Cyhalofop‐p‐butyl mobility and distribution of residues in soil at various depths

This study was conducted to evaluate cyhalofop‐p‐butyl mobility in a sandy loam soil and subsequent distribution of residues at various depths under field conditions. Soil samples were taken from 0 to 150 cm depths at 3–90 d after rains in lysemeter of 1 and 2 m depths. Cyhalofop‐p‐butyl application at two rates and subsequent precipitation had a significant impact on soil, physico‐chemical properties and herbicide mobility. Precipitation caused substantial mobility of cyhalofop‐p‐butyl in the soil and 1.1–7.6 μg L^?1 of cyhalofop‐p‐butyl was found in leachates. Cyhalofop‐p‐butyl residues in the leachates were probably due to preferential flow through the soil. Cyhalofop‐p‐butyl residues were detected in significant amounts from the soil up to 10 d, later, residues were found below the detection limit but its three transformation products viz., cyhalofop acid, diacid, and phenol were detected.     

Solubility products of six metal‐glyphosate complexes in water and forestry soils,and their influence on glyphosate toxicity to plants

Abstract

The solubility products (K_sp) of 1:1 complexes of glyphosate, [N‐(phosphonomethyl)glycine], with Mg²⁺, Ca²⁺, Mn²⁺, Zn²⁺, Cu²⁺ and Fe³⁺, were determined in buffered (pH 7.0) distilled water, moist Ottawa sand, sandy loam and clay loam soils, each adjusted to 0.02 M with respect to KNO₃. The K_sp values decreased in the order of Mg ? Ca > Mn > Zn > Cu > Fe, regardless of the medium in which they were determined. The constants measured in Ottawa sand were similar to those in water, but those in the forestry soils depended upon the type of metal ion involved. The values for the Mg, Ca, Mn and Zn complexes were about 2 to 3 times lower in sandy loam soil than those in water, but those in clay loam were about 3 to 10 times lower. The K_sp of the Cu and Fe complexes were similar to those in water regardless of the soil type used.

In a bioassay experiment using tomato plants, immersed in the saturated solutions of the complexes or planted in the sand and soils containing saturated solutions of the complexes, no mortality occurred although slight inhibition in growth was observed in all cases. The most soluble complexes of Mg and Ca caused the most reduction in plant height, while the least soluble complex of Fe caused little growth inhibition. The Zn, Cu and Mn complexes caused some growth inhibition depending on their K_sp values. The larger the solubility product, the greater the concentration of glyphosate ion in solution, and the greater the growth inhibition. In a similar experiment using white spruce seedlings, growth inhibition was insignificant over the 12‐d bioassay period.     

鄱阳湖沙山植物叶片与土壤C∶N、C∶P沿沙化梯度分布特征

在鄱阳湖多宝沙山沿沙化梯度测定了17种常见植物叶片及土壤有机碳(C)、全氮(N)、全磷(P)含量,以阐明沙山常见植物种与土壤C〖DK〗∶N、C〖DK〗∶P分布特征及对沙化的响应,为沙山植被恢复提供基础数据。结果表明：（1）植物叶片C〖DK〗∶N、C〖DK〗∶P分布范围为185～1273、1698～5071,平均值分别为431、3418;土壤0～10、10～30、30～50 cm层C〖DK〗∶N变化范围分别为98～463、24～465和37～450; 相应土层C〖DK〗∶P范围分别为198～759、30～905和47～765。（2）植物C〖DK〗∶N、C〖DK〗∶P对沙化的响应模式一致,均表现出在重度沙化区数值最小;土壤C〖DK〗∶N随沙化程度增加表现出降低趋势,而C〖DK〗∶P则表现出增加趋势,二者对沙化的响应不一致。（3）植物C〖DK〗∶N、C〖DK〗∶P变化主要取决于叶片的N、P含量;土壤C〖DK〗∶N的变化受控于土壤N含量;C〖DK〗∶P变化则决定于土壤有机C含量     

饱和砂质土壤中不同流速条件下1, 2-二氯乙烷的运移及模拟

采用室内土柱试验方法,研究了孔隙水流速对1,2-二氯乙烷(1,2-DCA)在饱和砂质土壤中运移行为的影响.借助CXTFIT模型,通过示踪剂(KBr)穿透试验,获取了土柱内部条件参数,包括弥散系数D和孔隙水流速v,以及可动水和不可动水的分配比例.应用示踪剂试验获取的参数,分别使用平衡模型和非平衡两点模型对1,2-DCA在不同孔隙水流速下的穿透曲线进行了拟合.结果表明,平衡模型不能很好地模拟本文试验条件下1,2-DCA的运移,而非平衡两点模型拟合精度较高.试验条件下,流速对1,2-DCA运移影响显著.孔隙水流速较高时穿透时间较短,穿透曲线峰值更高.土壤对1,2-DCA的吸附作用是影响穿透特征的主要因素,高流速条件下,吸附作用的影响较小.     

长江上游地区土地沙漠化现状及其驱动力的研究

利用最新的土地沙漠化普查数据 ,分析了长江上游地区土地沙漠化的现状及主要危害 ,阐述了该区土地沙漠化的主要影响因素及其驱动力 ,并提出了其土地沙漠化防治的具体对策与措施。结果表明 ,长江上游地区共有沙漠化土地 60 .98× 10 4hm2 ,集中分布于长江源区 ;土地沙漠化类型包括流动沙 (丘 )地、半固定沙 (丘 )地、固定沙 (丘 )地和裸露沙砾地四种 ,其中裸露沙砾地是其主体 ;区内重度、中度与轻度沙漠化土地所占比例分别为 11.5 3 %、5 8.94 %和 2 9.5 3 % ,中度居多 ,沙漠化程度总体偏重 ;土地沙漠化主要造成草地退化、导致冻土退化、影响人类社会经济活动 ,并危及全流域及周边地区的生态环境保护与建设 ;该区土地沙漠化的发生与发展是自然因素与过程、人为因素与过程共同作用的结果 ,其中自然因素是其首要影响因素 ,气候变化是其主要驱动力     

不同干扰强度对沙质海岸带植物物种β多样性的影响

选择东山岛沙质海岸带4种不同干扰强度林分作为空间演替系列,采用样方法研究其β多样性的变化,结果表明：（1）不同干扰强度林分的植物组成和重要值差别较大,在天然次生林的乔木层和灌木层中,潺槁木姜子（Litsea glutinosa）均是第一优势种,重要值分别为98和137,群落结构稳定;择伐干扰群落中,潺槁木姜子变为乔木层第三优势种,重要值为33,灌木层中仍为第一优势种,重要值为128;皆伐干扰群落中其优势地位逐渐降低,乔木层已无潺槁木姜子的分布,群落结构简单、稳定性差;（2）β多样性（CJ、CS、βWS、βC、βR、CN、CMH）测度表明,随着干扰强度的增大,群落间物种更替速率由低到高呈现增大趋势,物种变化较大,共有种逐渐减少;研究结果支持了＂初始植物区系＂学说,为选择合适树种构建稳定高效的沿海防护林体系提供了基础资料。     

盐池柳杨堡人工封育区植被特征研究

封育措施是一种主要的草场恢复和重建的措施。在宁夏自治区盐池县人工封育区采用样方调查法对不同封育年限和不同封育措施下封育区植被的群落结构和生物量进行调查分析。结果表明：封育可以提高生物多样性,使群落的组成趋于稳定。但是长期封育并不利于植被恢复,边缘区和外围区分别在封育后的第五年和第四年生物多样性指数达到最大,边缘区的丰富度指数（R1）和综合多样性指数D、H分别为22、2.26、6.18,外围区的分别达到13、1.67、3.24,然后逐年减小。在不同封育措施下,生物多样性指数核心区最大,说明封育是有效的植被恢复措施。植被盖度和生物量都是外围区最大,说明对草场进行适当的利用是有利于植被恢复的。带状翻耕对植被的恢复作用并不明显,建议进行适当的放牧或刈割。     

沙土中有机挥发物及无机物的测定研究

采用吹扫捕集-气质联用、顶空进样-气质联用、X射线荧光光谱法和二乙基二硫代氨基甲酸银分光光度法4种方法测定沙土中所含有的挥发性有机物以及无机物,检测出沙土中含有2-乙基己醇等5种有机挥发物和砷一种有害的无机物,对比了4种分析方法的效果。     

Spatial and temporal variation of nitrogen exported by runo from sandy agricultural soils

The eutrophication problem has drawn attention to nutrient leaching from agricultural soils, and an understanding of spatial and temporal variability is needed to develop decision-making tools. Thus, eleven sites were selected to monitor, over a two-year period, spatial and temporal variation of runoff discharge and various forms of N in surface runoff in sandy agricultural soils. Factors influencing the variation of runoff discharge and various forms of N in surface runoff were analyzed. Variation of annual rainfall was small among 11 sites, especially between 2001 and 2002. However, variation of annual discharge was significant among the sites. The results suggest that rainfall patterns and land use had significant effect on discharge. The concentrations of total N, total kjeldahl N （TKN）, organic matter-associated N （OM-N）, NO3- -N, and NHn＋-N in the runoff ranged widely from 0.25 to 54.1, 0.15 to 20.3, 0.00 to 14.6, 0.00 to 45.3, and 0.00 to 19.7 mg/L, respectively. Spatial and temporal variations in the N concentration and runoff discharge were noted among the different sites. Annual loads of N in the runoff varied widely among monitoring sites and depend mainly on runoff discharge. High loads of total N, OM-N, NO3--N, and NHn＋-N in the runoff either in citrus groves or on vegetable farms occurred from June to October for each year, which coincided with the rainy season in the region. This study found that N in surface runoff was related to rainfall intensity, soil N level, and fertilizer use.     

城市污泥和粉煤灰配施影响砂化土壤微生物区系的实验研究

目前,对利用城市污泥和粉煤灰改良土壤的研究大多集中在二者对土壤理化特性、作物产量以及重金属累积的影响等方面,而对土壤微生物区系进行研究的相对较少。为了了解城市污泥和粉煤灰改良砂化土壤对土壤微生物区系的影响,文章对包头试验田改良前后土壤微生物区系进行了比较,研究发现,刚刚改良后,土壤中微生物数量较对照组明显增加;在改良后的最初2个月内,细菌和放线菌的数量有所减少,真菌数量少量增加;改良后2～5个月内,改良后土壤中微生物数量较对照组增加幅度显著,细菌、放线菌和真菌数量分别增加79.53%～589.76%,46.53%～270%,61.92%～143.59%,且微生物数量增加的幅度随着时间的延长,呈上升的趋势。