季铵盐类化合物(QAC)在木材防腐中的应用

主要综述了季铵盐类化合物(QAC)在用作木材防腐剂时的耐腐性、抗流失性及其与木材的结合机理等方面的研究概况,分析了实验室耐腐性和野外实验耐腐性结果不一致的原因。此外也介绍了对季铵盐进行改性处理方面的一些研究进展。     

Soil carbon distribution and quality in a montane rangeland-forest mosaic in northern Utah

Relatively little is known about soil organic carbon (SOC) dynamics in montane ecosystems of the semi-arid western U.S. or the stability of current SOC pools under future climate change scenarios. We measured the distribution and quality of SOC in a mosaic of rangeland-forest vegetation types that occurs under similar climatic conditions on non-calcareous soils at Utah State University's T.W. Daniel Experimental Forest in northern Utah: the forest types were aspen [Populus tremuloides] and conifer (mixture of fir [Abies lasiocarpa] and spruce [Picea engelmannii]); the rangeland types were sagebrush steppe [Artemisia tridentata], grass-forb meadow, and a meadow-conifer ecotone. Total SOC was calculated from OC concentrations, estimates of bulk density by texture and rock-free soil volume in five pedons. The SOC quality was expressed in terms of leaching potential and decomposability. Amount and aromaticity of water-soluble organic carbon (DOC) was determined by water extraction and specific ultra violet absorbance at 254 nm (SUVA) of leached DOC. Decomposability of SOC and DOC was derived from laboratory incubation of soil samples and water extracts, respectively.

Although there was little difference in total SOC between soils sampled under different vegetation types, vertical distribution, and quality of SOC appeared to be influenced by vegetation. Forest soils had a distinct O horizon and higher SOC concentration in near-surface mineral horizons that declined sharply with depth. Rangeland soils lacked O horizons and SOC concentration declined more gradually. Quality of SOC under rangelands was more uniform with depth and SOC was less soluble and less decomposable (i.e., more stable) than under forests. However, DOC in grass-forb meadow soils was less aromatic and more bioavailable, likely promoting C retention through cycling. The SOC in forest soils was notably more leachable and decomposable, especially near the soil surface, with stability increasing with soil depth. Across the entire dataset, there was a weak inverse relationship between the decomposability and the aromaticity of DOC. Our data indicate that despite similar SOC pools, vegetation type may affect SOC retention capacity under future climate projections by influencing potential SOC losses via leaching and decomposition.     

改性尿素硝酸铵溶液调控氮素挥发和淋溶的研究

为了提高肥料的利用率,以尿素硝酸铵溶液为原料、聚氨酸为保护剂,复合抑制剂NBPT(N-丁基硫代磷酰三胺)和DMPP(3,4-二甲基吡唑磷酸盐)为材料,开发出改性尿素硝酸铵溶液(YUL1和YUL2),研究其对华北平原夏玉米追肥过程中的氨挥发和淋溶损失的调控效果。田间试验设置6个处理:不施氮肥(CK)、农民习惯追施尿素(CN)、优化追施尿素(CNU)、优化追施尿素硝酸铵溶液(UAN)、优化追施改性尿素硝酸铵溶液(YUL1)和优化追施改性尿素硝酸铵溶液(YUL2)。采用扫描电镜和能谱仪分析相关指标变化,在夏玉米喇叭口期追施氮肥后15d内进行田间原位连续动态观测氨挥发和土壤铵态氮和硝态氮变化,并在玉米成熟期测定产量,计算经济效益。结果表明,改性尿素硝酸铵溶液清澈无杂质,流延后成膜表面光滑、致密,抑制剂在膜表面分布均匀;能谱测试膜层表面磷硫含量增高,证明复合抑制剂与尿素硝酸铵溶液达到有效融合。在同等优化施氮量下:与CNU相比, YUL1氨挥发总量显著降低19.3%, YUL2增加9.6%;与UAN相比, YUL1、YUL2分别显著降低57.3%和42.0%。与其他施氮处理相比, YUL1和YUL2夏玉米季生长中后期0～20 cm土层依然保持相对较高的氮素含量水平,夏玉米收获后土壤硝态氮含量分别比CNU高46.0%和43.4%,比UAN高45.6%和44.7%;180～200cm土层硝态氮含量显著低于其他处理。在保证产量和净收益的同时,改性尿素硝酸铵肥料显著降低了氮素的氨挥发和淋溶损失浓度,尿酶抑制剂含量相对较高的YUL1抑制氨挥发的效果更好,硝化抑制剂含量相对高的YUL2硝态氮向下淋失的风险更小。     

Nitrogen balance in a paddy field planted with whole crop rice (Oryza sativa cv. Kusahonami) during two rice-growing seasons

This paper focuses on N balance in a paddy field planted with whole crop rice (Oryza sativa cv. Kusahonami). The experiment was conducted with two treatments during two rice-growing seasons: one was fertilized with N (160 kg N ha^–1; 16N plot) and the other unfertilized (0N plot); both plots were fertilized with P and K. The N input from precipitation was 15 and 12 kg N ha^–1 in 2002 and 2003, respectively. The N input from irrigation water reached as much as 123 and 69 kg N ha^–1 in 2002 and 2003, respectively. This was because irrigation water contained higher NO₃^– concentrations ranging from 4 to 8 mg N l^–1. The N uptake by rice plants was the major output: 118 and 240 kg N ha^–1 in the 0N and 16N plots in 2002 and 103 and 238 kg N ha^–1 in 2003, respectively. N losses by leaching were 4.8–5.3 and 6.5–7.3 kg N ha^–1 in 2002 and in 2003, respectively. Laboratory experiments were carried out to estimate the amounts of N₂ fixation and denitrification. Amount of N₂ fixation was 43 and 0 kg N ha^–1 in the 0N and 16N plots, respectively. Denitrification potential was quite high in both the plots, and 90% of the N input through irrigation water was lost through denitrification. Collectively, the total N inputs were relatively large due to irrigation water contaminated with NO₃^–, but N outflow loading, expressed as leaching–(irrigation water + precipitation + fertilizer), showed large negative values, suggesting that the whole crop rice field might serve as a constructed wetland for decreasing N.     

Microbial activity and leaching during initial oak leaf litter decomposition

The decomposition of oak leaf litter was studied by means of a litterbag experiment in an oak forest in the Netherlands. The contribution of microbial activity and leaching to weight loss and element dynamics during the first 6 weeks of decomposition was investigated by means of frequent respiration measurements and extractions of the litter and by a qualitative comparison of throughfall and litter percolation water chemistry. The oak-leaf litter lost 9.3% of its initial dry weight during the first 6 weeks. In total, 90% of this observed weight loss was explained by the processes studied. About 5.9% (64% of the total) of this weight loss was attributed to microbial tespiration and 0.5% (5%) to the loss of inorganic solutes. Leaching of dissolved organic compounds was estimated to account for 2.0% (21%). The results indicated a fast leaching of K and Cl out of the fresh litter during the first 2 weeks, while Mg, Fe, Mn, Si, ortho P, and dissolved organic N were released at a much lower rate. At the same time, small amounts of H⁺, NH _inf4 ^sup+ and NO _inf3 ^sup- were retained in the litter.     

灌溉入渗条件下农田土壤水盐动态简化模型及应用

率先采用线性简化式 ,并引入优先流系数来表示计算土层下边界渗漏水流通量 ;然后导出了计算土层入渗前后土壤储水量变化公式 ,在此基础上又引入淋洗系数 ,导出了入渗前后土壤储盐量变化公式。通过对公式的讨论 ,提出了灌溉水矿化度临界方程 ,讨论了淋洗系数和优先流系数的物理意义和影响因素。本文所建模型简单适用 ,而且与田间实测灌溉水矿化度临界方程极其吻合 ,可为农田灌溉水矿化度的选择提供参考     

Longterm influence of liquid sewage sludge on the organic carbon and nitrogen content of a furrow-irrigated desert soil

Summary In this study we evaluated the impact of five annual liquid sewage-sludge applications on the organic C and N content of a furrow-irrigated desert soil. Mineralization rates showed that sludge organic matter is mineralized rapidly (65% per year). Resistant residual sludge organic matter accumulation resulted in a theoretical increase in total soil organic C of 0.013% for the single sludge rate or 0.038% for three annual applications. These small additions were not detected in sludged soils at any depth to 270 cm. Similarly, increases in total soil N were not detected at any depth. However, soluble forms of organic C and N did increase in sludged soils relative to the non-sludged soils. In addition, soluble C:N ratios decreased significantly in the sludged soils. Soluble C and N also increased with depth due to leaching. This study therefore shows that applications of liquid sludge onto desert soils could affect the status of underground aquifers with respect to nitrate pollution.     

稻田氮素淋失测定方法的研究进展

氮素淋溶是稻田氮素向周围水体迁移的重要途径,氮以NO3–-N淋溶的形式进入水体,造成的地下水污染问题越来越引起人们的关注,有关稻田氮素淋溶的损失已开展了许多研究,所采用的研究方法不一。本文总结讨论了稻田土壤氮素淋溶的常用测定方法,主要包括土壤溶液提取法、原状土柱法、土钻取样法以及计算机模拟法和同位素示踪等方法,分别对其优缺点以及应用进行了阐述;同时对计算氮素渗漏总量的方法进行了总结,主要包括水分平衡法、达西定律法、小区渗漏池法和大型原状土柱等方法,以期为稻田氮素淋溶损失的相关研究提供技术支持和科学依据。     

高产农田土壤硝态氮淋失与地下水污染动态研究

对桓台县区域农田监测研究表明,水肥管理不同的2个监测区域郭家区、李家区高产农田土体内NO_3~--N淋失迁移动态有差异,地下水污染亦不同。春天始土体内NO_3~--N含量趋于持续降低,浅层地下水NO_3~--N含量则持续升高,雨季后地下水中NO_3~--N含量尤剧烈升高,并达年内最高值,表现出农田N肥对地下水的直接污染,这可能与李家区灌溉次数多、土壤质地较轻和地下水位较浅有关。     

南极半岛海洋气候区的土壤Ⅲ.冻-融作用与水分状况

自由水活动在南极海洋性气候区土壤形成与演化过程中发挥极为重要的作用。本文对土壤自由水的来源、冻-融作用、永冻层和活动层动态以及自由水参与下的物质迁移过程等几个方面进行了论述,讨论了上述不同过程的影响因素以及土壤发生学意义,指出以土壤水形态转化和自由水活动为基础的土壤过程具有显著的微域性特点,是决定本区土壤发生类型与分布模式的重要因素之一。