Availability of Cadmium in some Phosphorus Fertilizers to Field-Grown Lettuce

Although evaluations of the availability of cadmium (Cd) contaminants in phosphate fertilizers have been made, few have examined the transfer efficiency of Cd from fertilizers to plants, especially under field conditions. This 2-year field study determined the transfer of added Cd to lettuce (Lactuca sativa L.) (Royal Green) from a western phosphate rock (PR) and a triple superphosphate (TSP) as affected by liming and rate of fertilizer (or Cd) input. A readily soluble Cd salt, CdCl₂, was included in the study for comparison. The cumulative amounts of Cd added from the fertilizers and CdCl₂ over the 2-year period ranged from 0 to 1440 g ha^–1. Lettuce yield increased with increasing TSP rates, but was unaffected by PR. Significant (P < 0.01) effects of Cd source and rate, lime, and year were found on Cd accumulation by lettuce. The transfer of the added Cd was consistently higher for CdCl₂ than for the fertilizers regardless of lime rate. A contrasting year effect was also found between the two P fertilizers. In the second year of application, the Cd transfer efficiency increased in the soil treated with the PR, but decreased in the soil treated with the TSP. The Cd transfer efficiency for the plant was better measured with DTPA–Cd (r ²= 0.78 – 0.80) or CaCl₂–Cd (r ²= 0.57 – 0.76) than with soil total Cd (r ²= 0.39 to 0.54) across all Cd sources and lime rates. This is because DTPA–Cd or CaCl₂–Cd reflected the influences of the amount of Cd added, Cd source, and lime rate on Cd accumulation by the plant better than did the soil total Cd. Of the amount of Cd added from the fertilizers an average of 1.0% or less was accumulated in the harvested lettuce tissue. Applications of the fertilizers at high rates could result in increased Cd accumulation in the soil over time.     

Fractal features of soil particle size distribution and the implication for indicating desertification

Some of the effects of land desertification on soil properties are manifested by the coarsening of the soil particlesize distribution (PSD) and the losses in organic C and nutrients. The changes and characteristics of PSD and selected chemical properties in soils at the 0-15 cm plough layer from different degrees of desertified croplands are analyzed in the semiarid Horqin Sandy Land, northern China. The fractal dimension of the PSD is emanated to characterize the patterns of PSD. The relationships between the fractal dimension of the PSD and selected soil properties are discussed. The results show that: (1) in the transformation from potential desertified cropland to extremely desertified cropland, the sand content at the 0-15 cm soil increased from 69% to 93%, organic C and total N contents decreased by 65% and 69%, respectively; (2) the fractal dimension of PSD ranged from 2.179 to 2.611, the more the contents of sand, the lower the fractal dimension and the higher the desertified degree of farmland. In the desertification process within the studied area, the mean fractal dimension decreased from 2.555 for the potential desertified soils to 2.298 for extremely desertified soils; (3) there existed considerable linear relationships between fractal dimension and soil properties. It was shown that fractal dimensions of PSD are useful parameters able to monitor soil degradation and to estimate the degree of soil desertification.     

土地整理综合效益评价指标与方法

土地整理综合效益评价包括经济效益、社会效益和生态效益三方面，根据多次专家咨询和问卷调查结果，逐次求取影响土地整理综合效益评价的指标，用层次分析法(AHP)确定各评价指标权重，量化各评价指标，求出综合效益评价值，并以江苏省溧阳市新昌镇土地整理综合效益评价为例。新昌镇土地整理综合效益评价结果表明：该镇土地整理综合效益评价效果较好，但社会效益和部分生态效益指标增加不明显，在土地整理实践中应重视促进土地整理的经济效益、社会效益和生态效益协调发展。     

不同氮素形态配比对网纹甜瓜干物质分配和氮代谢的影响

该文研究了4种氮素形态配比(NO3--N∶NH4 -N分别为100∶0,75∶25,50∶50和25∶75)对基质栽培网纹甜瓜(品种为“春丽”和“蜜玲珑”)干物质积累和氮代谢的影响。结果表明,不同氮素形态配比影响了植株各器官干重占全株干重的百分比。随氮素形态中氨态氮比例的增加,叶片中硝酸还原酶、硝酸盐含量和可溶性蛋白质含量逐渐降低,而游离氨基酸含量则在NO3--N∶NH4 -N为50∶50的处理中最高。     

桂牧1号象草营养价值评定及PEG对其产气量的影响

用体外产气法测定了桂牧1号象草不同月份、不同高度的产气量及添加聚乙二醇（PEG）对产气量的影响。结果显示：（1）桂牧1号象草各月份的干物质含量比较为：11月〉10月〉9月〉4月。其中，1．0m左右及1．0m以上的象草的干物质含量明显较高（P〈0．01）。（2）在体外产气法实验中添加PEG能显著增加样品12h和24h的产气量（P〈0．01），证明象草中所含有的抗营养因子对黑山羊瘤胃微生物活动有一定的制约作用。（3）9、11月份象草的最佳刈割高度应为1．5m左右，4、10月份象草的最佳刈割高度应为1．0m左右。（4）4月、9月份的象草，添加PEG后产气量提高率较高。利用此时期的象草喂食黑山羊时，适当做PEG处理可以提高象草的饲用价值。     

江苏省畜禽粪便污染现状与防治对策

根据2000年以来江苏省畜禽饲养状况的有关资料,利用各类畜禽粪便日排泄系数估算畜禽粪便量,在此基础上计算江苏省各地畜禽粪便污染负荷量。研究发现,江苏省畜禽养殖业产生的粪便及各类污染物数量巨大,盐城市产生的粪便及各类污染物居全省首位,南通市次之;江苏省畜禽粪便污染负荷量平均为16.5t/(hm~2·a),南通市畜禽粪便污染负荷量最高,达26.7t/(hm~2·a)。全省畜禽粪便污染负荷最高的县是南通市的海安县,其次是盐城市的盐都县。最后本文分析了畜禽粪便污染环境的主要原因并提出了畜禽养殖污染防治的对策。     

长汀县退化劣质"老头松"改造效果分析

采用挖穴施肥和条沟草带2种方法,在2个不同的地点对劣质马尾林进行改造试验,从林木年抽梢、材积、覆盖和地表草灌多样性进行分析.结果表明:经过3年改造的马尾松抽梢总长在1.6m以上,比对照0.95m增长0.65m以上,年均多增长0.22m;材积增长12.7m3/hm2,比对照3.4增长9.3m3/hm2,年均增加3.1m3/hm2;覆盖度也增加32%～47%,比对照分别增加19%和32%;同时促进了生物多样性,草灌植被均增加10种以上.     

黄土丘陵区几种林木茎干径向生长的日变化及其对环境因素的响应

利用树木径向生长仪研究了黄土丘陵区6年生油松（Pinus tabulaef ormis）、山杨（Populus davidiana）和辽东栎（Quercus liaotungensis）及林下灌木胡颓子（Elaegnus umbellata）4种林木整个生长季茎干的径向变化,发现4种林木的径向变化表现为膨胀收缩旋回增长的模式。在整个生长季中,山杨从5月到10月径向持续增长,增长时间最长;而油松和胡颓子的径向生长主要发生在7月份,从8月份开始其增长速率变缓;辽东栎在整个生长季节的径向生长最小。在整个生长季内,山杨径向增长了2.63 mm,胡颓子为0.64 mm,油松和辽东栎则分别为0.40 mm和0.26 mm。辽东栎日收缩量与膨胀量明显大于其他树种。通过对影响林木径向生长的15种环境因子进行主成分分析后,将主要环境因子归结为温度影响因子、湿度影响因子和降水影响因子3个主成分,并提取了影响该区几种林木生长的主要环境因子：日大于0℃的积温、最低6 h相对湿度和日降雨量。采用线性逐步回归方法,建立了日膨胀量与日收缩量与3个主要环境因子之间的关系。发现日收缩量与日大于0℃的积温成正相关,而与最低6 h相对湿度和日降雨量均呈负相关关系;而日膨胀量亦与日大于0℃的积温成正相关,而与其他环境因子的关系随着树种的不同而不同,表现出较大的变异性。     

坡面产流机制研究刍议

随着水文学的发展,坡面产流问题越来越受到水文学领域的重视。对坡面产流机制(这里的坡面产流包括地表径流产流和壤中流产流两个部分)的研究现状详细进行了回顾与分析,并提出了目前产流机制所面临的问题,以期推动降雨产流计算方法和流域水文模型机构的发展。     

有机酸对针铁矿和膨润土吸附Cd2+、Pb2+的影响

用平衡吸附法研究了不同浓度的有机酸（乙酸、酒石酸和柠檬酸）对针铁矿和膨润土吸附Cd^2＋、Pb^2＋的影响。结果表明：（1）低浓度（〈0．6mmolL^-1）有机酸促进供试矿物吸附Cd^2＋和Pb^2＋，随着有机酸浓度增加，吸附逐渐被抑制。高浓度（〉1．0mmolL^-1）有机酸对Pb^2＋吸附的抑制作用比对Cd^2＋的强。有机酸浓度的变化对针铁矿Cd^2＋、Pb^2＋吸附率的影响大于对膨润土的。（2）不同Cd^2＋浓度下，有机酸对膨润土Cd^2＋吸附强度的影响大于针铁矿。加入高浓度Cd^2＋（8．0mmolL^-1）时，低浓度有机酸对膨润土吸附Cd^2＋的促进作用比加入低浓度Cd^2＋（0．4mmolL^-1）时明显，高浓度有机酸对膨润土吸附Cd^2＋的抑制作用与低浓度Cd^2＋时相近。（3）低浓度有机酸（〈0．6mmolL^-1）时，酒石酸、柠檬酸对针铁矿吸附Cd^2＋的促进作用大于乙酸，而它们对膨润土吸附Cd^2＋的促进作用相似；在三种有机酸高浓度（〉1．0mmol L^-1）时，针铁矿对Cd^2＋的吸附都趋于稳定，而柠檬酸对膨润土吸附Cd^2＋的抑制作用比乙酸和酒石酸的明显。不同种类有机酸下，矿物对Pb^2＋吸附率大小的变化基本一致。