Agricultural pesticide residues of farm runoff in the Okanagan Valley,British Columbia,Canada

The objectives of this study were to determine environmental occurrence and concentrations of selected currently-used-pesticides and some transformation products in agricultural farms in the Okanagan Valley (OKV), and to conduct a simple risk assessment of environmental pesticides levels detected in OKV on non-target aquatic organisms. The OKV is the tree fruit country of the Province of British Columbia where considerable amount of pesticides are applied annually. Water, sediment and soil samples were collected at eleven sites in early June and late September following rainfall events and/or extended periods of irrigation from drainage ditches and/or from small streams. Undisturbed reference sites were also sampled. Study results showed that forty of the eighty chemicals analyzed, including organochlorine, nitrogen-containing and organophosphate pesticides commonly used for OKV crops, were detected in runoff and small stream water samples. Among which, endosulfan-sulfate was the most frequently detected chemical. Also, azinophos-methyl (0.699–25.5 ng/L), diazinon (0.088–214 ng/L) exceeded, and α-, β- endosulfan, endosulfan sulphate approached the guidelines for the protection of aquatic life.     

Simultaneous voltammetric determination of four triazine herbicides in water samples with the aid of chemometrics

A novel differential pulse voltammetry (DPV) method was developed for the simultaneous analysis of herbicides in water. A mixture of four herbicides, atrazine, simazine, propazine and terbuthylazine was analyzed simultaneously and the complex, overlapping DPV voltammograms were resolved by several chemometrics methods such as partial least squares (PLS), principal component regression (PCR) and principal component–artificial networks (PC–ANN). The complex profiles of the voltammograms collected from a synthetic set of samples were best resolved with the use of the PC–ANN method, and the best predictions of the concentrations of the analytes were obtained with the PC-ANN model (%RPE_T = 6.1 and average %Recovery = 99.0). The new method was also used for analysis of real samples, and the obtained results were compared well with those from the GC-MS technique. Such conclusions suggest that the novel method is a viable alternative to the other commonly used methods such as GC, HPLC and GC-MS.     

Evaluating Alternative Strategies for Minimizing Unintended Fitness Consequences of Cultured Individuals on Wild Populations

Artificial propagation strategies often incur selection in captivity that leads to traits that are maladaptive in the wild. For propagation programs focused on production rather than demographic contribution to wild populations, effects on wild populations can occur through unintentional escapement or the need to release individuals into natural environments for part of their life cycle. In this case, 2 alternative management strategies might reduce unintended fitness consequences on natural populations: (1) reduce selection in captivity as much as possible to reduce fitness load (keep them similar), or (2) breed a separate population to reduce captive‐wild interactions as much as possible (make them different). We quantitatively evaluate these 2 strategies with a coupled demographic–genetic model based on Pacific salmon hatcheries that incorporates a variety of relevant processes and dynamics: selection in the hatchery relative to the wild, assortative mating based on the trait under selection, and different life cycle arrangements in terms of hatchery release, density dependence, natural selection, and reproduction. Model results indicate that, if natural selection only occurs between reproduction and captive release, the similar strategy performs better. However, if natural selection occurs between captive release and reproduction, the different and similar strategies present viable alternatives to reducing unintended fitness consequences because of the greater opportunity to purge maladaptive individuals. In this case, the appropriate approach depends on the feasibility of each strategy and the demographic goal (e.g., increasing natural abundance, or ensuring that a high proportion of natural spawners are naturally produced). In addition, the fitness effects of hatchery release are much greater if hatchery release occurs before (vs. after) density‐dependent interactions. Given the logistical challenges to achieving both the similar and different strategies, evaluation of not just the preferred strategy but also the consequences of failing to achieve the desired target is critical. Evaluación de Estrategias Alternativas para Minimizar las Consecuencias No Inesperadas en la Adecuación de Individuos Criados en Cautiverio sobre Poblaciones Silvestres     

Effect of sunlight radiation,rainfall and droplet spectra of sprays on persistence of bacillus thuringiensis deposits after application of dipel® 76af formulation onto conifers

Abstract

The effect of sunlight radiation, rainfall and droplet spectra of sprays on per ‐sistence of a Bacillus thuringiensis subspp. kurstaki (Btk) formulation, DiPel^® 76AF, was examined after application onto spruce [Picea glauca (Moench) Voss] foliage. The investigation consisted of three studies: (i) Study I: a laboratory microcosm study to examine the photostability of DiPel 76AF deposits on foliage after different periods of exposure to two radiation intensities, (ii) Study II: a laboratory microcosm study to examine the rainfastness of foliar deposits after exposure to different amounts of rainfall consisting of two separate droplet spectra, and (iii) Study III: a field microcosm study to investigate the influence of two different droplet spectra of DiPel 76AF sprays on foliar persistence of Btk under natural weathering conditions. In all studies, persistence of Btk was investigated both by bioassay [using spruce budworm (Choristoneura fumiferana Clemens)] and total protein assay.

The findings of Study I indicated that bioactivity of foliar deposits decreased with increasing duration of exposure to radiation, and with increasing radiation intensity. The half‐life (DT₅₀, the exposure period required for 50% of the initial bioactivity to disappear) was 5.1 d for the low intensity, and 3.9 d for the higher intensity. In contrast with the bioassay results, the total protein levels [determined by the bicinchoninic acid (BCA) method] showed no decrease with increasing duration of exposure, or with increasing radiation intensity.

The findings of Study II indicated that bioactivity of foliar deposits decreased with increasing cumulative rainfall. A new term, RF₅₀ [the amount of rain (in mm) required to washoff 50% of the initial deposit], was introduced to understand the relationship between rainfall intensity and reduction in bioactivity. When the same amount of rain was applied in different droplet sizes, the RF₅₀ value was high (5.2 mm) for the small rain droplets, and was low (2.9 mm) for the large rain droplets. Similar to the bioassay results, the total protein concentrations (determined by the BCA method) decreased with increasing amount of rain and with increasing rainfall intensity. The RF₅₀ value (obtained using ng protein /cm²) was 5.4 mm for the small rain droplets, and was 3.4 mm for the large rain droplets.

The field microcosm study indicated that when DiPel 76AF was applied in small droplets (D_v.5 of 65 μm), the persistence of bioactivity was ca 8.0 d, whereas when it was applied in large droplets (D_v.5 of 130 nm) it was ca 11 d. Bioactivity decreased with time after spray, and the DT₅₀ was 1.98 d for the spray of small droplets, and 2.87 d for that of large droplets. Similar to the bioactivity, the total protein concentrations also decreased with time after spray, and the DT₅₀ values for the small and large droplet spectra were 3.45 and 6.07 d respectively.     

渭北旱塬生态用地降水资源化潜力的估算及评价

针对黄土高原地区水资源严重短缺的态势和生态环境建设的需要，以黄土高原典型地区的渭北旱塬为例。对该区各种生态用地降水资源化理论潜力、可实现潜力和现实潜力进行初步估算。并进行相应评价。结果表明：农、林、牧、果业生产结构布局不合理，使得区内各地、市各种降水资源化潜力差异较大；林地、园地、牧草地的自然降水利用率较大：生态用地降水资源化现实潜力开发度与可实现潜力开发度有11．06％差距．现实潜力开发度与理论潜力开发度相比有36．22％潜力尚待开发。证明该区降水资源化潜力较大，但生态环境建设还是受水盗源短缺限制。     

基于ANN耦合遗传算法的爆破方案选择方法

为预防露天矿爆破引起的事故,基于安全和经济方面的考虑,对露天矿爆破方案进行优化选择,提出将人工神经网络(ANN)模型与遗传算法(GA)相耦合,从而进行爆破方案优化。研究露天矿爆破可能引起的2种主要危害形式:超爆和飞石,进而确定超爆深度和飞石距离为爆破方案的被优化目标参数。另一方面,炮眼深、间距、装药深度、阻塞深度、单位炸药消耗量和钻孔率对超爆深度和飞石距离的影响是复杂的、非线性的,因而将其作为爆破方案的影响参数。分别用影响参数和目标参数作为ANN的输入值和输出值加以训练,训练后的ANN数据作为GA的适应度函数进行方案优化。结果表明:可找到符合工程实例数据的爆破方案集合,借助Pareto图,可得到相关参数的值最小(超瀑深度为0.6999m,飞石距离为27.3386m)的最优爆破方案。     

中国的降水量符合正态分布吗?

利用适合性检验方法 ,对中国境内 16 0个测站自 195 1～ 2 0 0 0年 5 0年的逐月降水资料是否符合正态分布进行了检验 ,并在此基础上对该 16 0个测站降水量的统计分布做了区划。研究结果表明 ,对夏季 ,通过显著性检验的测站数最少 ,而对冬季 ,通过显著性检验的测站数最多 ,即中国夏季降水多符合正态分布 ,而冬季降水多符合非正态分布。一方面 ,我国降水量的统计分布具有一定的区域性、其中黄河流域以南和江淮流域 ,东北地区的东部和西北部以及云南的部分地区为基本符合正态分布区 ,其原因是该区域的气候基本属于季风性气候 ;西北、华北和东北西部为严重偏离正态分布区 ,其原因是西北地区的气候基本是大陆性气候 ;其他地区为偏离正态分布区。另一方面 ,我国降水量的统计分布又具有较强的局地性 ,因此 ,在做有关降水量的分析预报时 ,有必要考虑其统计分布特征。     

皆伐作业对林地土壤因子的影响

对福建省永安市元沙林业采育场杉阔混交人工林林地皆伐作业前后土壤理化性质变化进行试验研究.结果表明,皆伐作业使林地土壤许多理化性质发生改变.皆伐导致土壤容重增大0.13 g·cm-3,土壤结构体破坏率提高12.50%,最大持水量下降6.65%,总孔隙度减小3.88%; 同时土壤主要化学性质,如有机质、全N、水解性N、全P、速效P、全K、速效K等普遍降低,它们的含量分别下降8.14 g·kg-1、0.18 g·kg-1、7.20 mg·kg-1、0.38 g·kg-1、39.98 mg·kg-1、6.95 g·kg-1和12.31 mg·kg-1; 此外,对皆伐作业造成土壤理化性质变化的原因进行了分析,并从森林生态采运角度出发,提出减少皆伐作业对林地土壤破坏的技术措施.     

模拟酸雨对不同土层酸度和K+淋失规律的影响

在江西表土施用KCl肥料后,用室内模拟酸雨的土柱实验,研究酸雨对不同土层酸度及K⁺淋失的影响.其结果表明,不同土层淋出液pH值的变化先下降后上升,但起始pH值存在明显差异,pH2.5酸雨在A层和AB层淋溶的中后期又下降;淋出液电导变化有一个峰值,其出现在淋溶的起始阶段,表明土壤中养分迅速向下迁移.K+的淋失与降雨的酸度有关,pH2.5酸雨会加速K⁺在土体内向下迁移,在A层土壤中K⁺的释放可分为2个阶段:快速释放过程和中速释放过程;至于pH4.5酸雨淋溶下,K⁺淋失分为快速释放过程和慢速释放过程.     

红壤模拟铜污染下紫云英根表形态及其组织和细胞结构变化

采用根形态研究、显微镜观察和透射电子显微镜观察,研究了红壤模拟铜污染下紫云英根表形态及其组织、细胞结构变化.结果表明:当污染铜为0～40mg·kg^-1时,紫云英生长发育正常,根形态完好,功能正常.当污染铜水平在50 mg·kg^-1以上时,紫云英根开始出现受害症状:表现在根粗短呈淡褐色,根毛少且短,主根弯曲,并分出较短的叉根;表皮层出现皱缩;细胞壁略呈波浪形,厚薄不均,质膜界线不明显.紫云英地上部分生长发育受影响,产量开始下降.铜污染水平达到200mg·kg^-1时,根腐烂、组织黑色化、细胞壁断裂,胞质严重收缩解离,紫云英死亡,表明供试红壤临界铜污染浓度为50mg·kg^-1,并且紫云英根对土壤铜污染的耐性随生育期延长而增强,根细胞壁是根耐毒的主要部位.