秸秆和Eh对稻田土壤溶解性有机质组成及金属释放的影响

为探究秸秆添加对氧化还原条件变化下稻田土壤重金属释放的影响,本文选取典型重金属污染稻田土壤,通过微宇宙试验结合三维荧光光谱等手段,分析了土壤溶液化学性质、溶解性有机质（DOM）、金属释放之间的动态关系。结果表明：添加秸秆增加了厌氧期Fe、Mn、As、Cd等金属的释放,同时影响了DOM组成。土壤DOM中类蛋白（C3）含量在培养期总体降低（P<0.05）;类腐殖质含量呈现厌氧期上升、好氧期下降的趋势。结构方程模型（SEM）分析显示,Eh的变化与Mn和As的溶出显著负相关（路径系数分别为-0.662和-0.528,P<0.01）,同时,Eh还通过影响土壤类腐植酸C2（路径系数-0.816,P<0.01）控制As的释放（路径系数0.244,P<0.05）。因此,稻田土壤干湿交替造成的Eh变化和秸秆还田措施不仅可直接影响重金属的溶出,也可通过DOM含量和组成进一步控制其释放。     

养猪废水恶臭挥发性物质释放特征及其组分源解析

为探究猪场曝气池和出水口废水水样的恶臭挥发性物质（Malodorous Volatile Compounds,MVCs）组成和释放特征,本文采用质子转移反应质谱（PTR-MS）检测了养猪废水在实验室模拟存储过程中顶空MVCs组成,检出了含苯芳香烃、胺类、硫化物、酮类、酚类、羧酸和吲哚7类共22种MVCs。两种废水中MVCs浓度较高是氨、硫化氢、丙酮、二甲胺、甲基乙基酮、甲硫醇和丙酸等。通过臭味活度值（OAV_i）分析了两种废水的臭气组分相对贡献率,曝气池废水释放的MVCs臭味贡献度较高的是甲硫醇（28.77%）、3-甲基吲哚（19.05%）、对甲苯酚（18.45%）、硫化氢（15.05%）和二甲胺（7.15%）;而出水口液样释放的MVCs臭味贡献度较高的是对甲苯酚（47.17%）、甲硫醇（38.26%）和3-甲基吲哚（14.57%）。胺类和羧酸类物质在整个储存过程中的浓度变化较小,硫化物在所有挥发性有机物中所占的比例较低,在存放过程中浓度变化差异较小。曝气池废水中释放速率最高的MVCs是氨、丙酮和二甲胺,分别为47 928、27 μg·h^-1·m^-2和15 μg·h^-1·m^-2。主成分分析结果显示MVCs组分来源为4类,分别为含碳有机物的厌氧消化、蛋白质分解、粪浆及冲刷水中的颗粒物和动物排泄。     

A Comparison of Satellite-Derived Vegetation Indices for Approximating Gross Primary Productivity of Grasslands

Gross primary productivity (GPP) is a key component of ecosystem carbon fluxes and the carbon balance between the biosphere and the atmosphere. Accurate estimation of GPP is essential for quantifying plant production and carbon balance for grasslands. Satellite-derived vegetation indices (VIs) are often used to approximate GPP. The widely used VIs include atmospherically resistant vegetation index, enhanced vegetation index (EVI), normalized difference greenness index, normalized difference vegetation index, reduced simple ratio, ratio vegetation index, and soil-adjusted vegetation index (SAVI). The evaluation of the performance of these VIs for approximating GPP, however, has been limited to one or two VIs and/or using GPP observations from one or two sites. In this study, we examined the relationships between the nine VIs derived from the moderate resolution imaging spectroradiometer (MODIS) and tower-based GPP at five eddy covariance flux sites over the grasslands of northern China. Our results showed that the nine VIs were generally good predictors of GPP for grasslands of northern China. Overall, EVI was the best predictor. The correlation between EVI and GPP also declined from the south to the north, indicating that EVI and GPP exhibited closer relationships in more southerly sites with higher vegetation cover. We also examined the seasonal influence on the correlation between VIs and GPP. SAVI exhibited the best correlation with GPP in spring when the grassland canopy was sparse, while EVI exhibited the best correlation with GPP in summer when the grassland cover was dense. Our results also showed that VIs could capture variations in observed GPP better in drought period than in nondrought period for an alpine meadow site because of the suppression of vegetation growth by drought.     

Particulate phase polycyclic aromatic hydrocarbons in the ambient atmosphere of a protected and ecologically sensitive area in a tropical megacity

This study reports, for the first time, the profiles and source analysis of 16 US EPA priority polycyclic aromatic hydrocarbons (PAHs) associated with PM₁₀ (particulate matter with aerodynamic diameter ≤10 μm) at a protected and ecologically sensitive area – the Yamuna Biodiversity Park – located in the megacity Delhi, India. Weekly PM₁₀ sampling was carried out at this location for 1 year (2009–2010) and the annual mean PM₁₀ level was found to be ～9 times the World Health Organization limit. Seasonal variation of PAHs (range 37.2–74.0 ng m^?3) was significant with winter values being 72% and 68% higher than summer and monsoon respectively. Principal component analysis coupled with multiple linear regression identified diesel, natural gas and lubricating oil combustion (49.5%), wood combustion (25.4%), gasoline (15.5%) and coal combustion (9.6%) sources for the observed PAHs. Heavy traffic on the national highway and arterial roads and domestic emissions from suburban households in the vicinity of the park appeared to have significantly affected its air quality. A substantial portion (～55%) of the aerosol PAH load was comprised of carcinogenic species, which yielded a considerably high lifetime inhalation cancer risk estimate (8.7E?04). If considered as a conservative lower-bound estimate, this risk translates into ～211 excess cancer cases for lifetime inhalation exposure to the observed PAH concentrations in Delhi.     

Biochar composites: Emerging trends,field successes and sustainability implications

Engineered biochars are promising candidates in a wide range of environmental applications, including soil fertility improvement, contaminant immobilization, wastewater treatment and in situ carbon sequestration. This review provides a systematic classification of these novel biochar composites and identifies the promising future trends in composite research and application. It is proposed that metals, minerals, layered double hydroxides, carbonaceous nanomaterials and microorganisms enhance the performances of biochars via distinct mechanisms. In this review, four novel trends are identified and assessed critically. Firstly, facile synthesis methods, in particular ball milling and co-pyrolysis, have emerged as popular composite fabrication strategies that are suitable for large-scale applications. Secondly, biochar modification with green materials, such as natural clay minerals and microorganisms, align well with the on-going green and sustainable remediation (GSR) movement. Furthermore, new applications in soil health improvement and climate change mitigation support the realization of United Nation's Sustainable Development Goals (SDGs). Finally, the importance of field studies is getting more attention, since evidence of field success is critically needed before large-scale applications.     

Comparison of tree species effects on microbial C and N transformations and dissolved organic matter properties in the organic layer of boreal forests

The aim of this study was to determine whether tree species consistently affects soil microbial activities related to C and N cycling and to compare these activities with the characteristics of soil dissolved organic matter (DOM). Samples were taken from the mor-type organic layer (Of+Oh) underlain by podzols of six 20–72-year-old tree-species experiments on different site types in different parts of Finland. Sampling plots were dominated by silver birch (Betula pendula Roth), Norway spruce (Picea abies (L.) Karst) or Scots pine (Pinus sylvestris L., only on four sites). Amounts of C and N in the microbial biomass and rates of C mineralization (CO₂ production) and net N mineralization were determined, and water extracts were analysed for concentrations of DOC and DON and characterized according to molecular size by ultrafiltration and according to chemical composition using a resin fractionation technique. In all older stands, birch, compared to spruce or pine, increased soil pH, NH₄-concentration and amounts of C and N in microbial biomass and decreased the C-to-N ratio and ratio of dissolved organic N (DON)-to-mineral N. Birch had similar effects also in part of the younger stands. Birch also increased the rates of both C and net N mineralization compared to spruce or pine but only on two sites. In all soils, net nitrification was low. The distribution of DOC into different fractions based on chemical composition and molecular size was rather similar in all soils. The most abundant chemical fraction was hydrophobic acids, and the most abundant molecular size fraction was 10–100 kDa. The C-to-N ratio varied but was lowest in hydrophilic bases and in the smallest molecular size class. Mineralization of C was highly and positively correlated with concentration of DOC (Pearson's correlation coefficient r = 0.9, P < 0.01). The results indicated close interactions between microbial processes and dissolved organic matter.     

应用MODIS数据监测大范围病虫害植被指数变化——以2010年澳大利亚蝗灾为例

为了分析2010年澳大利亚新南威尔士州大范围蝗灾的发生范围和受灾程度,利用2008—2010年MODIS/Terra数据,通过植被生长期内前后同期的NDVI差值图像△NDVI判断2010年植被长势情况。研究结果表明:从整体上看,监测到的受灾范围与受灾程度上基本一致,能较好的反映出新南威尔士州的受灾情况;2010年9月新南威尔士州未受灾面积约为41万km2;受灾较轻区域面积约为5万km2;受灾较重区域的面积约为34万km2;受灾总面积约为39万km2,约占总面积的49%。通过与官方统计数据对比,监测到的受灾面积与官方统计数据相对误差为22%,造成误差的主要原因是像元的缺失与个别错误的像元点,导致受灾区域缺失的像元不能统计在受灾面积中和降低了受灾情况分类的精度。可得出结论,此方法适用于在对蝗灾发生范围和受灾程度的研究中。     

Quantifying production potentials of winter wheat in the North China Plain

The North China Plain (NCP) is one of the major winter wheat (Triticum aestivum L.) producing areas in China. Current wheat yields in the NCP stabilize around 5 Mg ha⁻¹ while the demand for wheat in China is growing due to the increase in population and the change in diet. Since options for area expansion of winter wheat are limited, the production per unit of area need to be increased. The objective of this study is to quantify the production potential of winter wheat in the NCP taking into account the spatial and temporal variability caused by climate. We use a calibrated crop growth simulation model to quantify wheat yields for potential and water-limited production situations using 40 years of weather data from 32 meteorological stations in the NCP. Simulation results are linked to a Geographic Information System (GIS) facilitating their presentation and contributing to the identification of hotspots for interventions aimed at yield improvements. In the northern part of the NCP, average simulated potential yields of winter wheat go up to 9.7 Mg ha⁻¹, while average water-limited yields only reach 3 Mg ha⁻¹. In the southern part of the NCP, both average potential and water-limited yields are about 7.5 Mg ha⁻¹. Rainfall is the limiting factor to winter wheat yields in the northern part of the NCP, while in the southern part, the joint effect of low radiation and high temperature are major limiting factors. Temporal variation in potential yields throughout the NCP is low in contrast with the temporal variation in water-limited yields, which is especially great in the northern part. The study calls for the collection of location-specific and disaggregated irrigated and rainfed wheat yield statistics in the NCP facilitating the identification of hotspots for improvement of current wheat yields.