2-羟基-1,4-萘醌在土壤中降解作用和淋溶行为研究

采用室内培养法和土柱法,研究了2-羟基-1,4-萘醌在土壤中的降解作用和淋溶行为。结果表明,2-羟基-1,4-萘醌在灭菌和非灭菌土壤中的降解半衰期分别为3.47～6.98d和0.42～0.53d,且随着2-羟基-1,4-萘醌浓度增加,其降解半衰期延长。说明微生物对其降解过程起主导作用。参考POPs国际公约关于化学品持久性的定义,2-羟基-1,4-萘醌在土壤中属于易降解有机物。通过2-羟基-1,4-萘醌在土壤中的淋溶研究发现：当其添加浓度为5mg·kg-1和10mg·kg-1时,各处理土层中均未检出2-羟基-1,4-萘醌;当添加浓度为20mg·kg-1时,仅在0～10cm土层样品中检测到2-羟基-1,4-萘醌。与未老化土壤相比,2-羟基-1,4-萘醌在老化土壤中的淋溶作用减弱。     

不同种植方式下土壤和蔬菜中氨基甲酸酯类农药残留状况研究

氨基甲酸酯类农药的蔬菜残留问题随着其广泛使用受到公众的极大关注。本研究采用高效液相色谱-柱后衍生-荧光检测法分析了苏南某市4种不同种植方式下（传统菜地、露天蔬菜基地、大棚蔬菜基地和水稻田）68个蔬菜样品和32个土壤样品中10种N-甲基氨基甲酸酯类农药（涕灭威、涕灭威砜、涕灭威亚砜、杀线威、灭多威、残杀威、克百威、3-羟基克百威、甲萘威和灭虫威）的残留量，结果表明在蔬菜中检出的氨基甲酸酯农药残留水平多处于0．2～23μgkg^-1，土壤中为0．1～10μgkg^-1；土壤中3-羟基克百威和灭虫威全部检出，其最高检测浓度分别为10μgkg^-1和1．64μgkg^-1，其他农药仅有少数检出。尤其，克百威的代谢物3-羟基克百威在土壤和蔬菜样品中均全部检出，且部分蔬菜，如空心菜、茄子和芹菜中3-羟基克百威的浓度高达0．4～4．8mgkg^-1。这可能是由蔬菜对其生物利用的有效性不同造成的。此外，不同种植方式下土壤与某些蔬菜中（西红柿、辣椒和上海青）3-羟基克百威的含量间存在一定的相关性，但统计结果表明相互间的差异并不显著。     

降解菌HQ-C-01对克百威污染土壤的生物修复

在室内模拟条件下,研究了降解菌HQ-C-01(Pichia anomala)对克百威污染土壤的修复作用及其影响因素,同时研究了克百威及该菌株对土壤微生物的影响。结果表明,克百威降解率与降解菌HQ-C-01接种量呈正相关,降解菌接种量为2.09×108 CFU/g干土时,对土壤中50 mg/kg克百威10天降解率达82.89%;当降解菌接种量低于106 CFU/g干土时,降解菌对克百威的降解效果较弱。土壤含水量显著影响降解菌对克百威的降解率,含水量为600 g/kg时降解效果最好,降解率达85.32%,而当含水量低于200 g/kg时降解效果较差。在温度范围25℃~35℃降解菌对克百威都具有较好的降解效果。不同土壤pH值对降解菌的降解作用有显著影响,在pH值为7时,降解菌对土壤中50 mg/kg克百威10天降解率达85.62%,在较低和较高pH值下,降解效果较差。克百威使用对土壤菌落结构有一定的影响,对土壤真菌具有强烈刺激作用,从而使土壤微生物群落结构发生改变,而降解菌的使用可缓解克百威对土壤微生物的影响,修复受污染土壤。     

原位土壤中乙草胺降解迁移规律研究

通过原位试验,研究了乙草胺在海伦农田黑土中残留和迁移的时间特征和微生物对乙草胺的降解作用。结果显示:乙草胺按推荐量施入土壤后,在0-10cm层次微生物降解作用非常明显,使乙草胺残留显著降低,同时由于海伦黑土有机质含量高,保水能力强,因而乙草胺不易向深层移动。但连续降水显著促进乙草胺向下层土壤迁移并有所积累,因此施药初期要尽量避开此种天气,以提高乙草胺持效性并降低其生态环境风险。     

长期施肥对土壤中氯氰菊酯降解转化的影响

采用长期不同施肥处理土壤：有机肥（OM）、无机肥（NPK、PK、NK）和不施肥（CK）研究施肥对氯氰菊酯降解的影响,通过测定土壤中氯氰菊酯残留量及降解产物3-苯氧基苯甲酸生成量来确定其降解速度。结果表明：不同施肥处理对氯氰菊酯在土壤中降解有显著影响,其中在PK、CK土壤中降解较快,半衰期分别为9.6 d和10.7 d,在NK土壤中降解最慢,半衰期为15.1 d,长期施用有机肥（OM）较无机肥（NPK）降解呈增加趋势,但未达显著水平,半衰期分别为10.8 d和11.8 d。相关分析表明土壤中速效氮含量与氯氰菊酯半衰期呈显著负相关,长期偏施氮肥可提高土壤中速效氮的含量,进而能显著降低氯氰菊酯在土壤中降解速度。氯氰菊酯在OM、NPK土壤中降解较慢的原因可能是土壤高有机质含量增加了对农药的吸附,进而抑制了其降解。     

兽药磺胺二甲嘧啶在土壤中的生态行为

通过室内培养和土壤薄层层析等实验方法，研究了磺胺二甲嘧啶对土壤微生物的毒性及其在土壤中的降解、迁移特性。结果显示：在土壤磺胺二甲嘧啶浓度为1mg kg^-1时，土壤中细菌和真菌数量明显减少（p〈0．05），但随时间延长，该抑制作用变缓；磺胺二甲嘧啶在土壤中降解缓慢，持留时间久，在灭菌土和未灭菌土中的半衰期分别为223．9d和102．4d，并容易在土壤中迁移和渗漏，迁移系数R大于0．7，迁移和渗漏速度受介质pH的影响，在非中性环境下，移动和渗漏能力增强。表明磺胺二甲嘧啶是一种在土壤中不易被降解、容易迁移和渗漏到水体、对土壤微生物和水体产生危害的新型污染源。     

氯氰菊酯污染土壤的微生物修复及对土著微生物的影响

在实验室条件下,在含有氯氰菊酯的土壤中添加氯氰菊酯和3-苯氧基苯甲酸(3-PBA)降解菌CDT3(Rhodococcussp.)和PBM11(Pesudomonassp.),同时设不加菌的对照。分别于0、3、7、15、30 d取样,测定土壤中氯氰菊酯和3-PBA的残留,同时用平板计数和变性梯度凝胶电泳(DGGE)方法分析土壤微生物群落的变化。结果显示:CDT3和PBM11在土壤中协同作用能够更好地降解氯氰菊酯及其中间产物3-PBA。氯氰菊酯对土著微生物有较强的抑制作用。投加降解菌可以消除农药对土壤微生物的抑制,有助于土著微生物种群的恢复,但短期内无法改变农药对土壤微生物结构的破坏。     

冻融条件下沙丘土壤水分物理性提升的试验研究

基于乌兰敖都试验站内土壤冻融试验,探讨不同外界条件下土壤冻融作用对土壤中水分迁移的影响。结果表明:土壤冻结作用可以增加水分的迁移量,从而提高冻融层土壤水分含量,0-30cm和100-140cm深度土壤中水分迁移受冻结作用的影响比较显著,分别迁移了87.6,210.9mm,30-60cm和60-100cm深度受到的影响较小;冻融期内,稻草覆盖减小了水分向土壤上层迁移或者向下层的入渗;初始地下水埋藏较深能导致土壤水分迁移量变大。通过探究土壤冻融对水分物理性提升的影响作用,测定其提升数量,合理利用其提升的水分,改善固沙植被区浅层土壤水分条件,有利于固沙植物的生长和其他植物物种的侵入,提高固沙植被区的物种多样性,建立持久稳定的固沙植被。     

开花期补充水肥对花生田土壤水分、氮磷养分时空变化特征的影响

田间条件下,以花育22号和花育25号为试材,采用膜下滴灌方法,设置花生初花后20d灌水(WN0)、灌水施N 20kg/hm~2(WN1)和灌水施N 30kg/hm~2(WN2)处理,以田间自然降雨条件为对照,研究开花期补充水肥对0—100cm剖面土壤水分、水解性氮、速效磷(Olsen-P)和NO-3-N含量变化及迁移特征的影响。结果表明:(1)开花期灌水施肥使0—100cm土壤剖面土壤含水量均随土层深度增加而升高,利于0—60cm土层土壤含水量保持稳定;施用氮肥可使0—60cm土层土壤含水量升高滞后于不施肥处理10d左右,高量施氮处理使水分下渗速度减缓且20—40cm土层含水量变异性增大。(2)开花期灌水施氮肥提高了0—60cm土层NO-3-N含量,灌水施肥10~20d后是NO-3-N淋失迁移的风险期,其淋溶迁移时间与土壤水分同步。高量施氮肥使土壤硝态氮淋溶风险提前10d。(3)花后补充水分并施氮肥均可提高0—100cm剖面土壤水解性氮含量,不施氮肥处理使开花后60d时0—40cm土层水解氮含量降至57.4~89.6mg/kg,高量施氮使土壤水解性氮素养分向下淋溶风险增强。(4)开花后补充水分和氮肥处理均明显增加0—40cm土壤Olsen-P含量,施氮肥使磷素供应强度高峰后移20~40d。花生开花期灌水补充氮肥可使0—60cm土层土壤含水量、NO-3-N含量、水解氮含量和0—40cm土壤Olsen-P含量升高且水氮下渗速度减缓,促进水肥利用效率提高,但施氮量不应超过30kg/hm~2,以降低氮素养分淋失迁移风险。     

稻改草后土壤中DDT及其代谢产物的动态变化

用盆栽方法研究了DDT及其主要降解产物在水稻土改种草后土壤中的残留动态，比较了植黑麦草土壤与未植草土壤中DDT残留的差异。盆栽试验设计3种DDT处理浓度，分别为0、0．5、5．0mg kg^-1，每处理4次重复。研究表明，DDT的残留量随着时间的增加而不断减少，且前期降解速率比后期快。在试验的第81天，DDT浓度为0．5、5．0mg kg^-1的植草土壤中，DDT分别减少了27．24％、20．50％。比较植黑麦草和未植黑麦草土壤，p，p′-DDT残留量在试验的16d、32d、64d、81d均出现显著性差异。这可能与植物释放到根际的酶和有机分泌物能有效地促进农药降解有关。同时，DDT的代谢产物DDE随着时间的增加而逐渐增加。     

农药污染对水稻田土壤硫酸盐还原菌种群数量及其活性影响的研究

在实验室条件下 ,施用杀虫剂 (呋喃丹 )、杀菌剂 (多菌灵 )和除草剂 (丁草胺 )后 ,对黄松稻田土壤、紫色稻田土壤和红壤稻田土的硫酸盐还原细菌 (Sulfate reducingbacteria ,SRB)种群数量和硫酸盐还原活性的影响。结果表明 ,紫色稻田土壤、黄松稻田土壤和红壤稻田土的SRB种群数量和硫酸盐还原活性的范围分别为 (66 83～ 12 7 81)× 10 4 cfug- 1干土、(45 87～ 10 5 0 7)× 10 4 cfug- 1干土和 (3 81～ 61 62 )× 10 4 cfug- 1干土和S- 2 (7 14～ 11 57) μgg- 1d- 1干土、S- 2 (6 84～ 9 0 7) μgg- 1d- 1干土、S- 2 (1 91～ 6 67) μgg- 1d- 1干土 ,且稻田土SRB种群数量和土壤硫酸盐还原活性之间具有正相关性。每kg干土中加入 1mg的丁草胺或呋喃丹 ,能促进SRB的生长及其硫酸盐还原活性。 1kg干土中加入 5mg的多菌灵、50mg的丁草胺或呋喃丹 ,对SRB的生长和硫酸盐还原活性有明显的抑制作用。施用丁草胺和呋喃丹 7d时 ,多菌灵 14d时 ,对水稻田土壤的SRB种群数量和硫酸盐还原活性的抑制影响最大 ,然后逐渐减轻 ,最后显示出某种程度的促进作用     

Soil photolysis in a moisture- and temperature-controlled environment. 2. Insecticides

The photolytic degradations of imidacloprid, carbofuran, diazinon, chlorpyrifos, pyridaben, propoxur, and esfenvalerate were independently compared in both moist (75% field moisture capacity at 0.33 bar) and air-dry microbially viable soils at 5 microg/g. All compounds were applied to sandy soil except for propoxur, which was applied to sandy loam soil. Diazinon was applied to both sandy soil and sandy loam soil. The samples were exposed for up to 360 h, depending on the half-life of the compound. Moisture and temperature were maintained through the use of a specially designed soil photolysis apparatus. Corresponding dark control studies were performed concurrently. With the exception of esfenvalerate, the other compounds exhibited significantly shorter half-lives in moist soils, attributed to the increased hydrolysis and microbial activity of the moist soil. The esfenvalerate metabolism was not first order due to limited mobility in the soil because of its very low water solubility. The overall half-life for esfenvalerate was 740 h, as the percent remaining did not drop below 60%. The imidacloprid half-life in irradiated moist soil was 1.8 times shorter than in air-dry soils. However, on dry soil the photodegradation showed poor first-order kinetics after 24 h of exposure. The metabolism of carbofuran and diazinon was highly dependent on soil moisture. Carbofuran exhibited 2.2 times longer half-lives when less moisture was available in the soil. Diazinon in moist sandy soil degraded rapidly, but slowed significantly in irradiated and dark control air-dry sandy soil. Diazinon photolysis on sandy loam soil was not first order, as it attained a constant concentration of 54.9%, attributed to decreased mobility in this soil. Chlorpyrifos photolysis was 30% shorter on moist sand than on air-dry sand. Pyridaben photolyzed rapidly throughout the first 72 h of irradiation but maintained 48% through 168 h. Propoxur metabolism in moist sandy loam soil was not first order and did not degrade below 50% after 360 h of exposure, but the overall half-life was still nearly half of that on irradiated air-dry soil. Three of the compounds showed differences in metabolism patterns during exposure on moist or air-dry soil. Typically, the moist soils produced a more linear decline than that seen in the dry soils, corresponding to the susceptibility of the particular chemical to hydrolysis and/or biodegradation. Four of the eight experiments had shorter half-lives in dark control moist soils than in irradiated dry soils.     

黑土肥料长期定位试验冻土分割搬迁后土壤融合效果评价

为了明确黑土长期定位试验土壤搬迁后与新址的融合效果,以一个搬迁土块为研究对象,明确搬迁土块间的接缝处土壤与距接缝处不同距离的中心土壤在理化特性上的不同。结果表明,0~20 cm层次土体中心50 cm处的田间持水量比接缝处高5%,容重低4%,变异系数均明显高于其他层次;20~40 cm层次,土壤的固相率和容重高于其他层次,田间持水量降低,土块横切面各部位物理性质均无明显差别;剖面底部80~100 cm层次接缝处土壤松散缝处的固相率比30 cm和土体中心处低4.3%,液相率低3.1%,气相率高出7.6%,容重下降8.3%。0~40 cm土层的缝处、距缝30 cm和距缝50 cm处的孔隙率均低于40~100 cm层次,其中80~100 cm层次的孔隙率最大,20~40cm孔隙率最低为44.2%;土壤饱和导水率0~20 cm层次为35.3~38.0 cm/d,随着深度的加深呈下降趋势,均小于20cm/d;而80~100 cm层次缝处的饱和导水率值高达144.4 cm/d,是表层土壤的4倍。同一层次搬迁土块缝处与土块中心土壤速效养分无明显差别,缝处全氮含量均高于土块的其他位置,且与距缝30 cm和50 cm处的数值差异均达到显著水平(P0.05);pH随着土层的加深逐渐增大,碱解氮和土壤有机碳含量随着土层的加深而下降。长期定位土壤搬迁5 a后,深层土壤接缝处还处于疏松状态,下层土壤的融合要弱于上层土壤。     

Simultaneous gas chromatographic determination of carbofuran, metalaxyl, and simazine in soils

A method for extraction, cleanup, and simultaneous gas chromatographic detection of carbofuran, metalaxyl, and simazine in soils has been developed. Pesticide residues were extracted from soil with acetone containing 10% 0.2M HCl-KCl buffer (pH 2.0), cleaned up with methylene chloride-carbonate buffer (pH 10.7) solvent partitioning and solid-phase extraction on disposable silica gel columns, and quantitated with gas chromatography using a Supelcowax 10 megabore capillary column and a nitrogen-selective detector. Method limits of detection were 0.02 microgram/g for the 3 pesticides in surface soils (0-30 cm depths) and 0.02, 0.02, and 0.005 microgram/g in soils below 30 cm (subsoils) for carbofuran, metalaxyl, and simazine, respectively. Recoveries for carbofuran, metalaxyl, and simazine were 92.6 +/- 5.5, 93.6 +/- 5.0, and 88.4 +/- 6.7%, respectively, when soil samples were spiked with pesticide concentrations ranging from 0.02 to 2.0 micrograms/g.     

不同肥料类型对土壤酶活性与微生物数量时空变化的影响

采用等氮技术进行原状土柱法试验,研究了不同肥料类型对土壤酶活性和微生物数量时空变化的影响。结果表明,柱栽条件下,不同肥料类型对土壤酶活性和微生物数量的时空变化有明显影响。不同土壤深度脲酶和蛋白酶总活性均表现为肥料配施>有机肥>尿素;土壤脲酶活性均随土壤深度的增加而下降,0~20 cm土层的土壤脲酶活性占全生育期1.2 m土层总活性的50%以上,0~40 cm土层占79%左右,在0~20 cm和20~120 cm的土层所占比例大致相当;不同土层的脲酶活性均在拔节期达到最高;在小麦生育后期,脲酶活性在不同土壤深度表现为升高的趋势。3种肥料类型处理不同土层的蛋白酶活性均在成熟期达到最大值,其次为拔节期,在拔节期和扬花期出现峰值,在抽穗期和灌浆盛期出现低谷,其最小值出现在灌浆盛期;土壤蛋白酶在20~40 cm和80~100 cm时出现峰值,并在20~40 cm土层时活性最高。3种肥料类型处理间比较,微生物数量均表现为肥料配施>有机肥>尿素。在同一土层中的细菌数量以苗期最大;真菌数量以抽穗期最大;放线菌随着小麦生育期的推进数量逐渐增加,成熟期达最大值。在小麦不同生育时期,以20~40 cm土层中的细菌、真菌和放线菌数量最大,0~20 cm土层次之,40~120 cm土层随土层深度加深数量逐渐减少。     

浅层施肥对水稻苗期养分吸收及土壤养分分布的影响

采用盆栽土柱试验研究不同施肥深度对水稻秧苗生物量、养分吸收及土壤养分分布的影响,以期为水稻育秧合理施肥提供理论依据。结果表明:播种后10天,各处理水稻生物量无显著差异;播种后20天,施肥深度1 cm处理生物量与其他处理相比平均显著增加80.6%;播种后40天,施肥深度1 cm和5 cm处理与10 cm处理相比分别显著增加70.9%和30.7%。养分吸收结果与生物量表现一致,播种后20天,施肥深度1 cm处理秧苗氮、磷、钾素吸收量分别平均提高86.9%、156.9%和202.7%;播种后40天,施肥深度1 cm和5 cm处理与10 cm处理相比分别增加52.3%和24.8%、23.8%和20.4%、50.5%和43.1%。随着生育进程的推进,土壤有效养分含量均逐渐下降,且有向下迁移的趋势;其中施肥深度1 cm和5 cm处理0~10 cm土层中无机氮、速效磷、速效钾含量显著高于其他处理。适宜的浅层施肥明显促进水稻秧苗的生长发育,浅层施肥方式施入的速效养分主要集中于土壤上层,利于秧苗生长对养分的吸收,提高秧苗养分含量,增加养分吸收量,有利于提高养分资源利用效率。     

Impact of tillage on microbial activity and the fate of pesticides in the upper soil

The impact of two tillage systems, plow tillage (PT) and no-tillage (NT), on microbial activity and the fate of pesticides in the 0–5 cm soil layer were studied. The insecticides carbofuran and diazinon, and the herbicides atrazine and metolachlor were used in the study, which included the incubation and leaching of pesticides from untreated soils and soils in which microorganisms had been inhibited. The mineralization of ring¹⁴C labeled pesticides was studied. The study differentiated between biotic and abiotic processes that determine the fate of pesticides in the soil. Higher leaching rates of pesticides from PT soils are explaned by the relative importance of each of these processes. In NT soils, higher microbial populations and activity were associated with higher mineralization rates of atrazine, diazinon and carbofuran. Enhanced transformation rates played an important role in minimizing the leaching of metolachlor and carbofuran from NT soils. The role of abiotic adsorption/retention was important in minimizing the leaching of metolachlor, carbofuran and atrazine from NT soils. The role of fungi and bacteria in the biodegradation process was studied by selective inhibition techniques. Synergistic effects between fungi and bacteria in the degradation of atrazine and diazinon were observed. Carbofuran was also degraded in the soils where fungi were selectively inhibited. Possible mechanisms for enhanced biodegradation and decreased mobility of these pesticides in the upper layer of NT soils are discussed.     

Soil sterilization effects on root growth and formation of rhizosheaths in wheat seedlings

Sterilized soils are frequently used in experiments related to soil biology. Soil sterilization is known to alter physicochemical characteristics of soil, plant growth and community structure of the newly developed bacterial population. However, little information exists regarding soil sterilization effects on belowground processes mediated through root–microbe–soil interactions, e.g., development of rhizosheaths which significantly promote the plant growth under stress environments. The present study was conducted to elucidate effects of soil sterilization on wheat root growth and formation of rhizosheaths in relation to chemical changes caused by soil sterilization and the proportion of expolysaccharide (EPS)-producers in bacterial population recolonizing the sterilized soils. Wheat plants were grown for two weeks under greenhouse conditions either in the unsterilized soil or in soils sterilized by autoclaving (121 °C, 1 h) or by gamma (γ)-irradiation (50 kGy). While soil sterilization had no effect on the release of macronutrients, both sterilization procedures significantly increased the electrical conductivity, water-soluble carbon and DTPA-extractable Mn. Seedlings grown in sterilized soils produced higher root biomass and the rhizosheath soil (RS) mass as compared to those grown in the unsterilized soil. Soil sterilization also increased the root length, surface area, volume and number of tips. In bulk soil, RS and on roots, the proportion of EPS-producers in the total bacterial population was higher in sterilized treatments than in the unsterilized. Amending the unsterilized soil with glucose-C increased the root biomass, whereas adding Mn II increased the RS mass. The results showed that soil sterilization by autoclaving or γ-irradiation increases the root growth and RS mass of wheat seedlings. The water-soluble C and DTPA-extractable Mn released upon sterilization, and the increased proportion of EPS-producers in the bacterial population recolonizing the sterilized soils were involved in the observed effects. The results may have implications in studies using autoclaved or γ-irradiated soils to investigate soil–plant–microbe interactions and signify the need to account for intrinsic stimulatory effects of soil sterilization.     

天山北坡林沿土壤养分含量的区域差异特征研究

以天山北坡为研究区域, 采用野外调查与试验分析相结合的方法, 选取5个土壤养分指标: 有机质、速效氮、速效磷、速效钾和总盐, 应用多元统计分析方法, 分析了天山北坡3个区段(昭苏-特克斯、新源-巴音布鲁克、巴里坤-伊吾)林沿土壤不同层位(0~5 cm、5~20 cm、20~40 cm)养分含量的分布特征及差异性。结果表明: 天山北坡西段(昭苏-特克斯、新源-巴音布鲁克)土壤养分含量比天山北坡东段(巴里坤-伊吾区域)高。3个区段不同深度土壤有机质、速效氮、速效磷、速效钾含量均存在明显差异, 其中0~5 cm土层有机质、速效氮、速效磷、速效钾的平均含量均比5~20 cm、20~40 cm高; 5~20 cm土层有机质、速效氮、速效磷、速效钾的平均含量均比20~40 cm高; 总盐含量不具有明显的垂直分层现象。按全国第2次土壤普查标准, 天山北坡3个区段土壤均属肥沃级。昭苏-特克斯区段、新源-巴音布鲁克区段0~5 cm、5~20 cm、20~40 cm土壤养分各指标含量变化具有一定的规律, 而巴里坤-伊吾区段土壤养分各指标含量变化具有良好的独立性。天山北坡西段(昭苏-特克斯、新源-巴音布鲁克)植被类型较多, 植被覆盖度较高, 土壤较为肥沃, 大部分区域为夏牧场, 人类活动以放牧为主, 对该区段土壤要防止过度放牧所造成的植被退化与水土流失。天山北坡东段(巴里坤-伊吾)因土壤中砾石较多, 植被类型较少, 植被覆盖度较低, 人类活动包括放牧、林业种植与旅游, 与西段相比东段土壤的养分含量较低, 所以应以保持生境原貌为主, 避免人为扰动后的生境退化。     

开封黑岗口引黄灌区稻麦轮作下农田土壤剖面重金属分布特征

引黄灌区是我国重要的农业生产基地,其土壤重金属赋存状况直接关系到农业的可持续发展。本研究以黑岗口引黄灌区开封北郊稻麦轮作下农田土壤为研究对象,采集了耕作层(0~15 cm与15~30 cm)与剖面(0~100 cm)土壤样品,对其土壤剖面主要性质与重金属Pb、Cd、Cu和Zn的积累特征进行了分析。结果表明:(1)长期引黄灌溉及稻麦轮作下,开封北郊农业土壤主要性质在剖面上表现出明显的分异特征:总有机碳(TOC)与全氮(TN)含量主要分布在耕作层土壤,而30 cm以下的土层其含量明显降低;全磷(TP)含量在各土壤层中无明显差异;在部分土壤剖面中CaCO3呈现出明显的淀积层。(2)耕作层(0~30 cm)土壤中重金属Pb、Cu、Zn的含量与研究区背景值相当,而Cd含量显著高于背景值。除少部分剖面含量超标外,Cd、Pb、Cu、Zn的平均含量均未超出WHO限值,且远低于我国农业土壤环境质量标准。因子分析源解析表明:引黄灌区土壤中Pb、Cu和Zn具有相似的来源和迁移特性,而Cd的来源和迁移特性具有特殊性,它可能与当地的化肥施用等农业活动有关。(3)土壤剖面中Cu和Zn具有明显的表聚现象,Pb的表聚作用不明显,而Cd在剖面各层土壤含量具有较大变异性,这与重金属的自身属性、土壤剖面性质和当地的耕作条件有较大相关性。(4)Cu和Zn在土壤剖面主要以有机结合态和残余态形式存在;Pb的残余态、有机态以及铁锰氧化态含量也较高,且Pb的全量与有机结合态含量百分比变化呈现出一定的相似性;而Cd具有较高的碳酸盐结合态和离子交换态,表明Cd在土壤中具有较强的移动性,预示Cd的潜在健康风险较高。