Production and emission of phosphine gas from wetland ecosystems

Phosphine is a part of an atmospheric link of phosphorus cycle on earth, which could be an important pathway for phosphorus transport in environment.Wetland ecosystems are important locations for global biogeochemical phosphorus cycle.In this study, production and emission fluxes of free phosphine from four wetlands types in southern China were observed in different seasons.The results showed that the concentration of phosphine liberated from wetlands was at pg/m3-ng/m3 level.The emission concentrations of different wetlands followed the sequence:paddy field(51.83 ± 3.06) ng/m3 marsh(46.54 ± 20.55) ng/m3 lake(37.05 ± 22.74) ng/m3 coastal wetland(1.71 ± 0.73) ng/m3, the positive phosphine emission flux occurred in rice paddy field(6.67 ± 5.18) ng/(m2·hr) and marsh(6.23 ± 26.9) ng/(m2·hr), while a negative phosphine flux of(-13.11 ± 35.04) ng/(m2·hr) was observed on the water-air interface of Lake Taihu, suggesting that paddy field and marsh may be important sources for phosphine gas in atmosphere, while lake may be a sink of atmospheric phosphine gas during the sampling period.Atmospheric phosphine levels and emission flux from Yancheng marsh and rice paddy field varied in different seasons and vegetational zones.Both diffusion resistance in aqueous phase and temperature were dominating factors for the production and transportation of phosphine to atmosphere.     

丹江口水库入库河流总氮通量监测

针对丹江口水库总氮超标问题,对作为主要集水区的汉库入库各河流进行了一整年的水量和水质同步监测。结果表明:(1)主要河流入汉库总氮量共24503t/a,湖北和陕西两省入库总氮量比例总体上与水资源量比例相当,其中,汉江干流上游陕西来水入库总氮量占68.2%,湖北主要支流包括十堰堵河(18%)、神定河(7%)、泗河(4%)、官山河(0.9%)、浪河(0.7%)剑河(0.5%)和天河(0.5%)。(2)入汉库总氮总量月变化与入库总水量变化一致,总氮入库量主要集中在5~9月,占全年的77%。(3)根据各河流水环境容量和纳污特征,可将入库河流划分为容量型、点源污染型、农业面源型和混合型等四种类型。建议对不同类型河流应采取不同控制对策,点面结合,综合防治。     

稻鸭复合系统的温室气体排放及其温室效应

利用密闭箱技术和碱液吸收法.通过田间试验研究了稻鸭复合系统土壤CH4、N2O和CO2的排放规律及其温室效应.结果表明:①在水稻生长期间,CH4分别在分蘖期和抽穗期出现2个排放高峰.平均排放通量养鸭处理为(7.68±0.74)mg·m-2·h-1.常规淹水稻田(对照)为(9.53±0.40)mg·m-2·h-1;N2O排放通量呈现出在稻田淹水期间保持较低值,在稻田落干后迅速升高的趋势,平均排放通量养鸭处理为(0.092±0.073)mg·m-2·h-1,对照为(0.082±0.074)mg·m-2·h-1;而CO2的排放则在分蘖期和成熟期田面水逐渐落干后呈现2个排放峰,养鸭处理和对照的平均排放通量分别为(121.20±4.21)mg·m-2·h-1和(107.53±3.92)mg·m-2·h-1.②稻田养鸭显著地降低了CH4的排放.水稻整个生育期间排放量为18.41 g.m-2,比对照减少19.3%;而显著地提高了N2O的排放,整个生育期间排放量为0.2 g·m-2,比对照增加了10%;养鸭稻田土壤CO2的总排放量为273.66 g·m-2,对照为245.73 g·m-2,两者之间没有显著性的差异.③CH4是引起稻田温室气体综合温室效应的主体,其贡献率在60%左右,相对于常规稻作,稻田养鸭能有效降低甲烷的温室效应,使其温室气体的综合温室效应显著降低.说明在中国南部稻鸭共作是一个减缓全球温室效应的可行措施.     

预臭氧化对MF膜处理黄浦江水的影响研究

采用预臭氧化处理黄浦江原水后进行微滤（MF）膜过滤试验,考察预臭氧化对有机物的作用,进而考察其对MF膜过滤特性的影响.结果表明,臭氧投量在0.5～3.0 mg/Ｌ范围内时,臭氧对DOC的去除率最高仅为10%,而对UV254的去除率最高可达71%.随着臭氧投量的增加,相对分子质量在2×10³～7×10³的有机物逐渐减少,而相对分子质量＜0.5×10³的有机物则几乎没有改变.臭氧可把部分疏水性有机物氧化成亲水性有机物,只有很少部分转变成无机物,这种有机物组成结构的改变影响了膜过滤阻力,进而改善了膜透水通量的效果.臭氧投量在0.5～3.0 mg/Ｌ范围内,存在一个最佳的臭氧投量1.5 mg/Ｌ,使膜通量达到最大值.这主要是由于在该臭氧投量下,臭氧化对有机物的组成结构的改变使膜过滤阻力达到最小.     

Distribution and deposition of polycyclic aromatic hydrocarbons in precipitation in Guangzhou, South China

Polycyclic aromatic hydrocarbons (PAHs) were measured in precipitation from March to August 2005 in Guangzhou, South China. Fourteen PAHs were studied, and their total concentrations varied from 616.6 to 3486.7 ng/L in dissolved phase and from 403.8 to 3125.5 ng/L in particulate phase. The estimated deposition loading of PAHs was 3568 μg/m2 during the monitoring period. The deposition of PAHs was a potential source for Pearl River comparing with the contents of surface water. In addition, the high concentra...     

香溪河库湾夏季温室气体通量及影响因素分析

采用LGR-密闭式动态通量箱法对三峡水库香溪河库湾夏季水-气界面温室气体(CO2和CH4)通量进行了24 h连续观测.结果表明,观测点处水-气界面CO2和CH4的释放通量具有明显的日变化特征,且二者的日变化过程呈较强的负相关性.监测期间,CO2的吸收和释放过程明显,CH4全天均为释放状态,其全天平均通量分别为0.336 mg.(m2.h)-1和0.088mg.(m2.h)-1.分析发现,水-气界面碳通量与温度、pH、叶绿素a、气压、辐照强度的相关性明显,而Eh对碳通量的影响并不显著,其中,CO2与各环境因子的相关性较CH4更为密切.     

大辽河口痕量元素砷的河口混合行为

研究了大辽河口痕量元素砷的河口混合行为.分别于2010年4、7、11月从大辽河口采集20个站位,采用氢化物发生原子荧光光谱法测定了溶解态砷的含量,目的是探讨大辽河口砷的来源及其分布的影响因素.大辽河口4、7、11月砷含量的变化范围分别为2.98～44.1、1.19～14.6、1.27～12.4μg.L-1;4月含量最高,7月次之,11月最低.不同季节其行为差别很大,7月其行为是保守的;4、11月在整个盐度范围其行为是非保守的,但在盐度1～30、10～30之间是保守的.不同季节河流砷的输送通量差异不大,4月起通量主要受砷浓度控制,11月主要由流量控制,7月由两者共同控制.7月河口通量主要来自于河流的输送,4、11月则主要来自河口内部.同世界上其他河口相比,大辽河口砷的含量处于较高的水平.     

污染河口区沉积物-水界面营养盐交换通量的实验研究

采集青岛市李村河口下游沉积物柱状样品,通过实验室培养实验,研究了溶解氧、温度、盐度、生物扰动等环境因素对沉积物-水界面营养盐交换通量的影响。结果表明,NO3-N、NH4-N、PO4-P在贫氧环境下的交换通量要高于富氧条件下,NO2-N受溶解氧含量的影响较小;随着温度的升高,NO3-N、NH4-N、PO4-P的交换通量增大,而NO2-N的交换通量减小;NO2-N和NH4-N的交换通量随盐度增大而增大,NO3-N减小,而PO4-P受盐度的影响较小;生物扰动对营养盐在沉积物-水界面的交换通量的影响显著。     

Elevated atmospheric CO2 and drought effects on leaf gas exchange properties of barley

Atmospheric CO₂ concentration (C_a) is rising, predicted to cause global warming, and alter precipitation patterns. During 1994, spring barley (Hordeum vulgare L. cv. Alexis) was grown in a strip-split-plot experimental design to determine the effects that the main plot C_a treatments [A: Ambient at 370 μmol (CO₂) mol⁻¹; E: Enriched with free-air CO₂ enrichment (FACE) at ∼550 μmol (CO₂) mol⁻¹] had on several gas exchange properties of fully expanded sunlit primary leaves. The interacting strip-split-plot irrigation treatments were Dry or Wet [50% (D) or 100% (W) replacement of potential evapotranspiration] at ample nitrogen (261 kg N ha⁻¹) and phosphorous (29 kg P ha⁻¹) fertility. Elevated C_a facilitated drought avoidance by reducing stomatal conductance (g_s) by 34% that conserved water and enabled stomata to remain open for a longer period into a drought. This resulted in a 28% reduction in drought-induced midafternoon depression in net assimilation rate (A). Elevated C_a increased A by 37% under Dry and 23% under Wet. Any reduction in A under Wet conditions occurred because of nonstomatal limitations, whereas under Dry it occurred because of stomatal limitations. Elevated C_a increased the diurnal integral of A (A′) that resulted in an increase in the seasonal-long integral of A′ (A″) for barley leaves by 12% (P = 0.14) under both Dry and Wet - 650, 730, 905 and 1020 ± 65 g (C) m⁻² y⁻¹ for AD, ED, AW and EW treatments, respectively. Elevated C_a increased season-long average dry weight (DW_S; crown, shoots) by 14% (P = 0.02), whereas deficit irrigation reduced DW_S by 7% (P = 0.06), although these values may have been affected by a short but severe pea aphid [Acyrthosiphon pisum (Harris)] infestation. Hence, an elevated-C_a-based improvement in gas exchange properties enhanced growth of a barley crop.     

六股河水质污染特征分析

本文通过对不同时段和不同监测点环境监测数据的对比分析,研究了六股河水质污染特征。结果发现：2004～2010年六股河上游和中游符合Ⅱ-Ⅲ类标准,水质保持良好,但部分年份入海口处水质下降,主要污染指标为高锰酸盐指数和石油类。水期监测结果反映了六股河水质主要污染特征：入海口处个别年份丰水期和平水期主要污染物浓度突升是造成水质下降的主要原因。高流量状态下水质下降反映出受面源污染影响特征。入海口小渔场断面污染物入海通量估算结果表明：高锰酸盐指数和石油类入海量总体呈下降趋势,氨氮入海量呈先下降后急剧升高趋势。