BS-CTMAB复配修饰膨润土对苯酚的吸附

采用两性表面修饰剂十二烷基二甲基甜菜碱(BS-12)和阳离子表面修饰剂十六烷基三甲基溴化铵(CTMAB)复配修饰膨润土,通过批处理法研究了不同修饰比例、温度、pH和离子强度等条件下,复配修饰膨润土对苯酚的吸附规律和热力学特征,并探讨了其吸附机制。结果表明,CTMAB复配修饰显著增强了两性修饰膨润土对苯酚的吸附能力,30℃时吸附量呈现100BS+100CT(100%BS-12+100%CTMAB)100BS+50CT(100%BS-12+50%CTMAB)50BS+100CT(50%BS-12+100%CTMAB)100BS+150CT(100%BS-12+150%CTMAB)50BS+50CT(50%BS-12+50%CTMAB)100BS+25CT(100%BS-12+25%CTMAB)50BS+150CT(50%BS-12+150%CTMAB)50BS+25CT(50%BS-12+25%CTMAB)100BS(100%BS-12)50BS(50%BS-12)CK(原土)的顺序。当CTMAB复配修饰比例在0~100%CEC时,两性复配修饰土样对苯酚的吸附量随着修饰比例的增大而升高,而在100%~150%CEC阶段,吸附量则随CTMAB修饰比例的增大有所降低;修饰土样对苯酚吸附量随着温度、pH的升高而降低,在低浓度范围内,随着离子强度的增大而升高。Henry模型适用于描述苯酚在供试土样的吸附,供试土样对苯酚的吸附属于自发的物理吸附过程,吸附呈现焓减、熵增特征。     

Combining rhizosphere and soil-based P management decreases the P fertilizer demand of China by more than half based on LePA model simulations

Phosphorus (P) is a finite natural resource and is increasingly considered to be a challenge for global sustainability. Agriculture in China plays a key role in global sustainable P management. Rhizosphere and soil-based P management are necessary for improving P-use efficiency and crop productivity in intensive agriculture in China. A previous study has shown that the future demand for phosphate fertilizer by China estimated by the LePA model (legacy phosphorus assessment model) can be greatly reduced by soil-based P management (the building-up and maintenance approach). The present study used the LePA model to predict the phosphate demand by China through combined rhizosphere and soil-based P management at county scale under four P fertilizer scenarios: (1) same P application rate as in 2012; (2) rate maintained same as 2012 in low-P counties or no P fertilizer applied in high-P counties until targeted soil Olsen-P (TP_Olsen) level is reached, and then rate was the same as P-removed at harvest; (3) rate in each county decreased to 1–7 kg ha^–1 yr^–1 after TP_Olsen is reached in low-P counties, then increased by 0.1–9 kg ha^–1 yr^–1 until equal to P-removal; (4) rate maintained same as 2012 in low-P counties until TP_Olsen is reached and then equaled to P-removal, while the rate in high-P counties is decreased to 1–7 kg ha^–1 yr^–1 until TP_Olsen is reached and then increased by 0.1–9 kg ha^–1 yr^–1 until equal to P-removal. Our predictions showed that the total demand for P fertilizer by whole China was 693 Mt P₂O₅ and according to scenario 4, P fertilizer could be reduced by 57.5% compared with farmer current practice, during the period 2013–2080. The model showed that rhizosphere P management led to a further 8.0% decrease in P fertilizer use compared with soil-based P management. The average soil Olsen-P level in China only needs to be maintained at 17 mg kg^–1 to achieve high crop yields. Our results provide a firm basis for government to issue-relevant policies for sustainable P management in China.     

稻壳生物炭对矿区重金属复合污染土壤中Cd、Zn形态转化的影响

明确稻壳生物炭的农业生态效应对合理利用其修复矿区重金属复合污染土壤具有重要意义。通过盆栽试验,研究了稻壳生物炭不同施用量(0、5、10、20、50、100 g·kg~(-1))对重金属复合污染土壤p H、CEC和Cd、Zn赋存形态转化的影响。结果表明:与对照相比,稻壳生物炭的添加使土壤p H升高0.18~0.29个单位,CEC提高32.89%(5.68 cmol·kg~(-1));同时,重金属复合污染土壤中弱酸提取态Cd、Zn分别降低21.88%、19.63%,氧化态Cd、Zn分别降低24.12%、18.62%,可还原态Cd、Zn分别降低13.72%、8.97%;而使残渣态Cd、Zn分别升高115.56%、39.45%。综上所述,稻壳生物炭的添加提高了矿区重金属复合污染土壤的p H和CEC,促进了重金属复合污染土壤中Cd、Zn的弱酸提取态、可氧化态和可还原态向化学性质稳定的残渣态转化,降低了土壤重金属的有效性,实现了对重金属复合污染土壤的修复。     

渭北旱塬不同耕作措施对土壤养分分布及作物产量的影响

基于8年(2007—2015)定位试验,在小麦-玉米轮作下研究了免耕-深松(NS)、深松-翻耕(SC)、翻耕-免耕(CN)和连年免耕(NN)、深松(SS)、翻耕(CC)等轮耕措施对土壤养分分布及作物产量的影响。结果表明:深松处理(连年深松、免耕-深松)使表层(0~10 cm)土壤与底层(10~20、20~35、35~50 cm)土壤有机质、全氮、全磷、速效磷、速效钾等养分含量差异更大,翻耕或免耕的相对差异较小;在0~50 cm的土层中,硝态氮含量在20~35 cm土层相对较高,且以翻耕(CC)处理的含量最高;铵态氮含量在10~20 cm土层相对较高,以免耕-深松(NS)处理的含量最高;连年深松(SS)处理使土壤全钾表层含量较高。免耕-深松(NS)措施在6种耕作措施中小麦和玉米产量均为最高,显著高于翻耕(CC)、免耕(NN)措施。     

Trends of Yield and Soil Fertility in a Long-Term Wheat-Maize System

The sustainability of the wheat-maize rotation is important to China＇s food security. Intensive cropping without recycling crop residues or other organic inputs results in the loss of soil organic matter （SOM） and nutrients, and is assumed to be non- sustainable. We evaluated the effects of nine different treatments on yields, nitrogen use efficiency, P and K balances, and soil fertility in a wheat-maize rotation system （1991-2010） on silt clay loam in Shaanxi, China. The treatments involved the application of recommended dose of nitrogen （N）, nitrogen and phosphorus （NP）, nitrogen and potassium （NK）, phosphorus and potassium （PK）, combined NPK, wheat or maize straw （S） with NPK （SNPK）, or dairy manure （M） with NPK （M1NPK and M2NPK）, along with an un-treated control treatment （CK）. The mean yields of wheat and maize ranged from 992 and 2 235 kg ha-1 under CK to 5 962 and 6 894 kg ha-1 under M2NPK treatment, respectively. Treatments in which either N or P was omitted （N, NK and PK） gave significantly lower crop yields than those in which both were applied. The crop yields obtained under NP, NPK and SNPK treatments were statistically identical, as were those obtained under SNPK and MNPK. However, M2NPK gave a significant higher wheat yield than NP, and MNPK gave significant higher maize yield than both NP and NPK. Wheat yields increased significantly （by 86 to 155 kg ha-1 yr-1） in treatments where NP was applied, but maize yields did not. In general, the nitrogen use efficiency of wheat was the highest under the NP and NPK treatments; for maize, it was the highest under MNPK treatment. The P balance was highly positive under MNPK treatment, increasing by 136 to 213 kg ha-1 annually. While the K balance was negative in most treatments, ranging from 31 to 217 kg ha^-1 yr^-1, levels of soil available K remained unchanged or increased over the 20 yr. SOM levels increased significantly in all treatments. Overall, the results indicated that combinations of organic manure and inorganic nitrogen, or retuming straw with NP is likely to improve soil fertility, increasing the yields achievable with wheat-maize system in a way which is environmentally and agronomically beneficial on the tested soil.     

外加碳酸盐增加石灰性土壤密闭培养过程中CO2的释放量

The closed-jar incubation method is widely used to estimate the mineralization of soil organic C. There are two C pools (i.e., organic and inorganic C) in calcareous soil. To evaluate the effect of additional carbonates on CO2 emission from calcareous soil during closed-jar incubation, three incubation experiments were conducted by adding different types (CaCO3 and MgCO3 ) and amounts of carbonate to the soil. The addition of carbonates significantly increased CO2 emission from the soil; the increase ranged from 12.0% in the CaCO3 amended soil to 460% in the MgCO3 amended soil during a 100-d incubation. Cumulative CO2 production at the end of the incubation was three times greater in the MgCO3 amended soil compared to the CaCO3 amended one. The CO2 emission increased with the amount of CaCO3 added to the soil. In contrast, CO2 emission decreased as the amount of MgCO3 added to the soil increased. Our results confirmed that the closed-jar incubation method could lead to an overestimate of organic C mineralization in calcareous soils. Because of its effect on soil pH and the dissolution of carbonates, HgCl2 should not be used to sterilize calcareous soil if the experiment includes the measurement of soil CO2 production.     

Response of Stream Water Chemistry to Rainwater Acidification in Natural Forest Region of Qinling Mountains

This study was conducted in the Huoditang naturally-regenerated forest,which is located at the center of the natural forest region across the southern-slope of the Qinling Mountains. Rainwater and stream water samples were collected mainly in rainy seasons in the area.The sample pH values and chemical concentrations were measured. The response of stream water chemistry to rainwater acidification in the region was studied.The results showed that long time rainwater acidification could result in reduction of pH value,Ca²⁺ and Mg²⁺ concentration in the stream water.The changes of K⁺,Na⁺ concentration of stream water were not correlated with the rainwater acidification.There was no response of Zn,Pb and Cd concentration of the stream water to rainwater acidification.The acidified rainwater did not result in the release of the heavy metals enriched in the forest soil.     

作物营养从有机肥到化肥的变化与反思

二十世纪前，农业生产主要靠施用有机肥为作物提供营养，维持地力不衰，这一时期一般称为“有机营养”阶段。之后，化肥逐渐取代有机肥，成为作物养分的主要来源，农业生产进入以化肥养分供应为主的“无机营养”阶段。化肥的连续大量施用在作物增产方面发挥了巨大作用，也带来了不少问题，以致近年来出现了怀疑或否定农业生产中施用化肥的思潮。为此，本文回顾了植物营养学科的发展历程和我国化肥使用的历史，指出仅靠施用有机肥、种植豆科作物等传统的营养作物的方式难以满足农业生产对养分的需求，化肥与有机肥配合施用是我国农业发展的正确道路。目前生产中，化肥施用存在不合理和过量问题，有机肥施用方面，主要是集约化养殖业与种植业的不合理布局，存在种养分离，难以农业利用等养分管理问题。同时解决这两个问题，除采取已有的合理施肥技术及方法外，还应改变从植物营养角度只重视氮磷钾等无机养分的供应，拓宽为重视碳、氮、磷及钾等不同元素间的时空平衡关系；以农业生态系统养分资源高效循环利用为核心，采取不同方式实现有机–无机营养的结合，应避免陷入有机与无机营养的争论；从生物地球化学循环角度看待养分利用与管理问题，关注养分在田块、流域及区域尺度的流向及对土壤、水体及大气的影响；将科技与政策等有效结合，提高养分利用效率，减少养分损失，保障我国农业的健康持续发展。     

冬小麦叶角质层组分对菲和芘的吸附及影响

冬小麦叶面吸收多环芳烃（Polycyclic aromatic hydrocarbons,PAHs）途径内在机制及影响因素尚不清晰。本研究采用化学分离法将冬小麦叶角质层分为7个不同组分,通过比较不同角质层组分对菲和芘吸附的影响,揭示角质层分离组分的组成和结构对菲（Phenanthrene,PHE）和芘（Pyrene,PYR）吸收的作用机制。结果表明：冬小麦叶角质层中除可提取脂质蜡质外,还含有丰富的聚合脂质角质,其含量是蜡质的1.3倍。角质层中被糖类包裹的角碳并非连续分布,而角质则连续分布。角质层各组分元素组成存在较大差异,其非极性组分主要是角质,极性组分主要是糖类。冬小麦角质层4种组分对PHE的相对吸附系数大小顺序为：角碳>角质>角碳-糖类复合体>蜡质,对PYR的相对吸附系数大小顺序为：角质>角碳>角碳-糖类复合体>蜡质。这可能是由于角碳中芳香碳较为丰富,更易与PHE和PYR发生特殊的π-π吸附作用,而角质中含有较高水平的无定形石蜡,为PHE与角质中的柔性长烷基链基团之间的疏水作用提供了分配介质,由于蜡质含量较低,表现出较低的吸附系数。此外,角质层组分吸附系数与碳含量呈正线性相关,而与氧含量、极性指数呈显著负线性相关。研究表明,角碳和角质是PAHs的主要存储介质,由于角质层蜡质含量较低（9.6%）,蜡质组分对PAHs的吸附贡献最低。角质层组分碳含量越高,其对PAHs的吸附能力越强,而角质层组分氧含量和极性指数越高,其对PAHs的吸附能力越弱。     

基于猕猴桃树体养分携出量确定果园合理施肥量——以周至县俞家河流域为例

为定量年生长周期内猕猴桃树体各器官养分含量及养分携出量,确定猕猴桃果园年养分需求量和合理施肥量,在猕猴桃年生长周期内采集秦美、哑特和华优3个品种猕猴桃树体各器官样品,测定养分含量,计算养分携出量。同时在参照研究区成龄果园树体养分贮藏量的基础上,通过果园养分吸收量推算猕猴桃果园合理施肥量。结果表明:不同品种猕猴桃果实产量、单果质量、单叶质量及叶个数、枝条修剪量间均没有显著差异,各器官氮(N)、磷(P)、钾(K)养分含量亦无显著差异。猕猴桃果园每生长1 kg叶片吸收的养分量为N 2.81 g、P 0.31 g、K 2.13 g;每收获1 kg鲜果移出的养分量为N 1.40 g、P 0.47 g、K 2.23 g;每修剪1 kg枝条移出的养分量为N 3.70 g、P 0.47 g、K 2.94 g。年生长周期内果园因叶片吸收、果实收获、枝条修剪和树体贮藏的总养分量为N 162kg·hm~(-2)·a~(-1)、P 36 kg·hm~(-2)·a~(-1)、K 146 kg·hm~(-2)·a~(-1),其中来自肥料的养分为N 38.0 kg·hm~(-2)·a~(-1)、P 5.4 kg·hm~(-2)·a~(-1)、K 20.0 kg·hm~(-2)·a~(-1)。研究表明,不同品种成龄猕猴桃果园的推荐施肥量均为N 380 kg·hm~(-2)·a~(-1)、P 77 kg·hm~(-2)·a~(-1)、K 87 kg·hm~(-2)·a~(-1),N∶P_2O_5∶K_2O为1∶0.5∶0.3。