化肥减量配施有机肥对盐碱地土壤性状及镉形态的影响

盐碱地盐分含量高,会对植物生长起抑制作用或直接造成危害,盐碱地的安全利用对保障粮食安全具有重大意义。为探讨化肥减量配施不同有机肥对盐碱地土壤性状及镉形态的影响变化特征,试验在化肥施用减量20%的基础上,设厩肥30000 kg/hm²(AM)、生物有机肥600 kg/hm²(BF)、厩肥30000 kg/hm²+生物有机肥600 kg/hm²(AM+BF)及化肥正常施用量(CK)4种施肥处理,研究不同有机肥配施对土壤性状、镉含量及形态的影响。结果表明:2020年,处理BF较CK土壤镉含量显著降低了16.99%;2021年,处理BF和AM与CK相比,土壤镉含量分别降低了14.06%和10.16%,且差异显著。2020年,与CK相比,处理BF、AM和AM+BF土壤有效态镉含量分别显著降低了67.44%、34.88%和60.47%;2021年,处理BF、AM和AM+BF与CK相比,有效态镉含量分别降低了66.67%、27.27%和51.52%,且差异显著。与CK相比,有机肥配施对土壤中镉形态的分配比例有明显影响,交换态镉降低19.34%～75.69%、有机结合态镉提高45.78%～135.22%、土壤pH提高1.06%～5.81%;阳离子交换量提高5.29%～29.11%、有机质含量提高4.35%～30.14%、土壤容重降低0.76%～9.09%、过氧化氢酶活性提高7.84%～56.02%、脲酶活性提高14.67%～29.07%、碱性磷酸酶活性提高16.54%～40.09%、微生物量碳提高8.02%～25.09%、微生物量氮提高12.28%～33.12%。综上,在盐碱土壤条件下,配施有机肥可改善土壤理化性状、生物学特性,促进土壤交换态镉向有机结合态镉的转化,达到降低土壤有效态镉的目的。     

不同土地利用方式土壤对铜、镉离子的吸附解吸特征

采用一次平衡法对Cu²⁺、Cd²⁺在城市及城郊农田、林地、草地3种土地利用方式土壤中的吸附解吸过程进行比较研究, 结果表明: Cu²⁺、Cd²⁺在3种土地利用方式土壤中的吸附量均随平衡液浓度的增加而增大, Cu²⁺、Cd²⁺在农田土壤上的吸附量均高于林地和草地土壤。分别用Langmuir和Freunlich两种等温吸附方程对吸附过程进行拟合, 3种土壤对Cu²⁺的吸附过程运用Langmuir方程拟合效果好, 而对Cd²⁺的吸附过程运用Freunlich方程拟合效果更好。Cu²⁺在3种土壤的解吸量大小顺序为农田>林地>草地, Cd²⁺在3种土壤的解吸量大小顺序为农田>草地>林地。两种离子在3种土壤中的动态吸附是个快速反应的过程, 随时间延长, 吸附反应趋于平衡。运用双常数函数方程和Elovich方程能较好地拟合重金属在土壤上的吸附动力学过程。Cu²⁺、Cd²⁺的吸附与土壤黏粒含量、有机质含量、CEC和pH均有关。     

镉污染中性土壤伴矿景天修复的硫强化及其微生物效应

田间微区试验研究了施硫(S)处理对中性镉污染农田上伴矿景天镉吸取修复效率、土壤pH、有效态镉(Cd)、有效态硫以及微生物群落变化的影响。结果发现,土壤pH值随时间和硫用量的增加而显著下降,有效态镉和有效态硫随时间和硫用量的增加而显著增加。在360 g/m_²硫处理下,伴矿景天地上部镉浓度为70.9 mg/kg,较不施硫对照(38.3 mg/kg)增加85%,耕层土壤全量镉去除率为19.4%,是对照(10.5%)的1.85倍。施硫处理150天后,土壤Thiomonas和Rhodanobacter细菌相对丰度显著高于试验前土壤和对照处理。本试验结果表明,中性土壤施加适量硫磺不仅可显著提高污染土壤中镉的生物有效性,也可通过调节与硫代谢相关的功能微生物,显著增强镉的植物吸取修复效率。     

不同改良剂对镉污染土壤中小白菜吸收镉的影响

采用盆栽试验, 研究了施用石灰、钙镁磷肥、泥炭、碱渣4种土壤改良剂对外加镉污染的赤红壤上小白菜产量、镉吸收量、土壤有效态镉及pH的影响。结果表明: 外加1 mg·kg^-1和5 mg·kg^-1镉对小白菜生物量无显著影响, 且1 mg·kg^-1镉对小白菜生长有一定的促进作用; 施用改良剂对镉污染土壤上小白菜无显著增产效果。施用4种改良剂均能降低小白菜地上部镉含量, 作用效果为石灰≈泥炭>碱渣>钙镁磷肥。不同改良剂对小白菜根部镉含量影响不同, 泥炭和石灰在所有镉浓度下、钙镁磷肥在0和1 mg·kg^-1镉浓度下可显著降低根部镉含量, 而碱渣无明显作用, 种植两茬规律一致。土壤有效态镉含量与pH呈显著负相关; 施用石灰、碱渣、钙镁磷肥使土壤pH显著升高, 有效态镉含量显著降低, 从而降低小白菜对镉的吸收; 泥炭可显著提高土壤pH, 虽降低土壤有效态镉作用效果不显著, 但显著降低小白菜体内镉含量, 这可能与土壤中形成难以被植物吸收的镉有机结合物有关。两茬蔬菜种植结果显示, 施用后期改良剂对镉污染的抑制效果也较明显。     

改良剂对镉污染酸性水稻土的修复效应与机理研究

为探明田间条件下施用石灰、钙镁磷肥、海泡石和腐殖酸等改良剂对Cd污染酸性水稻土的修复效应和作用机理, 通过在Cd污染区建立田间小区试验, 研究了改良剂单施和与石灰配施对Cd污染酸性水稻土中Cd作物有效性的影响。结果表明, 施用改良剂有效地改变了土壤中Cd的存在形态, 除腐殖酸外, 其他改良剂均使土壤酸提取态Cd不同程度地转化为可还原态Cd和残渣态Cd; 施用改良剂可使0.1 mol·L^-1 NaNO₃和 0.01 mol·L^-1CaCl₂提取态Cd 降低26%~97%, 降低效果为石灰+海泡石>海泡石>石灰+钙镁磷肥>钙镁磷肥>石灰>石灰+腐殖酸>腐殖酸; 改良剂使水稻地上部分的Cd吸收量降低6%~49%。试验结果还显示, 施用改良剂提高土壤pH是引起土壤中Cd作物有效性降低的主要原因之一。根据田间试验的结果, 海泡石可推荐作为Cd污染酸性水稻土的改良剂, 而腐殖酸则不宜使用。     

不同改良剂对重金属污染土壤中小麦镉吸收的影响

为探讨不同改良剂及用量对重金属污染土壤的修复作用和效果,采用土壤盆栽试验,研究不同改良剂(K2HPO4、鸡粪、Na2S)对小麦生物量、不同组织镉吸收量、土壤pH及土壤有效态镉含量的影响。结果表明:3种改良剂均增加了小麦籽粒和茎秆重,对小麦的生长起到了促进作用,24g/kg鸡粪(B3)处理下,小麦籽粒重和茎秆重最高;不同改良剂均可降低小麦地上部和根系镉含量,0.004 8g/kg Na_2S(C3)处理水平下,地上部和根系镉含量与对照相比分别下降了69.72%,59.42%,下降幅度最大。其中,24g/kg鸡粪(B3)处理水平下转运系数最小,对重金属从根系向地上部迁移的抑制力最强;鸡粪(B)、Na_2S(C)可显著降低小麦籽粒中的镉浓度,K2HPO4(A)对降低小麦籽粒镉浓度无显著影响,但随着用量的增加,小麦籽粒镉浓度呈现降低的趋势,3种改良剂对降低小麦籽粒镉浓度的作用效果为Na_2S鸡粪K_2HPO_4;施加改良剂增加了土壤pH,土壤有效态镉含量随改良剂用量的增加呈下降趋势,24g/kg鸡粪(B3)与对照相比下降幅度最大,达48%。     

植物吸取修复及钝化处理对后茬水稻镉吸收的影响

采集湖南湘潭县某地镉(Cd)污染酸性农田土壤及其经伴矿景天分别吸取修复两季和三季后的土壤,采用盆栽试验研究了经伴矿景天修复及钝化改良与否对土壤pH、有效态Cd、Zn以及水稻生长和稻米Cd、Zn浓度的影响。结果表明:未改良的处理,随着修复次数的增加,土壤pH显著降低,降低幅度为0.26~0.38个单位;且修复两季、三季土壤CaCl_2提取态Cd浓度较未修复土壤分别降低19.4%、24.0%;修复后土壤种植水稻品种W184,其糙米中Cd浓度显著降低,但依然超标;修复三季土壤种植低积累水稻品种IRA7190,其糙米中Cd由0.47 mg/kg降为0.03 mg/kg。施加钝化剂海泡石和石灰(10 g/kg+1 g/kg)后,修复两季、三季土壤的pH显著升高,较未施钝化剂处理土壤pH分别提高0.95、0.72;土壤CaCl_2提取态Cd浓度分别降低79.8%、79.5%;修复两季、三季土壤上水稻W184糙米的Cd浓度与未施加钝化剂相比,分别降低27.3%、44.4%,均降至国家食品安全限值0.2 mg/kg以下;无论是否添加钝化剂,伴矿景天吸取修复三季的土壤上水稻IRA7190糙米中Cd浓度均仅0.03 mg/kg。     

春大豆施钼条件下最适氮磷肥施用量研究

缺乏高效的养分管理技术体系,一直是制约永州地区富硒大豆产业发展的重要因素。为优化春大豆钼肥拌种条件下氮、磷肥运筹,提高养分利用效率和产量,以“湘春豆V8”为材料,通过大田小区试验探究不同氮肥和磷肥施用水平组合对春大豆产量和产量构成、干物质和养分累积量,以及养分利用效率的影响。结果表明,(1)单独采用钼肥拌种能显著提高大豆单株有效分枝数和荚果数,增幅分别达71.4% 和10.0%;显著提高大豆的生物产量和地上部分氮素累积量,增幅分别达17.8% 和22.9%。(2)处理MN1P2(80 g/100 kg 钼肥拌种+45 kg/hm² 尿素+300 kg/hm² 钙镁磷肥)和处理MN2P1(80 g/100 kg 钼肥拌种+75 kg/hm² 尿素+150 kg/hm² 钙镁磷肥)产量分别达2675.64 和2576.49 kg/hm²;两处理氮肥农学利用率、氮肥吸收利用率、磷肥利用率、磷利用效率分别为35.15和20.97 kg/kg、181.15% 和111.53%、14.28% 和15.94%、319.69 和450.55 kg/kg。(3)相较于当地常规施肥措施(75 kg/hm² 尿素+450 g/hm² 钙镁磷肥),MN1P2 和MN2P1 两处理施氮、磷肥减施幅度分别达40%、50% 和0%、66.7%。永州贫钼地区春大豆钼肥拌种前提下,氮、磷施用量为45 kg/hm² 尿素+300 kg/hm² 钙镁磷肥或75 kg/hm²尿素+150 kg/hm² 钙镁磷肥,可在减施氮磷肥的基础上,获得较高的产量和提高大豆养分利用率。     

水蚀条件下硝酸铵施用对黄绵土氮素流失的影响

研究结果表明不同坡度谷子地,高N处理小区径流中铵态氮、硝态氮和有效氮浓度平均为1.06、0.76和1.82mg/kg,低N分别为0.64、1.29和1.93mg/kg;高氮处理土壤铵态氮、硝态氮和有效氮平均流失量分别达到17.90、12.93和30.84kg/(km²·a),低N流失量为11.90、23.86和35.77kg/(km²·a)。高氮处理小区泥沙中有机质和全氮浓度平均为5.21和0.536g/kg,而低氮处理分别为4.94和0.481g/kg;高氮和低氮处理土壤有机质流失量分别为5702和5743kg/(km²·a),土壤全氮流失量为498和559kg/(km²·a)     

聚丙烯酰胺(PAM)对三峡库区紫色土坡面片蚀的影响

设置不同PAM施加量(0,0.4,0.8,1.6 g/m²),在不同坡度(15°,20°,25°)条件下开展不同雨强(60,90,120 mm/h)的模拟降雨试验。研究不同PAM施加量紫色土坡面片蚀产流产沙过程及其对产流产沙量的影响程度和主要因素,并分析了PAM对坡面片蚀可蚀性的影响。结果表明:坡面产流过程呈现先持续增加后趋于波动稳定的变化趋势,产沙过程则呈现先迅速减少并趋于稳定的变化趋势,PAM对片蚀的产流产沙过程变化趋势没有影响。和空白对照组相比,PAM施加量为0.4,0.8,1.6 g/m²的产流总量平均分别减小7.71%,35.16%,21.12%,产沙总量平均分别减小35.80%,49.39%,17.85%,PAM施加量为0.8 g/m²时产流总量和产沙总量最小。同种雨强下,不同施加量减流效益的大小顺序为0.8 g/m²>1.6 g/m²>0.4 g/m²,而减沙效益则受到坡度影响,在15°坡面减沙效益大小顺序是0.8 g/m²>1.6 g/m²>0.4 g/m²,在20°和25°坡面减沙效益大小顺序为0.8 g/m²>0.4 g/m²>1.6 g/m²。施加PAM能有效降低片蚀可蚀性,与空白对照组相比,施加PAM后降低效果依次为0.8 g/m²>0.4 g/m²>1.6 g/m²,片蚀可蚀性依次降低54.40%,40.94%,18.21%。     

改良剂对复垦土壤水稳性团聚体及POC和MOC的影响

为探究改良剂对煤矿复垦土壤有机碳的影响,以山西省襄垣县煤矿复垦区复恳7年的土壤为研究对象,采用田间微区的方法研究了泥炭和腐殖酸对复垦土壤及各粒级水稳性团聚体颗粒态有机碳(POC)和矿物结合态有机碳(MOC)的影响。结果表明:施用泥炭和腐殖酸均能增加复垦土壤水稳性大团聚体(>0.25 mm)含量,但6个月后,水稳性大团聚体会减少,而水稳性微团聚体(<0.25 mm)会增加,>2 mm和<0.25 mm粒级的团聚体变化较大,2种改良剂相比,腐殖酸各处理土壤大团聚体及微团聚体的变化比泥炭大。泥炭和腐殖酸均能增加复垦土壤总POC、MOC含量及各粒级水稳性团聚体中的POC、MOC含量,施用比例相同时,施用腐殖酸的土壤POC、MOC增量更大,施用泥炭6个月和1年后土壤POC含量变化分别为2.14~8.89,1.53~5.00 g/kg,施用腐殖酸6个月和1年后土壤POC含量变化分别为8.07~20.12,5.63~19.36 g/kg,施用泥炭6个月和1年后土壤MOC含量变化分别为4.84~10.51,5.41~8.08 g/kg,施用腐殖酸6个月和1年后土壤MOC含量变化分别为9.10~35.34,5.91~30.00 g/kg。但6个月后,泥炭和腐殖酸各处理土壤POC和MOC含量会减少。施用泥炭和腐殖酸会降低土壤有机碳的稳定性,不利于有机碳的储存。     

Sorption of humic acid on Fe oxides,bacteria, and Fe oxide-bacteria composites

Purpose

Sorption of humic substances on other soil components plays an important role in controlling their function and fate in soil. Sorption of humic substances by individual soil components has been studied extensively. However, few studies reported the sorption characteristic of humic substances on composites of soil components. This study aimed to investigate the sorption characteristics of humic acid on Fe oxide-bacteria composites and improve the understanding on the interaction among humic substance Fe oxide bacteria in soil.

Materials and methods

Humic acid was purchased from Sigma-Aldrich and was purified. Hematite and ferrihydrite were synthesized in the lab. Bacillus subtilis and Pseudomonas putida were cultivated in Luria-Broth medium and harvested at stationary growth phase. Batch sorption experiments were carried out at pH 5.0. Various amounts of humic acid were mixed with 20 mg of Fe oxide, bacteria, or Fe oxide-bacteria composite (oxide to bacteria of 1:1) in 10 mL of KCl (0.02 mol L^?1) to construct sorption isotherms. The effects of phosphate concentration and addition order among humic acid, Fe oxide, bacteria on the sorption of humic acid were also studied. The sorption of humic acid was calculated by the difference between the amount of humic acid added initially and that remained in the supernatant.

Results and discussion

The maximum sorption of humic acid on hematite, ferrihydrite, B. subtilis and P. putida was 73.2, 153.5, 69.1, and 56.7 mg C g^?1, respectively. The maximum sorption of humic acid on examined Fe oxide-bacteria composite was 28.2–57.2 % less than the predicted values, implying that the sorption of humic acid was reduced by the interaction between Fe oxides and bacteria. The presence of phosphate exerted negligible influence on the sorption of humic acid on bacteria while it inhibited the sorption of humic acid on Fe oxides. On Fe oxide-bacteria composites, inhibiting influences followed by promoting or weak inhibiting effects of phosphate with increasing concentration on the sorption of humic acid were found.

Conclusions

The interaction between Fe oxides and bacteria reduced the sorption of humic acid; moreover, the reduction was greater by the interaction of bacteria with ferrihydrite than that with hematite. Phosphate exerted negligible and inhibiting influence on the sorption of humic acid by bacteria and Fe oxides, respectively. On Fe oxide-bacteria composites, humic acid sorption was initially inhibited and then promoted or weakly inhibited by phosphate with increasing concentration.     

Adsorptionsisothermen als Regelgrößen beim Transport von Schwermetallen in Böden

Adsorption isotherms as regulators controlling heavy metal transport in soils The adsorption and desorption of Pb²⁺ and Cd²⁺ from equilibrium solutions with heavy metal contents up to 5000 μg/1 were determined in bulk experiments for soil samples from an acid Braunerde developed in loess loam, taken from the humic surface layer of the mineral soil (0–10 cm) and from the subsoil fairly free from organic matter (30–40 cm). Pb and Cd in solutions were determined by flameless atomic absorption spectroscopy. Pb was more strongly retained in the solid phase than Cd, and higher amounts of heavy metals were retained in the humic surface soil than in the subsoil free of organic matter. In the case of Pb adsorption/desorption showed slight hysteresis in the subsoil. The quantity/intensity (Q/I) relationships found in the experiments could be described by the Freundlich equation. The Q/I-relationships were substituted in the general transport equation. With a simulation model the transport of Pb and Cd through the soil with vertical water flow was calculated by the use of the Continuous Simulation Programming Language (CSMP). Two different cases were considered: a small, continuous increase in the heavy metal input of the soil surface, and a high, instantaneous peak input. Simulation of the transport and distribution mechanisms induced by the inputs over a period of 10 years showed strong retention of lead in the surface layer and consequently a strong damping of the concentration peak in the soil solution. In contrast, cadmium is distributed more quickly over the whole profile, yet the concentration peak in the solution phase is, too, damped considerably in the surface layer by temporary retention in the solid phase. The results of the simulation runs are in accordance with the situation in real soils where often strong accumulation of Pb is found in the top soil, while Cd is accumulated only slightly.     

生物腐植酸对露天矿排土场黑麦草生长的影响

[目的]研究生物腐植酸对露天矿排土场土壤改良效果的影响,为进一步提高露天矿排土场的土壤质量提供科学参考。[方法]通过盆栽试验,研究不同生物腐植酸含量(0~400kg/hm2)对露天矿排土场不同土地利用类型〔(刺槐(Robinia pseudoacacia)林、榆树(Ulmus pumila)林、荆条(Vitex negundo)林、农田、未复垦土地〕下黑麦草(Lolium multiflorum)生长状况的影响。[结果]刺槐土、榆树土、荆条土、农田土、未复垦土出苗率最大值分别出现在加入生物腐植酸量为200,200,300,300,200kg/hm2的试验盆;5种土壤黑麦草幼苗株高所需生物腐植酸最大量值分别为200,200,200,300,300kg/hm2;5种土壤黑麦草根系长度最大值分别出现在300,100,300,300,300kg/hm2的试验盆;而生物量最大值分别出现在加入生物腐植酸量为200,100,200,300,300kg/hm2的试验盆。随着生物腐植酸量的增加,各土地利用类型条件下种植的黑麦草出苗率、株高、根系长度、生物量均表现出先增加后减小的趋势。[结论]生物腐植酸对露天矿排土场不同土壤植物更新与生长具有剂量效应,表现为"单峰型"变化规律,体现出适量的生物腐植酸对露天矿排土场植被恢复具有促进作用。     

修复剂调控铅镉污染棉田对土壤微生物多样性的影响

为探讨重金属铅(Pb)、镉(Cd)污染下棉粕腐植酸和聚丙烯酸钾修复剂对土壤微生物多样性的影响,采用田间桶栽试验,进行了棉粕腐植酸、聚丙烯酸钾以及两者复合施用修复污染棉田土壤的研究,通过高通量测序分析了土壤微生物多样性的变化,并利用傅里叶红外光谱进行了土壤化学结构的修复响应分析。结果表明:与未施用修复剂处理相比,施用棉粕腐植酸和聚丙烯酸钾减少了表层土壤Pb、Cd含量,其中两者复合处理可分别减少62.6%和52.3%;改变了土壤微环境进而影响了土壤微生物多样性,不同处理共发现土壤细菌25个门,69个纲,149个目,273个科,442个属,其中优势菌门主要为变形菌门、酸杆菌门、芽单胞菌门和放线菌门。聚丙烯酸钾处理增加了土壤中变形菌门的相对丰度,棉粕腐植酸和复合修复处理增加了酸杆菌门和芽单胞菌门的相对丰度。由此可见,铅镉复合污染土壤中微生物多样性丰富,优势菌群相对稳定,聚丙烯酸钾和棉粕腐植酸通过改变土壤微环境进而影响菌群丰度。     

酸性农田土壤镉污染修复钝化材料筛选研究

[目的]研究0.3 mg kg-1、1.0mg kg-1、1.5 mg kg-1三种不同镉污染水平的酸性农田土壤单一或复配添加海泡石(H)、膨润土(P)、钙镁磷肥(G)、磷矿粉(L)四种钝化剂钝化镉污染的效果.[方法]采用室内培养模拟实验,添加单一纯化剂处理于开始培养后10 d、20 d、30 d,复配添加钝化剂处理于...     

Cation binding by acid-washed peat, interpreted with Humic Ion-Binding Model VI-FD

A sample of ombrotrophic peat from Moor House in northern England was extensively extracted with dilute nitric acid (pH 1) to free it of bound cations. Suspensions of the acid‐washed peat (5–30 g l^?1), prepared with different concentrations of background electrolyte (NaCl and KCl), were used to conduct batch acid–base titrations. A strong dependence of proton release on ionic strength (I) was observed, the apparent acid dissociation constant (pK_app) being found to decrease by approximately 1.0 for each tenfold increase in I. This behaviour could not be explained satisfactorily with Humic Ion‐Binding Model VI, a discrete‐site/electrostatic model of cation binding by humic substances, parameterized with data from laboratory studies on isolated samples. More success was obtained by abandoning the impermeable‐sphere electrostatic submodel used in Model VI, and instead assuming the peat to consist of aggregates with fixed internal volume, and with counterion accumulation described by the Donnan model, as proposed by Marinsky and colleagues. The fixed‐volume Donnan model (Model VI‐FD) could also approximately explain other reported results from acid–base titrations of peat, including the effects on the titrations of complexing cations (Al, Ca, Cu). Copper titrations of the Moor House sample were performed using an ion‐selective electrode, with peat suspensions in the acid pH range, at two ionic strengths, and in the presence of Al and Ca. The measured concentrations of Cu²⁺ were in the range 10^?13?10^?5 m . Model VI‐FD provided reasonable fits of the experimental data, after optimization of the intrinsic binding constant for Cu, the optimized value being close to the default value derived previously from data referring to isolated humic substances. The optimized constants for Al and Ca, derived from their competition effects, were also close to their default values. Additional experiments were performed in which the centrifugation‐depletion method was used to measure the binding of a cocktail of metals (Al, Ni, Cu, Zn, Cd, Eu, Pb) at a single pH. The model correctly predicted strong binding of Al, Cu, Eu and Pb, and weaker binding of Ni, Zn and Cd. For the strongly binding metals, the dissolved forms were calculated to be mainly due to complexes with dissolved humic matter, whereas the free ions (Ni²⁺, Zn²⁺, Cd²⁺) dominated for the weakly binding metals. Acid‐washed soil appears to provide a valuable intermediate between isolated humic substances and untreated soil for the investigation of cation binding by natural organic matter in the natural environment.     

不同改良措施下砂质土壤肥力的微形态评价——以内蒙古科尔沁沙地为例

本文以内蒙古通辽市科尔沁左翼后旗巴胡塔镇乌旦塔拉村为试验区,选取13个土壤微形态指标,利用Photoshop、土壤切片图像处理分析系统、Image-pro plus 6.0软件对土壤微形态图像进行处理,采用定性、定量相结合的方法对不同改良处理后的砂质土壤肥力进行评价,在此基础上建立了砂质土壤肥力评价的微形态指标最小数据集(MDS)。得出以下结论:与对照组单元1相比,其他各个单元的土壤结构体、粗骨颗粒等微形态特征变化不显著。单元10(黏土、有机肥、腐殖酸施加量分别为3.00×10~5、3.00×10~4、7.50×10~3 kg/hm~2)中土壤黏粒最多、基质比最大、有机物质频率最高;土壤孔隙状况以及毛管孔隙发育最好的单元分别是单元8和单元13(黏土、有机肥、腐殖酸施加量分别是单元8:1.50×105、3.00×10~4、1.125×10~4 kg/hm~2,单元13:7.50×10~4、3.00×10~4、3.75×103 kg/hm~2)。准则层指标土壤基质、土壤孔隙、有机物质、土壤结构体、粗骨颗粒的权重分别为0.336、0.253、0.203、0.124、0.084。砂质土壤肥力评价的最小数据集包括基质比、基质类型、基质颜色、毛管孔隙占比、孔隙类型、有机物质类型、粗骨颗粒平均粒径7个指标,MDS评价结果与原始评价结果呈显著的线性相关关系,因此实际评价砂质土壤肥力时,可以MDS的7个微形态指标代替原始的13个指标。     

Removal of Cu2+ and Cd2+ from Aqueous Solution by Bentonite Clay Modified with Binary Mixture of Goethite and Humic Acid

Pre-modification of bentonite clay with goethite, humic acid, and a binary mixture of goethite and humic acid reagents increased its cation exchange capacity from 95 to 105.32, 120.4, and 125.8 meq/100 g of bentonite clay, respectively. The effective pre-modification of bentonite clay with goethite, humic acid, and goethite–humic acid reagents was confirmed from their Fourier transform infrared spectra which suggested that modification was effective on the AlAlOH and Si–O sites for goethite and humic acid modification and AlAlOH for goethite–humic acid modification. The presence of 0.001 M NaNO₃ electrolyte increased the adsorption capacity of bentonite clay. Temperature was observed to favor the adsorption of Cu²⁺ and Cd²⁺ onto both the raw and modified bentonite clay samples. The goethite–humic acid-modified bentonite gave the best adsorption capacity of ≈10 and 16 mg/g at 30 and 50°C, respectively, for both metal ions. The inner sphere complexation mechanism was suggested for the adsorption of both metal ions onto the modified adsorbents. Modifying bentonite clay with a binary mixture of goethite and humic acid reduced the selectivity of bentonite clay for either Cu²⁺ or Cd²⁺. Preadsorbed goethite and humic acid on bentonite clay will further reduce the mobility of heavy metal ions in soils and in aquatic environments.