土壤对城市雨水径流中污染物的削减作用

[目的]分析城市雨水径流在土壤中的净化情况及径流污染物对土壤环境造成的影响。[方法]在充分了解陕西省西安市某地土壤特性和当地雨水径流水质的基础上,模拟城市土壤表层系统和雨水径流装置,研究雨水径流中的污染物在下渗过程中土壤表层对它们的削减作用及土壤基本理化性质的变化。[结果]在土壤层厚度为20cm,雨水渗透量为6 000ml,径流时间3h的条件下,裸土和绿地表层土壤对模拟雨水中各污染物的去除率均达到40%以上;土壤的密度及pH值基本未发生变化,氮的含量由原土的54.95mg/kg分别增加到65.10(绿地)和68.60mg/kg(裸土),有效磷的含量由原土的59.23mg/kg变化到82.39mg/kg(裸土)和39.93mg/kg(绿地),有机质的含量由原土的18.32mg/kg变化到19.28mg/kg(裸土)和14.04mg/kg(绿地)。[结论]绿地对雨水径流处理效果较好。在渗流过程中,土壤对氨氮的截留效果较为明显,短时间内土壤基本物理性质变化不大。     

Lake Sediments from Dianchi Lake： A Phosphorus Sink or Source？

Dianchi Lake is a highly eutrophic lake in southwestern China where phosphorus (P) is the limiting element for eutrophication and where lake sediments play an important role in the P cycle. One hundred and eighteen sites were sampled throughout Dianchi Lake in 2002 to investigate the P loading of the lake sediments, while fresh surface sediments were studied in the laboratory to clarify its role for phosphorus. The results showed that concentrations of total phosphorus(TP) in sediments were very high, with a maximum value of 6.66 g kg^-1, and decreased with sediment depth. P adsorption on surface sediments was rapid with adsorption amounts higher in acidic than in alkaline conditions. The release experiments showed that P release increased as pH rose from 7.0 to 10.5. Additionally, compared with aerobic conditions, P release was much higher under anaerobic conditions, especially with low P content in the lake water. At present, the sediments in Dianchi Lake still function as a sink for phosphorus at high P levels in lake water. However, if the external P load was reduced and P content in lake water became low, the sediment would have a large potential for P release under anaerobic conditions.     

氧化势影响下的滇池沉积物孔隙水磷浓度变化

The sediment redox potential was raised in the laboratory to estimate reduction of internal available phosphorus loads, such as soluble reactive phosphorus （SRP） and total phosphorus （TP）, as well as the main elements of sediment extracts in Dianchi Lake. Several strongly reducing substances in sediments, which mainly originated from anaerobic decomposition of primary producer residues, were responsible for the lower redox potential. In a range of -400 to 200 mV raising the redox potential of sediments decreased TP and SRP in interstitial water. Redox potentials exceeding 320 mV caused increases in TP, whereas SRP maintained a relatively constant minimum level. The concentrations of Al, Fe, Ca^2＋, Mg^2＋, K^＋, Na^＋ and S in interstitial water were also related to the redox potential of sediments, suggesting that the mechanism for redox potential to regulate the concentration of phosphorus in interstitial water was complex.     

烟台果园表层土壤水分的时空分布及分形特征

在果树生长旺期,利用Trim e水分速测系统对果园表层土壤水分采样后,对土壤水分的数据统计特征、变异函数、分形特征、合理取样数目及其等值线分布进行了分析。结果表明:降雨后变程和基台值最大,变异系数和分维数最小,其值分别为38.09m、1.163、0.0888和1.846。在90%或95%的置信水平(Pl)和相同精度(Δ)下,降雨后土壤水分合理取样数目最少,此时土壤水分的空间等值线分布的变化程度相对也较小。这说明降雨有促使土壤水分分布趋于均匀及空间相关性增强的效应,但也可能导致在个别区域内出现明显的高低值;而随后的土壤蒸发则使土壤水分的结构性减弱,空间异质性增强。     

洪水沉积物对长江中游洪泛区土壤肥力的影响Ⅰ.对养分含量及作物生长的影响

长江中游平原湖区地势低洼、洪涝频繁，历史上洪水带来的大量泥沙是该区土壤母质的主要来源。     

浅旋在保护性耕作中的作用和地位

旋耕作业是指利用旋耕机对耕地进行的耕作处理。旋耕作业深度一般在20cm以内．旋耕作业时，旋耕机的旋耕刀在对土层进行翻动，同时也将地表上的植被进行粉碎，并把粉碎过的植被和表层土进行混合，处理过的地表较为松软平整，十分有利于播种，因此，在我国很多地方旋耕作业已经代替了用铧犁翻耕作业。浅旋是旋耕作业的一种形式，是特指对10cm以内的地表浅层进行旋耕处理的作业，通常处理的深度在6-10cm。浅旋作业后，由于部分植被被埋于表层土中，减少了地表的覆盖量，降低了保护性耕作的效果。因此，学术界、政府主管部门和各地具体实施部门，对在保护性耕作中使用浅旋一直存有异议，现就相关问题作一些简要的分析。     

风蚀控制

土壤风蚀是中国西部和北部地区面临的一个重大问题。悬浮在空中的灰尘损害了人畜的健康，污染了家庭和企业，损坏了机械设备．污染了储藏的饲料，并且降低道路能见度从而增加交通危险。表层土的丧失降低了土地的生产力，并且增加了对化肥的需求。风蚀的成本无疑大于控制风蚀的成本。     

大龙洞水库放水塔改建中表层取水结构的选择

介绍了大龙洞水库放水塔改建中对表层取水结构方案的拟定过程，分析了各方案的特点， 进行了方案比较和采用方案的最后确定。详细阐明了采用方案的取水结构的构造、组成和特点，分析了该结构的取水性能。     

呼伦湖沉积物有机碳的分布特征

以内蒙古高原湖泊呼伦湖为对象,开展了湖泊沉积物有机碳的分布特征研究。结果表明:呼伦湖沉积物中总有机碳(TOC)含量范围为9.18～61.68g·kg-1,平均34.64g·kg-1;重组碳(HFOC)含量范围为9.02～61.47g·kg-1,平均34.32g·kg-1;轻组碳(LFOC)含量范围为0.02～0.86g·kg-1,平均0.32g·kg-1。TOC在空间分布上呈现从北西向南东逐渐递减的趋势。表层沉积物中C/N的平均值为20.35,表明呼伦湖中有机质的多源性。