A quantitative knowledge of the fate of deicing chemicals in the subsurface can be provided by joint analysis of lab experiments with numerical simulation models. In the present study, published experimental data of microbial degradation of the deicing chemical propylene glycol (PG) under flow conditions in soil columns were simulated inversely to receive the parameters of degradation. We evaluated different scenarios of an advection-dispersion model including different terms for degradation, such as zero order, first order and inclusion of a growing and decaying biomass for their ability to explain the data. The general break-through behavior of propylene glycol in soil columns can be simulated well using a coupled model of solute transport and degradation with growth and decay of biomass. The susceptibility of the model to non-unique solutions was investigated using systematical forward and inverse simulations. We found that the model tends to equifinal solutions under certain conditions.

This study examines concentrations of volatile organic compounds (VOCs) measured inside and outside of 162 residences in southeast Michigan, U.S.A. Nested analyses apportioned four sources of variation: city, residence, season, and measurement uncertainty. Indoor measurements were dominated by seasonal and residence effects, accounting for 50 and 31%, respectively, of the total variance. Contributions from measurement uncertainty (<20%) and city effects (<10%) were small. For outdoor measurements, season, city and measurement variation accounted for 43, 29 and 27% of variance, respectively, while residence location had negligible impact (<2%). These results show that, to obtain representative estimates of indoor concentrations, measurements in multiple seasons are required. In contrast, outdoor VOC concentrations can use multi-seasonal measurements at centralized locations. Error models showed that uncertainties at low concentrations might obscure effects of other factors. Variance component analyses can be used to interpret existing measurements, design effective exposure studies, and determine whether the instrumentation and protocols are satisfactory.

We investigated presence and levels of DDT in 163 breast milk samples from four South African villages where, in three of them, malaria is controlled with DDT-sprayed indoors. Mean ΣDDT levels in breast milk were 18, 11, and 9.5 mg/kg mf (milk fat) from the three DDT-sprayed villages, respectively, including the highest ΣDDT level ever reported for breast milk from South Africa (140 mg/kg mf). Understanding the causes for these differences would be informative for exposure reduction intervention. The Provisional Tolerable Daily Intake (PTDI) for DDT by infants, and the Maximum Residue Limit (MRL) were significantly exceeded. DDT had no effect on duration of lactation. There were indications (not significant) from DDT-sprayed villages that first-born female infants drink milk with more ΣDDT than first-born male infants, and vice versa for multipara male and female infants, suggesting gender involvement on levels of DDT in breast milk – requiring further investigation.

Tree-ring width of Picea abies was studied along an altitudinal gradient in the Harz Mountains, Germany, in an area heavily affected by SO₂-related forest decline in the second half of the 20th century. Spruce trees of exposed high-elevation forests had earlier been shown to have reduced radial growth at high atmospheric SO₂ levels. After the recent reduction of the SO₂ load due to clean air acts, we tested the hypothesis that stem growth recovered rapidly from the SO₂ impact. Our results from two formerly damaged high-elevation spruce stands support this hypothesis suggesting that the former SO₂-related spruce decline was primarily due to foliar damage and not to soil acidification, as the deacidification of the (still acidic) soil would cause a slow growth response. Increasing temperatures and deposited N accumulated in the topsoil are likely additional growth-promoting factors of spruce at high elevations after the shortfall of SO₂ pollution.

Agricultural pesticides continue to impair surface water ecosystems, although there are few assessments of interactions with other modifications such as fine sediment and physical alteration for flood drainage. We, therefore, surveyed pesticide contamination and macroinvertebrates in 14 streams along a gradient of expected pesticide exposure using a paired-reach approach to differentiate effects between physically modified and less modified sites. Apparent pesticides effects on the relative abundance of SPEcies At Risk (SPEAR) were increased at sites with degraded habitats primarily due to the absence of species with specific preferences for hard substrates. Our findings highlight the importance of physical habitat degradation in the assessment and mitigation of pesticide risk in agricultural streams.

As the consumption of electricity increases, air pollutants from power generation increase. In metropolitans such as Hong Kong and other Asian cities, the surge of electricity consumption has been phenomenal over the past decades. This paper presents a historical review about electricity consumption, population, and change in economic structure in Hong Kong. It is hypothesized that the growth of electricity consumption and change in gross domestic product can be modeled by 4-parameter logistic functions. The accuracy of the functions was assessed by Pearson's correlation coefficient, mean absolute percent error, and root mean squared percent error. The paper also applies the life cycle approach to determine carbon dioxide, methane, nitrous oxide, sulfur dioxide, and nitrogen oxide emissions for the electricity consumption of Hong Kong. Monte Carlo simulations were applied to determine the confidence intervals of pollutant emissions. The implications of importing more nuclear power are discussed.

This study focused on the presence and distribution of 22 antibiotics, including eight quinolones, nine sulfonamides and five macrolides in mollusks from the Bohai Sea of China. 190 samples of eleven species were collected in 2006, 2007 and 2009. Laboratory analyses revealed that antibiotics were widely distributed in the mollusks with quinolones as the major compounds with concentrations of 0.71∼1575.10 μg/kg, which were up to two orders of magnitude higher than those of sulfonamides (0∼76.75 μg/kg) and macrolides (0∼36.21 μg/kg). The contents of quinolones and macrolides did not show significant changes from 2006, 2007 to 2009, while sulfonamides decreased significantly from 2006 to 2009. Compared with other sites, the city of Dalian was more polluted with quinolones, while Beidaihe was more contaminated with erythromycin and sulfapyridine. In addition, Mactra veneriformis and Meretrix merehjgntrix Linnaeus contained higher concentrations of quinolones and sulfamonomethoxine, while Mytilus edulis had higher levels of erythromycin and sulfapyridine.

Surface fire could induce heat transferring into the soil, creating a carbonized environment, which may alter the chemical compositions of soil organic matters (SOM). In the study, a surface soil was carbonized at up to 600 °C with limited air to simulate soils experiencing a surface fire, and Cr(VI) removal on the carbonized soils was investigated. NMR and FTIR analyses demonstrated a remarkable change of SOM structures at 300–400 °C. TGA-MS spectra indicated that (e.g. C₂H₄, CH₃OH and C₃H₈) were the major components in the evolved gases from the pyrolyzed soil. A maximum amount of Cr(VI) removal (ca. 4 mg g⁻¹ soil) occurred for the 200 °C-carbonized soils, attributed mainly to a significant increase of Cr(VI) reduction by 0.1 M KCl extractable organic carbon (EOC) with abundant carboxylic groups. Nonetheless, the formation of aromatic C upon carbonization of the soil at >400 °C may be responsible for Cr(VI) reduction.

Seasonal variation in mercury (Hg) concentrations and food web structure was assessed for eastern Lake Ontario. Hg concentrations, measured in 6 species of invertebrates and 8 species of fishes, tended to be highest in the spring and lowest in the summer for most biota. Yellow perch (Perca flavescens) exhibited significant ontogenetic shifts in diet and Hg, although such patterns were not evident for other species. Food web structure, as indicated by stable isotope values (δ¹⁵N, δ¹³C) was not static. Log-transformed Hg data were strongly and consistently correlated with δ¹⁵N values for the whole food web in each of the three seasons (slopes, 0.17–0.24) and across the entire year (slope, 0.2). While significantly different between seasons, the regression slope values are still consistent with published global Hg biomagnification rates. Our results indicate that the assessment of Hg trends in Great Lakes must take into account seasonal patterns and time of sampling.

Knowledge of the partitioning and sources of mercury are important to understanding the human impact on mercury levels in Lake Superior wildlife. Fluvial fluxes of total mercury (HgT) and methylmercury (MeHg) were compared to discharge and partitioning trends in 20 sub-basins having contrasting land uses and geological substrates. The annual tributary yield was correlated with watershed characteristics and scaled up to estimate the basin-wide loading. Tributaries with clay sediments and agricultural land use had the largest daily yields with maxima observed near the peak in water discharge. Roughly 42% of HgT and 57% of MeHg was delivered in the colloidal phase. Tributary inputs, which are confined to near-shore zones of the lake, may be more important to the food-web than atmospheric sources. The annual basin-wide loading from tributaries was estimated to be 277 kg yr⁻¹ HgT and 3.4 kg yr⁻¹ MeHg (5.5 and 0.07 mg km⁻² d⁻¹, respectively).