CYCLING OF Mn,Fe, Cu AND Zn BY EELGRASS,ZOSTERA MARINA L

Significant (P < 0.005) differences in Mn, Fe, Cu and Zn concentrations were found in different parts of eelgrass plants; i.e., roots and rhizomes, live blades, attached dead blades, and detritus. Imported vs. exported suspended particles of eelgrass blades did not differ in Mn, Fe, Cu or Zn content. Significant location effects, which varied with the type of plant tissue, were noted for Mn, Fe, Cu and Zn for three grass beds in the vicinity of Beaufort, NC. In simplified Mn, Fe, Cu and Zn budgets, eelgrass biomass is the largest biological reservoir, while eelgrass growth, senescence, and decomposition constitute the largest biological flux of these elements in this ecosystem.     

Room temperature solvent extraction for simple and fast determination of total concentration of Ca,Cu, Fe,Mg, Mn,and Zn in bee pollen by FAAS along with assessment of the bioaccessible fraction of these elements using in vitro gastrointestinal digestion

Background and aimBee pollen is recognized to be a source of different nutrients, including minerals. As a food supplement, its quality and safety due to concentrations of essential macro- and microelements, and harmful trace elements has to be verified. Fast and simple element analysis of bee-collected pollen can be regarded as an important part of its quality assurance and control. The present study aimed at developping a new method for determination of selected elements (Ca, Cu, Fe, Mg, Mn, Zn) of bee pollen based on solvent extraction and completely avoiding a high temperature treatment with concentrated reagents. In addition, in vitro gastrointestinal digestion was used to assess bioavailability of elements from this food supplement.MethodsBee pollen samples were dried and pulverized. Total concentrations of Ca, Cu, Fe, Mg, Mn, and Zn were determined by flame atomic absorption spectrometry (FAAS) in sample solutions obtained by wet digestion (WD) in concentrated HNO₃ or alternatively by solvent extraction (SE) with diluted solutions of HNO₃. Gastrointestinal digestion was mimicked using simulated solutions of gastric and intestinal juices followed by determination of Ca, Cu, Fe, Mg, Mn and Zn concentrations in the bioaccessible fraction by FAAS.ResultsA new simple and fast method for determination of total concentrations of Ca, Cu, Fe, Mg, Mn, and Zn in bee pollen was developed and validated. The method combined room temperature, two-hour SE with 0.5 mol L⁻¹ HNO₃ with FAAS measurements versus simple standard solutions. It provided precision within 1–5 % and trueness better than 8%, and was shown to be suitable for fast analysis of different polyfloral bee pollens. In vitro gastrointestinal digestion revealed that elements were well (70–85 % for Ca, Mg) and fairly (27–43 % for Cu, Fe, Mn, and Zn) bioaccessible from bee pollen. By pouring with water and swelling overnight, bioaccessibility of studied elements from such prepared bee pollen was increased on average by less than 15 % (Mn), 20 % (Ca, Cu, Fe, Zn) or 30 % (Mn).ConclusionsAvoiding long-lasting, high-temperature wet digestion with concentrated reagents, the proposed sample treatment along with FAAS provided precise and true results of total concentrations of Ca, Cu, Fe, Mg, Mn, and Zn in bee pollen. The method was simple and fast, and enabled to analyze a higher number of samples. Simulated gastrointestinal digestion of bee pollen have shown for the first time that Ca and Mg are the most bioaccessible from this bee product. Bioaccessibility of Cu, Fe, Mg, and Zn from bee pollen are close to or lower than 40 %.     

Plasma manganese, selenium, zinc, copper, and iron concentrations in patients with schizophrenia

A number of essential trace elements play a major role in various metabolic pathways. Selenium (Se), manganese (Mn), copper (Cu), zinc (Zn), and iron (Fe) are essential trace elements that have been studied in many diseases, including autoimmune, neurological, and psychiatric disorders. However, the findings of previous research on the status of trace elements in patients with schizophrenia have been controversial. We studied these elements in patients with a DSM-IV diagnosis of schizophrenia and compared them with sex- and age-matched healthy controls. Plasma Cu concentrations were significantly higher (p<0.01) and Mn and Fe concentrations were lower (p<0.05 and p<0.05, respectively) in schizophrenic patients than in controls. Se and Zn concentrations and protein levels did not differ between patients and healthy controls. These observations suggest that alterations in essential trace elements Mn, Cu, and Fe may play a role in the pathogenesis of schizophrenia. However, findings from trace element levels in schizophrenia show a variety of results that are difficult to interpret.     

Enrichment in Trace Metals (Al,Mn, Co,Cu, Mo,Cd, Fe,Zn, Pb and Hg) of Macro-Invertebrate Habitats at Hydrothermal Vents Along the Mid-Atlantic Ridge

The present study describes several features of the aquatic environment with the emphasis on the total vs. filter-passing fraction (FP) of heavy metals in microhabitats of two typical deep-sea vent organisms: the filter-feeder, symbiont-bearing Bathymodiolus and the grazer shrimps Rimicaris/Mirocaris from the Mid-Atlantic Ridge (MAR). The concentration of 10 trace elements: Al, Mn, Co, Cu, Mo, Cd, Fe, Zn, Pb and Hg was explored highlighting common and distinctive features among the five hydrothermal vent sites of the MAR: Menez Gwen, Lucky Strike, Rainbow, Saldanha, and Menez Hom that are all geo-chemically different when looking at the undiluted hydrothermal fluid composition. The drop off in the percentage of FP from total metal concentration in mussel and/or shrimp inhabited water samples (in mussel beds at Rainbow, for instance, FP fraction of Fe was below 23%, Zn 24 %, Al 65%, Cu 70%, and Mn 89%) as compared to non-inhabited areas (where 94% of the Fe, 90% of the Zn, 100% of the other metals was in the FP fraction) may indicate an influence of vent organisms on their habitat’s chemistry, which in turn may determine adaptational strategies to elevated levels of toxic heavy metals. Predominance of particulate fraction over the soluble metals, jointly with the morphological structure and elemental composition of typical particles in these vent habitats suggest a more limited metal bioavailability to vent organisms as previously thought. In addition, it is evoked that vent invertebrates may have developed highly efficient metal-handling strategies targeting particulate phase of various metals present in the mixing zones that enables their survival under these extreme conditions.     

TRACE METALS IN GIANT KELP,MACROCYSTIS

Concentrations of 38 elements present in Macrocystis tissues are listed. Mean concentrations of Cu, Zn, Fe, and Mn were similar for samples of juvenile and adult sporophytes from field sites. Cu in Macrocystis tissues rose above background levels when concentrations of 0.05 to 0.1 μm were added to the culturing medium. Above-normal accumulation for Zn occurred at 0.1 μm and for Fe at 10 μm . Tissue Mn appeared independent of the ambient Mn concentration over the ranges studied. Computations indicated that upwelling is important for N and P renewal to Macrocystis beds but may be less significant for import of trace metals.     

Aluminum,Fe, Ca,Mg, K,Mn, Cu,Zn and P in above- and belowground biomass. II. Pools and circulation in a subalpineAbies amabilis stand

Elemental concentrations of above- and belowground tissues were determined in anAbies amabilis stand in the Cascade Mountains, Washington, USA. These data were used to calculate the pools and circulation of trace elements and micronutrients on a stand level. For all elements except Al, a greater proportion (from 62 to 87%) was distributed in above- rather than belowground tissues. This contrasted sharply with the biocirculation of elements where 97% of the Al and Fe, 88% of the Cu and 67–84% of the Ca, P, and Mg of total detrital cycling was from the belowground components. Aboveground tissues, however, contributed 69% of the Zn, 65% of the K and 68% of the Mn found in annual detritus production. The proportion of total element pool circulated annually was the highest for Al (82%) and Fe (32%) followed by 13% and less for the remaining elements. Copper, Fe and Al were accumulated in root tissues, while Mn and Zn accumulated in foliage.We hypothesize that roots are an effective mechanism for avoiding Al toxicity in these subalpine ecosystems. The large root biomasses of these stands allow for high Al levels to be taken up and immobilized in roots; this is observed in the significantly higher Al accumulations in below- than aboveground tissues. The high root turnover in these stands is hypothesized to be a result of root senescence occurring in response to high Al accumulation. Furthermore, Al inputs into detritus production occur by soil horizon so that roots with high Al concentrations located in the Bhs horizon turnover and are retained within that horizon. These roots also decompose very slowly (99% decay = 456 years) due to the high Al and low Ca, Mn and Mg present in these tissues and therefore have very little impact on short-term elemental cycling.     

Influence of age, sex, and sexual activity on trace element levels and antioxidant enzyme activities in field mice (Apodemus sylvaticus and Mus spretus)

The influence of age, gender and sexual activity on both hepatic levels of some trace elements (Fe, Cu, Zn, Mn, Se) and the activities of glutathione-S-transferase (GST) and superoxide dismutase (SOD) was investigated in Wood mice (Apodemus sylvaticus) and Algerian mice (Mus spretus). Animals were taken from a riverside community of an unpolluted area of central Portugal. Adult A. sylvaticus presented the highest hepatic mean concentrations of Cu and Mn, whereas adult M. spretus had the highest Fe concentration in the liver. Moreover, an influence of age on the contents of Fe, Zn, and Mn has been observed in A. sylvaticus, whereas in M. spretus an influence of gender and sexual activity was only detected on Zn levels. In contrast, enzyme activities were not influenced by the studied variables, despite a tendency for an increase in SOD activity in sexually active M. spretus. GST activity was species dependent, whereas SOD activity was similar between species. These findings were analyzed regarding the relationship of both essential trace elements and the two antioxidant enzymes with physiological and metabolic pathways related to life cycles in the two species of mice. Results enhanced the understanding of A. sylvaticus and M. spretus as biological models, allowing their future use as bioindicators of environmental toxicity.     

氮磷肥对茶树锌硒等中微量元素吸收与分配的影响

锌（Zn）和硒（Se）及其他中微量元素（铝Al,钙Ca,铁Fe,铜Cu,锰Mn）是茶叶品质的重要指标,但茶树吸收Zn、Se能力及氮（N）磷（P）肥影响中微量元素吸收与分配的过程尚不清楚。以红壤丘陵区福鼎大白茶树为研究对象,开展Zn+Se、Zn+Se+N、Zn+Se+P、Zn+Se+N+P和对照共5种处理3次重复随机化区组试验,处理第3年春季分茶叶、成熟叶、吸收根、运输根和储藏根采集植物样品,测定其元素含量。结果表明,茶树地上和地下器官Zn和Se及其他中微量元素对N、P、Zn、Se添加的响应具分异性。与对照相比,茶树地上和地下器官Zn和Se含量均显著增加,与Zn+Se相比,施N和/或P肥仅显著提高茶叶和成熟叶Se含量（P<0.05）;与对照相比,施肥处理均显著提高吸收根和运输根Al、Fe含量以及储藏根Cu含量;运输根Mn含量表现为Zn+Se+N、Zn+Se+P、Zn+Se+N+P显著高于对照,储藏根Mn含量为Zn+Se+N+P显著高于其他处理;茶树各器官Ca含量对施肥处理无显著响应。此外,茶叶和成熟叶的Zn含量与吸收根显著正相关,而Se含量则与储藏根显著正相关。茶树具有吸收和积累Zn和Se的能力,而施N、P肥有助于提高茶叶Se含量,研究结果为红壤丘陵区培育高品质锌硒茶及营建生态高值茶园提供了依据。     

Adsorption of Cu and Zn onto Mn/Fe Oxides and Organic Materials in the Extractable Fractions of River Surficial Sediments

The roles of the extractable components (Mn oxides, Fe oxides, and organic materials) of surficial sediments in controlling metals adsorption were investigated. Cu and Zn adsorptions were conducted before and after the surficial sediments extracted with hydroxylamine hydrochloride, an oxalate solution, and H ₂ O ₂ , respectively. The extraction removed target components with extraction efficiencies from 63 to 98%. Nonlinear regression analyses of Cu and Zn adsorptions based on the assumption of additive Langmuir adsorption isotherm were employed to estimate the relative contributions of sediment components to Cu and Zn adsorptions. The results indicate that the greatest contribution to total Cu and Zn adsorption to the surficial sediments on a molar basis was from Mn oxides in the extractable fractions. Both Cu and Zn adsorption capacities of Mn oxides exceeded those of Fe oxides by approximately one order of magnitude, fewer roles were attributed to the adsorption of organic material (OM), and the estimated contribution of the residual fraction to total Cu and Zn adsorption was insignificant. These information implied that the roles of metal oxides (Fe and Mn oxides) in the extractable form of the surficial sediments, especially Mn oxides, was the most important component in controlling heavy metal transportation in aquatic environments.     

Effects of soil acidification on the chemical extractability of Fe,Mn, Zn and Cu and the growth and micronutrient uptake of highbush blueberry plants

Summary The effects of soil acidification and micronutrient addition on levels of extractable Fe, Mn, Zn and Cu in a soil, and on the growth and micronutrient uptake of young highbush blueberry plants (Vaccinium corymbosum L. cv. Blueray) was investigated in a greenhouse study.Levels of 0.05M CaCl₂-extractable Fe, Mn, Zn and Cu increased as the pH was lowered from 7.0 to 3.8. However, the solubility (CaCl₂-extractability) of Fe and Cu was considerably less pH-dependent than that of Mn and Zn. With the exception of HCl-and DTPA-extractable Mn, micronutrients extractable with 0.1M HCl, 0.005M DTPA and 0.04M EDTA were unaffected or raised only slightly as the pH was lowered from 6.0 to 3.8. Quantities of Mn and Zn extractable with CaCl₂ were similar in magnitude to those extractable with HCl, DTPA and EDTA whilst, in contrast, the latter reagents extracted considerably more Cu and Fe than did CaCl₂. A fractionation of soil Zn and Cu revealed that soil acidification resulted in an increase in the CaCl₂- and pyrophosphate-extractable fractions and a smaller decrease in the oxalate-extractable fraction.Plant dry matter production increased consistently when the soil pH was lowered from 7.0 to 4.6 but there was a slight decline in dry matter as the pH was lowered to 3.8. Micronutrient additions had no influence on plant biomass although plant uptake was increased. As the pH was lowered, concentrations of plant Fe first decreased and then increased whilst those of Mn, and to a lesser extent Zn and Cu, increased markedly.     

Reduction of Fe(III), Mn(III), and Cu(II) chelates by roots of pea (Pisum sativum L.) or soybean (Glycine max)

Neither the reduction of Fe(III) to Fe(II) by roots nor its induction by Fe-deficiency are unique characteristics of the reductive activities of roots. We show that chelated Mn(III) or chelated Cu(II), as well as chelated Fe(III), may be reduced by Fe-stressed roots of pea (Pisum sativum L.). Deficiency of Fe stimulated the reduction of Fe(III)EDTA about 20-fold, the reduction of Mn(III)CDTA about 11-fold, the reduction of Cu(II)(BPDS)₂ about 5-fold, and the reduction of Fe(III)(CN)₆ by only about 50%. Not only are metals other than Fe reduced as part of the Fe-stress response, but deficiencies of metals other than Fe stimulate the reductive activity of roots. We show that depriving peas or soybeans (Glycine max) of Cu or Zn stimulates the reduction of Fe(III).     

秦艽药材及其生长土壤中无机元素含量特征及相关性分析

该研究采用原子吸收分光光度法和火焰光度法,测定云南20个种植地的秦艽及其生长土壤中无机元素的含量,探讨药材中无机元素分布特征,并对药材中无机元素含量与土壤中无机元素含量的相关性进行了分析。结果表明：云南秦艽药材无机元素的含量呈现K>Ca>Mg>Fe>Mn>Zn>Cu有规律的分布态势;通过相关性分析、主成分分析和逐步回归分析发现秦艽的特征元素为K、Cu、Ca和Zn;药材中钾含量与土壤中锌,钙与土壤中锰和铜,锰与土壤中钙和镁,铜与土壤中钾和锌元素含量间均分别显著负相关;而药材中镁含量与土壤中钙和镁,铁、铜与土壤中铁元素含量间均呈显著正相关。对秦艽各无机元素含量影响最大的因子是秦艽生长土壤有效钙,有效铁和有效锌其次,最后为有效锰。该研究结果为秦艽道地性成因及适宜栽培区域的选择提供了参考,为秦艽资源合理利用和GAP研究以及从无机元素的角度品评药材品质提供了理论依据。     

Effects of minerals on the production of valine byAerobacter aerogenes

A study has been made on the mineral requirements of a strain ofAerobacter aerogenes for the production of valine. It was observed that K₂HPO₄ and MgSO₄]. 7 H₂O were required at concentrations of 0.1% and 0.05% respectively while the optimum level of each of the trace elements Fe and Mo was 1 μg/ml. NaCl, KCl and trace elements like Mn, Ni, Co, Cu and Zn had an adverse effect on the production of valine. The requirements for metals except Mg for growth of the organism and valine production are different.     

Effects of six trace metals on calcium fluxes in brown trout (Salmo trutta L.) in soft water

Summary Calcium fluxes were measured simultaneously in brown trout fry maintained in an artificial soft water medium of [Ca] 20 mol·l^-1 and pH 5.6, and exposed to each of six trace metals (Al, Cu, Fe, Ni, Pb, and Zn). The trace metal concentrations represented typical and maximum levels found in acid waters experiencing declining fishery status. In the absence of trace metals, evidence is presented which suggests that ca. 91% of Ca taken up from the external medium was by extraintestinal active transport. Calcium efflux was stimulated by both concentrations of Al, Cu, Fe, and Pb. Efflux was also stimulated by [Ni] 170 nmol·l^-1 and [Zn] 3000 nmol·l^-1. In some cases, response to increased efflux was stimulation of influx. Lack of stimulation of influx resulted in negative net Ca fluxes. Net Ca losses were recorded at both concentrations of Al, Pb, and Ni, lower concentrations only of Fe, and higher concentrations only of Cu and Zn.Abbreviations J _in influx - J _net net flux - J _out efflux Henceforward in this paper, chemical elements are referred to by their chemical symbols rather than by full names     

Trace element studies on four species of Fusarium.

Trace element studies were carried out on four species of Fusarium: F. moniliforme, F. solani, F. poae and F. bulbigenum. Out of fifteen trace elements tested, Fe, Zn, Mn, Cu, Mo and B were found to be essential for growth and sporulation of all these species of Fusarium. Optimum concentrations in ppm of essential trace elements of these fungi were as follows: F. moniliforme Fe 1.0, Zn 0.1, Mn 0.1, Cu 0.1, Mo 0.1, B 1.0-10.0; F. solani Fe 1.0, Zn 10.0, Mn 0.1, Cu 0.01, Mo 1.0, B 0.1; F. poae Fe 1.0, Zn 0.1, Mn 0.1, Cu 1.0, Mo 0.1, B0.1, F. bulbigneum Fe 10.0, Zn 1.0, Mn 1.0, Cu 1.0, Mo 0.01, B 1.0. Concentrations higher than the optimum were inhibitory to the respective fungi.     

Effects of pruning on the concentration of trace elements in Colophospermum mopane leaves

Despite the nutritional value of Colophospermum mopane to browser's diets, there is still insufficient knowledge on the effect of browsers on concentrations of these trace elements. A field experiment was conducted in Musina Nature Reserve, Limpopo Province, South Africa, to determine the effect of pruning on the concentration of trace elements in mopane leaves. Samples were analysed for iron (Fe), manganese (Mn), boron (B), molybdenum (Mo), copper (Cu), zinc (Zn), cobalt (Co), fluoride (F) and selenium (Se) using the inductively coupled plasma atomic emission spectrometry technique. The effect of pruning was tested using the two‐tailed t‐test: two‐sample assuming equal variance and two‐tailed Mann–Whitney U‐test. Results showed that the concentration of trace elements in the control and pruned trees varies slightly through the year. Fe, Mn, Mo, Cu, Zn and Se are higher during leaf flush, but declined as the leaves matured and aged. This study concluded that simulated browsing had no significant effect on the concentration of trace elements in the mopane leaves. Seasonal variation in the amount of trace elements has implications on the distribution of browsers in the mopane woodland.     

Effects of nitrogen and water addition on trace element stoichiometry in five grassland species

A 9-year manipulative experiment with nitrogen (N) and water addition, simulating increasing N deposition and changing precipitation regime, was conducted to investigate the bioavailability of trace elements, iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn) in soil, and their uptake by plants under the two environmental change factors in a semi-arid grassland of Inner Mongolia. We measured concentrations of trace elements in soil and in foliage of five common herbaceous species including 3 forbs and 2 grasses. In addition, bioaccumulation factors (BAF, the ratio of the chemical concentration in the organism and the chemical concentration in the growth substrate) and foliar Fe:Mn ratio in each plant was calculated. Our results showed that soil available Fe, Mn and Cu concentrations increased under N addition and were negatively correlated with both soil pH and cation exchange capacity. Water addition partly counteracted the positive effects of N addition on available trace element concentrations in the soil. Foliar Mn, Cu and Zn concentrations increased but Fe concentration decreased with N addition, resulting in foliar elemental imbalances among Fe and other selected trace elements. Water addition alleviated the effect of N addition. Forbs are more likely to suffer from Mn toxicity and Fe deficiency than grass species, indicating more sensitivity to changing elemental bioavailability in soil. Our results suggested that soil acidification due to N deposition may accelerate trace element cycling and lead to elemental imbalance in soil–plant systems of semi-arid grasslands and these impacts of N deposition on semi-arid grasslands were affected by water addition. These findings indicate an important role for soil trace elements in maintaining ecosystem functions associated with atmospheric N deposition and changing precipitation regimes in the future.     

Copper,iron, manganese,and zinc content of hair from two populations of rhesus monkeys

The concentrations of the elements copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn) in hair of caged (in Maryland) and freeranging (in Puerto Rico) rhesus monkey populations were determined. Significant chronological age-related decreases were evident for the trace elements Mn and Zn in both populations (P<0.01) and for Cu and Fe in free-ranging monkeys (P<0.005). The only overall gender difference was higher hair Mn concentration in freeranging males than in females (P<0.03). There were no significant differences in hair Cu, Fe, or Mn related to pregnancy status. Hair Zn was lower in samples from pregnant than from nonpregnant monkeys from the caged monkeys (P≤0.05), but did not differe in the freeranging monkeys. Comparison of the two populations revealed that hair Zn levels were significantly higher in caged vs free-ranging animals (P<0.001). We attribute this higher hair Zn in the caged monkeys to contact and ingestion of Zn from their galvanized enclosures. Hair iron levels were significantly higher (P<0.001) in free-ranging monkeys, possibly as a result of Fe-rich soil ingestion from their environment. These data support continued investigation of the use of hair as an indicator of the exposure of large groups or populations to potentially high levels of specific minerals, and the use of nonhuman primates as models for the study of trace element deficiency and/or toxicity in humans. Prelliminary reports of portions of these data were presented at the 69th Annual Meeting of the Federation of American Societies for Experimental Biology, April 1982, New Orleans, LA (B. M. Marriott, J. C. Smith, R. Jacobs, A. O. Jones, M. J. Kessler, and R. Rawlins,Fed. Proc. 41:770, [1982]) and in a symposium at the 6th Annual Meeting of the American Society of Primatologists, 1983, East Lansing, MI (B. Marriott, J. C. Smith, R. Jacobs, A. O. Lee Jones, R. Rawlins, and M. J. Kessler,Am. J. Primatol. 4(3): 157 [1983]; B. Marriott, J. C. Smith, Jr., R. M. Jacobs, A. O. Lee Jones, R. Rawlins, and M. J. Kessler, inThe Cayo Santiago Macaques, R. Rawlins and M. J. Kessler, eds., SUNY Press, Albany, NY, pp. 219–231 [1986]).     

Effects of liming on the extractability of Fe,Mn, Zn and Cu from a peat medium and the growth and micronutrient uptake of highbush blueberry plants

Summary Levels of extractable micronutrients in a peat and the growth and nutrient uptake of young highbush blueberry plants (Vaccinium corymbosum L cv. Blueray) were studied in a greenhouse experiment in response to liming and two rates of addition of Fe, Mn, Zn and Cu.Levels of extractable micronutrients showed different trends with liming depending upon the extractant used and the element being considered. Levels of 0.05M CaCl₂-extractable Fe, Mn and Zn decreased as the pH was raised whilst those of Cu first decreased and then increased again. There was a general decline in 0.1M HCl-extractable Fe, Mn and Cu with increasing pH but levels of Zn were not greatly affected. Levels of 0.005M DTPA extractable Fe, Mn Zn and Cu generally declined but those extractable with 0.04M EDTA were either unaffected or increased as the pH was raised. Levels of CaCl₂-extractable Mn and Zn were the same order of magnitude as those extractable with HCl, DTPA and EDTA. In contrast, the latter reagents extracted considerably more Fe and Cu than did CaCl₂.Dry matter yields of plants were increased as the pH was raised from 3.9 to 4.3 but then decreased markedly as the pH was raised further to 6.7. With increasing pH, concentrations of plant Fe generally increased those of Mn were decreased and those of Zn and Cu were not greatly affected except for a marked decline in plant Cu at pH 6.7.     

南四湖区农田土壤有机质和微量元素空间分布特征及影响因素

基于地统计学和GIS技术相结合的方法,研究了南四湖区农田土壤有机质和微量元素的空间分布特征及其影响因素。结果表明,土壤有机质和微量元素均属中等变异程度,除硼符合正态分布外,其余土壤属性均符合对数正态分布。结构分析表明,除硼为纯块金效应外,土壤有机质和其它微量元素空间自相关性较强,其中结构性因素起主导作用。克里格插值结果表明,土壤有机质分布总体趋势为由北向南逐渐降低,锰、铜、锌分布总体趋势为中部高,南北两端低。影响因素分析表明,土壤类型、耕层质地、坡度、土地利用类型和地貌类型对土壤有机质均有显著影响。土壤类型主要是由于成土母质的差异影响土壤有机质的高低与分布,随质地由砂变粘、坡度由低变高,土壤有机质含量逐步升高,田间管理水平的差异是造成不同土地利用类型下土壤有机质含量差异的主要原因。微量元素中,除硼不受影响外,铁、锰、铜和锌与土壤类型、耕层质地、坡度、土地利用类型和地貌类型密切相关。