成都平原氮磷化肥施用强度空间分布及影响因素分析

掌握化肥施用强度的空间分布及影响因素,对施肥的精准管理和污染防控意义重大.以往研究多限于人为因素的探讨而缺乏自然地理因素对化肥施用强度空间分布的影响分析.基于成都平原23492个点位的化肥调研数据,结合地统计学方法和地理信息系统（GIS）技术,探究该区域2010~2015年均氮和磷化肥施用强度的空间分布特征及影响因素.结果表明：①研究区2010~2015年均氮和磷化肥施用强度总体处于120~360 kg·hm^-2和60~180 kg·hm^-2的中低风险强度.高风险强度主要分布在郫都、彭州、什邡、龙泉驿和金堂等粮（果）蔬种植区,相对低值区多分布在南部和东北部;②氮和磷化肥施用强度的块金系数为66.17%和41.60%,其空间分布受结构性和随机性因素共同作用决定,呈中等空间自相关性;③人为和自然因素均对氮和磷化肥施用强度的空间分布影响显著.种植作物类型（细分类）能独立解释12.90%和25.10%的施氮和施磷空间变异,是影响氮和磷施用强度空间分布的主控因子;成土母质的重要性仅次于种植作物类型,且对于施磷强度独立解释能力约是施氮强度的3.6倍.在种植作物类型起主要决定作用时,成土母质仍深刻制约和影响研究区氮和磷化肥施用强度的空间分布.因此,进行化肥施用管理和环境风险分析时需重点考虑种植作物类型和成土母质的综合作用,在磷肥施用方面更应关注成土母质的影响.     

多菌种混合发酵转化秸秆技术的研究及应用进展

农作物秸秆是农业生产的副产品,也是一项重要的生物资源。利用微生物的广泛适应性和多功能性来转化秸秆已日益受到国内外科学研究者重视,特别是多菌种混合发酵是将秸秆纤维素转化为蛋白质、乙醇、乙酸等最具发展前景的方法。文章通过混合菌降解秸秆纤维,转化利用秸秆制蛋白饲料、燃料酒精、农用沼气等方面,对混合菌发酵转化秸秆技术的研究进展进行阐述。混合菌发酵转化秸秆已成为农业综合开发领域的一个亮点,正在朝着多元化,深层次的方向发展。     

秸秆沼气干发酵基质中微生物DNA提取方法筛选

比较了4种处理方法对从秸秆沼气干发酵基质中提取微生物总DNA纯度和产量的影响,以及添加PVP和使用试剂盒对DNA粗提液的纯化效果,试图寻找一种适用于从秸秆沼气干发酵基质中提取微生物总DNA的有效方法。结果表明:采用冻融处理和酶处理相结合的方法得到DNA提取液的A260/A230和A260/A280相对较高,与其它3种方法有显著性差异(P≤0.05);提取液中添加PVP对去除DNA粗提液中的腐殖酸有一定效果,但添加量1%⁶%的效果差异不显著;经细菌DNA纯化试剂盒纯化后A260/A230和A260/A280分别达到(1.223±0.156)和(1.737±0.120)。对吸附了磷酸盐的氢氧化钽进行解吸,当pH=12时解吸率为52.45%。研究结果表明,氢氧化钽能够有效地去除水溶液中磷酸盐的吸附剂。     

我国主要蔬菜和粮油作物的砷含量与砷富集能力比较

根据国内外文献报道,对蔬菜和粮油作物中砷的累积特点和富集能力进行总结和分析.结果表明.清洁区和污染区蔬菜的砷含量变幅分别为0.001-1.07 mg·kg-1和0.001-8.51 mg·kg-1(鲜重),均值分别为0.035 mg·kg-1和0.068 mg·kg-1不同种类蔬菜的砷含量由大到小,依次为:叶菜类>根茎类>茄果类>鲜豆类;清洁区和污染区粮油作物的砷含量变幅分别为0.001-2.20 mg·kg-1和0.007-6.83 mg·kg-1(干重),均值分别为0.081 mg·kg-1和0.294 mg·kg-1,其中水稻的砷含量显著高于小麦和玉米.从富集系数来看,叶莱类蔬菜的砷富集系数最高,芹菜、蕹菜、茼蒿、芥菜等蔬菜的抗砷污染能力较弱.粮食作物玉米的抗砷污染能力较强.与蔬菜砷限量标准(GB4810-1994)相比,我国砷污染区的蔬菜中有32.2%的样本砷含量超标,其中叶菜类和根茎类的超标率分别为47.9%和12.8%.与粮食砷限量标准(GB4810-1994)比较,我国污染区粮油作物的样本砷超标率为34.8%,其中水稻的超标率高达42.9%.玉米和小麦的超标率均高于20%.     

不同轮作模式下作物根际土壤养分及真菌群落组成特征

为研究宁夏中部干旱带不同轮作模式下土壤养分及真菌群落组成的特征,以谷子轮作大豆（MRG）、轮作籽粒苋（MRA）、轮作藜麦（MRQ）及谷子连作（CK）为对象,测定了土壤养分含量,并利用Illumina MiSeq高通量测序平台测定了土壤真菌的ITS变异区序列.结果表明,不同轮作模式对土壤养分的影响存在差异.3种轮作模式下土壤pH和电导率均有所下降,土壤全氮、全钾、全磷和有机质含量均上升,OTUs数和α多样性指数均高于连作.真菌群落组成研究结果显示,子囊菌门（Ascomycota）为4种模式下的优势菌群.聚类分析显示MRA和MRG的真菌属组成最为相似,其次是MRQ,CK与3种轮作模式相差较大.相关性分析显示,土壤养分与几种优势真菌属呈显著相关性（P<0.05或P<0.01）,土壤全氮、全钾、硝态氮和有机质含量是影响土壤真菌群落最主要的因子.主成分分析（PCA）表明,MRG轮作模式优于MRA和MRQ模式.综上所述,轮作提高了真菌群落多样性指数,改变了土壤真菌群落结构,改善了土壤肥力状况,其中以谷子与大豆轮作效果最佳,建议将谷豆轮作作为中部干旱带杂粮产业中主要的轮作模式之一进行推广.     

The dynamics of arsenic in four paddy fields in the Bengal delta

Irrigation with arsenic contaminated groundwater in the Bengal Delta may lead to As accumulation in the soil and rice grain. The dynamics of As concentration and speciation in paddy fields during dry season (boro) rice cultivation were investigated at 4 sites in Bangladesh and West Bengal, India. Three sites which were irrigated with high As groundwater had elevated As concentrations in the soils, showing a significant gradient from the irrigation inlet across the field. Arsenic concentration and speciation in soil pore water varied temporally and spatially; higher As concentrations were associated with an increasing percentage of arsenite, indicating a reductive mobilization. Concentrations of As in rice grain varied by 2-7 fold within individual fields and were poorly related with the soil As concentration. A field site employing alternating flooded-dry irrigation produced the lowest range of grain As concentration, suggesting a lower soil As availability caused by periodic aerobic conditions.     

Size distributions of aerosol and water-soluble ions in Nanjing during a crop residual burning event

To investigate the impact on urban air pollution by crop residual burning outside Nanjing, aerosol concentration, pollution gas concentration, mass concentration, and water-soluble ion size distribution were observed during one event of November 4-9, 2010. Results show that the size distribution of aerosol concentration is bimodal on pollution days and normal days, with peak values at 60-70 and 200-300 nm, respectively. Aerosol concentration is 10⁴ cm^-3. nm^-1 on pollution days. The peak value of spectrum distribution of aerosol concentration on pollution days is 1.5-3.3 times higher than that on a normal day. Crop residual burning has a great impact on the concentration of fine particles. Diurnal variation of aerosol concentration is trimodal on pollution days and normal days, with peak values at 03:00, 09:00 and 19:00 local standard time. The first peak is impacted by meteorological elements, while the second and third peaks are due to human activities, such as rush hour traffic. Crop residual burning has the greatest impact on SO₂ concentration, followed by NO₂, O₃ is hardly affected. The impact of crop residual burning on fine particles (< 2.1 μm) is larger than on coarse particles (> 2.1 μm), thus ion concentration in fine particles is higher than that in coarse particles. Crop residual burning leads to similar increase in all ion components, thus it has a small impact on the water-soluble ions order. Crop residual burning has a strong impact on the size distribution of K⁺, Cl^-, Na⁺, and F^- and has a weak impact on the size distributions of NH₄⁺, Ca²⁺, NO₃^- and SO₄^2-.     

单一重金属污染对水稻叶片光合特性的影响

以杂交稻协优818为材料，研究了Cu^2＋、Hg^2＋、Cd^2＋ 3种重金属离子对水稻叶片光合特性的影响。试验结果表明：（1）Cu^2＋在低浓度时BI起叶片叶绿素含量降低。而Hg^2＋、Cd^2＋在低浓度时。则导致叶绿素含量增加：高浓度时，3种重金属均BI起叶绿素含量降低。同时，低浓度时3种重金属离子均导致叶绿素a／b值升高：高浓度时则均引起叶绿素a／b值下降。（2）Cu^2＋、Hg^2＋、Cd^2＋对水稻叶片叶绿素的吸收光谱均无明显影响，在活体条件下并未发生卟啉环中Mg^2＋的置换。（3）Cu^2＋、Hg^2＋、Cd^2＋均引起叶片希尔反应活力降低，即重金属污染明显影响光合作用。     

作物生长和氮含量对土壤-作物系统CO2排放的影响

为探讨作物生物学特征对土壤-作物系统CO₂排放的影响,本研究基于逐步收割法和静态暗箱-气相色谱技术,以冬小麦和水稻作物为研究对象,采用盆栽和大田试验的方法,在作物生长的主要生育期原位测定了土壤-作物系统CO₂排放速率,同时测定了作物生物量和氮含量.研究结果表明:①土壤-作物系统CO₂排放在生长季内呈现动态变化,土壤-水稻系统CO₂排放高于土壤-冬小麦系统.②作物暗呼吸速率与生物量呈显著线性相关.③作物暗呼吸系数(R_d)的季节变化可以用植株氮含量来描述.冬小麦R_d与N含量的关系可用线性方程R_d=0.0124N-0.0076(R²=0.9879,p<0.001)表示;水稻R_d与N含量的关系可用二次方程R_d=0.0085N2-0.0049NR²=0.9776,p<0.001)表示.④作物根系的参与极大地促进了土壤呼吸.冬小麦生长季土壤表观呼吸CO₂平均值为247.2 mg·(m²·h)^-1 ,高于未种作物土壤1.78倍,水稻生长季为215.3 mg·(m²·h)^-1 CO₂,高于未种作物土壤的3.38倍.冬小麦根系呼吸系数大于水稻,其根际呼吸对土壤表观呼吸的贡献高于水稻.