Temporal variability of groundwater chemistry in shallow and deep aquifers of Araihazar, Bangladesh

Samples were collected every 2-4 weeks from a set of 37 monitoring wells over a period of 2-3 years in Araihazar, Bangladesh, to evaluate the temporal variability of groundwater composition for As and other constituents. The monitoring wells are grouped in 6 nests and span the 5-91 m depth range. Concentrations of As, Ca, Fe, K, Mg, Mn, Na, P, and S were measured by high-resolution ICPMS with a precision of 5% or better; concentrations of Cl were measured by ion chromatography. In shallow wells <30 m deep, As and P concentrations generally varied by <30%, whereas concentrations of the major ions (Na, K, Mg, Ca and Cl) and the redox-sensitive elements (Fe, Mn, and S) varied over time by up to +/-90%. In wells tapping the deeper aquifers >30 m often below clay layers concentrations of groundwater As were much lower and varied by <10%. The concentrations of major cations also varied by <10% in these deep aquifers. In contrast, the concentration of redox-sensitive constituents Fe, S, and Mn in deep aquifers varied by up to 97% over time. Thus, strong decoupling between variations in As and Fe concentrations is evident in groundwaters from shallow and deep aquifers. Comparison of the time series data with groundwater ages determined by (3)H/(3)He and (14)C dating shows that large seasonal or inter-annual variations in major cation and chloride concentrations are restricted to shallow aquifers and groundwater recharged <5 years ago. There is no corresponding change in As concentrations despite having significant variations of redox sensitive constituents in these very young waters. This is attributed to chemical buffering due to rapid equilibrium between solute and solid As. At two sites where the As content of groundwater in existing shallow wells averages 102 microg/L (range: <5 to 648 microg/L; n=118) and 272 microg/L (range: 10 to 485 microg/L; n=65), respectively, a systematic long-term decline in As concentrations lends support to the notion that flushing may slowly deplete an aquifer of As. Shallow aquifer water with >5 years (3)H/(3)He age show a constant As:P molar ratio of 9.6 over time, suggesting common mechanisms of mobilization.     

Long-term trends and short-term variability of water quality in Skive Fjord, Denmark – nutrient load and mussels are the primary pressures and drivers that influence water quality

Nineteen years of monitoring data from the eutrophic Skive Fjord, Denmark were examined for linkages to external pressures and drivers, including nutrient inputs, meteorology and stocks of blue mussels. Linkages were examined by: 1) time-series analysis to document effects of nutrient reduction programs, 2) Pearson Rank correlations, 3) multivariate statistical analysis (PLS) to identify water quality variables with high predictability and their linkages to pressures, and 4) regression analysis to quantify relationships between pressures and water quality. Freshwater input, nitrogen load and phosphorus load showed decreasing trends through the period 1984–2002. The load reductions were only partially translated into trends in water quality: phosphorus decreased in most seasons, while total nitrogen decreased during winter and spring only. Phosphorus concentration had the highest predictability (explained by seasonal temperature variation) followed by transparency, silicate, tot-N, chlorophyll-a, primary productivity, phytoplankton diversity and phytoplankton turnover. The variation in pressures other than nutrient input confounded the relations between loads and water quality. High biomass of mussels led to reduced chlorophyll-a and increased transparency, while short-term variability in water column mixing led to changes in chlorophyll-a due to nutrient entrainment and coupling to benthic mussels.     

Time trends of perfluorinated compounds from the sediment core of Tokyo Bay, Japan (1950s-2004)

Perfluorinated compounds (PFCs) were detected in sediment core samples collected in Tokyo Bay to reveal their time trends. The core sample deposited during 1950s-2004 was divided into two- to three-year intervals and the concentrations of 24 types of PFCs were determined. Perfluorooctane sulfonate (PFOS) decreased gradually from the early 1990s and its precursor decreased rapidly in the late 1990s, whereas perfluorooctanoic acid (PFOA) increased rapidly. The observed trends were regarded as a reflection of the shift from perfluorooctyl sulfonyl fluoride (PFOSF)-based products to telomer-based products after the phaseout of PFOSF-based products in 2001. The branched isomers of perfluoroundecanoic acid (PFUnDA) and perfluorotridecanoic acid (PFTrDA) were detected in the sample with its ratio of linear-isomer/branched-isomer concentrations decreasing. In this study, we revealed that the sediment core can serve as a tool for reconstructing the past pollution trend of PFCs and can provide interesting evidence concerning their environmental dynamics and time trend.     

不同时间长度监测道路交通噪声比较

目前道路交通噪声的监测时间规定为20 min,监测工作量大。实验采用5 min测量与20 min测量进行比较,结果表明,2种时间测量的最终结果无明显差异。     

黑龙江省近40年洪涝旱灾害及未来减灾对策

洪涝旱灾害是黑龙江省的主要自然灾害。本文提出了黑龙江省洪涝旱灾害指标;分析了1949～1990年洪涝旱灾害的时空分布特性;提出理论损失新概念,较系统地估算洪涝旱灾害造成的实际损失和理论损失;探讨防灾减灾对策。     

城市震害时空序列的展开过程分析

本文系统地介绍城市地震灾害的主体，震害的特征及按时间、空间序列的发展过程。城市震害是多种灾害同时发生、相互影响，并且多种灾害在时空序列上都有发生、发展和延续的过程。通过对以往几次城市地震灾害的现象的研究、展示其在时空序列的分布规律，力求找到各种灾害与抗震救灾活动的对应关系     

河北省沿海风暴潮的发生规律研究

风暴潮是河北省沿海最主要的灾害之一。本文收集整理了最近２０４４年的史料，分析了河北省风暴潮的成因，讨论了风暴潮的时空分布特征、危害程度及区域评价，提出了河北省风暴潮的预警要点。     

Households’ recycling efforts

Households’ recycling effort is often argued to be of an insignificant size. It is also frequently argued that this contribution, if significant, is not a cost to households, since it is voluntary. Thus households’ use of time and energy are frequently disregarded in cost-benefit analyses of stricter recycling targets. In this survey, based on 1162 interviews, we find that sorting at source involves significant extra use of time and energy in the households. On average, each of those asked reported that they use close to half an hour a week for cleaning, sorting and transporting recyclable waste. On average, 185 h is used per tonne of waste. Four out of ten reported that they use warm or hot water to clean the materials. When investigating the motives for sorting waste, we find that many perceive sorting as mandatory, while some in fact find it a pleasant activity in itself. Moral motives for sorting at source are also widespread. A majority would prefer that a company took over the sorting if this were possible, and on average, the respondents are willing to pay US$ 20/year for this service.     

背景噪声的测量和用于修正计算的问题分析及建议

在诸多有关噪声排放的标准中，背景噪声的定义在时间和空间位置方面的规定不够完备；相关的测量的规范方法也未对背景噪声的测量作了规定。实际操作上的“非同时性”给背景噪声的测量结果及用于修正均带来一些失准问题。文中分析了这些问题并提出了初步建议。     

Impacts of meteorology and precursor emission change on O3 variation in Tianjin, China from 2015 to 2021

Deterioration of surface ozone (O₃) pollution in Northern China over the past few years received much attention. For many cities, it is still under debate whether the trend of surface O₃ variation is driven by meteorology or the change in precursors emissions. In this work, a time series decomposition method (Seasonal-Trend decomposition procedure based on Loess (STL)) and random forest (RF) algorithm were utilized to quantify the meteorological impacts on the recorded O₃ trend and identify the key meteorological factors affecting O₃ pollution in Tianjin, the biggest coastal port city in Northern China. After “removing” the meteorological fluctuations from the observed O₃ time series, we found that variation of O₃ in Tianjin was largely driven by the changes in precursors emissions. The meteorology was unfavorable for O₃ pollution in period of 2015-2016, and turned out to be favorable during 2017-2021. Specifically, meteorology contributed 9.3 µg/m³ O₃ (13%) in 2019, together with the increase in precursors emissions, making 2019 to be the worst year of O₃ pollution since 2015. Since then, the favorable effects of meteorology on O₃ pollution tended to be weaker. Temperature was the most important factor affecting O₃ level, followed by air humidity in O₃ pollution season. In the midday of summer days, O₃ pollution frequently exceeded the standard level (>160 µg/m³) at a combined condition with relative humidity in 40%-50% and temperature > 31°C. Both the temperature and the dryness of the atmosphere need to be subtly considered for summer O₃ forecasting.