环境中磷化氢对水稻根际环境与土壤有效磷的影响研究

以稻田湿地中磷化氢为研究对象,采用室内模拟的方法,考察了不同浓度的磷化氢(0,1.4,4.2,7.0 mg·m-3)对水稻根际与非根际土壤的p H值、氧化还原电位、Fe2+、Mn2+、磷酸酶活性及有效磷的影响.结果表明:磷化氢导致根际土壤p H明显下降,非根际土壤中p H变化不明显.而氧化还原电位(Eh)则不同,磷化氢使水稻根际与非根际土壤的Eh均增大.磷化氢对Fe2+、Mn2+和碱性磷酸酶的影响具有相似性,磷化氢处理的前15 d,根际土壤中的Fe2+、Mn2+和碱性磷酸酶变化不明显,随着水稻的生长,根际土壤中的Fe2+和Mn2+随磷化氢浓度的增大而增加,随暴露时间的增加而减少;而根际土壤中的碱性磷酸酶随磷化氢浓度和暴露时间的增加而增加.非根际土壤中的Fe2+、Mn2+和碱性磷酸酶在磷化氢作用下变化不明显.水稻在磷化氢的环境影响下,根际与非根际土壤的有效磷含量都提高,表明一定浓度的磷化氢对土壤磷表现出活化效应.     

Plant development in the absence of epiphytic microorganisms

Microorganisms (bacteria, fungi) are common residents of the roots, stems and leaves of higher plants. In order to explore the dependency of plant development on the presence of epiphytic microorganisms, the achenes (seeds) of sunflower (Helianthus annuus L.) were sterilized and germinated under aseptic conditions. The sterility of the seedlings was determined with the agar impression method. In seedlings from non-sterile seeds (control) that were likewise raised in a germ-free environment, all plant organs investigated (stem, cotyledons and primary leaves) were contaminated with bacteria. Hypocotyl elongation was not affected by epiphytic microorganisms. However, the growth rates of the cotyledons and primary leaves were higher in sterile seedlings compared with the control. The implications of this differential inhibition of organ development by epiphytic bacteria that are transmitted via the outer surface of the seed coat are discussed. We conclude that epiphytes in the above-ground phytosphere are not necessary for the development of the sunflower seedling.     

Rhizobacteria helps to explain the enhanced efficiency of phytoextraction strengthened by Streptomyces pactum

The ultimate purpose of phytoextraction is not only to remove heavy metals from soil but also to improve soil quality. Here, we evaluated how the joint effect of Streptomyces pactum (strain Act12) and inorganic (Hoagland's solution) and organic (humic acid and peat) nutrients affected the phytoextraction practice of cadmium (Cd) and zinc (Zn) by potherb mustard, and the microbial community composition within rhizosphere was also investigated. The results indicated that the nutrients exerted synergistically with Act12, all increasing the plant biomass and Cd/Zn uptakes. The inoculation of Act12 alone significantly increased dehydrogenase activity of rhizosphere soil (P < 0.05), while urease and alkaline phosphatase activities varied in different dosage of Act12. Combined application of microbial strain with nutrients increased enzymatic activities with the elevated dosage of Act12. 16S ribosomal RNA high-throughput sequencing analysis revealed that Act12 inoculation reduced the diversity of rhizosphere bacteria. The Act12 and nutrients did not change dominant phyla i.e., Proteobacteria, Bacteroidetes, Gemmatimonadetes, Actinobacteria and Acidobacteria, but their relative abundance differed among the treatments with: Peat > Act12 > Humic acid > Hoagland's solution. Comparatively, Sphingomonas replaced Thiobacillus as dominant genus after Act12 application. The increase in the Sphingomonas and Flavisolibacter abundances under Act12 and nutrients treatments gave rise to growth-promoting effect on plant. Our results revealed the important role for rhizosphere microbiota in mediating soil biochemical traits and plant growth, and our approach charted a path toward the development of Act12 combined with soil nutrients to enhance soil quality and phytoextraction efficiency in Cd/Zn-contaminated soils.     

菲、芘污染土壤中丛枝菌根真菌对土壤酶活性的影响

采用温室盆栽试验方法,研究了丛枝菌根真菌(AMF)对菲、芘复合污染土壤中微生物数量和酶活性的影响.结果表明,接种AMF显著增加了三叶草根际和菌丝际土壤中细菌、真菌和放线菌的数量,并对微生物区系有选择性.在供试菲、芘污染浓度范围内,低浓度菲、芘对土壤多酚氧化酶、酸性磷酸酶和过氧化氢酶活性有激活作用;但当菲、芘浓度升高时,3种酶活性受到抑制.与无植物对照土壤相比,接种AMF后三叶草菌根际酸性磷酸酶活性降低了2.4%~23.1%,过氧化氢酶活性增加了12.6%~20.3%,除高浓度处理外多酚氧化酶活性均增加;菌丝际多酚氧化酶活性比菌根际低12.9%~62.9%,酸性磷酸酶活性比菌根际高3.3%~24.0%,过氧化氢酶活性则高于菌根际.     

大气O3浓度升高对2种基因型矮菜豆根际微生物的影响

在模拟的大气臭氧浓度升高环境中,用磷脂脂肪酸方法（PLFA）分析大气臭氧浓度升高和接种丛枝菌根（AM）真菌对臭氧敏感性不同的2种基因型矮菜豆（臭氧敏感性：S156;臭氧耐受性：R123）根际和菌丝际微生物量及群落结构的影响,旨在明确大气臭氧浓度变化对植物根际微生物的影响,为全面评价臭氧浓度升高对土壤-植物生态系统的影响...     

菌株Desulfovibrio sp. CMX的DNRA性能和影响因素

微生物的硝酸盐异化还原为铵(DNRA)过程对自然界中铵根离子的存在和转化具有重要影响,然而关于SRB菌株DNRA过程影响和机制尚未探明.本文考察了实验室筛选的SRB菌株Desulfovibrio sp.CMX的DNRA能力、影响因素及其影响机制.结果表明,无外加氮源的情况下,分别以10 mmol·L-1NO_3~-和NO_2~-作为唯一电子受体,菌株Desulfovibrio sp.CMX最终NH_4~+生成率分别达到85.8%和97.3%,且无N2和N2O等副产物产生.实验探究了不同外加氮源、不同初始浓度的SO_4~(2-)、S~(2-)对菌株DNRA过程的影响.酵母浸粉作为外加氮源可促进菌株的生长和代谢从而促进菌株DNRA过程;SO_4~(2-)对于NO_3~-还原为NO_2~-阶段起促进作用,而对NO_2~-还原为NH_4~+阶段起抑制作用,综合两方面影响,最终表现出对菌株DNRA过程的抑制作用;S~(2-)对菌株生长及DNRA过程都表现出抑制作用,且S~(2-)浓度越高抑制作用越强,当S~(2-)浓度达到6 mmol·L-1后,S~(2-)对于NO_3~-还原为NO_2~-阶段的抑制作用强于NO_2~-还原为NH_4~+阶段的抑制作用,NO_3~-还原为NO_2~-速率低于NO_2~-还原为NH_4~+速率,此时体系中不再有NO_2~-的积累.     

藻细胞在固体表面附着特性的初步研究

针对平板式光生物反应器,以补充有碳源的SE(Brostol's solution)培养基作为普通小球藻生长的水环境,研究了载体表面粗糙度、藻细胞接种量、培养液pH值和液体流量对小球藻细胞在固体基质表面吸附特性的影响.结果表明:藻细胞在各载体表面的吸附密度均随时间进行呈现先快速增大再逐渐趋于平缓的变化趋势;在实验条件下,随载体表面粗糙度和藻液中藻细胞接种量增大,载体表面对小球藻细胞的吸附率均增大,吸附密度也增大;当藻液pH值为6左右时,小球藻在载体表面的吸附密度达到最大;液体流量为0.65 mL·min-1时,载体表面对小球藻细胞的吸附能力最强.各参数对藻细胞吸附密度影响的重要程度依次为藻细胞接种量、培养基pH值、液体流量.     

Removal of metals by sorghum plants from contaminated land

The growth of high biomass crops facilitated by optimal of agronomic practices has been considered as an alternative to phytoremediation of soils contaminated by heavy metals. A field trial was carried out to evaluate the phytoextraction efficiency of heavy metals by three varieties of sweet sorghum (Sorghum biocolor L.), a high biomass energy plant. Ethylene diamine tetraacetate (EDTA), ammonium nitrate (NH₄NO₃) and ammonium sulphate ((NH₄)₂SO₄) were tested for their abilities to enhance the removal of heavy metals Pb, Cd, Zn, and Cu by sweet sorghum from a contaminated agricultural soil. Sorghum plants always achieved the greatest removal of Pb by leaves and the greatest removal of Cd, Zn and Cu by stems. There was no significant difference among the Keller, Rio and Mray varieties of sweet sorghums in accumulating heavy metals. EDTA treatment was more efficient than ammonium nitrate and ammonium sulphate in promoting Pb accumulation in sweet sorghum from the contaminated agricultural soil. The application of ammonium nitrate and ammonium sulphate increased the accumulation of both Zn and Cd in roots of sorghum plants. Results from this study suggest that cropping of sorghum plants facilitated by agronomic practices may be a sustainable technique for partial decontamination of heavy metal contaminated soils.     

Alcoholism in cockchafers: orientation of male Melolontha melolontha towards green leaf alcohols

Chemical orientation of the European cockchafer, Melolontha melolontha L., a serious pest in agriculture and horticulture, was investigated by field tests and electrophysiological experiments using plant volatiles. In total, 16 typical plant volatiles were shown to elicit electrophysiological responses in male cockchafers. Funnel trap field bioassays revealed that green leaf alcohols (i.e. (Z)-3-hexen-1-ol, (E)-2-hexen-1-ol and 1-hexanol) attracted males, whereas the corresponding aldehydes and acetates were behaviourally inactive. Furthermore, male cockchafers were attracted by volatiles from mechanically damaged leaves of Fagus sylvatica L., Quercus robur L. and Carpinus betulus L. However, volatiles emitted by damaged leaves of F. sylvatica attracted significantly more males than those from the other host plants. Odour from intact F. sylvatica leaves was not attractive to M. melolontha males. Females were not attracted by any of the tested volatile sources. The results suggest that plant volatiles play a similar role as a sexual kairomone in mate finding of M. melolontha, as has been shown for the forest cockchafer, Melolontha hippocastani F. Nevertheless, both species show remarkable differences in their reaction to green leaf alcohols.     

丛枝菌根真菌在矿区生态环境修复中应用及其作用效果

针对煤矿区生态环境修复中存在的主要问题,研究丛枝菌根真菌与紫穗槐共生状况,丛枝菌根真菌对紫穗槐根系发育的影响及其对煤炭开采塌陷区退化土壤的改良效应.结果表明,接种菌根5个月后,接种丛枝菌根促进紫穗槐地上部分和根系生长,提高了紫穗槐根系侵染率;接种区紫穗槐根际土壤中球囊霉素、易提取球囊霉素含量显著增加;接种菌根提高了紫穗槐根际土壤有效磷和有机质含量,微生物数量明显提高,取得较好的菌根生态效应.接种菌根有利于对矿区根际土壤的改良,促进了矿区生态系统稳定,对维持矿区生态系统的持续性具有重要意义.     

增氧模式对水稻根际微生物多样性和群落结构的影响

为探讨不同增氧模式对水稻根际土壤微生物数量和群落结构的影响特征,以密阳46（MY）和珍汕97B （ZS）为材料,设置干湿交替（AWD）、长淹充氧（CFA）和长淹（CF）这3种根际氧处理模式,采用Illumina MiSeq高通量测序技术结合土壤理化性质,分析不同氧环境下水稻根际土壤细菌和真菌群落多样性特征及其与土壤理化因子的关系.结果表明,水稻根际土壤中细菌优势菌群为绿弯菌门（Chloroflexi）、放线菌门（Actinobacteriota）、酸杆菌门（Acidobacteriota）、变形菌门（Proteobacteria）和厚壁菌门（Firmicutes）;真菌优势菌群为子囊菌门（Ascomycota）和担子菌门（Basidiomycota）.不同增氧模式下水稻根际土壤微生物群落组成存在明显差异.各生育期,Chloroflexi和Acidobacteriota在AWD处理时,Actinobacteriota在CFA处理时的相对丰度高于其他处理;Firmicutes在AWD处理下相对丰度低于其他处理.增氧影响根际微生物物种多样性和丰富度.如AWD处理显著增加细菌物种多样性,降低其丰富度;AWD和CFA处理后真菌物种多样性和丰富度均显著增加.土壤理化性质也受增氧模式的影响.不同处理土壤氧化还原电位（Eh）大小表现为：AWD>CFA>CF,处理间差异达显著水平;与CF处理相比,增氧处理（AWD和CFA）显著增加根际土壤NO₃^--N含量,降低NH₄⁺-N含量.相关性分析表明,根际土壤pH和Eh与细菌物种多样性正相关,与丰富度负相关;与真菌物种多样性和丰富度正相关.冗余分析发现,全生育期的Chloroflexi相对丰度与pH和NH₄⁺-N均呈正相关;分蘖期和齐穗期的Chloroflexi相对丰度与Eh和NO₃^--N呈正相关,成熟期则负相关.pH和Eh与Acidobacteriota、Proteobacteria和Basidiomycota相对丰度正相关,与Firmicutes和Ascomycota相对丰度负相关.Ascomycota相对丰度与NO₃^--N负相关,与NH₄⁺-N正相关,Basidiomycota与之相反.综上,增氧模式改善根际土壤氧环境,改变土壤理化性质,影响微生物群落多样性和丰富度,从而优化微生物群落结构.     

旱地作物根际和非根际土壤硝酸盐异化还原成铵细菌群落组成的研究

为研究典型旱地农田土壤硝酸盐异化还原成铵过程(Dissimilatory nitrate reduction to ammonium,DNRA)的群落组成,针对DNRA过程的功能基因nrfA进行高通量测序.根际和非根际、4种典型农作物共16个样品,质控后每个样品得到87000条序列,在相似度≥90%下划分到27952个OTUs,选取其中丰度较高的258个代表OTUs进行生态学分析.多样性分析(OTUs水平)结果表明:3/4的作物根际土壤样品中的DNRA群落丰富度、物种多样性和物种均匀度高于相应非根际样品,对比4种作物,粟作物根部土壤DNRA群落多样性最高,玉米作物非根际土壤最低.对代表OTUs进行分类,共定义到6个门(Phylum),19个属(Genus).其中相对丰度最高的3个属为Hyalangium(29.31%)、Chthoniobacter(20.33%)和Nitrospira(13.41%),表明三者在群落组成中占主导地位.结合土壤理化因子分析,DNRA群落相对丰度与NO~-_2-N、TN、含水率、TOM、pH及温度呈显著相关关系.本研究在一定程度上揭示了旱地农田土壤DNRA细菌的群落组成、多样性及与土壤环境因子的关系,为提高氮肥的利用效率和减小环境污染提供理论依据.     

土壤中残留毒死蜱的作物效应

应用盆栽实验和室内分析方法,研究了红壤中残留毒死蜱农药对小麦、油菜苗生长及其对农药吸收的影响.结果表明,红壤中残留毒死蜱初始浓度为1～10μg/g,20d后,小麦苗地上部吸收的浓度可达0.257～4.50μg/g,油菜苗地上部吸收浓度可达到0.249～2.02μg/g;红壤中残留毒死蜱浓度低于10μg/g,对小麦苗地上部鲜重没有显著影响,低于5μg/g,对油菜苗地上部鲜重没有显著影响;残留毒死蜱在油菜苗根际的降解比非根际快1.4～4.2倍;油菜苗根际土细菌、真菌数量分别是非根际土的3.18倍、1.84倍,而放线菌数量差异不大;根际土比非根际土pH值低约0.19～0.23.     

增施CO2对C3和C4植物根际氯氰菊酯残留浓度的影响

CO2减排和土壤污染修复是我国实现经济和环境可持续发展必须解决的两大难题.基于生物固碳对根际微环境的影响,本研究提出通过增施CO2强化土壤有机污染的植物修复过程,为同时解决CO2减排和土壤污染植物修复面临的困境提供新思路.在模拟的CO2增施环境中,以C3植物菜豆和C4植物玉米为供试植物,以氯氰菊酯为目标污染物,研究增施CO2对C3和C4植物根际氯氰菊酯残留浓度的影响.结果表明,增施CO2可显著增加C3植物菜豆的地上和地下干重,在氯氰菊酯添加浓度为0、20、40 mg.kg-1时地下干重分别比自然CO2水平时增加了54.3%、31.9%和30.0%.增施CO2提高了未添加氯氰菊酯土壤的菜豆根际微生物数量,但降低了添加氯氰菊酯土壤的菜豆根际微生物数量.增施CO2对未添加氯氰菊酯土壤的菜豆根际氯氰菊酯残留浓度没有显著影响,但降低了菜豆根际氯氰菊酯的残留浓度,分别比自然CO2水平时下降24.0%（20mg.kg-1）和16.9%（40 mg.kg-1）.然而,对C4植物玉米而言,增施CO2对植物生物量、根际微生物、根际氯氰菊酯残留浓度下降没有明显促进作用,甚至有抑制作用.本实验表明,增施CO2降低了C3植物根际氯氰菊酯残留浓度,可以考虑将增施CO2作为C3植物修复土壤污染的强化措施,但对C4植物的影响还有待进一步研究.     

太湖地区农田土壤中铵态氮和硝态氮的时空变异

对太湖地区农田土壤3种主要水稻土类型:白土、黄泥土和乌栅土在小麦和水稻生长期间土壤剖面中NH₄⁺-N和NO₃^--N含量的时空变异进行了研究.结果表明:NH₄⁺-N在1a中的2月份和9月含量较高;4月份和11月的含量较低.NH₄⁺-N在土壤剖面中的空间变异为土壤上层到土壤下层呈逐渐递减趋势,以表土层含量为最高,在40cm以下基本上趋于稳定.NO₃^--N的含量低于NH₄⁺-N,在1a中小麦生长季节(旱作)高于水稻生长季节(水作);NO₃^--N在土壤剖面中的空间变异为:旱作时的土壤表层到底层迅速下降;但在水稻生长季节土壤剖面中表层土壤的NO₃^--N含量低于底层的NO₃^--N的含量,出现明显的淋溶现象.在旱作期间NO₃^--N随NH₄⁺-N呈指数曲线变化,而在水稻生长期间没有这种关系.NH₄⁺-N和NO₃^--N含量与土壤有机质呈显著的直线线性正相关关系.但NH₄⁺-N和NO₃^--N仅在旱作时随土壤粘粒含量和土壤pH值的升高而呈对数曲线下降.     

肠杆菌FM-1强化积雪草修复镉污染土壤机理

分析了肠杆菌FM-1的耐镉性及促生特性，并研究了肠杆菌FM-1对矿山型和非矿山型积雪草镉富集及根际土壤pH值的影响.结果表明，肠杆菌FM-1对镉有较强的耐受性，其分泌的吲哚乙酸含量，铁载体A/A_r值和溶磷能力分别达到（72.85±0.62）mg/L，0.21±0.01和（143.33±2.13）mg/L，表明肠杆菌FM-1具有良好的促生能力.将肠杆菌FM-1接种于采自广西柳州泗顶铅锌矿周边4种类型的土壤中，均不同程度提高了矿山型和非矿山型积雪草对镉的富集.其中，下游区土壤接种肠杆菌FM-1后，矿山型积雪草茎和叶中镉含量分别增加了87.90%~161.84%和21.85%~76.42%，非矿山型叶片中的镉含量增加了5.84%~35.20%.研究表明肠杆菌FM-1促进了积雪草对镉的富集.同时，肠杆菌FM-1的添加在一定程度上影响了积雪草根际土壤的pH值，显著降低了下游区矿山型积雪草根际土壤中的pH值.     

Molecular phylogeny of cycads inferred from rbcL sequences

The chloroplast gene rbcL was sequenced to elucidate the evolution of the gymnosperm plant order Cycadales. In accordance with traditional systematics, the order Cycadales and the corresponding genera cluster as monophyletic clades. Among them, the genus Cycas forms a basal group. The genetic distances within the genus Encephalartos and between the sister groups Encephalartos, Lepidozamia and Macrozamia, are unexpectedly small, suggesting that the extant species are the result of Miocene and Pliocene speciation. Their distribution in Africa or Australia, respectively, may therefore rather be due to long-distance dispersal than to Cretaceous continental drift, as had previously been assumed. The rbcL sequences also indicate that the colonisation of Madagascar by Cycas thouarsii occurred only recently as the sequences of C. thouarsii and Cycas rumphii from Indonesia are identical. In contrast, the divergence of the Cycadaceae and Zamiaceae apparently occurred in the Mesozoic.     

转cry1Ab和epsps基因玉米C0030.3.5对土壤固氮细菌丰度和群落结构的影响

为评估转基因玉米种植对土壤氮周转功能微生物的潜在风险,以转cry1Ab和epsps基因玉米C0030.3.5(TM)及其亲本玉米DBN318(PM)为研究对象,于2015年拔节期、抽雄期、乳熟期、完熟期采集根际土和非根际土进行试验,并采用荧光定量PCR(quantitative real-time PCR,q PCR)和末端限制性片段长度多态性(terminal restriction fragment length polymorphism,TRFLP)技术分析土壤固氮微生物nif H基因丰度和多样性.结果表明,TM和PM根际土和非根际土固氮细菌nif H基因丰度随生长时期整体呈现先升高后降低的变化趋势,无论是根际土还是非根际土,同一生长时期2种玉米nif H基因丰度间差异均不显著.相关分析显示,土壤固氮细菌nif H基因丰度与有机质含量呈极显著正相关.T-RFLP结果表明,所获得的14种TRFs中,43 bp和155 bp片段所代表的固氮细菌为共有优势种群,无论是根际土还是非根际土,同一生长时期各T-RFs的相对丰度在TM和PM间差异同样不显著.土壤固氮细菌的Shannon指数和Evenness指数随生长期整体呈现出先升高后降低的变化趋势,无论是根际土还是非根际土,同一生长时期TM和PM的Shannon指数间及Evenness指数间均无显著差异.主成分分析(principal component analysis,PCA)表明TM和PM土壤固氮细菌群落结构组成无显著差异.冗余分析(redundancy analysis,RDA)显示土壤铵态氮和p H对固氮细菌群落结构组成影响显著.     

基于高通量测序检测Pb污染对三叶草根际土壤细菌多样性的影响

为了研究Pb污染对根际土壤微生物多样性的影响,揭示根际微生物对Pb胁迫的适应性机制,通过盆栽试验模拟轻度[w（Pb）为300 mg/kg]、中度[w（Pb）为600 mg/kg]和重度[w（Pb）为900 mg/kg]Pb污染土壤环境,利用高通量测序技术和生物信息学分析方法,测定了不同w（Pb）处理下三叶草根际土壤中细菌群落的丰度和组成.结果表明:①共检测到37个门,其中变形菌门为优势菌群,占比为50.7%~53.9%,其次为拟杆菌门、酸杆菌门和疣微菌门. ②共检测到623个属,其中鞘氨醇单胞菌属为优势菌属,占比为17.1%~19.4%. ③中度Pb污染土壤样本中细菌的多样性最高,重度Pb污染土壤样本中的细菌数量最少,并且其群落组成与其他处理差异最大.研究显示,重度Pb污染会显著抑制三叶草根际土壤样本中细菌的生长,降低土壤样本中细菌总量及其群落的多样性,但中度Pb污染会提高土壤样本中细菌群落的多样性. Pb污染会改变三叶草根际土壤样本中细菌群落组成和丰度,不同类型细菌对Pb污染土壤的适应性不同.根际土壤样本中Gp1菌群的丰度随着土壤w（Pb）的增加而增加,说明Gp1菌群可能是具有Pb污染抗性的优势菌群.      

The composition of bulk precipitation on a coastal island with agriculture compared to an urban region

Results of chemical analyses of monthly bulk samples from Schiermonnikoog, one of the islands in the northern part of The Netherlands, are interpreted. The continuous record covers a period of more than 15 years. A comparison (10 years) is made with Ouderkerk, a village near Amsterdam. Non-sea salt contributions, relations between ion species, long-time trends, annual cycles and meteorological influence are discussed.The study reveals enhanced levels of ammonium in the Schiermonnikoog samples with respect to Ouderkerk. Also, concentrations of sulfate and nitrate were higher. The high concentrations of ammonium are ascribed to dry-deposited NH₃ caused by cattle breeding, the only economical activity on the island. A significant positive trend reflects its intensifying nature. Annual cycles and statistical computations indicate prior combination of parts of ammonium and excess sulfate as ammonium sulfate. The nitrate content appears to be strongly related to ammonium (r = 079). In the Ouderkerk dataset this correspondence is much weaker (0.37), whereas its pH values are systematically lower. It is therefore believed that on Schiermonnikoog concentrations of nitrate are increased by nitrification of ammonium in the collector.Annual cycles of sodium, magnesium and chloride, and to a lesser extent potassium, are very similar (maximum concentrations in November, December and January, and a relative maximum in April). The other annual patterns peak in the first half of the year: maximum concentrations are found in February (ammonium, excess sulfate), June (nitrate), January (potassium) and in April (excess calcium). A combination of frequently occurring offshore winds and low precipitation amounts will account for this behavior.