Socio-economic Comparison Between Traditional and Improved Cultivation Methods in Agroforestry Systems, East Usambara Mountains, Tanzania

The East Usambara Mountains, recognized as one of the 25 most important biodiversity hot spots in the world, have a high degree of species diversity and endemism that is threatened by increasing human pressure on resources. Traditional slash and burn cultivation in the area is no longer sustainable. However, it is possible to maintain land productivity, decrease land degradation, and improve rural people’s livelihood by ameliorating cultivation methods. Improved agroforestry seems to be a very convincing and suitable method for buffer zones of conservation areas. Farmers could receive a reasonable net income from their farm with little investment in terms of time, capital, and labor. By increasing the diversity and production of already existing cultivations, the pressure on natural forests can be diminished. The present study shows a significant gap between traditional cultivation methods and improved agroforestry systems in socio-economic terms. Improved agroforestry systems provide approximately double income per capita in comparison to traditional methods. More intensified cash crop cultivation in the highlands of the East Usambara also results in double income compared to that in the lowlands. However, people are sensitive to risks of changing farming practices. Encouraging farmers to apply better land management and practice sustainable cultivation of cash crops in combination with multipurpose trees would be relevant in improving their economic situation in the relatively short term. The markets of most cash crops are already available. Improved agroforestry methods could ameliorate the living conditions of the local population and protect the natural reserves from human disturbance.     

Effect of corn root exudates on the degradation of atrazine and its chlorinated metabolites in soils

DIMBOA (3,4-dihydro-2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3-one), a major benzoxazinone of Poaceae plants, was isolated and purified from corn seedlings. The effect of isolated and purified DIMBOA on the degradation of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine], and its toxic breakdown products, desethylatrazine [2-chloro-4-amino-6-(isopropylamino)-s-triazine; DEA] and desisopropylatrazine [2-chloro-4-(ethylamino)-6-amino-s-triazine; DIA], was studied in the absence of plants using batch experiments, while the effect of corn root exudates on these compounds was determined in hydroponic experiments. Degradation experiments were performed in the presence and absence of 50 microM, 1 mM, or 5 mM DIMBOA resulting in ratios of DIMBOA to pesticide of 1:1, 20:1, and 100:1. We observed a 100% degradation of atrazine to hydroxyatrazine within 48 h at a ratio of DIMBOA to atrazine of 100:1. DIMBOA had the largest effect on atrazine, while it was about three times less effective on DEA and DIA. Corn (Zea mays L. cv. LG 2185) was exposed to 10 mg L(-1) of either atrazine, DEA, or DIA for 11 d in a growth chamber experiment. Up to 4.3 micromol L(-1) d(-1) of hydroxyatrazine were formed in the nutrient solutions by plants exposed to atrazine, while the formation of hydroxylated metabolites from plants exposed to DEA and DIA was smaller and also delayed. The formation of hydroxylated metabolites increased in the solution with plant age in all atrazine, DEA, and DIA treatments. HMBOA (3,4-dihydro-2-hydroxy-7-methoxy-2H-1,4-benzoxazin-3-one), the lactam precursor of DIMBOA, and a tentatively identified derivative of MBOA (2,3-dihydro-6-methoxy-benzoxazol-2-one) were detected in the corn root exudates. Mass balance calculations revealed that up to 30% of the disappearance of atrazine and DEA, and up to 10% of DIA removal from the solution medium in our study could be explained by the formation of hydroxylated metabolites in the solution itself. Our results show that higher plants such as corn have the potential to promote the hydrolysis of triazine residues in soils by exudation of benzoxazinones.     

Nitrogen removal in laboratory model leachfields with organic-rich layers

Septic system leachfields can release dissolved nitrogen in the form of nitrate into ground water, presenting a significant source of pollution. Low cost, passive modifications, which increase N removal in traditional leachfields, could substantially reduce the overall impact on ground water resources. Bench-scale laboratory models were constructed to evaluate the effect of placing an organic layer below the leachfield on total N removal. The organic layer provides a carbon source for denitrification. Column units representing septic leachfields were constructed with sawdust-native soil organic layers placed 0.45 m below the influent line and with thicknesses of 0.0, 0.3, 0.6, and 0.9 m. Using a synthetic septic tank effluent, NO(3)-N concentrations at 3.8 m below the influent line were consistently below 1 mg L(-1) during 10 months of operation compared with a NO(3)-N concentration of nearly 12 mg L(-1) in the control column. The average total N removal increased from 31% without the organic layer to 67% with the organic layer. Total N removal appeared limited by the extent of organic N oxidation and nitrification in the 0.45-m aerobic zone. Design modifications targeted at improving nitrification above the organic layer may further increase total N removal. Increased organic layer thicknesses from 0.3 m to 0.9 m did not significantly improve average total N removal, but caused a shift in residual nitrogen from organic N to ammonia N. Results indicate that addition of a layer of carbon source material at least 0.3 m thick below a standard leachfield substantially improves total N removal.     

On measuring wealth: a case study on the state of Queensland

In order for policy makers to plan effectively for sustainable development, there is a need for measures of welfare that consider changes in the natural capital stock. Current measures based on conventional national accounting are flawed because they are based solely on flow measures and do not account for environmental effects. In this paper, we use an expanded measure of wealth to estimate the value of natural capital for Queensland. The state's stock of natural capital is valued at A dollar 355.6 billion, of which non-timber forest resources account for 45.3%, ecosystem services 20.0%, and mineral resources 17.6%. This figure is a conservative estimate of the true value since some significant components such as the ecological and life-support functions of the environment are excluded. The estimates highlight the relative importance of different forms of natural capital and can be used to draw the attention of policymakers to the need to give adequate weight to the value of such services in decision-making processes.     

铜污染场地土壤的原位电动强化修复

电动修复技术是一种新型的污染土壤修复技术,相关的理论和实验室小试研究较多,但鲜见野外现场条件下的原位修复研究。本研究以某电镀厂铜污染区为修复对象,以可生物降解的络合剂乳酸和柠檬酸为阴极池增强试剂,考察在原位条件下电动修复技术对土壤中铜的去除效率,并评估修复过程的电能消耗。结果表明:在电压梯度7.5 V·m-1,阴极池乳酸和柠檬酸浓度为0.5 mol·L-1,处理24 d(乳酸处理)和17 d(柠檬酸处理)的条件下,乳酸处理较柠檬酸处理电流要高、且阴阳极池溶液和土壤的pH、电导率变化要小;乳酸处理后土壤铜含量明显下降(阳极和阴极附近土壤铜去除率分别为52.6%和35.7%),而柠檬酸处理条件下阳极和阴极附近铜的去除效率分别为27.2%和-17.5%,这可能与其较低的电流和较短的处理时间有关。与现有文献比较,乳酸处理总能耗(15.7 kWh·m-3)处于较低水平,而Cu的去除率处于较高水平(35.7%~52.6%),优于文献报道的电动修复去除效率和电能消耗。     

铝土矿浮选尾矿对水泥砂浆性能的影响

以铝土矿浮选尾矿为研究对象,探讨了烘干尾矿、尾矿浆用作水泥基材料掺和料的可行性,测定了其对砂浆基本性能的影响。结果表明,尾矿作为混合材料能显著缩短水泥的凝结硬化时间;尾矿作为掺和料能够增加砂浆的保水性,提高砂浆的吸水率,降低砂浆的稠度;掺入10%的尾矿对砂浆的密度和力学性能具有较好的改善作用。因此,尾矿作为掺和料是可行的,有利于消耗废渣,改善生态环境。     

Petroleum hydrocarbon concentrations in eight mollusc species along Tamilnadu coast, Bay of Bengal, India

Eight mollusc species and sediment samples collected from three different stations along Tamilnadu coast, Bay of Bengal, India were analysed for the levels of petroleum hydrocarbons to elucidate the status of the petroleum residues in mollusc meant for human consumption. The concentrations of petroleum hydrocarbons in sediments along Tamilnadu coast varied from 5.04–25.5 g/g dw (dry weight). High concentration of petroleum hydrocarbons in the sediment of Uppanar estuary (25.5 1.45 g/g dw) was perhaps land and marine based anthropogenic sources of this region. The petroleum hydrocarbon residues in eight mollusc species collected from Uppanar, Vellar and Coleroon estuaries varied between 2.44–6.04 g/g ww (wet weight). Although the concentration of petroleum hydrocarbons in sediment of the Uppanar region was markedly higher than the background, the petroleum hydrocarbon residues in mollusc collected from Uppanar estuary did not suggest bioaccumulation. The results signified that industrial growth has affected the aquatic environments and regular monitoring will help to adopt stringent pollution control measures for better management of the aquatic region.     

设施菜地土壤重金属累积及影响因素研究

为了解设施菜地土壤重金属累积规律及影响因,通过在全国8个省具有代表性的设施蔬菜产区采集土壤和肥料样品,系统研究了设施栽培年限、肥料施用、土壤性质对设施菜地土壤重金属Cu、Zn、Cd累积量及活度的影响.结果表明:与露天栽培相比,设施条件下随着栽培年限的延长,土壤Cu、Zn和Cd的全量和有效态浓度均呈明显的累积趋势,栽培年限>15a时的设施土壤Cu、Zn和Cd的全量和有效态浓度分别是露天栽培土壤的1.57、2.16、1.67、3.28、1.96、2.00倍.Pearson分析表明设施菜地土壤Cu、Zn、Cd均与土壤SOM呈极显著相关,说明其在来源上较强的相似性,进一步对设施栽培土壤主要投入品中Cu、Zn、Cd含量分析表明,猪粪、商品有机肥及土壤调理剂中Cu、Zn均超过了100mg/kg,Cd超过了1.0mg/kg,且投入量较大,是设施栽培土壤中Cu、Zn、Cd的主要贡献者,而秸秆和部分化肥(如尿素、硫酸钾)中的Cu、Zn、Cd含量均极低,对设施栽培土壤累积贡献微乎其微.pH值和CEC是影响Cu、Zn、Cd在土壤中累积活度的关键因素,其中随着pH值的升高土壤Cu活度表现了先升高后下降的趋势,而土壤Cd活度则表现了持续下降的趋势,仅在pH<6.26时达到了显著相关水平;土壤CEC的升高对土壤Cu活度表现了先下降后升高再下降的趋势,土壤Cd活度表现了先升高后缓慢下降再升高的趋势,而土壤Zn活度仅在CEC<5.83时随着CEC升高表现下降显著线性相关趋势.因此,防止设施栽培土壤Cu、Zn、Cd的累积与污染,选择重金属含量低的肥料和调控土壤理化特性(尤其是pH值、CEC)则是缓解设施栽培土壤重金属累积速率进而确保蔬菜质量安全的有效途径.