几种有机酸对土壤中磷活动性的增强效应

由富营养化导致的地表水和地下水水质的恶化是当今全球关注的主要环境问题之一。富营养化主要是由于磷在地表径流、生活污泥和流向地表水和地下水体的土壤渗滤液中的迁移。近年来随着大量的有机废弃物在土壤中的应用,磷在土壤表层和亚表层中的活动性显著增加[1～3]。这不仅归结     

千岛湖库区农地土壤磷的固定与释放特性的研究

农田土壤中磷的流失与磷的积累及其吸附/释放特性等有关。为了解千岛湖库区土壤中磷素积累对农地土壤磷流失的潜在影响,本文选择了10个代表性土壤,采用等温吸附与室内加磷培养及化学提取等试验,探讨了库区代表性农地土壤对磷的固定和释放特性;同时采样评估了库区内140个农田土壤有效磷积累状况及其磷素释放的潜力。结果表明,千岛湖库区农地土壤最大磷吸附量有较大的差异,在214.5~745.2 mg kg-1之间变化,平均最大磷吸附量:红壤石灰岩土水稻土紫色土。土壤最大磷吸附量主要与粘粒和游离氧化铁含量有关。加磷培养试验表明,水溶性磷水平随土壤磷的积累呈显著的增加,当土壤有效磷(Olsen P)达45 mg kg-1左右时,土壤磷的释放潜力明显增强。对库区代表性农田磷素积累研究表明,约有19.8%的样点土壤有效磷在45 mg kg-1以上,存在一定的磷流失风险。研究建议加强千岛湖库区农田土壤的测土配方施肥工作,减免因农田土壤中磷素的过度积累而增加对水体的污染。     

有关美国爱俄华州耕地磷素流失指标的研究

土壤磷素的过量流失会危害地表水资源。为了评价农田中磷素释放危险的高潜在性,美国学者提出了耕地磷素流失评价指标。反映了以谷类作物为主的种植体系下,考虑了在侵蚀、径流和亚表层排水等3种主要迁移机制下诸来源因子的多个方面,并估计了进入水体生态系统且转化为对其有效的磷量。当侵蚀危险高时,测得颗粒磷的流失大于可溶性磷的流失,且长期过程明显地大于短期过程。这种磷的评价指标有助于交替选择磷素管理和土壤保护措施,以减少农田向地表水资源迁移的磷总量。     

土壤磷向地表径流迁移的提取系数研究

农田土壤磷随降雨径流进入地表水体是水环境富营养化的主要污染源。通过天然降雨径流小区,动态监测溶解态磷在降雨径流-土壤系统中的迁移,研究坡耕地表层土壤水浸提磷(WEP)和降雨径流溶解态磷(DTP)之间的关系。应用SPSS统计软件线性回归土壤WEP和径流DTP关系,拟合方程,y=0.281x-0.179(R=0.943)。方程斜率表示降雨径流溶解态总磷浓度对土壤不稳定磷浓度的提取系数。经最小二乘法线性回归检验,该模型拟合优度较高,整体性显著。土壤磷提取系数方程可实现磷素从农业营养元素向水环境污染因子内涵的转换,为农业非点源污染防治和水环境保护规划提供了一种估算农业非点源磷素污染潜在负荷的简单有效工具。     

施用鸡粪后土壤磷的累积特征

根据不同方式计算鸡粪施用量,进行连续6茬蔬菜施用鸡粪田间试验,研究农田土壤中磷的累积特征。结果表明:土壤中全磷、树脂态磷、碳酸氢钠提取态磷、氢氧化钠提取态磷和稀盐酸提取态磷含量均随着鸡粪用量的提高而显著提高,且含量增幅随着种植茬数的增加而提高,故在生产实践中以作物需磷量配施鸡粪较优,否则由此所引起的土壤盈余磷素流失或淋失对地表水和地下水水质的潜在影响风险较大。     

外源磷在三峡库区典型土壤中的活性演变及形态转化

三峡库区消落带土壤周期性淹水—出露对磷素迁移循环和水体负荷具有重要影响。以三峡库区消落带广泛分布的紫色潮土和灰棕紫泥土为对象,通过室内模拟培养实验,探讨不同饱和度外源磷在两种土壤中的活性变化与形态转化特征。结果表明:(1)外源磷进入土壤后,表征土壤磷活性的有效磷(Olsen-P)含量及磷素释放能力呈指数型衰减,可用指数方程C_t=ae~(-kt)+b拟合,拟合度均在94%左右。(2)外源磷在灰棕紫泥土中较在紫色潮土中能够保持更高的活性,同时也具有更高的渗漏淋失与释放风险。50%Q_m(最大吸附量)是两种土壤Olsen-P与磷素平衡解吸量的突变点,当磷素吸持饱和度≥50%时,土壤磷活性与渗漏淋失风险将明显增大。(3)Olsen-P与磷释放量在p0.01水平上呈显著正相关,两者可用线性方程良好拟合,因此可用Olsen-P含量表征土壤磷素释放潜势。(4)外源磷进入土壤后,主要转化为活性较高的Ca_2-P和Ca_8-P,约占施入量50%~60%;其次是Al-P和Fe-P,约占施入量的30%左右,闭蓄态磷(O-P)和Ca_(10)-P变化不明显。(5)Ca_2-P是决定Olsen-P和磷素解吸能力的主要形态,对两者均起正向直接作用。     

改良剂降低富磷蔬菜地土壤磷和氮流失的作用

为了解不同改良剂对土壤中磷和氮的稳定作用,进行田间试验研究在施用量为2.5t/hm2时氢氧化铝、石灰石粉、石膏、氯化钙和粉煤灰5种改良剂对蔬菜地地表径流中磷和氮浓度的影响。结果表明,改良剂施用可明显降低土壤有效磷和水溶性磷含量,轻微增加土壤中NH4+-N含量,但对土壤中NO3--N影响不大。施用改良剂可显著降低蔬菜地地表径流中总磷、溶解态磷、颗粒态磷和NH4+-N的浓度,增加水溶性有机氮浓度,但对水溶性总氮和NO3--N浓度影响不明显。与对照比较,施用氢氧化铝、石灰石粉、石膏、氯化钙和粉煤灰5种改良剂的地表径流中总磷浓度下降比例平均分别为13.68%,35.54%,38.72%,43.77%和45.02%,溶解态磷浓度下降比例平均分别为16.05%,32.42%,48.75%,55.38%和38.98%;NH4+-N浓度下降比例平均分别为24.21%,37.84%,11.31%,10.08%和55.56%。总体上,施用氯化钙和粉煤灰降低地表径流中磷浓度的效果好于其他改良剂。     

钱塘江附近农田土壤磷的积累及其流失的潜在风险

为探讨钱塘江周边农田土壤磷流失风险,采集了181个代表性农田土壤,分析了土壤藻类可利用磷、植物有效磷(Olsen P)、水溶性磷和磷零吸附时的磷平衡浓度(EPC0)。结果表明,土壤藻类可利用磷在5.89～932.65 mg·kg~(-1)之间,平均为105.30 mg·kg~(-1);植物有效磷在1.00～444.76 mg·kg~(-1)之间,平均为30.57 mg·kg~(-1),达到较高水平;蔬菜地土壤磷素积累明显高于一般农田。土壤水溶性磷含量和EPC0值随土壤中植物有效磷积累而增加,当土壤中植物有效磷超过60 mg·kg~(-1)时,土壤水溶性磷含量迅速增加;土壤中植物有效磷60 mg·kg~(-1)的样品比例达11.60%。土壤EPC0可作为评价土壤磷素向水体释放磷的强度指标,根据土壤EPC0值与植物有效磷之间的线性关系,估算得到的径流中磷达到Ⅰ、Ⅱ、Ⅲ、Ⅳ、Ⅴ类地表水环境质量标准上限值相应的土壤植物有效磷临界值分别为7.9、13.7、20.9、28.2 mg·kg~(-1)和35.4 mg·kg~(-1),研究区大约有35.9%的农田磷积累可能产生的地表径流磷含量在Ⅳ～劣Ⅴ类的范围。研究认为,钱塘江近江地段部分农田土壤中磷素已有明显积累,存在较高的流失风险。建议把植物有效磷为30 mg·kg~(-1)和60 mg·kg~(-1)分别作为这一区域农田磷肥限量施用和禁止施用的参考值。     

上海市都市农业区域地下水磷素非点源污染特征研究

为研究都市农业区域非点源磷污染对地下水的影响,选择上海市南汇区新场镇果园村的地下水为研究对象,并于2009年7月到9月雨季对该区域地下水进行连续监测。研究结果表明:该区域地下水中磷的形态以水溶性有机磷为主,水溶性总磷含量介于0.75～1.97mg/L之间,平均浓度为1.31mg/L,磷酸盐浓度在0.22～0.62mg/L之间,平均浓度为0.42mg/L。水质低于地表水Ⅴ类标准(0.4mg/L),地下水污染水平已严重超标,不宜饮用。地下水中非点源磷的迁移与土地利用类型相关,果园旁地下水中磷素浓度在降雨前后变化明显。同时,降雨时地表径流加剧磷素流失,农田施肥、水体渗漏均会加剧地下水磷素非点源污染。     

蔬菜种植年限对土壤磷素吸附解吸特性的影响

为揭示不同种植年限土壤磷的固定和释放机制,通过土壤磷的等温吸附、解吸试验研究种植年限分别为3～5年、15～20年、25～30年的黄棕壤0～5cm和5～20cm土层磷的吸附、解吸特性。结果表明:土壤磷的等温吸附曲线、吸附量-解吸量曲线分别与Langmuir方程(R2为0.8728～0.8436)、二次函数方程拟合良好(R2为0.9545～0.9970);随蔬菜种植年限延长,表层土壤磷最大吸附量(Qm)、磷最大缓冲容量(MBC)明显降低,而土壤磷吸附饱和度(DPS)和解吸率明显提高;种植年限15～20年、25～30年土壤磷的解吸率明显高于3～5年土壤。对表征土壤磷素吸附、解吸特性的主要因子如MBC及DPS等作相关分析发现,无定形铁铝含量的变化是影响土壤磷吸附解吸特性的主要因素。     

Relationship between Soil Phosphorus Availability and Phosphorus Loss Potential in Runoff and Drainage

Abstract

Elevated soil phosphorus (P) content is common in the central coastal valleys of California, the result of decades of the intensive vegetable production. Undesirably high P concentration in surface water in this region stimulated interest in evaluating techniques to rank the potential for soil P loss to the environment. Phosphorus availability of 25 representative soils from fields in vegetable rotations were evaluated by the following techniques: bicarbonate‐extractable P (P_bc)–calcium chloride, extractable P (P_cc), P extractable by iron‐impregnated paper (P_Fe), P extractable by anion exchange resin (P_ae), and the degree of P saturation (P_sat). A column study was conducted in which these soils were evaluated for soluble P concentration in runoff and leachate from two simulated irrigation events. There were strong correlations among all measures of soil P availability (r=0.66–0.90). Runoff soluble P was most strongly correlated with P_cc, P_ae, and P_bc (r=0.98, 0.93, and 0.91, or 0.98, 0.90, and 0.85 in the first and second irrigation, respectively). The relationship of runoff soluble P to P_bc, P_ae, and P_cc was characterized by a change point; runoff soluble P from soils <50 mg kg^?1 P_bc was minimal, whereas at higher P_bc runoff P reached levels of environmental concern. Leachate soluble P was also correlated with P_cc, P_ae, and P_bc (r=0.84–0.99). Across soils, leachate soluble P averaged 1.4 mg L^?1, compared to 0.11 mg L^?1 for runoff P. We conclude that P_cc, P_ae, and P_bc are useful tests to rank the potential for P loss in irrigation runoff or drainage. Given the relative complexity of the P_ae technique, P_bc and P_cc appear to be the most practical soil tests for this purpose.     

浙北平原不同种植年限蔬菜地土壤氮磷的积累及环境风险评价

长期过量施肥可导致蔬菜地土壤养分大量累积、养分利用效率下降和环境污染风险增加。以浙北平原不同种植年限蔬菜地土壤为研究对象,采用化学测试方法研究了菜地土壤氮和磷的积累及其淋失潜力的变化。结果表明,随着种植年限的增加,蔬菜地土壤全磷、有效磷（Olsen P）和NO3-N呈明显的积累;蔬菜种植年限为〈2、2～5、6～10、11～20、20～30和＆gt;30a的表土全P平均分别为0.66、0.75、1.07、1.49、2.40和2.12g·kg-1,有效P平均分别为13.2、37.8、42.2、70.2、137.9和101.7mg·kg-1,NO3-N平均分别为9.15、13.58、50.18、46.48、73.28和74.20mg·kg-1,同时土壤N和P垂直下移渐趋明显。土壤水溶性磷含量随土壤有效磷（OlsenP）积累的变化存在一个明显的突变点,相对应的土壤OlsenP临界值约为60mg·kg-1。随着种植年限增长,蔬菜地地表径流中氮和磷浓度呈明显增加,利用年限为20～30a的蔬菜地径流中可溶性P和NO3-N浓度分别约为利用年限〈2a蔬菜地的13.12和9.48倍。研究认为,长期超量施肥已导致这一地区蔬菜地土壤养分的过度积累,在蔬菜生产中应重视和提倡平衡施肥,控制土壤氮磷的积累。     

粪肥对不同磷水平土壤磷流失潜力的影响

田间试验结果表明,因施肥方式不同,粪肥施用对不同磷水平土壤磷流失潜力的影响也不相同。在施用的粪肥与表土混合的情况下,粪肥对土壤磷流失的增加量随土壤磷水平的提高而升高。但当粪肥表施不与土壤混合时,情况有所不同。在粪肥表施初期,无论是高磷土壤还是低磷土壤,地表径流中磷浓度都达到较高水平,施肥引起的土壤磷流失的增加量以低磷土壤更为明显。但粪肥表施较长时间后,粪肥对土壤磷流失的增加量也随土壤磷水平的提高而升高。总的来说,控制地表径流磷流失的效果是粪肥与土混施优于表施,流域内粪肥处置应优先施于土壤磷水平较低的土壤中。     

砂质农业土壤养分积累和迁移特点的研究

研究表明，砂质土壤开垦农用后，土壤有机质和保肥性（CEC）明显下降。除大棚蔬菜地外，施用的氮和钾肥不易在土壤中积累，很容易在短时间内沿剖面迁移至地下水，或随地表径流迁移至周围水体。但磷可以活性较高的可提取态形式积累在砂质土壤剖面中，并可逐渐随水进入地下水或迁至地表水，对环境造成危害。长期施用化肥的砂质农地地下水中磷、氮浓度可达到较高的水平。田间观测和模拟淋洗试验表明，砂土中养分极易随水迁移，高浓度的养分流失常发生在施肥后的降雨过程中。因此在砂质土壤上应避免高量施肥，肥料宜少量多次施用，不宜在雨前施用肥料。     

砂质土壤磷素的组成特点与释放规律研究

砂质土壤磷素主要以可提取态形式积累,有很高的释放潜力。该类土壤磷素的释放受土壤pH、土水作用时间和土壤溶液化学组成等的影响。土壤酸化、土壤溶液中Na+浓度的提高及土壤与水的作用时间增加可促进土壤磷素的释放。用淋洗方法和平衡提取等2种方法对土壤磷素的释放评价表明,淋洗方法测得的P量较小,可代表土壤短期内P释放强度;而平衡提取法提取的P数量较大,可代表土壤P长期释放的容量。     

Profile Characteristics and Potential Environmental Effect of Accumulated Phosphorus in Soils ofVegetable Fields in Beijing

Profile characteristics of accumulated P in 10 representative soils of vegetable fields in suburban districts of Beijing were investigated. Bioavailability of the accumulated P and its potential effect on the environment were studied in a greenhouse pot experiment and a soil column experiment. The results showed that the concentration of Olsen-P in the 0～20 cm soil samples of the vegetable fields ranged from 22.1 to 358.0 mg kg-1, which was 2 to 10 times higher than that of the crop fields in the suburbs of Beijing. Most of the excessive phosphorus was accumulated in the topsoils. The longer the soils cultivated with vegetables, the higher the soil total P, Olsen-P and organic matter concentration. Accumulated P in the soils from vegetable fields had higher bioavailability. Application of phosphorus fertilizer could not increase the dry weights of cucumbers, Chinese cabbage, and rape seedlings continuously planted. The soil column study showed high P concentration (＞ 0.6 mg L-1) in the leachates from the columns of the vegetable field soils with high accumulated P, which has a potential effect on the groundwater and natural water quality.     

长期施肥下黄壤旱地磷对水环境的影响及其风险评价

通过对贵州中部黄壤旱坡地进行采样以及采用无界径流小区法收集地表径流样品 ,探讨长期施肥下旱地磷素水平与地表径流磷浓度的变化及其对水环境的影响。结果表明 :长期施肥下黄壤旱地的磷素水平不断提高 ,CaCl2 浸提磷 (溶解态活性磷 )和NaOH浸提磷 (藻类可利用的土壤总磷 )与土壤全磷或有效磷之间存在显著的相关性 ,土壤富磷化的同时 ,旱地磷对水环境影响的潜能明显提高。黄壤旱坡地中CaCl2 浸提磷、Olsen P、NaOH浸提磷、土壤磷吸持指数、土壤磷饱和度与地表径流中颗粒态磷、生物有效性磷和溶解态活性磷之间的相关性均达显著水平 ,以这些参数作为评价指标 ,初步将黄壤旱地磷对水环境的潜在影响程度分为 3个等级     

Soil Sample Depth in Pasture Soils for Environmental Soil Phosphorus Testing

Phosphorus (P) in runoff from agricultural land is a major contributor to eutrophication of surface waters. This study investigated the relationship between dissolved P in surface runoff and soil-test P measured at different sample depths (0–2 and 0–10 cm). Soil at these depths was collected from 136 sites in southeast New South Wales, Australia, under pastoral agriculture, covering a wide range of soil types and land-use intensity, from native pasture to intensive dairying. Bicarbonate-extractable soil P concentrations at these two depths were curvilinearly related over a very wide range of P (r² = 0.91). Small-plot rainfall simulations were conducted at 14 of these locations, for which the relationship between the sampling depths was even closer (r² = 0.95). After dividing the soils into two groups based on parent material (basalt and nonbasalt), linear relationships were found between extractable soil P and runoff dissolved reactive P, with more of the variance being accounted for with the sedimentary soils (r² = 0.89, 0–10 cm; 0.91, 0–2 cm) compared with basalt soils (r² = 0.63; 0–10 cm; 0.57, 0–2 cm). The results suggest that agronomic soil P testing in pastoral soils (typically 0–10 cm depth) is sufficient for estimating the potential for losses of P in runoff and that there is no need to collect shallow soil samples especially for this purpose.     

Adsorption controls mobilization of colloids and leaching of dissolved phosphorus

Loss of phosphorus (P) from agriculture contributes to the eutrophication of surface waters. We have assessed the magnitude and controls of P leaching and the risk of colloid‐facilitated transport of P from sandy soils in Münster. Concentrations of soluble reactive P in drainage water and groundwater were monitored from 0.9 to 35 m depth. Total P concentrations, P saturation, and P sorption isotherms of soil samples were determined. Concentrations of dispersible soil P and colloidal P in drainage water and groundwater were investigated. The concentrations of soluble reactive P in drainage water and groundwater were close to background concentrations (< 20 µg P l^?1). Median concentrations in excess of 100 µg P l^?1 were found down to 5.6 m depth at one of four research sites and in the lower part of the aquifer. Experimentally determined equilibrium concentrations and the degree of P saturation were good predictors of P concentrations of drainage water. Large concentrations of dispersible P were released from soil with large concentrations of oxalate‐extractable P and addition of P induced further dispersion. Colloidal P was transported in a P‐rich subsoil when there was a large flow of water and after nitrate had been flushed from the soil profile and total solute concentrations were small. We conclude that the concentration of soluble reactive P in drainage water is controlled by rapid adsorption in the sandy soils. Subsurface transport of dissolved P contributes substantially to the loss of P from the soils we investigated. Accumulation of P in soils increases the risk of colloid‐facilitated leaching of P.