外源硒（Se(4＋)和Se(6＋））污染对土壤酶活性的影响

利用盆栽试验,研究了不同浓度、不同价态外源硒（Se4＋、Se6＋）对连续种植小白菜土壤中过氧化氢酶、脱氢酶、脲酶和碱性磷酸酶活性的影响,为土壤硒污染的生态风险评价和管理提供科学依据。结果表明：低浓度硒对土壤酶活性有不同程度的激活效应,而高浓度硒对4种土壤酶均产生抑制作用;外源硒对脲酶及脱氢酶活性的抑制作用大于碱性磷酸酶和过氧化氢酶。外源Se4＋及Se6＋浓度与土壤脲酶活性间都存在显著的负相关（P〈0.01）,且同浓度两个价态硒差异显著（P〈0.05）,说明脲酶可作为土壤硒污染程度的生态风险评价的生物指标;而过氧化氢酶、脱氢酶及碱性磷酸酶只能表征一定时间段内土壤硒污染的程度。土壤酶的ED5（0生态剂量）均随硒施入时间的延长而增大,以脲酶的ED50值最小,Se6＋的ED50小于Se4＋,生态毒性大于Se4＋。     

Transformation and Bioavailability of Selenate and Selenite Added to a Nicotiana tabacum L. Planting Soil

Selenium (Se) is an essential nutrient for humans and is beneficial for plant growth. To investigate the transformation and bioavailability of Se in tobacco planting soil, selenite and selenate were applied. A pot experiment and sequential extraction scheme were used to investigate the Se contents in different forms in soils treated with Se. A series of equations were applied to model the transformation behavior of Se in this study. The results showed that the forms of selenium were increased significantly by applying the different valence state of water-soluble selenium. The carbonate-bound and iron-manganese (Fe-Mn) oxide–bound species were improved in selenite-added soil, whereas the soluble and exchangeable forms were increased in selenate-added soil. Michaelis-Menten equation fitting results indicated that estimated maximal selenium contents of leaves, stems, and roots in selenate-added soils were 1.83, 15.81, and 20.98 times larger than in selenite-added soils. The utilization levels of selenate were 4.3 to 7.9 times larger than selenite for Nicotiana tabacum L. In conclusion, the bioavailability and mobility of selenate were greater than selenite in Nicotiana tabacum L. planting soil.     

Application of Response Surface Methodology to Analyze the Effects of Soil/Liquid Ratio,pH, and Incubation Time on the Bioaccessibility of PAHs from Soil in In Vitro Method

Water, Air, & Soil Pollution - Central composite design using response surface methodology was employed to optimize soil/liquid ratio (S/L), pH, and incubation time for polycyclic aromatic...     

Quantification and In Vitro Bioaccessibility of Selenium from Osborne Fractions of Selenium‐Rich Cereal Grains

Cereal crops cultivated in the seleniferous belt of Punjab, India, were observed to hyperaccumulate a significantly high concentration of selenium (20–123 µg/g). Selenium concentration (µg/g) in storage proteins of wheat, maize, and rice, namely, albumin (401, 280, and 29, respectively), globulin (264, 192, and 242, respectively), glutelin (563, 359, and 178, respectively), and prolamin (629, 339, and 257, respectively) indicated variable selenium levels, with prolamin contributing significantly higher levels of selenium when compared with other proteins with reference to the total concentration of the protein fraction. The simulated gastric and gastrointestinal digestion studies indicated better accessibility of selenium during intestinal digestion, with variability across proteins and cereal types. The observations provide an insight into the bioavailability of selenium in selenium‐rich cereal grains, used in the study, and their potential use as source for selenium supplementation to deficient populations, or as “bioactive” selenium‐rich nutraceutical blends for health benefits.     

对开发建设项目水土保持投资概(估)算编制有关问题的探讨

开发建设项目水土保持投资概 (估 )算编制既要体现水土保持工程特点 ,又要与主体工程造价编制相结合。对在各行业工程造价编制规定及定额体系多样、标准不一的情况下 ,水土保持工程投资概 (估 )算编制中的有关问题进行了分析 ,并提出了建议     

~7Be示踪法估算土壤侵蚀速率模型计算结果比较

在总结现有7Be示踪法估算土壤侵蚀速率模型的基础上,通过坡耕地径流小区野外模拟降雨实测侵蚀资料,比较了Walling、杨明义和Wilson等所建的利用7Be示踪法估算土壤侵蚀速率模型的计算结果,并验证各模型的准确度。结果表明,对于不发生细沟侵蚀的小区,3个模型的计算值都有较高的准确度,但Wilson模型相对其它两个模型计算结果误差较大;对于发生细沟侵蚀的小区,Walling模型和杨明义模型估算坡面细沟间侵蚀量的绝对差值较小,但大于不发生细沟侵蚀小区的绝对差值;Wilson模型能够比较准确计算坡面的总侵蚀量,与实测值相比较,相对误差为3.59%～14.47%,不发生细沟侵蚀的小区相对误差大于发生细沟侵蚀的小区。随着侵蚀强度的增大,3个模型计算结果的准确度呈降低趋势。     

Extraction and Analysis of Soil Solution of Phosphate Rock and Acid Treated Soil

Abstract

Increasing basic phosphate rock (PR) rates and acid loads were applied to an acidic sandy soil in a laboratory experiment. ‘Total’ amounts of potentially toxic elements in the soil and PR samples were determined by inductively coupled plasma (ICP) spectrometry after acidic, microwave digestion. Soil solution was extracted from wet soil by centrifugation with a speed corresponding to the suction power exerted by plants at the conventional wilting point. Addition of PR generally decreased rather than increased metal concentrations in the soil solution because of its pH elevating, immobilizing effect. Except for Pb, the extreme acid treatment compensated for the immobilizing effect of PR. Release of Cd (expressed as soil solution concentration in percentage of the total amount in soil+PR) was generally highest among elements at every treatment, and Cr was the least mobile metal. The one‐time, high rate of PR application did not make a direct environmental risk probable.     

Rapid, Micro-Methods to Estimate Plant Silicon Content by Dilute Hydrofluoric Acid Extraction and Spectrometric Molybdenum Method

By treating 0.5 g DW of a plant sample directly with 10 ml of a dilute hydrofluoric acid solution (HF solution, 1.5 M HF—0.6 M HCl), all the silica in plant (as much as 150 mg SiO₂) was dissolved within 1 h. After dilution of the extract with 40 mL of distilled water, the silica in the extract was measured by the spectrometric molybdenum yellow method. The molybdenum yellow method, in which silica in 0.1 mL of the diluted extract can be determined in 8 min, is well suited to rapid, micro-estimations of the silica content in plants. In the micro-modification, the size of the plant sample was reduced to 100 mg DW. The analytical procedure was simple, and the analytical time was less than 2 h. The method can save much labor and time, compared with the gravimetric analysis. The dissolution with HF solution and the molybdenum yellow method were also applied to the measurement of the content of silica separated by acid digestion of rice plants. Excellent agreement in the silica measurement of rice plants was confirmed among the direct extraction method, the gravimetric method and the digestion-separation-dissolution method. In the molybdenum yellow method, the addition of boric acid enabled to mask the interference of hydrofluoric acid, and the least amount of citric acid required for the elimination of phosphorus interference was proposed. In conclusion in this report, recommended methods for the rapid estimation of the silica content in rice plants were presented.     

Comparison of Disturbed and Undisturbed Soil Core Methods to Estimate Nitrogen-Mineralization Rates in Manured Agricultural Soils

Ion exchange resin?/?soil cores are a common in situ approach to estimating soil nitrogen (N) mineralization rates. However, no studies compare the two common methods of core preparation (disturbed and undisturbed). The objective of our study was to compare N mineralized and soil temperature in disturbed versus undisturbed cores of manured agricultural soils. Undisturbed cores were prepared by driving aluminum tubes (25 cm long with 10 cm inner diameter) into soil, removing the tubes, and then inserting an ion-exchange resin bag beneath the soil at the bottom of the tube. Disturbed cores were prepared with the same materials, but soil was excavated, mixed, and then filled into tubes fitted with ion-exchange resin bags at the bottom. Soil from six agricultural fields (five of which had more than 10 years of regular dairy manure application) was incubated over four time periods during summer and winter. A total of 13 soil?/?incubation-period combinations were tested. Disturbed cores tended to have more N mineralized than undisturbed cores (P < 0.10), especially in cores prepared with the lowest clay content soil. However, variability of N mineralized was lower in disturbed cores than undisturbed cores for 11 of the 13 soil?/?incubation periods. This lower variability was significant in two of the four incubation periods (P < 0.10). There was little difference in mean soil temperatures in disturbed versus undisturbed cores or within cores versus outside but adjacent to cores. However, in summer, the daily temperature range inside cores was significantly greater than the temperature range in soil outside cores (P < 0.01).     

In Vitro Effects of Agriculture Pollutants on Microcrustacean and Fish Acid Phosphatases

Chemical inputs from agricultural activities represent a threat to aquatic biota and its biochemical systems. Among these systems, acid phosphatases are involved in autophagic digestive processes, decomposing organic phosphates, signaling pathways, and other metabolic routes. In vitro tests are helpful to generate hypotheses about pollutant mechanisms of action through comparison of the toxicity effects of these compounds. In this work, we investigated the inhibitory effects of four organic pesticides and three metals on the acid phosphatases extracted from the freshwater microcrustacean Daphnia similis and the fish Metynnis argenteus. Our results demonstrated that only the metals have considerable inhibitory effects (50% or higher) on the enzyme activities. The calculated median effect concentrations (IC50) for the enzyme inhibition were 0.139 mM Hg²⁺ (fish enzyme), 0.652 mM Cu²⁺ (fish enzyme), and 1.974 mM Al³⁺ (Daphnia enzyme). Due to the relatively low value of the inhibition parameter for Hg²⁺, its inhibitory property could be used as a tool for Hg²⁺ detection in environmental samples. The enzyme activities obtained in the presence of the inhibitors are potential data as in vivo biomarkers for metals in both aquatic species.     

Comparison of Factors Affecting Soil Nitrate Nitrogen and Ammonium Nitrogen Extraction

Extraction of soil nitrate nitrogen (NO₃ ^?-N) and ammonium nitrogen (NH₄ ⁺-N) by chemical reagents and their determinations by continuous flow analysis were used to ascertain factors affecting analysis of soil mineral N. In this study, six factors affecting extraction of soil NO₃ ^?-N and NH₄ ⁺-N were investigated in 10 soils sampled from five arable fields in autumn and spring in northwestern China, with three replications for each soil sample. The six factors were air drying, sieve size (1, 3, and 5 mm), extracting solution [0.01 mol L^?1 calcium chloride (CaCl₂), 1 mol L^?1 potassium chloride (KCl), and 0.5 mol L^?1 potassium sulfate (K₂SO₄)] and concentration (0.5, 1, and 2 mol L^?1 KCl), solution-to-soil ratio (5:1, 10:1, and 20:1), shaking time (30, 60, and 120 min), storage time (2, 4, and 6 weeks), and storage temperature (?18 ^oC, 4 ^oC, and 25 ^oC) of extracted solution. The recovery of soil NO₃ ^?-N and NH₄ ⁺-N was also measured to compare the differences of three extracting reagents (CaCl₂, KCl, and K₂SO₄) for NO₃ ^?-N and NH₄ ⁺-N extraction. Air drying decreased NO₃ ^?-N but increased NH₄ ⁺-N concentration in soil. Soil passed through a 3-mm sieve and shaken for 60 min yielded greater NO₃ ^?-N and NH₄ ⁺-N concentrations compared to other treatments. The concentrations of extracted NO₃ ^?-N and NH₄ ⁺-N in soil were significantly (P < 0.05) affected by extracting reagents. KCl was found to be most suitable for NO₃ ^?-N and NH₄ ⁺-N extraction, as it had better recovery for soil mineral N extraction, which averaged 113.3% for NO₃ ^?-N and 94.9% for NH₄ ⁺-N. K₂SO₄ was not found suitable for NO₃ ^?-N extraction in soil, with an average recovery as high as 137.0%, and the average recovery of CaCl₂ was only 57.3% for NH₄ ⁺-N. For KCl, the concentration of extracting solution played an important role, and 0.5 mol L^?1 KCl could fully extract NO₃ ^?-N. A ratio of 10:1 of solution to soil was adequate for NO₃ ^?-N extraction, whereas the NH₄ ⁺-N concentration was almost doubled when the solution-to-soil ratio was increased from 5:1 to 20:1. Storage of extracted solution at ?18 °C, 4 °C, and 25 °C had no significant effect (P < 0.05) on NO₃ ^?-N concentration, whereas the NH₄ ⁺-N concentration varied greatly with storage temperature. Storing the extracted solution at ?18 ^oC obtained significantly (P < 0.05) similar results with that determined immediately for both NO₃ ^?-N and NH₄ ⁺-N concentrations. Compared with the immediate extraction, the averaged NO₃ ^?-N concentration significantly (P < 0.05) increased after storing 2, 4, and 6 weeks, respectively, whereas NH₄ ⁺-N varied in the two seasons. In conclusion, using fresh soil passed through a 3-mm sieve and extracted by 0.5 mol L^?1 KCl at a solution-to-soil ratio of 10:1 was suitable for extracting NO₃ ^?-N, whereas the concentration of extracted NH₄ ⁺-N varied with KCl concentration and increased with increasing solution-to-soil ratio. The findings also suggest that shaking for 60 min and immediate determination or storage of soil extract at ?18 ^oC could improve the reliability of NO₃ ^?-N and NH₄ ⁺-N results.     

Comparison of In Vivo and In Vitro assays for nitrate reductase activity determination in soybean tissues

Nitrate reductase (NR) activities of soybeans (Glycine max L. Merr. Cv. Altona), grown in sand with nutrient solution containing only nitrate as a nitrogen (N) source, were compared, using one in vivo and two in vitro assays. The in vivo assay was the most sensitive of the three, particularly in measuring root NR activity. NR activity was highest in the upper most expanded leaf and declined with leaf position lower in the canopy. NR activity in the lower 6 em sections of roots was more than double that of the upper 6 cm sections. Differences in NR activity at different stem positions were not detected by the three techniques.     

塔克拉玛干沙漠地表浅层土壤热扩散率、温度和热通量计算方法的比较研究

利用塔克拉玛干沙漠大气环境观测站2008年7月30日至8月4日的土壤温度、湿度和土壤热通量观测资料,定量分析了沙漠土壤热扩散率、温度、热通量的变化规律。采用谐波法、振幅法、相位法和热传导对流法分别计算了5~20 cm沙漠土壤的热扩散率,在此基础上,以5 cm深度的土壤层为上边界条件,计算了10和20 cm深度的土壤温度和8 cm深度的土壤热通量。结果表明:谐波法计算沙漠土壤温度的精度最高,10和20 cm深度的土壤温度计算值与观测值的标准误差分别为0.167℃和0.127℃;热传导对流法对土壤温度的计算结果好于振幅法和相位法。同样,谐波法计算的沙漠土壤热通量值与观测值的误差最小,计算值与观测值的相关系数R2达到0.976,热传导对流法次之,振幅法和相位法的误差最大。     

台湾水土保持探析

由于特殊的地理条件和气候条件,台湾地区水土流失和地质灾害十分严重,每年给台湾带来巨大的损失,所以台湾当局十分重视水土保持工作,并重点开展了治山防灾、山坡地治理与山区农村规划与建设工作。近年来,台湾吸取了欧美日等发达国家的先进经验,提出在水土保持工作中运用“生态工法”这一新的理念与方法。生态工法是一个对环境、生态友善的工程概念,它包括生态系统、生态原则、生物多样性保育、人类与自然共存共乐及永续发展等几方面。台湾采用工程、农艺、植生的方法,或三种方法相互配合,使生态工法广泛应用于山坡地灾害防治、坡地保育和河溪治理中,取得了良好的水土保持效果。     

Phosphorus Uptake from Green Manures and Phosphate Fertilizers Applied in an Acid Tropical Soil

Abstract

Quantifying the relative contribution of different phosphorus (P) sources to P uptake can lead to greater understanding of the mechanisms that increase available P in integrated P management systems. The ³²P–³³P double isotope labeling technique was used to determine the relative contribution of green manures (GMs) and P fertilizers to P uptake by Setaria grass (Setaria sphacelata) grown in an amended tropical acid soil (Bungor series) in a glasshouse study. The amendments were factorial combinations of GMs (Calopogonium caeruleum, Gliricidia sepium and Imperata cylindrica) and P fertilizers [phosphate rocks (PRs) from North Carolina (NCPR), China (CPR) and Algeria (APR), and triple superphosphate (TSP)]. Dry matter yield, P uptake, and P utilization from the amendments were monitored at 4, 8, and 15 weeks after establishment (WAE). The GMs alone or in combination with P fertilizers contributed less than 5% to total P uptake in this soil, but total P uptake into Setaria plants in the GM treatments was three to four times that of the P fertilizers because the GMs mobilized more soil P. Also, the GMs markedly increased fertilizer P utilization in the combined treatments, from 3% to 39% with CPR, from 6–9% to 19–48% with reactive PRs, and from 6% to 37% with TSP in this soil. Both P_GM and the other decomposition products were probably involved in reducing soil P‐retention capacity. Mobilization of soil P was most likely the result of the action of the other decomposition products. These results demonstrate the high potential of integrating GMs and PRs for managing P in tropical soils and the importance of the soil P mobilization capacity of the organic components. Even the low‐quality Imperata GM enhanced the effectiveness of the reactive APR more than fourfold.     

CaCl_2和SrCl_2提取土壤氮钾的比较

为了探讨0.01mol L-1 CaCl2和0.02mol L-1 SrCl2提取土壤氮、钾能力的差异,用0.01mol L-1 CaCl2和0.02mol L-1 SrCl2提取14个土壤样品,再分别用流动分析和火焰光度法测定提取液中的硝态氮和亚硝态氮之和和钾的含量,以1mol L-1 KCl和1mol L-1中性醋酸铵提取液作为无机氮和钾的对照提取剂,同时选择部分土壤样品用盆栽试验测定提取数量与土壤氮、钾有效性的关系。结果表明,两种方法和对照方法提取氮和钾数量的相关性均达到p<0.01水平,对照提取剂、0.01mol L-1 CaCl2和0.02mol L-1 SrCl2对于14个土壤的硝态氮和亚硝态氮之和提取含量平均值分别为13.36、15.33和26.62mgkg-1,14个土样的提取钾含量的平均值分别为120.4、33.58和54.24mgkg-1。盆栽试验结果表明,对照提取剂和0.01molL-1CaCl2和0.02molL-1SrCl2提取氮的数量与植物吸氮量的相关性达到p<0.05显著水平,钾的相关性达到p<0.01显著水平。与对照提取剂的氮、钾分别提取相比,SrCl2和CaCl2提取剂均可大大降低样品提取中试剂费用。以上结果表明,0.01mol L-1 CaCl2和0.02mol L-1 SrCl2提取对土壤氮和钾的提取能力均可反映土壤硝态氮和亚硝态氮、有效钾的含量和供应能力,而提取能力以0.02mol L-1 SrCl2为高。     

西北地区耕地土壤真菌DNA提取方法比较

由于西北土壤理化性质的复杂性和真菌特殊性,所以从土壤中提取真菌基因组DNA就相对细菌更困难。在2种常用的土壤微生物基因组DNA提取方法与在传统提取方法的基础上,结合了一种专门适用于真菌的提取方法进行了比较,并且利用真菌28SrDNA通用引物U1/U2进行扩增。三种提取方法比较结果表明:SDS法提取的DNA纯度最低,传统CTAB-SDS的DNA产量最低,实验室的提取方法既可以提高DNA产量又可以保证DNA的片段完整性,并且本实验室的提取方法扩增效果最好,可广泛应用于西北地区土壤真菌的分子生物学研究。     

从沙棘开发利用探讨水土保持产业化发展思路

从沙棘开发利用探讨水土保持产业化发展思路焦居仁（水利部水土保持司,北京１００７６１）ＡｐｐｒｏａｃｈｔｏＩｎｄｕｓｔｒｉｌｉｚａｔｉｏｎＤｅｖｅｌｏｐｍｅｎｔｏｆＳｏｉｌａｎｄＷａｔｅｒＣｏｎｓｅｒｖａｔｉｏｎｆｒｏｍＵｔｉｌｉｚａｔｉｏｎｏｆＣｏｍ...     

新型碱性肥料治酸改土降镉的效果和机理

通过大田试验和模拟实验,研究碱性肥料治酸改土的效果、土壤pH对Cd吸附解吸热力学性能的影响,为碱性肥料治理土壤酸化和降低土壤Cd污染提供理论依据。结果表明:碱性肥料能明显提高大田土壤pH、显著降低土壤有效镉含量,明显遏制土壤酸化和土壤镉污染。施用碱性肥料是提高土壤pH和降低土壤有效镉含量的有效措施。当土壤Cd含量小于等于60mg·L^-1时,pH从5增加到9时几乎不影响Cd的吸附强度(在15.77 mg·kg^-1/(mg·L^-1)～16.67 mg·kg^-1/(mg·L^-1)之间);而当Cd含量大于60 mg·L^-1,Cd的吸附强度随pH的升高而明显增大,但吸附率随浓度的增大而减少。土壤Cd含量相等时,pH越高土壤Cd的吸附量及吸附率越大。土壤Cd的等温吸附曲线适于用Freundlich方程拟合和定量描述。土壤吸附Cd是自发反应过程,表现为Cd的吸附自由能(ΔG°)为负。同一pH下,ΔG°随着土壤Cd含量的增大而增大;ΔG°随着土壤溶液pH的升高而减小。碱性...     

Bioaccessibility of carotenoids and vitamin e from pasta: evaluation of an in vitro digestion model

The present investigation aimed to expand the knowledge of bioaccessibility of carotenoids, tocopherols, and tocotrienols from cereal products such as pasta. Because most of the published approaches assessing the bioaccessibility of lipophilic micronutrients dealt with fruits and vegetables, a prevalent in vitro digestion procedure was modified. Additionally, several digestion parameters were evaluated with regard to their impact on the bioaccessibility of carotenoids and vitamin E from pasta. Overall, the estimated values were highly dependent on the amount of bile extract present in the digestive medium and to a lesser extent on the simulated gastric pH and the incubation time with digestive enzymes. The bioaccessibility of carotenoids and vitamin E from durum wheat pasta was quite high (71 ± 5 and 70 ± 4%, respectively), whereas these micronutrients were considerably less accessible from pasta containing 10% eggs (57 ± 1 and 49 ± 5%, respectively).