中国转型期水环境治理中的政府责任研究

水环境问题已成为制约我国长期可持续发展的主要瓶颈.如何有效治理水环境问题已引起全社会的普遍关注.本文在全面分析水环境公共物品属性以及水环境问题的客观现实的基础上,论证了政府承担治理水环境责任的必要性.进而对现阶段政府承担的水环境治理责任进行研究,归纳出其环境治理责任主要有财政责任、制度责任、监管责任和社会整合责任.然后对水环境治理中政府责任存在的现实问题进行深入分析,揭示其问题主要表现为:责任主体边界模糊、责任分布以“行政”为主导、责任履行中“越位”与“缺位”并存、责任种类中重直接投入轻间接引导.最后,提出水环境治理中的政府责任应该在坚持财权与事权统一、政府主导与责任分担统一、制度设计、监管与实施合理分离、政府引导与社会参与相结合的原则基础上,按照分类、分项、分级来构建转型期水环境治理中政府的应然责任框架体系.     

三峡库区汛期极端降水非均匀性特征

利用极端降水量集中度和集中期讨论三峡库区汛期极端降水量的非均匀性分布特征。结果表明: 三峡库区极端降水量空间分布表现为西南部和东北部地区相对较少,中部、东南部相对较多。库区汛期极端降水集中度和集中期的空间差异不大,集中程度总体较差,东北部和西部地区极端降水相对集中,中部相对分散。库区极端降水主要集中在6月底和7月上中旬,东北部和西部偏西地区集中期相对较晚,中部地区集中期相对较早。库区汛期极端降水量的分配状况与同期极端降水量存在较好的关系,即极端降水量越少,则极端降水量越集中、集中期越早;反之极端降水量越多,则极端降水量越分散、集中期越晚,尤其是在库区东北部地区最为显著。三峡库区蓄水后极端降水集中程度在空间上一致性较好,表现为蓄水后更为分散;极端降水量和集中期则在空间上差异显著,大致表现为蓄水后东北部极端降水增加并延迟;西南部极端降水减少并提前     

三峡工程蓄水运用期库区干流水质分析

分析了三峡库区蓄水前后（1998～2009年）干流水质的变化及原因。结果表明,同蓄水前相比,蓄水后库区干流水质变好,库区干流断面月度达标率均值由蓄水前的623%变为蓄水后的783%,库区干流超标污染物主要为高锰酸盐指数、总磷、铅等。蓄水后水质时空分布出现新的特点,近坝水体悬浮物、浑样高锰酸盐指数、总磷、铅等可吸附污染物浓度显著降低。蓄水后年内悬浮物及浑样高锰酸盐指数、总磷和铅浓度仍然是丰水期＞平、枯水期,但近坝水体不同水期间浓度差别比蓄水前明显减小。蓄水后,库区干流浑样高锰酸盐指数、总磷、铅浓度整体上表现为从库尾至库首沿程下降,尤以丰水期沿程下降最为突出。浑样高锰酸盐指数、总磷、铅浓度以上变化特征主要缘于库区水位抬高后,流速减小导致的澄清作用,即高锰酸盐指数所代表污染物、磷、铅等随泥沙发生了不同程度的沉降。蓄水前后清样高锰酸盐指数和总磷未发生明显变化,156 m蓄水后至今,清样铅浓度明显低于蓄水前。     

洪湖历史时期人类活动的湖泊沉积环境响应

以洪湖北部和南部两个短柱钻孔(HN和HS)研究湖泊沉积,采用137Cs定年,沉积速率为0.155 cm/a。沉积物的总有机碳、总氮、磷以及元素和磁化率等指标分析表明：1840年前洪湖地区人类活动较弱,在湖泊沉积物中基本没有早期的人类活动信号的记录;1840年以后由于人口大量增加,人类活动增强,湖泊的营养水平有所增加,尤其是1950年以来沉积物中营养元素急剧增加;近50年来的湖泊营养程度的加重主要与流域内大量营养物质进入湖泊,以及大面积的围垦造成湖泊面积减小、自我调节能力降低有关。洪湖两孔的对比研究表明,不同区域之间存在着差异,可能与洪湖湖流作用及人类活动的影响差异有关。     

丰水期鄱阳湖氮磷含量变化及来源分析

通过系统测定丰水期鄱阳湖湖水、主要支流水、长江水及部分农田水、地下水及城市污水的氮磷含量,对其氮磷含量变化及来源进行了分析,结果表明,鄱阳湖水体中主要的氮素形式是硝酸盐氮（090 mg/L）,赣江是其主要贡献者。鄱阳湖五大支流氮磷含量存在着较大的差异,赣江NO-3 N含量明显高于鄱阳湖其它主干流,而NH+4 N和TN含量以饶河的最高,TP以信江的最高。农田水、城市废水以及地下水含有较高的氮磷含量,是鄱阳湖及其五大支流氮磷的主要来源。农田水TN和TP含量最高,分别为1347、2863 mg/L。高含量的NO-3 N（735 mg/L）和NH+4 N（548 mg/L）分别出现在地下水和城市污水中。鄱阳湖水体氮负荷较大,N/P比值远大于7〖DK〗∶1。受滞留区及赣江和修水补给的影响,鄱阳湖主河道氮含量变化从上游至下游呈总体上升趋势。鄱阳湖湖体氮含量以下游最高,滞留区次之,上游主河道最低,TP含量呈相反的趋势变化。底层沉积有机物的降解和扰动导致鄱阳湖水体底层NO-3 N、NH+4 N、TN、TP的含量高于表层。     

一种新的汛期降水集中期划分方法

汛期降水集中期是近期气象学者提出的表征汛期气候的一种新的特征量,它在气候研究中体现了较好的灵活性、客观性,通过对其分析,可为汛期气候的诊断和预测提供依据。但现在普遍使用的降水集中期在计算方法和时间长度上存在缺陷,特别是运用到时间跨度较长时段的气候分析时,特征量表征作用就有所缺失,而且计算方法较为复杂。为更好地使用降水集中期这一特征量,提出了以15天作为时长,用滑动统计来划定汛期降水集中期的新方法,并运用统计方法、天气气候学方法进行了论证,同时在长江下游主雨季降水集中期分析和金华地区汛期分析两个实例中进行了应用检验。结果表明,汛期降水集中期新方法划定的特征量与汛期降水总量存在时间上的相对独立性和总趋势上的显著相关性,且在汛期气候极端灾害事件上有较强的描述能力。因此认为,15天滑动统计新方法划定的汛期降水集中期使用便捷,天气气候意义明确,在实际应用中更为客观有效。     

基于轮廓似然函数的PM_(10)极值浓度分析

以R软件为分析工具,选择GEV(generalized extreme value distribution)模型拟合四川省泸州市2003～2007年期间PM10每月最高日平均浓度数据,采用极大似然法估计模型的3个参数即位置参数、尺度参数、形状参数,利用所得的参数估计值计算得出某一标准值(如GB3095—1996)的重现期;进一步利用参数估计值计算轮廓似然函数,估计某一段固定时间间隔的PM10浓度的重现值以及其置信区间。结果表明,GEV模型能很好地拟合泸州市PM10数据,利用轮廓似然函数估计的不同时间间隔的重现值准确度高,统计结果可以为环境主管部门发布污染状况预警信息提供参考。     

Critical considerations for future action during the second commitment period: A small islands' perspective

If the objective of the United Nations Framework Convention on Climate Change (UNFCCC) is to be achieved, Parties must commit themselves to meeting meaningful long‐term targets that, based on current knowledge, would minimize the possibility of irreversible climate change. Current indications are that a global mean temperature rise in excess of 2–3 °C would enhance the risk of destabilizing the climate system as we know it, and possibly lead to catastrophic change such as a shutdown of the deep ocean circulation, and the disintegration of the West Arctic Ice Sheet. Observations have shown that for many small island developing States (SIDS), life‐sustaining ecosystems such as coral reefs, already living near the limit of thermal tolerance, are highly climate‐sensitive, and can suffer severe damage from exposure to sea temperatures as low as 1 °C above the seasonal maximum. Other natural systems (e.g., mangroves) are similarly susceptible to relatively low temperature increases, coupled with small increments of sea level rise. Economic and social sectors, including agriculture and human health, face similar challenges from the likely impacts of projected climate change. In light of known thresholds, this paper presents the view that SIDS should seek support for a temperature cap not exceeding 1.5–2.0 °C above the pre‐industrial mean. It is argued that a less stringent post‐Kyoto target would frustrate achievement of the UNFCCC objective. The view is expressed that all countries which emit significant amounts of greenhouse gases should commit to binding reduction targets in the second commitment period, but that targets for developing countries should be less stringent than those agreed for developed countries. Such an arrangement would be faithful to the principles of equity and would ensure that the right of Parties to attain developed country status would not be abrogated.     

The effect of greenhouse vegetation coverage and area on the performance of an earth-to-air heat exchanger for heating and cooling modes

The underground temperature at a depth of about 3–4 m is almost constant all the year round. In summer, the underground temperature is lower than the ambient temperature, but in winter it is vice versa. This potentiality is considered for greenhouse cooling and heating by using an earth-to-air heat exchanger (EAHE). This paper considers the effects of two parameters as independent variables including the area of greenhouse and the percentage of vegetation coverage inside the greenhouse on the performance of an EAHE system during both cooling and heating modes. The inside temperature, the thermal energy exchange and the coefficient of performance (COP) of the system were considered as dependent variables. The results showed that both greenhouse area and the percentage of vegetation coverage inside the greenhouse had significant effects on the performance of the EAHE system during both cooling and heating modes. However, the COP of the EAHE system was higher in the cooling mode (4.32) than during the heating mode (1.01). The percentage of vegetation coverage negatively affected the performance of the EAHE system in the cooling mode. However, the performance of the EAHE system improved with the increase in the percentage of vegetation coverage during the heating mode.     

Mitigation of methane and nitrous oxide emissions from drained irrigated rice fields

One of the important cultural practices that affect methane and nitrous oxide emissions from tropical rice plantations is the water drainage system. While drainage can reduce methane emissions, it can also increase nitrous oxide emissions, as well as reduce yields. In this experiment, four different water drainage systems were compared in a rice field in central Thailand including: (1) continuous flooding, (2) mid-season drainage, (3) multiple drainage and (4) a local method (drainage was done according to local cultural practice) in order to find a system of drainage that would optimize yields while simultaneously limiting methane and nitrous oxide emissions. Methane and nitrous oxide emission were observed and compared with rice yield and physical changes of rice plants. It was found that drainage during the flowering period could reduce methane emission. Interestingly, nitrous oxide emission was related to number of drain days rather than the frequency of draining. Fewer drain days can help reduce nitrous oxide emission. The mid-season drainage and the multiple drainage, with 6.9% and 11.4% reduction in rice yield, respectively, had an average methane emission per crop 27% and 35% lower when compared to the local method. Draining with fewer drain days during the flowering period was recommended as a compromise between emissions and yield. The field drainage can be used as an option to reduce methane and nitrous oxide emissions from rice fields with acceptable yield reduction. Mid-season drainage during the rice flowering period, with a shortened drainage period (3 days), is suggested as a compromise between the need to reduce global warming and current socio-economic realities.