氮添加对亚热带森林土壤有机碳氮组分的影响

为了研究氮添加对森林土壤有机碳氮组分稳定性的影响,选取我国亚热带典型常绿阔叶林(浙江桂天然林和罗浮栲天然林)和针叶林(杉木人工林),开展为期5年的野外模拟氮沉降试验,分别设置对照〔0 kg/(hm2·a),以NH₄NO₃中的N计,下同〕、低氮〔75 kg/(hm2·a)〕和高氮〔150 kg/(hm2·a)〕3个氮添加水平,用H₂SO₄分2步酸水解获得LPⅠ(活性有机库Ⅰ)、LPⅡ(活性有机库Ⅱ)和RP(惰性有机库),定量研究土壤活性和惰性有机碳氮组分以及微生物生物量碳氮对氮添加的响应. 结果表明:氮添加仅对w(LPⅡ-C)(LPⅡ-C为活性有机碳Ⅱ)有显著影响,而对其他活性和惰性有机碳氮组分的影响不显著,并且对不同林分的影响存在差异. 与对照处理相比,低氮处理下浙江桂天然林、罗浮栲天然林和杉木人工林土壤w(LPⅡ-C)的增幅分别为15.3%、29.8%、68.8%;高氮处理下杉木人工林土壤w(LPⅠ-C)(LPⅠ-C为活性有机碳Ⅰ)、w(LPⅠ-N)(LPⅠ-N为活性有机氮Ⅰ)和w(RP-C)(RP-C为惰性有机碳)的增幅分别为32.4%、78.6%、28.7%;氮添加使得土壤w(SMB-C)(土壤微生物生物量碳)的增幅为18.1%~202.5%、w(SMB-N)(土壤微生物生物量氮)的增幅为0%~103.6%;在氮添加处理下,除杉木人工林土壤SMB-N/LPⅠ-N〔w(SMB-N)/w(LPⅠ-N)〕是随着氮添加水平的增加而降低外,微生物对其他林分土壤活性有机氮的利用均表现为随着氮添加水平的增加而增加. 研究显示,氮添加对阔叶林和针叶林土壤活性和惰性有机碳氮组分的影响存在差异,但差异不显著,这与它们归还土壤的凋落物性质差异有关,并且凋落物的分解差异也可能是影响土壤不同碳氮组分变化的原因.      

长期有机无机肥配合施用土壤中添加不同肥料养分后土壤微生物短期变化

为了阐明改变肥料养分投入后土壤微生物特性的短期变化,采集长期定位有机无机肥配施的红壤水稻土,通过室内培育试验,观测添加不同肥料养分后土壤微生物生物量碳及BIOLOG群落功能多样性的变化.结果表明,长期有机无机肥配施土壤中添加无机肥料养分短期内( 185 d)降低了15％～22％的微生物生物量碳含量和55.6％的微生物群落平均光密度；添加有机肥料养分短期内提高了8％～42％的微生物生物量碳含量和992％的微生物群落平均光密度；而不添加肥料养分短期内提高了501％的微生物群落平均光密度,降低了微生物群落均一性,但对微生物生物量碳含量影响不大.此外,添加不同肥料养分均改变了土壤微生物群落碳源代谢模式.长期配施有机无机肥土壤中添加不同肥料养分后土壤微生物生态特征发生明显变化,其差异体现在微生物生物量碳与微生物碳源利用特性的变化上.     

活性污泥储存与消耗乙酸基质的试验研究与模拟

同时贮存与生长理论认为,活性污泥吸收有机碳基质同时用于储存和生长.向SBR反应器投加不同浓度乙酸基质,监测活性污泥氧利用速率(OUR)、聚羟基烷酸盐(PHA)和出水COD的变化,运用活性污泥同时贮存与生长理论分析有机碳储存与消耗过程的特征.结果表明,饱食期结束与COD消耗至最低水平、PHA浓度出现最大值和OUR由最大值急速下降相对应;在饱食阶段,基质贮存OUR是利用外部基质直接生长OUR的2倍.随基质投加历时延长,饱食期平均OUR和最大OUR均下降,PHA产率降低,甚至出现PHA净消耗.因此,基质投加方式对有机碳基质储存与消耗有重要影响.     

Nitrogen to phosphorus ratios of two understory plant species in response to nitrogen and phosphorus addition in tropical forest of southern China北大核心CSCD

The secondary tropical forests in southern China have suffered from frequent human disturbance and increasing high N deposition. In order to explore the nutrient limitation status in secondary tropical forests of South China, this 3-year field experiment of nitrogen (+N) and phosphorus (+P) addition investigated nitrogen (N) and phosphorus (P) concentrations of the aboveground tissue (leaf and branch) of two widely distributed understory native species Clerodendrum cyrtophyllum and Uvaria microcarpa in a secondary tropical forest of South China. The results showed that: 1) the N and P concentrations of the two species were significantly different (P < 0.001); N and P concentrations of different tissues in the same species were different; N&P addition greatly affected N and P concentrations in branch rather than new leaf and older leaf. 2) +N treatment had no significant effect on N or P concentrations of either species, but significantly decreased N:P ratios (P = 0.001), at the level of 9% for C. cyrtophyllum and 50% for U. microcarpa, respectively. 3) +P treatment had no significant effect on tissue N concentrations, but significantly increased plant P concentrations (P < 0.001), at 54% for C. cyrtophyllum and 88% for U. microcarpa, respectively; +P treatment significantly decreased plant N:P ratios (P < 0.001), at 28% and 60%, respectively. 4) The alterations of P concentrations of two species had significantly negative correlations with N:P alterations under +N/+P treatment (P < 0.001), suggesting that the alteration of P concentrations in plant tissue was the major driver for N:P alteration. Our results show that N and P addition would affect tissue N and P concentrations of the two species, with +P treatment having relatively greater effect on nutrient concentrations than +N treatment; the branch is more sensitive than new or older leaf in response to nutrient addition. Therefore, P availability may be the limiting factor for plant growth in the tropical forests.     

我国14种典型土壤脲酶、脱氢酶活性对汞胁迫的响应

Hg作为环境的主要污染重金属之一,其对土壤酶的影响是表征其环境效应的重要方面,结果可为土壤环境监测等提供生物学依据.因此,本文通过室内模拟试验,较系统地分析了全国14种主要类型18个土样的脲酶和脱氢酶活性在Hg胁迫下的响应.结果表明,Hg会抑制土壤酶活性,其降幅随土壤类型的不同有明显差异;随着Hg含量的升高,土壤脲酶和脱氢酶活性均显著降低;模型U=A/(1+B×C)可较好地拟合酶活性(U)与汞含量(C)之间的关系,揭示出土壤脲酶和脱氢酶在一定程度上可监测土壤Hg污染的程度,且机理为完全抑制(包括竞争性抑制和非竞争性抑制)作用.同时,实验获得的供试土样脲酶的生态剂量(ED10)范围为0.08~0.77 mg·kg-1,脱氢酶ED10范围为0.11~2.58mg·kg-1,从土壤酶角度获得的土壤汞轻度污染临界值为0.08 mg·kg-1,此值要小于国家土壤质量标准中的二级标准.有机质、pH、CEC和粘粒显著影响了汞与土壤脱氢酶的关系,上述4个土壤性状参数值越高,汞对土壤酶的毒害作用就越弱;酸性土壤中汞的毒害作用强于碱性土壤.表明在我国主要土壤类型上,土壤脲酶、脱氢酶对Hg毒性均较为敏感,可在更广范围内作为Hg污染程度的监测指标之一.     

Differential responses of short-term soil respiration dynamics to the experimental addition of nitrogen and water in the temperate semi-arid steppe of Inner Mongolia, China

We examined the effects of simulated rainfall and increasing N supply of different levels on CO2 pulse emission from typical Inner Mongolian steppe soil using the static opaque chamber technique, respectively in a dry June and a rainy August. The treatments included NH4NO3 additions at rates of 0, 5, 10, and 20 g N/（m2.year） with or without water. Immediately after the experimental simulated rainfall events, the CO2 effluxes in the watering plots without N addition （WCK） increased greatly and reached the maximum value at 2 hr. However, the efflux level reverted to the background level within 48 hr. The cumulative CO2 effluxes in the soil ranged from 5.60 to 6.49 g C/m2 over 48 hr after a single water application, thus showing an increase of approximately 148.64% and 48.36% in the efftuxes during both observation periods. By contrast, the addition of different N levels without water addition did not result in a significant change in soil respiration in the short term. Two-way ANOVA showed that the effects of the interaction between water and N addition were insignificant in short-term soil COz efftuxes in the soil. The cumulative soil CO2 fluxes of different treatments over 48 hr accounted for approximately 5.34% to 6.91% and 2.36% to 2.93% of annual C emission in both experimental periods. These results stress the need for improving the sampling frequency after rainfall in future studies to ensure more accurate evaluation of the grassland C emission contribution.     

辐射化学剂量计在强脉冲混合辐射场测定中的应用

本文讨论了将硫酸亚铁剂量计和铜－铁剂量计用于强脉冲混合辐射场测定的实验设计,利用直径２２０毫米的聚乙烯球,将硫酸亚铁剂量计的快中子响应降低到２０％以下,由它和完全暴露在中子、γ混合场中的硫酸亚铁剂量计响应之差,测量中子吸收剂量。这种方法两次实际用于强脉冲混合辐射场中子、γ吸收剂量测量,得到的结果和热释光剂量计、固体径迹探测器的测量结果进行了比较,在±２５％的误差范围内一致     

成都施用磷肥中镭（^226Ra）含量调查及对农田环境影响评价

本文报道了成都磷肥及其原料矿石中外照射剂量水平；用国家标准规定的方法测定了磷肥及其矿石中＾２２６Ｒａ含量；调查了同一生产厂家不同批号磷肥中＾２２６Ｒａ含量变化情况；估算出施用磷肥后可能带来的放射性环境污染，并对磷肥中＾２２６Ｒａ可能导致的农田环境影响作了简要评价? ?     

An investigation on biological stability of product water generated by lab-scale and pilot-scale distillation systems

Material Disposal Area G is the primary low-levelradioactive waste disposal site at Los Alamos NationalLaboratory, New Mexico, and is adjacent to Pueblo of SanIldefonso lands. Pueblo residents and Los Alamos scientists areconcerned about radiological doses resulting from uptake of AreaG radionuclides by mule deer (Odocoileus hemionus) andRocky Mountain elk (Cervus elaphus), then consumption ofdeer and elk meat by humans. Tissue samples were collected fromdeer and elk accidentally killed near Area G and were analyzedfor ³H, ⁹⁰Sr, total U, ²³⁸Pu, ^{239, 240}Pu,²⁴¹Am, and ¹³⁷Cs. These data were used to estimatehuman doses based on meat consumption of 23 kg y^-1. Humandoses were also modeled using RESRAD, and dose rates to deer andelk were estimated with a screening model. Dose estimates tohumans from tissue consumption were 2.9 × 10^-3 mSv y^-1and 1.6 × 10^-3 mSv y^-1 from deer and elk, respectively,and RESRAD dose estimates were of the same order of magnitude. Estimated dose rates to deer and elk were 2.1 × 10^-4 mGyd^-1 and 4.7 × 10^-4 mGy d^-1, respectively. Allestimated doses were significantly less than established exposurelimits or guidelines.     

用热释光剂量计对哈密地区环境天然贯穿辐射水平调查

用国产ETLD-80型热释光环境剂量计调查了哈密地区环境天然贯穿辐射水平.结果表明,哈密地区室外、室内宇宙射线电离辐射空气吸收剂量率分别为(3.7±0.3 )、(3.3±0.3)×10~(-8)Gy/h,人口加权平均值分别为3.2和2.8×10~(-8)Gy/h.地球γ辐射空气吸收剂量率分别为(5.8±0.9)、(7.7±1.2)×10~(-8)Gy/h,人口加权平均值分别为5.0和6.6×10~(-8)Gy/h.天然贯穿辐射所致居民有效剂量当量为71.7μSv/a(宇宙辐射298μSv/a,地球γ辐射419μSv/a).