting less duckweed at shorter intervals favored nutrient removal and total biomass production. Harvesting 20% of duckweed twice a week led to 66.3 and 109.4% higher total nitrogen and total phosphorus removals, respectively, and a duckweed production of 20.0 g fresh biomass/m2 x d--39.6% higher than that of harvesting 80% of duckweed once every 4 weeks. The water depth of duckweed system was of great importance to total nutrient removal. At the water depth of 40 cm, total nitrogen and total phosphorus removals were 2.05 and 2.16 times higher, respectively, than those at the water depth of 10 cm. However, because of the larger amount of nutrients in a deeper system, it took a longer time for the nutrient concentrations to decrease.     

Field crops (Ipomoea aquatica Forsk. and Brassica chinensis L.) for phytoremediation of cadmium and nitrate co-contaminated soils via rotation with Sedum alfredii Hance

Environmental Science and Pollution Research - Phytoremediation coupled with crop rotation (PCC) is a feasible strategy for remediation of contaminated soil without interrupting crop production....     

Nitrogen nutrition in cotton and control strategies for greenhouse gas emissions: a review

Cotton (Gossypium hirustum L.) is grown globally as a major source of natural fiber. Nitrogen (N) management is cumbersome in cotton production systems; it has more impacts on yield, maturity, and lint quality of a cotton crop than other primary plant nutrient. Application and production of N fertilizers consume large amounts of energy, and excess application can cause environmental concerns, i.e., nitrate in ground water, and the production of nitrous oxide a highly potent greenhouse gas (GHG) to the atmosphere, which is a global concern. Therefore, improving nitrogen use efficiency (NUE) of cotton plant is critical in this context. Slow-release fertilizers (e.g., polymer-coated urea) have the potential to increase cotton yield and reduce environmental pollution due to more efficient use of nutrients. Limited literature is available on the mitigation of GHG emissions for cotton production. Therefore, this review focuses on the role of N fertilization, in cotton growth and GHG emission management strategies, and will assess, justify, and organize the researchable priorities. Nitrate and ammonium nitrogen are essential nutrients for successful crop production. Ammonia (NH₃) is a central intermediate in plant N metabolism. NH₃ is assimilated in cotton by the mediation of glutamine synthetase, glutamine (z-) oxoglutarate amino-transferase enzyme systems in two steps: the first step requires adenosine triphosphate (ATP) to add NH₃ to glutamate to form glutamine (Gln), and the second step transfers the NH₃ from glutamine (Gln) to α-ketoglutarate to form two glutamates. Once NH₃ has been incorporated into glutamate, it can be transferred to other carbon skeletons by various transaminases to form additional amino acids. The glutamate and glutamine formed can rapidly be used for the synthesis of low-molecular-weight organic N compounds (LMWONCs) such as amides, amino acids, ureides, amines, and peptides that are further synthesized into high-molecular-weight organic N compounds (HMWONCs) such as proteins and nucleic acids.     

Formation of methyl mercury in an aquatic macrophyte

In the nature, inorganic forms of mercury (Hg) may be transformed to the organic, very toxic, methyl-Hg. Occasionally methyl-Hg has been detected in plants, also so in the aquatic macrophyte water spinach (Ipomoea aquatica), which is a popular vegetable in tropical regions. The objectives of this study were to investigate if methyl-Hg is formed and/or degraded in water spinach. Water spinach plants were exposed to inorganic Hg via spiked soil or spiked nutrient solution. Tests were performed in a climate chamber and in experimental units, one for each individual plant, that were equipped with separated shoot and root compartments. Plant tissues were analysed for total- and methyl-Hg. The results showed that methyl-Hg was accumulated in water spinach, especially in young metabolically active parts, when exposed to external inorganic Hg, even at sterilized conditions. Results also showed that methyl-Hg was formed in water spinach in the absence of external Hg, i.e., during recovery in a not Hg-spiked medium following after HgCl₂-exposure. There was however, no sign of demethylation. Summarizing, most of the Hg that is taken up by the plants is bound in the roots, but of the comparatively small amounts of Hg that reach the young growing shoots, a part will be methylated. Since the young shoots of this plant make a delicious and very appreciated vegetable, Hg in I. aquatica may contribute to human health problems.     

Toxicity of tributyltin to willow trees

BACKGROUND: Tributyltin is an organotin compound, used as an antifouling agent in ship paint, with heavy impact on the marine environment. Contaminated dredged harbor sludge is now dumped on land. The toxicity of tributyltin (TBT) to trees has not yet been quantified. Eventually, a vegetation cover on the dumped sludge could be established for the purpose of non-food cash crop production and phytoremediation. METHODS: The phytotoxicity of tributyltin chloride (TBTCl) and tributyltin hydride (TBTH) was measured at pH 4 and at pH 7 using the willow tree transpiration test. Different pH levels of the nutrient solutions were achieved by adding ammonium salt (low pH) or nitrate (high pH) as nitrogen source. RESULTS AND DISCUSSION: At low pH (pH 4), all trees showed symptoms of poor health. Transpiration decreased at concentrations above or equal to 0.1 mg TBTCl/l and 1 mg TBTH/L. The TBT toxicity was more pronounced at pH 7. The trees survived even the highest dose of 10 mg/l TBTCl or TBTH, although their growth and transpiration was strongly reduced. CONCLUSION: In contrast to other organisms, TBTCl and TBTH were less toxic to higher plants. RECOMMENDATIONS AND OUTLOOK: The toxicity of TBT is no hindrance for establishing vegetation on TBT-contaminated sludge. Phytoremediation and cash crop production could be possible with suitable plants.