Forest drainage: a threat to benthic biodiversity of boreal headwater streams?

1. Forest drainage, including mainly ditching of waterlogged peatlands in order to increase wood growth, has caused substantial changes in the hydrology and water quality of Finnish streams. However, knowledge on the ecological impact of these changes is poor. This paper studies the potential impact of forest drainage, catchment characteristics and habitat factors on the water quality and benthic macroinvertebrates in headwater streams of the River Isojoki, western Finland. An intensive programme of water sampling was carried out at nine study sites, while zoobenthic samples covered a total of 18 streams. 2. According to multivariate regression models concentrations of aluminium and suspended solids in stream water at nine study sites increased significantly with increasing forest drainage of the catchment area. Further, drainage intensity contributed significantly to the decrease in minimum values of alkalinity. 3. In a Canonical Correspondence Analysis, the variation in macroinvertebrate species distribution and abundance was largely explained by drainage intensity, moss coverage and the concentrations of aluminium and iron in stream water. A significant positive correlation was established between the species richness of benthic macroinvertebrates and the proportional cover of vegetation on the stream bed, whereas a significant negative correlation was found between species richness and sand cover. 4. The results suggest that drainage has significantly contributed to the deterioration of water quality and habitat structure, and impoverishment of benthic communities in the headwater streams of the River Isojoki. In order to protect the ecological integrity of such boreal headwater streams, more effective protection schemes in forestry practices and rehabilitation of the adversely affected streams and their catchment areas are needed. © 1998 John Wiley & Sons, Ltd.     

臭氧对循环水系统中悬浮颗粒物净化效果及机理研究

为了研究臭氧对循环水养殖系统中悬浮颗粒物的净化效果,探讨臭氧对悬浮颗粒物的影响机理,在养殖水体投加不同量的臭氧进行实验室小规模模拟实验,对水体的TSS、浊度等指标进行检测,并对悬浮颗粒物进行粒度分析。结果表明投加臭氧有助于降低水体浊度,投加7.53mg/L臭氧可将浊度为(5.22±0.55)NTU的原水降低浊度12.47%,投加15.05mg/L和22.58mg/L 臭氧则可提高到25.31%和30.20%。投加臭氧将影响悬浮颗粒物的物理特性,在投加22.58mg/L臭氧时对颗粒物助凝效果显著,将悬浮颗粒物粒径大多分布在48-68um范围的原水转变成99.22%数量的颗粒物粒径>64um,有利于后续物理过滤处理。本研究明确了臭氧对悬浮颗粒物的净化效果是通过氧化有机物产生络合沉淀和胶体絮凝物等改变颗粒物的粒径大小分布的途径来实际的,为臭氧在循环水养殖系统中的应用提供理论支撑。     

Ambient TSP concentration and dustfall variation in Urumqi,China

Total suspended particulate(TSP, particle diameter≤100 μm) was the dominant air pollutant and significantly influenced local air quality. In this paper, we investigated the interannual and seasonal variations of TSP and dustfall of the atmosphere over Urumqi, the capital city of Xinjiang Uygur autonomous region, northwestern China, basing on environmental monitoring records and meteorological data from 1986–2012. The results showed that during the study period, annual average TSP concentration decreased from 716 to 260 μg/m3, with an average level of 422.9 μg/m3, while dustfall intensity reduced from 350.4 to 166.6 t/(km2?a), with an average level of 259 t/(km2?a). Over 50% of the annual pollution days were induced mainly by TSP. Spring and winter had relatively higher dustfall intensities, and dense traffic and residential areas had the highest dustfall intensities in the Urumqi metropolitan area. With an annual average precipitation of less than 300 mm, atmospheric particulates in Urumqi could be hardly removed through wet deposition. During spring and summertime prevailing winds from northwest and northeast could carry aeolian dust particles from sandy deserts to Urumqi. Aeolian dusts from deserts would remain to be a priority regarding air pollution control in arid oasis cities.     

大跨度悬索静力构形和内力计算方法

建立悬索重力曲线方程的差分形式,给出悬索在自重、索端移动、集中力作用下非线性分析的一种简单的有限差分法迭代模型。与有限元方法不同,本方法不需要悬索初始线形,只需要输入悬索两端坐标、索截面面积、弹性模量、初始张力,可计算悬索在不同状态下的张力和线形,算例表明该方法收敛速度快,精度高。     

滤食性双壳贝类对工厂化养殖废水中悬浮物的生物滤除研究

针对海水鱼类半滑舌鳎养殖池排出水中大量絮状悬浮物难以用常规机械过滤法去除的问题,选择适应能力强的滤食性双壳贝类长牡蛎(Crassostrea gigas)和紫贻贝(Mytilus galloprovincialis),通过现场实验测定了它们对鱼类养殖排出水中悬浮物的生物滤除能力。结果表明,在海水流速为100L·h-1条件下,牡蛎[壳高(9.80±0.45)cm,湿重(117.0±10.0)g]和贻贝[壳高(6.54±0.26)cm,湿重(29.7±2.4)g]对养殖排出水悬浮物的生物沉积速率分别为40.28～45.30mg·ind-1·d-1[平均(43.40±2.16)mg·ind-1·d-1]和6.96～8.87mg·ind-·1d-1[平均(7.66±0.99)mg·ind-·1d-1];在实验海水流速为150L·h-1条件下,牡蛎[壳高(9.33±0.99)cm,湿重(95.8±31.4)g]和贻贝[壳高(6.39±0.91)cm,湿重(28.0±15.4)g]对悬浮物的生物沉积速率分别为13.68～22.50mg·ind-1·d-1[平均(17.35±4.59)mg·ind-1·d-1]和5.37～...     

人工浅水湖泊高含沙补水过程中叶绿素a浓度的变化

在2012年4月23日至26日高含沙的黄河水向东昌湖补水期间,分别对湖面12个监测点及从入湖口到出湖口的纵断面 5个监测点同步取样、测流和测沙,从整体到局部分析了悬浮泥沙与叶绿素a浓度的变化。结果表明：补水前,湖区叶绿素a平均浓度为4.07 μg·L-1,补水后达到7.74 μg·L-1,其中黄河补水贡献了21.1%。在从入湖口到出湖口的纵断面中,入湖口附近监测点A、B叶绿素a浓度增幅由大变小,流速、悬浮泥沙均出现明显高峰,监测点C、D、E依次呈现递减趋势。补水期间,5个纵断面监测点叶绿素a浓度与悬浮泥沙含量呈现极显著负相关,相关系数达-0.81,而补水前后其相关系数仅在-0.43左右。湖面细颗粒悬浮泥沙占主导的监测点,叶绿素a浓度增幅大,反之,粗颗粒占主导的监测点,叶绿素a浓度增幅小,故可推断悬浮泥沙对叶绿素a的影响表现为“高浓度粗颗粒悬浮泥沙抑制叶绿素a浓度的增加,细颗粒或胶粒悬浮泥沙促进叶绿素a浓度的增加”,但这种影响只在补水短期内显著。因此,悬浮泥沙在黄河补水期间是影响叶绿素a浓度变化的主要水环境因素之一。     

基于MODIS影像估算鄱阳湖泥沙浓度及其时空变化

悬浮泥沙浓度是衡量水质的重要指标之一,估算其泥沙浓度及获得其在空间和时间上的分布信息对于保护与管理湖泊生态系统是有利的。该研究以鄱阳湖区域为例,利用MODIS。感影像,并结合反演模型对鄱阳湖区域的悬浮泥沙浓度进行反演。结果显示：2010年鄱阳湖悬浮泥沙浓度呈明显的时间和空间分布特征。     

夏、冬季苏北近岸海域悬沙浓度垂直分布特征

通过将2012年8月、12月在苏北黄海海域野外调查获得的声学多普勒流速剖面仪(ADCP)后向散射强度数据与悬沙浓度进行拟合,得知两者的相关系数在0.8以上,反演结果较理想。并结合同步观测的温度、盐度等水文要素资料,对该区域夏、冬季两季悬浮泥沙的垂直分布特征、形成原因及输运进行了研究,结果表明苏北近岸海域悬浮泥沙分布的典型性季节变化明显,冬季悬沙浓度普遍高于夏季。悬浮泥沙分布及输运受苏北沿岸水、黄海西部沿岸流、长江冲淡水、黄海暖流、黄海冷水团等影响,其中黄海西部沿岸流的季节变化为主要的影响因素。苏北沿岸水携带废黄河口的再悬浮泥沙和近岸悬沙向东南外海扩散,冬季的搬运量和扩散范围显著大于夏季。黄海暖流阻碍悬沙向外海扩散,使其在近岸被大量捕集下来。夏季长江冲淡水的东北方向偏转,使得苏北南部海域悬沙分布出现层化现象。     

立面阳台式太阳能热水器的性能特性

以阳台平板太阳能热水器和全玻璃真空管太阳能热水器为对象,研究太阳能集热器南立面横排和竖排放置,自然循环和强制循环对系统热性能和水箱分层的影响。结果表明,对于立面阳台式全玻璃真空管太阳能热水器,集热器横排放置比竖排放置系统循环快,热效率提高12%。对于立面阳台式平板太阳能热水器,自然循环时无论是横排放置还是竖排放置,液体循环不流畅,系统热效率均小于30%;采用强制循环能有效改善循环状况,平均进出口温差稳定,系统热效率约为63%。     

农田轻便土壤悬虚镇压器的研制与应用

针对目前旋耕机大面积应用造成的农作物播前或播后土壤悬虚现状,提出了农田轻便土壤悬虚镇压器研制的指导思想。研制出的镇压器主要包括牵引装置、轴承、压辊装置3部分,可满足不同农田所需镇压深度的要求,并对其提出了合理的工作参数。该机具克服了以住镇压辊质量固定、携带不便等缺点,灵活轻便、无需配套动力、生产和作业成本低、作业效率高,经不同农田镇压效果良好。