Comparison of arsenic resistance in Mediterranean woody shrubs used in restoration activities

Myrtus communis, Arbutus unedo and Retama sphaerocarpa are Mediterranean shrubs widely used in revegetation of semiarid degraded soils. The aim of this work is to study the resistance of these plants to arsenic under controlled conditions, in order to evaluate their potential use in revegetation and/or phytoremediation of As-polluted soils. R. sphaerocarpa showed higher resistance to As than M. communis or A. unedo according to its higher EC50, P status and P/As molar ratio in both, roots and shoots, and the lower increases in lipid peroxidation and decrease of chlorophyll levels in response to arsenic, while the highest arsenate sensitivity was obtained for A. unedo. Arsenic was mainly retained in roots, and, although M. communis accumulated higher arsenic amounts than the other two species, R. sphaerocarpa showed the highest root to shoot transfer. Most of the studied parameters (chlorophylls, MDA and total thiols) showed significant correlation with arsenic concentration in roots and leaves of plants, so they can be useful indexes in the diagnosis of arsenic toxicity in these species. According to our results, both M. communis and R. sphaerocarpa could be used in the revegetation of moderately arsenic contaminated sites.     

Using Mediterranean shrubs for the phytoremediation of a soil impacted by pyritic wastes in Southern Spain: a field experiment

Re-vegetation is the main aim of ecological restoration projects, and in Mediterranean environments native plants are desirable to achieve successful restoration. In 1998, the burst of a tailings dam flooded the Guadiamar river valley downstream from Aznalcóllar (Southern Spain) with sludges that contained elevated concentrations of metals and metalloids, polluting soils and waters. A phytoremediation experiment to assess the potential use of native shrub species for the restoration of soils affected by the spillage was performed from 2005 to 2007, with soils divided into two groups: pH < 5 and pH > 5. Four native shrubs (Myrtus communis, Retama sphaerocarpa, Rosmarinus officinalis and Tamarix gallica) were planted and left to grow without intervention. Trace element concentrations in soils and plants, their extractability in soils, transfer factors and plant survival were used to identify the most-interesting species for phytoremediation. Total As was higher in soils with pH < 5. Ammonium sulphate-extractable zinc, copper, cadmium and aluminium concentrations were higher in very-acid soils, but arsenic was extracted more efficiently when soil pH was >5. Unlike As, which was either fixed by Fe oxides or retained as sulphide, the extractable metals showed significant relationships with the corresponding total soil metal concentration and inverse relationships with soil pH. T. gallica, R. officinalis and R. sphaerocarpa survived better in soils with pH > 5, while M. communis had better survival at pH < 5. R. sphaerocarpa showed the highest survival (30%) in all soils. Trace element transfer from soil to harvestable parts was low for all species and elements, and some species may have been able to decrease trace element availability in the soil. Our results suggest that R. sphaerocarpa is an adequate plant species for phytostabilising these soils, although more research is needed to address the self-sustainability of this remediation technique and the associated environmental changes.     

Generality of Models that Predict the Distribution of Species: Conservation Activity and Reduction of Model Transferability for a Threatened Bustard

Abstract:  Predictive models can help clarify the distribution of poorly known species but should display strong transferability when applied to independent data. Nevertheless, model transferability for threatened tropical species is poorly studied. We built models predicting the incidence of the critically endangered Bengal Florican ( Houbaropsis bengalensis ) within the Tonle Sap (TLS) floodplain, Cambodia. Separate models were constructed with soil, land-use, and landscape data and species incidence sampled over the entire floodplain (12,000 km²) and from the Kompong Thom (KT) province (4000 km²). In each case, the probability of Bengal Florican presence within randomly selected 1 × 1 km squares was modeled by binary logistic regression with multimodel inference. We assessed the transferability of the KT model by comparing predictions with observed incidence elsewhere in the floodplain. In terms of standard model-validation statistics, the KT model showed good spatial transferability. Nevertheless, it overpredicted florican presence outside the KT calibration region, classifying 491 km² as suitable habitat compared with 237 km² predicted as suitable by the TLS model. This resulted from higher species incidence within the calibration region, probably owing to a program of conservation education and enforcement that has reduced persecution there. Because both research and conservation activity frequently focus on areas with higher density, such effects could be widespread, reducing transferability of predictive distribution models.     

Mercury bioaccumulation and phytotoxicity in two wild plant species of Almadén area

Mercury is a widely distributed environmental pollutant, able to induce toxicity in living organisms, including higher plants. Some plant species are able to grow in mine sites, like the Almadén zone in Spain. Our study focus on two of these plant species, Rumex induratus and Marrubium vulgare and their responses to natural Hg exposure. Total Hg concentration in the soil below the plants could be classified as toxic, although the available fraction was low. Hg availability was higher for the M. vulgare than for the R. induratus plot. Hg concentrations in field plants of R. induratus and M. vulgare grown on these soils can be considered as phytotoxic, although no symptoms of Hg toxicity were observed in any of them. According to the BAF ([Hg]_tissue/[Hg]_avail), R. induratus showed a higher ability in Hg uptake and translocation to shoots, as well as higher concentrations of MDA and –SH:Hg ratios, so that this plant is more sensitive to Hg than M. vulgare. The resistance to Hg and the capability to extract Hg from the soil make both M. vulgare and R. induratus good candidates for Hg phytoremediation of contaminated soils.     

南北极大气气溶胶单颗粒成分特点研究

运用定量电子探针微区分析技术(EPMA)分别测定了采自北极新奥尔松地区(78?55′N、11?56′E)和南极乔治王岛(62?13′S、58?47′W)极昼天气下PM10大气颗粒物样品.结果表明,北极和南极大气颗粒物化学成分存在很大差异,表现出各自不同的特点.北极的颗粒类型中,“反应的海盐”和“矿物尘”分别占颗粒总数的44%和27%,“新鲜海盐”所占的比例不到10%,“反应的海盐”中以含硝酸盐的颗粒为主,反映了外来物质或人为污染对该地气溶胶影响较大;南极的颗粒类型中,“新鲜海盐”占总数的74%左右,“反应的海盐”占19%,反应的海盐全部含硫酸盐、未发现含硝酸盐的颗粒,推测与海盐反应的含硫物质来源于海洋浮游生物代谢过程产生的二甲硫醚(DMS)及其降解产物,而与人为污染无关.     

畜禽源氨气排放因子估算方法研究

畜禽养殖过程中产生的氨气(NH_3)在人为源NH_3排放中所占的比重较大,对二次气溶胶的形成起重要作用.由于我国畜禽饲养品种多样,各地气候条件和饲养规模存在较大差异,且影响NH_3排放的因素复杂多变,因此,获得准确的畜禽NH_3排放因子较为困难.本文以山西省太原市及其周边地区典型猪场、鸡场、牛场、羊场为实验场所,以杜洛克猪与长白猪的杂交猪、海兰褐蛋鸡、白羽肉鸡、杜泊羊与晋中绵羊的杂交羊、中国黑白花奶牛、金色阿奎丹与西门塔尔杂交肉牛为研究对象,通过3种方法估算它们的NH_3排放因子.结果表明:基于日粮成分和氮代谢沉积率的粗蛋白估算法过程简单、计算便捷、适合所有种类的畜禽,但未考虑NH_3挥发过程中的吸收转化及施肥利用,因而误差较大;基于排泄物含氮率和NH_3挥发率的物质流法涉及粪肥管理的不同阶段,全面考虑了NH_3产生、损失的全过程,与实际情况接近,但参数较多、周期较长、计算过程复杂;基于畜禽舍内NH_3浓度的直接测量法数据来源可靠、参数少,但只能用于相对封闭的环境,不适合牛场和羊场等敞开或半敞开的圈舍,且该方法没有考虑粪尿离开畜禽舍以后的储藏、还田过程,计算结果偏小.通过3种方法的互相印证和比对,猪、奶牛、肉牛、羊、蛋鸡、肉鸡6种实验动物的NH_3排放因子分别为6.90、36.53、22.99、3.94、0.54、0.46 kg·头(只)~(-1)·a~(-1).本研究可以为我国畜禽源NH_3排放因子的本地化测定提供一定的参考,并为准确估算畜禽NH_3排放量、做好农业源NH_3排放清单编制和污染防治工作提供参考.     

Use of perlite in cadmium plant studies: an approach to polluted soil conditions

Two different types of hydroponic cultures, "water culture" and "perlite system", were compared using white lupin plants (Lupinus albus L., cv. Marta) under different Cd treatments: 0, 0.2, 0.6, 2, 4, 6, 13, 20, 40 and 60 microM (water culture) and 0.2, 2, 20, 60 and 150 microM (moistened perlite). Fresh weight, shoot and root length, and total Cd concentration in the plants were measured. Moreover, a batch experiment was carried out to study the ability of perlite to adsorb and desorb Cd from nutrient solution. Lupin plants under Cd treatments in "water culture" showed a higher growth inhibition than those grown on perlite. A high positive correlation between Cd concentration in the plant and Cd supply was obtained regardless of the substrate used. Moreover, a high positive correlation between Cd doses with the "perlite system" and their equivalent Cd doses estimated for the "water culture" system was observed. Thus, the "water culture-equivalent" Cd doses were 14 times lower than the Cd doses in the perlite system. On the other hand, desorbed Cd concentrations were calculated giving values 12 times lower than the tested Cd doses.