Uncertainty assessment of mapping mercury contaminated soils of a rapidly industrializing city in the Yangtze River Delta of China using sequential indicator co-simulation

Accurate characterization of heavy-metal contaminated areas and quantification of the uncertainties inherent in spatial prediction are crucial for risk assessment, soil remediation, and effective management recommendations. Topsoil samples (0–15 cm) (n = 547) were collected from the Zhangjiagang suburbs of China. The sequential indicator co-simulation (SIcS) method was applied for incorporating the soft data derived from soil organic matter (SOM) to simulate Hg concentrations, map Hg contaminated areas, and evaluate the associated uncertainties. High variability of Hg concentrations was observed in the study area. Total Hg concentrations varied from 0.004 to 1.510 mg kg⁻¹ and the coefficient of variation (CV) accounts for 70%. Distribution patterns of Hg were identified as higher Hg concentrations occurred mainly at the southern part of the study area and relatively lower concentrations were found in north. The Hg contaminated areas, identified using the Chinese Environmental Quality Standard for Soils critical values through SIcS, were limited and distributed in the south where the SOM concentration is high, soil pH is low, and paddy soils are the dominant soil types. The spatial correlations between Hg and SOM can be preserved by co-simulation and the realizations generated by SIcS represent the possible spatial patterns of Hg concentrations without a smoothing effect. Once the Hg concentration critical limit is given, SIcS can be used to map Hg contaminated areas and quantitatively assess the uncertainties inherent in the spatial prediction by setting a given critical probability and calculating the joint probability of the obtained areas.     

国内外烟气流速测量标准比较分析

比较了国内外燃煤电厂烟气流速测量技术及相关标准,分析了测量仪器、矩形烟道采样位置及采样点位置和数目等方面的异同,结合我国电厂现场烟气流速测量的实际情况,提出了修改《固定污染源排气中颗粒物测定与气态污染物采样方法》相关内容的建议。     

污染源废气中二噁英监测采样应注意的几个问题

解析废气中二噁英监测采样的现状及不足,针对生活垃圾焚烧炉(炉排炉)、蓄热式焚烧炉(RTO)和危险废物焚烧炉(回转窑)3种不同类型焚烧炉,考察了采样过程中烟道类型、采样时间和采样时间间隔不同对二噁英监测的影响。结果表明,在水平烟道和垂直烟道采样测得二噁英排放浓度水平相当,有垂直烟道时,优先在垂直烟道采样;间隔采样和连续采样二噁英测定结果基本一致,为了便于操作,建议均采用连续采样方式;采样时间上,生活垃圾焚烧炉应保证超过1 h,蓄热式焚烧炉以2 h左右为宜;间歇投料危险废物焚烧炉应尽量满足2 h以上,条件不许可时,可通过增加采样流量缩短采样时间保证采样量,并在危险废物完全燃烧前结束采样工作。     

顶空-气相色谱法测定地表水中6种乙酸酯类化合物

采用顶空-气相色谱法测定地表水中乙酸酯类化合物,并对顶空瓶的加热温度、平衡时间进行优化。优化后,方法在6种乙酸酯类化合物质量浓度0.05~1.00 mg/L范围内线性良好,检出限为4.49~58.5μg/L,RSD为0.61%~2.51%,加标回收率为96.5%~104%,方法便捷、环保、经济,适用于地表水中乙酸酯类的检测。     

固体进样-冷原子吸收法直接测定土壤中总汞

应用固体测汞仪,采用多标准土壤样品(n20)绘制校准曲线法和单一标准土壤样品绘制校准曲线法,分别对土壤中的汞进行测定。结果表明,两者的方法检出限分别为0.30、1.49 ng,平行样(n=6)的相对标准偏差分别为3.6%~4%、5.4%~9.0%,90 d内的重复性精密度为4.1%,对国家土壤标样进行测定,结果与标准值相符。表明与单一标准土壤样品绘制校准曲线法相比,多标准土壤样品绘制标准曲线法具有更好的精密度、更低的检出限,更强的适用性,并且由于校准曲线长期稳定性,有效缩短土壤中汞的检测周期。     

气体污染源中总氟的监测方法研究

通过对玻璃纤维滤筒的预处理,在等速采样情况下达到完全捕捉烟气中的总氟。     

Investigating the Fate and Transport of Escherichia coli in the Charles River,Boston, Using High‐Resolution Observation and Modeling1

Abstract: The processes affecting the fate and transport of Escherichia coli in surface waters were investigated using high‐resolution observation and modeling. The concentration patterns in Boston’s Charles River were observed during four sampling events with a total of 757 samples, including two spatial surveys with two along‐river (1,500 m length) and three across‐river (600 m length) transects at approximately 25‐m intervals, and two temporal surveys at a fixed location (Community Boating) over seven days at hourly intervals. The data reveal significant spatial and temporal structure at scales not resolved by typical monitoring programs. A mechanistic, time‐variable, three‐dimensional coupled hydrodynamic and water quality model was developed using the ECOMSED and RCA modeling frameworks. The computational grid consists of 3,066 grid cells with average length dimension of 25 m. Forcing functions include upstream and downstream boundary conditions, Stony Brook, and Muddy River (major tributaries) combined sewer overflow (CSO) and non‐CSO discharge and wind. The model generally reproduces the observed spatial and temporal patterns. This includes the presence and absence of a plume in the study area under similar loading, but different hydrodynamic conditions caused by operation of the New Charles River Dam (downstream) and wind. The model also correctly predicts an episode of high concentrations at the time‐series station following seven days of no rainfall. The model has an overall root mean square error (RMSE) of 250 CFU/100 ml and an error rate (above or below the USEPA‐recommended single sample criteria value of 235 CFU/100 ml) of 9.4%. At the time series station, the model has an RMSE of 370 CFU/100 ml and an error rate of 15%.     

Assessing the spatial distribution of grassland age in a marginal European landscape

Grassland age is increasingly recognised to be an indicator for present-day biodiversity, e.g. plant species richness, and is also important for other landscape functions. We developed a methodological approach to systematically assess the spatial distribution of grassland age in marginal European landscapes. This approach - applied to the Lahn-Dill Highlands (1270 km(2)), a marginal landscape in Hesse, Germany - comprises three steps: (1) in a two-stage stratification process, we pre-stratified the study area according to recent land-cover patterns and their changes between 1955 and 1995 (stratification I) and classified grassland types by combining data on soil moisture, base-richness, and elevation (stratification II). From 50 grassland types, we randomly selected 1000 representative grassland patches. (2) We determined the age of these patches by means of aerial photograph interpretation of a chronosequence dating back to 1953 and classified each patch with respect to the age classes young (<18 years), mid-aged (18-47 years), and old (>47 years). (3) Based on this information, we calculated grassland type-specific probabilities for grassland patches to belong to the respective age classes. These probabilities were projected to districts by direct extrapolation. An exemplary validation of extrapolation results for two test areas was performed. The results revealed that 49% of the investigated patches were old grassland. The remaining patches were mid-aged (36%) or young grassland (15%). The extrapolation results indicated accordingly a predominance of old grassland at the district scale. Occurrences of mid-aged grassland were concentrated in districts with a pronounced land-cover change, whereas young grassland is apparently evenly distributed across the study area. Validation results suggest that our approach is suitable for a realistic estimation of grassland age in marginal European landscapes. The method may be applied in landscape models of various disciplines that rely on large-scale information on grassland age.     

Use of the modified BCR three-step sequential extraction procedure for the study of trace element dynamics in contaminated soils

The modified BCR three-step sequential extraction procedure was used to examine the temporal dynamics of trace elements in soils contaminated by an accidental spill from an opencast mine in south-west Spain. Soils were mainly contaminated with pyritic sludge and acidic wastewater, whereas some soils were affected only by acidic wastewater. The distributions obtained for both some major (Ca, Fe and Mn) and trace elements (As, Cd, Cu, Pb and Zn) in the sludge and soil samples taken at different times after the accident, 1-3 months and 21 months, were compared. Sequential extractions were useful in identifying different sources of contamination, and in obtaining additional information on the solubility of secondary minerals formed by pyrite oxidation. Thus, the effectiveness of the BCR procedure has proved to be a useful tool for predicting short- and long-term mobility of trace elements, even in complex environmental scenarios.     

Calibration of the Chemcatcher passive sampler for monitoring selected polar and semi-polar pesticides in surface water

Passive sampling is a powerful method for continuous pollution monitoring, but calibration experiments are still needed to generate sampling rates in order to estimate water concentrations for polar compounds. We calibrated the Chemcatcher device with an uncovered SDB-XC Empore disk as receiving phase for 12 polar and semi-polar pesticides in aquatic environments in flow-through tank experiments at two water flow velocities (0.135 m/s and 0.4 m/s). In the 14-day period of exposure the uptake of test substances in the sampler remained linear, and all derived sampling rates R(s) were in the range of 0.1 to 0.5 L/day. By additionally monitoring the release of two preloaded polar pesticides from the SDB-XC disks over time, very high variation in release kinetics was found, which calls into question the applicability of performance reference compounds. Our study expands the applicability of the Chemcatcher for monitoring trace concentrations of pesticides with frequent occurrence in water.