黑藻对沉积物及土壤中不同形态磷的利用与转化

利用同一区域湖泊和河流沉积物及土壤培养黑藻,运用化学连续提取法对底质中磷的不同形态进行分离,同时分析黑藻生物量及底质中上覆水和间隙水中磷浓度的变化,并对底质中生物可利用磷进行了估算,揭示沉水植物对底质中不同形态磷的利用与转化规律。结果表明,底质中弱吸附态磷、可还原性磷（RSP）是黑藻利用的主要磷形态;土壤与沉积物相比不利于黑藻生长,营养水平高的河流沉积物有利于黑藻初期生长,但容易使其早衰;沉积物作底质上覆水和间隙水磷浓度主要受底质中RSP含量的控制;土壤作底质上覆水和间隙水磷浓度主要受弱吸附态磷控制;黑藻能促进底质中磷向可利用态转化;黑藻对土壤中生物可利用磷的利用率比沉积物低。     

疏浚对巢湖重污染入湖河流沉积物中污染物赋存及释放的影响

以巢湖重污染入湖河流双桥河为研究对象,研究了底泥疏浚对水质以及沉积物中总氮、总磷和有机质的短期影响及长期效应.结果表明,双桥河水质的季节变化显著,受上游城市污水及周边面源污染的影响,疏浚对水质改善作用不明显.表层沉积物中总氮、总磷及有机质含量在疏浚结束后1个月有所降低,但是2年后分别回复到疏浚前的189.77%、111.62%和152.87%.疏浚结束2年后,沉积物中磷主要以钙磷和有机磷的形式存在,铝磷和铁磷的含量较少,弱结合态磷的含量最低;但是表层沉积物中的弱结合态磷、铝磷和铁磷结合态磷含量较疏浚前分别升高了728.32%、13.52%和37.73%,并呈现出表层富集现象,存在较高的污染物释放风险.这可能是由沉积环境改变、外源污染未得到有效控制引起的.因此,为了维持疏浚的长期效果,应该对外源污染源进行有效控制.     

Amounts,forms, and management of nitrogen and phosphorus export from agricultural peatlands

Peatlands provide a setting that is well suited for cranberry agriculture in the Northeastern United States. However, misconceptions exist about the amounts and forms of nitrogen (N) and phosphorus (P) export from cranberry farms. In this study, we report inorganic and organic forms of N and P export from five peatlands cultivated for cranberry production in southeastern, Massachusetts, United States. We then compare N loading rates among cranberry farms in southeastern Massachusetts, row crop farms in the Midwestern United States, and uncultivated peatlands in the United States and United Kingdom. Based on a fluvial mass balance analysis, we find that nonriparian cranberry farms export 2.56 kg of P ha⁻¹ year⁻¹of total P and 12.1 kg of N ha⁻¹ year⁻¹of total N. Total N export from riparian or “flow through” farms is two times higher than nonriparian farms due to less retention of N fertilizer in the vadose zone of riparian farms. Gross total N export from riparian and nonriparian cranberry farms consists of 35% particulate organic N, 26% dissolved organic N, 31% ammonium (NH₄⁺), and 8% nitrate (NO₃⁻). The low proportions of NO₃⁻ export (13% of total dissolved N [TDN]) for cranberry farms differ from NO₃⁻ export for row crop farms (75% of TDN; p < .001) but not for uncultivated peatlands (17% of TDN; p = .61). Despite being highly modified by fertilizers and artificial drainage, low NO₃⁻ export (2.2 kg of N ha⁻¹ year⁻¹) from cranberry farms is consistent with field measurements of rapid N turnover in uncultivated peatlands. This finding suggests that state-funded wetland restoration efforts to restore denitrification in retired cranberry farms may be limited by NO₃⁻ rather than soil moisture or organic matter.     

太湖钩虾种群时空分布特征及与环境因子关系分析

在对太湖湖滨带钩虾种群空间分布前期调查的基础上,于2013年4月、8月和11月对太湖底栖动物钩虾种群的分布和水质情况进行了调研。钩虾种群密度在太湖水域空间上表现出明显的差异性,其高值区域出现在太湖的西北部,且随季节变化较大,其中,冬季钩虾种群密度最高。通过主成分分析(PCA)筛选出影响太湖水质的主要指标为氮和磷(方差解释率为52.2%),相关分析表明钩虾种群密度对数值与第一主成分氮和磷呈正相关,而与第二主成分透明度呈负相关。研究表明钩虾种群空间分布的差异与氮磷水平关系最密切,其次是透明度。     

U-Pb zircon dating,Sr-Nd isotope and petrogenesis of Sarduiyeh granitoid in SE of the UDMA,Iran: implication for the source origin and magmatic evolution

ABSTRACT

The Sarduiyeh granitoid (SG) is intruded in the southeastern part of the Dehaj-Sarduiyeh volcano-sedimentary belt in the southeastern end of the Urumieh-Dokhtar Magmatic Arc (UDMA) in Iran. The medium-to-coarse-grained granitoid unit, with granular texture consists mainly of diorite, tonalite, granodiorite and monzogranitic rocks. Mineralogically, these rocks consist mainly of plagioclase, K-feldspar, quartz, biotite and hornblende. The whole rock geochemical analyses indicates that the SG is calc-alkaline, I-type, metaluminous, enriched in large ion lithophile elements (LILE; such as K, Cs, Pb) and depleted in high field strength elements (HFSE; such as Ti, Nb, Ta, Zr). Chondrite normalized plot of SG rare earth elements (REE) show light rare earth element enrichments with (La_N/Yb_N = 2.44–8.68) and flat heavy rare earth element patterns with (Gd_N/Yb_N = 1.02–1.36). The rather high Y (av. 19.35 ppm), low Sr content (av. 293.76 ppm) and low Cr and Ni contents (av. 20.1 and 4.69 ppm, respectively) of the SG demonstrate its normal calc-alkaline and non-adakitic nature, the features of Jebal Barez-type granitoids. The geochemical characteristics and isotopic composition, low I_Sr (0.7046–0.7049) and positive ?^tNd (+3.4 to +4.03) values, of the SG suggest that its parental magma formed as a result of partial melting from metabasic rocks of lower crust in a subduction-related arc setting. Fractionation of an assemblage dominated by plagioclase, K-feldspar, amphibole and magnetite may have been responsible for the evolution of the SG magma. U-Pb zircon geochronology gives an age of 27.95 ± 0.27 Ma for the SG, suggesting that the final collision between the Arabian plate and Central Iranian microcontinent may have happened in the Late Oligocene.     

Phosphorus storage,transport and export dynamics in the Foron River watershed

Phosphorus (P) export from the Foron River watershed was intensively monitored. Water was analysed for total P, soluble total P, soluble orthophosphate and suspended solids. Watershed soils and river sediments were sampled and the size fraction <0·2 mm analysed for total P, water extractable P, bioavailable P, 1 minute exchangeable P and P fixation capacity. Interstitial waters were analysed for soluble total P. Four hydrological conditions recurred, two during low river flows and two during increased flow. The first occurs in dry weather with a constant or decreasing flow over at least seven days and when there is no surface runoff. Exported phosphorus, predominately soluble and bioavailable, is from point sources. Phosphorus inputs exceed P export so P accumulates in the river. The second condition occurs when a small storm flow increases the average seven-day flow to exceed the preceding weekly average. Phosphorus export exceeds P inputs and originates from urban runoff, point sources and release of P stored in the river. Exported P is largely particulate but highly bioavailable. The third condition is when substantial runoff follows at least a seven-day period of constant or decreasing flow. Phosphorus export is from diffuse urban runoff. All the P stored is exported. Exported P is highly bioavailable. High concentrations and fluxes of P export are often seen. The fourth condition happens when the soils are wet and increased flow is from both urban and agricultural runoff. Phosphorus export from diffuse agricultural runoff predominates and is largely not bioavailable. Phosphorus concentrations are low but export fluxes are high when flows are high. These hydrological conditions, when integrated with concepts of mass balance define a phosphorus export typology comprising four regimes. These regimes explain total phosphorus (TP) storage, transport and export patterns, changes in P speciation and allow identification of probable sources of TP in the Foron river watershed. © 1998 John Wiley & Sons, Ltd.     

Soil water movement and nutrient cycling in semi-arid rangeland: vegetation change and system resilience

Recent decades have seen rapid intensification of cattle production in semi-arid savannah ecosystems, increasingly on formalized ranch blocks. As a result, vegetation community changes have occurred, notably bush encroachment (increased bush dominance) in intensively grazed areas. The exact causes of this vegetation change remain widely debated. Previous studies have suggested: (i) increased leaching of water and nutrients into the subsoil in intensively grazed areas provides deeper rooting bush species with a competitive advantage for soil water and nutrients, and (ii) nutrient leaching may be exacerbated by nutrient inputs from cattle dung and urine. Our research in the Eastern Kalahari showed that in infertile sandy soils both the magnitude of soil water and concentration of soil nutrients leached into the subsoil is largely unaffected by the ecological and biochemical effects of increased cattle use. We found that despite the high soil hydraulic conductivity ( &greaterno;12 cm h⁻¹), relatively high subsoil moisture contents and the restriction of water movement to matrix flow pathways prevent leaching losses beyond the rooting zone of savannah grass species. No significant differences in patterns of soil water redistribution were noted between bush dominant and grass dominant sites. We also found that the low nutrient status of Kalahari soils and leachate movement as matrix flow combine to allow nutrient adsorption on to soil particles. Nutrient adsorption ensures that nitrogen and phosphorus cycling remains topsoil dominated even following the removal of vegetation and direct nutrient inputs in cattle dung and urine. This conclusion refutes environmental change models that portray increases in the leaching of soil water and available nitrogen as a major factor causing bush encroachment. This provides a possible explanation for the now widely cited, but hitherto unexplained, resilience of dryland soils. We suggest that infertile sandy soils appear resilient to changes in soil water distribution and nutrient availability caused by increased cattle use. Hence, soil characteristics contribute to the resilience to permanent ecological change that is increasingly recognized as an attribute of semi-arid rangelands. © 1998 John Wiley & Sons, Ltd.     

Study of colloidal phosphorus variation in estuary with salinity

The variation of colloidal phosphorus with salinity in estuary was studied in this paper, which was compared with those of particle and truly dissolved phosphorus with the purpose of ˉnding out the similarities and di?erences between their behaviors in the estuary. Distribution patterns of phospho- rus in particle, colloidal and truly dissolved phase at di?erent salinities and their relationships with suspended particulate matter were also studied to understand the transformation and transporta- tion of colloidal phosphorus in estuarine area. The result showed that the concentrations of total colloidal phosphorus, organic colloidal phosphorus and inorganic colloidall phosphate all descended from river-end to sea-end, illustrating their terrigenous source. Ratios of organic to total colloidal phosphorus decreased with salinity's increment, indicating that organic phosphorus was in°uenced by scavenging process of colloid more signiˉcantly as compared with inorganic phosphate. Both of the phosphorus variation tendencies and the proportion between organic and inorganic phosphorus in colloidal phase was similar with that in truly dissolved phase while di?erent from that in particle phase.     

Phase fractionation and oil-condensate mass balance in the South Marsh Island Block 208–239 area,offshore Louisiana

Phase fractionation can strongly deplete oil of its volatile compounds in a regular and characteristic fashion. This process has affected oils to a remarkably uniform extent throughout the 30 × 15 km South Marsh Island 208–239 and Vermilion 30–31 area (including the Tiger Shoal, Starfak, Mound Point, Lighthouse Point, Amber, Trinity Shoal, and Aquamarine fields) just offshore Louisiana. Fractionation of the original “parent” oil likely occurred in the deep, relatively flat-lying Rob L sand that underlies the area, and produced gas-washed oils (mean API 33°) and gas condensates (mean API 50°) in a volume ratio of 1:3.5. Both fractionated oil and vapor migrated from the fractionation site to shallower reservoirs. However, the estimated ultimate production ratio of gas-washed oil to gas condensate in this group of fields is 1:0.32, about 11 times higher than would be expected on mass balance considerations alone. Thus, there is an apparent deficiency of producible gas condensate relative to the amount of producible oil for the entire study area and for every field in that area. In the case of the Tiger Shoal field, the ratio of industry-estimated ultimately producible oil to gas condensate is 1:1.1. Based on the production data, we conclude that either there is an additional 6.4 × 10⁶ m³ (43 MMbbl) of undiscovered and/or unproduced condensate in the area or that condensate has escaped preferentially in vapor form to the seafloor. The well-studied and nearly depleted Tiger Shoal field provides a good example of how chemical data can be analyzed in a way that contributes insight into the phase fractionation process and the remaining exploration potential of an area.     

氮、磷对大亚湾大鹏澳海区浮游植物群落的影响Ⅱ种类组成

根据2005年4－5月（春季）、8月（夏季）和11月（秋季）对大亚湾大鹏澳海区表层的现场调查结合营养盐加富实验,探讨了不同季节氮（NO3－或脲氮 (urea)）和无机磷（PO43－）营养元素对浮游植物种类组成的潜在影响。大鹏澳海区浮游植物优势种有明显季节变化,秋季种类组成的平面变化最明显。春季浮游植物平均细胞密度最高但多样性指数最低。实验结果显示,春季至夏季浮游植物优势种翼根管藻模式变型Rhizosolenia alata f. genuina、丹麦细柱藻Leptocylindrus danicus和绕孢角毛藻Chaetoceros cinctus之间的演替可能受氮、磷条件变化的控制。夏季优势种菱形海线藻Thalassionema nitzschioides和威氏海链藻Thalassiosira weissflogii之间的演替可能受营养条件外的因素控制。尽管磷被认为是该海区浮游植物生长的主要限制因子,但夏季无机氮磷比值较高的实验组中未出现磷限制现象,无机氮磷比值的变化对浮游植物种类组成也没有显著影响,而秋季氮对浮游植物种类组成有较明显的潜在影响。