秦淮河干流沉积物磷形态沿程分布特征

应用化学连续提取法,分析了秦淮河干流14个表层沉积物样品的磷形态沿程变化特征及其影响因素.结果发现,秦淮河干流由上游至南京市区段,随城市化程度的提高,河流沉积物总磷和各种形态磷沿程增加的趋势十分明显.Ca-P和Fe-P平均含量分别占TP的26.8%和25.7%,是主要的磷形态.易吸附态磷(L-P)在TP中的比例最低,但在城区由于TP的高度富集,其含量均超过15 mg·kg-1.沉积物中的总磷含量在城区河段显著增加,但只有很少部分转化为稳定形态的磷,人口密集区生活污水等各种来源排放的磷仍然深刻影响着城市河流的水环境质量.随城市化程度的提高,秦淮河中下游沉积物样品中钙富集的趋势明显,与之相对应的是沉积物Ca-P含量均超过200 mg·kg-1,相关分析和通径分析结果表明,二者之间存在成因上的联系.钙的富集提高了沉积物的固磷能力,将上覆水体中的磷转化为钙结合态磷.城区河流沉积物中钙含量的升高,对于河流生态系统磷的迁移转化有重要影响.     

亚热带丘陵小流域土壤有效磷空间变异与淋失风险研究

肥料过施导致的土壤磷素累积和淋失是农业面源污染的重要方面.以湖南省长沙县金井镇脱甲河小流域(52 km2)为研究区,采用高密度布点采样、Arc GIS软件和属性相似反距离加权插值法研究了亚热带丘陵小流域表层(0~20 cm)土壤有效磷(Olsen-P)含量(以P计,下同)的空间分布特征与磷素的淋失风险.结果表明,菜地、果园、稻田和茶园土壤Olsen-P平均含量为62.0、16.1、14.4和13.7 mg·kg-1,是林地(平均含量为2.36 mg·kg-1)的5.8~26.3倍.5个土地利用类型土壤Olsen-P含量均具有高等变异水平和中等程度的空间自相关性(块基比C0/(C0+C)=50%),这与区内地形地貌、土壤母质、人工施肥等具有密切关系.根据土壤0.01 mol·L-1Ca Cl2浸提态P和Olsen-P的非线性关系可确定区内红壤和水稻土P的淋失风险临界值分别为69.97和98.40 mg·kg-1,并据此对脱甲河小流域土壤磷素淋失的风险进行了定量评价,结果表明旱地土壤具有明显较高的淋失风险,其中中等以上的比例占36.4%,而稻田土壤仅有0.2%,为中等以上淋失风险.因此,控制旱地(尤其是菜地)磷肥的投入是降低亚热带丘陵小流域土壤P淋失风险和减轻农业面源污染的关键.     

Se-Ca联合膳食干预缓解Cd诱导小鼠肝肾毒性

为探究Se-Ca联合膳食干预对生物Cd中毒的缓解效果,选取88只BALB/c小鼠,随机划分为19组,在相同饲料Cd暴露浓度下(2mg/kg)分别设置低、中、高浓度的Se和Ca单独和联合膳食干预处理,并观察30d后小鼠的生长发育、肝肾功能、氧化应激状态和组织病理变化.结果显示,Se-Ca联合干预可有效缓解Cd蓄积所致小鼠生长发育迟缓现象,且进一步促进小鼠生长;肝肾功能及氧化应激指标测定结果表明,Se-Ca联合干预对Cd暴露下小鼠肝脏AST、GSH、SOD、GSH-Px和肾脏BUN、MDA、SOD的保护效果优于单一元素干预;联合干预仅需较小剂量即可达到单独Se或Ca干预对肝肾病理损伤的最佳缓解效果.Se-Ca联合膳食干预可有效缓解Cd摄入导致的生长发育缓慢和肝肾毒性,且较之单一元素的干预效果更佳.     

铁基硅盐对土壤环境镉砷赋存形态及转化影响

为探明铁基硅盐对土壤镉砷赋存形态影响及各形态间转化规律,采用室内长期淹水培养吸附实验,研究不同比例铁硅材料对土壤离子态镉砷活性影响;筛选适宜铁基硅盐(FS)配比同时添加腐殖酸(FSC)和金属氧化物(FSCa),明确复配处理土壤中镉砷分级形态转化程度.结果显示,铁:硅比值增加10%,土壤pH值平均降低0.35;F₂-S₈处理土壤离子态镉降幅71%;F₁₀-S₀处理土壤离子态砷降低59.9%,离子态镉砷含量与硅酸盐-铁盐施用量互呈反比;处理F₄-S₆和F₆-S₄之间镉、砷钝化率产生交点,约为25%~30%.土壤中镉主要以可溶态为主,占比58%;砷主要以铁铝氧化态和钙结合态为主,占比40%和23%.铁硅比例为5:5或5.5:4.5左右复配能有效将铝结合态砷和铁铝氧化态砷转变为钙结合态砷和残渣态砷,可溶态镉转化为碳酸盐结合态镉以及铁锰氧化态镉,同步降低土壤中镉砷的活性.     

基于贝叶斯的苯并(α)芘PBPK模型优化与健康风险评估应用

应用基于生理的药代动力学(PBPK)模型预测苯并(α)芘(BaP)暴露的人体内部剂量,基于贝叶斯的马尔科夫链蒙特卡洛模拟(MCMC)方法对模型参数进行校准和优化,最后运用已优化的模型对BaP内暴露基准值进行推导.研究发现,基于贝叶斯的MCMC方法对模型后验参数校准后,模型精度明显提高,两个数据集验证结果显示残差平方和分别降低了72%和94%.PBPK模型以BaP和子代谢物3-羟基苯并(α)芘(3-OHBaP)的体内动力学过程为结构基础,模拟BaP体内浓度分布大小为脂肪>肾脏>皮肤>缓慢灌注组织>快速灌注组织>静脉血>肝脏;3-OHBaP体内浓度分布大小为肾脏>快速灌注组织>脂肪>肺>静脉血>缓慢灌注组织>肝脏>皮肤.敏感性分析显示,快速灌注组织-血分配系数对模型输出影响最大,灵敏度系数超过了200%;排泄系数影响最小,只有肾小球过滤率K_BR的灵敏度系数超过了1%.以美国国家环境保护局推荐的参考浓度2.0×10^-6mg/m³为外暴露安全基准值,基于PBPK模型推导了职业暴露的BaP生物监测当量(BE),结果显示BE值为0.405pmol/mol肌酐(尿液3-OHBaP平均浓度),为基于人体内暴露剂量水平进行定量健康风险评估奠定了基础.     

酸性条件下剩余污泥中Ca2＋和Mg2＋溶出对磷回收的影响

为了在酸性条件下实现剩余污泥中磷的高效回收，对pH=3时剩余污泥水解酸化过程中氨氮、正磷酸盐和钙镁离子的溶出现象以及磷回收进行了研究分析。结果表明：当pH=3时，所溶出的氨氮、镁离子和钙离子与磷酸盐的摩尔比均大于1，能满足采用鸟粪石沉淀法或者羟磷灰石沉淀法回收磷的要求；但所溶出的钙镁离子的摩尔比大于1，会对鸟粪石沉淀法回收磷的顺利进行有较大影响；有无外加镁剂对磷回收率影响不大。采用改型后的镁型强酸性阳离子交换树脂进行离子交换可以得到较高纯度的鸟粪石沉淀产品，通过XRD检测其纯度为95％以上。     

餐厨垃圾厌氧消化中硬脂酸钙的形成及作用

在稳定运行的餐厨垃圾单相厌氧消化体系中，出现白色颗粒状物质，且随着负荷的提高，其数量和粒径不断增加。利用能谱技术分析白色颗粒的元素组成，结合傅里叶红外光谱和13C核磁共振技术分析白色颗粒中的官能基团。经过研究分析认为，该白色颗粒的主要成分为长链羧酸钙盐，具体为硬脂酸钙。同时，对其形成过程进行了分析。该物质的形成对餐厨垃圾中油脂的去除提供了新的思路和途径。     

芳香酸稀溶液的络合萃取研究

络合萃取法分离极性有机物稀溶液具有高效性和高选择性。本文利用三辛胺或磷酸三丁酯为络合剂，四氯化碳、三氯甲烷、正辛醇或煤油为稀释剂，实验测定了苯甲酸、邻硝基苯甲酸稀溶液的萃取相平衡分配系数，讨论了影响因素。     

The variability and intrinsic remediation of a BTEX plume in anaerobic sulphate-rich groundwater

Data from long-term groundwater sampling, limited coring, and associated studies are synthesised to assess the variability and intrinsic remediation/natural attenuation of a dissolved hydrocarbon plume in sulphate-rich anaerobic groundwater. Fine vertical scale (0.25- and 0.5-m depth intervals) and horizontal plume-scale (>400 m) characteristics of the plume were mapped over a 5-year period from 1991 to 1996. The plume of dissolved BTEX (benzene, toluene, ethylbenzene, xylene) and other organic compounds originated from leakage of gasoline from a subsurface fuel storage tank. The plume was up to 420 m long, less than 50 m wide and 3 m thick. In the first few years of monitoring, BTEX concentrations near the point of leakage were in approximate equilibrium with non-aqueous phase liquid (NAPL) gasoline. NAPL composition of core material and long-term trends in ratios of BTEX concentrations in groundwater indicated significant depletion (water washing, volatilisation and possibly biodegradation) of benzene from residual NAPL after 1992. Large fluctuations in BTEX concentrations in individual boreholes were shown to be largely attributable to seasonal groundwater flow variations. A combination of temporal and spatial groundwater quality data was required to adequately assess the stationarity of plumes, so as to allow inference of intrinsic remediation. Contoured concentration data for the period 1991 to 1996 indicated that plumes of toluene and o-xylene were, at best, only partially steady state (pseudo-steady state) due to seasonal groundwater flow changes. From this analysis, it was inferred that significant remediation by natural biodegradation was occurring for BTEX component plumes such as toluene and o-xylene, but provided no conclusive evidence of benzene biodegradation. Issues associated with field quantification of intrinsic remediation from groundwater sampling are highlighted. Preferential intrinsic biodegradation of selected organic compounds within the BTEX plume was shown to be occurring, in parallel with sulphate reduction and bicarbonate production. Ratios of average hydrocarbon concentrations to benzene for the period 1991 to 1992 were used to estimate degradation rates (half-lives) at various distances along the plume. The estimates varied with distance, the narrowest range being, for toluene, 110 to 260 days. These estimates were comparable to rates determined previously from an in situ tracer test and from plume-scale modelling.     

Hydrolysis and photolysis of oxytetracycline in aqueous solution

Oxytetracycline ((2Z,4S,4aR,5S,5aR,6S,12aS)-2-(amino-hydroxy-methylidene)-4-dimethylamino-5,6,10,11,12a-pentahydroxy-6-methyl-4,4a,5,5a-tetrahydrotetracene-1,3,12-trione) is a member of tetracycline antibiotics family and is widely administered to farm animals for the purpose of therapeutical treatment and health protection. Increasing attention has been paid to the environmental fate of oxytetracycline and other veterinary antibiotics with the occurrence of these antibiotics in the environment. The hydrolysis and photolysis degradation of oxytetracycline was investigated in this study. Oxytetracycline hydrolysis was found to obey the first-order model and similar rate constant values ranging from 0.094 ± 0.001 to 0.106 ± 0.003 day^{? 1} were obtained at different initial concentration ranging from 10 to 230 μ M. Solution pH and temperature were shown to have remarked effects on oxytetracycline hydrolysis. The hydrolysis in pH neutral solution appeared to be much faster than in both acidic and alkaline solutions. Oxytetracycline half-life decreased from 1.2 × 10² to 0.15 day with the increasing temperature from 4 ± 0.8 to 60 ± 1°C. The presence of Ca^{2 +} made oxytetracycline hydrolytic degradation kinetics deviate from the simple first-order model to the availability-adjusted first-order model and greatly slowed down the hydrolysis. Oxytetracycline photolysis was found to be very fast with a degradation rate constant at 3.61 ± 0.06 day^{? 1}, which is comparable to that of hydrolysis at 60°C. The presence of Ca^{2 +} accelerated oxytetracycline photolysis, implying that oxytetracycline become more vulnerable to sunlight irradiation after chelating with Ca^{2 +}. The photolysis may be the dominant degradation pathway of oxytetracycline in shallow transparent water environment.