Poplar plantation has the potential to alter the water balance in semiarid Inner Mongolia

Poplar plantation is the most dominant broadleaf forest type in northern China. Since the mid-1990s plantation was intensified to combat desertification along China's northwestern border, i.e., within Inner Mongolia (IM). This evoked much concern regarding the ecological and environmental effects on areas that naturally grow grass or shrub vegetation. To highlight potential consequences of large-scale poplar plantations on the water budget within semiarid IM, we compared the growing season water balance (evapotranspiration (ET) and precipitation (PPT)) of a 3-yr old poplar plantation (Kp₃) and a natural shrubland (Ks) in the Kubuqi Desert in western IM, and a 6-yr old poplar plantation (Bp₆) growing under sub-humid climate near Beijing. The results showed that, despite 33% lower PPT at Kp₃, ET was 2% higher at Kp₃ (228 mm) as compared with Ks (223 mm) in May–September 2006. The difference derived mainly from higher ET at the plantation during drier periods of the growing season, which also indicated that the poplars must have partly transpired groundwater. Estimated growing season ET at Bp₆ was about 550 mm and more than 100% higher than at Kp₃. It is estimated that increases in leaf area index and net radiation at Kp₃ provide future potential for the poplars in Kubuqi to exceed the present ET and ET of the natural shrubland by 100–200%. These increases in ET are only possible through the permanent use of groundwater either directly by the trees or through increased irrigation. This may significantly change the water balance in the area (e.g., high ET at the cost of a reduction in the water table), which renders large-scale plantations a questionable tool in sustainable arid-land management.     

Intracolonial genetic diversity in honeybee (<Emphasis Type="Italic">Apis mellifera</Emphasis>) colonies increases pollen foraging efficiency

Multiple mating by honeybee queens results in colonies of genotypically diverse workers. Recent studies have demonstrated that increased genetic diversity within a honeybee colony increases the variation in the frequency of tasks performed by workers. We show that genotypically diverse colonies, each composed of 20 subfamilies, collect more pollen than do genotypically similar colonies, each composed of a single subfamily. However, genotypically similar colonies collect greater varieties of pollen than do genotypically diverse colonies. Further, the composition of collected pollen types is less similar among genotypically similar colonies than among genotypically diverse colonies. The response threshold model predicts that genotypic subsets of workers vary in their response to task stimuli. Consistent with this model, our findings suggest that genotypically diverse colonies likely send out fewer numbers of foragers that independently search for pollen sources (scouts) in response to protein demand by the colony, resulting in a lower variety of collected pollen types. The cooperative foraging strategy of honeybees involves a limited number of scouts monitoring the environment that then guide the majority of foragers to high quality food sources. The genetic composition of the colony appears to play an important role in the efficiency of this behavior.     

The biodegradation of cable oil components: impact of oil concentration, nutrient addition and bioaugmentation

The effect of cable oil concentration, nutrient amendment and bioaugmentation on cable oil component biodegradation in a pristine agricultural soil was investigated. Biodegradation potential was evaluated over 21 d by measuring cumulative CO₂ respiration on a Micro-Oxymax respirometer and ¹⁴C-phenyldodecane mineralisation using a ¹⁴C-respirometric assay. Cable oil concentration had a significant effect upon oil biodegradation. Microbial respiratory activity increased with increasing cable oil concentration, whereas ¹⁴C-phenydodecane mineralisation decreased. Bioaugmentation achieved the best cable oil biodegradation performance, resulting in increases in cumulative CO₂ respiration, and maximum rates and extents of ¹⁴C-phenyldodecane mineralisation. Generally, nutrient amendment also enhanced cable oil biodegradation, but not to the extent that degrader amendment did. Cable oil biodegradation was a function of (i) cable oil concentration and (ii) catabolic ability of microbial populations. Bioaugmentation may enhance cable oil biodegradation, and is dependent upon composition, cell number and application of catabolic inocula to soil.     

添加剂对伴矿景天修复石灰性铅冶炼污染土壤的影响

为了探讨利用伴矿景天(Sedum plumbizincicola)修复北方重金属污染土壤的可行性,在河南省某铅冶炼形成的污染农田(全镉、铅和锌含量分别为2.65、261和130 mg·kg-1)上种植种子苗或扦插苗伴矿景天,并设对照(CK)、单独尿素(U)、尿素和单质硫(U+S)、尿素与鸡粪(U+CM)配合处理,生长7个月后采样分析.结果表明,种子苗产量比扦插苗高45.8%~162.0%,U、U+CM处理产量均明显高于CK,而U+S处理产量有所下降.种子苗地上部镉含量比扦插苗高15%~99%(p0.05),多数处理铅和锌含量也是种子苗高于扦插苗.与CK相比,各处理措施均导致伴矿景天地上部镉和铅含量下降,而U+S、U+CM处理均导致伴矿景天地上部锌含量上升.从伴矿景天地上部重金属积累量判断,与CK相比,对于镉,仅种子苗U+CM处理镉积累量有所上升;U处理种子苗和扦插苗地上部锌积累量分别比CK上升43.5%和32.3%,两种苗U+S处理锌积累量比CK分别上升11.1%和22.3%.种子苗和扦插苗地上部镉的积累量分别为137~178 g·hm-2和43.7~64.8 g·hm-2,锌的积累量分别为297~1042 g·hm-2和162~326 g·hm-2,两类苗对铅的积累量小于28.8 g·hm-2.U+CM处理对伴矿景天地上部锌吸收的促进作用主要是由于鸡粪中含有大量的有效锌.以上结果表明,可利用种子苗伴矿景天结合尿素的施用对铅冶炼污染石灰性土壤进行修复.     

Passive flux meter measurement of water and nutrient flux in saturated porous media: bench-scale laboratory tests

The passive nutrient flux meter (PNFM) is introduced for simultaneous measurement of both water and nutrient flux through saturated porous media. The PNFM comprises a porous sorbent pre-equilibrated with a suite of alcohol tracers, which have different partitioning coefficients. Water flux was estimated based on the loss of loaded resident tracers during deployment, while nutrient flux was quantified based on the nutrient solute mass captured on the sorbent. An anionic resin, Lewatit 6328 A, was used as a permeable sorbent and phosphate (PO4(3-)) was the nutrient studied. The phosphate sorption capacity of the resin was measured in batch equilibration tests as 56 mg PO4(3-) g(-1), which was determined to be adequate capacity to retain PO4(3-) loads intercepted over typical PNFM deployment periods in most natural systems. The PNFM design was validated with bench-scale laboratory tests for a range of 9.8 to 28.3 cm d(-1) Darcy velocities and 6 to 43 h deployment durations. Nutrient and water fluxes measured by the PNFM averaged within 6 and 12% of the applied values, respectively, indicating that the PNFM shows promise as a tool for simultaneous measurement of water and nutrient fluxes.     

Predicted taxonomic patterns in pheromone production by longhorned beetles

Males of five species of three tribes in the longhorned beetle subfamily Cerambycinae produce volatile pheromones that share a structural motif (hydroxyl or carbonyl groups at carbons two and three in straight-chains of six, eight, or ten carbons). Pheromone gland pores are present on the prothoraces of males, but are absent in females, suggesting that male-specific gland pores could provide a convenient morphological indication that a species uses volatile pheromones. In this article, we assess the taxonomic distribution of gland pores within the Cerambycinae by examining males and females of 65 species in 24 tribes using scanning electron microscopy. Gland pores were present in males and absent in females of 49 species, but absent in both sexes of the remaining 16 species. Pores were confined to indentations in the cuticle. Among the species that had male-specific gland pores were four species already known to produce volatile compounds consistent with the structural motif. These findings support the initial assumption that gland pores are associated with the production of pheromones by males. There were apparently no taxonomic patterns in the presence of gland pores. These findings suggest that volatile pheromones play an important role in reproduction for many species of the Cerambycinae, and that the trait is evolutionarily labile.     

Distribution of polychlorinated dibenzo-p-dioxins and dibenzofurans in suspended sediments, dissolved phase and bottom sediment in the Houston Ship Channel

Spatial distributions of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) in the water column and bottom sediments of the Houston Ship Channel in Texas were measured three times over a 1-year period. Total TEQ concentrations in water ranged from 0.01 to 0.25 pg/l for the dissolved phase and from 0.09 to 2.91 pg/l for the suspended phase, while TEQ concentrations in bottom sediments varied from 0.9 to 139.8 ng/kg dry wt. The dissolved concentrations were lower than their respective suspended concentrations, with average dissolved/suspended ratios between 0.11 and 0.59 for individual congeners. More than 89% of the total concentration of 2378-substituted PCDD/PCDFs was attributable to OCDD but 2378-TCDD was the major contributor to total TEQ for the three sampled media. Average logs of organic carbon-normalized suspended sediment-dissolved partitioning coefficients (logK(oc)(obs)) varied between 4.92 and 8.59 l/kg-oc; while in the bottom sediment-dissolved interface, logK(oc)(obs) values ranged from 5.48 to 8.48 l/kg-oc. Observed logK(oc)values varied within a factor of 0.64-1.26 from equilibrium logK(oc) values, suggesting fluxes of PCDD/PCDFs across the interfaces. It was found that in the HSC, on average, the tendency of a compound to move from the particulate phase to the dissolved phase decreases with increasing K(ow).     

Integration of traditional and innovative characterization techniques for flux-based assessment of Dense Non-aqueous Phase Liquid (DNAPL) sites

Key attributes of the source zone and the expanding dissolved plume at a trichloroethene (TCE) site in Australia were evaluated using trends in groundwater monitoring data along with data from on-line volatile organic compound (VOC) samplers and passive flux meters (PFMs) deployed in selected wells. These data indicate that: (1) residual TCE source mass in the saturated zone, estimated using two innovative techniques, is small ( 10 kg), which is also reflected in small source mass discharge ( 3 g/day); (2) the plume is disconnecting, based on TCE concentration contours and TCE fluxes in wells along a longitudinal transect; (3) there is minimal biodegradation, based on TCE mass discharge of  6 g/day at a plume control plane  175 m from source, which is also consistent with aerobic geochemical conditions observed in the plume; and (4) residual TCE in the vadose zone provides episodic inputs of TCE mass to the plume during infiltration/recharge events. TCE flux data also suggest that the small residual TCE source mass is present in the low-permeability zones, thus making source treatment difficult. Our analysis, based on a synthesis of the archived data and new data, suggests that source treatment is unwarranted, and that containment of the large TCE plume ( 1.2 km long,  0.3 km wide; 17 m deep;  2000–2500 kg TCE mass) or institutional controls, along with a long-term flux monitoring program, might be necessary. The flux-based site management approach outlined in this paper provides a novel way of looking beyond the complexities of groundwater contamination in heterogeneous domains, to make intelligent and informed site decisions based on strategic measurement of the appropriate metrics.     

Assessment of spiking procedures for the introduction of a phenanthrene-LNAPL mixture into field-wet soil

Laboratory based studies on the fate of organic contaminants in soil typically requires the test compound(s) to be spiked into the test medium. Consequently, such studies are inherently dependent on the homogeneity of the contaminant within the spiked soil. Three blending methods were compared for the addition of a phenanthrene-transformer oil mixture into field-wet soil. Spiking homogeneity, reproducibility and artefacts were assessed based on dichloromethane and hydroxypropyl-beta-cyclodextrin chemical extractability, and bacterial mineralization. Spiking using a stainless-steel spoon, consistently produced good spike homogeneity as determined by sample oxidation, chemical extraction and mineralization, and was consistently more reliable than either the Waring blender or modified bench drill. Overall, neither transformer oil-concentration nor blending method influenced chemical extractability or mineralization of the PAH following 1 day equilibration. In general, spiking procedures require validation prior to use, as homogeneity cannot be assured.