镉对稻田土壤典型微生物种的胁迫生理毒性

以水稻田土壤中典型的单种微生物为实验材料,采用纯培养方法,从个体水平上全面探讨了重金属镉胁迫对稻田土壤典型微生物的的生长、活性以及生化过程的生理毒性影响。研究表明:不同微生物纯培养对镉胁迫的敏感程度不同,G 较G-对Cd2 更为敏感,表现为世代时间缩短,最高菌浓度下降。固氮菌对Cd2 非常敏感,当Cd2 质量浓度为0.2mg·L-1时即完全抑制菌体增殖。同时,外源镉强烈的抑制作为稻田土壤中功能微生物的厌氧固氮菌及产甲烷细菌的生物活性,各菌种镉胁迫下细菌细胞内可溶性蛋白、还原糖、核酸质量浓度都在低质量浓度镉胁迫时有所增加;随着镉质量浓度的增加,细菌细胞内各种物质的质量浓度开始减小,以减慢细胞代谢速度,增强对镉胁迫的适应力;各种物质的质量浓度变化趋势为可溶性蛋白>还原糖>核酸,R.eutrophaDKC1细胞内含物质量浓度基本保持稳定。结果可在一定程度上说明镉对微生物的毒性效应,且能在早期较灵敏地指示污染的影响,作为稻田土壤环境受到污染胁迫的细胞生化指标具有一定可行性。     

锑和砷对固氮菌的毒性效应及其机制研究

锑作为一种具有毒性和致癌性的类金属,其不合理的开发造成了严重的生态环境污染,尤其是土壤中高浓度锑和砷污染导致了环境中多种营养元素的缺乏。其中,氮素的缺乏严重阻碍了环境的恢复。然而,固氮微生物不仅能为氮素匮乏环境提供稳定的氮素来源,而且其固氮潜能可以作为监测土壤金属污染的敏感指标。为此,该文通过乙炔还原法(ARA)微宇宙培养试验手段,研究了不同价态锑和砷(三价及五价)在不同质量浓度(100、200、500、1 000、2 500、5 000 mg·L^-1)水平下对棕色固氮菌固氮潜能的影响,同时进一步探究了土壤固氮菌群落固氮潜能对土壤中主要锑和砷价态[Sb(Ⅴ)和As(Ⅴ)]的响应机制。结果表明,锑和砷浓度与棕色固氮菌和土壤固氮微生物的固氮潜能均呈显著负相关,验证了以固氮微生物固氮潜能作为生物指示物的可行性。此外,Sb(Ⅴ)对土壤固氮微生物的毒性显著小于As(Ⅴ)。三价锑和砷污染对固氮菌固氮潜能的毒性高于五价[As(Ⅲ)>Sb(Ⅲ)>As(Ⅴ)>Sb(Ⅴ)],这可能是由于Sb(Ⅲ)和As(Ⅲ)对细胞的致裂性强于Sb(Ⅴ)和As(Ⅴ)。相较于Sb(Ⅴ)和As(Ⅴ)对于棕色固氮菌固氮潜能的抑制作用,其对土壤固氮菌群落的固氮潜能的影响相对较弱。这一差异可能是由于土壤复杂的理化性质以及微生物群落和功能多样性而导致的。     

转Bt基因抗虫棉对土壤微生物群落生物多样性的影响

设置非转基因抗虫棉棉田以及分别种植7和10 a转Bt基因抗虫棉的棉田3个处理,于2007--2008年棉花苗期、蕾期、花铃期和吐絮期采样测定了土壤中5个微生物种类的数量,以监测长期种植转Bt基因抗虫棉对土壤微生物群落生物多样性的影响.结果表明,3种类型棉田土壤细菌、真菌、固氮菌、反硝化细菌、亚硝化细菌数量以及微生物多样性指数在整个棉花生长期内变化趋势基本一致,其中,在棉花蕾期各种微生物数量达到高峰.与种植非转基因抗虫棉相比,不同种植年限转Bt基因抗虫棉对土壤细菌、真菌、固氮菌、反硝化细菌、亚硝化细菌数量和微生物多样性指数都无显著影响,但随着采样时间的不同,3种类型棉田土壤各类微生物数量和多样性指数都呈明显季节变化.     

长期不同施肥模式对砂姜黑土可培养微生物数量和酶活性的影响

以砂姜黑土长期定位土壤培肥试验(1981年—)为依托,研究了长期不施肥CK、长期单施化肥NPK、长期单施有机肥M、长期有机肥与化肥配施MNPK(等氮)和HMNPK(高氮)对砂姜黑土可培养微生物数量和酶活性的影响,揭示砂姜黑土微生物数量和酶活性对不同施肥模式的响应机制,以期为改善砂姜黑土肥力和质量提供科学依据和理论支持。结果表明,CK细菌、真菌、放线菌和固氮菌数量明显低于其它施肥处理,灌浆中期M细菌、放线菌和固氮菌数量显著高于NPK,而真菌数量在M与NPK间差异不显著。MNPK和HMNPK细菌、真菌和放线菌数量显著高于NPK和M,其中灌浆中期MNPK比NPK和M分别增加了47.0%、21.1%、32.1%和23.2%、11.7%、20.2%。MNPK与HMNPK细菌、真菌和放线菌数量在灌浆中期差异皆不显著,而固氮菌数量MNPK显著高于HMNPK。灌浆中期M转化酶、脱氢酶、酸性和中性磷酸酶、蛋白酶活性显著高于NPK,分别增加20.9%、22.1%、17.7%、18.4%、10.0%。长期有机肥与化肥配施相对于长期单施有机肥和化肥可以明显提高土壤转化酶、脱氢酶、酸性和中性磷酸酶、蛋白酶活性。HMNPK的脱氢酶活性显著高于MNPK,而转化酶、酸性和中性磷酸酶、蛋白酶活性与MNPK差异不显著。土壤中转化酶、脱氢酶、酸性和中性磷酸酶、蛋白酶活性皆与细菌、真菌、放线菌呈显著正相关关系,与固氮菌正相关不显著。有机肥与化肥配施最利于提高砂姜黑土微生物数量和酶活性,其次为单施有机肥,有机肥与化肥配施下增加施氮量对土壤微生物数量和酶活性提高作用不大,甚至导致固氮菌数量的下降。     

引入养殖鳖对稻田土壤固氮菌的影响

土壤微生物是土壤生态系统的重要组成部分,为了解稻田综合种养殖模式的土壤细菌尤其是功能型菌群的群落结构特征,采用高通量测序技术对稻鳖共作组(R-T)与稻田单作组(R-M)两种种养模式下根系土壤微生物(nif H基因)多样性特征进行比较.结果显示,稻田根系土壤中,属分类级别的固氮菌主要为慢生根瘤菌属(Bradyrhizobium)、地杆菌属(Geobacter)、脱硫弧菌属(Desulfovibrio)、除硫单胞菌属(Desulfuromonas)、嗜盐红螺菌属(Halorhodospira)、固氮菌属(Azotobacter)、脱硫球茎菌属(Desulfobulbus)、甲基单胞菌属(Methylomonas)、固氮螺菌属(Azospirillum)、Pseudacidovorax、Anaeromyxobacter、Sideroxydans共12类.R-T组根系土壤固氮菌的多样性指数高于R-T组,为6.85±0.07.稻田根系土壤固氮菌在不同种养模式间的差异性占23.86%,在不同水稻生长时期的差异性占16.97%.本研究表明,水稻的生长时期与不同种养模式对稻田根系土壤固氮微生物均具有影响,且生长时期对稻田根系土壤固氮微生物的影响更大.     

丁草胺污染对高产水稻土微生物区系的影响

土壤微生物多样性是表征土壤质量最有潜力的指标,与农田生态系统的稳定性和生产力密切相关。云南永胜涛源乡是保持我国水稻小面积超高产纪录的特殊生态区,常年施用丁草胺作为选择性芽前除草剂,因此,了解丁草胺对其土壤微生物物种多样性的影响意义重大。采用平板菌落计数法,研究了模拟条件下不同丁草胺剂量（有效成分质量分数0.15、0.30和1.5 mg·kg^-1）对高产水稻土中好氧细菌（aerobic bacteria）、放线菌（actinobacteria）和真菌（fungi）,以及功能微生物自生固氮菌（nitrogen fixing bacteria）、磷酸盐溶解菌（phosphate solubilizing bacteria）和硅酸盐细菌（silicate dissolving bacteria）数量的影响。结果表明：施药7 d,中、高质量分数（0.30和1.50 mg·kg^-1）丁草胺处理好氧细菌数量比CK分别高出78.6%和153.8%,而后数量逐渐下降,表现出先刺激生长、后抑制活性的作用,低质量分数（0.15 mg·kg^-1）丁草胺对好氧细菌的生长和增殖影响不明显;施药7 d,高质量分数处理放线菌数量超过CK 75.1%,表现出明显的刺激作用;施药15 d,中等质量分数处理放线菌数量比 CK 高出125.0%,丁草胺浓度越高,刺激作用越迅速,低浓度丁草胺对放线菌则主要表现为抑制作用。低浓度丁草胺对真菌的生长和增殖基本没有影响,中等浓度有先抑制后刺激的作用,施药30 d后其真菌数量超过CK 56.9%,高浓度丁草胺则表现为抑制作用,施药7、30和45 d其真菌数量始终显著低于CK;不同浓度处理丁草胺均能刺激自生固氮菌的数量显著增加,施药7 d,低、中、高质量分数处理自生固氮菌数量分别高出CK 237.1%,179.9%和138.1%,刺激作用显著,但随培养时间延长,高浓度开始表现出抑制作用;不同浓度丁草胺均能抑制磷酸盐溶解菌的生长和增殖,低浓度处理抑制作用微弱,中、高浓度处     

4种农药对土壤微生物的影响Ⅱ:氮素矿质化的变化

研究农药,氯氰菊酯、高效氯氰菊酯、多菌灵和丁硫克百威对山西省两种土壤氮素矿质化（ 氨化作用和硝化作用） 的影响．结果表明,添加低浓度（ ｗ ＝ １００ ｍｇ／ｋｇ） 的４ 种农药,对土壤氮素矿质化无显著影响． 高浓度（ ｗ ＝ １０００ ｍｇ／ｋｇ） 的菊酯类农药会抑制土壤中硝化细菌的活动,使土壤中氨的含量明显积累;添加高浓度多菌灵的土壤样品出现硝态氮积累的现象,这可能与其对微生物生长影响有关;添加高浓度丁硫克百威在一种土壤样品中使氨的含量有明显积累,但在另一种土壤样品中与对照基本相同．可见,农药对土壤氮素矿质化及微生物活性的影响,因农药品种的不同和浓度的不同而异,不同的土壤因微生物活性的差异而对农药污染的反应也不同     

南海北部海域底泥微生物的腐殖质还原性能研究

微生物的腐殖质还原过程自1996年发现以来,日益成为环境领域的一个研究热点。以南海北部海域的8个底泥为实验材料,利用蒽醌-2,6,-双磺酸（AQDS）为腐殖质模式物,初步探讨了南海北部8个底泥培养物对腐殖质的还原能力,并探讨了驯化后的8个底泥微生物对腐殖质的还原过程。结果发现：从南海北部深海海域到海陆交接的香港米浦红树林的8个底泥样品培养液均能很好的还原AQDS;驯化后的8个站点底泥微生物对腐殖质还原的能力有所不同,在48 h,E425站点培养液中的OD450只有0.74,其余7个站点培养液中的OD450都在2.0~3.0之间,推测其原因是8个站点中腐殖质还原微生物的数量具有明显差异,使得各站点的OD450差异很大。研究结果为认知腐殖质还原微生物的分布和探究腐殖质还原微生物在环境中的生态学意义提供重要的理论依据。     

等温微量热技术在土壤微生物学研究中的应用

土壤微生物代谢活性与土壤功能直接相关,是评价土壤质量的灵敏的、普适的综合指标.物质的理化或生物变化过程都伴随着热效应,等温微量热技术可精确测定和跟踪此过程,其研究领域广范并带动土壤微生物的代谢热力学研究蓬勃发展.本文首先简要介绍微量热技术、普遍采用的底物诱导法揭示的微生物代谢活性和国内外研究团队.然后重点综述微量热技术在土壤微生物学的主要研究成果,包括代谢热力学可量化微生物对土壤有机碳的同化效率;土壤微生物在短时间内达到最大热释放值,伴随高的生长速率,表明其代谢活性高;代谢热熵(单位微生物热释放值)可指示微生物对土壤有机碳的转化和利用效率,是指示土壤质量的良好指标;外源污染物总体上抑制土壤微生物代谢活性;检测过程中应重视微量热测定的影响因素与条件优化.讨论测定过程中微生物生长条件的标准化和底物问题.最后展望潜在的研究方向,微量热技术与各种技术的有机结合,有望在土壤微生物结构与活性的地理属性、气候变化、土壤质量的空间大尺度比较和外源污染物的生物毒性评价等方面发挥其重要作用.     

VA菌根真菌对玉米生长及根际土壤微生态环境的影响

用两种不同的VA菌根真菌Glomus mosseae和Glomuscaledonium接种玉米进行盆栽试验。结果表明，两种菌株均能侵染玉米，促进玉米生长．其中以Glomus caledonium的侵染率和作用较为明显。接种后，根区土壤中的细菌、放线菌、固氮菌的数量和微生物生物量明显增加，但真菌的数量则稍有下降。此外．菌根的形成也改善了根区土壤的微生态环境，为下一造作物的生长积累了养分基础。     

Biosynthesis of wax esters in oceanic crustaceans

Slices from the hepatopancreas of various oceanic curstaceans incorporated radioactivity into wax esters from ¹⁴C glucose and ¹⁴C aspartic acid to a lesser extent and from ¹⁴C palmitic acid to a much greater extent. Radioactivity was incorporated from ¹⁴C palmitic acid into both fatty acid and fatty alcohol moieties of wax esters, the percentage of total radioactivity present in alcohol moieties being greater in deep-living than in shallow-living species. Cell-free preparations from the hepatopancreas but not from muscle, supplemented with ATP and reduced pyridine nucleotides, incorporated radioactivity from 1-¹⁴C palmitoyl Coenzyme A into both fatty alcohol and fatty acid moieties of wax esters. Incorporation into fatty alcohol was NADPH- rather than NADH-specific. Preparations from deep-living species had a greater percentage of total radioactivity in the fatty alcohol moieties of wax esters than preparations from shallow-living species. We conclude that the level of wax esters in a given species is correlated with the rate at which the species biosynthesises these lipids de novo; deep-living species have higher rates of wax ester biosynthesis and higher levels of wax esters than shallow-living species. The results support the thesis that wax esters in oceanic crustaceans are derived largely from the animals' internal biosynthetic activities, presumably in response to particular biochemical and/or physiological requirements, rather than from their diets.     

Role of esters in egg removal behaviour in honeybee (Apis mellifera) colonies

In queen-right honeybee colonies workers detect and eat the vast majority of worker-laid eggs, a behaviour known as worker policing. However, if a colony becomes permanently queen-less then up to 25% of the worker population develops their ovaries and lay eggs, which are normally reared into a final batch of males. Ovary development in workers is accompanied by changes in the chemical secretion of the Dufour's gland with the production of queen-like esters. We show that ester production increases with the period that the colony is queen-less. The increased ester production also corresponds to an increase in persistence of worker-laid eggs in queen-right colonies, since the esters somehow mask the eggs true identity. However, in a rare queen-less colony phenotype, workers always eat eggs indiscriminately. We found that the egg-laying workers in these colonies were unusual in that they were unable to produce esters. This apparently maladaptive egg eating behaviour is also seen in queen-less colonies prior to the appearance of egg-laying workers, a period when esters are also absent. However, the indiscriminate egg eating behaviour stops with the appearance of ester-producing egg-laying workers. These observations suggest that esters are providing some contextual information, which affects the egg eating behaviour of the workers.     

Biosynthesis of lipds in zooplankton from Saanich Inlet,British Columbia,Canada

Lipid analyses were carried out on various species of zooplankton captured in Saanich Inlet, British Columbia, Canada, during September, 1972. The amphipod Cyphocaris challengeri had the highest level of lipid, consisting mainly of wax esters. The copepod Calanus pacificus had moderate amounts of lipid, with triglyceride as the major neutral lipid. The euphausiid Thysanoessa raschii contained mainly triglyceride in its moderate levels of neutral lipid, while wax esters and, to a lesser extent, triglycerides were present in the very small levels of neutral lipid in the chaetognath Sagitta elegans. The major fatty alcohols in wax esters of both Cyphocaris challengeri and Calanus pacificus were 20:1 and 22:1, although notable differences were found in the major fatty acids. Biosynthetic studies showed that phospholipids were labelled faster than neutral lipids in all species with both (U-¹⁴C) glucose and (1-¹⁴C) palmitic acid as precursors. Only species containing significant amounts of wax esters in their neutral lipids incorporated substantial amounts of radio-activity from (1-¹⁴C) palmitic acid into wax esters in (i) living animals, (ii) preparations containing fragments of tissue, (iii) cell-free systems. All species incorporated added fatty alcohols into wax esters in preparations containing tissue fragments and in cell-free preparations. Both the fatty acid and fatty alcohols of the wax esters of both Calanus pacificus and S. elegans were labelled from (1-¹⁴C) palmitic acid, consistent with de novo biosynthesis of the esters. (1-¹⁴C) hexadecanol was incorporated into wax esters almost entirely in the fatty alcohol moiety. It is concluded that all species examined formed was esters when presented with preformed fatty alcohols, but only those species that had wax esters as a major component of the neutral lipids were capable of de novo biosynthesis of the lipids.     

Importance of wax esters and other lipids in the marine food chain: Phytoplankton and copepods

Wax esters, which function as reserve fuels, account for 25 to 40% of the lipid of the pelagic copepod Calanus helgolandicus (Copepoda, Calanoida). In laboratory experiments with these crustaceans, diatoms (Lauderia borealis, Chaetoceros curvisetus, and Skeletonema costatum) and dinoflagellates (Gymnodinium splendens), which contained no wax esters, were used as food. Changes in the food concentration affected both the amount of lipid and the composition of the wax esters. Since the fatty acids of the triglycerides and wax esters of C. helgolandicus resembled the dietary fatty acid composition, it appeared that copepods incorporated their dietary fatty acids largely unchanged into their wax esters. The polyunsaturated alcohols of the wax esters did not correspond in carbon numbers or degrees of unsaturation to the dietary fatty acids. We postulate two different metabolic pools to explain the origin of these long chain alcohols. The phospholipid fatty acids were not affected by changes in the amount or type of food, probably because of their structural function.     

邻苯二甲酸酯类环境激素降解研究

概括介绍了邻苯二甲酸酯类化合物的理化性质、毒性和致癌作用，以及其对环境生态系统的影响，论述了近年来在邻苯二甲酸酯类化合物的降解方面所取得的进展，重点讨论了邻苯二甲酸酯的光催化降解。     

Characterization of the pro-inflammatory potencies of purified Jatropha phorbol esters by a gene expression-based in vitro bioassay

The oil extracted from Jatropha seeds is an emerging biodiesel feedstock that also contains several pro-inflammatory phorbol esters. These phorbol esters can elicit adverse inflammatory responses through activation of the protein kinase C, as previously described for the prototypical phorbol ester 12-O-tetradecanoylphorbol-13-acetate. We extracted and purified the six phorbol esters identified in Jatropha oil and assessed their pro-inflammatory activities using a recently developed gene expression-based bioassay. Borrowing from an approach used for the assessment of dioxin toxicity, we expressed their pro-inflammatory potencies in relation to the potency of 12-O-tetradecanoylphorbol-13-acetate (in terms of 12-O-tetradecanoylphorbol-13-acetate toxic equivalency factors). The pro-inflammatory potencies of Jatropha phorbol esters were orders of magnitudes below the potency of 12-O-tetradecanoylphorbol-13-acetate. Interestingly, the cytotoxicity of phorbol esters did not appear to be directly related to their pro-inflammatory potencies. Calculations based on phorbol ester potencies and concentrations led to overestimation of the pro-inflammatory activity of Jatropha oil, as measured by the same gene expression-based bioassay. The preliminary results presented here suggest that further work on the described approach may lead to the development of valuable tools and metrics to quantify and predict the pro-inflammatory activities of complex phorbol ester mixtures.     

Studies on the mechanism of biosynthesis of wax esters in Euchaeta norvegica

Preparations of Euchaeta norvegica catalyse the incorporation of (1-¹⁴C) hexadecanol, (9,10-³H₂) oleic acid, (U-¹⁴C) glucose, (U-¹⁴C) alanine and (U-¹⁴C) aspartic acid into wax esters. Both the fatty alcohol and fatty acid moieties of the wax esters are labelled, indicating de novo biosynthesis. A limited interconversion of fatty acid and fatty alcohol has been demonstrated. Incorporation of glucose into wax esters is diminished by prior starving of E. norvegica; it is also reduced in the presence of ecdysterone. Formation of wax esters from glucose is inhibited by increased oxygen tensions, rotenone and dinitrophenol, and is relatively insensitive to decreased oxygen tensions and cyanide. The data are discussed with particular reference to the reasons why wax esters are biosynthesised by calanoids.     

麻疯树种子中佛波酯的提取及对菜青虫的杀虫活性

佛波酯是麻疯树种子中的主要毒性物质之一.麻疯树种子经乙醇浸提、液液萃取和柱层析,获得佛波酯富集物.以TPA为外标,通过高效液相色谱(HPLC)定量分析佛波酯的含量,同时检测其对菜青虫的毒杀和拒食活性.结果显示,富集物中佛波酯含量达到0.817 35 mg mg-1.佛波酯富集物对3龄菜青虫具有显著的毒杀和拒食活性:毒杀活性表现为胃毒作用,胃毒活性具有明显的剂量效应和时间效应,48、72、120 h的佛波酯半致死浓度(LC50)分别为73.86、16.99、5.26μg mL-1;24、48 h的非选择拒食中浓度(AFC50)分别为9.81、5.39μg mL-1.图3表3参24     

Wax-ester metabolism in the orange roughyHoplostethus atlanticus (Beryciformes: Trachichthyidae)

Freshly caught orange roughy (Hoplostethus atlanticus) obtained at the edge of the Chatham Rise, east of the South Island of New Zealand, in June 1988, were used to investigate tissue-specific lipid synthesis and to obtain blood for plasma lipoprotein analysis. Tissue slices prepared from an intraneurocranial fat deposit, pieces of skull (neurocranium), swimbladder and liver were incubated with radioactive acetate, palmitate and oleate, and the labelled lipids extracted and analysed. All four tissues could incorporate acetate label into fatty acids which were themselves incorporated into triacylglycerols and phospholipids although not into wax esters, the most abundant lipid class in these tissues. Exogenous palmitate and oleate were also incorporated into more complex lipids, with the label from oleate (but not palmitate) being found in wax esters as well as triacylglycerols and phospholipids. The distribution of the label in the wax esters showed that some reduction of the fatty acid to fatty alcohol had occurred. The only exception to this pattern was the swimbladder, which incorporated small amounts of palmitate-label into both the fatty acid and fatty alcohol portions of the wax esters. Lipoproteins were isolated from serum by centrifugation. All lipoprotein classes contained phospholipid, cholesterol, triacylglycerol, cholesteryl esters and wax esters. A very low-density lipoprotein class also contained large amounts of unesterified fatty acids, which are possibly artefacts resulting from storage of the samples. Significant quantities of-3 fatty acids were also found in the serum lipids.     

Bestimmung von Phthalsäureestern in Lebensmitteln, Frauenmilch, Hausstaub und Textilien

25 food samples, 5 mother’s milk specimens, 4 dust samples, and 16 textiles were analysed for phthalic acid esters. Phthalic acid esters were detected in all samples, with di (2-ethylhexyl) phthalate (DEHP) and di-n-butyl phthalate (DBP) being the most abundant phthalates. Raw milk samples revealed average concentrations of total phthalate of 0.1 mg/kg. Retail milk did not contain higher loads than raw milk, even storing samples until their “best-before” date did not result in elevated levels. Skimmed milk was less contaminated than whole milk. The higher concentrations of DEHP and total phthalates in cream samples are due to their higher fat content. With concentrations up to 1.54 mg/kg, ground hazelnuts, almonds, and nutmeg in plastic packagings showed relatively high levels. In infant food, only traces of DEHP and DBP could be found while other phthalic acid esters were not detectable. The mother’s milk samples also exhibited only low amounts of approx. 0.1 mg/kg, thus indicating that there is no accumulation of phthalate esters in the human body. Extraordinarily high concentrations were found in dust samples; with the levels ranging from 300 to 5370 mg/kg and DEHP being the major compound. This leads to the conclusion that the air path must play a considerable role in the transfer of phthalic acid esters. As dust contains considerable amounts of textile fibres, textiles were also included in the investigation. The phthalic ester levels in the textile samples ranged from 3.42 to 34.44 mg/kg. Therefore, the high phthalate contaminations of dust cannot be explained by textile fibres.