Sampling strategies in the assessment of long‐term exposures to toxic substances in air

The decision to mitigate exposures from vapor intrusion (VI) is typically based on limited data from 24‐hour air samples. It is well documented that these data do not accurately represent long‐term average exposures linked to adverse health effects. Limited decision guidance is currently available to determine the most appropriate sampling strategy, considering the cost of sampling alternatives along with the economic consequences of exposure‐related health effects. We present a decision model that introduces economic and statistical considerations in evaluating alternative VI sampling methods. The model characterizes the best sampling method by factoring economic and health consequences of exposure, the variability of exposure, the cost of sampling and mitigation, and the likelihood of false‐negatives and false‐positives. Decision‐makers can use results to select the sample size that maximizes net benefit. Conceptual and mathematical models are presented linking biological, statistical, and economic considerations to assess the cost and effectiveness of different sampling strategies. The model relates an average exposure concentration, determined statistically, to abatement costs and to the monetary value of health deterioration. The value of the information provided by different strategies is calculated and used to select the optimum sampling method. Simulations show that longer‐term sampling methods tend to be more accurate and cost‐effective than short‐term samples. The ideal sampling strategy shows significant seasonal variation (it is typically optimal to use longer samples in the winter) and also varies significantly with the stringency of regulatory standards. Longer‐term sample collection provides a more accurate representation of average VI exposure and reduces the likelihood of type I and type II errors. This reduces expected costs of mitigation and exposure (e.g., health consequences, legal and regulatory penalties), which in some cases can be quite significant. The model herein shows how these savings are balanced against the additional costs of longer‐term sampling.     

Correction to: Opportunities to reduce nutrient inputs to the Baltic Sea by improving manure use efficiency in agriculture

While progress has been made in reducing external nutrient inputs to the Baltic Sea, further actions are needed to meet the goals of the Baltic Sea Action Plan (BSAP), especially for the Baltic Proper, Gulf of Finland, and Gulf of Riga sub-basins. We used the net anthropogenic nitrogen and phosphorus inputs (NANI and NAPI, respectively) nutrient accounting approach to construct three scenarios of reduced NANI-NAPI. Reductions assumed that manure nutrients were redistributed from areas with intense animal production to areas that focus on crop production and would otherwise import synthetic and mineral fertilizers. We also used the Simple as Necessary Baltic Long Term Large Scale (SANBALTS) model to compare eutrophication conditions for the scenarios to current and BSAP-target conditions. The scenarios suggest that reducing NANI-NAPI by redistributing manure nutrients, together with improving agronomic practices, could meet 54–82% of the N reductions targets (28–43 kt N reduction) and 38–64% P reduction targets (4–6.6 kt P reduction), depending on scenario. SANBALTS output showed that even partial fulfillment of nutrient reduction targets could have ameliorating effects on eutrophication conditions. Meeting BSAP targets will require addressing additional sources, such as sewage. A common approach to apportioning sources to external nutrients loads could enable further assessment of the feasibility of eutrophication management targets.

     

Ambient air monitoring of PCDD/Fs and co-PCBs in Gyeonggi-do, Korea

We started the monitoring for PCDD/Fs in ambient air and soil in August 2001, and co-PCBs in January 2002. Decreasing of PCDD/Fs and co-PCBs levels in ambient air were observed. The higher PCDD/Fs levels were found in winter and lower in autumn. We found that the industrial incinerators influenced the PCDD/Fs levels in ambient air. In the 2,3,7,8-substituted PCDD/Fs concentration profiles, the three major congeners occupied 67% of the total mass. In case of co-PCBs, PCB#118, #105 and #77 were observed as the main congeners. Five cluster groups discriminated by ratio of four components, O(8)CDD, 1,2,3,4,6,7,8-H(7)CDD, 1,2,3,4,6,7,8-H(7)CDF and O(8)CDF, were obtained from HCA (hierarchical cluster analysis).     

南宁城市大气污染对人体健康的危害及治理对策

南宁市大气属煤烟型污染 ,大气的主要污染物为SO2 、NOx、TSP、降尘 ,虽然随着环境管理和污染治理工作的加强 ,污染物浓度逐年下降 ,但是工业区大气污染仍然较重。污染物流行病学调查显示 :工业区癌症和呼吸系统疾病死亡率均高于全市平均水平 2倍左右 ,城区又高于郊区 2倍 ,大气污染综合指数与呼吸内科门诊就诊人数呈正相关。用邓聚龙的灰色系统理论分析得知污染物对癌症和呼吸系统疾病死亡率有关联 ,关联度从大到小排序为 :TSP >降尘 >SO2 >NOx ,最后提出了大气污染治理的对策。     

Single-source impact analysis using three-dimensional air quality models

Isolating the effects of an individual emissions source on secondary air pollutants such as ozone and some components of particulate matter must incorporate complex nonlinear processes, be sensitive to small emissions perturbations, and account for impacts that may occur hundreds of kilometers away. The ability to evaluate these impacts is becoming increasingly important for efficient air quality management. Here, as part of a recent compliance enforcement action for a violation of the Clean Air Act and as an evaluation of ozone response to single-source emissions plumes, two three-dimensional regional photochemical air quality models are used to assess the impact on ozone from approximately 2000 to 3000 excess t/month of nitrogen oxides emitted from a single power plant in Ohio. Periods in May, July, and August are evaluated. Two sensitivity methods are applied: the "brute-force" (B-F) method and the decoupled direct method (DDM). Using DDM, maximum 1-hr averaged ozone concentrations are found to increase by up to 1.8, 1.3, and 2.2 ppbv during May, July, and August episodes, respectively, and concentration increases greater than 0.5 ppbv occur in Ohio, Pennsylvania, Maryland, New York, West Virginia, Virginia, and North and South Carolina. B-F results for the August episode show a maximum 1-hr averaged ozone concentration increase of 2.3 ppbv. Significant localized decreases are also simulated, with a maximum of 3.6 ppbv in Ohio during the August episode and decreases of 0.50 ppbv and greater in Ohio, Pennsylvania, Maryland, West Virginia, and Virginia. Maximum increases are compared with maximum decreases for the August period using second-order DDM and are found, in aggregate, to be greater in magnitude by 42%. When evaluated during hours when ozone concentrations exceed 0.060 ppm, the maximum increases in ozone are higher than decreases by 82%. The spatial extent of ozone increase in both cases is about triple that of reduction.     

岗南水库沉积物间隙水有色溶解有机物的时空分布特征及差异分析

有色可溶性有机物(CDOM)作为溶解性有机物的重要组分,影响着水体中污染物质的形态特征和迁移转化过程.本研究运用紫外-可见光谱技术(UV-vis)以及三维荧光光谱(EEMs)技术结合平行因子分析法(PARAFAC),对岗南水库自入库河口到坝前主库区四季演变过程中沉积物间隙水CDOM的分布、光谱特征以及来源进行解析.结果表明,岗南水库沉积物间隙水CDOM的相对浓度a_(254)、a_(260)、a_(280)和a_(355)存在显著的季节差异,并且相对浓度大小为夏季春季秋季冬季;沉积物间隙水CDOM的E2/E3、E3/E4、E4/E6以及S_R存在显著的季节差异,呈现冬季高夏季低的特征;秋冬季的E2/E3以及E3/E4明显高于春夏季,并且秋冬季的E3/E4大部分均大于3.5,表明秋冬季沉积物间隙水CDOM具有更小的分子量和更低的腐殖化程度;三维荧光光谱通过PARAFAC解析出3种组分,分别为类酪氨酸(C1)、短波类富里酸(C2)和降解的腐殖类物质(C3),并且3种荧光组分间具有显著的正相关性(P0.001);岗南水库沉积物间隙水的CDOM总荧光强度和各荧光组分荧光强度呈现显著的季节差异,总荧光强度以及各组分的荧光强度呈现春季的最高、秋冬季次之、夏季最低的分布特征;秋冬季各个荧光组分占比不存在显著差异,春夏季各个荧光组分占比不存在显著差异,秋冬季与春夏季各个荧光组分占比存在显著差异;秋冬季沉积物间隙水CDOM生物源指数(BIX)和荧光指数(FI)均高于春夏季,表明秋冬季CDOM的自生源强于春夏季,与腐殖程度指标(HIX)的结果相吻合;PCA结合Adonis分析显示沉积物间隙水CDOM的光谱特征呈现显著的季节差异(P0.001);并且组分C1、C2、C3以及水质参数[氨氮、硝氮、亚硝氮、溶解性总氮以及溶解性总磷]均有很好的线性回归方程.综上,通过对岗南水库沉积物间隙水CDOM光谱特征进行研究,可以为分析岗南水库有机物污染特征和水质管理提供技术支持.     

转换电极的电动力强化植物修复高浓度砷污染土壤

电极转换下,以Capsicum annuum L.为对象探讨电动力强化的植物修复高浓度砷污染土壤效果。结果表明:对照组土壤pH降低,实验组升高。对照组土壤中砷浓度从（524.1±5.6） mg/kg降低为（500.5±8.3） mg/kg,实验组不同区域土壤砷浓度分别为（179.8±10.6）,（674.9±5.43）,（512.8±7.3） mg/kg。相较于对照组,实验组植物对砷的吸收量分别增加了-18.1%、282.8%和170.3%。对照组、实验组区域1、2、3的土壤和根际土壤砷浓度之比分别为2.62、0.64、1.48和1.26,电场增高了植物根系附近的砷浓度。对照组、实验组区域1、2、3土壤第5天的残渣态砷占比为55.64%、34.99%、39.06%和0%;对照组、实验组第5天阴极和第10天阴极附近土壤,结晶水铁铝氧化物结合态和残渣态砷占比为67.45%、0%和8.88%;体现了电场对土壤重金属形态的活化作用。实验组修复10 d的电耗成本为79.5元/m3,具备一定经济优势。     

组配改良剂联合硅肥对Cd污染稻田的修复效果

选取湖南省浏阳市某Cd污染稻田进行田间试验,研究组配改良剂石灰石+海泡石（LS）、基施硅肥及叶面喷施硅肥对Cd污染稻田修复效果,结果表明：（1）基施硅肥90kg/hm²和叶面喷施硅肥（0.2,0.4g/L）对土壤pH值无明显影响,添加LS（2250,4500kg/hm²）的各处理均显著提高土壤pH值（P < 0.05）.（2）基施硅肥90kg/hm²分别降低土壤交换态、毒性特征浸出（TCLP）提取态Cd含量20.0%和18.5%,叶面喷施硅肥对土壤Cd两种提取态含量无明显影响,添加LS的各处理（2250,4500kg/hm²）分别使土壤交换态、TCLP提取态Cd含量降低25.8%~49.9%、26.4%~44.5%.（3）3种单一技术措施均能明显降低水稻各部位Cd含量,但降低糙米中Cd含量的效果低于3种技术措施的组合处理;“组配改良剂LS+基施硅肥+叶面喷施硅肥”各处理（JL1F1、JL1F2、JL2F1、JL2F2）使水稻糙米中Cd含量降低25.6%~70.5%.（4）“组配改良剂LS+基施硅肥+叶面喷施硅肥”的组合技术处理能显著降低土壤中Cd的有效性,显著降低水稻各部位中Cd含量,其中JL2F2处理效果最佳,能使对照糙米Cd含量从0.66mg/kg降低到0.19mg/kg,实现中重度Cd污染稻田的水稻安全生产.     

土壤调理剂对土壤-水稻系统Cd、Zn迁移累积的影响及健康风险评价

选取湖南省长沙市北山镇某中重度Cd污染稻田,研究了土壤调理剂(石灰石+偏高岭土+钙镁磷肥)对稻田土壤重金属Cd、Zn的钝化效果,以及对水稻各部位累积Cd和Zn的影响,并进行了Cd的健康风险评价.结果表明,使用土壤调理剂提高了稻田土壤p H值.Cd的CaCl_2提取态含量降低了0.9%~24.1%,Zn的CaCl_2提取态含量降低了22.5%~69.6%.土壤调理剂显著降低了水稻糙米中Cd与Zn的含量,与对照相比分别降低了10.8%~47.3%、10.3%~17.5%;土壤调理剂对水稻糙米Cd的吸收和累积的影响要远大于Zn,水稻糙米中的Cd/Zn比随着土壤调理剂施用量的增加而显著降低.研究区大米重金属Cd目标危害系数THQ值大于1,说明当地人群通过食用大米途径摄入重金属Cd存在健康风险.土壤调理剂有效地抑制了水稻植株对土壤中Cd的吸收,并降低了Cd/Zn比,使糙米中的Cd含量显著降低,从而降低了当地人群通过食用大米途径摄入重金属Cd的健康风险.