Atrazine contamination in agricultural soils from the Yangtze River Delta of China and associated health risks

Atrazine is one of the most widely applied and persistent herbicides in the world. In view of limited information on the regional contamination of atrazine in soils in China, this study investigated the spatial distribution and environmental impacts of atrazine in agricultural soils collected from the Yangtze River Delta (YRD) as an illustrative analysis of rapidly developing regions in the country. The results showed that the concentrations of atrazine in the YRD agricultural soils ranged from <1.0 to 113 ng/g dry weight, with a mean of 5.7 ng/g, and a detection rate of 57.7 % in soils. Pesticide factory might be a major source for the elevated levels of atrazine in Zhejiang Province. The contamination of atrazine was closely associated with land use types. The concentrations and detection rates of atrazine were higher in corn fields and mulberry fields than in rice paddy fields. There was no significant difference in compositions of soil microbial phospholipids fatty acids among the areas with different atrazine levels. Positive relationship (R = 0.417, p < 0.05, n = 30) was observed between atrazine and total microbial biomass. However, other factors, such as soil type and land management practice, might have stronger influences on soil microbial communities. Human health risks via exposure to atrazine in soils were estimated according to the methods recommended by the US EPA. Atrazine by itself in all the soil samples imposed very low carcinogenic risks (<10^?6) and minimal non-cancer risks (hazard index <1) to adults and children.     

SBR降解动力学研究

采用SBR工艺处理有机废水，在已有工艺条件下对生物降解动力学进行了研究，得出生物降解反应为一级反应。研究表明，用Monod公式能较好反映出有机物的降解规律，确定了其动力学参数V_max=14.6306 d^-1，K_s=83.2993 mg/L，得出SBR降解动力学模型为V=14.6306X·S/(83.2993+S)。利用以动力学为基础的动态模拟法优化SBR工艺，实验结果表明该方法合理可行，对SBR的设计与运行有一定的指导作用，可作为SBR反应器扩大实验和设计的依据。     

Investigation of PM2.5 pollution during COVID-19 pandemic in Guangzhou, China

The COVID-19 pandemic has raised awareness about various environmental issues, including PM_2.5 pollution. Here, PM_2.5 pollution during the COVID-19 lockdown was traced and analyzed to clarify the sources and factors influencing PM_2.5 in Guangzhou, with an emphasis on heavy pollution. The lockdown led to large reductions in industrial and traffic emissions, which significantly reduced PM_2.5 concentrations in Guangzhou. Interestingly, the trend of PM_2.5 concentrations was not consistent with traffic and industrial emissions, as minimum concentrations were observed in the fourth period (3/01-3/31, 22.45 μg/m³) of the lockdown. However, the concentrations of other gaseous pollutants, e.g., SO₂, NO₂ and CO, were correlated with industrial and traffic emissions, and the lowest values were noticed in the second period (1/24-2/03) of the lockdown. Meteorological correlation analysis revealed that the decreased PM_2.5 concentrations during COVID-19 can be mainly attributed to decreased industrial and traffic emissions rather than meteorological conditions. When meteorological factors were included in the PM_2.5 composition and backward trajectory analyses, we found that long-distance transportation and secondary pollution offset the reduction of primary emissions in the second and third stages of the pandemic. Notably, industrial PM_2.5 emissions from western, southern and southeastern Guangzhou play an important role in the formation of heavy pollution events. Our results not only verify the importance of controlling traffic and industrial emissions, but also provide targets for further improvements in PM_2.5 pollution.     

Soot Control During the Combustion of Polystyrene

This paper describes an experimental study on the control of soot formation during the combustion of polystyrene (PS). A stable, twodimensional flame generated by using a Wolfhard-Parker type diffusion flame burner was used to simulate practical combustion situations. The combustion characteristics, effects of operating conditions on soot formation, and the effectiveness of various metallic additives as soot suppressants were investigated. It was found that soot yield could not be significantly reduced by controlling the oxidizer (air) flow rate. Increasing the O₂ mole fraction of the oxidlzer increased soot yield under typical operating conditions. However, soot yield could be greatly reduced by adding small amounts of air into the pyrolysis zone of the flame. The additional air would probably increase the combustion reaction rate while decreasing the soot precursor formation rate, thereby causing the observed effect. It was thus suggested that effective soot control could be accomplished by improving mixing between air and the PS devolatilizatlon products In practical combustion situations. The metallic additives tested in this study were the salts of Na, K, Ca, and Ba. Among these salts, Ca was the least effective in reducing soot, and K and Na were nearly equally effective. Ba was much more effective than all the others, and Its effectiveness was strongly dependent on its addition rate.     

Phosphorus in Hawaiian kikuyugrass pastures and potential phosphorus release to water

Pasture systems in Hawaii are based primarily on kikuyugrass (Pennisetum clandestinum Hochst. ex Chiov.). Relationships among kikuyugrass P concentration, animal P requirements, and various soil P determinations are needed to help identify source areas for implementing pasture management strategies to limit P loss via overland flow. A total of 51 rotationally stocked kikuyugrass pastures (>20 yr old) with contrasting soil chemical properties were sampled. A satisfactory predictive relationship between modified-Truog (MT)-extractable phosphorus (P(MT)) and dissolved (<0.45-mum pore diameter), molybdate-reactive phosphorus (DRP) desorbed from soil in a water extract (DRP(WE)) was found when 0- to 4-cm-depth data for the soil orders with medium to high DRP(WE) (two Mollisols and an Inceptisol) were pooled separately from those with low DRP(WE) (five Andisols, three Ultisols, and an Oxisol). The oxalate phosphorus saturation index (PSI(ox)) procedure was the best predictor of DRP(WE) across soil orders when oxalate-extractable molybdate-reactive phosphorus (RP(ox)) was used to calculate PSI(ox) (PSI(ox)RP) rather than when total oxalate-extractable phosphorus (TP(ox)) was used (PSI(ox)TP). There was little DRP(WE) until PSI(ox)RP exceeded 6% or PSI(ox)TP exceeded 8%. A more empirical dilute-acid phosphorus saturation index (PSI(MT)) was also calculated using P(MT) and MT-extractable iron (Fe(MT)) and aluminum (Al(MT)). The PSI(MT) procedure showed some utility in predicting DRP(WE), was positively related to the PSI(ox) procedures, and can be more readily performed in agronomic soil testing laboratories than PSI(ox). The present research suggests that while Hawaiian kikuyugrass pastures tend to be sufficient to high in forage P, potential soil P release to water only appeared to be a possible environmental concern for the Mollisol and Inceptisol sites.     

Use of spent mushroom compost to bioremediate PAH-contaminated samples

Spent mushroom compost (SMC) is a bulky waste byproduct of mushroom industry and produced abundantly. The SMC of Pleurotus pulmonarius immobilized laccase (0.88 mmoles min(-1) g(-1)) and manganese peroxidase (0.58 mmoles min(-1) g(-1)) of which the optimal temperatures were 45 and 75 degrees C, respectively. In laboratory test, complete degradative removal of individual naphthalene, phenanthrene, benzo[a]pyrene and benzo[g,h,i]perylene (200 mg PAH kg(-1) sandy-loam soil) by 5% SMC was obtained in two days under continuous shaking at 80 degrees C. The SMC-treated PAH samples had significantly reduced or removed their toxicities as revealed by the Microtox bioassay. These results were confirmed by gas chromatography-mass spectrometry analysis on the breakdown products. A phthalic derivative which is reported as a degradative product of PAHs by ozonation or ligninolysis was also detected in the SMC-treated samples. The results demonstrate the potential in employing SMC in ex situ bioremediation.     

Bacteria on housefly eggs, Musca domestica, suppress fungal growth in chicken manure through nutrient depletion or antifungal metabolites

Female houseflies, Musca domestica (Diptera: Muscidae), lay their eggs in ephemeral resources such as animal manure. Hatching larvae compete for essential nutrients with fungi that also colonize such resources. Both the well-known antagonistic relationship between bacteria and fungi and the consistent presence of the bacterium Klebsiella oxytoca on housefly eggs led us to hypothesize (1) that K. oxytoca, and possibly other bacteria on housefly eggs, help curtail the growth of fungal resource competitors and (2) that such fungi indeed adversely affect the development of housefly larvae. Bacteria washed from housefly eggs significantly reduced the growth of fungi in chicken manure. Nineteen bacterial strains and ten fungal strains were isolated from housefly eggs or chicken manure, respectively. Co-culturing each of all the possible bacterium–fungus pairs revealed that the bacteria as a group, but no single bacterium, significantly suppressed the growth of all fungal strains tested. The bacteria's adverse effect on fungi is due to resource nutrient depletion and/or the release of antifungal chemicals. Well-established fungi in resources significantly reduced the number of larval offspring that completed development to adult flies. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Effect of starvation on the energy budget of two Asian horseshoe crab species: <Emphasis Type="Italic">Tachypleus tridentatus</Emphasis> and <Emphasis Type="Italic">Carcinoscorpius rotundicauda</Emphasis> (Chelicerata: Xiphosura)

Energy budget is one of the most studied parameters in aquatic animals under environmental challenge. To examine how prolonged starvation would affect their energy budget, respiration rate (RR), ammonia excretion rate (ER), oxygen consumption to ammonia–nitrogen excretion (O:N) ratio and scope for growth (SfG) representing the balance between energy intake and metabolic output, two Asian horseshoe crab species, Tachypleus tridentatus and Carcinoscorpius rotundicauda, were investigated in two feeding regimes (fed and starved) over a period of 7 weeks. No significant effects of species and time course, as well as their interaction, on absorption efficiency were observed in the fed treatments. For both species, RR and ER of the starved treatments significantly decreased, while their O:N ratio significantly increased during the experiment. However, such values for the fed treatments remained relatively stable over the study period. A rapid reduction in SfG was only apparent in the first week of the starved treatments for both species; thereafter, their SfG remained relatively constant. In the fed treatments, SfG of T. tridentatus was significantly lower than that of C. rotundicauda throughout the experiment. In general, C. rotundicauda showed a greater decrease in SfG under starvation than T. tridentatus, suggesting that they may have a more competitive life-history strategy for adjusting to poor nutritional conditions.     

Copper extraction effectiveness and soil dissolution issues of EDTA-flushing of artificially contaminated soils

Ethylenediaminetetraacetic acid (EDTA) was used as a reference chelating agent in column experiments to investigate the effectiveness of chelant-enhanced flushing of soils artificially contaminated under various conditions (low/high Cu loading, and aging). The associated soil dissolution issues were of particular concern. Dissolution of indigenous Fe/Al oxides, Ca carbonates and organic matter was monitored over the course of flushing. Regardless of contamination condition, above 85% extraction efficiency could be accomplished by 10(-2) and 10(-3)M EDTA-flushing, but not 10(-4)M. The Cu extraction kinetics positively correlated to EDTA concentration but inversely to Cu loading in soils. In addition to extraction from weakly sorbed fractions, a large portion of Cu was extracted from oxide, organic matter and residual fractions, which appears to derive from soil dissolution. Cumulative dissolved amounts of Fe, Al, and Ca were found to reach as high as hundreds of mgkg(-1), which were comparable to Cu contamination. Soil organic matter, which is known to strongly interact with Fe and Al oxides, was also mobilized. The rate and extent of these soil dissolutions were also positively correlated to EDTA concentration. Therefore, the co-extraction of soil minerals and organic matter during chelant-enhanced flushing, which would alter both physical structure and chemical properties of the soils, is detrimental to future land use and deserves greater attention. The concentration of chelating agent is the most crucial factor for an effective soil flushing with minimal damage.     

Biodegradation capacity of tributyltin by two Chlorella species

Two microalgal species, Chlorella vulgaris and Chlorella sp., which showed high tributyltin (TBT) tolerant ability were investigated for their capabilities in degrading TBT at sublethal concentration. The distribution of TBT and its degraded products dibutyltin (DBT) and monobutyltin (MBT) in the incubation medium, extracellular surface and intracellular fraction were monitored during an exposure period of 14 days. Results showed that biosorption of TBT by the algal cell wall was the major mechanism in reducing 40% of the initial TBT from the medium in the first 2 days. The half-life of TBT incubated with C. vulgaris was 60 h while that of Chlorella sp. was 80 h. The occurrence of DBT at Day 1 in the culture medium provided direct evidence to the biodegradation of TBT by both Chlorella species. At the end of the experimental period, 27 and 41% of the original TBT were recovered as DBT and MBT in cultures of C. vulgaris, respectively. In contrast, DBT appeared to be the only degradation product of Chlorella sp. and only 26% of the original TBT was transformed to DBT. Despite the same genus, TBT was debutylated to a greater extent to MBT by C. vulgaris, while DBT was the end degradation product by Chlorella sp. The capability of such debutylating process therefore accounted for the higher tolerant ability of C. vulgaris than Chlorella sp.