Height growth of northern red oak in relation to site and atmospheric deposition in Pennsylvania

A forest tree growth-response to atmospheric deposition is expected to arise indirectly through soil chemical changes and would probably be observable only in the long term. We examined this hypothesis by evaluating the relationship between periodic height growth of mature northern red oak (Quercus rubra L.) trees and soil, physiography and atmospheric sulfate deposition along a 170-km west-to-east gradient of decreasing sulfate deposition in north central Pennsylvania, USA. Height increments for three common 20-year periods beginning in 1929, 1949 and 1969 were estimated from exponential-monomolecular growth functions fitted to stem analysis data for each of 45 trees in 13 ecologically analogous stands along the deposition gradient. Canonical analysis was used to identify a statistically manageable subset of the original 48 independent soil, site and tree (age, crown width) variables strongly associated with height growth. Predictive models relating total (60-year) and the three 20-year height increments to the reduced variable set plus estimated average sulfate and nitrate deposition were derived by best subsets multiple regression. An inherent spatial gradient of decreasing height growth from western to eastern sites was apparent in even the earliest (1929-1948) increment. This inferred non-deposition-related spatial growth trend was accounted for in the 1949-1968 growth increment by introduction of the earliest (1929-1948) growth increment as a significant covariate in the regression model. The inherent growth largely disappeared by the 1969-1988 period as a probable consequence of converging growth rates reported to occur in oaks after age 60 years regardless of site quality. The 1969-1988 growth increment was not as strongly correlated with site factors as was growth in preceding periods, nor was early growth or sulfate deposition significantly related to this height increment. Growth effects from sulfate deposition, if any, would most likely occur within the recent (1969-1988) increment coincident with the period of naturally decreasing growth rate, when site differences and possibly environmental factors would have less influence on growth. Our results give no indication that wet sulfate inputs are affecting northern red oak height growth across the atmospheric deposition gradient.     

珠江咸潮如何治本

咸潮——因海水顺着潮汐倒灌入内江河，导致沿河两岸的水源变咸而得名，这是一种不为内陆民众所熟知的灾害。     

杠杆体坯件冷拔成形工艺及其平直度的研究

此文详细介绍了磅称杠杆坯件冷拔成形工艺过程和工艺参数,分析了生产中存在的翘曲、扭曲、旁弯及瓦形等严重形状缺陷的成因,论述了减少形状缺陷、提高平直度的工艺技术措施。     

西南环境移民安置地的生态环境状况

以桂西北环江县肯福环境移民安置示范区为例，对我国西南喀斯特地区，环境移民安置区的气候、地貌、土壤与植被等主要生态因子，进行了调查研究与取样分析，研究表明，环境移民安置地由于地处亚热带季风气候区，具有气候温暖，雨量充沛、日照充足，且雨热同季的特点；地貌破碎，土地以坡地为主，但有一定量可开垦利用的土地；土壤主要为红壤，土壤剖面发育良好，有机质和氮含量相对丰富，磷、钾缺乏，土壤酸度大，土壤质地和结构尚可     

红纺锤水蚤(Acartia erythraea)对Cu2+和Ag+的吸收

通过对桡足类动物红纺锤水蚤(Acartia erythraea)分别在Cu2 、Ag 、Cu2 Ag 混合溶液中的暴露实验,测定了其对Cu2 、Ag 的吸收速率常数、排出速率常数,并对Cu2 和Ag 在动物体内的分布状况进行了分析.结果表明,在单金属暴露的条件下,红纺锤水蚤对Cu2 、Ag 的吸收速度分别为1.09×104L·g-1·d-1、3.31×104L·g-1·d-1,排出速率常数分别为0.096 d-1、0.1056 d-1.而在Cu2 Ag 的混合暴露体系中,红纺锤水蚤对Cu2 、Ag 的吸收速率分别下降到9.17×103 L·g-1·d-1、2.87×104L·g-1-d-1,Cu2 和Ag 的排出速度常数则分别降到0.084 d-1和0.1008 d-1.动态模型的模拟结果表明,Cu2 和Ag 存在一定程度的拮抗作用.与暴露在单金属溶液中的红纺锤水蚤相比较,在暴露于Cu2 、Ag 混合体系中动物体内的非极性部分所占的比重明显增加,说明其在食物链中对于上一营养级的生物有效性将明显增加.     

长江、嘉陵江重庆段生活垃圾污染负荷研究

通过对重庆市生活垃圾的取样分析，得出重庆市城区、郊区城镇生活垃圾中污染物含量，从而计算出重庆现有的生活垃圾污染负荷。同时，对重庆市到２０００年生活垃圾污染负荷进行了预测，为重庆市水污染控制规划提供了必须的生活垃圾污染负荷数据。     

吸附胶体浮选法处理电解钴废水的研究

采用吸附胶体浮选法处理电解钴废水。用十二烷基磺酸钠（ＳＬＳ）作浮选剂，用ＦｅＣｌ３和Ａｌ２（ＳＯ４）３作混凝剂，浮选后废水可达到国家工业废水排放标准（３ｍｇ／Ｌ）。为实际废水的处理提供了可靠的依据。     

The life table and competing risks

The concept of the life table originated in longevity studies of man, where it was always presented as a subject peculiar to public health, demography, and actuarial science. As a result, its development has not received sufficient attention in the field of statistics. Actually, the problems of mortality studies are similar to those of reliability theory and life testing, and they may be described in terms familiar to the statistically oriented mind. From a statistical point of view, human life is a random experiment and its outcome, survival or death, ss subject to chance. The life table systematically records the outcomes of many such experiments for a large number of individuals over a period of time. Thus, the quantities in the table are random variables subject to established statistical analysis. The purpose of this presentation is to discuss the life table from a statistical viewpoint.     

油田高盐浓度废水对其生化处理的影响

根据油田压裂液废水中的盐浓度对生化处理系统的影响,对生化处理系统中活性污泥的生物学变化规律进行了实验研究。结果表明:当废水中盐浓度低于2.5×104mg/L时,废水生化处理系统对COD的去除率可稳定在92%左右,污泥活性良好;当废水中盐浓度达到2.5×104mg/L时,污泥活性开始受到抑制,COD去除率急剧下降(稳定在80%左右);当盐浓度达到3.5×104mg/L时,COD去除率下降到60%左右;当废水中盐浓度达到6.0×104mg/L时,污泥活性系统趋于崩溃。     

玉门矿区污染黄土中原油的解吸研究

用振荡平衡法研究了玉门矿区原油污染黄土中原油的解吸行为，测得了解吸常数，绘出了解吸等温线。结果表明，Freundlich方程可较好地描述黄土中原油的解吸状况；黄土中原油的解吸行为受温度、溶液pH值和表面活性剂的影响；温度和pH值越高，原油解吸量越大；阴离子表面活性剂的加入有助于原油的解吸，在相同条件下使解吸率提高了5倍，阳离子和非离子表面活性剂的加入不利于原油解吸，但是阳离子表面活性剂的加入有利于原油在土壤中的截留以及回收再利用。本研究为修复玉门原油污染黄土提供了理论依据。