【作者】 张营；

【导师】 李法云；

【作者基本信息】 湖南农业大学 ， 植物营养学， 2013， 博士

【摘要】 融雪剂是高纬度城市冬季除雪化冰、保证交通安全的主要措施之一。近年来,在中国北方地区氯盐型融雪剂除雪以其简便的操作方式、低廉的价格和良好的融雪效果而得到广泛应用。随着化学融雪剂施用量的逐年增加,其对土壤、植被、地表水和地下水和野生动物的生态环境效应受到广泛关注。高浓度的Na+和Cl-会影响土壤结构和渗透性,对土壤微生物和植物形成渗透胁迫。由于城市市区融雪剂施用量大,融雪剂对土壤-植物系统的危害最为直接,因此研究城市土壤环境中可溶性盐离子的积累具有非常重要的意义。然而在城市环境中,城市道路网密度高,不渗透地表面积比例大,使用融雪剂的种类繁多,融雪剂使用后可溶性盐离子的迁移途径复杂,因此对于城市环境探究可溶性盐离子在土壤-植物系统中的积累和淋溶效应更为重要。本研究以辽宁省沈阳市为研究对象,主要采用野外调查、室内模拟与分析测试相结合的方法,对融雪剂在城市环境中的主要污染行为及生态效应展开系统研究。研究结果表明,目前沈阳市使用的典型融雪剂是以NaCl和CaCl2为主要成分的氯盐型融雪剂。采集城市冬季使用融雪剂的交通主要干道残雪、绿化土壤、典型绿化植物、雨水地表径流和环城水系样品,研究结果表明,城市冬季残雪中Na+、Ca2+和C1-离子等主要离子含量远高于对照,并在城市绿化土壤和典型绿化植物油松中具有明显的积累作用。融雪剂的使用也导致了雨水径流中的可溶性盐离子含量的增加,其在环城水系中的积累可能导致对城市水生生态系统造成不利影响。以城市典型绿化树木油松、灌木唐棣和3种冷季型草坪草为研究对象,探讨2种典型融雪剂(1号融雪剂：NaCl质量百分比为45.2%；2号融雪剂：NaCl质量百分比为54.6%)与其种子发芽、生理生态(叶绿素、质膜透性、酶、丙二醛MDA、光合特性等)的剂量-效应关系以及K+、Na+吸收运输和分配的影响,并进一步探究外源K+和SA在缓解融雪剂对油松幼苗生长抑制中的效应关系。研究结果表明,随着融雪剂处理浓度的增加,3种草坪草种子萌发和幼苗生长受到的抑制作用增强,唐棣幼苗根、茎和叶各器官中Na+含量增加,K+含量和K+/Na+比值降低,根茎运输的SK,Na逐渐上升,茎叶运输的SK, Na显著下降,不同器官间Na+含量表现为根>叶>茎。与2号融雪剂相比,1号融雪剂处理下草坪草种子萌发和幼苗生长的抑制作用更小,唐棣幼苗生物量积累、K+/Na+比值和SK, Na相对更高。3种草坪草对融雪剂胁迫的耐受能力大小依次为：黑麦草、早熟禾、白三叶,耐受1临界值分别为6.25-9.61g/L、4.99-6.17g/L和1.97-3.11g/L,极限值分别为12.89-16.85g/L、9.79-12.62g/L和5.71-8.26gL。融雪剂处理选唐棣叶片中的K+/Na+比值高于根茎,说明唐棣具有一定的耐盐性,根系对Na+截留能力强,保持较高茎向叶SK, Na是减轻地上部分离子毒害的关键因素。0.2%浓度融雪剂胁迫下,20mmol/L KNO3和2mmol/L水杨酸SA能明显诱导油松幼苗过氧化物酶POD活性的增强,缓解膜脂过氧化作用,降低丙二醛MDA在叶片中的积累,维持细胞膜的稳定性。虽然外源K+和SA对油松幼苗叶片胞间CO2浓度Ci和气孔导度Gs的缓解作用并不显著,但其可通过提高叶绿素含量促进光合作用的进行,缓解融雪剂胁迫对油松幼苗生长的抑制,分别增加生物量24.9%和63.6%。可见,20mmol/L KNO3和2mmol/L SA处理能有效缓解融雪剂对油松幼苗的伤害。融雪剂对土壤生物化学性质的试验结果表明,随融雪剂处理浓度的增加,土壤微生物量碳、微生物量氮、土壤呼吸、土壤脲酶和过氧化氢酶活性、土壤矿化作用和硝化作用均受到不同程度的抑制,当融雪剂处理浓度高于0.5%时,土壤微生物量碳土壤呼吸、土壤脲酶活性、土壤矿化作用和硝化作用的抑制程度与对照相比差异显著。土壤中微生物量C/N比与融雪剂处理浓度的相关性分析中,土壤中微生物量CN比和融雪剂处理浓度之间呈现极显著的负相关性(r=0.963,P<0.01),试验结果表明随融雪剂浓度的增加,微生物群落中真菌数量显著减少,细菌成为优势群落。微生物量碳与土壤酶、累积矿化量、累积硝化量的显著相关关系表明,融雪剂对土壤微生物量、微生物活性和群落结构变化的影响可能是导致融雪剂抑制土壤的氮转化过程的重要因素。城市土壤环境中Na和Cl离子明显积累,浓度分别达到352-513mg/kg和577-2,353mg/kg, Cd、Pb、Cu和Zn全量的平均含量为3.0mg/kg、49.2mg/kg、72.0mg/kg和167.4mg/kg。通过先淋洗融雪剂处理液后淋洗去离子水的淋洗方式,模拟实际土壤环境中融雪剂的使用和降水冲刷的过程。土柱淋溶实验的研究结果表明,融雪剂处理下土壤对Cd和Zn的释放量达到总量的20.9%和16.2%,淋出液中Cd、Zn与Cl含量的极显著相关性表明,氯化络合物的形成是Cd和Zn迁移的主要方式之一。与Cd、Zn相比,仅有2.34%的Pb被释放,证实了土壤环境中Pb元素的低迁移性。然而,本试验中淋出液中较高浓度的Pb、Cu和Fe、TOC浓度间显著的相关性表明胶体运移是土壤中1Pb和Cu迁移的主要方式,可见土壤中Pb污染达到一定浓度时,融雪剂对Pb胶体迁移的影响不容忽视。融雪剂对棕壤和红壤中重金属迁移行为的短期淋溶实验结果表明,棕壤对Cu和Pb的释放量为20.98mg/kg和1.11mg/kg,占土壤中Cu和Pb全量的11.11%和0.82%,红壤对Cu的释放量为14.42mg/kg和0.87mg/kg,占土壤中的Cu和Pb全量的7.64%和0.64%。棕壤对Cd和Zn的释放量占土壤中Cd和Zn全量的22.19%和17.37%,红壤的释放量为37.48%和33.20%。可见,棕壤对Pb和Cu的释放高于红壤,而对Cd和Zn的释放量远低于红壤。比较传统型融雪剂(NaCl)和替代型融雪剂(KCOOH)对土壤重金属迁移行为影响的异同,结果表明KCOOH对土壤中Cd、Pb、Cu和Zn的释放量均低于NaCl,因此,与传统型融雪剂NaCl相比KCHOO可能是更好的选择,但其对其他金属元素的释放及对其他环境介质的生态效应有待进一步研究。更多还原

【Abstract】 Large quantities of deicing salts are applied in urban areas for clearing the pavement and ensuring the normal traffic flow during the winter seasons in Northeastern China. There have been many recent reports of high salt levels on aquatic systems and terrestrial vegetation. According to the different pathways by which salt ions may move after deicing salts application, studies of salt storage in soils are especially needed in urban environments. Compared to soils in other ecosystems, urban soils are more exposed to human activities. Urban areas are responsible for a large portion of deicing salts use. However, most previous studies of the effects of deicing salts have been on the soils beside remote, rural highways where salt effects are easily attributed to as single source (a road). It is still unclear how well results of rural studies apply to urban areas, where road and sidewalk density is high, total impervious cover is high. The most common deicing material used in Shenyang city, where the largest and oldest heavy industrial base city in China, is the chemical compounds including sodium chloride (NaCl), calcium chloride (CaCl2).In this paper, the possible alternative pathway by which salt ions (K, Ca, Na, Mg, Cl and SO42-) may move to soil, plants and aquatic systems after deicing chemicals applications was investigated. The distribution characteristics of the principal components in the urban environment showed that the high sodium and chloride concentration in roadside snow is extensively higher than thatin roadside snow samples collected far from urban roads. The salt from deicing operation has been observed to accumulate in roadside soil and inhibit the growth of vegetation (Pinus tabulaeformis). There was an obvious increasing of salt ions concentrations in stormwater runoff samples, especially Na and Cl. It is also found that readily soluble salts ions in stormwater runoff peaked at the first storm event after winter.It is evident that the application of deicing salts in cold regions of China every year has had adverse impacts on the aquatic ecology through stormwater runoff.Application of chemical road deicers has a negative impact on roadside vegetation. Every year, plants in cities suffer from direct and indirect effects of salt application for winter road maintenance.The effects of different concentrations of two typical deicing salts on seed germination and growth response of three kinds of cool-season turfgrasses(Poa pratensis cv. Merit, Lolium perenne cv. Green Emerald and Trifolium repens cv. Riverdel) were studied in this paper. The NaCl content of two typical deicing salts was45.2%and54.6%, respectively. The investigation of growth response in the turfgrass seedlings including length of roots and shoots, relative water content, relative conductivity of the plasma membrance, malondialdehyd (MDA) content and peroxidases (POD) activity. The results showed that the inhibition effect of seed germination and growth response in the three kinds of turfgrasses was increased with the increasing deicing salts concentration. Compared with No.1deicing salt, the inhibition effect of No.2deicing salt on seed germination and growth of three cool-season turfgrass species was stronger. The deicing salts tolerance was in the sequence Lolium perenne, Poa pratensis and Trifolium repens. The critical value of those was6.25-9.61g/L,4.99-6.17g/L and1.97-3.11g/L, respectively. The maximum value was12.89-16.85g/L,9.79-12.62g/L and5.71-8.26g/L, respectively. The deicing salts stress mainly inhibited water absorption, disturbed membrane function and induced MDA accumulation via the effect of osmotic and ion toxicity. However, POD enzyme of the three kinds of turfgrass seedlings played a significant role under the deicing salts stress.Pot experiments were performed in soil culture to test the effect of two typical deicing salts on the growth and K+and Na+transportation and distribution of Amelanchier alnifolia seedlings. The results showed that the biomass accumulation of roots, stems and leaves of seedlings was inhibited by the stress of two typical deicing salts. The treatment of0.4%deicing salts decreased the biomass accumulation significantly in comparison with the control seedlings. Compared with the No.2deicing salts, the seedling of Amelanchier alnifolia had the higher biomass accumulation, K+/Na+ratios and higher transportation selectivity of K+to Na+from root to stem and stem to leaves. In conclusion, the inhibition effect of No.2deicing salt was stronger. With the increasing concentration of deicing salts, the Na+content in the roots, stems and leaves of Amelanchier alnifolia increased while the K+content decreased, resulting in a decrease in the K+/Na+ratio. The ability of ion transporting from root to stem was enhanced, while K+to Na+from stem to leaves was decreased significantly under the increasing concentration of deicing salts. It was reported that the application of exogenous K+and salicylic acid (SA) could protect plants against abiotic stress. In this study, pot experiments were performed in soil culture to test the efficacy of two soil additives, potassium nitrate (KNO3) and SA, in alleviating the stress of deicing salts on growth and photosynthetic parameters of Pinus tabulaeformis seedlings. The results showed that the treatment of KNO320mmol/L and SA2mmol/L to0.2%deicing salts had high dry weight and water content. Meanwhile, the MDA content and leakage rates of electrolyte increased once exposure to0.2%deicing salts, and salts exposure also had an inhibitory effect on the activities of the POD. It was also found that the contents of Ci and Gs remained unchanged in leaves of Pinus tabulaeformis seedlings in all alleviation treatments, but the enhancing of chlorophyll contents played a key role in maintaining the leaf photosynthetic rate under the treatment of KNO3and SA. The results indicated that the salt tolerance of Pinus tabulaeformis seedlings was improved by using soil additives of KNO320mmol/L and SA2mmol/L. Exogenous K+and SA showed strong benefits against deicing salts-induced negative symptoms.Of several impacts of road salting on roadside soils, the potential disruption of the nitrogen cycle has been largely ignored. The effects of deicing salts on the activity and community structure of soil microorganisms, ammonification and nitrification in the soils were investigated. The results showed that the inhibition effect of microbial biomass, metabolic quotient, urease enzyme activiy, the content of mineralizable N and nitrate N growth response was increased with the increasing deicing salts concentration. All that indexes were inhibited significantly by the stress of0.5%deicing salts..The declining trend in biomass C/N with increasing salinity may reflect the baeterial dominanee in soil microbial biomass. The positive relationship between microbial biomass and the content of mineralizable N and nitrate N, indicated that the remarkable influence of deicing salts on the activity and community structure of soil microorganisms, and induced the decrease of soil nitrogen mineralization and nitrification in the soils.Widespread use of deicing salts on road in cold regions has been shown to mobilize heavy metals in roadside soils putting ground and surface waters at risk. Examining the accumulation of deicing salts and its short-term effect on metal mobility in urban roadside soils is important for understanding the distribution and movement of heavy metals in the environment of Northern China. The investigation results from41roadside soils not only showed a strong rise in deicing-salt related Na concentration (352-513mg/kg) and Cl concentration (577-2,353mg/kg), but also high Cd (1.2-7.6mg/kg) and Pb (28.7-101.6mg/kg) values. The most serious contaminated roadside soil was leached in columns alternately with de-icing salt solution and de-ionized water to simulate the runoff of deicing salts into roadside soils followed by snowmelt or rainwater. The results showed that an extensive mobilization of Cd (20.90%of the total Cd) occurred in the salt leachate and a high correlation with Cl showed that Cl complexes are important for the mobilization, although the cation exchange cannot be excluded. Conversely, only2.34%of the total amount of Pb was leached confirming the usual hypotheses about the high immobility of Pb in soils. However, the high Pb concentration coincided with peaks in Fe and TOC concentrations and the low proportion of Pb in the>0.45μm phase, implied an extensive mobilization of small-sized colloids.更多还原