Abstract.A good understanding of the interrelations between land cover alteration and changes in hydrologic conditions (e.g., soil moisture) as well as soil physicochemical properties (e.g., fine soil particles and nutrients) is crucial for maintaining the fragile hydrologic and environmental conditions of semiarid land, such as the Horqin Sandy Land in China, but is lacking in existing literature. The objectives of this study were to examine: (1) spatio-temporal variations of soil moisture and physicochemical properties in semiarid land; and (2) how those variations are influenced by land cover alteration. Using the data collected in a 9.71 km 2 well-instrumented area of the Horqin Sandy Land, this study examined by visual examination and statistical analyses the spatio-temporal variations of soil moisture and physicochemical properties. The results indicated that for the study area, the soil moisture and physicochemical properties were dependent on local topography, soil texture, vegetation density, and human activity. Long-term reclamation for agriculture was found to reduce soil moisture by over 23 % and significantly (p-value < 0.05) lower the contents of soil organic matter, fine soil particles, and nutrients.

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Polyhydroxyalkanoates (PHA) terployesters P(3HB-co-3HV-co-3HHx) consisting of 3-hydroxybutyrate (3HB), 3-hydroxyvalerate (3HV), and 3-hydroxyhexanoate (3HHx) were produced by wild-type Aeromonas hydrophila 4AK4, its recombinant harboring PHA synthesis genes phaPCJ encoding PHA binding protein phasin, PHA synthase, and enoyl-CoA hydratase, and another its recombinant harboring phaAB encoding beta-ketothiolase and acetoacetyl-CoA reductase, respectively, when grown in lauric acid and/or valerate. The terpolyesters produced by A. hydrophila 4AK4 (phaAB) grown in velarate were found to produce copolymers P(3HB-co-3HV) containing high 3HV fractions with a maximum of 99 mol% 3HV. In terpolyesters, 3HV ranged from 9 to 32 mol% depending on the valerate concentration and strain used. A maximal terpolyester P(3HB-co-3HV-co-3HHx) content in dry cells was 71 wt%. Transmission electron microscopy study of A. hydrophila 4AK4 harboring phaPCJ revealed the full occupation of terpolyester P(3HB-co-3HV-co-HHx) in the cellular spaces. Terpolyesters with various monomer compositions showed changing thermal and mechanical properties. Those with higher 3HV fractions demonstrated an improved property over the lower HV containing ones.

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Elevated levels of herbicides in surface and groundwater are a concern in the Cornbelt in the USA. This study was conducted to interpret the herbicide behavior in a watershed system using data collected from runoff, Recharge Lake, and groundwater influenced by agriculture and lake seepage. The York Ground Water Recharge Project was constructed on a tributary of Beaver Creek, which drains a 3327‐ha watershed of primarily row‐cropped heavily irrigated farmland. The estimated average runoff is 1.48 × 106 m3 yr−1 under a precipitation norm of 635 mm yr−1. Maximum atrazine (2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine) inputs to Recharge Lake occurred in May and June runoff events and resulted in average lake concentrations of 36 and 17 µg L−1 in 1993 and 1994, respectively. Only about 0.28 and 0.19% of total applied atrazine was lost to runoff in 1993 and 1994, respectively. The deethylatrazine (DEA) to atrazine molar ratio (DAR) decreased rapidly over a period of several hours in runoff samples, which is consistent with inputs from recently atrazine‐treated soil. After the spring runoff, herbicide levels in Recharge Lake rose rapidly in response to the runoff event, then diminished gradually over a period of months. Atrazine concentrations in Recharge Lake decreased exponentially with time. Degradation half‐lives were 237 d (r = 0.93) in 1993 and 209 d (r = 0.91) in 1994. Adjusted DEA concentrations in Recharge Lake remained relatively constant, indicating little evidence for biotic degradation and suggesting that abiotic degradation of atrazine to hydroxyatrazine (2‐hydroxy‐4‐ethylamino‐6‐isopropylamino‐s‐triazine) was the most likely major degradative pathway in Recharge Lake.

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