Pollutant loadings from solvay waste beds to lower Ninemile Creek,New York

Concentrations of Cl, total ammonia (TNH₃), NO₃ plus NO₂, total P (TP), and soluble reactive P (SRP) were measured at two sites, located 5 km apart, on Ninemile Creek, New York, for a period of more than 8 mo. The sites bound the most recently formed Solvay waste beds, associated with the production of soda ash, that adjoin the creek. Concentrations of Cl and T-NH₃ increased on average by factors of 16.1 and 7.6, respectively, over the monitored stream reach. The estimated average loadings of these materials to the stream over this reach were 2.3 × 10⁵ and 1.2 × 102 kg d^?1, respectively. These inputs are attributable to the Solvay waste beds. The loading of Cl from this source has not changed significantly over a 4 yr period since the closure of the soda ash manufacturing facility. This is the single largest source of Cl, and the second largest source of T-NH₃, to polluted Onondaga Lake. Profiles of Cl in the lake indicated that at times the creek inflow plunges to subsurface layers as a result of its elevated density. This is at least in part a result of the creek's ionic enrichment. The concentration of SRP decreased by a factor of 2.0 on average over the study reach, probably due to adsorption to the CaCO₃ deposits that cover the stream bed in this area. However, the TP load from the creek to the lake is not significantly affected by this phenomenon.     

The distribution of nitrogen species in polluted Onondaga Lake,N.Y., U.S.A.

The temporal and vertical distributions of four N species, N0₃ ^?, NO₂ ^?, total ammonia (T-NH₃), and free ammonia (NH₃), are documented for Onondaga Lake, an urban, polluted, hypereutrophic, dimictic, lake that receives a very high load of T-NH₃. Nitrate and NO₂ ^? were lost rapidly from the hypolimnion, and T-NH₃ accumulated to high concentrations (maximum > 10 mgN L^?1), after the onset of anoxia, consistent with the lake's high level of productivity. The concentrations of T-NH₃, NH₃ and N0₃ ^? that were maintained in the epilimnion (average concentrations at a depth of 1 m of 2.81, 0.16 and 0.91 mgN L^?1, respectively), and concentrations of N0₂ ^? that developed in the epilimnion (maximum of 0.48 mgN L^?1), were high in comparison to levels reported in the literature. These elevated concentrations are largely a result of the extremely high loads of T-NH₃, and its precursors, received by the lake. Water quality problems in the lake related to the prevailing high concentrations of N species include potential toxicity effects and severe lake-wide oxygen depletion during fall turnover.     

Chloride in the pore water and water column of Onondaga Lake,N.Y., U.S.A.

The vertical distributions of Cl in the pore waters of the sediments and in the water column of Onondaga Lake, New York, are documented and used to estimate the diffusion flux of Cl across the sediment-water interface, and establish the reduction in lake concentrations that has occurred as a result of the closure of an industrial source of Cl. Despite the industrial enrichment of the water column with Cl over the last 100 yr, gradients within the upper sediments toward the overlying water of 6.9 to 8.5 × 10^?2 mg cm^?3 cm^?1 exist in the deep basins of the lake. These upwards gradients are apparently a manifestation of the salt deposits that underlie the region. The estimated diffusion flux from the sediments to the water column, 3.2 × 106 kg yr^?1, represents a small percentage of the external load during the operation of the industry (0.4%) and after its closure (1.6%). The Cl concentration has decreased approximately 70% in response to an approximately equal percent reduction in external loading, as a result of closure of the industry. This supports the position that the lake's concentrations largely reflect external loading and lake flushing associated with surface inputs.     

辽东山溪河岸林群落特征对降雨再分配及其养分特征的影响

为明确不同物种组成和群落结构的河岸林对降雨再分配及其养分特征的影响,于2014年5—10月对辽东山地典型河岸林群落(落叶松林、蒙古栎林和槭树林)大气降雨、穿透雨和树干茎流过程及其水质特征进行研究。结果表明:落叶松林、蒙古栎林和槭树林穿透雨量分别占大气降雨量的81.9%,77.9%,73.1%,树干茎流量分别占大气降雨量的1.2%,4.4%,4.3%。与大气降雨相比,穿透雨和树干茎流中铵态氮、氯离子、硝态氮和总磷的浓度较高,不同林型铵态氮、氯离子、硝态氮和总磷的浓度和输入量差异显著。不同物种组成和群落结构的河岸林通过树木的形态特征及群落的结构特征对降雨进行再分配,通过林冠表层的物理特征、化学特征和生理特性等改变降雨理化性质,加之雨量、雨强的影响共同作用使铵态氮、氯离子、硝态氮和总磷的浓度和输入量发生改变。     

An Estimation of the Nitrogen and Phosphorus Loading by Wet Deposition over Lake Maracaibo,Venezuela

In order to make an estimation of thewet deposition levels of the major nitrogen compoundsin Lake Maracaibo system, the precipitation wascollected by events at five sites located on shorearound the Lake from 1991 to 1994. Also the phosphorusconcentrations were determined in rain samples. RainpHs averaged about 5 to 6. NH₄ ⁺ levels weresignificantly higher (up to 1.44 mg L^-1NH₄-N) than NO₃ ^-plus NO₂ ^-ions which resulted in the highest pHs values in thestrait Maracaibo. The strait is the nearest zone toAmmonia Plant located upwind at the TablazoPetrochemical Complex. At the strait, theinorganic-nitrogen ((NH₄ + NO₃ +NO₂)-N) concentrations were greater than organicnitrogen levels, but at the other sites were lower.Phosphorus levels were low, ranging from undetectableto 1.5 mg L^-1; organic-P was estimated to accountfor about 40% of total-P. Total mean nitrogen wetdepositions were 6.93 kg ha^-1 yr^-1 (≈59% asNH₄-N) at the strait and 9.85–16.84 kg ha^-1yr^-1 (≈55% as organic-N) around the lakeshore.Inorganic and organic nitrogen account for about equalportions of the total nitrogen loading. These amountsrepresents ≈24% of the annual total-N inputsby the tributary rivers to the lake and aresubstantially higher than those reported in the shoreof Lake Valencia (north-central part of Venezuela) andother tropical areas. The contribution ofprecipitation to P in lake is very small; ≈0.6 kg ha^-1 of total-P are added annually. The N and Pinputs were greater than the sewage contributions. Themean molar ratio N/P is ≈22 at the straitsite whilst at lake sites the N/P ratio isconsistently >22 (about 35～1 to 100～1). The results of this preliminary study show that the atmosphere represents a significant factor for the total nitrogen loading to Lake Maracaibo system.     

Headwater lake chemistry during the spring freshet in North-Central Ontario

From data on 30 headwater lakes in north-central Ontario we found that, during the spring snow melt of 1981, all lakes underwent serious declines in alkalinity. Generally, SO₄ ^2?, alkalinity, Ca⁺ and Mg²⁺ concentrations were reduced by runoff and rain then recovered to intermediate levels after the major inputs declined. As expected, a range in responses was evident with lower alkalinity systems showing the greatest changes. The observed changes, however, were consistent with acid loading having depleted alkalinity. In calculating an input-output budget for each lake, we found that changes in Cl^?, Na⁺, and K⁺ were consistent with atmospheric inputs being the major source as the difference between the expected input and the actual contribution from rain and snow had a mean near zero. There appears to be a significant, ? 45%, watershed source of sulphate that we hypothesize is from dry deposition occurring prior to snowfall and is eluted with the melting process. With refinements to a mass balance approach explaining the watershed source of SO₄ ^2? and Al, we feel it is possible to predict springtime lake changes given a few chemical and simple morphometric variables.     

SO42-和Cl-对稻田土壤养分及其吸附解吸特性的影响

利用长期定位试验 ,比较了长期施用含SO₄^2-和Cl^- 化肥 22年后稻田土壤的 pH值、养分状况及其吸附解吸特性。结果表明 ,长期施用含SO₄^2-化肥 ,土壤有机质、速效氮和速效钾的含量较高 ,但全量氮磷钾的含量较低 ;长期施用含Cl^- 化肥 ,土壤全量氮磷钾和速效磷的含量较高 ,但pH值相对较低。长期施用含上述二种阴离子的化肥后 ,土壤对H₂PO₄^-的最大吸附量均较大 ,且在Cl^- 处理下土壤对H₂PO₄^-吸附的结合能较大 ,而SO₄^2-处理下土壤在同等吸附量时对H₂PO₄^-的解吸量相应较多。长期施用含SO₄^2-的化肥亦使土壤对钾素的供应强度较大 (ΔK0的绝对值较大 )、缓冲能力增强 (AR0值较高 ) ,而长期施用含Cl^- 的化肥时则与SO₄^2-相反     

湖南烟区土壤含氯状况及烤烟施氯效应

对湖南省主要烟区3329个土壤样品中水溶性氯含量的测定结果表明,湖南省主要烟区土壤水溶性氯含量平均为16.6.mg/kg,在烤烟生长适宜的含氯范围内。不同烟区土壤中水溶性氯含量差异较大,湘西、湘中烟区,水溶性氯含量较低的土壤所占比例较大。田间试验表明,适量的氯素营养有利于提高烤烟旺长期叶片中的叶绿素含量和植株根系活力,提高烤烟生长前期Nrase的活性;在氯含量较低的土壤上,施入烟草的钾肥总量中,氯化钾所占比例为15%～30%时(以K2O计),烟叶可增产5.2%～16.9%,产值增加1911.0～7348.5元/hm2,中上等烟比例提高10.2～11.5个百分点,烟叶的品质也得到改善,不会造成土壤氯的积累。在湖南省乃至南方一些土壤氯含量较低的地区,在烟草上可考虑适当施用一定量的氯化钾部分代替硫酸钾,以降低肥料投入成本,提高烟叶的经济效益。     

Changes in water quality in the Laflamme Lake Watershed Area,Canada

The Laflamme Lake Watershed Area is located in a sensitive region on the Canadian Shield and is subjected to wet atmospheric loading between 17 and 25 kg ha^?1 yr^?1. From 1981 to 1988, the level and fluctuations of the atmospheric deposition of acidifying substances has led to various responses in the water chemistry of headwater lakes in the area. The general trend in atmospheric inputs is a gradual increase of acidifying substances from 1981 to 1985 followed by a 2 yr decrease then a return to previous values. In the two lakes with almost no alkalinity acidification has occured throughout the 1983 to 1988 period. In the four lakes with slightly higher alkalinity values, a reversal in acidification is seen when atmospheric loading decreased in 1986. Along with the interannual trends, seasonal variability to acidification occurs with sensitivity of surface waters being highest during spring melt. Sensitivity to acidification can also be altered by watershed processes and in the Laflamme Lake Watershed, soil processes are effective in altering the acidity of precipitation before it reached the lake. In this watershed, wet atmospheric inputs of H⁺ and NO₃ ^? are larger than surface water outputs while the reverse occurs for Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl^? and SO₄ ^2?.     

柴达木盆地弃耕地成因及其土壤盐渍地球化学特征

柴达木盆地弃耕地土壤pH值一般都在 8左右 ,属于碱性土壤。土壤含盐量较高 ,其全盐量随着土层深度的增大而减少。 0～ 10cm土层中的含盐量最大 ,一般在 1～ 45gkg- 1之间。弃耕地土壤阳离子主要以K 、Na 、Mg2 、Ca2 为主 ,各阴离子在三层土体中的含量为Cl- >SO2 -4>HCO-3 >CO2 -3 。经相关分析表明 ,弃耕地土壤全盐量与Cl- 呈极显著的正相关 (p <0 0 1) ,其次为Mg2 和Ca2 (p <0 0 5) ,而与HCO-3 呈负相关 ;Cl- 与Mg2 和Ca2 呈极显著的正相关 (p <0 0 1) ,与CO2 -3 和SO2 -4呈弱的正相关 ,而与HCO-3 呈负相关 ;从而进一步说明 ,柴达木盆地弃耕地土壤为氯化物盐化土。柴达木盆地弃耕地土壤中有机质含量较少 ,0～ 3 0cm土层中有机质平均含量为 11 46gkg- 1;全氮、全磷的含量极低 ,全钾的含量较为丰富。示范试验结果分析认为 ,柴达木盆地荒漠绿洲土地退化及土壤盐碱化的发生与当地自然条件和人为不合理利用等因素有紧密的联系     

几种一年生盐生植物的吸盐能力

【目的】土壤盐渍化在新疆发生面积多,分布广,利用盐生植物对盐分的超富集能力,选育生物量大且体内盐分浓度高的品种,可有效改良盐碱地。本试验比较了几种主要盐生植物的吸收离子类型和盐分积累量,为科学合理利用盐生植物进行盐碱地改良提供科学依据。【方法】选取一年生盐角草(Salicornia europaea)、盐地碱蓬(Suaeda salsa)、高碱蓬(Suaeda altissima)和野榆钱菠菜(Atripex aucheri Moq.)为材料进行人工种植,试验地土壤为壤土和砂壤土,耕层土壤盐分均值为10.23 g/kg,p H为8.36,属于中度盐化土壤。采用完全随机排列设计,在生育早期、中期和末期采样测定植物地上、地下部分干物质量和K+、Na+、Ca2+、Mg2+、Cl-、SO2-4浓度。【结果】生育末期四种盐生植物地上生物量均占整株生物量的89%以上,高碱蓬(23302 kg/hm2)蓬野榆钱菠菜(20379 kg/hm2)盐地碱蓬(18670 kg/hm2)盐角草(9096 kg/hm2)。盐分总浓度盐角草(215 g/kg)盐地碱蓬(152 g/kg)高碱蓬(137 g/kg)野榆钱菠菜(103 g/kg)。不同植物离子含量不同,K+浓度以高碱蓬中最高,Na+、Cl-、SO2-4在盐角草中最高,Ca2+、Mg2+浓度在盐地碱蓬中最高;4种盐生植物对Na+、Cl-、SO2-4的吸收能力极强,按阴离子类型划分盐角草属于SO2-4-Cl-型盐生植物,盐地碱蓬、高碱蓬、野榆钱菠菜属于Cl--SO2-4型盐生植物;盐分积累量为高碱蓬(3499 kg/hm2)盐地碱蓬(3061 kg/hm2)蓬野榆钱菠菜(2180 kg/hm2)盐角草(2080 kg/hm2)。【结论】盐生植物对土壤的改良效果主要以生育末期刈割时单位面积从土壤中吸收的盐分总量来衡量,这取决于此时地上部分生物量与植株体内盐分浓度的大小。植物会根据其生长需求选择吸收土壤中矿物质元素,盐角草对的Na+、Cl-的吸收能力强于盐地碱蓬、高碱蓬和野榆钱菠菜,尤其对Cl-表现出极强的选择吸收能力。     

土壤高残留氮条件下施氮对夏玉米氮素平衡、利用及产量的影响

土壤残留氮是不容忽视的土壤氮素资源.通过田间小区试验研究了土壤高残留氮下不同施氮量(0、80、160、240和320 kg/hm2)对夏玉米土壤硝态氮积累、氮素平衡、氮素利用及产量的影响,分析了夏玉米的经济效益.结果表明,土壤剖面硝态氮积累量随施氮量的增加而增加,且施氮处理硝态氮积累量显著高于不施氮处理;各施氮处理土壤硝态氮在0-60 cm土层含量最高,在0--180 cm剖面呈先减少后增加的变化趋势.不施氮处理夏玉米收获后土壤无机氮残留量高达378 kg/hm2,随施氮量的增加,无机氮残留和氮表观损失显著增加.作物吸氮量、氮表观损失量与总氮输入量呈显著正相关,总氮输入量每增加l kg作物吸氮量增加0.156 kg,而表观损失量增加0.369 kg,是作物吸氮量的2.4倍.高残留氮土壤应严格控制氮肥用量,以免造成氮素资源的大量浪费.夏玉米籽粒吸氮量随施氮量的增加呈增加的趋势,氮收获指数呈降低的趋势.氮肥农学效率、氮肥生理利用率、氮肥利用率和氮素利用率在施氮量80 kg/hm2时最高,随施氮量的增加降低;增施氮肥能降低高残留氮土壤中氮肥的增产效果和利用率.综合考虑产量、氮素利用和环境效应,N 80 kg/hm2是氮素高残留土壤上玉米的合理施氮量.     

恒电荷土壤与可变电荷土壤对Cl~-和NO_3~-吸附的差异及其机理

对 3种可变电荷土壤和 4种恒电荷土壤在不同 pH、不同浓度、不同相伴阴阳离子下混合体系中Cl-和NO3-的吸附进行了测定。结果表明 ,在Cl-和NO3- 共存体系中 ,Cl-比例增大使可变电荷土壤Na+吸附量及OH-释放量增加 ,而对恒电荷土壤影响不大。Cl-和NO3-吸附量随平衡Cl-和NO3-浓度增加而增大 ,随pH升高而减少。但恒电荷土壤在上述各种条件下对Cl-和NO3-吸附均相同 ,而可变电荷土壤对Cl-吸附量大于NO3-的吸附量 ;NO3-、Cl-的选择系数为 0.51～0.78,Cl-和NO3-的相对吸附量分别为56.9%和 43.1%。在不同相伴阳离子下 ,可变电荷土壤平衡溶液Cl-/NO3-比值均小于 1,且为Na+K+Ca2+Mg2+Fe3+;而恒电荷土壤Cl-/NO3-比值为 1左右 ,且不受阳离子类型的影响。由此认为 ,Cl-和NO3-在两类土壤中均以电性吸附为主 ,恒电荷土壤对Cl-和NO3-的亲合力及吸附机理相同 ;而可变电荷土壤对Cl-的亲合力 NO3- ,Cl-存在着专性吸附     

克拉玛依人工碳汇林区景观地球化学特征与规律

以克拉玛依人工碳汇林区的土壤可溶性盐分离子、地下水矿化度和植被为研究对象, 综合运用描述性统计和相关性分析等方法, 研究其景观地球化学特征, 旨在通过对克拉玛依人工碳汇林区的景观地球化学特征的研究, 为这一地区盐渍化土壤改良和沙漠化防治提供理论依据。结果表明: 克拉玛依人工碳汇林区土壤Cl^-、SO₄^2-、Ca²⁺在0~80 cm范围内变异系数较大, 80~100 cm范围内, 土壤总盐和各离子变异系数相对较小; 盐分表聚现象严重; 该地区盐土类型主要是硫酸盐型, 其中SO₄^2-和Na⁺+K⁺为土壤可溶性盐的主要成分。研究区地下水呈弱碱性, 除HCO₃^-外, 其他离子和矿化度表现出较强的变异性; 地下水的化学类型主要为Cl·SO₄-Na, 矿化度和Cl^-、SO₄^2-、Na⁺+K⁺相关系数较为显著。种植人工碳汇林后, 除土壤HCO₃^-含量有轻微上升外, 其他离子均有所下降, 其中SO₄^2-含量的降低趋势最为明显。俄罗斯杨林分土壤含盐量随种植年限的增长明显降低, 种植后的土壤盐渍化状况有明显改善。     

甘蔗酒精废液对土壤理化性状及氧化还原酶的影响

在蔗地上设计不施肥(CK1)、施化肥(CK2)和4个直接喷施甘蔗酒精废液处理,研究不同用量废液施用对土壤理化性状及两种氧化还原酶活性的影响.结果表明:蔗地施用废液提高了土壤全氮、Cl-、有机质、腐殖质含量,使甘蔗苗期土壤过氧化氢酶和多酚氧化酶活性异常升高,随后迅速下降,成熟期下降到接近或小于CK2的土壤酶活性水平.甘蔗苗期土壤过氧化氢酶活性与全氮、有机质、腐殖质呈极显著正相关,与富里酸、胡敏酸、Cl-呈显著正相关(r0.05=0.811,r0.01=0.917,n=6);土壤多酚氧化酶活性与有机质、腐殖质、Cl-呈显著正相关.与不种植甘蔗的75 tCK废液处理相比,种植甘蔗的75 t废液处理甘蔗生长后期土壤全氮、有机质、Cl-含量和多酚氧化酶活性较低.说明与施用化肥或不施肥处理相比,蔗地施用废液有提高土壤肥力和有机质、腐殖质含量的作用,但也使施用初期过氧化氢酶和多酚氧化酶活性异常升高,施废液的土壤种植甘蔗对废液养分吸收和环境净化有一定作用.     

Comparison of the Chemical Composition of Precipitation on the Western and Eastern Coasts of Korea

Precipitation samples were collected at two coastal sites on the Korean Peninsula, Kangwha on the western coast and Yangyang on the eastern coast, from September 1991 to February 1997. The samples were analyzed for concentrations of major ions, in addition to pH and electrical conductivity. The annual volume-weighted mean pH values were 4.89 and 5.05 at Kangwha and Yangyang, respectively. The pH was generally lower at Kangwha than that at Yangyang, especially during the winter, because of reduced neutralizing inputs and greater acid inputs in winter. Dominant ions were different with NH₄ ⁺ and SO₄ ^2- most important at Kangwha and Na⁺ and Cl^- at Yangyang. Neglecting sea salt components, nss-SO₄ ^2- and NO₃ ^- were important anions and nss-Ca²⁺ and NH₄ ⁺ were important cations at both sites. Concentrations of these ions were 1.2–1.6 times higher at Kangwha than at Yangyang. Annual mean concentrations of these ions varied little during the study, while larger seasonal variations were observed. Annual mean nss-SO₄ ^2-/NO₃ ^- ratios at Kangwha and Yangyang were 2.8 and 2.6. The 5 yr annual mean values of nss-SO₄ ^2-/NO₃ ^- showed no trend at Kangwha but a decreasing tendency at Yangyang. The decreasing trend is similar to the decreasing trend in emissions of SO₂/NO_x in South Korea. Regional differences in chemical composition between Kangwha and Yangyang appear to be associated with long-range transport of acidic gases and alkaline dust originated from other regions.     

Factors controlling the removal of sulfate and acidity from the waters of an acidified lake

Although Lake Anna, an impoundment in Central Virginia, receives acid mine drainage (AMD) from Contrary Creek, the effects of the AMD pollution on the lake are less severe than expected. Previous work at Lake Anna has shown that bacterial sulfate reduction in the lake sediments plays an important role in the recovery of the lake from the AMD inputs. Sulfate removal rates were measured in sediment microcosms under a variety of experimental conditions to determine the factors controlling the rate of sulfate and acidity removal from the lake water. Sulfate removal rates were not significantly different over the short term (3 weeks) in summer sediment microcosms incubated at 6 vs 26 °C. Winter sediment microcosms showed no significant sulfate removal during the 18 day experiment when incubated at either 6 or 28 °C. Thus there is a strong seasonal temperature effect in Lake Anna sediments but no significant short term effect. Simulated AMD, with and without Fe, was added to sediment microcosms collected from an unpolluted part of the lake. The microcosms with Fe had significantly higher rates of sulfate removal indicating that Fe plays an important role in transporting sulfate to the sediment and/or in preventing oxidation of the reduced sulfide. After 27 days, from 54 to 96% of the added sulfate in the simulated AMD was recovered as FeS or S⁰ in the top 4 cm of sediment. In a separate experiment, ³⁵S-SO _inf4 ^sup2? was found to attach to precipitating Fe oxyhydroxides (1.5 to 4.7 mol SO _inf4 ^sup2? mol^?1 Fe precipitate) upon mixing Contrary Creek (AMD) and Lake Anna waters. Results of this study suggest that sulfate removal may be more rapid in metal rich AMD systems thans in metal poor systems characteristic of those which receive acidic deposition.     

采前营养液处理对水培小白菜硝酸盐积累的影响

开展了在采收前减少小白菜营养液中的氮量或在去除硝态氮的基础上加入渗调离子以试图降低小白菜的硝酸盐积累的试验。结果表明,在去除营养液中的硝态氮后,在营养液中加入Cl-、SO42-、苹果酸根离子、山梨酸根离子、乙酸根离子是降低溶液培养小白菜硝酸盐积累的有效措施,但处理后采收的时间不可推迟太久。而只减少营养液中氮肥用量会使产量迅速下降,硝酸盐含量降低却缓慢,加入渗调离子可缓解因去除氮肥引起的小白菜产量的下降。     

新疆伊犁察南灌区土壤盐分特征

以察南灌区土壤为研究对象,对不同含盐量土壤进行盐化程度分级,并对该地区土壤盐分特征进行相关分析和主成分分析,以及对土壤盐分因子区域影响因素进行探讨。结果表明:察南灌区以碱性土壤为主,HCO_3~–是影响该灌区土壤p H最强的因子;对灌区0~100 cm土体土壤的分析表明,灌区盐化土面积约为总灌溉面积的1/4,盐渍化风险较大;相关性分析显示,HCO–3、Cl~–、SO_4~(2-)、Ca~(2~+)、Mg~(2~+)、Na~+、K~+为盐分主要组成离子,总盐分与各离子之间均呈正相关关系,与总盐分相关性最强的阴离子为SO_4~(2-),相关性最强的阳离子为Mg~(2~+);主成分分析显示,HCO_3~–、Cl~–、K~+为影响该灌区土壤盐分特征的主导因子;通过盐分因子区域影响因素定性分析可知,除HCO_3~–和pH是由河流以及地下水综合作用影响外,其他盐分因子均主要受河流影响。     

休耕和种植作物对黑麻土壤肥力的影响

为了明确不同茬口土壤养分的固持残留水平,建立高效合理的轮作顺序以解决连作再植障碍问题。2018年在甘肃定西渭源县莲峰镇绽坡村随机区组设计、“S”形取样休耕1季、种植1季春小麦、马铃薯、蒙古黄芪和当归后0-20 cm层次的黑麻土壤,测定土壤全量、速效养分和阴阳离子含量。结果表明:休耕1季和种植1季蒙古黄芪增加了0-20 cm层次土壤的有机质、全氮、速效磷、速效钾、阴阳离子、Mg^2+、SO4^2-和Cl^-含量,种植1季当归降低了0-20 cm层次土壤的有机质、全氮、速效磷、速效钾、阴阳离子、Mg^2+、SO4^2-和Cl^-含量。方差分析显示,休耕1季和种植1季蒙古黄芪后0-20 cm层次黑麻土壤的有机质、全氮、速效磷、速效钾、阴阳离子、Mg^2+、SO4^2-和Cl^-含量显著高于种植1季当归。主成分回归分析发现,休耕1季和种植1季蒙古黄芪后0-20 cm层次黑麻土壤肥力综合指数为0.98和0.56,种植1季当归的综合指数得分仅为0.07。休耕1季是黑麻土壤用养结合的简便有效方法,种植1季蒙古黄芪是培肥黑麻土壤肥力的适宜作物。